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Home My WebLink AboutB110093 1• 611 VC01 3 STORMWATER TECHNICAL INFORMATION Boeing Buyer Furnished Equipment (BFE) Expansion Building 4-68 Renton, Washington A FSsroN A June 15, 201 1 RETCEIVED JUN 2 2 2011 sUILDING (VISION ■ MAGNUSSON KLEMENCIC ASSOCIATES /�,�,� k. �l e��-r�--+- 2� � �r� — Z�� ,. CITY OF RENTON Plan Review Comments Permit Number: B 110093 #4-68 BLDG. -BFE WAREHOUSE Item 1: ENERGY COMMENTS: JAN CONKLIN 425-430-7276 1. SLAB INSULATION DETAIL INCORRECT. INSULATION TO BE INSTALLED FROM TOP OF SLAB DOWN TO BOTTOM OF FOOTING.FOR YOUR MONOLITHIC POURS THAT MEANS ON THE EXTERIOR OF THE FOOTING.ANY INSULATION EXPOSED TO THE ELEMENTS SHALL BE PROTECTED FROM EXPOSURE. DLR Group Response: Per our conversation 6/17/11, we have recalculated the Washington State Energy Code Compliance forms, and we are in compliance without foundation insulation for the west wall. Reference the attached Envelope Summary dated 6/20/2011. Note: for the north and south foundation walls, we have added the insulation to the exterior of the wall; reference sheets A200 and A201 attached. 2.PROVIDE WINDOW AND DOOR U-VALUES ON THE PLANS -SHEET A350. DLR Group Response: We have added this information instead to Drawing G4,CODE ANALYSIS,under"Thermal Resistance Requirements. 3.PROVIDE ROOF INSULATION R-VALUES ON THE PLANS.ALSO INCLUDE R-VALUES TO BE INSTALLED IN CANTILEVERED AREAS. DLR Group Response: As with Item 2 above, Roof insulation information is located on Drawing G4,CODE ANALYSIS,under"Thermal Resistance Requirements; we have added the cantilever requirements here. 4. YOU HAVE STATED ON THE PLANS AND ON THE ENERGY CODE CHECKLIST THAT YOU ARE DOING PRESCRIPTIVE COMPLIANCE-YET YOU PROVIDED COMPONENT PERFORMANCE CALCS AND THE U-VALUE OF YOUR DOORS ON THESE CALCS WOULD KEEP YOU FROM USING PRESCRIPTIVE APPROACH. VERIFY AND REVISE AS NECESSARY. DLR Group response: the"prescriptive"box was mistakenly checked instead of the"component performance"box.We have revised the form,dated 6/20/2011 as indicated in Item 1 response above, and attached herewith. 5. PLEASE PROVIDE THE LTG-EXT AND THE LTG-CHK PAGES OF THE ENERGY CODE CHECKLIST. DLR Group response: Checklist has been updated(dated 6/22/2011)to include all of the above information. 6. I SEE LOTS OF OCCUPANCY SENSORS AND AN ENERGY MANAGEMENT SYSTEM ON THE PLANS. ARE THERE AUTOMATIC CONTROLS TO TURN OFF THE LIGHTS THAT ARE INSTALLED ON CUBICLE FURNITURE? E IgCE VE D DLR Group response: The systems furniture is not part of the contract for constructiogUWe- Ill'Idlett Boeing of the new requirement mandating that task lights for cubicles must now include occupancy sensors. BUILDING DIVISION 2: PLAN REVIEW: JAN ILLIAN 425-430-7216 TIR STORM COMMENTS: DLR Group response: reference responses in separate letter,dated June 10, 2011,from Matthew Jones, Civil Engineer, Magnusson Klemencic Associates,included herewith; included also is a revised stormwater report. 1.Filterra®is not an approved treatment facility in the City's Amendments to t the 2009 KCSWDM. However,it has been given a general use designation for enhanced water quality treatment by Ecology through their Technology Assessment Protocol(TAPE) program. The City will consider any treatment facility that has been given a general use designation provided it is approved through the City's adjustment process. To be approved,the applicant will need to provide a written request to the Renton Development Services Division that shows the proposed water quality treatment facility will meet the following: " Produces a compensating or comparable result that is in the public interest " Meets the objectives of safety, function, appearance,environmental protection, and maintainability based on sound engineering judgment. Further information on the adjustment processes can be found in Section 1.4 of the City amendments document. 2. In accordance with the Department of Ecology's general use level designation requirements,the water quality volume sizing for the Filterra® is based on a volume equal to or greater than the 91 percent of the influent runoff file using DOE's Western Washington Hydrologic Model.However,the third paragraph in Section 4 of the drainage report, states that the water quality volume will be based on 60% of the 2-yr peak flow rate as determined using the KCRTS model with 15 min time steps per Section 6.2.1 of the City of Renton Amendments to the King County Surface Water Design Manual .The TIR will need to be corrected to show that the proposed treatment facility will be designed using the criteria in Ecology's General Use Level Designation for Filterra®. 3. Per Ecology's conditions of use for Filterra®,the sizing for enhanced treatment should be based on a filter hydraulic conductivity of 24.82 inches/hour.The WWHM summary sheet in the TIR shows an input value of 24.5 inches/hour.Applicant will need to explain the discrepancy. 4. Based on Table IV-1 on page 2 of the TIR,the project is required to treat 25,754 SF of replaced pollution generating impervious surface(PGIS). To provide enhanced treatment for this area,the project proposes to treat 19,063 SF of the replaced PGIS,4,807 SF of existing PGIS not currently being treated and 2,318 SF of non-pollution generating impervious surface. In accordance with Core Requirement No. 8, treating existing PGIS that is not currently being treated to compensate for targeted PGIS that cannot be treated is acceptable provided the existing area being treated has the same pollutant loading characteristics as the targeted PGIS. Since the 2,318 SF being treated is from a non-pollution generating impervious surface, it cannot be considered as providing mitigation.The applicant must either treat additional replaced PGIS or existing PGIS with the same pollutant loading characteristics. 5. Figure I-3F does not appear to delineate replaced PGIS being treated; it only shows the existing PGIS being treated. 6. Include in the TIR, a copy of the Ecology's product design document that defines the requirements for the use of Filterra® as an enhanced water quality treatment facility. 7. Include the WWHM output files for the Filterra®as a separate appendix in the report. Include in the appendix drawing detail and cover letter that shows the design was reviewed and approved by Filterra®. 8. The TIR does not address the requirement for Flow Control BMPs. Per Core Requirement No. 3, all projects, including redevelopment projects must provide onsite flow control facilities or flow control BMPs or both to all targeted surfaces. The applicant will need to review Chapter 5 of the 2009 King County Surface Water Design Manual to determine if flow control BMPs are required. 3 ' 9.The design plans use construction notes to identify existing and proposed utilities.This method makes it difficult to review the plans and does not conform to the standards for site improvement plans in Section 2.3.1.2 of the 2009 KCSWDM.Existing storm drainage facilities are to be represented with dashed lines and labeled as "Existing". New drainage pipes should have the length,diameter and material identified next to the pipe. 10. Plans should include profiles of proposed storm pipes. Please address each comment in writng. Please submit 1 copy of the revised TIR and 1 jset of revised drawings. 3: STRUCTURAL REVIEW: SEE ATTACHED LETTER FROM REID MIDDLETON. DLR Group response: Reference responses in separate letter,dated June 21, 2011,from Pat Ryan, Structural Engineer, Magnusson Klemencic Associates,included herewith; included also are revised portions of the structural calculations, and revised drawing sheets: 1S-1-13, 1S-1-14, 15-1-15, 15-2-13, 1S-2-14, 1S-2-15,MIS-3-15, S1, S2A, S2B, S212, S407, S408, S409, S524 and 5525. STORMWATER TECHNICAL INFORMATION Boeing Buyer Furnished Equipment (BFE) Expansion Building 4-68 Renton, Washington June 15, 2011 ■ MAGNUSSON KLEMENCIC ASSOCIATES Structural - Civil Engineers 1301 Fifth Avenue,Suite 3200 Seattle,Washington 98101-2699 T:206 292 1200 F:206 292 1201 MAGNUSSON KLEMENCIC STORMWATER TECHNICAL INFORMATION Section I: Project Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Section II: Conditions and Requirements Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Section III: Offsite Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Section IV: Flow Control and Water Quality Facility Analysis and Design . . . . . . . . . . . . . . . . . . 9 Section V: Conveyance System Analysis and Design. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 Section VI: Special Reports and Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 Section VII: Other Permits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 Section VIII: Construction Stormwater Pollution Prevention Plan Analysis and Design . . . . . . . . 1 1 Section IX: Bond Quantities Worksheet, Retention/Detention Facility Summary Sheet, and Declaration of Covenant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 Section X: Operations and Maintenance Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 3 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 FIGURES Figure 1-1: Technical Information Report Worksheet Figure 1-2: Site Location A. Vicinity Map B. Renton Facility Map C. Flood Hazard Area D. Liquefaction Hazard Area Figure 1-3: Drainage Basins and Site Characteristics A. Overall Drainage Basins and Downstream Discharge B. Existing Drainage System C. Site Sub-Basins D. Existing Site Conditions E. Proposed Site Conditions F. Proposed Drainage System Figure 1-4: Soils Map Figure II-1: 2-year, 24-hour Precipitation Figure II-2: 25-year, 24-hour Precipitation Figure II-3: 100-year, 24-hour Precipitation Figure V-1: Flow Diagram Stormwater Technical Information Table of Contents Boeing Buyer Furnished Equipment (BFE) Expansion, Building 4-68, Renton, Washington MAGNUSSON KLEMENCIC !A`r ■ APPENDICES Appendix A: Stormwater Calculations Appendix B: Americast Filterra Documentation Appendix C: Soils Report Appendix D: Stormwater Pollution Prevention Plan Appendix E: Temporary Erosion and Sedimentation Control Plans Appendix F: Grading and Utility Plans Stormwater Technical Information Table of Contents Boeing Buyer Furnished Equipment (BFE) Expansion, Building 4-68, Renton, Washington MAGNUSSON KLEMENC[C ASSOCIATES ■ SECTION i• PROJECT OVERVIEW INTRODUCTION This report documents the stormwater and drainage design approach for the proposed Building 4-68 Boeing Buyer Furnished Equipment (BFE) project. The report has been prepared using the guidelines for the Stormwater Technical Information Report (TIR) from the City of Renton Amendments to the 2009 King County Surface Water Design Manual (KCSWDM) dated February 2010. Figure I-1 consists of the standard TIR worksheet, completed for the project. The project is located within the Boeing-Renton Facility in Renton, Washington, just south of the southern tip of Lake Washington and just east of the lower reach of the Cedar River (see Figure I-2A). The site resides in Section 7, Range 5 East, Township 23 North, and is within the block bounded by North Sixth Street and Nishiwaki Lane. It is located in the Lower Cedar River Basin. Boeing's Renton Facility occupies roughly 278 acres of property and houses nearly 4.3 million square- feet of building space. This project proposes a new approximately 76,000-square-foot warehouse building (4-68 BFE) adjacent to the existing 4-75 building that will become the new home for avionics and seat assemblage amongst other functions (see Figure 1-213). The east face of the new BFE building will abut the west face of the existing 4-75 building. In the northwest corner of the new BFE building, two loading docks will be constructed and the existing parking lot will be modified to accommodate truck staging as well as loading and unloading. The existing covered pedestrian walkway will be bisected due to construction of the new BFE building, which will force pedestrian circulation to the west. The north and south sides of the new BFE building will tie into the existing roads that run east-west. Figure 1-213 shows the project site and limits of work for the proposed improvements. EXISTING CONDITIONS The entirety of the Boeing Renton Facility is developed, and current land use consists of paved parking areas, industrial warehouses, roads, and covered pedestrian walkways. The project is located roughly 100 feet outside of the 100-year flood plain of the lower Cedar River and is prone to high liquefaction, as seen on Figures 1-2C and I-2D. The existing site is currently occupied by the 4-75 building, covered walkways, cement concrete pavement, curbs, an asphalt concrete drive lane, and parking are also present on site. As stated previously, the site is located in the Lower Cedar River basin. There are two sub-basins that divide the site, as delineated by the Boeing-Renton Facility Drainage Basin Boundaries Map: - Sub-basin 32 to the north and Sub-basin 34 to the south (see Figures I-3A and 1-313). North Basin (32) Runoff from paved areas in the North Basin is currently routed through an oil/water separator (ROWS- 43; see Figure 1-36). This basin also collects half of the existing 4-75 building roof area which is routed to the drainage system downstream of the oil/water separator. All the storm water leaves the site to the west, and is then routed roughly 2,400 feet to the north by means of a 54-inch reinforced concrete pipe that upsizes to a 60-inch before draining directly into lake Washington. Stormwater Technical Information Boeing Buyer Furnished Equipment (BFE) Expansion, Building 4-68, Renton, Washington MAGNUSSON KLEMENCIC ASSOCIATES ■ South Basin (34) Runoff from the paved areas to the west and south of the existing building currently drain to the south where they are routed through one of two oil/water separators (ROWS-49 and ROWS-50; see Figure 1-36). The storm water drains into catch basins, as in Sub-basin 32, and is then conveyed to the west. It is then routed to the north and connects to the same storm drainage system as Sub-basin 32, eventually discharging into Lake Washington. The table below summarizes the existing surface conditions within the project limits delineated on Figure I-3D. Table 1-1: Existing Surface Conditions within Boeing BFE Building Project Limits Surface Area Surface Area Ground Surface ` (sf) (acres) Roof— Impervious 2,972 0.07 Pollution-Generating Impervious Surface 108,744 2.50 Landscape— Pervious 863 0.02 Total 112,576 2.59 PROPOSED DRAINAGE The project does not propose to change any discharge locations from the sub-basins or their final discharge to Lake Washington. All new storm drainage infrastructure will be installed to capture new roof and pavement runoff and will convey it to existing structures and outfalls. Due to the fact that Lake Washington is the receiving body for runoff from the site and meets the direct discharge criteria, storm water detention is neither required nor proposed. Water quality treatment is proposed via Americast's Filterra System as a means to provide enhanced water quality treatment for the pollution-generating impervious surfaces (PGIS). The tables below summarize the surface conditions within the projects limits of work as delineated on Figure I-3E and Figure 1-3F. Stormwater Technical Information Boeing Buyer Furnished Equipment (BFE) Expansion, Building 4-68, Renton, Washington MAGNUSSON KLEMENCIC nsSOC'A FS Table 1-2: Proposed Surface Conditions within Boeing BFE Building Project Limits Surface Area Surface Area Ground Surface Type (sf) (acres) Roof— Impervious 75,756 1 .74 Pollution-Generating Impervious Surface 22,924 0.53 Non-Pollution-Generating Impervious Surfaces 4,474 0.10 Landscape — Pervious 9,421 0.22 Total 112,576 2.59 Table 1-3: Basin Area Breakdown within Boeing BFE Building Project Limits Surface Description PGIS Non PGIS Pervious PGIS Non PGIS Pervious Existing 35,304 11155 420 74,436 1,817 443 1 12,576 Proposed 475 2,243 1,358 22,449 77,987 8,063 112,576 Stormwater Technical Information Boeing Buyer Furnished Equipment (BFE) Expansion, Building 4-68, Renton, Washington MAGNUSSON KLEMENCIC a�S(D-: rFS u Table 1-4: Proposed Basin Area Breakdown Area Being Exist/Replaced Treated for Basin Total Basin Replaced PGIS Existing PGIS Non-PGIS Water Area (impervious) (impervious) (impervious) Pervious Quality A 15,480 11,724 2,795 423 538 14,519 B 10,707 6,767 2,450 565 925 9,217 C 8,326 719 5,812 482 1,313 0 D 2,566 0 0 0 2,566 0 South E 2,697 2,512 0 185 0 0 Basin F-A 10,394 0 0 10,394 0 0 (34) F-B 8,332 0 0 8,332 0 0 F-C 1,623 0 0 1,623 0 0 F-D 51,673 0 0 51,673 0 0 G 18,492 0 0 18,492 0 0 H 9,756 186 6,915 1,406 1,249 0 1 5,560 541 4,251 678 90 0 J 3,040 0 1,501 156 1,383 0 Total 148,645 22,449 23,724 94,409 8,064 23,736 Area Being Exist/Replaced Treated for Basin Total Basin Replaced PGIS Exist PGIS Non-PGIS Water Name Area (impervious) (impervious) (impervious) Pervious Quality North K 4,256 66 3,897 0 293 0 Basin (32) L 2,349 324 1,352 0 673 0 M 7,414 85 6,721 215 393 0 N 18,478 0 0 18,478 0 0 Total 32,497 475 11,970 18,693 1,359 0 Stormwater Technical Information Boeing Buyer Furnished Equipment (BFE) Expansion, Building 4-68, Renton, Washington MAGNUSSON KLEMENCIC ASSOCIATES ■ SOILS The Boeing Renton Facility sits on the sedimentation fan created by the Cedar River outfall to Lake Washington. The soils are comprised of loose and unconsolidated alluvial sediments, as seen on the soil map in Figure 1-4 (prepared by the Soil Conservation Service [SCS] in the 1970s). The Geotechnical Report produced by Soil and Environmental Engineers, Inc., dated March 25, 2011, is included in this report in Appendix C, in which they note the following: "The native soils in the area consist of loose and unconsolidated alluvial sediments extending to 100 feet or more in depth. During WWII, the plant area was leveled by about 2 to 5 feet thick of fill. The native soils immediately under the fill include soft and compressible silt and loose sand. Groundwater level is typically about 4 to 6 feet below the ground surface ... [T]he majority of Renton area has been modified by past grading activities. Cedar River has meandered through various portions of the city since last glaciations and deposited alluvial soils. The upper portion of these soils is typically soft and unconsolidated." LIST OF FIGURES ■ Figure I-1 : TIR Worksheet ■ Figure 1-2: Site Location A. Vicinity Map B. Renton Facility Map C. Flood Hazard Area D. Liquefaction Hazard Area ■ Figure 1-3: Drainage Basins and Site Characteristics A. Overall Drainage Basins and Downstream Discharge B. Existing Drainage System C. Site Sub-Basins D. Existing Site Conditions E. Proposed Site Conditions F. Proposed Drainage System ■ Figure 1-4: Soils Map Stormwater Technical Information Boeing Buyer Furnished Equipment (BFE) Expansion, Building 4-68, Renton, Washington MAGNUSSON KLEMENCIC ASSOCIATES ■ SECTION II• CONDITIONS AND REQUIREMENTS SUMMARY SITE CON DITIONS/THRESHOLDS This project is considered a redevelopment project. The total project area encompasses 2.59 acres. The project will yield approximately 1.74 acres of building roof, 0.53 acres of replaced pavement, 0.10 acres of sidewalk, and roughly 0.22 acres of landscape areas. Approximate 1 .84 acres of existing pollution-generating surfaces will be replaced with non-pollution-generating rooftop surface and sidewalk. RAINFALL Design storms for the project are shown in Table II-1 and Figures II-1 to II-3. Table II-1: 24-hour Precipitation at Boeing BFE Building Rainfall Storm Recurrence (inches) 2-year 1.95 10-year 2.89 25-year 3.38 100-year 3.90 CORE REQUIREMENTS Stormwater detention is not required due to the fact that the site discharges directly to Lake Washington, an exempt water body, and meets all of the direct discharge criteria. Water quality, however, is required due to the project's removal and replacement of more than 5,000 square feet of pollution-generating impervious surfaces. The drainage design will accommodate the roof drainage off of the west side of the existing 4-75 building as well as the proposed BFE building and associated loading docks. Listed below are the core requirements as described in the City of Renton Amendments to the 2009 KCSWDM dated February 2010. Core Requirement 1: Discharge at the Natural Location The proposed storm drainage system will mimic the existing drainage sub-basins and tie into the existing storm drain system, thus discharging at the natural location. Stormwater Technical Information Boeing Buyer Furnished Equipment (BFE) Expansion, Building 4-68, Renton, Washington MAGNUSSON KLEMENCIC ASSOCIATES ■ Core Requirement 2: Offsite Analysis The project is exempt per Exemption #3, which states, "The project does not change the rate, volume, duration, or location of discharges to and from the project site (e.g., where the existing impervious surface is replaced with other impervious surface having similar runoff-generating characteristics)." Core Requirement 3: Flow Control The project will obtain a direct discharge exemption since the site discharges to Lake Washington and meets the following criteria: a) The flowpath from the project site discharge point to the edge of the 100-year floodplain of the major receiving water will be no longer than one-half mile, except for discharges to Lake Washington, and b) The conveyance system between the project site and the major receiving water will extend to the ordinary high water mark, and will be comprised of manmade conveyance elements (pipes, ditches, etc.) and will be within public right-of-way or a public or private drainage easement, and c) The conveyance system will have adequate capacity to convey the 25-year peak flow (per Core Requirement #4, Conveyance System) for the entire contributing drainage area, assuming build-out conditions to current zoning for the equivalent area portion (defined in Figure I.2.3.A, below) and existing conditions for the remaining area, and d) The conveyance system will be adequately stabilized to prevent erosion, assuming the same basin conditions as assumed in Criteria (c) above, and e) The direct discharge proposal will not divert flows from or increase flows to an existing wetland or stream sufficient to cause a significant adverse impact. Core Requirement 4: Conveyance System The proposed storm drain system will be designed to convey the 100-year storm event. Storm drainage infrastructure will be installed that extends along both the north and south sides of the proposed BFE building as well as trench drains and a storm drain manhole within the proposed loading docks. All storm drain piping will consist of Lined Corrugated Polyethylene Pipe where cover over the top of pipe is 2 feet or more. Ductile Iron pipe will be used in areas where the cover over the top of pipe is less than 2 feet. Core Requirement 5: Temporary Erosion and Sedimentation Control Temporary Erosion and Sedimentation Control (TESC) Plans have been prepared for this project and are included in this report as Appendix E. Stormwater Technical Information Boeing Buyer Furnished Equipment (BFE) Expansion, Building 4-68, Renton, Washington MAGNUSSON KLEMENCIC ASSOCIATES ■ Core Requirement 6: Maintenance and Operation Maintenance and operation requirements have been identified based on the stormwater management and storm drain system design. The Boeing Company is responsible for maintaining the proposed facilities in accordance with applicable manufacturer's recommendations, the 2009 KCSWDM, and the City of Renton Amendments to the 2009 KCSWDM adopted in February 2010. Core Requirement 1: Financial Guarantees and Liability Does not apply. Core Requirement 8: Water Quality Enhanced water quality treatment will be required as the project will remove and replace more than 5,000 square feet of pollution-generating impervious surfaces and a concern exists about metals such as Copper and Zinc. To accomplish this, two Americast Filterra Internal Bypass units with high flow bypass systems will be installed. These units will be installed behind the existing curb in two of the sump conditions on the west side of the site. Solid locking lids will be installed on the existing catch basins in order to direct the flows into the Filterra units. See Section IV for more information. SPECIAL REQUIREMENTS The City of Renton Amendments to the 2009 KCSWDM adopted in February 2010 is used as the basis for storm water design of this site. Below are additional special requirements that are specified in the KCSWDM. Special Requirement 1: Other Adopted Area-specific Requirements All other adopted requirements do not apply. Special Requirement 2: Flood Hazard Area Delineation This requirement does not apply since the site is not located in a floodplain. Special Requirement 3: Flood Protection Facilities Does not apply. Special Requirement 4: Source Controls The proposed project will comply with this requirement. Please refer to the Stormwater Pollution Prevention Plan (SWPPP), included as Appendix D, for source control information. Special Requirement 5: Oil Control This requirement does not apply since this project will not create a high-use site. That said, the site currently routes all pollution-generating surfaces through three existing oil-water separators (ROWS-043 Stormwater Technical Information Boeing Buyer Furnished Equipment (BFE) Expansion, Building 4-68, Renton, Washington MAGN USSON KLEMENCIC ASSOCIATES ■ in the north basin and ROWS-49 and ROWS-50 in the south basin) that will remain in use during and after construction. Refer to Figure 1-313 for details. Special Requirement 6: Aquifer Protection Area This requirement does not apply since the project is not location in an Aquifer Protection Area (APA). LIST OF FIGURES ■ Figure II-1 : 2-year, 24-hour Precipitation ■ Figure II-2: 25-year, 24-hour Precipitation ■ Figure II-3: 100-year, 24-hour Precipitation SECTION III: OFFSIIE ANALYSIS A quantitative downstream analysis is not required for this project since it does not change the rate, volume, duration, or location of discharges to and from the project site (e.g., where existing impervious surface is replaced with other impervious surface having similar runoff-generating characteristics, or where pipe/ditch modifications do not change existing discharge characteristics). STUDY AREA DEFINITION AND MAPS The project site is located in the Lower Cedar River watershed at the southern end of Lake Washington. A quantitative downstream analysis is not required for this project for the reasons stated above. Please refer to Figures 1-2 for the site location and characteristics. SECTION IV: FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN FLOW CONTROL This project is exempt from flow control (Core Requirement #3), due to a direct discharge exemption, as previously stated in Section II of this report. FLOW CONTROL BMPs This project will implement the large lot high impervious Best Management Practice (BMP) requirements for flow control as outlined in Section 5.2.1 .3 of the KCSWDM. ■ Full dispersion is not feasible for this site since no forest area is available within the threshold discharge area to meet the 15 percent ratio of fully dispersed impervious area to native vegetated surface. ■ Since the subject site will result in impervious surface coverage greater than 65 percent (approximately 92 percent), flow control BMPS must be applied to an impervious area equal to at Stormwater Technical Information Boeing Buyer Furnished Equipment (BFE) Expansion, Building 4-68, Renton, Washington MAGNUSSON KLEMENCIC ASSOCIATES ■ least 10 percent of the site area (10% * 112,576 sf = 1 1,258 sf) or 20 percent of the target impervious surface (20% * 0 sf = 0 sf). With respect to BMPs, the proposed Americast Filterra units are comparable to rain gardens, an acceptable flow control BMP as described in Section 5.2.1.3 in the KCSWDM, and are sized to treat 23,726 square feet, which equates to roughly 21 percent of the site area. ■ It is not practical to use perforated pipe connections for the roof downspouts due to the presence of high ground water and poor soils with negligible infiltration capacity. Refer to the soils report in Appendix C. WATER QUALITY TREATMENT Water Quality will be provided for pollution-generating surfaces in the south basin, which primarily occur in Basins A and B (see Figure 1-3F). Water will surface flow to two Americast Filterra Internal Bypass units. Table IV-1 below describes the areas that will be treated for water quality: Table IV-]: Water Quality Treatment Areas within Basin Boundaries Treatment,. North Pnsin South Basin Total Total Area Treated for Water Quality 0 23,736 23,736 Replaced PGIS Treated for Water Quality 0 18,491 18,491 Existing PGIS Treated for Water Quality 0 5,245 5,245 Replaced PGIS Not Treated for Water Quality 475 3,958 4,433 The Filterra units were sized based on a volume equal to or greater than 91 percent of the influent runoff volume using the Department of Ecology's Western Washington Hydrologic Model (WWHM). Refer to the WWHM output files and Americast Filterra documentation in Appendix B. Water quality treatment is not proposed in the north basin as this basin will contain a mere 475 square feet of replaced pollution-generating impervious surface. The south basin, however, has 3,958 square feet of pollution-generating impervious surfaces that will not be treated for water quality as the grades will not allow these areas to surface drain to the water quality treatment areas. These areas can be seen - in blue on Figure 1-3F. That said, the proposed water quality treatment facilities have been sized to treat 23,736 square feet, of which 18,491 square feet will be replaced PGIS within Basins A and B. The difference between these two areas is 5,245 square feet (23,736 - 18,491), which is the area of the currently untreated existing roads that will surface drain to the proposed water quality facilities. Therefore, the proposed treatment system will treat 812 square feet beyond what is required (5,245 - 3,958 - 475), thus sufficiently offsetting the areas that will not be treated. Stormwater Technical Information Boeing Buyer Furnished Equipment (BFE) Expansion, Building 4-68, Renton, Washington MAGNUSSON KLEMENCIC ASSOCIATES ■ SECTION V• CONVEYANCE SYSTEM ANALYSIS AND DESIGN HYDROLOGY FOR CONVEYANCE SYSTEM ANALYSIS The KCRTS modeling program was used to determine the design flow rates for this project; the - calculation printouts as well as example calculations can be found in Appendix A. All storm pipes were sized based on the 100-year flow rate. Using 15-minute time steps, this flow rate was found to be 1.29 CFS per acre of impervious surface. Although there is roughly 9,400 square feet of pervious - landscape surfaces, all of the surfaces were modeled as impervious surfaces to maintain a level of conservatism. FlowMaster was used to calculate the flow capacity of the proposed storm drain pipes. The proposed pipe size and slope was used to calculate the full flow capacity. This flow rate was then compared to the 100-year flow rate as a minimum requirement. Figure V-1 shows the flow diagram for the site and all contributing areas and flow rates. The FlowMaster calculation printout shows the pipe's flow capacity on the first page, and the 100-year flow rate for the contributing area can be found on the second page. LIST OF FIGURES ■ Figure V-1 : Flow Diagram SECTION VI* SPECIAL REPORTS AND STUDIES A copy of the Geotechnical Report performed by Soil and Environmental Engineers, Inc., dated March 25, 2011, is provided in Appendix C. SECTION VII: OTHER PERMLTS_ _ . No other permits are provided. SECTION VIII : CONSTRUCTION STORMWATER POLLUTION PREVENTION PLAN ANALYSIS AND DESIGN A TESC plan has been prepared for the project and is included in this report as Appendix E. The plan will meet the minimum TESC requirements as discussed below. A full SWPPP will be provided by the contractor prior to construction of this project. TESC REQUIREMENTS TESC Requirement 1 : Clearing Limits Not applicable. Storr-nwater Technical Information Boeing Buyer Furnished Equipment (BFE) Expansion, Building 4-68, Renton, Washington MAGNUSSON KLEMENCIC ASSOCIATES ■ TESC Requirement 2: Cover Measures Cover measures are addressed in the TESC Plan Notes. TESC Requirement 3: Perimeter Protection Perimeter protection is addressed in the TESC Plan Notes. TESC Requirement 4: Traffic Area Stabilization The stabilized construction entrance will be shown on the plans. The TESC Plan Notes will indicate that State water quality standards are applicable to construction site runoff. TESC Requirement 5: Sediment Retention A sediment retention system is shown on the plans. TESC Requirement 6: Surface Water Control Block and gravel inlet protection is shown on the plans. TESC Requirement 7: Dust Control Air quality will be addressed in the SWPPP. TESC Requirement 8: Wet-Season Construction Wet-season construction will be addressed in the TESC Plan Notes. TES( Requirement 9: Construction within Sensitive Areas and Buffers Does not apply. TESC Requirement 10: Maintenance Maintenance will be addressed in the TESC Plan Notes and SWPPP. TESC Requirement 11: Final Stabilization Final stabilization will be in accordance with the landscape plans for the project. SECTION IX: BOND QUANTITIES WORKSHEET, RETENTION/DETENTION FACILITY SUMMARY SHEET AND DEC'I ARATION OF COVENANT A bond quantities worksheet is not required for this project since it is a privately owned improvement project on private property owned by the Boeing Company. Stormwater Technical Information Boeing Buyer Furnished Equipment (BFE) Expansion, Building 4-68, Renton, Washington MAGNUSSON KLEMENCIC ASSOCIATES IN SECTION X. OPERATIONS AND MAINTENANCE MANUAL - OPERATIONS This project provides storm water treatment facilities to treat runoff. The operation of the treatment facilities will be passive and controlled by gravity. There are no actions required on the part of the Owner aside from maintaining the facilities. While it is not required, the maintenance interval of the proposed facilities can be extended by regularly removing leaves and debris from the roads within the catchment areas. Using a street sweeper regularly, particularly following autumn leaf fall, is highly recommended. Inspections and maintenance will be performed as required by the manufacturer's Operation and Maintenance Manual as well as the KCSWDM. MAINTENANCE The storm water treatment and conveyance facilities will require periodic inspection and cleaning to function properly. The specific areas requiring maintenance are the storm drain pipes and drainage structures. Please refer to Appendix A of the KCSWDM for specific and additional maintenance information. To ensure long-term performance of each Filterra Bioretention System, continual annual maintenance programs should be performed per the latest Filterra Operation and Maintenance Manual; a copy of the current manual is provided in Appendix B of this report. RFFFRFNCFS Surface Water Design Manual, King County Surface Water Management, 2009. City of Renton Amendments to the King County Surface Water Design Manual, February 2010. Pre-Application Meeting with King County Staff, December 16, 2009 (#A09P0169). Washington State Department of Ecology, Stormwater Management Manual for Western Washington, 2005. Stormwater Technical Information Boeing Buyer Furnished Equipment (BFE) Expansion, Building 4-68, Renton, Washington FIGURES ■ MAGNUSSON KLEMENCIC ASSOCIATES KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part PROJECT OWNER AND Part PROJECT LOCATION AND PROJECT ENGINEER DESCR►PTION Project Owner The Boeing Company Project Name Boeing 4_68 BFE Building Phone DDES Permit# NA Address 737 Logan Ave-------------- Location Township T.23N __- Renton, WA 98055 Range ---------------- __ -- --- Project Engineer_ Matthew Jones------ 07 SE ---------------- Section -------- Company Magnusson Klemencic Assoc. Site Address 737 Logan Ave N_ _ Phone 206-292-1200 Renton, Wa 98055 ------------------------------------- Part3 TYPE OF PERMIT APPLICATION Part OTHER REVIEWS AND PERMITS ❑ Landuse Services ❑ D F W HPA ❑ Shoreline Subdivison / Short Subd. / UPD C 0 E 404 Management ❑ Building Services ❑ DOE Dam Safety ❑ Structural M/F / Commerical / SFR Rockery/Vault/_____ ❑ Clearing and Grading ❑ C0EFEM Wetlands ❑ ESA Section 1 ❑ Right-of-Way Use ❑ C 0 E Wetlands ❑ Other ❑ Other Parts PLAN AND REPORT INFORMATION Technical Information Report Site Improvement Plan (Engr. Plans) Type of Drainage Review (iD Targeted / Type (circle one): Full / odifie / (circle): Large Site Small Site Date (include revision ___________________ Date (include revision ________-_-_----_- d ate s): dates): Date of Final: Date of Final: Part6 ADJUSTMENT APPROVALS Type (circle one): Standard / Complex / Preapplication / Experimental/ Blanket Description: (include conditions in TIR Section 2) ------------------------------------------------------------------------------------ D ate of Approval: PROJECT Boeing BFE Building, Renton Washington DATE June 10, 2011 TITLE TIR Worksheet DRAWN BY Figure 1-1 SKETCH# 20M Siaface Water Design Martial 1/9/2009 1 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part7 MONITORING REQUIREMENTS Monitoring Required: Yes / No Describe: _________________________________ ----------------------------------------- Start Date: ----------------------- ----------------------------------------- Completion Date: ----------------------------------------- Part8 SITE COMMUNITY AND DRAINAGE BASIN Community Plan : _ NA ---------------------- Special District Overlays: __________________________________________________________ Drainage Basin: _Lower Cedar River_ - - --------------- Stormwater Requirements: _____________________ rP—aart9 ONSITE AND ADJACENT SENSITIVE AREAS '1v River/Stream Cedar River ❑ Steep Slope 10 Lake Lake Washin ton ------�--------------- ❑ Erosion Hazard ---------------- -- LJ Wetlands ❑ Landslide Hazard --------------------------- ------------------ ❑ Closed Depression ___________________ ❑ Coal Mine Hazard ----______-------- ❑ Floodplain __________________________ ❑ Seismic Hazard ------------------- ❑ Other ❑ Habitat Protection ------------------------------ ------------------ ----------------------------------- High Liquefaction Susceptibility Zone Part 10 SOILS Soil Type Slopes Erosion Potential loose and unconsolidated 1%-- 2% Low ----------------- -------- -------- - ----------- alluvial sediments with ----------------- -----------------interbedded silt,silt, silt, ----------------- ----------------- ----------------- sand, sand, and gravel ----------------- -----------------iZ High Groundwater Table (within 5 feet) ❑ Sole Source Aquifer ❑ Other________________________ ❑ Seeps/Springs ❑ Additional Sheets Attached 2"Staface Water Design Manial 2 1j9/2009 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part11 DRAINAGE DESIGN LIMITATIONS REFERENCE LIMITATION / SITE CONSTRAINT ❑ Core 2 - Offsite Analysis----------------- ---------_------------- ❑ Sensitive/Critical Areas --------------------------------------- ❑ S E P A --------------------------------------- ❑ Other --------------------------------------- ❑ ---- ❑ Additional Sheets Attached Part12 TIR SUMMARY SHEET (provide one TIR Summary Sheet erThresholdDischarge Area) Threshold Discharge Area: name or description) Boeing Renton West Core Requirements (all 8 apply) Discharge at Natural Location Number of Natural Discharge Locations: 1 Offsite Analysis Level: 1 / 2 / 3 dated:N/A=Exemption#3__ Flow Control Level: 1 / 2 / 3 or Exemption Number Direct discharge (incl. facility summary sheet) Small Site BMPs ----------------------------------- Conveyance System Spill containment located at:oil water separator#43 in sub-basin 32 ---- -- — -------- and#49& 50 in sub-basin 34. Erosion and Sediment Control ESC Site Supervisor: Keith Johnson, LeaseCrutcherl-ewis Contact Phone: 206-730-0915 After Hours Phone: Maintenance and Operation Responsibility: rivat / Public If Private, Maintenance Lo Re uired: Yes No Financial Guarantees and Provided: Yes No Liability Water Quality Type: Basic / Sens. Lake / nhanced Basicm / Bog (include facility summary sheet) or Exemption No. ---------------------- Landscape Management Plan: Yes No Special Requirements (as applicable) Area Specific Drainage Type: C DA / SDO /MDP / BP / LMP / Shared Fac./ one Requirements Name: Flood plain/Floodway Delineation Type: Major / Minor / Exemption / one 100-year Base Flood Elevation (or range): -------------- Datum: Flood Protection Facilities Describe: NA Source Control Describe landuse: Industrial (comm./industrial landuse) Describe an structural controls: Y Vehicle& Equipment inspection, product storage, spill prevention implementation 2"Surface Water Design Manual 3 1/9/2009 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Oil Control High-use Site: Yes No Treatment BMP: -------------------------------- Maintenance Agreement: Yes / No with whom? N/A ------------------------------------ Other Drainage Structures Describe: Part13 EROSION AND SEDIMENT CONTROL REQUIREMENTS MINIMUM ESC REQUIREMENTS MINIMUM ESC REQUIREMENTS _ram DURING CONSTRUCTION AFTER CONSTRUCTION Y� Clearing Limits Stabilize Exposed Surfaces Cover Measures Remove and Restore Temporary ESC Facilities 10 Perimeter Protection Clean and Remove All Silt and Debris, Ensure Traffic Area Stabilization Operation of Permanent Facilities Sediment Retention ❑ Flag Limits of SAO and open space preservation areas Surface Water Collection ❑ Other r� ---------------------- " Dewatering Control *w Dust Control ❑ Flow Control Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility So mary and Sketch) Flow Control Type/Description Water Quality Type/Description ❑ Detention ---------------- ❑ Biofiltration -------- -- ❑ Infiltration ---------------- ❑ Wetpool ---------------- ❑ Regional Facility ---------------- ❑ Media Filtration ------__ ❑ Shared Facility ---------------- ❑ oil Control ❑ Flow Control ❑ Spill Control BMPs ---------- — ❑ Flow Control BMPs ❑ Other --- ------ Id Other Americast Filterra System ---------------- 2000 Surface Water Design Manual 4 1/9/2009 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET P art 15 EASEMENTS/TRACTS Part16 STRUCTURAL ANALYSIS ❑ Drainage Easement ❑ Castin Place Vault ❑ Covenant °&d Retaining Wall ❑ Native Growth Protection Covenant ❑ Rockery > 4' High ❑ Tract ❑ Structural on Steep Slope ❑ Other ❑ Other P art 17 SIGNATURE Of PROFESSIONAL ENGINEER I, or a civil engineer under my supervision, have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attached Technical Information Report. To the best of my knowledge the information provided here is accurate. Signed/Date 2009 Strface Water Design Manual 1�J/100� 5 • w Seattle i r .[' 17, } r e "'T King County t (l. 4►. �'y •. ..:*.Project Site �wFw R 2_ ��• ��, r e~.:ljjt t. � s ae r F � t IL PROJECT Boeing BFE Building; Renton,Washington DATE June 10, 2011 TITLE Vicinity Map DRAWN BY Figure 1-2A SKETCH# MAGNUSSON KLEMENC[C ASSOCIATES Lake Washington 9 1 /✓ � q � � 4 it ",vow" 1Y. . o 0 fl.. 1 Project Site N, t , � �� + >>� � ` t,\ (see figures 1-3) otit ■ ■ ■ rr■ ■ ■ r ■ ■ ■ ■ ■ ■ r ■ r ■�l� �� 11,t`�'"�., ... 1ns=�"^..� ■ _:..%rIT' yi1W�w.o�i�'`a{� _ �„ ■ ■ �1 �1 f??ftlrftl7�!.,.1(•MRtirittr: ■ ■ ■ ■ ■ ■ ■ ■ ■ ti ■ ■ ■ r ■ ■ r ■ ■ ■ ■ ■ r ■ rr ■ ■ ■ Existing 4-75 Building Proposed 4-68 BFE Building Limits of Work PROJECT Boeing BFE Building; Renton,Washington DATE June 10, 2011 TITLE Renton Facility Map DRAWN BY Figure 1-2B SKETCH # MAGNUSSON KLEMENCIC ASSOCIATES ^ 14th Lake Washington NE 12th St. 13th c idth S �� 90 ' a as 1900 =S 16th S. I� i7th �Q 'k N IDth St. 17th -i � r 181h S ,i Z � c 191h S F D 20th S n - t lD z G - S I S 121st St. G nd t, a wv 71h st. 4Pra e t Site ¢ A PI dth t. N 6th St N Sth St. tith St. S 125th Sc N1W 5th St. > r i N 5th t � � 0 __.ITT N 4th St. 3 a z z m m m 2nd Air 8 132n d StC1 Ave S 7 S obinof _ �� n` FLOOD HAZARD AREA 100 Year Flood Plain PROJECT Boeing BFE Building; Renton,Washington DATE June 10, 2011 TITLE Flood Hazard Area DRAWN BY Figure I-2C SKETCH# MAGNUSSON KLEMENCIC ASSOCIATES z z � a �� m o Y l Lake WashingtonL Jo C, U 8 \� NE 12th St < O O `-- i "I I �• c > m 11m a\ � 3 E�Jtsn, S :. 1900 v ]E:slE NE 10th (. 1 Sth S _ 8 NE 10[h PI. -.. E 9th O1 17th N 10 5� NI_"_' . � Z m �L PS ;qfts '1, l if . m2 NE 8m PI. jr IFEW41 Z m Z N 8th SL y§ y S 121st 1St ,22nd Z11 rp a 123. t�< NW 71h St� a ::: a O \ -- PI 1231d Pl. + .,1 t C W � B NYd f ject S �. m� ,2�th t. � N �tee > S,25th St. �� °' NW 50 St. I A - >I N Sth t. v ai E NE �� y't° N� EdmoCnd+ FW Ferndall e u f N 4th St / 3 W m ❑� , I11mpLEIII ` e h St 3 \ > NE3rast A 2 d � I S 132nd St W 9 \ (^__ Ave LD m St S2ntlSt 9 S nd \ ` o SE2ndP e �ST {(�}� Slry S3rd St a � a11 3rd PI - ....'We a a. p, ICE V- HAZARD CONDITION Liquefaction Susceptibility S high moderate to high low to moderate Renton City Limits PROJECT Boeing BFE Building; Renton,Washington DATE June 10, 2011 TITLE Liquefaction Hazard Area DRAWN BY ■ Figure I-2D SKETCH# MAGNUSSON KLEMENCIC ASSOCIATES r" Lake Washington Discharge Location into i \ Lake Washington s i 1 't 60"RCP Storm Pipe i 54"RCP Storm Pipe CD North Basin 32 Q N � See Figure 1-3C -------------------- North Basin connection South Basin 34 to storm system --- ----------------- South Basin connection o storm system PROJECT Boeing BFE Building; Renton,Washington DATE June 10,2011 TITLE Overall Drainage Basins and Downstream Discharge DRAWN BY Figure 1-3A SKETCH# MAGNUSSON KLEMENCIC ASSCC.AT ES Storm system discharges directly un 01into lake Washington .45 �11 ` 0 A,g0 North Basin (32) Viz z � D-63'J L � I � 32 �6t6 fiE 6 8 1 6 6 ��)�ZKEYMAP-NO SCALE ' (n ' 6 �� SHEET% OUT � cs Wa c ar D 35 B a] 41 CCI JI LB-file CB Y+3.L .I ov ReY .�� °" South Basin (34) LEGEND BUILDING LINEsR-6�a PROPERTY LINE v.ce-ss}c !I q 1 Y STORM DRAIN LINE (73 1 MAJOR DRAINAGE BASIN °B-spa CB-6)]B, FLOW ARROW I,, T se=- +��L1�a r'•, `-- B s" cs a„+ -ai C. 1 r' WATER FLOW TO GROUND �'', :e ss -A - 'Cs-nNB vcs-666 BEFORE ENTERING STORM 111,�/�_ 9 B"M1NE nA wa t 1 m STEM ROWS OIL WATER SEPARATOR A Ic6-614 -.,b, � > CB CATCH BASIN •,'•z 1 �cB-ees r e�< I W Q �+ CO CLEAN OUT DI DRAIN INLET -, --�-NE3:aa} 34 1 Q x 1 ,p CB-6Bi ` C6-di} 1 N North Discharge 6D �° 5 PARKiNG OT , 1 cs-6a] }cB-a;z Location to Storm 1----"'1 �. G 1 \�� 6_aP; I C ce-690. O Pipe ^ �' cB-svT l \ cs-sa< cs-evl I ,r . a -6<ee at e6-sa \r6-66Y 1 1 � CB-699a �p e-NI 1 LEGEND '� iFr��- •�ce-666 TltlCK-I'R-EE SINGLE QQUELE 011lE BERMED.1 -6+68 �C9-699 , 1'�B 9+ CB wCq cB-6Etl Y F t!f CHEVi PRODUCT WKL WdLLEQ > Project c.- r C6-d6ri �-4-L O j7 1N+15 a OI ,/I `: lANN610L) IM1 W� Location ICe aatl C36d�� .�`§ Z�-- —"-B i '-__-_y``-no1 W TA°AA.asRous wESTE @ 1 �4-6J ce-TDa; ce-stla .�. LZ. 0 PERMS w RULE o ( cfi>.a- 'nsc 1 jcB-m6e o Q C MRo u"w" f TANKS ® tlR ¢ce-6.- l I a i Z w=1 ED KNE NqE IgII _ <R-�031, 1:6-^O6B DIL PRODUCT/WASTE DRUM LOCAT*N AREA AIRCRAFT FUELING STATION C._637E VEHICLE FUELING STATION N TRANSFORMER South Discharge ;° _ I �, PaRKlh,)LCT ss m m Location to Storm Ill }C6-E]B 46-,D.6 1 1 R,aT� LU C Pipe I ,, c6-,oss <6 w6B w�z. m A. M o ', I I L - n j WD6-6+° R°"6,° NORTH 6TH STREE y ' I�.'' HDN_BOERF OIREUl - aria"-.• - Dln a RENTON our L - m Eu ti SCALE IN FFFT k Storm System Discharges to the North, See r ,_ Figure 1-3A � , y North Sub-Basin(within ` + construction limits) \ Storm System �5 Connects to t�+t _ � the West = t` Division Between North and South � Basins _ i 4--75 South Sub-Basin (within constructions -;1l —� limits) ^ f — 1 Existing 54"SD pipe,Discharge to Lake Washington r Existing North Basit SD System to remain ! , ----_ ss-------, Existing North Basin SO System to be removed Storm System f'f Connects to p, Existing South Basin SD System to remain the West, See x / ---- ------ ----, Existing South Basin SD System to be removed � Figure 1-3A 100 50 0 100 200 SCALE 1"=100' FEET PROJECT Boeing HE Building; Renton,Washington DATE June 10, 2011 TITLE Site Sub-Basins DRAWN BY Figure I-3C SKETCH# MAGNUSSON KLEMENCIC ASSOCIATES Existing 4-70 Building Limits of } P M ( Construction Property Line .' �'� 7� Covered Pedestrian Walk r Existing 4-75 Building 1 Asphalt Paving i ) i —� •�� j Concrete Paving Asphalt Over � _ ,y Concrete Paving Limits of Construction r ,■ z T i - CD i - 1 }i} � Property Line J�-f 'I00 50 0 100 200 SCALE V=100' FEET PROJECT Boeing BFE Building; Renton,Washington DATE June 10, 2011 TITLE Existing Site Conditions DRAWN BY Figure 1-31D SKET(:H# MAGNUSSON KLEMENCIC ASSOCIATES • } y g -• ! • Property Line North Building Concrete r i • !� ti Driveway Accesst • Pedestrian Sidewalk jConcrete Loading Docks • / Existing 4-75 Building • Proposed New Asphalt 1 4-68 Building Pavement 1 , r 1 • Saw Cut Line and —r- Limits of Work Saw Cut Line and Limits of Work Pedestrian South Building Concrete Sidewalk Driveway Access Property Line i 100 50 0 100 200 SCALE 1"=100' FEET PROJECT Boeing BFE Building; Renton,Washington DATE June 10, 2011 TITLE Proposed Site Conditions DRAWN BY Figure I-3E SKETCH# MAGNUSSON KLEMENCIC New Basin Division Boundary North basin areas outside of Swpe NA BASIN AREA K ;r •� BASIN AREAL BASIN AREA F-4 BASIN AREA D I BASIN AREA F•e ARFA E • BASIN AREA A BASIN AREA F41_4 �\ Water Quality Treatmont N AREA 0 Pilterra Water Quality Vaults ¢ayy� WA F w. BASIN AREA FL BASINAREAJ +�s495a' W BASIN AREA 1 South basin area outside of scope South basin area outside of scope 50 0 s0 too SCALE 1"=50' FEET LEGEND Replaced Pollution Generating Surfaces being treated for water quality Replaced Pollution Generating Surfaces not being treated for water quality Existing(Undisturbed)Pollution Generating Surfaces being treated for water quality Basin areas outside of scope(no now construction) Proposed Sloop Conveyance System ■ Proposed Catch Basin • Proposed Down Spout PROJECT Boeing BFE Building; Renton,Washington DATE June 10,2011 TITLE Proposed Drainage System DRAWN BY Figure 1-3F SKETCH# MAGNUSSON KLEMENCIC ASSOCIATES If �� ■ I U r 161 z ••••- Ur • A g D fr:•;:•�: ::r;` �i 1 AgC E T Ic • A R 0 ' ;BM • . — k thletic I �" e • 9 n 'FieldI t • U r �' • , EvD •• • 4b ja/ i Ur I' • AkF \ G ` I n • • . .- , •,fit old • Cem • Pa rk PC Rh �,. Sc f I/ C' AkF ,o 11 U rAkF . S I I i •i� Y Inc ' Ur = loose and unconsolidated alluvial sediments PROJECT Boeing BFE Building; Renton,Washington DATE June 10, 2011 TITLE Soils Map DRAWN BY Figure 1-4 SKETCH# MAGNUSSON KLEMENCIC ASSOCIATES SECTION 3.2 RUNOFF COMPUTATION AND ANALYSIS METHODS FIGURE3-1.A 2-YEARYIFI-IOURISOPLUVLUS SNO�O�ISN COUNTY KING COUNTY 1.8 nx.,xv j L aoxo 1 r C\i N 00 CV 2.0 0) gar CV O sE.r �C ♦xv -I i-r L T- ,�� -.1 I 1 " J x I[ Project Site d ri:. •s a �r— Q ( CID CV ', •uYU _ (V C N -- z. r 'AcG !KING COUNTY ^^Q• `- PIERCE COUNTY 'Y WESTERN KING COUNTY Zoe - �` 3.5 2-Year 24-Hour Precipitation `� C in Inches 0 Mlles — � PROJECT Boeing BFE Building; Renton,Washington DATE June 10, 2011 TITLE 2-year, 24-hour Precipitation DRAWN BY Figure II-1 SKETCH# MAGNUSSON KLEMENCIC ASSOCIATES SECTION 3.2 RUNOFF COMPUTATION AND ANALYSIS METHODS FIGURE--L?—I.0 2i-YEAR011-HOURLSOPLUVIAUS 711 __SN HOMIGH COUNTY KING COUNTY '.9 0.0 'V 5.0 iNa I�qv Project Site J-- D Cb N Yy PIERCE COUNTY WESTERN KING COUNTY 5_5 5.0 4.5 25-Year 24-Hour Y Precipitation 1\ 0 in Inches L.-�2 4 Miles� PROJECT Boeing BFE Building; Renton,'Washington DATE June 10, 2011 TITLE 25-year, 24-hour Precipitation DRAWN BY ■ Figure 11-2 SKETCH# MAGNUSSON KLEMENCIC ASSOCIATES 3.2.1 RATIONAL METHOD IIGURE,3?-l.D MYFAR3t LOUR LSC*LMMS 0 q 0 7 0, COUNTY 6 d -A f j-1 .0 43 IV Ln Project Site 1� j r, _J 01 N Jail COUNTY — PIE GE COUNTY WESTERN 0) KING COUNTY Cb*. , �,I ll-�.- - 6.5 l - 6.0 N N* rt, , - 5.5 100-Year 24-Hour Precipitation 0 2 4 Wes in Inches PROJECT Boeing BFE Building; Renton,Washington DATE June 10, 2011 TITLE 100-year, 24-hour Precipitation DRAWN BY ■ Figure 11-3 SKETCH# MAGNUSSON KLEMENCIC ASSOCIATES North Existing Conveyance 12 Basin K Basin L Basin M Area:4,256 sf Area: 2,349 sf Area: 7,414 sf 25 yr: 0.11 cfs 25 YR:0.06 cfs 25 yr: 0.18 cfs Basin C 100 yr:0.13 cfs 100 YR: 0.07 cfs 100 yr:0.22 cfs Area:8,326 sf 25 yr: 0.21 cfs TOTAL 100 yr:0.25 cfs Area: 20,827 sf 100 yr: 0.62 cfs Basin D Area:2,566 sf 25 YR: 0.06 cfs 11 100 YR: 0.08 cfs Basin Area: 10,934934 sf TOTAL Down Spout 25 yr: 0.26 cfs Area:2,566 sf 100 yr:0.31 cfs Basin N 100 yr:0.08 cfs Area: 18,478 sf 25 yr:0.46 cfs O100 yr: 0.55 cfs Basin F-B 2-A Down Spout Area: 8,332 sf m O 25 yr: 0.21 cfs y 100 yr: 0.25 cfs k Basin E W Area: 2,697 sf 25 YR: 0.07 cfs 100 YR: 0.08 cfs Roof Drainage TOTAL Area:24,529 sf Basin G 100 yr:0.72 cfs Area: 18,492 sf 25 yr: 0.46 cfs Basin F-D Basin F-C 100 yr: 0.55 cfs Basin A 3 Area: 51,673 sf Area: 1,623 sf Area: 15,480 sf TREATED FOR WQ 25 yr: 1.28 cfs 25 yr: 0.04 cfs 25 YR: 0.38 cfs 100 yr: 1.53 cfs 100 yr:0.05 cfs O 100 YR: 0.46 cfs s TOTAL Down Spout Area:48,335 sf 100 yr: 1.43 cfs O Basin I Basin J O Area: 5,560 sf Area: 3,040 sf 25 YR:0.14 cfs 25 YR: 0.08 cfs Basin B Basin H 100 YR: 0.16 cfs 100 YR: 0.09 cfs Area: 10,707 sf Area:9,756 sf TOTAL TOTAL TREATED FOR WQ O 25 YR:0.24 cfs Area: 7,183 sf Area: 21,532 sf 25 YR: 0.27 cfs 100 YR: 0.29 cfs 100 yr:0.21 cfs 100 yr: 0.64 cfs 100 YR: 0.32 cfs TOTAL TOTAL Area:68,798 sf O Area: 59,042 sf 100 yr:2.04 cfs 10 100 yr: 1.75 cfs # Corresponds to associated flow O master calculations South Existing Conveyance > Existing Pipes -� Proposed Pipes PROJECT Boeing BFE Building; Renton,Washington DATE June 10, 2011 TITLE Flow Diagram DRAWN BY Figure V-1 SKETCH# MAGNUSSON KLEMENCIC ASSOCIATES APPENDICES ■ MAGNUSSON KLEMENCIC ASSOCIATES Appendix A: Stormwater Calculations Worksheet for 1 Basin C Project Description Friction Method Manning Formula Solve For Full Flow Capacity Input Data Roughness Coefficient 0.010 Channel Slope 0.00760 ft/ft Nonnal Depth 1.00 ft Diameter 1.00 ft Discharge 4.04 ft3/s Results Discharge 4.04 ft3/s Normal Depth 1.00 ft Flow Area 0.79 ft2 Wetted Perimeter 3.14 ft Hydraulic Radius 0.25 ft Top Width 0.00 ft Critical Depth 0.85 ft Percent Full 100.0 % Critical Slope 0.00715 ft/ft Velocity 5.14 ft/s Velocity Head 0.41 ft Specific Energy 141 ft - Froude Number 0.00 Maximum Discharge 4.34 ft=/s Discharge Full 4.04 1113/s Slope Full 0-00760 ft/ft Flow Type SubCritical GVF Input Data Downstream Depth 0 00 ft Length 000 ft Number Of Steps 0 GVF Output Data - Upstream Depth 0.00 ft Profile Description Profile Headloss 0 00 ft Average End Depth Over Rise 0.00 Bentley Systems,Inc. Haestad Methods SolfikWA140phlewMaster V8i(SELECTseries 1) 108-11.01.031 5/6/2011 5:06:06 PM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Page 1 of 2 Worksheet for 1 Basin C GVF Output Data Normal Depth Over Rise 100-00 % Downstream Velocity Infinity ft/s Upstream Velocity Infinity fUs Normal Depth 1.00 ft Critical Depth 0.85 ft Channel Slope 0.00760 Wit Critical Slope 0.00715 fUft Messages Notes 100 year Flow Rate=0.25CFS Into a 12"@.76%Existing pipe Bentley Systems,Inc. Haestad Methods SolaealldjeFleNMaster V8i(SELECTseries 1) [08-11-01.031 5/6/2011 5:06:06 PM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Page 2 of 2 Worksheet for 2 Basin D Project Description Friction Method Manning Formula Solve For Full Flow Capacity Input Data Roughness Coefficient 0.012 Channel Slope 0.00500 ft/ft Normal Depth 050 ft Diameter 0.50 ft Discharge 0.43 ft'/s Results Discharge 0.43 ft'/s Normal Depth 050 ft Flow Area 0.20 ft' Wetted Perimeter 157 ft Hydraulic Radius 0.13 ft Top Width 0-00 ft Critical Depth 0.33 ft Percent Full 100-0 Critical Slope 0-00809 fUft Velocity 2.19 ft/s Velocity Head 0.07 ft Specific Energy 0.57 ft Froude Number 0-00 Maximum Discharge 0.46 ft'/s Discharge Full 0.43 ft'/s Slope Full 0-00500 ft/ft Flow Type SubCritical GVF Input Data Downstream Depth 0-00 ft Length 0.00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0.00 ft Profile Description Profile Headloss 0.00 It Average End Depth Over Rise 0.00 Bentley Systems,Inc. Haestad Methods Solfil- dlef lewMaster V8i(SELECTseries 1) [08.11.01.031 5/11/2011 8:50:22 AM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1.203-755-1666 Page 1 of 2 Worksheet for 2 Basin D GVF Output Data Normal Depth Over Rise 100.00 % Downstream Velocity Infinity ft/s Upstream Velocity Infinity f/s Normal Depth 0.50 ft Critical Depth 0.33 ft Channel Slope 0.00500 fult Critical Slope 0-00809 ft/ft Messages Notes 100 Yr Flow Rate Basin D=0-08CFS Total Flow Rate=0.08CFS Bentley Systems,Inc. Haestad Methods Soliliki"dkeF mMaster V8i(SELECTseries 1) [08.11.01.031 5/11/2011 8:50:22 AM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Page 2 of 2 Worksheet for 2-A Basin F-A Project Description Friction Method Manning Formula Solve For Full Flow Capacity Input Data Roughness Coefficient 0.012 Channel Slope 0.00500 fUft Normal Depth 0.67 ft Diameter 0.67 ft Discharge 0-93 ft'/s Results Discharge 0-93 ft'/s Normal Depth 0.67 ft Flow Area 0.35 ft' Wetted Perimeter 2.09 ft Hydraulic Radius 0-17 ft Top Width 0.00 If Critical Depth OA6 ft Percent Full 100.0 Critical Slope 0.00757 ft/ft Velocity 2.65 fUs Velocity Head 0.11 ft Specific Energy 0.78 ft Froude Number 0.00 Maximum Discharge 1.00 ft'/s Discharge Full 0.93 ft'/s Slope Full 0.00500 ft/ft Flow Type SubCritical GVF input Data Downstream Depth 0.00 ft Length 0-00 ft Number Of Steps O GVF Output Data Upstream Depth 0-00 ft Profile Description Profile Headloss 0-00 ft Average End Depth Over Rise 0.00 /o Bentley Systems,Inc. Haestad Methods Solfi*"44efilewMaster V8i(SELECTseries 1) [08.11.01.031 5/11t2011 8:53:33 AM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Page 1 of 2 Worksheet for 2-A Basin F-A GVF Output Data Normal Depth Over Rise 100 00 % Downstream Velocity Infinity fUs Upstream Velocity Infinity fUs Normal Depth 0.67 ft Critical Depth 0.46 ft Channel Slope 0.00500 Wit Critical Slope 0.00757 ft/ft Messages Notes 100 Yr Flow Rate From Basin D=0.08CFS 100 Yr Flow Rate From Basin F-A=0-31 CFS Total Flow Rate=0.39CFS Bentley Systems,Inc_ Haestad Methods Sol®i"djeFilewMaster V8i(SELECTseries 1) 108.11.01.031 5/11/2011 8:53:33 AM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Page 2 of 2 Worksheet for 3 Basin E Project Description Friction Method Manning Formula Solve For Full Flow Capacity Input Data Roughness Coefficient 0.012 Channel Slope 0.00500 ft/ft Normal Depth 1.00 ft Diameter 1.00 ft Discharge 2.73 ft3/s Results Discharge 2.73 W/s Normal Depth 1.00 ft Flow Area 0.79 ft1 Wetted Perimeter 3.14 ft Hydraulic Radius 0.25 It Top Width 0.00 ft Critical Depth 0.71 It Percent Full 100.0 % Critical Slope 0.00692 ft/ft Velocity 3.47 fUs Velocity Head 0.19 ft Specific Energy 1.19 ft Froude Number 0.00 Maximum Discharge 2.94 ft'/s Discharge Full 2.73 ft'/s - Slope Full 0.00500 ft/ft Flow Type SubCritical GVF Input Data Downstream Depth 000 ft Length 0 00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0.00 ft Profile Description Profile Headloss 0 00 ft Average End Depth Over Rise 000 % Bentley Systems,Inc. Haestad Methods Solft"d fAwMaster V8i(SELECTseries 1) [08.11.01.031 5111/2011 8:55:02 AM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1.203-755-1666 Page 1 of 2 Worksheet for 3 Basin E GVF Output Data Normal Depth Over Rise 100-00 % Downstream Velocity Infinity ft/s Upstream Velocity Infinity ft/s Normal Depth 1.00 ft Critical Depth 0.71 ft Channel Slope 0.00500 ft/ft Critical Slope 0.00692 ft/ft Messages Notes 100 Yr Flow Rate From Basin D=0-08CFS 100 Yr Flow Rate From Basin F-A=0.31CFS 100 Yr Flow Rate From Basin F-B=0 25 CFS 100 Yr Flow Rate From Basin E=0.08CFS Total Flow Rate=0.72CFS Bentley Systems,Inc. Haestad Methods SolfilikntloDphlewMaster V8i(SELECTseries 1) 108.11.01.031 5111/2011 8:55:02 AM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Page 2 of 2 Worksheet for 4 Basin A Project Description Friction Method Manning Formula Solve For Full Flow Capacity Input Data Roughness Coefficient 0.010 Channel Slope 0-00600 ft/ft Normal Depth 1.00 ft Diameter 1_00 ft Discharge 3.59 ft'/s Results Discharge 3.59 ft'/s Normal Depth 1.00 ft Flow Area 0.79 ftz Wetted Perimeter 3.14 It Hydraulic Radius 0.25 ft Top Width 0.00 ft Critical Depth 0.81 ft Percent Full 100.0 % Critical Slope 0-00615 ft/ft - Velocity 4.57 ft/s Velocity Head 0.32 ft Specific Energy 1.32 ft Froude Number 0.00 Maximum Discharge 3.86 W/s Discharge Full 3.59 ft'/s Slope Full 0.00600 ft/ft Flow Type SubCritical GVF Input Data Downstream Depth 0 00 ft Length 0-00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0.00 ft Profile Description Profile Headloss 0.00 ft Average End Depth Over Rise 000 % Bentley Systems,Inc. Haestad Methods SolOW"O fiiiDwMaster V8i(SELECTseries 1) [08.11.01.031 6/7/2011 10:19:20 AM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Page 1 of 2 Worksheet for 4 Basin A GVF Output Data Normal Depth Over Rise 100.00 % Downstream Velocity Infinity ft/s Upstream Velocity Infinity ft/s Normal Depth 1.00 It Critical Depth 0.81 ft Channel Slope 0-00600 ft/ft - Critical Slope 0.00615 ft/ft Messages Notes 100 Yr Flow Rate From Basin C=0.25CFS 100 Yr Flow Rate From Basin D=0.08 CFS 100 Yr Flow Rate From Basin E=0.08CFS 100 Yr Flow Rate From Basin F-A=0.31CFS 100 Yr Flow Rate From Basin F-B=0.25CFS 100 Yr Flow Rate From Basin A=0.46CFS Total Flow Rate= 1.43CFS Discharge through existing 12"pipe @.6% - I Bentley Systems,Inc- Haestad Methods Sol EbivWd3pF1ewMaster V8i(SELECTseries 1) [08-11.01-031 6/7/2011 10:19:20 AM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Page 2 of 2 Worksheet for 5 Basin B Project Description Friction Method Manning Formula Solve For Full Flow Capacity Input Data Roughness Coefficient 0.010 Channel Slope 0.00296 ft/ft Normal Depth 1.00 ft Diameter 1.00 ft Discharge 2.52 fP/s Results Discharge 252 ft'/s Normal Depth 1.00 ft Flow Area 0.79 ft' Wetted Perimeter 3.14 ft Hydraulic Radius 025 ft Top Width 0.00 ft Critical Depth 0.68 ft Percent Full 100.0 % Critical Slope 0.00456 fUft Velocity 321 fUs Velocity Head 0,16 ft Specific Energy 1.16 ft Froude Number 0.00 Maximum Discharge 2.71 ft'/s Discharge Full 2.52 ft'/s Slope Full 0-00296 fUft Flow Type SubCritical GVF Input Data Downstream Depth 0 00 ft Length 0.00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0-00 ft Profile Description Profile Headloss 0.00 ft Average End Depth Over Rise 0-00 % Bentley Systems,Inc_ Haestad Methods Sol ftm*ldjefilewMaster V8i(SELECTseries 1) 108.11.01.031 V7/2011 11:20:34 AM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Page 1 of 2 Worksheet for 5 Basin B GVF Output Data Normal Depth Over Rise 100.00 % Downstream Velocity Infinity ft/s Upstream Velocity Infinity fUs Normal Depth 1.00 It Critical Depth 068 It Channel Slope 000296 ft/ft Critical Slope 000456 Wit Messages Notes 100 Yr Flow Rate From Basin C=0.25CFS 100 Yr Flow Rate From Basin D=0-08 CFS 100 Yr Flow Rate From Basin E=0.08CFS 100 Yr Flow Rate From Basin F-A=0.31CFS 100 Yr Flow Rate From Basin F-B=0.25CFS 100 Yr Flow Rate From Basin F-B=0.25CFS 100 Yr Flow Rate From Basin A=0A6CFS 100 Yr Flow Rate From Basin B=0 32CFS Total Flow Rate= 1.75CFS Discharge through existing 12"pipe @.296 Bentley Systems,Inc. Haestad Methods Sol&"Wd.efikewMaster V8i(SELECTseries 1[ [08.11.01-031 6/7/2011 11:20:34 AM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Page 2 of 2 Worksheet for 6 Basin H Project Description Friction Method Manning Formula Solve For Full Flow Capacity Input Data Roughness Coefficient 0.010 Channel Slope 0.01000 tuft Normal Depth 1.00 ft Diameter 1.00 ft Discharge 4.63 ft'/s Results Discharge 4.63 ft'/s Normal Depth 1.00 It Flow Area 0.79 ft' Wetted Perimeter 3.14 ft Hydraulic Radius 0.25 ft Top Width 0.00 ft Critical Depth 0.90 It Percent Full 100.0 % Critical Slope 0.00884 ft/ft Velocity 5.90 ft/s Velocity Head 0.54 ft Specific Energy 1.54 ft Froude Number 0.00 Maximum Discharge 4-98 fP/s Discharge Full 4-63 ft'/s Slope Full 0.01000 ft/ft Flow Type SubCritical GVF Input Data Downstream Depth 0 00 ft Length 0.00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0.00 ft Profile Description Profile Headloss 0.00 ft Average End Depth Over Rise 0.00 % Bentley Systems,Inc. Haestad Methods SolitwYgeFlewiMaster V8i(SELECTseries 1) 108.11.01.031 6/7/2011 10:22.27 AM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Page 1 of 2 Worksheet for 6 Basin H GVF Output Data Normal Depth Over Rise 100.00 % Downstream Velocity Infinity fUs Upstream Velocity Infinity fUs Normal Depth 1.00 It Critical Depth 0-90 It Channel Slope 0.01000 ft/ft Critical Slope 0.00884 fUft Messages Notes 100 Yr Flow Rate From Basin C=025CFS 100 Yr Flow Rate From Basin D=0.08 CFS 100 Yr Flow Rate From Basin E=0-08CFS 100 Yr Flow Rate From Basin F-A=0.31 CFS 100 Yr Flow Rate From Basin F-B=0.25CFS 100 Yr Flow Rate From Basin F-B=025CFS 100 Yr Flow Rate From Basin A=0.46CFS 100 Yr Flow Rate From Basin B=0-32CFS 100 Yr Flow Rate From Basin H=0.29CFS Total Flow Rate=2.04CFS Into a 12"@ 1%Existing pipe Bentley Systems,Inc. Haestad Methods So1ililkii"d4eRmMaster V8i(SELECTseries 1) [08.11.01.031 6/7/2011 10.22.27 AM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Page 2 of 2 Worksheet for 7 Basin F-D Project Description Friction Method Manning Formula Solve For Full Flow Capacity Input Data Roughness Coefficient 0.010 Channel Slope 0-00600 fUft Normal Depth 1.00 ft Diameter 1_00 ft Discharge 3.59 ft3/s Results Discharge 3.59 ft'/s Normal Depth 1.00 ft Flow Area 0.79 ftz Wetted Perimeter 3.14 ft Hydraulic Radius 0.25 ft Top Width 0.00 ft Critical Depth 0.81 ft Percent Full 100.0 % Critical Slope 0.00615 ft/ft Velocity 4.57 ft/s Velocity Head 0.32 ft Specific Energy 1.32 ft Froude Number 0.00 Maximum Discharge 3.86 ft'/s Discharge Full 3.59 ft'/s Slope Full 0-00600 ft/ft Flow Type SubCritical GVF Input Data Downstream Depth 0.00 ft Length 0.00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0 00 ft Profile Description Profile Headloss 0 00 ft Average End Depth Over Rise 0.00 % - Bentley Systems,Inc_ Haestad Methods SolitiatlQeli Master V8i(SELECTseries 1) [08.11.01.03] 5/1112011 1:47:01 PM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Page 1 of 2 Worksheet for 7 Basin F-D GVF Output Data Normal Depth Over Rise 100.00 % Downstream Velocity Infinity fUs Upstream Velocity Infinity fUs Normal Depth 1.00 It Critical Depth 0.81 It Channel Slope 0.00600 ft/ft Critical Slope 0.00615 ft/ft Messages Notes 100 Yr Flow Rate Basin F-D =1.53CFS Bentley Systems,Inc. Haestad Methods Sol Blit"43,049wM aster V8i(SELECTseries 1) [08.11.01.031 5/11/2011 1:47:01 PM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Page 2 of 2 Worksheet for 8 Basin 1 Project Description Friction Method Manning Formula Solve For Full Flow Capacity Input Data Roughness Coefficient 0.010 Channel Slope 0.01460 ft/ft Norma[Depth 0.67 It Diameter 0.67 It Discharge 1.90 ft'/s Results Discharge t90 ft'/s Normal Depth 0.67 It Flow Area 0.35 ft' - Wetted Perimeter 2.10 It Hydraulic Radius 0.17 ft Top Width 0.00 It Critical Depth 0.62 It Percent Full 100.0 % Critical Slope 0.01263 ft/ft Velocity 5.44 ft/s Velocity Head 0.46 ft Specific Energy 1.13 ft Froude Number 0.00 Maximum Discharge 204 ft'/s Discharge Full 1.90 ft'/s Slope Full 0.01460 ft/ft Flow Type SubCritical GVF Input Data Downstream Depth 0.00 ft Length 0.00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0.00 It Profile Description Profile Headloss 0.00 It Average End Depth Over Rise 0.00 % Bentley Systems,Inc. Haestad Methods SolaimdESefifenMaster V8i(SELECTseries 1) [08.11,01-031 5/11/2011 1:48:06 PM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Page 1 of 2 Worksheet for 8 Basin 1 GVF Output Data Normal Depth Over Rise 100.00 % Downstream Velocity Infinity fUs Upstream Velocity Infinity fUs Normal Depth 0.67 ft Critical Depth 0.62 ft Channel Slope 0.01460 ft1ft Critical Slope 0.01263 ft/ft Messages Notes 100 Yr Flow Rate From Basin F-C=0-05CFS 100 Yr Flow Rate From Basin I=0.16CFS Total Flow Rate=0.21 CFS Bentley Systems,Inc_ Haestad Methods Sol®iaillt%eFEenMaster V8i(SELECTseries 1) [08.11.01.031 5/11/2011 1:48:06 PM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Page 2 of 2 Worksheet for 9 Basin G Project Description Friction Method Manning Formula Solve For Full Flow Capacity Input Data Roughness Coefficient 0.012 Channel Slope 0.00500 ft/ft Normal Depth 0.67 It Diameter 0.67 It Discharge 0.93 ft3/s Results Discharge 0.93 W/s Normal Depth 0.67 ft Flow Area 0.35 ft2 -- Wetted Perimeter 2.09 It Hydraulic Radius 0.17 ft Top Width 0.00 ft - Critical Depth 0.46 It Percent Full 100.0 % Critical Slope 0.00757 ft/ft Velocity 2.65 f/s Velocity Head 0.11 ft Specific Energy 0.78 ft Froude Number 0.00 Maximum Discharge 1.00 ft'/s Discharge Full 0.93 ft'/s Slope Full 0.00500 ft/ft Flow Type SubCritical GVF Input Data Downstream Depth 000 ft Length 0-00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0.00 ft Profile Description Profile Headloss 0.00 ft Average End Depth Over Rise 0.00 Bentley Systems,Inc. Haestad Methods Sol&&Wdl e�Master V8i(SELECTseries 1) 108-11.01.031 5111/2011 1:49:16 PM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Page 1 of 2 Worksheet for 9 Basin G GVF Output Data Normal Depth Over Rise 10000 % Downstream Velocity Infinity ft/s Upstream Velocity Infinity fUs Normal Depth 067 ft Critical Depth 0.46 It Channel Slope 0,00500 ft/ft Critical Slope 000757 ft/ft Messages Notes 100 Yr Flow Rate Basin G =0.55CFS Bentley Systems,Inc. Haestad Methods Solt "djeFEenMaster V8i(SELECTseries 1) [08-11.01.031 5/11/2011 1:49:16 PM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1_203-755-1666 Page 2 of 2 Worksheet for 10 Basin J Project Description Friction Method Manning Formula Solve For Full Flow Capacity Input Data Roughness Coefficient 0.010 Channel Slope 0.00500 ft/ft Normal Depth 0.67 ft Diameter 0-67 ft Discharge 1.11 ft'/s Results Discharge 1.11 ft'/s Normal Depth 0.67 ft Flow Area 0.35 ft' Wetted Perimeter 2.09 ft Hydraulic Radius 0.17 ft Top Width 000 ft Critical Depth 0.50 ft Percent Full 1000 Critical Slope 0.00601 ft/ft Velocity 3.18 ft/s Velocity Head 0.16 ft Specific Energy 0-82 ft Froude Number 0.00 Maximum Discharge 1.20 ft'/s Discharge Full 1.11 ft'/s Slope Full 000500 ft/ft Flow Type SubCritical GVF Input Data Downstream Depth 0.00 ft Length 0.00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0.00 ft Profile Description Profile Headloss 0.00 ft Average End Depth Over Rise 0.00 Bentley Systems,Inc_ Haestad Methods SolfibimllEQeFitewMaster V8i(SELECTseries 1) [08.11.01.031 5/6/2011 5:10:05 PM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1_203-755-1666 Page 1 of 2 Worksheet for 10 Basin J GVF Output Data Normal Depth Over Rise 100.00 % Downstream Velocity Infinity ft/s Upstream Velocity Infinity ft/s Normal Depth 0.67 ft Critical Depth 0-50 ft Channel Slope 0.00500 ft/ft Critical Slope 0.00601 ft/ft Messages Notes 100 Yr Flow Rate From Basin G=0.55CFS 100 Yr Flow Rate From Basin J=0.09CFS Total Flow Rate=0-64CFS Bentley Systems,Inc- Haestad Methods Solib"4-FibmMaster V8i(SELECTsenes 1) [08.11.01.031 5/6/2011 5:10:05 PM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Page 2 of 2 Worksheet for 11 Basin N Project Description Friction Method Manning Formula Solve For Full Flow Capacity Input Data Roughness Coefficient 0-012 Channel Slope 0.00500 fUft Normal Depth 0.67 ft Diameter 0.67 ft Discharge 0.93 fP/s Results Discharge 0.93 ft'/s Normal Depth 0-67 ft Flow Area 035 ft' Wetted Perimeter 2.09 ft Hydraulic Radius 0.17 ft Top Width 0-00 ft Critical Depth 0.46 ft Percent Full 100.0 % Critical Slope 0.00757 ft/ft Velocity 2.65 ft/s Velocity Head 0.11 It Specific Energy 0,78 ft Froude Number 0.00 Maximum Discharge 1.00 ft'/s Discharge Full 0.93 ft'/s Slope Full 0-00500 ft/ft Flow Type SubCnticat GVF Input Data Downstream Depth 0-00 ft Length 0.00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0.00 ft Profile Description Profile Headloss 0.00 ft Average End Depth Over Rise 0.00 % Bentley Systems,Inc. Haestad Methods SoIGW"E}efitewMaster V8i(SELECTseries 1) [08.11.01.03) 5/11/2011 1.51:10 PM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Page 1 of 2 Worksheet for 11 Basin N GVF Output Data Normal Depth Over Rise 100.00 % Downstream Velocity Infinity ft/s Upstream Velocity Infinity fUs Normal Depth 0.67 ft Critical Depth 0.46 ft Channel Slope 0.00500 ft/ft Critical Slope 0.00757 ft/ft Messages Notes 100 YR Flow Rate Basin N=0 55CFS Bentley Systems,Inc. Haestad Methods Solm' I dl efileivMaster V8i(SELECTseries 1) [08.11.01.03] 5/11/2011 1:51:10 PM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Page 2 of 2 Worksheet for 11-A Basin N Project Description Friction Method Manning Formula Solve For Full Flow Capacity Input Data Roughness Coefficient 0.010 Channel Slope 0.00500 ft/ft Normal Depth 067 ft Diameter 0.67 ft Discharge 1.11 ft�/s Results Discharge 1.11 fY/s Normal Depth 0.67 ft Flow Area 0.35 ft2 Wetted Perimeter 209 ft Hydraulic Radius 0.17 ft Top Width 0.00 ft Critical Depth 0.50 ft Percent Full 100.0 % Critical Slope 0.00601 ft/ft Velocity 3.18 ft/s Velocity Head 016 ft Specific Energy 0.82 ft Froude Number 0.00 Maximum Discharge 1.20 ft'/s Discharge Full 1.11 ft'/s Slope Full 0.00500 fUft Flow Type SubCritical GVF Input Data Downstream Depth 0.00 ft Length 0.00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0-00 ft Profile Description Profile Headloss 0.00 ft Average End Depth Over Rise 0.00 % Bentley Systems,Inc. Haestad Methods SolAemlld7efikewMaster V8i(SELECTseries 1) 108.11.01.031 6/7/2011 10.24:49 AM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Page 1 of 2 Worksheet for 11-A Basin N GVF Output Data Normal Depth Over Rise 100.00 Downstream Velocity Infinity f/s Upstream Velocity Infinity ft/s Normal Depth 0-67 it Critical Depth 0.50 It Channel Slope 0.00500 ft/ft Critical Slope 0-00601 ft/ft Messages Notes 100 YR Flow Rate Basin N=0.55CFS Bentley Systems,Inc. Haestad Methods Sol®emklgefibawMaster V8i(SELECTseries 1) 108A1.01.031 6/7/2011 10.24:49 AM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Page 2 of 2 Worksheet for 12 Basin L Project Description Friction Method Manning Formula Solve For Full Flow Capacity Input Data Roughness Coefficient 0.010 Channel Slope 001400 ft/ft Normal Depth 1 50 ft Diameter 1 50 ft Discharge 16.16 fP/s Results Discharge 16-16 ft'/s Normal Depth 1.50 ft Flow Area 1.77 ft' Wetted Perimeter 4.71 ft Hydraulic Radius 038 ft Top Width 0-00 ft Critical Depth 1.43 ft Percent Full 100.0 % Critical Slope 0.01213 ft/ft Velocity 9.14 ft/s Velocity Head 1.30 ft Specific Energy 2-80 ft Froude Number 0.00 Maximum Discharge 17.38 W/s Discharge Full 16.16 ft'!s Slope Full 0.01400 ft/ft Flow Type SubCritical GVF Input Data Downstream Depth 0.00 ft Length 0.00 It Number Of Steps 0 GVF Output Data Upstream Depth 0.00 ft Profile Description Profile Headloss 0.00 ft Average End Depth Over Rise 0.00 Bentley Systems,Inc. Haestad Methods Sol R VSi(SEIECTseries 1) (08.11.01.031 5/11/2011 11-52:13 PM 27 Stemons Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Page 1 of 2 Worksheet for 12 Basin L GVF Output Data Normal Depth Over Rise 100.00 % Downstream Velocity Infinity fVs Upstream Velocity Infinity ft/s Normal Depth 1.50 ft Critical Depth 1.43 ft Channel Slope 0.01400 fL/ft Critical Slope 0.01213 ft/ft Messages Notes 100 YR Flow Rate Basin N=0.55CFS 100 YR Flow Rate Basin M=O.00FS 100 YR Flow Rate Basin L=0.07CFS Total Flow Rate=0.62CFS Bentley Systems,Inc Haestad Methods So[06ME}eFil3ewMaster V8i(SELECTseries 1) 108.11.01.031 5/11/2011 1:52:13 PM 27 Siemons Company Drive Suite 200 W Watertown,CT 06795 USA +1-203-755-1666 Page 2 of 2 Flow Frequency Analysis Time Series File:devlac.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- FlowRate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.624 6 8/27/01 18:00 1 .29 1 100.00 0.990 0.419 8 9/17/02 16:15 1 .08 2 25.00 0.960 1.08 2 12/08/02 17:15 0.728 3 10.00 0.900 0.447 7 8/23/04 14:30 0.650 4 5.00 0.800 0.626 5 10/28/04 16:00 0.626 5 3.00 0.667 0.650 4 10/22/05 10:00 0.624 6 2.00 0.500 0.728 3 10/25/06 22:45 0.447 7 1 .30 0.231 1.29 i 1/09/08 6:30 0.419 8 1 . 10 0.091 Computed Peaks 1 .22 50.00 0.980 Example Calculations For Conveyance: 100%of the 100 year peak flow rate • Contributing area (Basin C) = 8,326 SF • 100 Year Peak Flow Rote = 129 CFS/ 1 Acre of impervious surface 8,326 5F " (I ACRE/n3650SO = 0.191 ACRES 0.191 ACRES " (129 CII/,ACRE-pe--) = 0.25 CFS • Minimum Pipe Capacity = 0.25 CFS Appendix B: Americast Filterra Documentation Matt Jones Magnusson Klemencic Associates 1301 Fifth Avenue, Suite 3200 ffa Seattle,WA 98101 2699 flo lie Bioretention Systems June 10, 2011 Plan Review of Filterra° Boeing - Building 04-68-75, City of Renton, WA Dear Sirs Thank you for submitting the revised plans on 09 June 2011 for our review of the subject project. Filterra structures 19 (FTS-CI 8x6-2) and 20 (FTS-CI 8x4-2)were studied for; • Planned Filterra®box sized according to Washington DOE WWHM modeling • Filterra® invert elevations are higher than effluent invert elevations • The maximum treatment flow does not exceed our internal weir allowance • The Filterra® outlet drain pipe is sized according to plans • For any conflicting structures such as storm drain pipes below Filterra® • For most efficient placement of Filterra®units The plan review concluded that the Filterra®structures listed above were sited and sized appropriately to treat stormwater to our published specifications and in compliance with Washington Department of Ecology's WWHM modeling; meeting the 91% filtered threshold for Basic Treatment. Operational consistency with these specifications is contingent upon the stormwater units being installed correctly and according to the plans, as well as regular maintenance being performed. Installation Help documents will be forwarded to the Buyer at time of order. The Filterra Operation and Maintenance Manual will be made available upon request. Yours sincerely -55 .�iu Dean Baddorf Engineer Support Manager Filterra® Bioretention Systems Manufactured by Americast T:(804)752-1454 A4MERICAST 11352 Virginia Precast Road F:(804)798-8400 not just concrete.concrete solutions. Ashland,VA 23005 E:dbaddorf@filterra.com www.filterra.com 1 1'-0" 8'-0" 20" TREATMENT CHAMBER F"I I r---------1 ---------r BYPASS CHAMBER A CONDUIT i OOOQ��OQo�IN ----- � — — —————— O a------ —±— --------T11 io p00000a000�ooa �� - --- �, �o0�a�D%gmi L--————————————————— I I I I TOP FACE FLOW FLOW OF CURB PLAN VIEW PLANT AS SUPPLIED BY AMERICAST (NOT SHOWN FOR CLARITY) ENERGY DISSIPATION LAYER TREE FRAME & GRATE TRENCH FRAME & GRATE CAST IN TOP SLAB CAST IN TOP SLAB TOP SLAB ao FILTERRA FLOW .. " .; .:. CONTROL WEIR a' (PATENT PENDING) ' % ', - OUTLET PIPE—LOCATION 00 VARIES (BY OTHERS) Z w -- UNDERDRAIN STONE PROVIDED BY AMERICAST MULCH PROVIDED BY AMERICAST FILTER TAPE/TARP APPROVED MEDIA PROVIDED BY AMERICAST SECTION A—A UNIT TO BE SET PLUMB AND LEVEL DATE: 04-18-11 DWG: FTS—CI 8x4-2R Q Q91Nff8Qwy8 S'x4' PRECAST FILTERRASUMP CURB INLET UNIT l� WITH 2' BYPASS CHAMBER US PAT 6,277,274 Copyright C'�2U07 by Americast AND 6,569,321 11'-0" 20' 8'—O" TREATMENT F CHAMBER Irr----------u ------- I II I BYPASS I I CHAMBER v QOa�aDO�o 2" PVC , A I �O�OOO DDO�O ( CONDUIT o A -- - T------- ---- a --- ` L - - +------- ---- --- r ��0°0000oo°ooQ I I �- L -------------------J I_ I I I I f TOP FACE FLOW FLOW OF CURB PLAN VIEW PLANT AS SUPPLIED BY AMERICAST (NOT SHOWN FOR CLARITY) TRENCH FRAME & GRATE ENERGY CAST IN TOP SLAB DISSIPATION TREE FRAME & GRATE LAYER CAST IN TOP SLAB FILTERRA FLOW CONTROL WEIR • ... (PATENT PENDING) ��. a- OUTLET PIPE-LOCATION o 1� (o VARIES (BY OTHERS) i o I ... 4 ;•. UNDERDRAIN STONE PROVIDED BY AMERICAST FILTER TAPE/TARP APPROVED MEDIA MULCH PROVIDED BY AMERICAST PROVIDED BY AMERICAST SECTION A-A UNIT TO BE SET PLUMB AND LEVEL DATE: 04-18-11 DWG: FTS-CI 8x6-2L Q 8'x6' PRECAST FILTERRA Ll`%IJLSUU LrL�J SUMP CURB INLET UNIT l� Copyright lC2007byAmericast WITH 2' BYPASS CHAMBER US PAT 6,277,274 AND 6,569,321 Facility Name ISand Finer-Basin A Outlet 1 Outlet 2 Outlet 3 Downstream Connections 10 0 Facility Type ISand Filter f- Precipitation Applied to Facility Quick Filter if Evaporation Applied to Facility Facility Bottom Elevation(ft) 10 Facility Dimensions Bottom Length 0 Outlet Structure Bottom Width Riser Height(it) 0.75 Effective Depth Riser Diameter(in) 100 1.25 Riser Type Flat J Left Side Slope0 Bottom Side Slope Typepe p� Right Side Slope p� Top Side Slope 0 Infiltration (YES Orifice Diameter Height QMax Hydraulic Conductivity(in/hr) 24.82 Number (In) (Ft) (cfs) Filter material depth(fi) 1.8 2 r--r--1 0 Total Volume Filtrated(acre-ft) 42.356 3 F0 �ro---J 0 Total Volume Through Riser(acre-ft) 2.393 Total Volume(acre-It) 44.748 Filter Storage Volume at Riser Head ,.1001 Percent Filtered 94.65 Pond Increment Show Pond Table i0p�ble -J Western Washington Hydrology Model PROJECT REPORT Project Name: BasinA Site Address: City Renton Report Date 6/6/2011 Gage Seatac Data Start 1948/10/01 Data End 1998/09/30 Precip Scale: 1.00 WWHM3 Version: PREDEVELOPED LAND USE Name Basin A Bypass: No Groundwater: No Pervious Land Use Acres Impervious Land Use Acres PARKING FLAT 0.355 Element Flows To: Surface Interflow Groundwater Name Sand Filter - Basin A Bottom Length: 8ft. Bottom Width : 6ft. Depth : 1.25ft. Side slope 1: 0 To 1 Side slope 2: 0 To 1 Side slope 3: 0 To 1 Side slope 4: 0 To 1 Filtration On Hydraulic conductivity 24.82 Depth of filter medium 1.8 Discharge Structure Riser Height: 0.75 ft. Riser Diameter: 100 in. Element Flows To: Outlet 1 Outlet 2 Sand Filter Hydraulic Table Stage(ft) Area(acr) Volume(acr-ft) Dschrg(cfs) Infilt(cfe) 0.000 0.001 0.000 0.000 0.000 0.014 0.001 0.000 0.000 0.000 0.028 0.001 0.000 0.000 0.000 0.042 0.001 0.000 0.000 0.000 0.056 0.001 0.000 0.000 0.000 0.069 0.001 0.000 0.000 0.000 0.083 0.001 0.000 0.000 0.000 0.097 0.001 0.000 0.000 0.000 0.111 0.001 0.000 0.000 0.000 0.125 0.001 0.000 0.000 0.000 0.139 0.001 0.000 0.000 0.000 0.153 0.001 0.000 0.000 0.000 0.167 0.001 0.000 0.000 0.000 0.181 0.001 0.000 0.000 0.000 0.194 0.001 0.000 0.000 0.000 0.208 0.001 0.000 0.000 0.000 0.222 0.001 0.000 0.000 0.000 0.236 0.001 0.000 0.000 0.000 0.250 0.001 0.000 0.000 0.000 0.264 0.001 0.000 0.000 0.000 0.278 0.001 0.000 0.000 0.000 0.292 0.001 0.000 0.000 0.000 0.306 0.001 0.000 0.000 0.000 0.319 0.001 0.000 0.000 0.000 0.333 0.001 0.000 0.000 0.000 0.347 0.001 0.000 0.000 0.000 0.361 0.001 0.000 0.000 0.000 0.375 0.001 0.000 0.000 0.000 0.389 0.001 0.000 0.000 0.000 0.403 0.001 0.000 0.000 0.000 0.417 0.001 0.000 0.000 0.000 0.431 0.001 0.000 0.000 0.000 0.444 0.001 0.000 0.000 0.000 0.458 0.001 0.001 0.000 0.000 0.472 0.001 0.001 0.000 0.000 0.486 0.001 0.001 0.000 0.000 0.500 0.001 0.001 0.000 0.000 0.514 0.001 0.001 0.000 0.000 0.528 0.001 0.001 0.000 0.000 j 0.542 0.001 0.001 0.000 0.000 0.556 0.001 0.001 0.000 0.000 0.569 0.001 0.001 0.000 0.000 0.583 0.001 0.001 0.000 0.000 0.597 0.001 0.001 0.000 0.000 0.611 0.001 0.001 0.000 0.000 0.625 0.001 0.001 0.000 0.000 0.639 0.001 0.001 0.000 0.000 0.653 0.001 0.001 0.000 0.000 0.667 0.001 0.001 0.000 0.000 0.681 0.001 0.001 0.000 0.000 0.694 0.001 0.001 0.000 0.000 0.708 0.001 0.001 0.000 0.000 0.722 0.001 0.001 0.000 0.000 0.736 0.001 0.001 0.000 0.000 0.750 0.001 0.001 0.000 0.000 0.764 0.001 0.001 0.133 0.000 0.778 0.001 0.001 0.376 0.000 0.792 0.001 0.001 0.690 0.000 0.806 0.001 0.001 1.063 0.000 0.819 0.001 0.001 1.485 0.000 0.833 0.001 0.001 1.952 0.000 0.847 0.001 0.001 2.460 0.000 - 0.861 0.001 0.001 3.006 0.000 0.875 0.001 0.001 3.587 0.000 0.889 0.001 0.001 4.201 0.000 0.903 0.001 0.001 4.846 0.000 0.917 0.001 0.001 5.522 0.000 0.931 0.001 0.001 6.227 0.000 0.944 0.001 0.001 6.959 0.000 0.958 0.001 0.001 7.717 0.000 0.972 0.001 0.001 8.502 0.000 0.986 0.001 0.001 9.311 0.000 1.000 0.001 0.001 10.14 0.000 1.014 0.001 0.001 11.00 0.000 1.028 0.001 0.001 11.88 0.000 1.042 0.001 0.001 12.78 0.000 1.056 0.001 0.001 13.71 0.000 1.069 0.001 0.001 14.65 0.000 1.083 0.001 0.001 15.62 0.000 1.097 0.001 0.001 16.61 0.000 1.111 0.001 0.001 17.61 0.000 1.125 0.001 0.001 18.64 0.000 1.139 0.001 0.001 19.68 0.000 1.153 0.001 0.001 20.75 0.000 1.167 0.001 0.001 21.83 0.000 1.181 0.001 0.001 22.93 0.000 1.194 0.001 0.001 24.05 0.000 1.208 0.001 0.001 25.18 0.000 1.222 0.001 0.001 26.34 0.000 1.236 0.001 0.001 27.51 0.000 1.250 0.001 0.001 28.69 0.000 1.264 0.001 0.001 29.90 0.000 Name Basin A Bypass: No GroundWater: No Pervious Land Use Acres C, Lawn, Flat .012 Impervious Land Use Acres ROADS FLAT 0.064 SIDEWALKS FLAT 0.01 PARKING FLAT 0.269 Element Flows To: Surface Interflow Groundwater Sand Filter - Basin A, Sand Filter - Basin A, MITIGATED LAND USE ANALYSIS RESULTS Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.095929 5 year 0.122702 10 year 0.14069 25 year 0.163813 50 year 0.181367 100 year 0.199227 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.046643 5 year 0.065877 10 year 0.079211 25 year 0.096699 50 year 0.110176 100 year 0.12403 Yearly Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1950 0.099 0.049 1951 0.154 0.089 1952 0.095 0.046 1953 0.083 0.038 1954 0.071 0.028 1955 0.090 0.043 1956 0.099 0.049 1957 0.094 0.046 1958 0.109 0.056 1959 0.098 0.048 1960 0.069 0.028 1961 0.092 0.044 1962 0.076 0.034 1963 0.080 0.034 1964 0.081 0.040 1965 0.094 0.046 1966 0.082 0.037 1967 0.081 0.036 1968 0.135 0.073 1969 0.156 0.088 1970 0.070 0.029 1971 0.081 0.036 1972 0.078 0.034 1973 0.122 0.066 1974 0.071 0.030 1975 0.087 0.046 1976 0.114 0.058 1977 0.071 0.029 1978 0.099 0.049 1979 0.139 0.079 1980 0.141 0.083 1981 0.105 0.052 1982 0.121 0.064 1983 0.174 0.102 1984 0.122 0.065 1985 0.084 0.037 1986 0.079 0.034 1987 0.102 0.052 1988 0.159 0.091 1989 0.063 0.024 1990 0.092 0.049 1991 0.174 0.103 1992 0.162 0.094 1993 0.085 0.039 1994 0.053 0.020 1995 0.064 0.022 1996 0.088 0.041 1997 0.105 0.054 1998 0.102 0.051 1999 0.117 0.065 Ranked Yearly Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.1742 0.1027 2 0.1738 0.1023 3 0.1617 0.0939 4 0.1594 0.0908 5 0.1555 0.0890 6 0.1540 0.0879 7 0.1405 0.0826 8 0.1391 0.0793 9 0.1349 0.0729 10 0.1225 0.0655 11 0.1223 0.0651 12 0.1210 0.0646 13 0.1167 0.0645 14 0.1144 0.0582 15 0.1094 0.0555 16 0.1054 0.0541 17 0.1050 0.0520 18 0.1024 0.0518 19 0.1017 0.0512 20 0.0992 0.0490 21 0.0988 0.0488 22 0.0986 0.0487 23 0.0979 0.0487 24 0.0946 0.0481 25 0.0944 0.0463 26 0.0943 0.0458 27 0.0923 0.0458 28 0.0920 0.0455 29 0.0904 0.0442 30 0.0881 0.0429 31 0.0872 0.0411 32 0.0846 0.0396 33 0.0839 0.0388 34 0.0833 0.0376 35 0.0819 0.0369 36 0.0808 0.0368 37 0.0808 0.0362 38 0.0806 0.0362 39 0.0797 0.0340 40 0.0790 0.0339 41 0.0775 0.0337 42 0.0764 0.0337 43 0.0715 0.0296 44 0.0709 0.0295 45 0.0708 0.0292 46 0.0701 0.0278 47 0.0691 0.0277 48 0.0641 0.0241 49 0.0632 0.0221 50 0.0535 0.0202 POC #1 The Facility PASSED The Facility PASSED. Flow(CFS) Predev Dev Percentage Pass/Fail 0.0480 653 67 10 Pass 0.0493 614 60 9 Pass 0.0507 569 56 9 Pass 0.0520 527 49 9 Pass 0.0534 497 45 9 Pass 0.0547 465 42 9 Pass 0.0560 434 38 8 Pass 0.0574 413 35 8 Pass 0.0587 383 32 8 Pass 0.0601 352 31 8 Pass 0.0614 331 30 9 Pass 0.0628 308 28 9 Pass 0.0641 284 27 9 Pass 0.0655 269 22 8 Pass 0.0668 253 20 7 Pass 0.0682 240 19 7 Pass 0.0695 218 18 8 Pass 0.0709 205 18 8 Pass 0.0722 195 16 8 Pass 0.0736 179 15 8 Pass 0.0749 168 14 8 Pass 0.0763 155 13 8 Pass 0.0776 147 13 8 Pass 0.0790 138 12 8 Pass 0.0803 132 11 8 Pass 0.0817 121 11 9 Pass 0.0830 112 10 8 Pass 0.0843 105 10 9 Pass 0.0857 100 8 8 Pass 0.0870 94 8 8 Pass 0.0884 90 7 7 Pass - 0.0897 85 4 4 Pass 0.0911 81 3 3 Pass 0.0924 75 3 4 Pass 0.0938 69 3 4 Pass 0.0951 65 2 3 Pass 0.0965 62 2 3 Pass 0.0978 57 2 3 Pass 0.0992 52 2 3 Pass 0.1005 51 2 3 Pass 0.1019 46 2 4 Pass 0.1032 42 0 0 Pass 0.1046 41 0 0 Pass 0.1059 38 0 0 Pass 0.1073 34 0 0 Pass 0.1086 34 0 0 Pass 0.1099 33 0 0 Pass 0.1113 31 0 0 Pass 0.1126 29 0 0 Pass 0.1140 29 0 0 Pass 0.1153 28 0 0 Pass 0.1167 28 0 0 Pass 0.1180 26 0 0 Pass 0.1194 24 0 0 Pass 0.1207 24 0 0 Pass 0.1221 22 0 0 Pass 0.1234 19 0 0 Pass 0.1248 19 0 0 Pass 0.1261 19 0 0 Pass 0.1275 18 0 0 Pass 0.1288 18 0 0 Pass 0.1302 18 0 0 Pass 0.1315 17 0 0 Pass 0.1329 17 0 0 Pass 0.1342 14 0 0 Pass 0.1356 13 0 0 Pass 0.1369 12 0 0 Pass 0.1382 12 0 0 Pass 0.1396 11 0 0 Pass 0.1409 10 0 0 Pass 0.1423 10 0 0 Pass 0.1436 10 0 0 Pass 0.1450 10 0 0 Pass 0.1463 10 0 0 Pass 0.1477 10 0 0 Pass 0.1490 9 0 0 Pass 0.1504 9 0 0 Pass 0.1517 8 0 0 Pass 0.1531 8 0 0 Pass 0.1544 7 0 0 Pass 0.1558 5 0 0 Pass 0.1571 4 0 0 Pass 0.1585 4 0 0 Pass 0.1598 3 0 0 Pass 0.1612 3 0 0 Pass 0.1625 2 0 0 Pass 0.1638 2 0 0 Pass 0.1652 2 0 0 Pass 0.1665 2 0 0 Pass 0.1679 2 0 0 Pass 0.1692 2 0 0 Pass 0.1706 2 0 0 Pass 0.1719 2 0 0 Pass 0.1733 2 0 0 Pass 0.1746 0 0 0 Pass 0.1760 0 0 0 Pass 0.1773 0 0 0 Pass 0.1787 0 0 0 Pass 0.1800 0 0 0 Pass 0.1814 0 0 0 Pass Water Quality SMP Flow and Volume for POC 1. On-line facility volume: 0.0283 acre-feet On-line facility target flow: 0.01 cfs. Adjusted for 15 min: 0.0644 cfs. Off-line facility target flow: 0.0343 cfs. Adjusted for 15 min: 0.0386 cfa. Perind and Impind Changes No changes have been made. This program and accompanying documentation is provided 'as-is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by the user. Clear Creek Solutions and the Washington State Department of Ecology disclaims all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions and/or the Washington State Department of Ecology be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions or the Washington State Department of Ecology has been advised of the possibility of such damages. Sand Filter I Mitigated Facility Name ISand Filter-Basin BI Outlet 1 Outlet 2 Outlet 3 Downstream Connections 0 0 0 Facility Type Sand Filter Precipitation Applied to Facility Quick Filter Evaporation Applied to Facility Facility Bottom Elevation(ft) 10 Facility Dimensions Bottom Length ® Outlet Structure Bottom Width q Riser Height(ft) 075 Effective Depth 175 RiserDiameter(in) 106— J Riser Type Flat J Left Side Slope 0 Bottom Side Slope 0 Notch Type Right Side Slope 0 Top Side Slope 0 Infiltration YES Orifice Diameter Height OMax Hydraulic Conductivity(in/hr) 24.62 Number (In) (Ft) (cis) 1 A Ji0 _ 0 Filter material depth(ft) 1.8 J 2 F0-. 4 i -_ ) 0 Total Volume Filtrated(acre-It1 29.305 3 ,r0 --J 0 J 0 Total Volume ThroughRiser(acre ft) 1.528 Total Volume(acre it) 29.833 Filter Storage Volume at Riser Head .001 Percent Filtered 94.88 Pond Increment 0.10 J Show Pond Table jOpen Table J Western Washington Hydrology Model PROJECT REPORT Project Name: Boeing Site Address: City Renton Report Date 6/6/2011 Gage Seatac Data Start 1948/10/01 Data End 1998/09/30 Precip Scale: 1.00 WWHM3 Version: PREDEVELOPED LAND USE Name Basin B Bypass: No GroundWater: No Pervious Land Use Acres Impervious Land Use Acres PARKING FLAT 0.246 Element Flows To: Surface Interflow Groundwater Name Sand Filter - Basin B Bottom Length: 8ft. Bottom Width : 4ft. Depth : 1.25ft. Side slope 1: 0 To 1 Side slope 2: 0 To 1 Side slope 3: 0 To 1 Side slope 4: 0 To 1 Filtration On Hydraulic conductivity 24.82 Depth of filter medium 1.8 Discharge Structure Riser Height: 0.75 ft. Riser Diameter: 100 in. Element Flows To: Outlet 1 Outlet 2 Sand Filter Hydraulic Table Stage(ft) Area(acr) Volume(acr-ft) Dschrg(cfs) Infilt(cfs) 0.000 0.001 0.000 0.000 0.000 0.014 0.001 0.000 0.000 0.000 0.028 0.001 0.000 0.000 0.000 0.042 0.001 0.000 0.000 0.000 0.056 0.001 0.000 0.000 0.000 - 0.069 0.001 0.000 0.000 0.000 0.083 0.001 0.000 0.000 0.000 0.097 0.001 0.000 0.000 0.000 0.111 0.001 0.000 0.000 0.000 0.125 0.001 0.000 0.000 0.000 0.139 0.001 0.000 0.000 0.000 0.153 0.001 0.000 0.000 0.000 0.167 0.001 0.000 0.000 0.000 0.181 0.001 0.000 0.000 0.000 0.194 0.001 0.000 0.000 0.000 0.208 0.001 0.000 0.000 0.000 0.222 0.001 0.000 0.000 0.000 0.236 0.001 0.000 0.000 0.000 0.250 0.001 0.000 0.000 0.000 0.264 0.001 0.000 0.000 0.000 0.278 0.001 0.000 0.000 0.000 0.292 0.001 0.000 0.000 0.000 0.306 0.001 0.000 0.000 0.000 0.319 0.001 0.000 0.000 0.000 0.333 0.001 0.000 0.000 0.000 0.347 0.001 0.000 0.000 0.000 0.361 0.001 0.000 0.000 0.000 0.375 0.001 0.000 0.000 0.000 0.389 0.001 0.000 0.000 0.000 0.403 0.001 0.000 0.000 0.000 0.417 0.001 0.000 0.000 0.000 0.431 0.001 0.000 0.000 0.000 0.444 0.001 0.000 0.000 0.000 0.458 0.001 0.000 0.000 0.000 0.472 0.001 0.000 0.000 0.000 0.486 0.001 0.000 0.000 0.000 0.500 0.001 0.000 0.000 0.000 0.514 0.001 0.000 0.000 0.000 0.528 0.001 0.000 0.000 0.000 0.542 0.001 0.000 0.000 0.000 0.556 0.001 0.000 0.000 0.000 0.569 0.001 0.000 0.000 0.000 0.583 0.001 0.000 0.000 0.000 0.597 0.001 0.000 0.000 0.000 0.611 0.001 0.000 0.000 0.000 0.625 0.001 0.000 0.000 0.000 0.639 0.001 0.000 0.000 0.000 0.653 0.001 0.000 0.000 0.000 0.667 0.001 0.000 0.000 0.000 0.681 0.001 0.000 0.000 0.000 0.694 0.001 0.001 0.000 0.000 0.708 0.001 0.001 0.000 0.000 0.722 0.001 0.001 0.000 0.000 0.736 0.001 0.001 0.000 0.000 0.750 0.001 0.001 0.000 0.000 0.764 0.001 0.001 0.133 0.000 0.778 0.001 0.001 0.376 0.000 0.792 0.001 0.001 0.690 0.000 0.806 0.001 0.001 1.063 0.000 0.819 0.001 0.001 1.485 0.000 0.833 0.001 0.001 1.952 0.000 0.847 0.001 0.001 2.460 0.000 0.861 0.001 0.001 3.006 0.000 0.875 0.001 0.001 3.587 0.000 0.889 0.001 0.001 4.201 0.000 0.903 0.001 0.001 4.846 0.000 0.917 0.001 0.001 5.522 0.000 0.931 0.001 0.001 6.227 0.000 0.944 0.001 0.001 6.959 0.000 0.958 0.001 0.001 7.717 0.000 0.972 0.001 0.001 8.502 0.000 0.986 0.001 0.001 9.311 0.000 1.000 0.001 0.001 10.14 0.000 1.014 0.001 0.001 11.00 0.000 1.028 0.001 0.001 11.88 0.000 1.042 0.001 0.001 12.78 0.000 1.056 0.001 0.001 13.71 0.000 1.069 0.001 0.001 14.65 0.000 1.083 0.001 0.001 15.62 0.000 1.097 0.001 0.001 16.61 0.000 1.111 0.001 0.001 17.61 0.000 1.125 0.001 0.001 18.64 0.000 1.139 0.001 0.001 19.68 0.000 1.153 0.001 0.001 20.75 0.000 1.167 0.001 0.001 21.83 0.000 1.181 0.001 0.001 22.93 0.000 1.194 0.001 0.001 24.05 0.000 1.208 0.001 0.001 25.18 0.000 1.222 0.001 0.001 26.34 0.000 1.236 0.001 0.001 27.51 0.000 1.250 0.001 0.001 28.69 0.000 1.264 0.001 0.001 29.90 0.000 Name Basin B Bypass: No GroundWater: No Pervious Land Use Acres C, Lawn, Flat .021 Impervious Land Use Acres ROADS FLAT 0.056 SIDEWALKS FLAT 0.013 PARKING FLAT 0.156 Element Flows To: Surface Interflow Groundwater Sand Filter - Basin B, Sand Filter - Basin B, MITIGATED LAND USE ANALYSIS RESULTS Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.095929 5 year 0.122702 10 year 0.14069 25 year 0.163813 50 year 0.181367 100 year 0.199227 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.030651 5 year 0.043656 10 year 0.052728 25 year 0.064682 50 year 0.073931 100 year 0.083467 Yearly Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1950 0.099 0.032 1951 0.154 0.060 1952 0.095 0.031 1953 0.083 0.024 1954 0.071 0.018 1955 0.090 0.028 1956 0.099 0.032 1957 0.094 0.030 1958 0.109 0.037 1959 0.098 0.032 1960 0.069 0.018 1961 0.092 0.029 1962 0.076 0.022 1963 0.080 0.022 1964 0.081 0.026 1965 0.094 0.030 1966 0.082 0.024 1967 0.081 0.024 1968 0.135 0.049 1969 0.156 0.058 1970 0.070 0.019 1971 0.081 0.023 1972 0.078 0.022 1973 0.122 0.044 1974 0.071 0.019 1975 0.087 0.030 1976 0.114 0.039 i 1977 0.071 0.019 -, 1978 0.099 0.032 1979 0.139 0.052 1980 0.141 0.054 1981 0.105 0.035 1982 0.121 0.043 1983 0.174 0.068 1984 0.122 0.043 1985 0.084 0.024 1986 0.079 0.022 1987 0.102 0.035 1988 0.159 0.059 1989 0.063 0.016 1990 0.092 0.032 1991 0.174 0.069 1992 0.162 0.063 1993 0.085 0.025 1994 0.053 0.013 1995 0.064 0.014 1996 0.088 0.026 1997 0.105 0.036 1998 0.102 0.034 1999 0.117 0.043 Ranked Yearly Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.1742 0.0693 2 0.1738 0.0680 3 0.1617 0.0631 4 0.1594 0.0601 5 0.1555 0.0591 6 0.1540 0.0580 7 0.1405 0.0541 8 0.1391 0.0520 9 0.1349 0.0490 10 0.1225 0.0436 11 0.1223 0.0429 12 0.1210 0.0427 13 0.1167 0.0426 14 0.1144 0.0388 15 0.1094 0.0370 16 0.1054 0.0365 17 0.1050 0.0347 18 0.1024 0.0346 19 0.1017 0.0342 20 0.0992 0.0322 21 0.0988 0.0318 22 0.0986 0.0318 23 0.0979 0.0317 24 0.0946 0.0317 25 0.0944 0.0311 26 0.0943 0.0304 27 0.0923 0.0303 28 0.0920 0.0300 29 0.0904 0.0294 30 0.0881 0.0284 I I 31 0.0872 0.0262 32 0.0846 0.0258 33 0.0839 0.0246 34 0.0833 0.0245 35 0.0819 0.0243 36 0.0808 0.0239 37 0.0808 0.0237 38 0.0806 0.0231 39 0.0797 0.0222 40 0.0790 0.0222 41 0.0775 0.0221 42 0.0764 0.0220 43 0.0715 0.0195 44 0.0709 0.0195 45 0.0708 0.0194 46 0.0701 0.0180 47 0.0691 0.0176 48 0.0641 0.0155 49 0.0632 0.0141 50 0.0535 0.0130 POC #1 The Facility PASSED The Facility PASSED. Flow(CFS) Predev Dev Percentage Pass/Fail 0.0480 653 16 2 Pass 0.0493 614 15 2 Pass 0.0507 569 14 2 Pass 0.0520 527 11 2 Pass 0.0534 497 11 2 Pass 0.0547 465 10 2 Pass 0.0560 434 9 2 Pass 0.0574 413 8 1 Pass 0.0587 383 7 1 Pass 0.0601 352 5 1 Pass 0.0614 331 3 0 Pass 0.0628 308 3 0 Pass 0.0641 284 2 0 Pass 0.0655 269 2 0 Pass 0.0668 253 2 0 Pass 0.0682 240 1 0 Pass 0.0695 218 0 0 Pass 0.0709 205 0 0 Pass 0.0722 195 0 0 Pass 0.0736 179 0 0 Pass 0.0749 168 0 0 Pass 0.0763 155 0 0 Pass 0.0776 147 0 0 Pass 0.0790 138 0 0 Pass 0.0803 132 0 0 Pass 0.0817 121 0 0 Pass 0.0830 112 0 0 Pass 0.0843 105 0 0 Pass 0.0857 100 0 0 Pass 0.0870 94 0 0 Pass 0.0884 90 0 0 Pass 0.0897 85 0 0 Pass 0.0911 81 0 0 Pass 0.0924 75 0 0 Pass 0.0938 69 0 0 Pass 0.0951 65 0 0 Pass 0.0965 62 0 0 Pass 0.0978 57 0 0 Pass 0.0992 52 0 0 Pass 0.1005 51 0 0 Pass 0.1019 46 0 0 Pass 0.1032 42 0 0 Pass 0.1046 41 0 0 Pass 0.1059 38 0 0 Pass 0.1073 34 0 0 Pass 0.1086 34 0 0 Pass 0.1099 33 0 0 Pass 0.1113 31 0 0 Pass 0.1126 29 0 0 Pass 0.1140 29 0 0 Pass 0.1153 28 0 0 Pass 0.1167 28 0 0 Pass 0.1180 26 0 0 Pass 0.1194 24 0 0 Pass 0.1207 24 0 0 Pass 0.1221 22 0 0 Pass 0.1234 19 0 0 Pass 0.1248 19 0 0 Pass 0.1261 19 0 0 Pass 0.1275 18 0 0 Pass 0.1288 18 0 0 Pass 0.1302 18 0 0 Pass 0.1315 17 0 0 Pass 0.1329 17 0 0 Pass 0.1342 14 0 0 Pass 0.1356 13 0 0 Pass 0.1369 12 0 0 Pass 0.1382 12 0 0 Pass 0.1396 11 0 0 Pass 0.1409 10 0 0 Pass 0.1423 10 0 0 Pass 0.1436 10 0 0 Pass 0.1450 10 0 0 Pass 0.1463 10 0 0 Pass 0.1477 10 0 0 Pass 0.1490 9 0 0 Pass 0.1504 9 0 0 Pass 0.1517 8 0 0 Pass 0.1531 8 0 0 Pass 0.1544 7 0 0 Pass 0.1558 5 0 0 Pass 0.1571 4 0 0 Pass 0.1585 4 0 0 Pass 0.1598 3 0 0 Pass 0.1612 3 0 0 Pass 0.1625 2 0 0 Pass 0.1638 2 0 0 Pass 0.1652 2 0 0 Pass '- 0.1665 2 0 0 Pass 0.1679 2 0 0 Pass 0.1692 2 0 0 Pass 0.1706 2 0 0 Pass 0.1719 2 0 0 Pass 0.1733 2 0 0 Pass 0.1746 0 0 0 Pass 0.1760 0 0 0 Pass 0.1773 0 0 0 Pass 0.1787 0 0 0 Pass 0.1800 0 0 0 Pass 0.1814 0 0 0 Pass Water Quality BMP Flow and Volume for POC 1. On-line facility volume: 0.0195 acre-feet On-line facility target flow: 0.01 cfs. Adjusted for 15 min: 0.0425 cfs. Off-line facility target flow: 0.023 cfa. Adjusted for 15 min: 0.0258 cfs. Perind and Impind Changes No changes have been made. This program and accompanying documentation is provided 'as-is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by the user. Clear Creek Solutions and the Washington State Department of Ecology disclaims all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions and/or the Washington State Department of Ecology be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions or the Washington State Department of Ecology has been advised of the possibility of such damages. 86.0� WA SH IN Ai ON Si AIF N EPAAi ME Ni OF E C O L O G Y November 2006 (Revised December, 2009) GENERAL USE LEVEL DESIGNATION FOR BASIC (TSS), ENHANCED, & OIL TREATMENT CONDITIONAL USE LEVEL DESIGNATION FOR PHOSPHORUS TREATMENT For Americast's Filterra® Ecolo 's Decision: Based on Americast's submissions, including the Final Technical Evaluation Report, dated December, 2009 and additional information provided to Ecology dated October 9, 2009, Ecology hereby issues the following use level designations: 1. A General Use Level Designation for Basic,Enhanced,and Oil Treatment. 2. A Conditional Use Level Designation for Phosphorus Treatment. The Conditional Use Level Designation expires on December 1,2011 unless extended by Ecology, and is subject to the conditions specified below. Ecolou's Conditions of Use: Filterra®units shall be designed,installed, and maintained to comply with these conditions: 1. Each Filterra®unit shall be sized for Basic and Oil Treatment using a filter hydraulic conductivity of 35.46 inches/hour (assuming a hydraulic gradient of 1.41 inch/inch as listed in the TER) using the sand filter module in the latest version of the Western Washington Hydrology Model (WWHM)or other Ecology-approved continuous runoff model. The model must indicate the unit is capable of processing 91 percent of the influent runoff file. The Filterra®unit is not appropriate for oil spill-control purposes. 2. Each Filterra®unit shall be sized for Enhanced Treatment using a filter hydraulic conductivity of 24.82 inches/hour (assuming a hydraulic gradient of 1.41 inch/inch as listed in the TER) using the sand filter module in the latest version of the WWHM or other Ecology-approved continuous runoff model. The model must indicate the unit is capable of processing 91 percent of the influent runoff file. 3. Each Filterra®unit shall be sized for Phosphorus Treatment using a filter hydraulic conductivity of 35.46 inches/hour (assuming a hydraulic gradient of 1.41 inch/inch as listed in the TER) using the sand filter module in the latest version of the WWHM or 1 other Ecology-approved continuous runoff model. The model must indicate the unit is capable of processing 91 percent of the influent runoff file. 4. Each site plan must undergo Filterra® review before the unit can be approved for site installation. This will ensure that site grading and slope are appropriate for use of a Filterra®unit. 5. Filterra® media shall conform to the specifications submitted to and approved by Ecology. 6. Maintenance includes removing trash, degraded mulch, and accumulated debris from the filter surface and replacing the mulch layer. Inspections will be used to determine the site-specific maintenance schedules and requirements. Maintenance procedures should follow those given in the most recent version of the Filterra®Installation, Operation, and Maintenance Manual. 7. Filterra© commits to submitting a QAPP by May 15, 2010 for Ecology review and approval of a new test site that meets the TAPE requirements for attaining a GULD for phosphorus treatment. The QAPP must be submitted for a minimum of one site where the unit is to be used for phosphorus treatment. 8. Filterra® shall submit a TER for Ecology review for phosphorus treatment by December 1,2011. 9. Filterra© units come in standard sizes. The minimum size filter surface-area is determined by using the sand filter module in the latest version of WWHM or other Ecology approved continuous runoff model. Model inputs include a. Filter media depth: 1.8 feet b. Effective Ponding Depth: 0.75 feet(This is equivalent to the 6-inch clear zone between the top of the mulch and the bottom of the slab plus 3 inches of mulch.) c. Side slopes: Vertical d. Riser height: 0.70 feet e. Filter Hydraulic Conductivity: Must be back-calculated assuming a target infiltration rate of 35 inches per hour (enhanced treatment) or 50 inches per hour (Basic,oil,or phosphorus treatment). Hydraulic conductivity in the WWHM includes the effective ponding depth as well as the filter media depth. 10. Filterra® may request Ecology to grant deadline or expiration date extensions,upon showing cause for such extensions. Lack of funds to complete the monitoring will not be viewed by Ecology as sufficient cause. 11. Discharges from the Filterra®units shall not cause or contribute to water quality standards violations in receiving waters. 2 Applicant: Americast Applicant's Address: 11352 Virginia Precast Road Ashland,VA,23005 Application Documents: • State of Washington Department of Ecology Application for Conditional Use Designation,Americast(September 2006) • Quality Assurance Project Plan Filterra®Bioretention Filtration System Performance Monitoring,Americast(April 2008) • Quality Assurance Project Plan Addendum Filterra®Bioretention Filtration System Performance Monitoring, Americast(June 2008) • Draft Technical Evaluation Report Filterra®Bioretention Filtration System Performance Monitoring,Americast(August 2009) • Final Technical Evaluation Report Filterra®Bioretention Filtration System Performance Monitoring,Americast(December 2009) • Technical Evaluation Report Appendices Filterra®Bioretention Filtration System Performance Monitoring, Americast,August 2009 Draft) • Memorandum to Department of Ecology Dated October 9,2009 from Americast, Inc. and Herrera Environmental Consultants Applicant's Use Level Request: General Level Use Designation for Basic, Enhanced,and Oil Treatment and Conditional Use Level Designation for Phosphorus Treatment. Applicant's Performance Claims: Field-testing and laboratory testing show that the Filterra®unit is promising as a stormwater m Ecology's performance goals for basic treatment best management practice and can meet g P gY P g enhanced and oil treatment and has the potential to meet Ecology's goal for phosphorus treatment. Findings of Fact: 1. Field-testing was completed at two sites at the Port of Tacoma. Continuous flow and rainfall data collected during the 2008-2009 monitoring period indicated that 89 storm events occurred. Water quality data was obtained from 27 storm events. Not all the sampled storms produced information that met TAPE criteria for storm and/or water quality data. 2. During the testing at the Port of Tacoma, 98.96 to 99.89 percent of the annual influent runoff volume passed through the POT and POT2 test systems respectively. Stormwater runoff bypassed the POT1 test system during nine storm events and bypassed the POT2 test system during one storm event. Bypass volumes ranged from 0.13%to 3 15.3%of the influent storm volume. Both test systems achieved the 91 percent water quality treatment-goal over the 1-year monitoring period. 3. Infiltration rates as high as 133 in/hr were observed during the various storms. No paired data that identified percent removal of TSS,metals,oil,or phosphorus at an instantaneous observed flow rate was provided. 4. The maximum storm average hydraulic loading rate associated with water quality data is <40 in/hr,with the majority of flow rates<25 in/hr. The average instantaneous hydraulic loading rate ranged from 8.6 to 53 inches per hour. 5. The field data showed a removal rate greater than 80% for TSS with an influent concentration greater than 20 mg/l at an average instantaneous hydraulic loading rate up to 53 in/hr(average influent concentration of 28.8 mg/1,average effluent concentration of 4.3 mg/1). 6. The field data showed a removal rate generally greater than 54% for dissolved zinc at an average instantaneous hydraulic loading rate up to 60 in/hr and an average influent concentration of 0.266 mg/1(average effluent concentration of 0.115 mg/1). 7. The field data showed a removal rate generally greater than 40% for dissolved copper at an average instantaneous hydraulic loading rate up to 35 in/hr and an average influent concentration of 0.0070 mg/1(average effluent concentration of 0.0036 mg/1). 8. The field data showed a average removal rate of 93% for total petroleum hydrocarbon (TPH)at an average instantaneous hydraulic loading rate up to 53 in/hr and an average influent concentration of 52 mg/l(average effluent concentration of 2.3 mg/1). The data also shows achievement of less than 15 mg/l TPH for grab samples. Limited visible sheen data was provided due to access limitations at the outlet monitoring location. 9. The field data showed low percentage removals of total Phosphorus at all storm flows at an average influent concentration of 0.189 mg/l(average effluent concentration of 0.171 mg/1). The relatively poor treatment performance of the Filterra® system at this location may be related to influent characteristics for total phosphorus that are unique to the Port of Tacoma site. It appears that the Filterra® system will not meet the 50 percent removal performance goal when the majority of phosphorus in the runoff is expected to be in the dissolved form. 10. Laboratory testing was performed on a scaled down version of the Filterra®unit. The lab data showed an average removal from 83-91% for TSS with influents ranging from 21 to 320 mg/L, 82-84% for total copper with influents ranging from 0.94 to 2.3 mg/L, and 50-61% for orthophosphate with influents ranging from 2.46 to 14.37 mg/L. 11. Permeability tests were conducted on the soil media. 12. Lab scale testing using Sil-Co-Sil 106 showed percent removals ranging from 70.1%to 95.5%with a median percent removal of 90.7%, for influent concentrations ranging from 8.3 to 260 mg/L. These laboratory tests were run at an infiltration rate of 50 in/hr. 4 13. Supplemental lab testing conducted in September 2009 using Sil-co-Sil 106 showed an average percent removal of 90.6%. These laboratory tests were run at infiltration rates ranging from 25 to 150 in/hr for influent concentrations ranging from 41.6 to 252.5 mg/l. Regression analysis results indicate that the Filterra system's TSS removal performance is independent of influent concentration in the concentration range evaluated at hydraulic loading rates of up to 150 in/hr. Remaining Issues or Concerns about the Filterra®Technology: Americast will provide additional mulch and media specifications for new installations and the facilities used for the TER by December 31, 2009. Once this information has been provided to Ecology,the General Use Level Designation will be finalized. Contact Information: Applicant: Larry Coffman Americast 301-580-6631 lcoffinan@filterra.com Applicant's Website: hqp://www.filterra.com Ecology web link: http://www.ecy.wa.gov/programs/wq/stormwater/newtech/index.htfnl Ecology: Douglas C. Howie, P.E. Water Quality Program, (360)407-6444, douglas.howie(&ecy.wa.gov 5 Operation & Maintenance (OM) Manual v01 f 10 [ te f fa I. Bioretention Systems A Growing Idea in Stormwater Filtration. A Division of: toAlrrMERICAST Filterra®Stormwater Bioretention Filtration System toll free: (866)349 3458 1 fax: (804)798 8400 1 maintenance(Vilterra.com filterra.com 0 fitterra Table of Contents Overview Filterrao'General Description Filterra` Schematic Basic Operations Design Maintenance Maintenance Overview Why Maintain? When to Maintain? Exclusion of Services Maintenance Visit Summary Maintenance Tools, Safety Equipment and Supplies Maintenance Visit Procedure Maintenance Checklist Resources Example Filterra Project Maintenance Report Sheet Example Filterra Structure Maintenance Report Sheet Filterra°Warranty Drawing FTST-2:Filterra Standard Configuration Detail Drawing FTNL-3:Filterra Narrow Length Configuration Detail Drawing FTNW-3: Filterra Narrow Width Configuration Detail 10/08/09 filterra.com toll free: (866) 349 3458 6) fitterfa General Description The following general specifications describe the general operations and maintenance requirements for the Americast stormwater bioretention filtration system, the Filterra° The system utilizes physical, chemical and biological mechanisms of a soil, plant and microbe complex to remove pollutants typically found in urban stormwater runoff. The treatment system is a fully equipped, pre-constructed drop-in place unit designed for applications in the urban landscape to treat contaminated runoff. Plant/oil/Mi f i Ire f f d Plant/Soil/Microbe Complex - Removes Pollutants,T55, Phosphorus,Nitrogen,Bacteria, Heavy Metals,Hydrocarbons,etc. New or Existing Hy,- Filterra Flow Line Catch Basin, at Higher Elevation Curb Cut or than Bypass Flow Line Other Means of Overflow Relief , Clean out Storm Water Inflow Energy t „ Stones Media 00 Filtenra'Concrete Treated Stormwater Container Stormwater flows through a specially designed filter media mixture contained in a landscaped concrete container. The mixture immobilizes pollutants which are then decomposed, volatilized and incorporated into the biomass of the Filterra°system's micro/macro fauna and flora. Stormwater runoff flows through the media and into an underdrain system at the bottom of the container, where the treated water is discharged. Higher flows bypass the Filterra°to a downstream inlet or outfall. Maintenance is a simple, inexpensive and safe operation that does not require confined space access, pumping or vacuum equipment or specialized tools. Properly trained landscape personnel can effectively maintain Filterra°Stormwater systems by following instructions in this manual. 10/08/09 filterra.com toll free: (866) 349 3458 6) fitterra Basic Operations Filterra°is a bioretention system in a concrete box. Contaminated stormwater runoff enters the filter box through the curb inlet spreading over the 3-inch layer of mulch on the surface of the filter media. As the water passes through the mulch layer, most of the larger sediment particles and heavy metals are removed through sedimentation and chemical reactions with the organic material in the mulch. Water passes through the soil media where the finer particles are removed and other chemical reactions take place to immobilize and capture pollutants in the soil media. The cleansed water passes into an underdrain and flows to a pipe system or other appropriate discharge point. Once the pollutants are in the soil, the bacteria begin to break down and metabolize the materials and the plants begin to uptake and metabolize the pollutants. Some pollutants such as heavy metals, which are chemically bound to organic particles in the mulch, are released over time as the organic matter decomposes to release the metals to the feeder roots of the plants and the cells of the bacteria in the soil where they remain and are recycled. Other pollutants such as phosphorus are chemically bound to the soil particles and released slowly back to the plants and bacteria and used in their metabolic processes. Nitrogen goes through a very complex variety of biochemical processes where it can ultimately end up in the plant/bacteria biomass, turned to nitrogen gas or dissolves back into the water column as nitrates depending on soil temperature, pH and the availability of oxygen. The pollutants ultimately are retained in the mulch, soil and biomass with some passing out of the system into the air or back into the water. Design and Installation Each project presents different scopes for the use of Filterra systems. To ensure the safe and specified function of the stormwater BMP, Americast reviews each application before supply Information and help may be provided to the design engineer during the planning process. Correct Filterra°box sizing (by rainfall region) is essential to predict pollutant removal rates for a given area. The engineer shall submit calculations for approval by the local jurisdiction. The contractor is responsible for the correct installation of Filterra units as shown in approved plans. A comprehensive installation manual is available at fillrerra.com. Maintenance Why Maintain All stormwater treatment systems require maintenance for effective operation. This necessity is often incorporated in your property's permitting process as a legally binding BMP maintenance agreement. • Avoid legal challenges from your jurisdiction's maintenance enforcement program. • Prolong the expected lifespan of your Filterra media. • Avoid more costly media replacement. • Help reduce pollutant loads leaving your property. Simple maintenance of the Filterra is required to continue effective pollutant removal from stormwater runoff before discharge into downstream waters. This procedure will also extend the longevity of the living biofilter system. The unit will recycle and accumulate pollutants within the biomass, but is also subjected to other materials entering the throat. This may include trash, silt and leaves etc. which will be contained within the void below the top grate and above the mulch layer. Too much silt may inhibit the Filterra's° flow rate, which is the reason for site stabilization before activation. Regular replacement of the mulch stops accumulation of such sediment. 10/08/09 filterra.com toll free: (866) 349 3458 6) fi te rra When to Maintain? Americast includes a 1-year maintenance plan with each system purchase. Annual included maintenance consists of a maximum of two (2) scheduled visits. Additional maintenance may be necessary depending on sediment and trash loading (by Owner or at additional cost). The start of the maintenance plan begins when the system is activated for full operation. Full operation is defined as the unit installed, curb and gutter and transitions in place and activation (by Supplier)when mulch and plant are added and temporary throat protection removed. Activation cannot be carried out until the site is fully stabilized (full landscaping, grass cover, final paving and street sweeping completed). Maintenance visits are scheduled seasonally; the spring visit aims to clean up after winter loads including salts and sands. The fall visit helps the system by removing excessive leaf litter. A first inspection to determine if maintenance is necessary should be performed at least twice annually after every major storm event of greater than (1) one inch total depth (subject to regional climate). Please refer to the maintenance checklist for specific conditions that indicate if maintenance is necessary. It has been found that in regions which receive between 30-50 inches of annual rainfall, (2)two visits are generally required. Regions with less rainfall often only require (1) one visit per annum. Varying land uses can affect maintenance frequency; e.g. some fast food restaurants require more frequent trash removal. Contributing drainage areas which are subject to new development wherein the recommended erosion and sediment control measures have not been implemented require additional maintenance visits. Some sites may be subjected to extreme sediment or trash loads, requiring more frequent maintenance visits. This is the reason for detailed notes of maintenance actions per unit, helping the Supplier and Owner predict future maintenance frequencies, reflecting individual site conditions. Owners must promptly notify the (maintenance) Supplier of any damage to the plant(s), which constitute(s) an integral part of the bioretention technology. Owners should also advise other landscape or maintenance contractors to leave all maintenance to the Supplier(i.e. no pruning or fertilizing). Exclusion of Services It is the responsibility of the owner to provide adequate irrigation when necessary to the plant of the Filterra°system. Clean up due to major contamination such as oils, chemicals, toxic spills, etc. will result in additional costs and are not covered under the Supplier maintenance contract. Should a major contamination event occur, the Owner must block off the outlet pipe of the Filterra°(where the cleaned runoff drains to, such as drop-inlet) and block off the throat of the Filterra°. The Supplier should be informed immediately. 10/08/09 filterra.com toll free: (866) 349 3458 6) fl [terra Maintenance Visit Summary Each maintenance visit consists of the following simple tasks (detailed instructions below). 1. Inspection of Filterra°and surrounding area 2. Removal of tree grate and erosion control stones 3. Removal of debris, trash and mulch 4. Mulch replacement 5. Plant health evaluation and pruning or replacement as necessary 6. Clean area around Filterra° 7. Complete paperwork Maintenance Tools, Safety Equipment and Supplies Ideal tools include: camera, bucket, shovel, broom, pruners, hoe/rake, and tape measure. Appropriate Personal Protective Equipment(PPE) should be used in accordance with local or company procedures. This may include impervious gloves where the type of trash is unknown, high visibility clothing and barricades when working in close proximity to traffic and also safety hats and shoes. A T-Bar or crowbar should be used for moving the tree grates (up to 170 Ibs ea.). Most visits require only replacement mulch. Three bags of double shredded mulch are used per unit (on a standard 6x6' size). Some visits may require additional Filterra engineered soil media available from the Supplier. 10/08/09 filterra.com toll free: (866) 349 3458 Maintenance Visit Procedure 1. Inspection of Filterra®and surrounding area Record individual unit before maintenance with photograph (numbered). Record on Maintenance Report(see example in this document)the following ... Record on Maintenance Report the following: Standing Water yes I no Damage to Box Structure Damage yes I no to Grate yes I no Is Bypass Clear yes I no If yes answered to any of these observations, record with close-up photograph (numbered). 2. Removal of tree grate and erosion control stones � I 1 • Remove metal grates for access into Filterra®box. :•/w"" Dig out silt(if any) and mulch and remove trash&foreign items. Record on Maintenance Report the following: Silt/Clay yes I no Cups/Bags yes I no ire Leaves yes I no #of Buckets Removed 3. Removal of debris, trash and mulch After removal of mulch and debris, measure distance from the top of the Filterra®engineered media soil to the bottom of the top slab. If this distance is greater than 12", add Filterra® k _ media(not top soil or other)to recharge to a 9°distance. Record on Maintenance Report the following: Distance to Bottom of Top Slab(inches) #of Buckets of Media Added Filterra°Stormwater Bioretention Filtration System toll free: (866) 349 3458 fax: (804) 798 8400 1 maintenance(a1filterra.com filterra.com � terra 4. Mulch replacement { 19 Add double shredded mulch evenly across the entire unit to a depth of 3". • Ensure correct repositioning of erosion control stones by the Filterra inlet to allow for entry of trash during a storm event. Replace Filterra®grates correctly using appropriate lifting or moving tools,taking care not to damage the plant. f ` ` a 5. Plant health evaluation and pruning or replacement as necessary • Examine the plant's health and replace if dead. Prune as necessary to encourage growth in the correct directions 6 Record on Maintenance Report the following: Height above Grate (feet) Width at Widest Point (feet) Health alive I dead Damage to Plant yes I no Plant Replaced yes I no f T- 6. Clean area around Filterra® c+ c ' Clean area around unit and remove all refuse to be disposed of appropriately. 7. Complete paperwork *, 0 Deliver Maintenance Report and photographs to appropriate location (normally Americast during maintenance contract period). • Some jurisdictions may require submission of maintenance reports in accordance with approvals. It is the responsibility of ■ the Owner to comply with local regulations. 10/08/09 filterra.com toll free: (866) 349 3458 Maintenance Checklist Drainage Conditions to Check Conditions That System Problem For Should Exist Actions Failure Inlet Excessive sediment or Accumulated sediments Inlet should be free of Sediments and/or trash trash accumulation or trash impair free flow obstructions allowing free should be removed. of water into Filterra distributed flow of water into Filterra. Mulch Cover Trash and floatable Excessive trash and/or Minimal trash or other Trash and debris should debris accumulation debris accumulation. debris on mulch cover. be removed and mulch cover raked level.Ensure bark nugget mulch is not used. Mulch Cover "Ponding"of water on "Ponding"in unit could be Stormwater should drain Recommend contact mulch cover. indicative of clogging due freely and evenly through manufacturer and replace to excessive fine mulch cover. mulch as a minimum. sediment accumulation or spill of petroleum oils, Vegetation Plants not growing or in Soil/mulch too wet, Plants should be healthy Contact manufacturer for poor condition evidence of spill. and pest free advice. Incorrect plant selection. Pest infestation. Vandalism to plants. Vegetation Plant growth excessive Plants should be Trim/prune plants in appropriate to the accordance with typical species and location of landscaping and safety Filterra. needs. Structure Structure has visible Cracks wider than'/z inch Vault should be repaired cracks or evidence of soil particles entering the structure through the cracks Maintenance is ideally to be performed twice annually. Inspection to be performed after every major storm event>1 inch total depth,subject to climate. Filterra°Stormwater Bioretention Filtration System toll free: (866)349 3458 1 fax: (804)798 8400 1 maintenance(Wfilterra.com filterra.com Filterra® Project Maintenance Order Project Address Directions Project Company Owner Contact Name Telephone# Owner Notified of Mtce on(date) Filterra Units on this Order Total Units on this Project Date of Maintenance Arrival Time Departure Time # of Workers Notes on Project Maintenance Supervisor 12/14/04 Filterra®Structure Maintenance Report Project Structure Number Plant Type Structure Size Date GPS Pre Mtce Photo# Initial Observations Standing Water Y N Damage to Grate Y N IF Yes, STOP NOW&call 804-798-6068 Is Bypass Clear Y N Notes Damage to Box Structure Y N If YES to any observation take close up photo Waste Silt/Clay Y N Buckets Removed (#of) Cups/Bags Y N Notes Leaves Y N Other Media Distance to Bottom of Top Slab (in.) Notes Buckets of Media Added (#of) Mulch Netting Replaced Y N Bags of Mulch Added (#of) Stones Replaced Y N Notes Plant #1 #2 #1 € #2 Height above Grate (feet) Plant Replaced Y/N Y/N Width at Widest Point(feet) Notes Health Alive/Dead'Alive/Dead Damage to Plant Y/N ' Y/ N If YES to plant damage take close up photo Other Notes (use back if necessary) 12114104 4)) fl te rra Filterra° Warranty Seller warrants goods sold hereunder against defects in materials and workmanship only, for a period of(1) year from date the Seller activates the system into service. Seller makes no other warranties, express or implied. Seller's liability hereunder shall be conditioned upon the Buyer's installation, maintenance, and service of the goods in strict compliance with the written instructions and specifications provided by the Seller. Any deviation from Seller's instructions and specifications or any abuse or neglect shall void warranties. In the event of any claim upon Seller's warranty, the burden shall be upon the Buyer to prove strict compliance with all instructions and specifications provided by the Seller. Seller's liability hereunder shall be limited only to the cost or replacement of the goods. Buyer agrees that Seller shall not be liable for any consequential losses arising from the purchase, installation, and/or use of the goods. toI F- ---------------- I I I I I INLET SHAPING A i I A (BY OTHERS) I I co I I J i i SDR-35 PVC COUPLING I CAST INTO PRECAST BOX WALL BY AMERICAST (OUTLET I PIPE LOCATION VARIES) I I I I L-------------------- I T CURB (BY OTHERS) PLAN VIEW 1,1E TREE FRAME & GRATE CAST IN TOP SLAB PLANT AS SUPPLIED CLEANOUT COVER BY AMERICAST GALVANIZED CAST IN TOP SLAB (NOT SHOWN ANGLE NOSING FOR CLARITY) TOP SLAB CURB AND GUTTER INTERLOCKING (BY OTHERS) JOINT (TYP) STREET o to r, N �o DOWEL BARS > 0 12" O.C. z UNDERDRAIN STONE PROVIDED BY AMERICAST PERFORATED MULCH PROVIDED BY AMERICAST UNDERDRAIN SYSTEM BY AMERICAST FILTER MEDIA PROVIDED BY AMERICAST SECTION A-A DESIGNATION L. W TREE GRATE OUTLET QTY & SIZE PIPE 6 x 6 6'-0" 6'-0" (1) 3x3 4" SDR-35 PVC �• SIZES SHOWN ARE FOR THE MID ATLANTIC AND MAY VARY ACROSS THE COUNTRY PLEASE CONTACT FILTERRA FOR A LIST OF SIZES WITHIN YOUR REGION DATE: 07-07-06 1 DWG: FTST-2 czleffflozwwa PRECAST FILTERRA® UNIT Copyright©20076yAmericast STANDARD CONFIGURATION US PAT 66,,277,,22174 AND 6,569,321 i 6„ � W � 6„ o I I I I I INLET SHAPING A I i A (BY OTHERS) I I I I I I SDR-35 PVC COUPLING I I CAST INTO PRECAST BOX I I WALL BY AMERICAST I (OUTLET PIPE LOCATION VARIES) L---------------------------- I � CURB (BY OTHERS) PLAN VIEW 1�L TREE FRAME PLANT AS SUPPLIED CLEANOUT COVER & GRATE BY AMERICAST GALVANIZED CAST IN TOP SLAB CAST IN (NOT SHOWN ANGLE NOSING TOP SLAB TOP SLAB FOR CLARITY) CURB AND GUTTER INTERLOCKING loo (BY OTHERS) JOINT (TYP) STREET i. o ' s H cD 04 I DOWEL BARS ® 12" O.C. a z �. MULCH PROVIDED BY AMERICAST PERFORATED UNDERDRAIN STONE PROVIDED BY AMERICAST UNDERDRAIN SYSTEMBY AMERICAST FILTER MEDIA PROVIDED BY AMERICAST SECTION A-A DESIGNATION L. W TREE GRATE OUTLET QTY & SIZE PIPE 4 x 6 4'-0" 6'-0" (1) 3x3 4" SDR-35 PVC 4 x 8 4'-0" 8'-0" (1) 30 4" SDR-35 PVC 4 x 12 4'-0" 12'-0" (2) 30 4" SDR-35 PVC 6 x 8 6'-0" 8'-0" (1) 4x4 4" SDR-35 PVC 6 x 10 6'-0" 10'-0" (1) 4x4 6" SDR-35 PVC 6 x 12 6'-0" 12'-0" (2) 4x4 6" SDR-35 PVC 7 x 13 7'-0" 13'-0" (2) 4x4 6" SDR-35 PVC •� SIZES SHOWN ARE FOR THE MID ATLANTIC AND MAY VARY ACROSS THE COUNTRY PLEASE CONTACT FILTERRA FOR A LIST OF SIZES WITHIN YOUR REGION DATE: 09-04-07 DwG: FTNL-3 PRECAST FILTERRA® UNIT f Reofra® NARROW LENGTH CONFIGURATION US PAT 6,277,274 Copyright 2007 by Amcricast AND 6.569,321 .I 6 � W � 6„ m I I 1 I INLET SHAPING I I (BY OTHERS) I I I I I I A I I A I I I I I I I I I I I I I I I I I I I I I L------I-I-----L CURB (BY OTHERS) CD PLAN VIEW L SDR-35 PVC COUPLING CAST INTO PRECAST BOX WALL (OUTLET PIPE LOCATION VARIES) CLEANOUT PLANT AS SUPPLIED COVER BY AMERICAST TREE FRAME & GRATE CAST IN (NOT SHOWN GALVANIZED CAST IN TOP SLAB :::::::,TOP SLAB FOR CLARITY) ANGLE NOSING TOP SLAB t CURB AND GUTTER INTERLOCKING JOINT (TYP) 00 (BY OTHERS) 1 STREET 0 cD iwi' Fo DOWEL BARS z ® 12" O.C. FILTER MEDIA PROVIDED BY AMERICAST PERFORATED MULCH PROVIDED BY AMERICAST [ UNDERDRAIN SYSTEM UNDERDRAIN STONE PROVIDED BY AMERICAST 0 BY AMERICAST JSECTION A-A DESIGNATION L W TREE GRATE OUTLET OTY & SIZE PIPE 6 x 4 6'-0" 4'-0" (1) 3x3 4" SDR-35 PVC 8 x 4 8'-0" 4'-0" (1) 3x3 4" SDR-35 PVC 8 x 6 8'-0" 6'-0" (1) 4x4 4" SDR-35 PVC 10 x 6 10'-0" 6'-0" (1) 4x4 6" SDR-35 PVC 12 x 4 12'-0" 4'-0" (2) 3x3 4" SDR-35 PVC 12 x 6 12'-0" 6'-0" (2) 4x4 6" SDR-35 PVC 13 x 7 13'-0" 7'-0" (2) 4x4 6" SDR-35 PVC •' SIZES SHOWN ARE FOR THE MID ATLANTIC AND MAY VARY ACROSS THE COUNTRY PLEASE CONTACT FILTERRA FOR A LIST OF SIZES WITHIN YOUR REGION DATE: 09-04-07 1 DWG: FfNW-3 Q L�%LILSLnS��L.;_h�J U® PRECAST FILTERRA® UNIT f��(o1Copyright��20O76yAmcricast NARROW WIDTH CONFIGURATION U US PAT 6.277,274 AND 6,569,321 Appendix C: Soils Report f[ REPORT OF GEOTECHNICAL,INVESTIGATION PROPOSED 4-68 BUILDING BOEING RENTON PLANT S&EE JOB NO. 1 104 MARCH 25,201 1 I t04rpc S&EE I. S&EE [ SOIL&ENVIRONMENTAL ENGINEERS, INC_ 16625 Redmond Way, Suite M 124, Redmond, Washington 98052, I425) 868-5868 I. March 25,2011 Mr.Mehdi Nakhjiri, P.E. The Boeing Company P.O. Box 3707 MC 61-90 Seattle, WA 98124-2207 CC: Mr. Bill Rockwell Report Geotechn ical Investigation Proposed 4-68 Building Boeing Renton Plant Dear Mehdi: We are pleased to present herewith our Report of Geotechnical Investigation for the referenced project_ Our services were authorized via Boeing's contract f#CNT-R-10073-111016. We appreciate the opportunity to provide our services. Should you have any questions regarding the contents of this report or require additional information,please contact the undersigned. Very truly yours, +s F1Vc SOIL&ENVIRONMlT1TAL ENGINEERS, WC. V � 28160 3 le p C.I.Shin, Ph.D_, P-E. President t t04rpt S&EE Section TABLE OF CONTENTS Page �T I, 1.0 INTRODUCTION_.........................._......._----._..._.........._...._...__...----•------._....__.....----•------.-..... . __......_..__._6 re 2.0 SCOPE OF SERVICES........................._....---•-----._...............................................................................__-._......._-...6 _ . 2.0 SITE CONDITIONS......................................................... .................................................................................2 3.1 SITE HISTORY&GEOLOGY.......__... _ 2 3.2 SUBSURFACE CONDITIONS AT THE PROJECT AREA....................................................................................3 3.3 GROUNDWATER CONDITIONS.__..... 4 4-0 LABORATORY TEST........._.................................................................................................................................4 5-0 CONCLUSIONS AND RECOMMENDATIONS....................................... .........5 5.1 GENERAL.........................._................................................................................................................................5 5.2 PRELOAD 5 5.3 PILE FOUNDATION.. 7 5.4 LATERAL EARTH PRESSURES_._._... 9 5.5 STRUCTURAL FILL.................................................................................__..........---.._...._....._................._.__.......-.10 5.6 FLEXIBLE PAVEMENT........................................................._......................................................................... !1 5.7 TEMPORARY AND PERMANENT EXCAVATIONS.....:......:..........................................................___..._...--_...l 5.8 SEISMIC CONSIDERATIONS AND HAZARDS......................................................•__......_.._._......__._......._..____.12 6.0 CLOSURE.............................................................»......._......................»..........--•-•-----._........._------------......._..-----....12 FIGURE 1:SITE LOCATION MAP FIGURE 2:SITE&EXPLORATION PLAN FIGURE 3:SOIL PROFILE- PLATE 1: PROMINENT ACTIVE FAULTS IN PUGET SOUND AREA PLATE 2: PRELOAD INDUCED GROUND SETTLEMENT(1) PLATE 3-- PRELOAD INDUCED GROUND SETTLEMENT(2) PLATE 4:SETTLEMENT MARKER APPENDIX A: FIELD EXPLORATION LOGS AND KEY APPENDIX B: LABORATORY TEST RESULTS APPENDIX C: RESPONSES OF LATERALLY LOADED PILE t 104rpt S&F.E �a r REPORT OF GEOTECHNICAL INVESTIGATION j PROPOSED 4-68 BUILDING Er BOEING RENTON PLANT For The Boeing Company 1.0 INTRODUCTION We present in this report our geotechnical recommendations for the proposed 4-68 Building at Boeing's Renton Plant. The proposed building will be located about 12 feet to the west of the existing 4-75 building. A project location plan is shown in Figure I which is included at the end this report. We understand that the new building will be single-story with 75,000 square feet of manufacturing and warehouse space. The building will house Buyer Furnished Equipment (BFE) seat assembly tine along with new office, loading dock, and storage space. We further understand that the design floor load will be 500 pounds per square feet(psf)and the column load will be on the order of 150 kips. The finished floor elevation will be close to existing ground surface and thus cut or fill will be minimal. 2.0 SCOPE OF SERVICES The purpose of our investigation is to develop geotechnical recommendations regarding the proposed development. Specifically,our services included: 1_ Attend meetings. 2. Review existing regional and local geologic information;reports,and-studies relevant to the project design. 3. Explore the subsurface soil and groundwater conditions at the site by the drilling of three soil test borings_ 4. Perform a laboratory testing program which includes torvane shear and consolidation tests on soft and compressible soils. 1 104rpt S&EE 5_ Evaluate subsurface soil and groundwater conditions and provide recommendations regarding: • Preload of slab area 1 • Pile foundation for building support L • Soil pressures for retaining wall design • Earthwork 6. Preparation of this written report documenting our findings and recommendations. 2.0 SITE CONDITIONS 3.1 SITE HISTORY&GEOLOGY Boeing Renton Plant is located on the alluvial fan of Cedar River where it discharges into Lake Washington_ The native soils in the area consist of loose and unconsolidated alluvial sediments extending to 100 feet or more in depth. During WW 11, the plant area was leveled by about 2 to 5 feet thick of fill. The native soils immediately under the fill include soft and compressible silt and loose sand. Groundwater level is typically about 4 to 6 feet below the ground surface. The project site is located about 1/2 miles to the south of Lake Washington shoreline and 300 feet to the east of Cedar River_ The site grade is relatively flat. Currently, the western portion of the proposed building area is an asphalt-paved parking lot. The eastern portion of the area includes a covered walkway and a service area_ This service area has a concrete slab that is about 50 feet in width and parallel the west side of 4-75 building. Published geologic map(USGS Geologic Map of the Renton Quadrangle, King County, Washington by D. R. Mullineaux, 1965) indicates that the majority of Renton area has been modified by past grading activities. Cedar River have meandered through various portions of the city since last glaciations and deposited alluvial soils. The upper portion of these soils is typically soft and unconsolidated_ A liquefaction map(Preliminary Liquefaction Susceptibility Map of the Renton Quadrangle, Washington by Stephen Palmer)indicates that the project area has high liquefaction susceptibility. Seattle Fault Plate 1, which is included at the end of this report, shows that Seattle Fault is the prominent active fault closest to the site_ The fault is a collective term for a series of four or more east-west-trending, south-dipping fault strands underlying the Seattle area. This thrust fault zone is approximately 2 to 4 miles 11041N 2 S&EE wide (north-south) and extends from the Kitsap Peninsula near Bremerton on the west to the Sammamish Plateau east of Lake Sammamish on the east. The four fault strands have been interpolated from over- water geophysical surveys(Johnson, et al_„ 1999) and, consequently, the exact locations on land have yet to be determined or verified. Recent geologic evidence suggests that movement on this fault zone occurred about 1,100 years ago,and the earthquake it produced was on the order of a magnitude 7.5. I` 3.2 SUBSURFACE CONDITIONS AT THE PROJECT AREA We have retained a sub-contractor to perform three soil test borings. The boring locations are shown on Figure 2 at the end of this report and the boring logs are presented on Figures A-I through A-3 in Appendix A. A Soil Classification Chart and Key to Boring Logs are shown at the end of the appendix. Our boringB-1 was drilled near the southeast corner of the proposed 4-68 building. The boring found 4 P P� g g inches thick concrete over soft silt(no base). Our borings B-2 and B-3 were drilled in the existing parking lot and near the center and northwest corner of the proposed building, respectively. Both borings found about 3 inches thick asphalt pavement over 1.5 to 2.5 feet of compacted recycled concrete. The parking lot was built in 2004 and our field representatives were onsite at the time to monitor the earthwork. Our record shows that the base material was generally compacted to at least 95% compaction. The construction drawing shows a pavement section of one inch thick asphalt over one inch thick top course and 6 inches thick base course_ Based on our knowledge of the parking lot construction, we believe that recycled concrete was used to fill portions of the lot. A soil profile is shown in Figure 3. The profile indicates that subsoils in the project area include alluvial soils extending to the maximum boring depth (100 feet). The soils include inter-bedded silt, silty sand, sand and gravel. In general, the soils are soft and loose from the ground surface to depths of 40 to 50 feet. Also, the upper 10 to 20 feet of soils are very soft, very loose and compressible. Similar but slightly denser or stiffer soils present below a depth of 50 feet.and,extend to a depth of 75 feet. From 75 feet down, the soil,becomes dense to very dense sand, silty sand and gravel. These dense soils.are underlain by soft to stiff silts near the depth of 100 feet. 1 t 04rpt 3 S&EE 33 GROUNDWATER CONDITIONS A groundwater monitoring well was installed in boring B-3 and the following groundwater depths were recorded after drilling_ Date Measured Groundwater Depth(below top-of asphalt pavement) March 2,2011 6 feet 2 inches March 4,2011 6 feet 8,inches March 16,2011 5 feet 2 inches 4.0 LABORATORY TEST Undisturbed soil samples were retrieved from the compressible silt and peat layers using Shelby tubes. The samples were transported to our sub-contracted soil laboratory, HWA in Bothell, WA for moisture content, torvane shear and consolidation tests. The test results are included in Appendix B. The test results show that the silt and peat have very low shear strength and moderate to high compressibility. t IQ4rpt 4 S&EE i 5.0 CONCLUSIONS AND RECOMMENDATIONS 5.1 GENERAL 1. The subsurface soils at the site include soft and loose, un-consolidated alluvial soils from the ground surface to depths of 40 to 50 feet. Due to their low shear strength and high compressibility these soils are not suitable for the support of conventional spread footings_ Augereast piles are recommended for building support. The piles should extend to a depth of 80 feet measuring from the current ground surface. 2. The results of our settlement analyses show maximum settlements of 4 to 6 inches under the proposed floor load. We believe this settlement is excessive and thus recommend preloading the slab area to pre-induce the ground settlement. To avoid down drag forces on piles the preload should be conducted prior to pile installation_ 3. The corridor between the existing 4-75 Building and new 4-68 Building should not be preloaded. This is to avoid excessive settlement of the footings that support the 4-75 building" Since a floor load of 500 psf will apply to the new slab in this corridor, we recommend that the slab in this corridor be structurally supported on piles. 4. The upper 40 feet or so of the subsoils are loose and liquefaction prone_ Recent studies show that liquefaction can also occur in fine-grained(silty and clayey)soils during strong earthquakes.(Bray, 1_D_, et. al. 2004). The proposed pile foundation would effectively mitigate the impact of liquefaction on building support. However, liquefaction induced sand boils and uneven ground settlements will threaten the slab-on-grade. As such, reinforcements in slab-on-grade should be considered. Details of our recommendations are presented in the following sections. 5.2 PRELOAD The preload program should begin by removing the concrete slabs between the 4-75 and 4-68 buildings and along the covered walkway. The asphalt pavement in the existing parking lot can remain during the preload pepod, but it should be broken into pieces of less than 10 feet by 10 feet in size. The soils immediately below the concrete and asphalt are compressible and vary horizontally. Removing the 1 to4rpt 5 S&EE r= i� concrete slab and breaking the asphalt pavement will promote uniform ground settlement and avoid bridging effect over non-uniform subgrade reaction_ r The preload should consist of non-structural fill soil that is at least 5 feet in thickness. The fill should be placed to have a minimum in-place density of 120 pcf(pounds per cubic feet)and be compacted to the extent that the fill can support the construction equipment. The surface should be graded for surface drainage. There should be 1 H:1 V side slopes and the edge/top of the one-to-one slope should extend 5"feet beyond the proposed south,west and north building lines,and in-line with the east building line. Based on our evaluations,the maximum ground settlement under the preload wilf be on the order of 6.5 inches and will take about 8 to 10 week to reach maturity_ Plate 2, at the end of this report, shows the predicted ground settlement from the center of the preload area toward the edge/top of the 1:1 slope and beyond. Plate 3 shows parts of the same curve but only the settlement beyond the edge/top of the 1:1 slope. Please note that the predicted ground settlement at the west side of 4-75 building line is 0.7 inches. A total of 3 settlement monitoring markers in the preload area and a total of 5 monitoring points on the 4-75 building wall should be installed prior to the placement of preload fill. The approximate locations of these monitoring stations are shown on Figure 2. A sketch showing the settlement marker is included in Plate 4. The movement of these monitoring stations should be surveyed initially (prior to the placement of preload), once every day for the first 5 days, and once every week thereafter. The survey results should be transmitted to our office within 24 hours. We will determine the termination of the preload period upon theoretical (about 90%)maturity is reached. Subgrade Preparation: Upon preload completion the preload soil and broken asphalt should be removed. The area to the west of the existing 4-75 building may have a silt or silty sand exposed at the subgrade, that is, no granular base_ In this case, the subgrade should be over-excavated 6 inches and the over-excavation backfilled with 1-1/4" minus crushed rock. Same rock should be used to fill any low area. The crushed rock should be placed in 8 to 10 inches thick lifts and each lift be compacted to a firm and non-yielding condition by a vibratory roller weighing at least 10 tons. All other areas should be re-compacted to a firm and non-yielding condition using the same compactor. 1 to4rpt 6 S&EE [s 5.3 PILE FOUNDATION I� 1 During the course of the project design, a few pile options were discussed and considered. We believe and Boeing concurs that augercast piles are best suited for the building support. The piles should be 18-inches in diameter and have a length of 80 feet, measuring from the existing_ground surface. This length will allow the pile tips be embedded at least 5 feet in a dense layer that consists of sand, silty sand or gravel, and at least 15 feet above a soft silt layer. Pile Capacities: The pile will develop a downward capacity of 180 kips and upward capacity of 90 kips. These values include a safety factor of 3 and have considered the effect of liquefaction. The capacities can be increased by 1/3 when considering the transient loads such as wind or seismic forces_ We recommend that all piles are spaced at least 3 pile diameters ON CENTER. Additional Lateral Resistance: Additional resistance to lateral loads will be provided by passive soil pressure against the pile caps and grade beams_ Assuming that structural fill is used for the backfill,an equivalent fluid density of 200 pounds per cubic foot(pcf)maybe used for design. The criteria for the structural fill are presented in Section 5.5 of this report. Pile Settlements: Pile settlement will result from elastic compression of the piles and the supporting soils. The settlement is estimated to be about 1/2,and will occur rapidly,essentially as the loads are applied. Respignse to Lateral Load: We have evaluated the responses of the pile using a computer program COM624 (A non-commercial program similar to LPILE and developed by Lymon Reese, et. al.for Federal Highway Administration, 1991). Our evaluations show that for a fixed head condition, the pile will have lateral capacities of I I kips when the pile heads are moved 1/2 inches. The soil profile and parameters utilized for the analyses,along with the computer outputs are included in Appendix C. Group effect for lateral capacity reduction should apply. That is, the capacity of the trailing pile.should be reduced by 60% when spaced at 3 pile diameter. Group action diminishes at a pile spacing of 7 pile diameters and the reduction can be lineally interpreted in between. Pile Reinforcement: Due to the presence of liquefaction zone in the upper 1/2 of the pile length, we recommend that the upper 2/3 of the pile be reinforced with a rebar cage and the entire length be reinforced with a center bar. 1 104rpt 7 S&EE r Pile Installation_ Cement grout must be pumped continuously during withdrawal of the auger, the rate of fwhich should not exceed about 5 to 8 feet per minute_ Also, at least 8 feet of grout head must be maintained during the entire withdrawal. We anticipate that the grout volume discharged from the pump to be about 1.2 to 1.5 times the theoretical volume of the drilled hole. The grout volume is usually obtained i; by counting the number of pump strokes. The grout pressure at the pump should be maintained in the range of 150 to 350 psi, depending on the length of the feeder hose used. The drilling contractor should provide pressure gages at the pump prior to drilling. For adjacent piles that are less than 5 feet clear space,the minimum waiting period is I2 hours. Quality Control: The following quality control measures must be implemented by the piling contractor. I) Prior to pile installation, the contractor should calibrate the grout pump by filling a 55-gallon drum. This calibration should be performed three times and approved by the onsite geotechnical engineer. 2) The rebar cage should be equipped with centralizers and the cage should be plumb before inserting into the drilled-hole. Single cable hooked on one side of the cage, or any other mean resulting in tilting of the cage is not allowed_ 3) The cage should sink to the design depth by its own weight_ Pushing the cage down by machine is not allowed- If grout de-hydration or any other reason preventing cage installation, the hole should be re-drilled and re-grouted. 4) Pile installation should be monitored by an engineer from our office. Our field representative will evaluate the adequacy of the construction methods and procedures. Any problems which might arise,or deviations from the specifications, will be considered during our evaluations and approval of each pile installed. t 1a4rpt s S&EE L� 5.4 LATERAL EARTH PRESSURES Lateral earth pressures on retaining walls or permanent subsurface walls, and resistance to lateral loads may be estimated using the following recommended soil parameters: Ite,, UI MIR- Ell _4 -A& V Mr -1 Ell�111V 01-t-, -ZI FP7, -x ,-I- M,tV�$ -�W_ 125 40 50 200 0.4 P I I K_ i n Note: 1)Hydrostatic pressures are not included in the above lateral earth pressures. —k I-S r �. 2)Lateral earth pressures are appropriate for level structural fill placed behind and in front of walls. The active case applies to walls that are permitted to rotate or translate away from the retained soil by approximately 0.002H, where H is the height of the wall. This would be appropriate for a cantilever reta- wall. The at-rest case applies to unyielding walls, and would be appropriate for wall restrained from lateral deflection such as basement walls, utility trenches or pits. SURCHARGE INDUCED LATERAL LOADS Additional lateral earth pressures will result from surcharge loads from floor slabs or pavements for parking that are located immediately adjacent to the walls. The surcharge-induced lateral earth pressures are uniform over the depth of the wall. Surcharge-induced lateral pressures for the "active" case may be calculated by multiplying the applied vertical pressure(in psf)by the active earth pressure coefficient(Ka).The value of Ka may be taken as 0.4. The surcharge-induced lateral pressures for the "at-rest" case are similarly calculated using an at-rest earth pressure coefficient(Ko)of 0-6. SEISMIC INDUCED LATERAL LOADS For seismic induced lateral loads,the dynamic force can be assumed to act at 0.6 H above the wall base and /"'the magnitude can be calculated using the following equation: AO PC = 14H Where PC = seismic-induced lateral load H = wall height 1104ro 9 S&EE l rr BACKFILL IN FRONT OF RETAINING WALLS Backfill in front of the wall should be structural fill. The material and compaction requirements are presented in Section 5.5_ The density of the structural fill can be assumed to be 130 pounds per cubic feet. BACKFILL BEHIND RETAINING WALLS Backfill behind the wall should be free-draining materials which are typically granular soils containing less than 5 percent fines(silt and clay particles)and no particles greater than 4 inches in diameter. The backfill material should be placed in 6 to 8-inch thick horizontal lifts and compacted to at least 90 percent of the maximum density in accordance with ASTM D-1557 test procedures. In the areas where the fill will support pavement,sidewalk or slabs,the top two feet of the backfill should be compacted to at least 95 percent of the maximum density. Care must be taken when compacting backfill adjacent to retaining walls,to avoid creating excessive pressure on the wall. DRAINAGE BEHIND RETAINING WALLS Unless the wall is designed to support hydrostatic pressure, rigid, perforated drainpipes should be installed behind retaining walls. Drainpipes should be at least 4 inches in diameter,covered by a layer of uniform size drain gravel of at least 12 inches in thickness,and be connected to a suitable discharge location_ An adequate number of cleanouts should be installed along the drain line for future maintenance. 5.5 STRUCTURAL FILL Structural fill materials should meet both the material and compaction requirements presented below. Material Requirements: Structural fill should be free of organic and frozen material and should consist of hard durable particles, such as sand, gravel, or quarry-processed stone_ Due to their silty nature the on-site soils are not suitable for structural fill. Suitable imported structural fill materials include silty sand, sand, mixture of sand and gravel (pitrun), and crushed rock. All structural fill material should be approved by an engineer from our office prior to use_ Placement and Compaction Requirements: Structural fill should be placed in loose horizontal lifts not exceeding a thickness of 6 to 12 inches, depending on the material type, compaction equipment, and number of passes made by the equipment. Structural fill should be compacted to at least 95%of the maximum dry density as determined using the ASTM D-1557 test procedures. 1104rpt 10 S&EE Prior to the placement of any structural fill, the subgrades of slab, pavement, and any other structural areas including sidewalks and driveway should,be thoroughly compacted. A vibratory roller compactor weighing at least 12 tons should be used for the compaction. The roller should travel with a casual walking speed and roll at least 6 times in two perpendicular directions. The compaction should be monitored by an engineer from our office. Any detected soft pockets should be over-excavated and backfilled with structural fill_ 5.6 FLEXIBLE PAVEMENT Assuming that the site subgrade is prepared according to recommendations presented in this report, we believe that the prepared subgrade will have a California Bearing Ratio(CBR)of at least 8_ The following paving sections are recommended. FLEXIBLE PAVEMENT For light traffic (Daily EAL=5 or less; few vehicles heavier than passenger cars no regular use by 2 or 3-axle trucks) Recommended section: 2 inches asphaltic concrete over 6 inches base.course. For medium traffic (Daily EAL=20 to 80;maximum 2,000 vehicles per day, including not over 10%2 or 3-axle trucks) Recommended section: 3 inches asphaltic concrete over 8 inches base course_ 5.7 TEMPORARY AND PERMANENT EXCAVATIONS When temporary excavations are required during construction, the contractor should be responsible for the safety of their personnel and equipment. The followings cut angles are provided only as a general reference: Temporary excavations should be sloped no steeper than 1.51-1:1 V(one horizontal to one vertical). The slope should continue from top to bottom (without vertical cut). Flatter slopes for all temporary cuts may be required if seepage occurs. All permanent slopes should be no steeper than 2H:IV. Water should not be allowed to flow uncontrolled over the top of any slope. Also, all permanent slopes should be seeded with the appropriate species of vegetation to reduce erosion and maintain the slope stability. t 104rpt 11 S&E E 5.8 SEISMIC CONSIDERATIONS AND HAZARDS We recommend that Site Class E as defined in the 2009 IBC be considered for the seismic design. Our evaluations show that the subsoils below groundwater table and to a depth of about 40 feet are liquefaction prone during strong.ear.hquakes (M = 7.5). The pile foundations recommended in this report will mitigate the impact of liquefaction on building support. However,damage to the slab-on-grade should be anticipated. The`site is located about 1/2 miles from the lake shore and 300 feet from the river channel_ Our evaluations r indicate that the risk of lateral spread is very low. 6.0 CLOSURE The recommendations presented in this report are provided for design purposes and are based on soil conditions disclosed by field observations and subsurface explorations_ Subsurface information presented herein does not constitute a direct or implied warranty that the soil conditions between exploration locations can be directly interpolated or extrapolated or that subsurface conditions and soil variations different from those disclosed by the explorations will not be revealed_ 'Be recommendations outlined in this report are based on the assumption that the development plan is consistent with the description provided in this report. If the development plan is changed or subsurface conditions different from those disclosed by the exploration are observed during construction,we should be advised at once so that we can review these'conditions,and if necessary,reconsider our design recommendations. tt04rpt 12 _ S&EE Puget Sound — Renton North 8th and Park Avenue North, Renton, WA 98055 {For mailing—see Company addresses) 51 52, 53.: Sty , - : From ' 1 H00 Bidp Fnxn Q WINgBe&n Lie Seattle _ tr Paywwwa`f LAKE WASHINGTON penny Dla 35 x' 167 cot 1a :., .y f� A �sw b- ,• EXIT 4 A COL 115 Issairltrah - �:' ,s�tiff� �,.. � 14dieraf�.q: 4 .® v �o-ss � /f5 fa>• r.y T igE f't+i •' ' i �U r?t" LT-1 71 E I9 �ji.r` sQ •s� r. ,• �� - N6THST �h�S 1045 r. a - SITE ` ` T '� �, � � Irpol ` ITN S'f •.u. 7r..�'•2 a '�-t�. -.�'�3�' z l ��- .��- � T. �•N JiF13T� �' f Frorn Seattle O yy 167 • h r fit} 3;.H b- w• 1A TN'-;- 169 i�uo i•- - - ,_- `t -'tS _ Corp ' 'ssn+srs t'` Z 40 .�r fyenta- CoUNta 8 1B1t awntsr.dam' s' ` iifn and G- Wa k1QtDn lti "+Y f f ♦. k�l Center K Renton n T� F - �z• ;B Rentort � :E p VIBa t. 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I `Sit aril `yv -WA Ar ' 60 30 0 60 120 II scoie feet S&EE 1104 B-i: Boring number and location Reference:Site Paving a Utility Plan by Magnusson I(lemencic Associates Figure 2 Site And Exploration Plan A AP B-3 B-2 B-1 0 C 0 N= o- Z Compressible silt (ve� oft) -T N 0-2 ML N = 0 Compressible silt(very soft) SP N= 0 N= 0 20 SP/ sP/M4/sm 6P/ Inter-bedded, sand, silt, silty sand& gravel (soft & loose) ,20 M L SM�MC MC N- 0-Z ML M[ N= 5� Compressible silt (very soft) N=/-Z w �0 N : 0- 6 Peat N= 8-!/ 40 0 w ^1 L N 0 rn = SM/M L/SP 2 U.1 0 6Q ML Inter-bedded, sand, silt&silty sand lip (soft&loose with medium stiff SM/ M and medium dense pockets) M4/ 60 sP 80 SP /v > 3o sp /V> 30 �P� 8 0 Sand,silty sand&gravel (dense) S P/SM N>30 I00 M ML LEGEND; N Standard Penetration Blow Count C: Recycled concrete Figure 3 N< 2 very soft or loose ML: Sift SOII Profile > 30 dense SP Sand S&EE 1104 SM. Silty sand SectionA-A' GP Gravel Proposed4.68 Building,Renton,WA SKAGIT } ly S L N SNOHOMISH f _ q CLAI LAM Everett e O L Y?ICI P I'C o NATIONAL , PARK !. o -- 3 7 S-minute J E F F E R S O N ��` _-S t DSO o topographic',! It I f ShlpftilOn Ruadtanptes r SEA L - arnatiotl C E /.wte �� o Fall it}- ('rr.,fituurt •{N, Snci a11711e MASON + KITSAP ort nods KIN b Rattlesnake' Mountain d_. fault one VSITE Reference Washington Department of Natural Resource, New Release April 16, 2009, Plate I S&EE Prominent Active Faults in Puget Sound Area Plate 2 Pre'-Load Induced Ground Settlement s. -3 -4 c -5 0 c� -6 -7 0 50 100 150 Distance from Center of Pre-Load (feet) (Edge/Top of 1 :1 Slope at 105 feet) Plate 3 Pre-Load Induced Ground Settlement 0 -0.5 s -2 -2.5 cis -3 -3.5 0 -4 t� -4.5 -5 0 10 20 30 40 50 Distance from Edge/Top of 1 :1 Slope (feet) f� i �i Measuring rod, 1/2"pipe or rebar Casing, 2" pipe (set but not fastened on plant) Preload soil, 5'min. Welded rod to plate / - Settlement plate 16" x 16"x 1/4"steel (asphalt) / Z_-_ Zy 30" min. Leveling sand, if needed (NOT TO SCALE) NOTES: 1_ INSTALL MARKERS ON FIRM GROUND OR ON SAND PADS IF NEEDED FOR STABILITY.TAKE INITIAL READING ON TOP`OF ROD AND AT ADJACENT GROUND LEVEL PRIOR TO PLACEMENT OF ANY FILL. 2. FOR EASE IN HANDLING, ROD AND CASING ARE USUALLY INSTALLED IN 5-FOOT SECTIONS. AS;FILL PROGRESSES, COUPLINGS ARE USED TO INSTALL ADDITIONAL LENGTHS, CONTINUITY IS MAINTAINED BY READING THE TOP OF THE MEASUREMENT ROD, THEN IMMEDIATELY ADDING THE NEW SECTION AND READING-THE TOP OF THE-ADDED ROD. BOTH READINGS ARE RECORDED- 3- RECORD THE ELEVATION OF THE'TOP OF THE MEASUREMENT ROD AT THE RECOMMENDED TIME INTERVALS_ EACH TIME,NOTE AND MEASURE THE ELEVATION OF THE ADJACENT FILL SURFACE 4. READ THE MARKER TO THE NEARESTO.01 FOOT,OR 0.005 FOOT IF POSSIBLE. NOTE THE FILL ELEVATION TO THE NEAREST 0.1 FOOT. Plate 4 S&EE Settlement Marker APPENDIX A FIELD EXPLORATION AND LOGS OF BORINGS The soil strata at the project site were explored with the drilling of three soil test borings, B-I to B-3 on February 28 through March 3, 2011. The borings were,advanced using mud rotary technique by a truck- mounted drill rig. A representative from S&EE was present throughout the exploration to observe the drilling operations, log subsurface soil conditions, obtain soil samples, and to prepare descriptive F_ geologic logs of the exploration. Disturbed soil samples were taken at 2.5-and 5-foot intervals in general accordance with ASTM D-1586, "Standard Method for Penetration Test and Split-Barrel Sampling of Soils" (1.4" I.D. sampler). The penetration test involves driving the samplers 18 inches into the ground at the bottom of the borehole with a 140 pounds hammer dropping 30 inches. The numbers of blows needed for the samplers to penetrate each 6 inches are recorded and are presented on the boring logs. The sum of the number of blows required for the second and third 6 inches of penetration is termed "standard penetration resistance", "blow count" or the "N-value". In cases where 50 blows are insufficient to advance it through a 6 inches interval the penetration after 50 blows is recorded. The blow count provides an indication of the density or consistency of the subsoil,and it is used in many empirical geotechnical engineering formulae. The following table provides a general correlation of blow count with density and consistency. DENSITY(GRANULAR SOILS) CONSISTENCY(FINE-GRAINED SOILS) N-value <4 very loose N-value <2 very soft 5-10 loose 3-4 soft 1 1-30 medium dense 5-8 medium stiff 31-50 dense 9-15 stiff >50 very dense 16-30 very stiff >30 hard Undisturbed soil samples were retrieved by Shelby tubes. The depth of Shelby tube samples are shown on the boring logs. After the boring was terminated, the borehole was backfilled with bentonite chips. One groundwater monitoring well was installed in Boring B-3_ The well was built with 2-inch diameter, 20-foot long PVC pipe. The bottom 10 feet of the pipe was slotted and a sand was used to backfill around the slotted pipe. All soil cuttings and drill fluid were placed in 50-gallon drums which were stored onsite. The boring logs are included in this appendix. A chart showing the Unified Soil Classification System is included at the end of this appendix. ;z g BORING B-1 m � � 3 tz E CO 4 U op c c N j Surface condition: Driveway 0 Mt_ 4 inches thick concrete over gray sift(very soft) 1 18 1 4 ; 1 . 6 o1e ; 1e sP Gray fine sand (very loose) 10, ° ; is ML Brownish gray silt with trace fine sand (very soft) ; 0 18 ' 18 15' ° :, 18 ' 1s ° ' is ; sM Gray silty fine sand(very loose) ' Illl 20' �- (Boring log continued on Figure 1 b) Client: The Boeing Company Drilling Method: Mud rotary advanced by track-mount Diedrich D-120 Drill Rig Sampling Method: SPT sampler driven by 140--lb auto hammer Drilfing Date: March 1 and March 2,2011 Drilling Contractor: Holocene Drilling Figure 1 a S&EE Proposed 4-68 Building Job No_1104 u To a BORING B-1 arcm (Continued) sM Gray silty-fine sand(medium dense) 7 JJ !! , ff, ; ML Gray organic silt(soft) , 26 ; 18 3 e ; sP7 Gray fine sand and silty fine sand,trace fine to medium gravel(loose) ' a SM ; , a ; ta a . 12 ' -wood at 28 feet 3 ; , 30 3 ' to , PT Brown,non-fibrous peat(soft to medium stiff) 3 , r , ML Gray sift(soft) ; , ; , ; , ; 35; ; t to ' sm4 Gray silty fine sand and sandy silt(loose) 2 to ' ML r ' 3 ' 16 ,a ta PT Brown,non-fibrous peat(medium stiff) - ; ; , , -vane shear reading=0"3 ksf , 40;--- - (Boring log continued on Figure 1c) Client: The Boeing Company Drilling Method: Mud rotary advanced by track-mount Diedrich D-120 Drill Rig Sampling Method: SPT sampler driven by 1404b auto hammer Drilling Date: March Land March 2,2011 Drilling Contractor Holocene Drilling Figure 1 b S&EE Job No-1104 Proposed 4-68 Building ;A r= amm m B BORING B-1 aQ: 8 v (Continued)a �� C c 40 16 PT Brown non-fibrous peat(medium stiff) SMi Gray, inter-bedded silly fine sand, fine sand and silt(loose and soft with medium I SPi dense pockets) IIII ML 46: 3 18lilt 2 3 O , Illy , Ilil IIII 50 3 IsIlll 2 ' 14 . IIII -tens of peat at 51 feet -- IIII IIII IIII 55; „ ; ,e -medium dense at 55 feet 15 ,o ' le ' HII -lens of peat at 56 feet ' IIII IIII - - IIII (Boring log continued on Figure 1d) Client_ The Boeing Company Drilling Method: Mud rotary advanced by track-mows Diedrich D-120 Drill RiV Sampling Method: SPT sampler driven by 1404b auto hammer Drilling Date: March 1 and March 2,2011 Drilling Contractor: Holocene Drilling Figure 1 c S&EE Proposed 4-68 Building Job No-1104 � P g n D mo Q a BORING B-1 m H y (Continued) 4 o is E U r t/0 5 ; o r sMi Gray, inter bedded silty fine sand, fine sand and sift e SPr (medium dense and medium stiff) ' Ilil ML , ' Ilil A till le mt, Gray silt and fine sand(soft and loose) to , SIP 70 , z ,a , 2 ' ,a , e ; peat at 71 feet , , l 75 27 ; Gpj Gray fine to medium gravel with some fine to medium sand(very dense) SP ; ; (Boring log continued on Figure 1e) Client: The Boeing Company Drilling Method: Mud rotary advanced by track-mount Diedrich 0-120 Drill Rig Sampling Method SPT sampler driven by 140-lb auto hammer Drilling Date_ March 1 and March 2,2011 Drilling Contractor: Holocene Drilling Figure 1 d SEE Job No.1V4 Proposed 4-68 Building g im N o BORING B-1 o� (Continued) i. C 3 tCx N is A 80 sors•, e GPI Gray"fine to medium gravel with some fine to medium sand(dense to very dense) 8fi ' 75 ' 1a , 11 ' o 20 ; 90 18 to 2 sM Gray silty fine sand with trace fine to medium gravel(dense) , 17 ; Ilil , llll ' IlII 96: 17 ; 18 IIII 20 ' 72 18 ' illl ' lIli , -- 18 1a 1 tL Brown sift with peat(stiff) a s Boring completed at a depth of 100 feet on March 2,2011. Client: The Boeing Company Drilling Method: Mud rotary advanced by track-mount Diedrich D-120 Drill Rig Sampling Method: SPT sampler driven by 1404b auto hammer Drilling Date: March 1 and March 2,2011 Did"Contractor_ Holocene Drilling _Figure le S&EE Job No_11o4 Proposed 4-68 Building a m y � o a a BORING B-2 a� m En 7g m E U mc co j Surface condition. Parking lot - 0 4 inches thick asphalt pavement over recycled concrete(fill)(moist)(dense) 6 , ; 1 1 y 1 sMr Light brown silty fine sand and sandy silt(loose and soft) 3 1 18 ' ML 3 18i IIII 3 1 lilt , IF 6 s 18 ' 3 e sP Orange brown medium sand(very loose) 2 1 ; ML Gray sift with lenses of non-fibrous peat(very soft) o 18 19 10; ; ; ; spr Gray, inter-bedded fine sand, silt and silty sand(loose and soft) MU 15; 3 18 SM 5 ' 18 ; ' S 1 1 - 1 1 3 ' 18 , 0 12 , SI 1 1 20,_ (Boring log continued on Figure 2b) CIIeM_ The Boeing Company Drilling Method: Mud rotary advanced by track-mount Diedrich D-120 Drill Rig Sampling Method: SPT sampler driven by 1404b auto hammer Drilling Date: March 2 and March 3,2011 Drilling Contrador Holocene Drilling Figure 2a S&EE Job No.I1N Proposed 4-68 Building s< N mo Q a BORING B-2 m (Continued) �U Ip �� _ CO Q O U U 0 20 3 e SPI Gray, inter-bedded fine sand, silt and silty sand(loose and soft) 4 MU SM 2 ' 18 ; 3 9 5 ■ 26, ' 3 ' 18 ; 8 ' 9 8 3 18 ' 3 14 -trace organic matter at 28 feet ; 30' PAL Gray and brown silt(very soft) ; ; ; 1 18 1 ' 12 ; 1 ; ; ; ; 35; ; ' -brown non-fibrous peat at 36 feet ; ; ' 40:- — -'- - J (Boring log continued on Figure 2c) Client: The Boeing Company Drilling Method: Mud rotary advanced by track-mount Diedrich D-120 Drip-Rig Sampling Method: SPT sampler driven by 140-lb auto hammer Drlfing Date: March 2 and March 3,2011 Wfing Contractor: Holocene Drilling Figure 2b IM Pro JWk 1t04 Proposed 4-68 Building :>onrb. Po 9 ;o Q BORING B-2 (Continued)_) 40 2 }2 PT .Brown, non-fibrous peat with lenses.of gray silty sand and sandy silt(soft) 4 0 ' 18 ; O ; 9 o Sivt Gray silty fine sand and sandy sift with trace organic matter(very loose and soft) ML 45' ; 2 18 IIII 2 ; 18 ' 3 , IIII ' Illl IIII ' - IIII so; 2 18 ' ML Gray sift,trace fine sand,trace organic matter(medium stiff) 3 55; 0 18 ' 0 18 ; PT Brown, non-fibrous peat with lenses of gray silt and fine sand(very soft) 0 mu Gray silt and fine sand, trace organic matter(stiff and medium dense) ' 6 ' 18 SP ' 14 (Boring log continued on Figure 2d) Client The Boeing Company Drilling Method: Mud rotary advanced by track-mount Diedrich 0-120 Drill Rig Sampling Method: SPT sampler driven by 140-lb auto hammer - Drilling Date: March 2 and March 3,2011 Drilling Contractor_ Holocene Drilling Figure 2C S&EE Job No.1104 Proposed 4-68 Building c b a BORING B-2 ao (Continued) o tr '. N 60 _ s ; 12 sP Gray fine to medium sand with lenses of soft silt'(medium dense) ; t ' ; ; 66: ' 12 18 12 ; '2 . 7 PT Brown non-fibrous peat(soft) ; 70; z 'a ; 10 ' 'a , 15 ; sw Gray silty fine sand and sandy silt(medium dense and stiff) , ML ; ; sP Gray fine to medium sand with some fine to medium gravel,trace sift(dense) ; 76; 1a ' . ; ; ; (Boring log continued on Figure 2e) Client The Boeing Company Drilling Method: Mud rotary advanced by track-mount Diedrich D-120 Drill Rig Sampling Method: SPT sampler driven by 140-lb auto hammer Drilling Date. March 2 and March 3,2011 .Drilling Contractor. Holocene Drilling Figure 2d S&EE , Proposed 4�8 Building lob No.1104 P g IS C1 0 y BORING B-2 (Continued) ,a , ,a SP 'Gray fine to medium sand with some fine to medium gravel,trace sift 'a ' (medium dense to dense) ; ' ; 115 ' ,8 ; t7 ; to n , 90; ' ; 18 t a Sty Gray silty fine sand(medium dense to dense) i , , llll Ilfl III( IIII 95; „ ; ,e � ,3 ' 9 17 - IIII ` IIII ; IIII 1od !!II z 1z Boring completed at a depth of 100 feet on March 3,2011_ ,2 IIII Client: The Boeing Company Drilling Method: Mud rotary advanced by track-mount Diedrich D-120 Drill Rig Sampling Method: SPT sampler driven by 1404b auto hammer Drilling Date: March 2 and March 3,2011 Figure 28 Drilling Contractor: Holocene Drilling g S&EE Job No.1104 Proposed 4-68 Building r IS r+ b mo n BORING B-3 z m m a yr n O UU E U a m c c j Surface condition: Parleng lot p GVY 3 inches thick asphalt pavement over recycled concrete(fillxmoistxvery dense) 41 ' 16 ' 48 ' t8 47 ' s 10 ML Gray sift with lenses of silty fine sand and fine sand(soft to very soft) 6 3 18 1 ' 18 ; o 1e ' 18 10' SM Gray silty fine sand with some fine gravel(loose) 0 18 i 4 8 i 7 /8 SP/ Gray medium to coarse sand and fine to medium gravel(medium dense) 14 ' 8 r7 GP 16: 8 ' 18 ;- 7 8 7 ' 20:--- (Boring log continued on Figure 3b) Client: The Boeing Company Drilling Method: Mud rotary advanced by track-mount Diedrich 0-120 Drill Rig Sampling Method: SPT sampler driven by 1404b auto hammer Drilling Date: February 28 and March 1,2011 Drilling Contractor: Holocene Drilling Figure 3a S&EE Proposed 4-68 Building Job No-11b4 D m y mo Q BORING B-3 MA � (Continued) n o - CIO, a co -S:S 20 iq y , GP Gray fine to medium gravel with few coarse sand(medium dense) ' 7 , SIP y , 3 ' 18 18 3 ; ML Brown sift with trace very fine sand(medium stiff) ' , 3., , , 26 sP Brown to gray to black fine to medium sand with lenses of grayish brown sift (medium dense) ; ' S ' 12 7 ; , ; 30; 8 18 12 ' 18 , 14 ' , , , ; 2 1a ML Grayish brown silt with trace fine sand,trace peat(soft) , 2 ; 35 ; , 3 ' 18 , s ; Is , sPl Inter-bedded fine to medium sand,silt, and silty tine sand, lenses of brown peat(loose) 7 , MCI sM ; ; (Boring log continued on Figure 3c) Client: The Boeing Company Drilling Method: Mud rotary advanced by track-mount Diedrich 0-120 Drill Rig Sampling Method: SPT sampler driven by 1404b auto hammer Drilling Date: February 28 and March 1,2011 Drilling Contractor Holocene Drilling Figure 3b SUE JobNoAll(W Proposed 4-68 Building c m m H 0 4 � BORING B-3 oa o (Continued) a rm E co 0 40 0 78 spr Inter-bedded fine to medium sand, silt, and silty fine sand(hose) r , MU SM t ; ; r ; , , ; ; ; 45: o 18 PAL Gray silt with trace fine sand, lenses of peat(very soft) ,e vane shear reading=0.4 ksf ; , 50; s o sP Gray fine to medium sand with trace silt(loose to medium dense) , ; 55; 11 18 ' -medium dense below 55 feet 13 ' 18 ; 15 ' , li0,- - (Boring log continued on Figure 3d) Client The Boeing Company Drilling Method: Mud rotary advanced by track-mount Diedrich D-120 Drill Rig Sampling Method: SPT sampler driven by 1404b auto hammer Drilling Date: February 28 and March 1.2011 Drilling Contractor Holocene Drilling Figure 3c SUE Job Ikk-1104 Proposed 4-68 Building t, m m so BORING B-3 (Continued) $ - E m ; j i" 60 e ; 12 sP Gray fine to medium sand with lenses of soft silt(loose to medium dense) ; 66- 3 ' 18 ; 3 9 4 i i PT Brown non-fibrous peat(soft) 70; 3 18 -vane shear reading=0.4 ksf 6 ' 18 ; 2 ML Gray silt with trace fine to medium gravel(medium stiff) sP Gray fine to coarse sand with some fine to medium gravel, trace silt(dense) 75; ' 19 ; 18 1a ' 12 , 20 ' 80 -- - --- (Boring log continued on Figure 3e) Client: The Boeing Company Drilling Method: Mud rotary advanced by track-mount Diedrich D-120 Drill Rig Sampling Method: SPT sampler driven by 1404b auto hammer Drilling Date: February 28 and March 1,2011 Drilling Contractor: Holocene Drilling Figure 3d SEE Job No.1104 Proposed 4-68 Building mo a BORING B-3 (Continued) a o vs co Y .80 is ; is SP Gray fine to medium sand with some fine to medium gravel,trace silt(dense) 19 , , .S ; ; ; 86; 15 ; fe -tense of peat at 85 feet 19 ; l8 1e . , 90 12 ' 1s ; -lense of medium stiff silt at 90 feet s 12 , s S5 o is ML Gray silt with trace fine sand(very soft to stiff) , -vane shear reading=0.5 ksf 10d___'_ __ stiff below 100 feet a is Boring completed at a depth of 100 feet on March 1,2011_ r A groundwater monitoring well is installed with slotted PVC pipe from depths of 10 to 20 feet. Depth of groundwater measured at a depth of 6 feet 2 inches on March 2,2011. Client The Boeing Company Drilling Method- Mud rotary advanced by track-mount Diedrich D-120 Drill Rig Sampling Method: SPT sampler driven by 1404b auto hammer Drilling Date: February 28 and March 1.2011 Figure 3e Drilling Contractor Holocene Drilling S&EE Proposed 4-68 Building Job No.I IN UNIFIED SOIL CLASSIFICATION SYSTEM Q - - __ -_ ' G ' DESCRIPTION MAJOR DIVISIONS I }` GW WELL-GRADED GRAVELS OR GRAVEL-SAND MIXTURES, CLEAN p LITTLE OR NO FINES GRAVELS w GP POORLY-GRADED GRAVELS OR GRAVEL-SAND MIXTURES, (uE oR J o 0 o >4� Ln • LITTLE OR NO FINES NO FINES) w =u<gI " O w fl GM SILTY GRAVELS,GRAVEL-SAND-SILT GRAVELS _ MIXTURES `w w " T, WITH FINES (9 of""w Zo w I GC CLAYEY GRAVELS,GRAVELSAND CLAY InPPRECIAetE f 0 F W Z LL _ MIXTURES AMOUNT OF FINES) Z H LLO SW WELL-GRADED SAND OR GRAVELLY SANDS, CLEAN < z s LITTLE OR NO FINES O az ��< LLW w Y� WW - Y SP POORLY-GRADED SANDS OR GRAVELLY SANDS, 1 o N.w m> w w o ' urnE OR LITTLE OR NO FINES NO FINES) p o a y a' Q o o o o SM SILTY SANDS,SAND-SILT MIXTURES SANDS Q wn W w y a U m w ---- — ----- - WITH FINES u) oily Cov wo �o SC CLAYEY SANDS,SAND-CLAY MIXTURES (APPRECIABLE 20. 7 J AMOUNT OF FINES) m ML INORGANIC SILTS,VERY FINE SANDS,ROCK FLOUR,SILTY OR 0> CLAYEY FINE SANDS OR CLAYEY SILTS WITH SLIGHT PLASTICITY �' CL INORGANIC CLAYS OF LOW TO MEDIUM PLASTICITY,GRAVELLY SILTS 8 CLAYS �" w CLAYS,SANDY CLAYS,SILTY CLAYS,LEAN CLAYS O �" a UOUID LIMB LESS THAN 50 In ul w 8 OL ORGANIC SILTS AND ORGANIC SILT-CLAYS OF LOW W 1 o PLASTICITY z z p MH INORGANIC SILTS,MICACEOUS OR DIATOMACEOUS FINE z SANDY OR SILTY SOILS,ELASTIC SILTS o INORGANIC CLAYS OF HIGH PLASTICITY,FAT CH CLAYS SILTS &CLAYS w W W z_ o l -- STICITY LIQUID LIMIT GREATER THAN 50 p OH ORGANIC CLAYS OF MEDIUM TO HIGH PLA , LL ORGANIC SILTS PT PEAT AND OTHER HIGHLY ORGANIC SOILS HIGHLY ORGANIC SOILS IIVI� DEPTH OF STANDARD PENETRATION TEST DEPTH OF UNDISTURBED SHELBY TUBE SAMPLE V DEPTH OF GROUNDWATER DURING EXPLORATION SOIL CLASSIFICATION CHART AND KEY TO EXPLORATION LOG S&EE (3 I APPENDIX B LABORATORY TEST RESULTS r 2 1 104RP[ S&EE Mum HWA GEOCIENCES INC. Materials Testing Laboratory Log of Extruded Shelby Tube (ASTM D 2937) . Visual-Manual Soil Classification (ASTM D 2488) Project Name: Building 468 AWA Project Number: 2011-025-23 y Date Tested: March 4, 2011 Technician: AC Borehole: B-2 Sample: NA Depth: 12— 14 feet z Depth Log_ Soil Description Notes ------------ 12.0 `= - = Loose silty gray SAND _- (SM) 12.5 13.0 Very soft gray SILT Torvane Shear= 100 psf (ML) 13.5 Medium stiff gray Torvane Shear=600 psf CLAY(CL) Very soft gray Torvane Shear= 100 psf 14.0 CLAY(CL) Figure: 2 rip HWA GEOSCIENCES INC. Materials Testing Laboratory Log of Extruded Shelby Tube (ASTM D 2937) Visual-Manual Soil Classification (ASTM D 2488) Project Name: Building 468 HWA Project Number: 2011-025-23 Date Tested: March 4, 2011 Technician: AC Borehole: B-2 Sample: I Depth: 37.5 —39.5 feet Depth Log Soil Descri Lion Notes 37.0 Torvane Shear= 300 psf 37.5 Olive gray soft to Torvane Shear=600 psf medium stiff SILT(ML) • 38.0 Torvane Shear=300 psf Torvane Shear=400 psf 38.5 Fibrous PEAT(PT) Consolidation sample location Olive gray soft to medium stiff SILT(ML) 39.0 Figure: 3 "� HWA GEOSCIENCES INC T Materials Testing Laboratory Log of Extruded Shelby_Tube (ASTM D 2937) Visual-Manual Soil Classification (ASTM D 2488) Project Name: Building 468 - HWA Project Number: 2011-025-23 Date Tested: March 2,2011 Technician: HB Borehole: B-3 Sample: 1 Depth: 9— I I feet Depth Log il Description Notes 9.0 ay SILT(ML) Torvane Shear=400 psf medium stiff, Consolidation sample location 9.5 ay SILT(ML) • Torvane-Shear=400 psf 10.0 Medium dense to dense gray silty SAND(SM) grading to dense dark gray fine SAND (SP) 10.5 = Moisture Content=25.4% 11.0 Figure: 4 ONE DIMENSIONAL CONSOUDATION HWAGEOSCIENCES INC. ASTM D 2435 Project Name: Building 468 Project Number: 2011-025-23 Start Finish Borehole Number: B-1 Moisture Content 37.4 31.0 % Sample Number: 4 Saturation 95.e 104.1 % Sample Depth: 32.5-34.5 ft Dry Density 82.0 93.5 pcf Soil Description: Gray SILT(ML) Coeff.of Consol.(inzlminute) Void Ratio vs. Stress 1.0E-01 1.0E+00 1,10 1.05 1.05 1.00 1.00 m 0.95 0 0.95 ^y ,D C 0.90 m � 0.90 m a Q 0.85 0.85 0.80 0.80 0.76 0.75 0.1 1.0 10.0 100.0 Stress(ksQ FIGURE 7, ONE DIMENSIONAL HWAGEOS NCES INC.CIE CONSOLIDATION ASTM D 2435 Project Name: Building,468 Project Number. 2011-025-23 Borehole Number: B-1 Start Finish Sample Number: 4 Moisture Content 37.4 31.0 % Sample Depth: 32.5-34.5 ft Saturation 95.6 104.1 % Soil Description: Gray SILT(ML) Dry Density 82.0 93.5 pcf COW.of Consol.(in2fminute) Strain Vs. Stress 1.0E-01 1.0E+00 0.1 1 Stress(ksf) 1.10 0 .0 10.0 100.0 1.05 2 1.00 4 d 0 0.95 6 •o > c 0.90 y d 8 a 0.85 10 0.80 12 0.75 • 14 FIGURE 8 ONE DIMENSIONAL` HWAGEQSCI .LACES INC. CONSOLIDATION ASTM D 2436 Project Name: Building 468 Project Number: 2011-025-23 Borehole Number: B-2 Start Finish Sample Number: 1 Moisture Content 299.5 239.3 % Sample Depth: 37.5-39.5 ft Saturation 88.2 98.6 '% Soil Description: Dark brown PEAT Dry Density 16.5 22.1 pcf COW.of Consol.(In'/minute) Void Ratio vs. Stress 1.0E-02 1.0E-01 1.0E+0 0 9.00 9.00 8:50 8.50 8.00 8.00 7.50 7.50 a 0 7.00 7.00 Q� v 6.50 6.50 > 6,00 6.00 a 5.50 5.50 5.00 5.00 4.50 4.50 4.00 4.00 0.1 1.0 10.0 100.0 Stress (ksf) FIGURE 9 ff LW, ONE DIMENSIONAL HWAGEOSCIENCES INC. CONSOLIDATION ASTM D 2435 Project Name: Building 468 Project Number: 2011-025-23 Start Finish Borehole Number: B I Moisture Content 299.5 239.3 % Sample Number; Sample Depth: 37.5-39.5 ft Saturation 88.2 98.8Dry Density 18.5 22.1 pcf Soil Description: Dark brown PEAT Coeff.of Consol.(O/minute) Strain vs. Stress 1.0E-02 1.0E-01 1.0E+00 Stress(ksf) 0.1 1.0 10.0 100,0 9.00 0 8.50 5 8.00 10 7.50 d 0 7.00 15 ro a .. o 6.50 c 20 6.00 a 25 5,50 5.00 30 4:50 35 ]TN 4.00; 40 FIGURE 10 ffM ONE DIMENSIONAL CONSOLIDATION H•WAGEOSCIENCES INC AS1IVI,D 2436 Project Name: Building 488 Project Number: 2011-026-23 Start Finish Borehole Number: B-3 Sample Number; I I1 Moisture Content 37.0 32.2 %Sample Depth; 9- 11 Saturation. 99.0 103.0 °� ft Dry Density 84.7 • 92.3 pcf Soil Description: Dark gray SILT(ML) Coeff.of Consol.(inz/minute) Void Ratio vs. Stress 1.0E-01 1.0E+00 1,05 1.05 i 1.00 1.00 d 0.95 o >° a d � ea 0.90 . 0.90 a 0.85 0,85 71 0.80 0.80 0.1 1.0 10.0 100.0 Stress(ksf) FIGURE 11 ONE DIMENSIONAL CONSOLIDATION HWAGEOSaENCES INC. ASTM D 2435 Project Name: Building 468, Project Number: 201r1-025-23 Borehole Number, B-3 Start Finish Sample Number: 1 Moisture Content 37.0 32.2 %. Sample Depth: 9.11 ft Saturation 99.0 103.0 % Soil Description: Dario gray SILT(MI-) Dry Density 84.7 92.3 pdf Coeff. of Consol.(in'Iminute) Strain vs. Stress 1.0E-01 1.0E+00 0.1 1.0 Stress (ksf) 1105 10.0 100.0 0 1 1.00 2 3 d v a 0.95 4 o ae c 5 d 0.90 y a 6 7 0.85 $ 9 0,80 10 FIGURE 12 J W, ONE DIMENSIONAL HWAGEOSCIENCES INC. ASTM D 1436 8TM 235 Project Name: Building 468 Project Number. 2011-026-23 Borehole Number: 3 Start Finish Moisture Content 126.0 88.2 % Sample Number. 3 °h Sample Depth: 35-37 ft Saturation 91.8 110.4. ,Soil Description: Olive brown SILT(ML) Dry Density 35.8 53:4; pcf Coeff. of Consol.(in2/minute) Void Ratio vs. Stress 1.0E-02 1.0E-01 1,0E+00 4.00 4.00 3.50 3.50 m o_ 3.00 3.00 w G! m v m 0 2.50 2.50 a 2.00 2.00 I 1.50 1.50 0.1 1.0 10.0 100.0 Stress(ksf) FIGURE 13 um ONE DIMENSIONAL H�NAGEOSCIENCES INC. CONSOLIDATION Project Name: Building 468 ASTM D 2435 Project Number: 2011-025-23 Borehole Number: B-3 Start Finish Sample Number: 3 Moisture Content 126.0 88.2 % Sample Depth: 35-37 ft Saturation 91.8 110.4 % Soil Description: Olive brown SILT(ML) Dry Density 35.6 63.4 pcf Coeff.of Consol.(in2/minute) 1.0E-02 1.0E-01 1.0E+00 Strain vs. Stress Stress(ksf) 4.00 00.1 1.0 10.0 100.0 5 3.50 - �s 10 a 3.00 15 o �- c 20 2.50 Q 25 2.00 30 35 1.50 40 FIGURE 14 APPENDIX C RESPONSES OF LATERALLY LOADED PILE I . 1104Rpt S&EE S&EE PROJECT '��`�il�� — 89f , SHEET- / OF___/__ BY C S DATE _�6-�/ CHECKED DATE f SUBJECT -- — P' JOB NO. / 4� PHASE TASK O- : Yy OSst-. U 0 2 0.. . O P C f de,WLe_ . . . . : _ 60 61k P�f n� Boeing 4-68 Bldg- 18-in augercast concrete pile UNITS--E%L INPUT INFORMATION THE LOADING IS CYCLIC NO. OF CYCLES = .50E+02 PILE GEOMETRY AND PROPERTIES PILE LENG [l = 960.00 IN MODULUS OF ELASTICITY OF PILE _ .300E+08 LBS/IN**2 1 SECI'ION(S) X DIAMETER MOMENT OF AREA INERTIA IN IN IN**4 IN**2 00 I8.000 .515E+04 .253E+03 960.00 SOILS INFORMATION X-COORDINATE AT THE GROUND SURFACE _ .00 IN SLOPE ANGLE AT THE GROUND SURFACE _ .00 DEG. 4 LAYER(S) OF SOIL LAYER I THE LAYER IS A SAND X AT THE TOP OF TILE LAYER = .00 IN X AT THE BIII" OF THE LAYER = 36.00 IN VARIATION OF SOIL MODULUS, k = .200E+02 LBS1IN**3 LAYER 2 THE LAYER IS A SAND X AT THE TOP OF THE LAYER = 36.00 IN X AT THE WHOM OF THE LAYER = 492.00 IN VARIATION OF SOIL MODULUS, k = .100E+02 LBS/IN**3 LAYER 3 THE LAYER IS A SAND i X AT THE TOP OF THE LAYER = 492.00 IN X AT THE BOTTOM OF TIE LAYER = 876.00 IN VARIATION OF SOIL MODULUS, k = .200E+02 LBS/IN**3 LAYER 4 THE LAYER IS A SAND X AT THE TOP OF THE LAYER = 876.00 IN X AT THE BOTTOM OF THE LAYER = 980.00 IN VARIATION OF SOIL MODULUS, k = . 125E+03 LBS/IN**3 DISTRIBUTION OF EFFECTIVE UNIT WEIGHT WITH DEPTH 8 POINTS X,IN WEIGHT,LBS/[N**3 .00 .58E-01 36.00 .58E-01 36.00 .60E-02 492-00 _60E-02 492.00 .30E-01 876.00 _30E-01 876.00 .40E-01 980.00 .40E-01 D I STR I BUT ION OF SIRENG[li PARAMETERS WITH DFP[1 I 8 POINTS X,1N C,LBS/[N**2 PHI,DEGREES E50 _00 .000E+00 10.000 ----- 36.00 .000E+00 10.000 ----- 36.00 .000E+0O 5.000 492.00 .000E+00 5.000 ---- 492.00 .000E+00 30.000 ----- 876.00 .000E+00 30.000 ----- 876.00 .000E+00 38.000 ----- 980.00 .000E+00 38.000 ----- FINITE D I FFEtENC'E PARAMETERS NUMBER OF PILE INCREMENTS = 80 TOLERANCE ON DETERMINATION OF DEFLECTIONS = .100E-02 IN MAXIMUM NUMBER OF ITERATIONS ALLOWED FOR PILE ANALYSIS = 100 MAXIMUM ALLOWABLE DEFLECTION = .20E+02 IN INPUT CODES OUTPT = I KCYCL = 0 KBC = 2 KPYOP = 0 INC = 2 rs rT Boeing 4-68 Bldg. 18-in augercast. concrete pile UNITS--ENGL OUTPUT INFORMATION ---------- *ss ---------- PILE LOADING CONDITION LATERAL LOAD AT PILE HEAD = .110E+05 LBS SLOPE AT PILE HEAD = 000E+00 IN/IN AXIAL LOAD AT PILE HEAD = .150E+06 LBS X DEFLECTION MOMENT TOTAL SHFAR SOIL FLEXURAL STRESS RESIST RIGIDITY IN IN LBS-IN LBS/IN**2 1.BS LBS/IN LBS-IN**2 .00 .496E+00 -.200E+07 .408E+04 .IIOE+05 .000E+00 .155E+12 24.00 .492E+00 -.174E+07 .362E+04 .107E+05 .252E+02 .155E+12 48.00 .482E+00 -.148E+07 .318E+04 .103E+05 .176E+02 .155E+12 72.00 .466E+00 -.124E+07 .276E+04 .984E+04 .194E+02 .155E+12 96.00 .446E+00 -.101E-+07 .235E+04 .932E+04 .238E+02 .155E+12 120.00 .422E+00 -.786E+06 .196E+04 .870E+04 .266E+02 .155E+12 144.00 .395E+00 -.581E+46 .161E+04 .806E+04 .272E+02 .155E+12 168.00 .366E+00 --391E+06 .127E+04 .740E+04 .276E+02 .155E+12 192.00 -336E+00 -.217E+06 .971E+03 .673E+04 .278E+02 .155E+12 216.00 .304E+00 -.587E+0S .694E+03 .606E+04 .278E+02 .155E+12 240.00 .273E+00 .835E+05 .738E+03 .539E+04 .277E+02 .155E+12 264.00 .242E+40 .210E+06 .958E+03 .473E+04 .273E+02 .155E+12 288.00 .211E+00 .320E+06 .115E+04 .408E+04 .266E+02 .155E+12 312.00 .182E+00 .415E+06 .132E+04 .345E+04 .258E+02 .155E+12 336.00 .154E+00 .494E+06 .146E+04 .284E+04 .248E+02 .155E+12 360.00 .128E+00 .559E+06 .157E+04 .226E+04 .235E+02 .155E+12 384.00 -104E+00 .611E+06 .166E+44 .171E+04 .221E+02 J55E+12 408.00 .827E-01 .649E+06 .172E+04 .120E+04 .205E+02 .155E+12 432.00 .636E-01 .674E+06 .177E+04 .727E+03 .187E+02 .155E+12 456.00 .469E-01 .689E+0b .180E+04 .301E+03 .167E+02 .155E+12 480.00 .328E-01 .694E+06 .180E+04 -.741E+42 .145E+02 .155E+12 504.00 .214E-01 .680E+06 .178E+04 --154E+04 .687E+02 .155E+12 528.00 .124E-01 .626E+06 .169E+04 -.292E+04 .458E+42 .155E+12 552.00 .574E-02 .546E+06 .154E+04 -.376E+04 -239E+02 .155E+12 576.00 .114E-02 .451E+06 .138E+44 -.410E+04 .521E+01 .155E+12 600.00 -.180E-02 .352E+06 .121E+44 -.405E+04 -.930E+0l .155E+12 624.00 -.341E-02 .259E+46 .104E+44 -.370E+04 -.192E+02 .155E+12 i ( 648.00 -.406E-02 176E+06 .900E+03 -.316E+04 -.248E+02 .155E+12 672.00 -.405E-02 108E+06 .780E+03 -.254E+04 267E+02 .155E+12 696.00 -.364E-02 .542E+05 .687E+03 -.191E+04 -_257E+02 155E+12 720.00 -.302E-02 156E+05 .619E+03 -.132E+-04 -.228E+02 .155E+12 744.00 -.234E-02 997E+04 .609E+03 821E+03 -.188E+02 .155E+12 768.00 -.170E-02 247E+05 .635E+03 422E+03 -.144E+02 .155E+12 792.00 -.114E-02 -.310E+05 .646E+03 127E+03 -.102E+02 .155E+12 816.00 -.699E-03 -_31SE+05 .647E+03 750E+02 -_660E+01 .155E+12 840.00 -.375E-03 -.280E+0S .641E+03 .198E+03 -.371E+01 .155E+12 864.00 -.154E-03 224E+05 .631E+03 _261E+03 159E+01 .155E+12 888.00 -.161E-04 -.154E+0S .619E+03 .316E+03 732E+00 .155E+12 912.00 .640E-04 797E+04 _606E+03 .285E+03 .315E+0l .155E+12 936.00 .114E-03 -.227E+04 .596E+03 .174E+03 .595E+01 .155E+12 960.00 .155E-03 .000E+00 .592E+03 .000E+00 .853E+01 .155E+12 COMPUIED LATERAL FORCE AT PILE HEAD = .11000E+05 LBS OOMPUIED SLOPE AT PILE HEAD = 23130E-17 IN/IN THE OVERALL MOMENT IMBALANCE _ -.354E-05 IN-LAS THE OVTRAL.I, LATERAL FORCE IMBALANCE _ -.258E-07 LBS OUTPUT SUMMARY PILE HEAD DEFLECTION = .496E+00 IN MAXIMUM BENDING MOMENT = -.200E+07 IN-LBS MAXIMUM TOTAL STRESS = .408E+04 LBS/IN**2 MAXIMUM SITAR FORCE _ .163E+05 LBS NO. OF ITERATIONS = 9 MAXIMUM DEFLECTION ERROR = .829E-03 IN SUMMARY TABLE LATERAL BOUNDARY AXIAL MAX. MAX_ LOAD CONDITION LOAD YT Si' MOMENT STRESS (LBS) BC2 (LBS) (1N) (IN/1N) (IN-LBS) (LBS/IN**2) .110E+05 .000E+00 . 150E+06 .496E+00 _231E-17 -.200E+07 .408E+04 Appendix D: Stormwater Pollution Prevention Plan Boeing Commercial Airplane Group Buyer Furnished Equipment (BFE) Building Building 4-68 Renton,Washington Stormwater Pollution Prevention Plan (SWPPP) Owner The Boeing Company PO Box 3707 MC 61-90 Seattle,WA 98124-2207 Contractor Lease Crutcher Lewis 107 Spring Street Seattle,WA 98104 Prepared by Water Tectonics, Inc 802 134th Street SW, Suite 110 Everett,WA 425 742-2062 SWPPP Preparation Date April 1, 2011 Updated 4114111 Approximate Project Construction Dates April — June 2011 — Utilities & Preload July— December 2011 —Building Construction Boeing—Renton Building 4-68 Stormwater Pollution Prevention Plan CERTIFICATION "I certify under penalty of law that this document and all attachments were prepared under my direction or supervision in accordance with a system designed to assure that qualified personnel gather and evaluate the information submitted. Based on my inquiry of the person or persons directly responsible for gathering the information, the information submitted is, to the best of my knowledge and belief, true accurate and complete. I am aware that there are significant penalties for submitting false information, including the possibility of fine and imprisonment for knowing violations." Operator: Lease Crutcher Lewis By: Name: Title: Date: SWPPP REVISIONS This SWPPP should be revised and updated to address changes in site conditions, new or revised regulatory requirements, and additional onsite stormwater pollution controls. All revisions to the original project SWPPP (No. 0) must be documented on the SWPPP Revision Documentation Form, which is shown below. The signature of this representative attests that information within this SWPPP revision is true and accurate to the best of their current understanding of the project. SWPPP Revision Documentation Table Number Date Company&Author Initials Reason for Revision(pg#of rev.) 0 -04.01.2011 Water Tectonics, Inc NA—Original Copy 1 04.14.11 Water Tectonics, Inc Updated to reflect LCL's comments 2 3 April 15,2011 2 Boeing—Renton Building 4-68 Stormwater Pollution Prevention Plan Table of Contents 1.0 Introduction ................... 5 2.0 Site Description..................................................................................................................7 2.1 Existing Conditions.....................................................................................................7 2.2 Proposed Construction Activities..............................................................................7 3.0 Construction Stormwater BMPs........... 8 3.1 The 12 BMP Elements....:........................ 8 3.1.1 Element#1 — Preserve Vegetation/Mark Clearing Limits.....................8 3.1.2 Element#2 — Establish Construction Access.........................................8 3.1.3 Element#3 — Control Flow Rates............................................................9 3.1.4 Element#4— Install Sediment Controls..................................................9 3.1.5 Element#5 — Stabilize Soils...................................................................10 3.1.6 Element#6— Protect Slopes..................................................................11 3.1.7 Element#7 — Protect Drain Inlets..........................................................11 3.1.8 Element#8— Stabilize Channels and Outlets ......................................11 3.1.9 Element#9— Control Pollutants.............................................................12 3.1.10 Element#10 — Control Dewatering........................................................13 3.1.11 Element#11 — Maintain BMPs...............................................................14 3.1.12 Element#12 — Manage the Project.......................................................17 3.2 Stormwater Management.........................................................................................19 4.0 Construction Phasing & BMP Implementation..............................................................20 5.0 Pollution Prevention Team..............................................................................................21 5.1 Roles and Responsibilities.......................................................................................21 5.2 Team Members.........................................................................................................21 6.0 Site Inspections and Monitoring.....................................................................................22 6.1 Site Inspection ..........................................................................................................22 6.1.1 Site Inspection Frequency......................................................................22 6.1.2 Site Inspection Documentation...............................................................22 6.2.1 Turbidity Sampling...................................................................................23 6.2.2 pH Sampling.............................................................................................24 7.0 Reporting and Recordkeeping .......................................................................................26 7.1 Recordkeeping..........................................................................................................26 7.1.1 Site Log Book...........................................................................................26 7.1.2 Records Retention...................................................................................26 7.1.3 Access to Plans and Records ................................................................26 7.1.4 Updating the SWPPP..............................................................................26 7.2 Reporting...................................................................................................................27 7.2.1 High Turbidity Phone Reporting.............................................................27 April 15,2011 3 Boeing—Renton Building 4-68 Stormwater Pollution Prevention Plan 7.2.2 Discharge Monitoring Reports................................................................27 7.2.3 Notification of Noncompliance................................................................27 7.2.4 Notice of Termination..............................................................................28 Appendix A— Permits & Authorizations Appendix B— Site Plans/Drawings Appendix C — Stormwater Calculations Appendix D — Construction BMPs Appendix E— Site Inspection Forms Apri 1 15,201 1 4 Boeing—Renton Building 4-68 Stormwater Pollution Prevention Plan 1.0 Introduction This Stormwater Pollution Prevention Plan (SWPPP) has been prepared as part of the NPDES —Stormwater General Permit requirements for the Boeing Renton BFE Building project located at 800 Logan Avenue North in Renton,Washington. This SWPPP was prepared using Ecology guidelines and is based on the requirements set forth in the construction Stormwater General Permit and Ecology's Stormwater Management Manual for Western Washington (SWMM-WW 2005). The NPDES—Stormwater General Permit(WAR124769) is included in Appendix A. The site is located at the southwestern quadrant of the Boeing Renton Facility Approximately 4.5 acres will be disturbed for the construction of a new 75,000sf building. This work will require removal and relocation of existing utilities, site preloading, demolition of the existing parking lot, excavation, grading, vertical building construction, installation of new utilities, and final stabilization with hardscape or landscape features. The purpose of this SWPPP is to describe the proposed construction activities and all temporary and permanent erosion and sediment control (TESC) measures, pollution prevention measures, inspection/monitoring activities, and recordkeeping that will be implemented during the proposed construction project. The objectives of the SWPPP are to: 1. Implement Best Management Practices(BMPs)to prevent erosion and sedimentation, and to identify, reduce, eliminate or prevent stormwater contamination and water pollution from construction activity. 2. Prevent violations of surface water quality, ground water quality, or sediment management standards. 3. Prevent, during the construction phase, adverse water quality impacts including impacts on beneficial uses of the receiving water by controlling peak flow rates and volumes of stormwater runoff at the Permittee's outfalls and downstream of the outfalls. This SWPPP has been customized for the Boeing Renton BFE Building project and is intended to be used with the project construction specifications and approved temporary erosion and sediment control (TESC)notes and drawings. Pertinent plans sheets and site drawings are included after this narrative. Information in this SWPPP is divided into the following seven sections: ■ Section 1 — INTRODUCTION. This section provides a summary description of the project, and the organization of the SWPPP document. ■ Section 2—SITE DESCRIPTION. This section provides a detailed description of the existing site conditions, proposed construction activities, and calculated stormwater flow rates for existing conditions and post-construction conditions. April 15,2011 5 Boeing—Renton Building 4-68 Stormwater Pollution Prevention Plan ■ Section 3—CONSTRUCTION BMPs. This section provides a detailed description of the BMPs to be implemented based on the 12 required elements of the SWPPP (SWMMWW 2005). ■ Section 4—CONSTRUCTION PHASING AND BMP IMPLEMENTATION. This section provides a description of the timing of the BMP implementation in relation to the project schedule. ■ Section 5— POLLUTION PREVENTION TEAM. This section identifies the appropriate contact names (emergency and non-emergency), monitoring personnel, and the onsite temporary erosion and sedimentation control inspector ■ Section 6— INSPECTION AND MONITORING. This section provides a description of the inspection and monitoring requirements such as the parameters of concern to be monitored, sample locations, sample frequencies, and sampling methods for all stormwater discharge locations from the site. ■ Section 7— RECORDKEEPING. This section describes the requirements for documentation of the BMP implementation, site inspections, monitoring results, and changes to the implementation of certain BMPs due to site factors experienced during construction. ■ Supporting documentation and standard forms are provided in the following Appendices: Appendix A— Permits&Authorizations Appendix B —Site Plans/Drawings Appendix C—Stormwater Calculations Appendix D—Construction BMPs Appendix E—Site Inspection Forms April 15,2011 6 Boeing—Renton Building 4-68 Stormwater Pollution Prevention Plan 2.0 Site Description 2.1 Existing Conditions The proposed site is located in the southwest portion of the Boeing Renton Facility located at 800 Logan Avenue North in Renton,Washington. A vicinity map is provided in Appendix B. The new building location is currently a parking lot west of Building 4-75. Site topography is flat Soils are a combination of fill materials and native glacial till. Runoff generated in the project area is collected in the existing storm drain system and drains to Lake Washington. The Boeing Renton Facility is bordered by the Cedar River to the West and Lake Washington to the north. 2.2 Proposed Construction Activities This project will proceed in two phases. The first phase consists of utility removal/relocation and site preloading. Utilities to be removed and or relocated include but are not limited to water, sewer, storm, electrical, natural gas, telephone and fiber optics. The majority of work in this phase involves trenching and backfill as well as placement of soil to preload the future building footprint. The second phase of the project consists of vertical building construction and associated landscape and hardscape features. The schedule and phasing of BMPs during construction is provided in Section 4.0. A summary of site run-off volumes for the two phases of construction are shown below. All stormwater calculations are provided in Appendix C. ■ Disturbed Soil 4.5 acres ■ CN 0.936 ■ 10 year 24-hour storm event volume 331,661 gallons ■ 100 year 24-hour storm event volume 450,602 gallons ■ Detention Tank(s) (if used) TBD April 15,2011 7 Boeing—Renton Building 4-68 Stormwater Pollution Prevention Plan 3.0 Construction Stormwater BMPs 3.1 The 12 BMP Elements The following section describes the BMPs to be implemented onsite to control sediment and stormwater. In addition alternate BMPs are included in Appendix C as a quick reference tool for the onsite inspector in the event the BMP(s) listed below are deemed ineffective or inappropriate during construction to satisfy the requirements set forth in the construction specifications. To avoid potential erasion and sediment control issues that may cause a water quality violation, the Certified Erosion and Sediment Control Lead will promptly initiate the implementation of one or more of the alternative BMPs listed in Appendix C after the first sign that existing BMPs are ineffective or failing. 3.1.1 Element#1 —Preserve Vegetation/Mark Clearing Limits To protect adjacent properties and to reduce the area of soil exposed to construction, the limits of construction will be clearly marked before land-disturbing activities begin. Trees that are to be preserved, as well as all sensitive areas and their buffers, shall be clearly delineated, both in the field and on the plans. In general, natural vegetation and native topsoil shall be retained in an undisturbed state to the maximum extent possible. Site specific BMPs: • Preserving Natural Vegetation (BMP C101) ■ High Visibility Plastic or Metal Fence (BMP C103) Alternate/Additional BMPs: • N/A 3.1.2 Element#2— Establish Construction Access Construction access or activities occurring on unpaved areas shall be minimized, yet where necessary,access points shall be stabilized to minimize the tracking of sediment onto public roads, and wheel washing, street sweeping, and street cleaning shall be employed to prevent sediment from entering state waters. All wash wastewater shall be controlled on site. If sediment is tracked off site, public roads shall be cleaned thoroughly at the end of each day as a minimum, or more frequently during wet weather. Sediment shall be removed from roads by shoveling or sweeping and be transported to a controlled sediment disposal area. April 15,2011 8 Boeing—Renton Building 4-68 Stormwater Pollution Prevention Plan Site specific BMPs: • Stabilized Construction Entrance (BMP C105) ■ Construction Road Stabilization (BMP C107) Alternate/Additional BMPs: ■ Tirewash (BMP C106) 3.1.3 Element#3—Control Flow Rates In order to protect the properties and waterways downstream of the project site, stormwater discharges from the site will be controlled. Stormwater detention facilities shall be constructed or mobilized as one of the first steps in grading. Detention facilities shall be functional prior to construction of site improvements. Site specific BMPs: ■ Portable Water Storage Tank(s) Altemate/Additional BMPs: ■ Interceptor Dike & Swale (BMP C200) ■ Water Bars (BMP C 203) ■ Check Dams (BMP C207) In general, dewatering from trenching activities will be routed to the sanitary sewer after treating to remove settleable solids. During the preload phase stormwater runoff will be directed to the storm drain system, assuming the runoff meets discharge requirements. Detention tanks may be required depending on season of work, phase of construction and water quality. Discharge rates of stormwater from the site will be controlled as necessary to meet local agency stormwater discharge requirements if necessary. 3.1.4 Element#4— Install Sediment Controls All stormwater runoff from disturbed areas shall pass through an appropriate sediment removal BMP before leaving the construction site or prior to being discharged to an infiltration facility. Site specific BMPs: • Straw Wattles (BMP C235) ■ Silt Fence (BMP C233) April 15,2011 9 Boeing—Renton Building 4-68 Stormwater Pollution Prevention Plan ■ Sediment Trap (BMP C240) Altemate/Additional BMPs: • Gravel Filter Berm (BMP C232) The following BMPs will be implemented as end-of-pipe sediment controls as required to meet permitted turbidity limits in the site discharge(s). Prior to the implementation of these technologies, sediment sources and erosion control and soil stabilization BMP efforts will be maximized to reduce the need for end-of-pipe sedimentation controls. ■ Infiltration/dispersal to a vegetated area of appropriate size ■ Geotextile sedimentation bag with outfall to ditch or swale for small volumes of localized dewatering • Sanitary sewer discharge only with prior approval of local sewer authority • Measures as discussed in Section 3.2. • Truck water off-site for legal disposal that does not pollute state waters 3.1.5 Element#5— Stabilize Soils Exposed and unworked soils shall be stabilized with the application of effective BMPs to prevent erosion throughout the life of the project. Site specific BMPs: ■ Mulching (BMP C121) ■ Plastic Covering (BMP C123) ■ Dust Control (BMP C140) Altemate/Additional BMPs: ■ Temporary & Permanent Seeding (BMP C120) ■ Early application of gravel base on areas to be paved The project site is located west of the Cascade Mountain Crest. As such, no soils shall remain exposed and unworked for more than 7 days during the dry season (May 1 to September 30) and 2 days during the wet season (October 1 to April 30). Regardless of the time of year, all soils shall be stabilized at the end of the shift before a holiday or weekend if needed based on weather forecasts. Specific soil stabilization measures for slopes are discussed next in Section 3.1.6. April 15,2011 10 Boeing—Renton Building 4-68 Stormwater Pollution Prevention Plan 3.1.6 Element#6—Protect Slopes All cut and fill slopes will be designed, constructed, and protected in a manner that minimizes erosion. In general, cut and fill slopes will be stabilized as soon as possible and soil stockpiles will be temporarily covered with plastic sheeting. All stockpiled soils shall be stabilized from erosion, protected with sediment trapping measures, and where possible, be located away from storm drain inlets, waterways, and drainage channels. Site specific BMPs: ■ Plastic Covering (BMP C123� Altemate/Additional BMPs: ■ N/A this site is flat and the only sloped area will be the preload stockpile during May/June 2011. 3.1.7 Element#7—Protect Drain Inlets All storm drain inlets and culverts made operable during construction shall be protected to prevent unfiltered or untreated water from entering the drainage conveyance system. However, the first priority is to keep all access roads clean of sediment and keep street wash water separate from entering storm drains until treatment can be provided. Storm Drain Inlet Protection (BMP C220) will be implemented for all drainage inlets and culverts that could potentially be impacted by sediment-laden runoff on and near the project site. Inlet protection devices shall be cleaned or removed and replaced when sediment has filled one third of the available storage (or as specified by the manufacturer) Site specific BMPs: ■ Storm Drain Inlet Protection (BMP C220) Altemate/Additional BMPs: ■ N/A- 3.1.8 Element#8—Stabilize Channels and Outlets Where site runoff is to be conveyed in channels, or discharged to a stream or some other natural drainage point, efforts will be taken to prevent downstream erosion. Site specific BMPs: ■ N/A run-off will be collected in the excavations and pumped to the designated sanitary/storm catchbasin. April 15,2011 l 1 Boeing—Renton Building 4-68 Stormwater Pollution Prevention Plan Alternate/Additional BMPs: ■ N/A The project site is located west of the Cascade Mountain Crest. As such, all temporary on-site conveyance channels shall be designed, constructed, and stabilized to prevent erosion from the expected peak 10 minute velocity of flow from a Type 1A, 10-year, 24-hour recurrence interval storm for the developed condition. Alternatively, the 10-year, 1-hour peak flow rate indicated by an approved continuous runoff simulation model, increased by a factor of 1.6, shall be used. Stabilization, including armoring material, adequate to prevent erosion of outlets, adjacent stream banks, slopes, and downstream reaches shall be provided at the outlets of all conveyance systems. 3.1.9 Element#9— Control Pollutants All pollutants, including waste materials and demolition debris, that occur onsite shall be handled and disposed of in a manner that does not cause contamination of stormwater. Good housekeeping and preventative measures will be taken to ensure that the site will be kept clean, well organized, and free of debris. If required, BMPs to be implemented to control specific sources of pollutants are discussed below. Vehicles, construction equipment, and/or petroleum product storage/dispensing: ■ All vehicles, equipment, and petroleum product storage/dispensing areas will be inspected regularly to detect any leaks or spills, and to identify maintenance needs to prevent leaks or spills. • On-site fueling tanks and petroleum product storage containers shall include secondary containment. ■ Spill prevention measures, such as drip pans, will be used when conducting maintenance and repair of vehicles or equipment. ■ In order to perform emergency repairs on site, temporary plastic will be placed beneath and, if raining, over the vehicle. ■ Surfaces shall be cleaned immediately following any discharge or spill incident. Chemical storage: ■ Any chemicals stored in the construction areas will conform to the appropriate source control BMPs listed in Volume IV of the Ecology stormwater manual. In Western WA, all chemicals shall have cover, containment, and protection provided on site, per BMP C153 for Material Delivery, Storage and Containment in SWMMWW 2005. ■ Application of agricultural chemicals, including fertilizers and pesticides, shall be conducted in a manner and at application rates that will not result in loss of chemical to stormwater runoff. Manufacturers' recommendations for application procedures and rates shall be followed. Excavation and tunneling spoils dewatering waste: Apri 1 15,2011 12 Boeing—Renton Building 4-68 Stormwater Pollution Prevention Plan ■ Dewatering BMPs and BMPs specific to the excavation and tunneling (including handling of contaminated soils)are discussed in Section 3.1.10. Demolition: ■ Dust released from demolished sidewalks, buildings, or structures will be controlled using Dust Control measures (BMP C140). ■ Storm drain inlets vulnerable to stormwater discharge carrying dust, soil, or debris will be protected using Storm Drain Inlet Protection (BMP C220 as described above in Section 3.1. 7). ■ Process water and slung resulting from sawcutting and surfacing operations will be prevented from entering the waters of the State by implementing Sawcutting and Surfacing Pollution Prevention measures(BMP C152). Concrete and grout: ■ Process water and slurry resulting from concrete work will be prevented from entering the waters of the State by implementing Concrete Handling measures(BMP C151). • A CO2 system or dry ice may be used to mitigate any high pH water that may be encountered. Sanitary wastewater: ■ Portable sanitation facilities will be firmly secured, regularly maintained, and emptied when necessary. Solid Waste: ■ Solid waste will be bagged or stored in lidded, clearly marked containers. Other: • Other BMPs will be administered as necessary to address any additional pollutant sources on site. The project does not require a Spill Prevention, Control, and Countermeasure (SPCC)Plan under the Federal regulations of the Clean Water Act(CWA); however the Boeing Renton facility has a SPCC. 3.1.10 Element#10—Control Dewatering All dewatering water from open cut excavation, tunneling, foundation work, trench, or underground vaults shall be discharged into a controlled conveyance system prior to discharge to a sediment trap, sediment pond or detention tank. Channels if used will be stabilized per Section 3.1.8. April 15,2011 13 Boeing—Renton Building 4-68 Stormwater Pollution Prevention Plan Clean, non-turbid dewatering water will not be routed through stormwater sediment ponds, and will be discharged to systems tributary to the receiving waters of the State in a manner that does not cause erosion, flooding, or a violation of State water quality standards in the receiving water. Dewatering of soils known to be free of contamination will trigger BMPs to trap sediment and reduce turbidity. Site specific sediment trapping BMPs to be implemented are discussed in Section 3.1.4. Additional BMPs that can be used for sediment trapping and turbidity reduction include the following: ■ Infiltration/dispersal to a vegetated area of appropriate size ■ Geotextile sedimentation bag with outfall to ditch or swale for small volumes of localized dewatering • Sanitary sewer discharge only with prior approval of local sewer authority ■ Measures as discussed in Section 3.2. ■ Truck water off-site for legal disposal that does not pollute state waters 3.1.11 Element#11 — Maintain BMPs All temporary and permanent erosion and sediment control BMPs shall be maintained and repaired as needed to assure continued performance of their intended function. ■ Maintenance and repair shall be conducted in accordance with each particular BMP's specifications. An abbreviated maintenance schedule is shown in Table 1. • Visual monitoring of the BMPs will be conducted at least once every calendar week and within 24 hours of any rainfall event that causes a discharge from the site. ■ If the site becomes inactive, and is temporarily stabilized, the inspection frequency will be reduced to once every month. Site specific BMPs: ■ Materials on Hand (BMP C150) All temporary erosion and sediment control BMPs shall be removed within 30 days after the final site stabilization is achieved or after the temporary BMPs are no longer needed. Trapped sediment shall be removed or stabilized on site. Disturbed soil resulting from removal of BMPs or vegetation shall be permanently stabilized. April 15,2011 14 Boeing—Renton Building 4-68 Stormwater Pollution Prevention Plan Table 1. BMP Maintenance and Inspection Schedule BMP tt BMP Name Recommended Maintenance Frequency C101 Preserving Natural Inspect flagged areas to make sure flagging has not been removed. If Vegetation tree roots have been exposed or injured,recover and/or seal them. Daily C103 Plastic or Metal If the fence has been damaged or visibility reduced,it shall be repaired Fence or replaced immediately and visibility restored. Daily Construction Quarry spalls shall be added if the pad is no longer in accordance with C105 Entrance the specifications. If the entrance fails to keep streets clean,install Daily wheel wash,sweep or wash streets if wash water can be collected. Wheel wash water shall not be discharged into a storm drain or the C106 Wheel Wash site's stormwater collection system. Use closed-loop recirculation,land Daily application,or discharge to sanitary sewer(by permit). C107 Const. Road Inspect stabilized areas regularly,especially after large storm events. Daily Stabilization Add rock(hog fuel),gravel,etc.as needed to maintain a stable surface Temporary& Re-seed areas failing to establish 80%cover within one month(during Inspect to C120 Permanent growing season). If re-seeding is ineffective,use sodding or ensure growth Seeding nets/blankets. Eroded areas shall be corrected and re-planted. weekly C121 Mulching Maintain specified thickness of mulch cover. Eroded areas must be Weekly and corrected and re-mulched. Drainage problems must be corrected. following storms C123 Plastic Covering Replace torn sheets and repair open seams. Replace deteriorated Weekly plastic sheets. Dispose of plastic when no longer needed. C140 Dust Control Re-apply dust control measures as necessary to keep dust to a Daily during dry minimum. weather C150 Materials on Hand Re-stock erosion control materials as needed Weekly Check containers and eco-pans for holes or leaks make sure all concrete Daily when C151 Concrete Handling pouring wash out is in an impervious contained area concrete Sawcutting and Continually monitor operations to determine if slurry could enter . Should a violation arise,immediately implement Continuously surface waters C152 Surfacing Pollution during preventative measures such as berms,barriers,secondary containment Prevention operations and/or vacuum trucks Material Delivery Check to see that all products are stored correctly(secondary C153 Storage& containment,fire protection etc.)Make sure adequate spill clean-up Weekly Containment materials are on hand if not restock. C200 Interceptor Dike& Inspect to insure structural integrity. Repair as needed Weekly and Swale following storms C220 Storm Drain Inlet Replace clogged filter fabric. Clean sediment from stone filters. Do not Weekly and Protection wash collected sediments into storm drains—remove to soil stockpile. following storms C232 Gravel Filter Berm Remove sediment and replace filter material as needed Weekly and following storms Repair damaged fencing immediately. Intercept concentrated flows and Weekly and C233 Silt Fence reroute. Remove sediment accumulations at 6-inches. Replace E deteriorated fencing material. Properly dispose of used fencing. Following storms April 15,2011 15 Boeing—Renton Building 4-68 Stormwater Pollution Prevention Plan Inspect wattles to ensure that they are in contact with soil and C235 Straw Wattles thoroughly entrenched.Intercept concentrated flows and reroute. Weekly and Repair and/or re-stake as needed,replace deteriorated material. following storms C240 Sediment Trap Remove sediment when it reaches a depth of one foot. Repair damage Weekly and to trap embankments and slopes. following storms C250 Chemical Follow monitoring requirements provided in Ecology's Use level As required Treatment Designation. Check system daily when operating. Remove sediment from retention Stormwater Daily when C251 Filtration Pond/backwash pond to maintain adequate volume. Clean and/or operating replace screed,bag and fiber filters as determined by flow restriction April 15,2011 16 Boeing—Renton Building 4-68 Stormwater Pollution Prevention Plan 3.1.12 Element#12—Manage the Project Erosion and sediment control BMPs for this project have been designed based on the following principles: ■ Design the project to fit the existing topography, soils, and drainage patterns. ■ Emphasize erosion control rather than sediment control. ■ Minimize the extent and duration of the area exposed. ■ Keep runoff velocities low. ■ Retain sediment on site. ■ Thoroughly monitor site and maintain all ESC measures. ■ Schedule major earthwork during the dry season. Phasing of Construction: ■ The construction project is being phased to the extent practicable in order to prevent soil erosion, and, to the maximum extent possible,the transport of sediment from the site during construction. ■ Revegetation of exposed areas and maintenance of that vegetation shall be an integral part of the clearing activities during each phase of construction, per the Scheduling BMP (C 162). Seasonal Work Limitations: From October 1 through April 30, clearing, grading, and other soil disturbing activities shall only be permitted if shown to the satisfaction of the local permitting authority that silt-laden runoff will be prevented from leaving the site through a combination of the following: ■ Site conditions including existing vegetative coverage, slope, soil type, and proximity to receiving waters; and ■ Limitations on activities and the extent of disturbed areas; and ■ Proposed erosion and sediment control measures. Based on the information provided and/or local weather conditions, the local permitting authority may expand or restrict the seasonal limitation on site disturbance. The following activities are exempt from the seasonal clearing and grading limitations: ■ Routine maintenance and necessary repair of erosion and sediment control BMPs; • Routine maintenance of public facilities or existing utility structures that do not expose the soil or result in the removal of the vegetative cover to soil; and ■ Activities where there is 100 percent infiltration of surface water runoff within the site in approved and installed erosion and sediment control facilities. April 15,201 l 17 Boeing—Renton Building 4-68 Stormwater Pollution Prevention Plan Coordination with Utilities and Other Jurisdictions: Care has been taken to coordinate with utilities, other construction projects, and the local jurisdiction in preparing this SWPPP and scheduling the construction work. Inspection and Monitoring: ■ All BMPs shall be inspected, maintained, and repaired as needed to assure continued performance of their intended function. Site inspections shall be conducted by a person who is knowledgeable in the principles and practices of erosion and sediment control. This person has the necessary skills to: ■ Assess the site conditions and construction activities that could impact the quality of stormwater, and ■ Assess the effectiveness of erosion and sediment control measures used to control the quality of stormwater discharges. ■ A Certified Erosion and Sediment Control Lead shall be on-site or on-call at all times. ■ Whenever inspection and/or monitoring reveals that the BMPs identified in this SWPPP are inadequate, due to the actual discharge of or potential to discharge a significant amount of any pollutant, appropriate BMPs or design changes shall be implemented as soon as possible. Maintaining an Updated Construction SWPPP: ■ This SWPPP shall be retained on-site or within reasonable access to the site. ■ The SWPPP shall be modified whenever there is a change in the design, construction, operation, or maintenance at the construction site that has, or could have, a significant effect on the discharge of pollutants to waters of the state. ■ The SWPPP shall be modified if, during inspections or investigations conducted by the owner/operator, or the applicable local or state regulatory authority, it is determined that the SWPPP is ineffective in eliminating or significantly minimizing pollutants in stormwater discharges from the site. The SWPPP shall be modified as necessary to include additional or modified BMPs designed to correct problems identified. Revisions to the SWPPP shall be completed within seven (7)days following the inspection. April 15,2011 18 Boeing—Renton Building 4-68 Stormwater Pollution Prevention Plan 3.2 Stormwater Management Site stormwater will in the excavation will gravity flow to a collection trench and discharge to the designated discharge location (stormwater run-off to storm system, groundwater to sanitary sewer). If work extends into the wet season (past September 15th)detention tanks may be necessary to proceed through the winter. No discharge to the sanitary sewer will occur without appropriate authorization from Boeing and/or the local sewer district. Additional considerations for stormwater management include: • A clean pump point will be installed and relocated as work progresses. • Water from the clean pump point will be dispersed to vegetated areas adjacent to the work area in a manner that does not cause erosion or sheet flow back to disturbed areas. • If the water encountered in the trench is highly turbid, chitosan gel floc logs may be used inline between the pump and detention tank to improve water clarity. This treatment method is only applicable for water that will be discharged to the sanitary sewer. Gel Floc logs are not approved for use where discharge will be to surface waters of the State (storm system, ditch, creek, stream, lake, wetland). • If the pH is higher than allowable discharge limits (due to contact with fresh concrete) dry ice or CO2 may be used to reduce the pH to allowable levels (BMP C252). • Clean stormwater from areas surrounding the excavation/work area should be diverted around the disturbed areas with sand bag berms or equivalent. April 15,2011 — 19 Boeing—Renton Building 4-68 Stormwater Pollution Prevention Plan 4.0 Construction Phasing & BMP Implementation The BMP implementation schedule will be driven by the construction schedule. The following provides a sequential list of the proposed construction schedule milestones and the corresponding BMP implementation schedule. The project site is located west of the Cascade Mountain Crest. As such, the dry season is considered to be from May 1 to September 30 and the wet season is considered to be from October 1 to April 30. Estimated Dates of Construction April 2011 — December 2011 Mobilize to site—Implement TESC Measures April 2011 High Visibility Plastic or Metal Fence(BMP C103), Storm Drain Inlet Protection(BMP C220) Utility Relocation April— May Plastic Covering(BMP C123), Dust Control (BMP C140), Concrete Handling measures(BMP C151), Materials on Hand (BMP C150), Perform maintenance on all installed BMPs. Site Preload May—June Plastic Covering(BMP C123), Dust Control (BMP C140), Materials on Hand(BMP C150), Perform maintenance on all installed BMPs. Building Construction July- December Materials on Hand (BMP C150), Perform maintenance on all installed BMPs. April 15,201 1 20 Boeing—Renton Building 4-68 Stormwater Pollution Prevention Plan 5.0 Pollution Prevention Team 5.1 Roles and Responsibilities The pollution prevention team consists of personnel responsible for implementation of the SWPPP, including the following: ■ Contractor-company responsible for day to day operation of the construction site ■ Owner Contact- individual that is the site owner or representative of the site owner to be contacted in the case of an emergency ■ Ecology Contact- individual to be contacted at Ecology in case of emergency. ■ Certified Erosion and Sediment Control Lead (CESCL)-primary contractor contact, responsible for site inspections(BMPs, visual monitoring, sampling, etc.); to be called upon in case of failure of any ESC measures. 5.2 Team Members Names and contact information for those identified as members of the pollution prevention team are provided in the following table. Title Name(s) Phone Number Lease Crutcher Lewis (206)622-0500 Contractor Don Simon, Superintendent (206)255-1683 Don Lane, Project Manager 206 423-3770 NW Regional Office - Inspection Ecology Contact Ken Waldo (construction inspection) Greg Stegman industrial permit) (425)649-7000 Boeing Bill Rockwell (Overall primary) (206)679-3825 Owner Contact Chad Budworth (EHS primary) (425)237-1513 Doris Turner EHS seconds 425 965-2304 Contractor's CESCL Lease Crutcher Lewis Keith Johnson 206 730-0915 April 15,2011 21 Boeing—Renton Building 4-68 Stormwater Pollution Prevention Plan 6.0 Site Inspections and Monitoring Monitoring includes visual inspection, monitoring for water quality parameters of concern and documentation of the inspection and monitoring findings in a site log book. A site log book will be maintained for all on-site construction activities and will include: ■ A record of the implementation of the SWPPP and other permit requirements; • Site inspections ■ Stormwater quality monitoring For convenience, the inspection form and water quality monitoring forms included in this SWPPP include the required information for the site log book. This SWPPP may function as the site log book if desired, or the forms may be separated and included in a separate site log book. However, if separated, the site log book but must be maintained on-site or within reasonable access to the site and be made available upon request to Ecology or the local jurisdiction. The City of Renton may require additional monitoring based on site and soil conditions. These will be met in addition to the Ecology requirements. When possible a monitoring event may satisfy both the City and Ecology requirements. 6.1 Site Inspection All BMPs will be inspected, maintained, and repaired as needed to assure continued performance of their intended function. The inspector will be a Certified Erosion and Sediment Control Lead (CESCL) per BMP C160. The name and contact information for the CESCL is provided in Section 5 of this SWPPP. Site inspection will occur in all areas disturbed by construction activities and at all stormwater discharge points. Stormwater will be examined for the presence of suspended sediment, turbidity, discoloration, and oily sheen. The site inspector will evaluate and document the effectiveness of the installed BMPs and determine if it is necessary to repair or replace any of the BMPs to improve the quality of stormwater discharges. All maintenance and repairs will be documented in the site log book or forms provided in this document. All new BMPs or design changes will be documented in the SWPPP as soon as possible. 6.1.1 Site Inspection Frequency Site inspections will be conducted at least once a week and within 24 hours following any rainfall event which causes a discharge of stormwater from the site. For sites with temporary stabilization measures, the site inspection frequency can be reduced to once every month. 6.1.2 Site Inspection Documentation The site inspector will record each site inspection using the site log inspection forms provided in Appendix F. The site inspection log forms may be separated from this SWPPP document, but April 15,2011 22 Boeing—Renton Building 4-68 Stormwater Pollution Prevention Plan will be maintained on-site or within reasonable access to the site and be made available upon request to Ecology or the local jurisdiction. During construction site water will be collected in the excavation. If needed a stormwater treatment system will be implemented for turbidity and pH reduction. Turbidity and pH values will be measured at the point of discharge to the two points shown on the TESC plans. Additional monitoring points may be added if necessary. All measurements will be read with approved field meters or automatically logged if using a treatment system. All measurements will be recorded and will be made available to the owner, City or Renton and/or state stormwater inspectors upon request. 6.2.1 Turbidity Sampling Ecology requires turbidity sampling on all sites disturbing one or more acres. Sampling will be conducted as follows: Sampling will occur at least once every calendar week when stormwater is discharging from the site. When there is no discharge during a calendar week, sampling is not required Sampling is not required outside of normal working hours or during unsafe conditions. If a permittee is not able to sample during a monitoring period, the Discharge Monitoring report(DMR) shall include a brief explanation. Sampling is required at all discharge points where stormwater is discharged off site (see attached plans for monitoring locations). Turbidity shall be read with a calibrated turbidimeter and read as nephelometric turbidity units (ntu). •3 Readings will be summarized on the Inspection Report which will be kept in the Site Log Book Ecology has set two benchmarks for turbidity, 25 ntu and 250 ntu. Table 2 explains the necessary actions required based on the measured turbidity value. These actions are taken from Section S4.C.5 of the Construction Stormwater General Permit. April 15,2011 23 Boeing—Renton Building 4-68 Stormwater Pollution Prevention Plan Table 2. Turbidity/Transparency Values& Necessary Actions NTU CM Corrective Action Necessary 0—25 ntu .•. 25 NTU is Ecology's Bench Mark— No Corrective Action Necessary •� Record value(s)on Inspection Sheet and file in Site Log Book 26—249 ntu Review SWPPP for compliance and make appropriate revisions. Fully implemdnt appropriate source control and/or treatment BMPs as soon as possible but within 10 days of the date of the benchmark exceedance. Document BMP implementation and maintenance in the Site Log Book. Notify Ecology by phone within 24-hours of reading. ee Review SWPPP for compliance and make appropriate revisions. Fully implement appropriate source control and/or treatment BMPs* as soon as possible but within 10 days of the date of the exceeded benchmark. Document BMP implementation and maintenance in the site log book. 250 ntu or ❖ Continue to sample discharges daily until: more • Turbidity is 25 NTU or less; transparency is 31 cm or greater • The CESCL has demonstrated compliance with the water quality standard for turbidity: • No more than 5NTU above background if background is less than 50 NTU • No more than 10%over background turbidity if background is 50 NTU or greater • The discharge stops or is eliminated *Additional treatment BMPs to be considered will include, but are not limited to, off-site treatment, infiltration, filtration and chemical treatment. 6.2.2 pH Sampling This site is subject to pH monitoring because significant concrete work(>1000cy of poured or recycled concrete)will occur and/or engineered soils will be used on the project. Approximately 22,000 cy of concrete will be used on this site. pH monitoring will be performed as follows: During the pH monitoring period (see Table 3), pH sampling and analysis will occur weekly. Monitoring will be most critical from July— December 2011. Sampling will occur in the sediment trap/pond(s) or other locations that receive stormwater fun-off from the area of concrete/engineered soils prior to discharge to surface waters. April 15,2011 24 Boeing—Renton Building 4-68 Stormwater Pollution Prevention Plan pH benchmark is 8.5 Standard Units. Any time sampling indicates that the pH is higher than 8.5 the following will occur: • Prevent high pH water from entering storm system or surface waters • If necessary adjust or neutralize the high pH water with CO2 sparging or dry ice. The permittee shall obtain written approval for the use of any other chemical treatment pH analysis will be performed on site with a calibrated pH meter, pH test kit or wide range pH indicator paper. s Readings will be summarized on the Inspection Report which will be kept in the Site Log Book Table 3. pH Monitoring Period as Dictated by Source Monitoring will begin when the first significant concrete work is Significant Concrete exposed to precipitation and continue weekly until stormwater pH is 8.5 or less Monitoring will begin when the soil amendments are first Engineered Soils exposed to precipitation and shall continue until the amended area is fully stabilized (permanent stabilization - paved) April 15,2011 25 Boeing—Renton Building 4-68 Stormwater Pollution Prevention Plan 7.0 Reporting and Recordkeeping 7.1 Recordkeeping 7.1.1 Site Log Book A site log book will be maintained for all on-site construction activities and will include: • A record of the implementation of the SWPPP and other permit requirements; • Site inspections; and, • Stormwater quality monitoring. For convenience,the inspection form and water quality monitoring forms included in this SWPPP include the required information for the site log book. 7.1.2 Records Retention Records of all monitoring information (site log book, inspection reports/checklists, etc.), this Stormwater Pollution Prevention Plan, and any other documentation of compliance with permit requirements will be retained during the life of the construction project and for a minimum of three years following the termination of permit coverage in accordance with permit condition S5.C. 7.1.3 Access to Plans and Records The SWPPP, General Permit, Notice of Authorization letter, and Site Log Book will be retained on site or within reasonable access to the site and will be made immediately available upon request to Ecology or the City of Renton. A copy of this SWPPP will be provided to Ecology within 14 days of receipt of a written request for the SWPPP from Ecology. Any other information requested by Ecology will be submitted within a reasonable time. A copy of the SWPPP or access to the SWPPP will be provided to the public when requested in writing in accordance with permit condition S5.G. 7.1.4 Updating the SWPPP In accordance with Conditions S3, S4.13, and S9.6.3 of the General Permit, this SWPPP will be modified if the SWPPP is ineffective in eliminating or significantly minimizing pollutants in stormwater discharges from the site or there has been a change in design, construction, operation, or maintenance at the site that has a significant effect on the discharge, or potential for discharge, of pollutants to the waters of the State. The SWPPP will be modified within seven days of determination based on inspection(s)that additional or modified BMPs are necessary to correct problems identified, and an updated timeline for BMP implementation will be prepared. April 15,2011 26 Boeing—Renton Building 4-68 Stormwater Pollution Prevention Plan 7.2 Reporting 7.2.1 High Turbidity Phone Reporting Any time sampling indicates turbidity is 250 ntu or greater(transparency 6cm or less)the permittee shall notify the appropriate Ecology regional office by phone within 24 hours. 7.2.2 Discharge Monitoring Reports Water quality sampling results will be submitted to Ecology monthly on Discharge Monitoring Report(DMR)forms in accordance with permit condition S5.13. The DMR will be prepared by Boeing 737 AP Environmental Affairs staff and submitted electronically via the Ecology's WebDMR website within 15 days of the end of the month (i.e. Sept report due Oct 15''). If there was no discharge during a given monitoring period, the form will be submitted with the words "no discharge"entered in place of the monitoring results. If a benchmark was exceeded, a brief summary of inspection results and remedial actions taken will be included. If sampling could not be performed during a monitoring period, a DMR will be submitted with an explanation of why sampling could not be performed. 7.2.3 Notification of Noncompliance If any of the terms and conditions of the permit are not met, and it causes a threat to human health or the environment, the following steps will be taken in accordance with permit section S5.F: In the event of a noncompliance issue the Boeing Construction Manager shall be notified who will then notify site Environmental Affairs. Environmental Affairs will be the entity to contact Ecology in the event of a failure to comply. Immediate action will be taken to control the noncompliance issue and to correct the problem. If applicable, sampling and analysis of any noncompliance will be repeated immediately and the results submitted to Ecology within five (5)days of becoming aware of the violation. A detailed written report describing the noncompliance will be submitted to Ecology within five (5)days, unless requested earlier by Ecology. Any time turbidity sampling indicates turbidity is 250 nephelometric turbidity units (NTU)or greater or water transparency is 6 centimeters or less, the Ecology regional office will be notified by phone within 24 hours of analysis as required by permit condition S5.A(see Section 5.0 of this SWPPP for contact information). In accordance with permit condition S4.F.6.b, the Ecology regional office will be notified if chemical treatment other than CO2 sparging is planned for adjustment of high pH water(see Section 5.0 of this SWPPP for contact information). Permit Application and Changes In accordance with permit condition S2.A, a complete application form will be submitted to Ecology and the appropriate City of Renton (if applicable)to be covered by the General Permit. April 15,2011 27 Boeing—Renton Building 4-68 Stormwater Pollution Prevention Plan 7.2.4 Notice of Termination The site is eligible for termination when the site has undergone final stabilization, all temporary BMPs have been removed and all stormwater discharges associated with construction activities have been eliminated. The site is also eligible fortermination when any remaining unstabilized portions of the project have been sold or transferred and the permittee no longer has operational control of the construction activity. Once these criteria are met a completed Notice of Termination form shall be completed, signed and submitted to: Department of Ecology Water Quality Program—Construction Stormwater PO Box 47696 Olympia, WA 98504— 7696 The termination is effective on the date that the NOT form was received by Ecology, unless the Permittee is notified otherwise by Ecology within 30 days. April 15,2011 28 Appendix A — Permits & Authorizations Appendix B — Site Plans/Drawings Vicinity Map C kve Hil 520 NE 24.h 53 r Medina Samma 7, sh Bellevue Beaux Arts village ti J, r r �. Mercer oLMai% Island Eastgate so"ir/ t .� :z Meice` "kdk j 2 0 � €stand �j u G 509 s Newcastle Issaquah 99 900 99 900 Bryn Mawr Seola Beach Boulevard Park Skyway ] East Ren:vf• 509 Riverton Renton Highlands BUflen Heights13 Tukwila SF�enror> aP�P vettey `r Normandy Park `' v sF a SeaTac SE 208th St Des Moines Included by reference and considered part of this SWPPP. The project drawings will be kept onsite in the construction job trailer BOEING COMMERCIAL AIRPLANE GROUP BUYER FURNISHED EQUIPMENT (BFE) BUILDING VICINITY SITE MAR LEGAL DESCRIPTION :,R01C7 TEAM DRAWING INDEX � - - I „ He- •r VIE-N T i i- - - _ . f _ 1,) -t y Ll;1pl rK t - . ,.[.rn i, •r.wa .; rra, ` r-a i i [1 W. iiI- A SCOPE OF 1001ORK, AREA.ti"•AP CODE SUMMARY r i - '[la �- [ �� — � 1-�a cI !�■ `II if it Q N.A::ilt rlll �wS coal N P , /�� •� -�^ ?II ICE fyH AQ � Specifically: RTN-YD-EC157D Temporary Erosion & Sedimentation Control Plan RTN-YD-EC158D Temporary Erosion & Sedimentation Control Plan Appendix C - Stormwater Calculations Boeing Renton BFE Building Estimated Stormwater Volumes Generated Based on Landuse and Storm Events Acres Sq.Ft Disturbed Area F-4.501 196020 Curve# %of site area Product Impervious 098 60% 117,612 115,260 Open Dirt 0 87 40% 78,408 68,215 Composite CN 0,936 196,020 183,475 Soil Type B Run-off Curve# 0 936 Precipitation Rates inches ft cf gallons of run-off 2-yr 24-hour storm 200 0 17 30,579 228,732 10yr 24-hour storm 290 024 44,340 331,661 25-yr24-hour storm 3.40 0.28 51,985 388,844 100-yr 24-hour storm 394 0 33 60,241 450,602 Estimated Average Monthly Rainfall-Seatac Monthly Volume Estimated Monthly Stormwater Volumes Month Inches Gallons Jan 5.38 615,289 800,000 -- -- Feb 3,99 456,325 700,000 Mar 3,54 404,855 600.000 Apr 2,33 266,473 May 1.7 194,422 K0,000 0 Jun 1.5 171,549 400,000 Jul 0.76 86,918 300,000 Aug 1,14 130,377 200.000 Sept 1,88 215,008 Oct 3.23 369,402 100.000 Nov 5.83 666,753 0 Dec 5.91 b- 675,9H03 Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Annual 37A9 4,253,2 Appendix D — Construction BMPs Chapter 4 - Standards and Specifications for Best Management Practices Best Management Practices (BMPs)are defined as schedules of activities, prohibitions of practices, maintenance procedures, and structural and/or managerial practices, that when used singly or in combination, prevent or reduce the release of pollutants to waters of Washington State. This chapter contains standards and specifications for temporary BMPs to be used as applicable during the construction phase of a project. Section 4.1 contains the standards and specifications for Source Control BMPs. Section 4.2 contains the standards and specifications for Runoff Conveyance and Treatment BMPs. The standards for each individual BMP are divided into four sections: 1. Purpose 2. Conditions of Use 3. Design and Installation Specifications 4. Maintenance Standards Note that the"Conditions of Use"always refers to site conditions. As site conditions change, BMPs must be changed to remain in compliance. Information on streambank stabilization is available in the Integrated Streambank Protection Guidelines, Washington State Department of Fish and Wildlife, 2000. February 2005 Volume 11-Construction Stormwater Pollution Prevention 4-1 4.1 Source Control BMPs BMP C101: Preserving Natural Vegetation Purpose The purpose of preserving natural vegetation is to reduce erosion wherever practicable. Limiting site disturbance is the single most effective method for reducing erosion. For example,conifers can hold up to about 50 percent of all rain that falls during a storm. Up to 20-30 percent of this rain may never reach the ground but is taken up by the tree or evaporates. Another benefit is that the rain held in the tree can be released slowly to the ground after the storm. Conditions of Use • Natural vegetation should be preserved on steep slopes, near perennial and intermittent watercourses or swales, and on building sites in wooded areas. • As required by local governments. Design and Natural vegetation can be preserved in natural clumps or as individual Installation trees, shrubs and vines. Specifications The preservation of individual plants is more difficult because heavy equipment is generally used to remove unwanted vegetation. The points to remember when attempting to save individual plants are: • Is the plant worth saving? Consider the location,species, size,age, vigor,and the work involved. Local governments may also have ordinances to save natural vegetation and trees. • Fence or clearly mark areas around trees that are to be saved. It is preferable to keep ground disturbance away from the trees at least as far out as the dripline. Plants need protection from three kinds of injuries: • Construction Equipment-This injury can be above or below the ground level. Damage results from scarring,cutting of roots, and compaction of the soil. Placing a fenced buffer zone around plants to be saved prior to construction can prevent construction equipment injuries. • Grade Changes -Changing the natural ground level will alter grades, which affects the plant's ability to obtain the necessary air, water, and minerals. Minor fills usually do not cause problems although sensitivity between species does vary and should be checked. Trees can tolerate fill of 6 inches or less. For shrubs and other plants, the fill should be less. When there are major changes in grade, it may become necessary to supply air to the roots of plants. This can be done by placing a layer of gravel and a tile system over the roots before the fill is made. A tile 4-2 Volume 11—Construction Stormwater Pollution Prevention February 2005 system protects a tree from a raised grade. The tile system should be laid out on the original grade leading from a dry well around the tree trunk. The system should then be covered with small stones to allow - air to circulate over the root area. Lowering the natural ground level can seriously damage trees and shrubs. The highest percentage of the plant roots are in the upper 12 inches of the soil and cuts of only 2-3 inches can cause serious injury. To protect the roots it may be necessary to terrace the immediate area around the plants to be saved. If roots are exposed,construction of retaining walls may be needed to keep the soil in place. Plants can also be preserved by leaving them on an undisturbed, gently sloping mound. To increase the chances for survival, it is best to limit grade changes and other soil disturbances to areas outside the dripline of the plant. • Excavations- Protect trees and other plants when excavating for drainfields,power, water,and sewer lines. Where possible, the trenches should be routed around trees and large shrubs. When this is not possible, it is best to tunnel under them. This can be done with hand tools or with power augers. If it is not possible to route the trench around plants to be saved,then the following should be observed: Cut as few roots as possible. When you have to cut,cut clean. Paint cut root ends with a wood dressing like asphalt base paint. Backfill the trench as soon as possible. Tunnel beneath root systems as close to the center of the main trunk to preserve most of the important feeder roots. Some problems that can be encountered with a few specific trees are: • Maple, Dogwood, Red alder, Western hemlock,Western red cedar, and Douglas fir do not readily adjust to changes in environment and special care should be taken to protect these trees. • The windthrow hazard of Pacific silver fir and madronna is high,while that of Western hemlock is moderate. The danger of windthrow increases where dense stands have been thinned. Other species(unless they are on shallow,wet soils less than 20 inches deep)have a low windthrow hazard. • Cottonwoods, maples,and willows have water-seeking roots. These can cause trouble in sewer lines and infiltration fields. On the other hand,they thrive in high moisture conditions that other trees would not. • Thinning operations in pure or mixed stands of Grand fir, Pacific silver fir, Noble fir, Sitka spruce, Western red cedar,Western hemlock, February 2005 Volume 11—Construction Stormwater Pollution Prevention 4-3 Pacific dogwood, and Red alder can cause serious disease problems. Disease can become established through damaged limbs, trunks, roots, and freshly cut stumps. Diseased and weakened trees are also susceptible to insect attack. Maintenance . Inspect flagged and/or fenced areas regularly to make sure flagging or Standards fencing has not been removed or damaged. If the flagging or fencing has been damaged or visibility reduced, it shall be repaired or replaced immediately and visibility restored. • If tree roots have been exposed or injured, "prune" cleanly with an appropriate pruning saw or lopers directly above the damaged roots and recover with native soils. Treatment of sap flowing trees (fir, hemlock, pine, soft maples) is not advised as sap forms a natural healing barrier. 4-4 Volume 11-Construction Stormwater Pollution Prevention February 2005 BMP C102: Buffer Zones Purpose An undisturbed area or strip of natural vegetation or an established suitable planting that will provide a living filter to reduce soil erosion and runoff velocities. Conditions of Use Natural buffer zones are used along streams, wetlands and other bodies of water that need protection from erosion and sedimentation. Vegetative buffer zones can be used to protect natural swales and can be incorporated into the natural landscaping of an area. Critical-areas buffer zones should not be used as sediment treatment areas. These areas shall remain completely undisturbed. The local permitting authority may expand the buffer widths temporarily to allow the use of the expanded area for removal of sediment. Design and . Preserving natural vegetation or plantings in clumps,blocks,or strips Installation is generally the easiest and most successful method. Specifications Leave all unstable steep slopes in natural vegetation. • Mark clearing limits and keep all equipment and construction debris out of the natural areas. Steel construction fencing is the most effective method in protecting sensitive areas and buffers. Alternatively, wire-backed silt fence on steel posts is marginally effective. Flagging alone is typically not effective. • Keep all excavations outside the dripline of trees and shrubs. • Do not push debris or extra soil into the buffer zone area because it will cause damage from burying and smothering. • Vegetative buffer zones for streams, lakes or other waterways shall be established by the local permitting authority or other state or federal permits or approvals. Maintenance . Inspect the area frequently to make sure flagging remains in place Standards and the area remains undisturbed. February 2005 Volume Il-Construction Stormwater Pollution Prevention 4-5 BMP C103: High Visibility Plastic or Metal Fence Purpose Fencing is intended to: (1) restrict clearing to approved limits; (2) prevent disturbance of sensitive areas, their buffers, and other areas required to be left undisturbed; (3) limit construction traffic to designated construction entrances or roads; and, (4) protect areas where marking with survey tape may not provide adequate protection. Conditions of Use To establish clearing limits,plastic or metal fence may be used: • At the boundary of sensitive areas, their buffers, and other areas required to be left uncleared. • As necessary to control vehicle access to and on the site. Design and . High visibility plastic fence shall be composed of a high-density Installation polyethylene material and shall be at least four feet in height. Posts Specifications for the fencing shall be steel or wood and placed every 6 feet on center(maximum)or as needed to ensure rigidity. The fencing shall be fastened to the post every six inches with a polyethylene tie. On long continuous lengths of fencing, a tension wire or rope shall be used as a top stringer to prevent sagging between posts. The fence color shall be high visibility orange. The fence tensile strength shall be 360 lbs./ft. using the ASTM D4595 testing method. • Metal fences shall be designed and installed according to the manufacturer's specifications. • Metal fences shall be at least 3 feet high and must be highly visible. • Fences shall not be wired or stapled to trees. Maintenance • If the fence has been damaged or visibility reduced, it shall be Standards repaired or replaced immediately and visibility restored. 4-6 Volume 11—Construction Stormwater Pollution Prevention February 2005 BMP C104: Stake and Wire Fence Purpose Fencing is intended to: (1)restrict clearing to approved limits; (2) prevent disturbance of sensitive areas, their buffers, and other areas required to be left undisturbed; (3) limit construction traffic to designated construction entrances or roads; and, (4)protect any areas where marking with survey tape may not provide adequate protection. Conditions of Use To establish clearing limits, stake or wire fence may be used: • At the boundary of sensitive areas, their buffers, and other areas required to be left uncleared. • As necessary, to control vehicle access to and on the site. Design and . See Figure 4.1 for details. Installation More substantial fencing shall be used if the fence does not prevent Specifications encroachment into those areas that are not to be disturbed. Maintenance • If the fence has been damaged or visibility reduced, it shall be Standards repaired or replaced immediately and visibility restored. Survey Flagging Baling Wire Do Not Nail or Staple Wire to Trees 3' MIN. 10'-10' Metal Fence Post IMEEHEIIE111 - -III- -III III—III—III—I 11—I I I I 1—I 11-1 I I—III I I—t I 12" MIN. 1 Figure 4.1 —Stake and Wire Fence February 2005 Volume 11—Construction Stormwater Pollution Prevention 4-7 BMP C105: Stabilized Construction Entrance Purpose Construction entrances are stabilized to reduce the amount of sediment transported onto paved roads by vehicles or equipment by constructing a stabilized pad of quarry spalls at entrances to construction sites. Conditions of Use Construction entrances shall be stabilized wherever traffic will be leaving a construction site and traveling on paved roads or other paved areas within 1,000 feet of the site. On large commercial, highway, and road projects, the designer should include enough extra materials in the contract to allow for additional stabilized entrances not shown in the initial Construction SWPPP. It is difficult to determine exactly where access to these projects will take place; additional materials will enable the contractor to install them where needed. Design and • See Figure 4.2 for details. Note: the 100' minimum length of the Installation entrance shall be reduced to the maximum practicable size when the Specifications size or configuration of the site does not allow the full length(100'). • A separation geotextile shall be placed under the spalls to prevent fine sediment from pumping up into the rock pad. The geotextile shall meet the following standards: Grab Tensile Strength (ASTM D4751) 200 psi min. Grab Tensile Elongation(ASTM D4632) 30% max. Mullen Burst Strength (ASTM D3786-80a) 400 psi min. AOS(ASTM D4751) 20-45(U.S. standard sieve size) • Consider early installation of the first lift of asphalt in areas that will paved; this can be used as a stabilized entrance. Also consider the installation of excess concrete as a stabilized entrance. During large concrete pours, excess concrete is often available for this purpose. • Hog fuel (wood-based mulch) may be substituted for or combined with quarry spalls in areas that will not be used for permanent roads. Hog fuel is generally less effective at stabilizing construction entrances and should be used only at sites where the amount of traffic is very limited. Hog fuel is not recommended for entrance stabilization in urban areas. The effectiveness of hog fuel is highly variable and it generally requires more maintenance than quarry spalls. The inspector may at any time require the use of quarry spalls if the hog fuel is not preventing sediment from being tracked onto pavement or if the hog fuel is being carried onto pavement. Hog fuel is prohibited in permanent roadbeds because organics in the subgrade soils cause degradation of the subgrade support over time. • Fencing (see BMPs C103 and C104) shall be installed as necessary to restrict traffic to the construction entrance. 4-8 Volume 11—Construction Stormwater Pollution Prevention February 2005 • Whenever possible, the entrance shall be constructed on a firm, compacted subgrade. This can substantially increase the effectiveness of the pad and reduce the need for maintenance. Maintenance . Quarry spalls(or hog fuel)shall be added if the pad is no longer in Standards accordance with the specifications. • If the entrance is not preventing sediment from being tracked onto pavement,then alternative measures to keep the streets free of sediment shall be used. This may include street sweeping,an increase in the dimensions of the entrance,or the installation of a wheel wash. • Any sediment that is tracked onto pavement shall be removed by shoveling or street sweeping. The sediment collected by sweeping shall be removed or stabilized on site. The pavement shall not be cleaned by washing down the street, except when sweeping is ineffective and there is a threat to public safety. If it is necessary to wash the streets, the construction of a small sump shall be considered. The sediment would then be washed into the sump where it can be controlled. • Any quarry spalls that are loosened from the pad, which end up on the roadway shall be removed immediately. • If vehicles are entering or exiting the site at points other than the construction entrance(s), fencing(see BMPs C103 and C104) shall be installed to control traffic. • Upon project completion and site stabilization, all construction accesses intended as permanent access for maintenance shall be permanently stabilized. Driveway shall meet the requirements of the permitting agency It is recommended that the entrance be crowned so that runoff Poyp drains off the pad �,"ng / r i Install driveway culvert if there is a roadside ditch present t'-8'quarry spalls Geotextile 12'min.thickness�— 1•, Provide full width of ingress/egress area Figure 4.2—Stabilized Construction Entrance February 2005 Volume ll—Construction Stormwater Pollution Prevention 4-9 BMP C106: Wheel Wash Purpose Wheel washes reduce the amount of sediment transported onto paved roads by motor vehicles. Conditions of Use When a stabilized construction entrance(see BMP C105) is not preventing sediment from being tracked onto pavement. • Wheel washing is generally an effective BMP when installed with careful attention to topography. For example, a wheel wash can be detrimental if installed at the top of a slope abutting a right-of-way where the water from the dripping truck can run unimpeded into the street. • Pressure washing combined with an adequately sized and surfaced pad with direct drainage to a large 10-foot x 10-foot sump can be very effective. Design and Suggested details are shown in Figure 4.3. The Local Permitting Installation Authority may allow other designs. A minimum of 6 inches of asphalt Specifications treated base(ATB) over crushed base material or 8 inches over a good subgrade is recommended to pave the wheel wash. Use a low clearance truck to test the wheel wash before paving. Either a belly dump or lowboy will work well to test clearance. Keep the water level from 12 to 14 inches deep to avoid damage to truck hubs and filling the truck tongues with water. Midpoint spray nozzles are only needed in extremely muddy conditions. Wheel wash systems should be designed with a small grade change, 6 to 12 inches for a 10-foot-wide pond, to allow sediment to flow to the low side of pond to help prevent re-suspension of sediment. A drainpipe with a 2-to 3-foot riser should be installed on the low side of the pond to allow for easy cleaning and refilling. Polymers may be used to promote coagulation and flocculation in a closed-loop system. Polyacrylamide (PAM)added to the wheel wash water at a rate of 0.25 -0.5 pounds per 1,000 gallons of water increases effectiveness and reduces cleanup time. If PAM is already being used for dust or erosion control and is being applied by a water truck, the same truck can be used to change the wash water. Maintenance The wheel wash should start out the day with fresh water. Standards The wash water should be changed a minimum of once per day. On large earthwork jobs where more than 10-20 trucks per hour are expected, the wash water will need to be changed more often. Wheel wash or tire bath wastewater shall be discharged to a separate on- site treatment system, such as closed-loop recirculation or land application, or to the sanitary sewer with proper local sewer district approval. 4-10 Volume 11-Construction Stormwater Pollution Prevention February 2005 A "Schedule 40 1 '/2"schedule 40 for sprayers s II 2% 5:1 5:1 11 2% Slope Slope Slope Slope II SIApe Wheel Wash Plan 1-16-716— 20' 16� 50' Elevation View Water level �1 1:1 Slope �12----� Section A-A N.T.S. Figure 4.3 Wheel Wash Notes: 1. Asphalt construction entrance 6 in. asphalt treated base(ATB). 2. 3-inch trash pump with floats on the suction hose. 3_ Midpoint spray nozzles, if needed. 4. 6-inch sewer pipe with butterfly valves. Bottom one is a drain. Locate top pipe's invert 1 foot above bottom of wheel wash. 5. 8 foot x 8 foot sump with 5 feet of catch. Build so can be cleaned with trackhoe. 6. Asphalt curb on the low road side to direct water back to pond. 7. 6-inch sleeve under road. 8. Ball valves. 9. 15 foot. ATB apron to protect ground from splashing water. February 2005 Volume 11—Construction Stormwater Pollution Prevention 4-11 BMP C107: Construction Road/Parking Area Stabilization Purpose Stabilizing subdivision roads,parking areas,and other onsite vehicle transportation routes immediately after grading reduces erosion caused by construction traffic or runoff. Conditions of Use ' Roads or parking areas shall be stabilized wherever they are constructed, whether permanent or temporary, for use by construction traffic. • Fencing (see BMPs C103 and C104) shall be installed, if necessary, to limit the access of vehicles to only those roads and parking areas that are stabilized. Design and • On areas that will receive asphalt as part of the project, install the first Installation lift as soon as possible. Specifications • A 6-inch depth of 2-to 4-inch crushed rock, gravel base, or crushed surfacing base course shall be applied immediately after grading or utility installation. A 4-inch course of asphalt treated base(ATB) may also be used, or the road/parking area may be paved. It may also be possible to use cement or calcium chloride for soil stabilization. If cement or cement kiln dust is used for roadbase stabilization, pH monitoring and BMPs are necessary to evaluate and minimize the effects on stormwater. If the area will not be used for permanent roads, parking areas,or structures, a 6-inch depth of hog fuel may also be used,but this is likely to require more maintenance. Whenever possible, construction roads and parking areas shall be placed on a firm, compacted subgrade. • Temporary road gradients shall not exceed 15 percent. Roadways shall be carefully graded to drain. Drainage ditches shall be provided on each side of the roadway in the case of a crowned section, or on one side in the case of a super-elevated section. Drainage ditches shall be directed to a sediment control BMP. • Rather than relying on ditches,it may also be possible to grade the road so that runoff sheet-flows into a heavily vegetated area with a well- developed topsoil. Landscaped areas are not adequate. If this area has at least 50 feet of vegetation,then it is generally preferable to use the vegetation to treat runoff,rather than a sediment pond or trap. The 50 feet shall not include wetlands. If runoff is allowed to sheetflow through adjacent vegetated areas, it is vital to design the roadways and parking areas so that no concentrated runoff is created. • Storm drain inlets shall be protected to prevent sediment-laden water entering the storm drain system(see BMP C220). Maintenance • Inspect stabilized areas regularly,especially after large storm events. Standards . Crushed rock, gravel base,hog fuel, etc. shall be added as required to maintain a stable driving surface and to stabilize any areas that have eroded. • Following construction,these areas shall be restored to pre-construction condition or better to prevent future erosion. 4-12 Volume ll—Construction Stormwater Pollution Prevention February 2005 BMP C120: Temporary and Permanent Seeding Purpose Seeding is intended to reduce erosion by stabilizing exposed soils. A well-established vegetative cover is one of the most effective methods of reducing erosion. Conditions of Use ' Seeding may be used throughout the project on disturbed areas that have reached final grade or that will remain unworked for more than 30 days. • Channels that will be vegetated should be installed before major earthwork and hydroseeded with a Bonded Fiber Matrix. The vegetation should be well established(i.e., 75 percent cover) before water is allowed to flow in the ditch. With channels that will have high flows, erosion control blankets should be installed over the hydroseed. If vegetation cannot be established from seed before water is allowed in the ditch, sod should be installed in the bottom of the ditch over hydromulch and blankets. • Retention/detention ponds should be seeded as required. • Mulch is required at all times because it protects seeds from heat, moisture loss, and transport due to runoff. • All disturbed areas shall be reviewed in late August to early September and all seeding should be completed by the end of September. Otherwise, vegetation will not establish itself enough to provide more than average protection. • At final site stabilization, all disturbed areas not otherwise vegetated or stabilized shall be seeded and mulched. Final stabilization means the completion of all soil disturbing activities at the site and the establishment of a permanent vegetative cover, or equivalent permanent stabilization measures (such as pavement, riprap, gabions or geotextiles)which will prevent erosion. Design and • Seeding should be done during those seasons most conducive to Installation growth and will vary with the climate conditions of the region. Specifications Local experience should be used to determine the appropriate seeding periods. • The optimum seeding windows for western Washington are April 1 through June 30 and September 1 through October 1. Seeding that occurs between July 1 and August 30 will require irrigation until 75 percent grass cover is established. Seeding that occurs between October 1 and March 30 will require a mulch or plastic cover until 75 percent grass cover is established. • To prevent seed from being washed away, confirm that all required surface water control measures have been installed. February 2005 Volume 11—Construction Stormwater Pollution Prevention 4-13 • The seedbed should be firm and rough. All soil should be roughened no matter what the slope. If compaction is required for engineering purposes, slopes must be track walked before seeding. Backblading or smoothing of slopes greater than 4:1 is not allowed if they are to be seeded. • New and more effective restoration-based landscape practices rely on deeper incorporation than that provided by a simple single-pass rototilling treatment. Wherever practical the subgrade should be initially ripped to improve long-term permeability, infiltration, and water inflow qualities. At a minimum, permanent areas shall use soil amendments to achieve organic matter and permeability performance defined in engineered soil/landscape systems. For systems that are deeper than 8 inches the rototilling process should be done in multiple lifts, or the prepared soil system shall be prepared properly and then placed to achieve the specified depth. • Organic matter is the most appropriate form of"fertilizer"because it provides nutrients (including nitrogen, phosphorus,and potassium) in the least water-soluble form. A natural system typically releases 2-10 percent of its nutrients annually. Chemical fertilizers have since been formulated to simulate what organic matter does naturally. • In general, 10-4-6 N-P-K(nitrogen-phosphorus-potassium) fertilizer can be used at a rate of 90 pounds per acre. Slow-release fertilizers should always be used because they are more efficient and have fewer environmental impacts. It is recommended that areas being seeded for final landscaping conduct soil tests to determine the exact type and quantity of fertilizer needed. This will prevent the over-application of fertilizer. Fertilizer should not be added to the hydromulch machine and agitated more than 20 minutes before it is to be used. If agitated too much, the slow-release coating is destroyed. • There are numerous products available on the market that take the place of chemical fertilizers. These include several with seaweed extracts that are beneficial to soil microbes and organisms. If 100 percent cottonseed meal is used as the mulch in hydroseed, chemical fertilizer may not be necessary. Cottonseed meal is a good source of long-term, slow-release,available nitrogen. • Hydroseed applications shall include a minimum of 1,500 pounds per acre of mulch with 3 percent tackifier. Mulch may be made up of 100 percent: cottonseed meal; fibers made of wood,recycled cellulose, hemp, and kenaf, compost; or blends of these. Tackifier shall be plant- based, such as guar or alpha plantago, or chemical-based such as polyacrylamide or polymers. Any mulch or tackifier product used shall be installed per manufacturer's instructions. Generally, mulches come in 40-50 pound bags. Seed and fertilizer are added at time of application. 4-14 Volume 11—Construction Stormwater Pollution Prevention February 2005 • Mulch is always required for seeding. Mulch can be applied on top of the seed or simultaneously by hydroseeding. • On steep slopes, Bonded Fiber Matrix(BFM)or Mechanically Bonded Fiber Matrix (MBFM) products should be used. BFM/MBFM products are applied at a minimum rate of 3,000 pounds per acre of mulch with approximately 10 percent tackifier. Application is made so that a minimum of 95 percent soil coverage is achieved. Numerous products are available commercially and should be installed per manufacturer's instructions. Most products require 24-36 hours to cure before a rainfall and cannot be installed on wet or saturated soils. Generally,-these products come in 40-50 pound bags and include all necessary ingredients except for seed and fertilizer. BFMs and MBFMs have some advantages over blankets: • No surface preparation required; • Can be installed via helicopter in remote areas; • On slopes steeper than 2.5:1, blanket installers may need to be roped and harnessed for safety; • They are at least$1,000 per acre cheaper installed. In most cases, the shear strength of blankets is not a factor when used on slopes, only when used in channels. BFMs and MBFMs are good alternatives to blankets in most situations where vegetation establishment is the goal. • When installing seed via hydroseeding operations, only about 1/3 of the seed actually ends up in contact with the soil surface. This reduces the ability to establish a good stand of grass quickly. One way to overcome this is to increase seed quantities by up to 50 percent. • Vegetation establishment can also be enhanced by dividing the hydromulch operation into two phases: 1. Phase I- Install all seed and fertilizer with 25-30 percent mulch and tackifier onto soil in the first lift; 2. Phase 2- Install the rest of the mulch and tackifier over the first lift. An alternative is to install the mulch, seed, fertilizer, and tackifier in one lift. Then, spread or blow straw over the top of the hydromulch at a rate of about 800-1000 pounds per acre. Hold straw in place with a standard tackifier. Both of these approaches will increase cost moderately but will greatly improve and enhance vegetative establishment. The increased cost may be offset by the reduced need for: 1. Irrigation 2. Reapplication of mulch 3. Repair of failed slope surfaces February 2005 Volume 11—Construction Stormwater Pollution Prevention 4-15 This technique works with standard hydromulch(1,500 pounds per acre minimum) and BFM/MBFMs(3,000 pounds per acre minimum). • Areas to be permanently landscaped shall provide a healthy topsoil that reduces the need for fertilizers, improves overall topsoil quality, provides for better vegetal health and vitality, improves hydrologic characteristics, and reduces the need for irrigation. This can be accomplished in a number of ways: Recent research has shown that the best method to improve till soils is to amend these soils with compost. The optimum mixture is approximately two parts soil to one part compost. This equates to 4 inches of compost mixed to a depth of 12 inches in till soils. Increasing the concentration of compost beyond this level can have negative effects on vegetal health, while decreasing the concentrations can reduce the benefits of amended soils. Please note: The compost should meet specifications for Grade A quality compost in Ecology Publication 94-038. Other soils, such as gravel or cobble outwash soils, may require different approaches. Organics and fines easily migrate through the loose structure of these soils.Therefore, the importation of at least 6 inches of quality topsoil, underlain by some type of filter fabric to prevent the migration of fines,may be more appropriate for these soils. Areas that already have good topsoil, such as undisturbed areas, do not require soil amendments. • Areas that will be seeded only and not landscaped may need compost or meal-based mulch included in the hydroseed in order to establish vegetation. Native topsoil should be re-installed on the disturbed soil surface before application. • Seed that is installed as a temporary measure may be installed by hand if it will be covered by straw,mulch, or topsoil. Seed that is installed as a permanent measure may be installed by hand on small areas (usually less than 1 acre) that will be covered with mulch, topsoil, or erosion blankets. The seed mixes listed below include recommended mixes for both temporary and permanent seeding. These mixes, with the exception of the wetland mix, shall be applied at a rate of 120 pounds per acre. This rate can be reduced if soil amendments or slow- release fertilizers are used. Local suppliers or the local conservation district should be consulted for their recommendations because the appropriate mix depends on a variety of factors, including location, exposure, soil type, slope, and expected foot traffic. Alternative seed mixes approved by the local authority may be used. 4-16 Volume 11—Construction Stormwater Pollution Prevention February 2005 Table 4.1 represents the standard mix for those areas where just a temporary vegetative cover is required. Table 4.1 Temporary Erosion Control Seed Mix %Weight %Puri %Germination Chewings or annual blue grass 40 98 90 Festuca rubra var.commutata or Poa anna Perennial rye- 50 98 90 Lolium perenne _ Redtop or colonial bentgrass 5 92 85 A rostis alba or Agrostis tennis White dutch cloyer 5 98 90 Tri olium re ens Table 4.2 provides just one recommended possibility for landscaping seed. Table 4.2 Landscaping Seed Mix %Weight %Puri %Germination Perennial rye blend 70 98 90 Lolium perenne Chewings and red fescue blend 30 98 90 Festuca rubra var. commutata or Festuca rubra This turf seed mix in Table 4.3 is for dry situations where there is no need for much water. The advantage is that this mix requires very little maintenance. Table 4.3 Low-Growing Turf Seed Mix % Weight %Puri %Germination Dwarf tall fescue(several varieties) 45 98 90 Festuca arundinacea var. Dwarf perennial rye(Barclay) 30 98 90 Lolium perenne var. barclay Red fescue 20 98 90 Festuca rubra Colonial bentgrass 5 98 90 Agrostis tennis Table 4.4 presents a mix recommended for bioswales and other intermittently wet areas. Table 4.4 Bioswale Seed Mix* Wei ht %Puri %Germination Tall or meadow fescue 75-80 98 90 Festuca arundinacea or Festuca elatior Seaside/Creeping bentgrass 10-15 92 85 A rostis palustris Redtop bentgrass 5-10 90 80 A rostis alba or Agrostis ' ntea *Modified Briargreen, Inc. Hydroseeding Guide Wetlands Seed Mix February 2005 Volume 11—Construction Stormwater Pollution Prevention 4-17 The seed mix shown in Table 4.5 is a recommended low-growing, relatively non-invasive seed mix appropriate for very wet areas that are not regulated wetlands. Other mixes may be appropriate, depending on the soil type and hydrology of the area. Recent research suggests that bentgrass(agrostis sp.) should be emphasized in wet-area seed mixes. Apply this mixture at a rate of 60 pounds per acre. Table 4.5 Wet Area Seed Mix* %Weight %Puri %Germination Tall or meadow fescue 60-70 98 90 Festuca arundinacea or Festuca elatior Seaside/Creeping bentgrass 10-15 98 85 AZrostis palustris Meadow foxtail 10-15 90 80 Ale ocurus pratensis Alsike clover 1-6 98 90 Tri olium h bridum Redtop bentgrass 1-6 92 85 Agrostis alba *Modified Briargreen,Inc. Hydroseeding Guide Wetlands Seed Mix The meadow seed mix in Table 4.6 is recommended for areas that will be maintained infrequently or not at all and where colonization by native plants is desirable. Likely applications include rural road and utility right- of-way. Seeding should take place in September or very early October in order to obtain adequate establishment prior to the winter months. The appropriateness of clover in the mix may need to be considered, as this can be a fairly invasive species. If the soil is amended, the addition of clover may not be necessary. Table 4.6 Meadow Seed Mix %Weight %Puri %Germination Redtop or Oregon bentgrass 20 92 85 Agrostis alba or Agrostis ore onensis Red fescue 70 98 90 Festuca rubra White dutch clover 10 98 90 Tri olium re ens Maintenance . Any seeded areas that fail to establish at least 80 percent cover(100 Standards percent cover for areas that receive sheet or concentrated flows) shall be reseeded. If reseeding is ineffective, an alternate method, such as sodding,mulching, or nets/blankets, shall be used. If winter weather prevents adequate grass growth, this time limit may be relaxed at the discretion of the local authority when sensitive areas would otherwise be protected. 4-18 Volume 11—Construction Stormwater Pollution Prevention February 2005 • After adequate cover is achieved, any areas that experience erosion shall be reseeded and protected by mulch. If the erosion problem is drainage related, the problem shall be fixed and the eroded area reseeded and protected by mulch. • Seeded areas shall be supplied with adequate moisture, but not watered to the extent that it causes runoff. February 2005 Volume 11-Construction Stormwater Pollution Prevention 4-19 BMP C121: Mulching Purpose The purpose of mulching soils is to provide immediate temporary protection from erosion. Mulch also enhances plant establishment by conserving moisture, holding fertilizer, seed, and topsoil in place,and moderating soil temperatures. There is an enormous variety of mulches that can be used. Only the most common types are discussed in this section. Conditions of Use As a temporary cover measure, mulch should be used: • On disturbed areas that require cover measures for less than 30 days. • As a cover for seed during the wet season and during the hot summer months. • During the wet season on slopes steeper than 3H:1V with more than 10 feet of vertical relief • Mulch may be applied at any time of the year and must be refreshed periodically. Design and For mulch materials,application rates, and specifications, see Table 4.7. Installation Note: Thicknesses may be increased for disturbed areas in or near Specifications sensitive areas or other areas highly susceptible to erosion. Mulch used within the ordinary high-water mark of surface waters should be selected to minimize potential flotation of organic matter. Composted organic materials have higher specific gravities(densities) than straw, wood, or chipped material. Maintenance • The thickness of the cover must be maintained. Standards • Any areas that experience erosion shall be remulched and/or protected with a net or blanket. If the erosion problem is drainage related, then the problem shall be fixed and the eroded area remulched. 4-20 Volume 11-Construction Stormwater Pollution Prevention February 2005 Table 4.7 Mulch Standards and Guidelines Mulch Application Material Quality Standards Rates Remarks Straw Air-dried;free from 2"-3"thick;5 Cost-effective protection when applied with adequate undesirable seed and bales per 1000 sf thickness. Hand-application generally requires greater coarse material. or 2-3 tons per thickness than blown straw.The thickness of straw may be acre reduced by half when used in conjunction with seeding. In windy areas straw must be held in place by crimping,using a tackifier,or covering with netting. Blown straw always has to be held in place with a tackifier as even light winds will blow it away.Straw,however,has several deficiencies that should be considered when selecting mulch materials.It often introduces and/or encourages the propagation of weed species and it has no significant long-term benefits. Straw should be used only if mulches with long-term benefits are unavailable locally. It should also not be used within the ordinary high-water elevation of surface waters(due to flotation). Hydromulch No growth Approx.25-30 Shall be applied with hydromulcher. Shall not be used inhibiting factors. lbs per 1000 sf without seed and tackifier unless the application rate is at or 1500 -2000 least doubled. Fibers longer than about Y4-1 inch clog lbs per acre hydromulch equipment. Fibers should be kept to less than 1% inch. Composted No visible water or 2"thick min.; More effective control can be obtained by increasing Mulch and dust during approx. 100 tons thickness to 3". Excellent mulch for protecting final grades Compost handling. Must be per acre(approx. until landscaping because it can be directly seeded or tilled purchased from 800 lbs per yard) into soil as an amendment. Composted mulch has a coarser supplier with Solid size gradation than compost.It is more stable and practical Waste Handling to use in wet areas and during rainy weather conditions. Permit(unless exempt). Chipped Site Average size shall 2"minimum This is a cost-effective way to dispose of debris from Vegetation be several inches. thickness clearing and grubbing,and it eliminates the problems Gradations from associated with burning. Generally,it should not be used on fines to 6 inches in slopes above approx. 100/.because of its tendency to be length for texture, transported by runoff. It is not recommended within 200 variation,and feet of surface waters. If seeding is expected shortly after interlocking mulch,the decomposition of the chipped vegetation may tie properties. up nutrients important to grass establishment. Wood-based _ No visible water or 2"thick;approx. This material is often called"hog or hogged fuel." It is Mulch dust during 100 tons per acre usable as a material for Stabilized Construction Entrances handling. Must be (approx.800 lbs. (BMP C 105)and as a mulch. The use of mulch ultimately purchased from a per cubic yard) improves the organic matter in the soil. Special caution is supplier with a Solid advised regarding the source and composition of wood- Waste Handling based mulches. Its preparation typically does not provide Permit or one any weed seed control,so evidence of residual vegetation in exempt from solid its composition or known inclusion of weed plants or seeds waste regulations. should be monitored and prevented(or minimized). February 2005 Volume 11—Construction Stormwater Pollution Prevention 4-21 BMP C122: Nets and Blankets Purpose Erosion control nets and blankets are intended to prevent erosion and hold seed and mulch in place on steep slopes and in channels so that vegetation can become well established. In addition, some nets and blankets can be used to permanently reinforce turf to protect drainage ways during high flows. Nets(commonly called matting)are strands of material woven into an open,but high-tensile strength net(for example, coconut fiber matting). Blankets are strands of material that are not tightly woven,but instead form a layer of interlocking fibers, typically held together by a biodegradable or photodegradable netting(for example, excelsior or straw blankets). They generally have lower tensile strength than nets,but cover the ground more completely. Coir(coconut fiber) fabric comes as both nets and blankets. Conditions of Use Erosion control nets and blankets should be used: • To aid permanent vegetated stabilization of slopes 2H:1 V or greater and with more than 10 feet of vertical relief. • For drainage ditches and swales (highly recommended). The application of appropriate netting or blanket to drainage ditches and swales can protect bare soil from channelized runoff while vegetation is established. Nets and blankets also can capture a great deal of sediment due to their open, porous structure. Synthetic nets and blankets can be used to permanently stabilize channels and may provide a cost-effective, environmentally preferable alternative to nprap. 100 percent synthetic blankets manufactured for use in ditches may be easily reused as temporary ditch liners. Disadvantages of blankets include: • Surface preparation required; • On slopes steeper than 2.5:1, blanket installers may need to be roped and harnessed for safety; • They cost at least$4,000-6,000 per acre installed. Advantages of blankets include: • Can be installed without mobilizing special equipment; • Can be installed by anyone with minimal training; • Can be installed in stages or phases as the project progresses; • Seed and fertilizer can be hand-placed by the installers as they progress down the slope; • Can be installed in any weather; • There are numerous types of blankets that can be designed with various parameters in mind. Those parameters include: fiber blend, mesh strength, longevity, biodegradability,cost, and availability. 4-22 Volume 11—Construction Stormwater Pollution Prevention February 2005 Design and . See Figure 4.4 and Figure 4.5 for typical orientation and installation of Installation blankets used in channels and as slope protection. Note: these are Specifications typical only; all blankets must be installed per manufacturer's installation instructions. • Installation is critical to the effectiveness of these products. If good ground contact is not achieved,runoff can concentrate under the product,resulting in significant erosion. • Installation of Blankets on Slopes: 1. Complete final grade and track walk up and down the slope. 2. Install hydromulch with seed and fertilizer. 3. Dig a small trench,approximately 12 inches wide by 6 inches deep along the top of the slope. 4. Install the leading edge of the blanket into the small trench and staple approximately every 18 inches. NOTE: Staples are metal,"U"-shaped,and a minimum of 6 inches long. Longer staples are used in sandy soils. Biodegradable stakes are also available. 5. Roll the blanket slowly down the slope as installer walks backwards. NOTE: The blanket rests against the installer's legs. Staples are installed as the blanket is unrolled. It is critical that the proper staple pattern is used for the blanket being installed. The blanket is not to be allowed to roll down the slope on its own as this stretches the blanket making it impossible to maintain soil contact. In addition, no one is allowed to walk on the blanket after it is in place. 6. If the blanket is not long enough to cover the entire slope length, the trailing edge of the upper blanket should overlap the leading edge of the lower blanket and be stapled. On steeper slopes, this overlap should be installed in a small trench, stapled, and covered with soil. • With the variety of products available, it is impossible to cover all the details of appropriate use and installation. Therefore, it is critical that the design engineer consults the manufacturer's information and that a site visit takes place in order to insure that the product specified is appropriate. Information is also available at the following web sites: 1. WSDOT: hqp://www.wsdot.wa.gov/eesc/environmental/ 2. Texas Transportation Institute: hW://www.dot.state.tx.us/insdtdot/orgchart/cmd/erosion/contents htm February 2005 Volume 11—Construction Stormwater Pollution Prevention 4-23 • Jute matting must be used in conjunction with mulch(BMP C121). Excelsior, woven straw blankets and coir(coconut fiber) blankets may be installed without mulch. There are many other types of erosion control nets and blankets on the market that may be appropriate in certain circumstances. • In general, most nets(e.g.,jute matting) require mulch in order to prevent erosion because they have a fairly open structure. Blankets typically do not require mulch because they usually provide complete protection of the surface. • Extremely steep, unstable, wet, or rocky slopes are often appropriate candidates for use of synthetic blankets,as are riverbanks, beaches and other high-energy environments. If synthetic blankets are used, the soil should be hydromulched first. • 100 percent biodegradable blankets are available for use in sensitive areas. These organic blankets are usually held together with a paper or fiber mesh and stitching which may last up to a year. • Most netting used with blankets is photodegradable, meaning they break down under sunlight(not UV stabilized). However, this process can take months or years even under bright sun. Once vegetation is established,sunlight does not reach the mesh. It is not uncommon to find non-degraded netting still in place several years after installation. This can be a problem if maintenance requires the use of mowers or ditch cleaning equipment. In addition, birds and small animals can become trapped in the netting. Maintenance • Good contact with the ground must be maintained, and erosion must Standards not occur beneath the net or blanket. • Any areas of the net or blanket that are damaged or not in close contact with the ground shall be repaired and stapled. If erosion occurs due to poorly controlled drainage, the problem shall be fixed and the eroded area protected. 4-24 Volume 11—Construction Stormwater Pollution Prevention February 2005 \(a w2mm� /\\/\\/� ie�l \/\\/ /\ •el•itsonan) �/ Longitudinal Anchor Trench Terminal Slope and Channel Anchor Trench Y Y Y Y Y Ga if Y Y + Stake at X-5' P (1-1.5m)intervals. P P P Check slot at 25'(7.6m)intervals Isometric View � Y� j P s•lisanmt i \/ Initial Channel Anchor Trench Intermittent Check Slot NOTES: 1.Check sloe to be constructed per manufacturers specifications. 2.Staking or stapling layout per manufacturers specifications. Figure 4.4—Channel Installation Slope surface shall be smooth before placement for proper soil contact. If there is a berm at the Stapling pattem as per top of slope,anchor manufacturer's recommendations. upslope of the berm. Min.2" i II Overlap j r Anchor in 6"x6"min.Trench and staple at 17' intervals. Min.6"overlap. Staple overlaps max.5"spacing. Bring material down to a level area,turn Do not stretch blankets/mattings tight- the end under 4"and staple at 1 Zintervals. allow the rolls to mold to any irregularities. For sbpes less than 3K 1 V,rolls Lime,fertilize,and seed before installation. may be placed in horizontal strips. Planting of shrubs,trees,etc-Should occur after installation. Figure 4.5—Slope Installation February 2005 Volume !l—Construction Stormwater Pollution Prevention 4-25 BMP C123: Plastic Covering Purpose Plastic covering provides immediate, short-term erosion protection to slopes and disturbed areas. Conditions of • Plastic covering may be used on disturbed areas that require cover Use measures for less than 30 days, except as stated below. • Plastic is particularly useful for protecting cut and fill slopes and stockpiles. Note: The relatively rapid breakdown of most polyethylene sheeting makes it unsuitable for long-term(greater than six months) applications. • Clear plastic sheeting can be used over newly-seeded areas to create a greenhouse effect and encourage grass growth if the hydroseed was installed too late in the season to establish 75 percent grass cover, or if the wet season started earlier than normal. Clear plastic should not be used for this purpose during the summer months because the resulting high temperatures can kill the grass. • Due to rapid runoff caused by plastic sheeting, this method shall not be used upslope of areas that might be adversely impacted by concentrated runoff. Such areas include steep and/or unstable slopes. • While plastic is inexpensive to purchase, the added cost of installation, maintenance,removal, and disposal make this an expensive material, up to $1.50-2.00 per square yard. • Whenever plastic is used to protect slopes, water collection measures must be installed at the base of the slope. These measures include plastic-covered berms,channels, and pipes used to covey clean rainwater away from bare soil and disturbed areas. At no time is clean runoff from a plastic covered slope to be mixed with dirty runoff from a project. • Other uses for plastic include: 1. Temporary ditch liner; 2. Pond liner in temporary sediment pond; 3. Liner for bermed temporary fuel storage area if plastic is not reactive to the type of fuel being stored; 4. Emergency slope protection during heavy rains;and, 5. Temporary drainpipe("elephant trunk") used to direct water. 4-26 Volume 11—Construction Stormwater Pollution Prevention February 2005 Design and Plastic slope cover must be installed as follows: Installation 1. Run plastic up and down slope,not across slope; Specifications 2. Plastic may be installed perpendicular to a slope if the slope length is less than 10 feet; 3. Minimum of 8-inch overlap at seams; 4. On long or wide slopes, or slopes subject to wind, all seams should be taped; 5. Place plastic into a small (12-inch wide by 6-inch deep) slot trench at the top of the slope and backfill with soil to keep water from flowing underneath; 6. Place sand filled burlap or geotextile bags every 3 to 6 feet along seams and pound a wooden stake through each to hold them in place; 7. Inspect plastic for rips, tears, and open seams regularly and repair immediately. This prevents high velocity runoff from contacting bare soil which causes extreme erosion; 8. Sandbags may be lowered into place tied to ropes. However, all sandbags must be staked in place. • Plastic sheeting shall have a minimum thickness of 0.06 millimeters. • If erosion at the toe of a slope is likely, a gravel berm, riprap, or other suitable protection shall be installed at the toe of the slope in order to reduce the velocity of runoff. Maintenance . Torn sheets must be replaced and open seams repaired. Standards • If the plastic begins to deteriorate due to ultraviolet radiation, it must be completely removed and replaced. • When the plastic is no longer needed, it shall be completely removed. • Dispose of old tires appropriately. February 2005 Volume 11—Construction Stormwater Pollution Prevention 4-27 BMP C124: Sodding Purpose The purpose of sodding is to establish permanent turf for immediate erosion protection and to stabilize drainage ways where concentrated overland flow will occur. Conditions of Use Sodding may be used in the following areas: • Disturbed areas that require short-term or long-term cover. • Disturbed areas that require immediate vegetative cover. • All waterways that require vegetative lining. Waterways may also be seeded rather than sodded, and protected with a net or blanket. Design and Sod shall be free of weeds, of uniform thickness (approximately 1-inch Installation thick),and shall have a dense root mat for mechanical strength. Specifications The following steps are recommended for sod installation: • Shape and smooth the surface to final grade in accordance with the approved grading plan. The swale needs to be overexcavated 4 to 6 inches below design elevation to allow room for placing soil amendment and sod. • Amend 4 inches(minimum) of compost into the top 8 inches of the soil if the organic content of the soil is less than ten percent or the permeability is less than 0.6 inches per hour. Compost used should meet Ecology publication 94-038 specifications for Grade A quality compost. • Fertilize according to the supplier's recommendations. • Work lime and fertilizer 1 to 2 inches into the soil,and smooth the surface. • Lay strips of sod beginning at the lowest area to be sodded and perpendicular to the direction of water flow. Wedge strips securely into place. Square the ends of each strip to provide for a close, tight fit. Stagger joints at least 12 inches. Staple on slopes steeper than 3H:I V. Staple the upstream edge of each sod strip. • Roll the sodded area and irrigate. • When sodding is carried out in alternating strips or other patterns, seed the areas between the sod immediately after sodding. Maintenance If the grass is unhealthy, the cause shall be determined and appropriate Standards action taken to reestablish a healthy groundcover. If it is impossible to establish a healthy groundcover due to frequent saturation, instability, or some other cause, the sod shall be removed, the area seeded with an appropriate mix, and protected with a net or blanket. 4-28 Volume 11—Construction Stormwater Pollution Prevention February 2005 BMP C125: Topsoiling Purpose To provide a suitable growth medium for final site stabilization with vegetation. While not a permanent cover practice in itself, topsoiling is an integral component of providing permanent cover in those areas where there is an unsuitable soil surface for plant growth. Native soils and disturbed soils that have been organically amended not only retain much more sormwater, but they also serve as effective biofilters for urban pollutants and, by supporting more vigorous plant growth, reduce the water, fertilizer and pesticides needed to support installed landscapes. Topsoil does not include any subsoils but only the material from the top several inches including organic debris. Conditions of Native soils should be left undisturbed to the maximum extent Use practicable. Native soils disturbed during clearing and grading should be restored,to the maximum extent practicable, to a condition where moisture-holding capacity is equal to or better than the original site conditions. This criterion can be met by using on-site native topsoil, incorporating amendments into on-site soil, or importing blended topsoil. • Topsoiling is a required procedure when establishing vegetation on shallow soils, and soils of critically low pH(high acid) levels. • Stripping of existing,properly functioning soil system and vegetation for the purpose of topsoiling during construction is not acceptable. If an existing soil system is functioning properly it shall be preserved in its undisturbed and uncompacted condition. • Depending on where the topsoil comes from, or what vegetation was on site before disturbance, invasive plant seeds may be included and could cause problems for establishing native plants, landscaped areas, or grasses. • Topsoil from the site will contain mycorrhizal bacteria that are necessary for healthy root growth and nutrient transfer. These native mycorrhiza are acclimated to the site and will provide optimum conditions for establishing grasses. Commercially available mycorrhiza products should be used when topsoil is brought in from off-site. Design and If topsoiling is to be done, the following items should be considered: Installation Maximize the depth of the topsoil wherever possible to provide the Specifications maximum possible infiltration capacity and beneficial growth medium. Topsoil depth shall be at least 8 inches with a minimum organic content of 10 percent dry weight and pH between 6.0 and 8.0 or matching the pH of the undisturbed soil. This can be accomplished either by returning native topsoil to the site and/or incorporating organic amendments. Organic amendments should be incorporated to a minimum 8-inch depth except where tree roots or other natural February 2005 Volume 11—Construction Stormwater Pollution Prevention 4-29 features limit the depth of incorporation. Subsoils below the 12-inch depth should be scarified at least 2 inches to avoid stratified layers, where feasible. The decision to either layer topsoil over a subgrade or incorporate topsoil into the underlying layer may vary depending on the planting specified. • If blended topsoil is imported, then fines should be limited to 25 percent passing through a 200 sieve. • The final composition and construction of the soil system will result in a natural selection or favoring of certain plant species over time. For example, recent practices have shown that incorporation of topsoil may favor grasses,while layering with mildly acidic, high-carbon amendments may favor more woody vegetation. • Locate the topsoil stockpile so that it meets specifications and does not interfere with work on the site. It may be possible to locate more than one pile in proximity to areas where topsoil will be used. • Allow sufficient time in scheduling for topsoil to be spread prior to seeding, sodding,or planting. • Care must be taken not to apply to subsoil if the two soils have contrasting textures. Sandy topsoil over clayey subsoil is a particularly poor combination, as water creeps along the junction between the soil layers and causes the topsoil to slough. • If topsoil and subsoil are not properly bonded, water will not infiltrate the soil profile evenly and it will be difficult to establish vegetation. The best method to prevent a lack of bonding is to actually work the topsoil into the layer below for a depth of at least 6 inches. • Ripping or re-structuring the subgrade may also provide additional benefits regarding the overall infiltration and interflow dynamics of the soil system. • Field exploration of the site shall be made to determine if there is surface soil of sufficient quantity and quality to justify stripping. Topsoil shall be friable and loamy(loam, sandy loam, silt loam, sandy clay loam, clay loam). Areas of natural ground water recharge should be avoided. • Stripping shall be confined to the immediate construction area. A 4- to 6- inch stripping depth is common, but depth may vary depending on the particular soil. All surface runoff control structures shall be in place prior to stripping. Stockpiling of topsoil shall occur in the following manner: • Side slopes of the stockpile shall not exceed 2:1. • An interceptor dike with gravel outlet and silt fence shall surround all topsoil stockpiles between October 1 and April 30. Between May 1 4-30 Volume 11—Construction Stormwater Pollution Prevention February 2005 and September 30, an interceptor dike with gravel outlet and silt fence shall be installed if the stockpile will remain in place for a longer period of time than active construction grading. • Erosion control seeding or covering with clear plastic or other mulching materials of stockpiles shall be completed within 2 days (October 1 through Apri130)or 7 days(May 1 through September 30) of the formation of the stockpile. Native topsoil stockpiles shall not be covered with plastic. • Topsoil shall not be placed while in a frozen or muddy condition, when the subgrade is excessively wet, or when conditions exist that may otherwise be detrimental to proper grading or proposed sodding or seeding. • Previously established grades on the areas to be topsoiled shall be maintained according to the approved plan. • When native topsoil is to be stockpiled and reused the following should apply to ensure that the mycorrhizal bacterial, earthworms, and other beneficial organisms will not be destroyed: 1. Topsoil is to be re-installed within 4 to 6 weeks; 2. Topsoil is not to become saturated with water, 3. Plastic cover is not allowed. Maintenance • Inspect stockpiles regularly, especially after large storm events. Standards Stabilize any areas that have eroded. February 2005 Volume 11-Construction Stormwater Pollution Prevention 4-31 BMP C126: Polyacrylamide for Soil Erosion Protection Purpose Polyacrylamide(PAM) is used on construction sites to prevent soil erosion. Applying PAM to bare soil in advance of a rain event significantly reduces erosion and controls sediment in two ways. First, PAM increases the soil's available pore volume, thus increasing infiltration through flocculation and reducing the quantity of stormwater runoff. Second, it increases flocculation of suspended particles and aids in their deposition, thus reducing stormwater runoff turbidity and improving water quality. Conditions of Use PAM shall not-be directly applied to water or allowed to enter a water body. In areas that drain to a sediment pond, PAM can be applied to bare soil under the following conditions: • During rough grading operations. • Staging areas. • Balanced cut and fill earthwork. • Haul roads prior to placement of crushed rock surfacing. • Compacted soil roadbase. • Stockpiles. • After final grade and before paving or final seeding and planting. • Pit sites. • Sites having a winter shut down. In the case of winter shut down, or where soil will remain unworked for several months, PAM should be used together with mulch. Design and PAM may be applied in dissolved form with water, or it may be applied in Installation dry, granular or powdered form. The preferred application method is the Specifications dissolved form. PAM is to be applied at a maximum rate of 2/3 pound PAM per 1000 gallons water(80 mg/L) per I acre of bare soil. Table 4.8 can be used to determine the PAM and water application rate for a disturbed soil area. Higher concentrations of PAM do not provide any additional effectiveness. Table 4.8 PAM and Water Application Rates Disturbed Area ac PAM Ibs Water al 0.50 0.33 500 1.00 0.66 1,000 1.50 1.00 1,500 2.00 1.32 2,000 2.50 1.65 2,500 3.00 2.00 3,000 3.50 2.33 3,500 4.00 2.65 4,000 4.50 3.00 4,500 5.00 3.33 5,000 4-32 Volume II—Construction Stormwater Pollution Prevention February 2005 The Preferred Method: • Pre-measure the area where PAM is to be applied and calculate the amount of product and water necessary to provide coverage at the specified application rate(2/3 pound PAM/1000 gallons/acre). • PAM has infinite solubility in water,but dissolves very slowly. Dissolve pre-measured dry granular PAM with a known quantity of clean water in a bucket several hours or overnight. Mechanical mixing will help dissolve the PAM. Always add PAM to water-not water to PAM. • Pre-fill the-water truck about 1/8 full with water. The water does not have to be potable,but it must have relatively low turbidity—in the range of 20 NTU or less. • Add PAM/Water mixture to the truck • Completely fill the water truck to specified volume. • Spray PAM/Water mixture onto dry soil until the soil surface is uniformly and completely wetted. An Alternate Method: PAM may also be applied as a powder at the rate of 5 lbs. per acre. This must be applied on a day that is dry. For areas less than 5-10 acres,a hand-held"organ grinder" fertilizer spreader set to the smallest setting will work. Tractor-mounted spreaders will work for larger areas. The following shall be used for application of PAM: • PAM shall be used in conjunction with other BMPs and not in place of other BMPs. • Do not use PAM on a slope that flows directly into a stream or wetland. The stormwater runoff shall pass through a sediment control BMP prior to discharging to surface waters. • Do not add PAM to water discharging from site. • When the total drainage area is greater than or equal to 5 acres, PAM treated areas shall drain to a sediment pond. • Areas less than 5 acres shall drain to sediment control BMPs, such as a minimum of 3 check dams per acre. The total number of check dams used shall be maximized to achieve the greatest amount of settlement of sediment prior to discharging from the site. Each check dam shall be spaced evenly in the drainage channel through which stormwater flows are discharged off-site. • On all sites, the use of silt fence shall be maximized to limit the discharges of sediment from the site. • All areas not being actively worked shall be covered and protected from rainfall. PAM shall not be the only cover BMP used. February 2005 Volume /l—Construction Stormwater Pollution Prevention 4-33 • PAM can be applied to wet soil, but dry soil is preferred due to less sediment loss. • PAM will work when applied to saturated soil but is not as effective as applications to dry or damp soil. • Keep the granular PAM supply out of the sun. Granular PAM loses its effectiveness in three months after exposure to sunlight and air. • Proper application and re-application plans are necessary to ensure total effectiveness of PAM usage. • PAM, combined with water, is very slippery and can be a safety hazard. Care must be taken to prevent spills of PAM powder onto paved surfaces. During an application of PAM, prevent over-spray from reaching pavement as pavement will become slippery. If PAM powder gets on skin or clothing,wipe it off with a rough towel rather than washing with water-this only makes cleanup messier and take longer. • Some PAMs are more toxic and carcinogenic than others. Only the most environmentally safe PAM products should be used. The specific PAM copolymer formulation must be anionic. Cationic PAM shall not be used in any application because of known aquatic toxicity problems. Only the highest drinking water grade PAM, certified for compliance with ANSI/NSF Standard 60 for drinking water treatment, will be used for soil applications. Recent media attention and high interest in PAM has resulted in some entrepreneurial exploitation of the term "polymer." All PAM are polymers, but not all polymers are PAM, and not all PAM products comply with ANSI/NSF Standard 60. PAM use shall be reviewed and approved by the local permitting authority. The Washington State Department of Transportation(WSDOT) has listed approved PAM products on their web page. • PAM designated for these uses should be "water soluble" or"linear" or "non-crosslinked". Cross-linked or water absorbent PAM, polymerized in highly acidic (pH<2) conditions, are used to maintain soil moisture content. • The PAM anionic charge density may vary from 2-30 percent; a value of 18 percent is typical. Studies conducted by the United States Department of Agriculture (USDA)/ARS demonstrated that soil stabilization was optimized by using very high molecular weight(12- 15 mg/mole), highly anionic (>20%hydrolysis) PAM. • PAM tackifiers are available and being used in place of guar and alpha plantago. Typically, PAM tackifiers should be used at a rate of no more than 0.5-1 lb. per 1000 gallons of water in a hydromulch machine. Some tackifier product instructions say to use at a rate of 3 — 4-34 Volume 11—Construction Stormwater Pollution Prevention February 2005 5 lbs. per acre, which can be too much. In addition,pump problems can occur at higher rates due to increased viscosity. Maintenance . PAM may be reapplied on actively worked areas after a 48-hour Standards period. • Reapplication is not required unless PAM treated soil is disturbed or unless turbidity levels show the need for an additional application. If PAM treated soil is left undisturbed a reapplication may be necessary after two months. More PAM applications may be required for steep slopes, silty and clayey soils(USDA Classification Type "C" and "D" soils), long grades, and high precipitation areas. When PAM is applied first to bare soil and then covered with straw, a reapplication may not be necessary for several months. • Loss of sediment and PAM may be a basis for penalties per RCW 90.48.080. February 2005 Volume 11—Construction Stormwater Pollution Prevention 4-35 BMP C130: Surface Roughening Purpose Surface roughening aids in the establishment of vegetative cover, reduces runoff velocity, increases infiltration,and provides for sediment trapping through the provision of a rough soil surface. Horizontal depressions are created by operating a tiller or other suitable equipment on the contour or by leaving slopes in a roughened condition by not fine grading them. Conditions for • All slopes steeper than 3:1 and greater than 5 vertical feet require Use surface roughening. • Areas with grades steeper than 3:1 should be roughened to a depth of 2 to 4 inches.prior to seeding. • Areas that will not be stabilized immediately may be roughened to reduce runoff velocity until seeding takes place. • Slopes with a stable rock face do not require roughening. • Slopes where mowing is planned should not be excessively roughened. Design and There are different methods for achieving a roughened soil surface on a Installation slope, and the selection of an appropriate method depends upon the type of Specifications slope. Roughening methods include stair-step grading, grooving,contour furrows, and tracking. See Figure 4.6 for tracking and contour furrows. Factors to be considered in choosing a method are slope steepness, mowing requirements, and whether the slope is formed by cutting or filling. • Disturbed areas that will not require mowing may be stair-step graded, grooved,or left rough after filling. • Stair-step grading is particularly appropriate in soils containing large amounts of soft rock. Each"step" catches material that sloughs from above, and provides a level site where vegetation can become established. Stairs should be wide enough to work with standard earth moving equipment. Stair steps must be on contour or gullies will form on the slope. • Areas that will be mowed(these areas should have slopes less steep than 3:1)may have small furrows left by disking,harrowing,raking, or seed-planting machinery operated on the contour. • Graded areas with slopes greater than 3:1 but less than 2:1 should be roughened before seeding. This can be accomplished in a variety of ways, including "track walking," or driving a crawler tractor up and down the slope, leaving a pattern of cleat imprints parallel to slope contours. • Tracking is done by operating equipment up and down the slope to leave horizontal depressions in the soil. Maintenance • Areas that are graded in this manner should be seeded as quickly as Standards possible. • Regular inspections should be made of the area. If rills appear, they should be re-graded and re-seeded immediately. 4-36 Volume ll—Construction Stormwater Pollution Prevention February 2005 Tracking 'TRACKING'with machinery up and down _> _ — the slope provides grooves that will catch seed, rainfall and reduce runoff. Contour Furrows \VA 50 6"min (15m� (150mm) VA VA Maximum \\�\\X/ Grooves Will Catch Seed, \\�jj\�j/\ Fertilizer, Decrease all Runoff. and Figure 4.6—Surface Roughening by Tracking and Contour Furrows February 2005 Volume 11— Construction Stormwater Pollution Prevention 4-37 BMP C131: Gradient Terraces Purpose Gradient terraces reduce erosion damage by intercepting surface runoff and conducting it to a stable outlet at a non-erosive velocity. Conditions of Use Gradient terraces normally are limited to denuded land having a water erosion problem. They should not be constructed on deep sands or on soils that are too stony, steep, or shallow to permit practical and economical installation and maintenance. Gradient terraces may be used only where suitable outlets are or will be made available. See Figure 4.7 for gradient terraces. Design and The maximum spacing of gradient terraces should be determined by Installation the following method: Specifications VI = (0.8)s+y Where: VI = vertical interval in feet s = land rise per 100 feet, expressed in feet y =a soil and cover variable with values from 1.0 to 4.0 Values of"y"are influenced by soil erodibility and cover practices. The lower values are applicable to erosive soils where little to no residue is left on the surface. The higher value is applicable only to erosion-resistant soils where a large amount of residue (1'/z tons of straw/acre equivalent) is on the surface. • The minimum constructed cross-section should meet the design dimensions. • The top of the constructed ridge should not be lower at any point than the design elevation plus the specified overfill for settlement. The opening at the outlet end of the terrace should have a cross section equal to that specified for the terrace channel. • Channel grades may be either uniform or variable with a maximum grade of 0.6 feet per 100 feet length. For short distances, terrace grades may be increased to improve alignment. The channel velocity should not exceed that which is nonerosive for the soil type with the planned treatment. • All gradient terraces should have adequate outlets. Such an outlet may be a grassed waterway, vegetated area, or tile outlet. In all cases the outlet must convey runoff from the terrace or terrace system to a point where the outflow will not cause damage. Vegetative cover should be used in the outlet channel. • The design elevation of the water surface of the terrace should not be lower than the design elevation of the water surface in the outlet at their junction, when both are operating at design flow. 4-38 Volume 11—Construction Stormwater Pollution Prevention February 2005 • Vertical spacing determined by the above methods may be increased as much as 0.5 feet or 10 percent, whichever is greater, to provide better alignment or location,to avoid obstacles, to adjust for equipment size,or to reach a satisfactory outlet. • The drainage area above the top should not exceed the area that would be drained by a terrace with normal spacing. • The terrace should have enough capacity to handle the peak runoff expected from a 2-year, 24-hour design storm without overtopping. • The terrace cross-section should be proportioned to fit the land slope. The ridge height should include a reasonable settlement factor. The ridge should have a minimum top width of 3 feet at the design height. The minimum cross-sectional area of the terrace channel should be 8 square feet for land slopes of 5 percent or less, 7 square feet for slopes from 5 to 8 percent, and 6 square feet for slopes steeper than 8 percent. The terrace can be constructed wide enough to be maintained using a small cat. Maintenance • Maintenance should be performed as needed. Terraces should be Standards inspected regularly; at least once a year, and after large storm events. Slope to adequate outlet. 10' min. Figure 4.7-Gradient Terraces February 2005 Volume 11—Construction Stormwater Pollution Prevention 4-39 BMP C140: Dust Control Purpose Dust control prevents wind transport of dust from disturbed soil surfaces onto roadways, drainage ways, and surface waters. Conditions of Use • In areas(including roadways) subject to surface and air movement of dust where on-site and off-site impacts to roadways, drainage ways, or surface waters are likely. Design and • Vegetate or mulch areas that will not receive vehicle traffic. In areas Installation where planting, mulching, or paving is impractical, apply gravel or Specifications landscaping rock. • Limit dust generation by clearing only those areas where immediate activity will take place, leaving the remaining area(s) in the original condition, if stable. Maintain the original ground cover as long as practical. • Construct natural or artificial windbreaks or windscreens. These may be designed as enclosures for small dust sources. • Sprinkle the site with water until surface is wet. Repeat as needed. To prevent carryout of mud onto street,refer to Stabilized Construction Entrance(BMP C 105). • Irrigation water can be used for dust control. Irrigation systems should be installed as a first step on sites where dust control is a concern. • Spray exposed soil areas with a dust palliative, following the manufacturer's instructions and cautions regarding handling and application. Used oil is prohibited from use as a dust suppressant. Local governments may approve other dust palliatives such as calcium chloride or PAM. • PAM(BMP C126) added to water at a rate of 0.5 lbs. per 1,000 gallons of water per acre and applied from a water truck is more effective than water alone. This is due to the increased infiltration of water into the soil and reduced evaporation. In addition, small soil particles are bonded together and are not as easily transported by wind. Adding PAM may actually reduce the quantity of water needed for dust control, especially in eastern Washington. Since the wholesale cost of PAM is about$4.00 per pound, this is an extremely cost- effective dust control method. Techniques that can be used for unpaved roads and lots include: • Lower speed limits. High vehicle speed increases the amount of dust stirred up from unpaved roads and lots. • Upgrade the road surface strength by improving particle size, shape, and mineral types that make up the surface and base materials: 4-40 Volume 11—Construction Stormwater Pollution Prevention February 2005 • Add surface gravel to reduce the source of dust emission. Limit the amount of fine particles(those smaller than .075 mm) to 10 to 20 percent. • Use geotextile fabrics to increase the strength of new roads or roads undergoing reconstruction. • Encourage the use of alternate,paved routes, if available. • Restrict use by tracked vehicles and heavy trucks to prevent damage to road surface and base. • Apply chemical dust suppressants using the admix method, blending the produci with the top few inches of surface material. Suppressants may also be applied as surface treatments. • Pave unpaved permanent roads and other trafficked areas. • Use vacuum street sweepers. • Remove mud and other dirt promptly so it does not dry and then turn into dust. • Limit dust-causing work on windy days. • Contact your local Air Pollution Control Authority for guidance and training on other dust control measures. Compliance with the local Air Pollution Control Authority constitutes compliance with this BMP. Maintenance Respray area as necessary to keep dust to a minimum. Standards February 2005 Volume 11—Construction Stormwater Pollution Prevention 4-41 BMP C150: Materials On Hand Purpose Quantities of erosion prevention and sediment control materials can be kept on the project site at all times to be used for emergency situations such as unexpected heavy summer rains. Having these materials on-site reduces the time needed to implement BMPs when inspections indicate that existing BMPs are not meeting the Construction SWPPP requirements. In addition,contractors can save money by buying some materials in bulk and storing them at their office or yard. Conditions of Use Construction projects of any size or type can benefit from having materials on hand. A small commercial development project could have a roll of plastic and some gravel available for immediate protection of bare soil and temporary berm construction. A large earthwork project, such as highway construction, might have several tons of straw, several rolls of plastic, flexible pipe, sandbags, geotextile fabric and steel"T"posts. • Materials are stockpiled and readily available before any site clearing, grubbing, or earthwork begins. A large contractor or developer could keep a stockpile of materials that are available to be used on several projects. • If storage space at the project site is at a premium, the contractor could maintain the materials at their office or yard. The office or yard must be less than an hour from the project site. Design and Depending on project type, size, complexity, and length, materials and Installation quantities will vary. A good minimum that will cover numerous situations Specifications includes: Material Measure Quantity Clear Plastic, 6 mil 100 foot roll 1-2 -Drainpipe, 6 or 8 inch diameter 25 foot section 4-6 Sandbags, filled each 25-50 Straw Bales for mulching, approx. 50#each 10-20 Quarry S ails ton 2-4 Washed Gravel cubic yard 2-4 Geotextile Fabric 100 foot roll 1-2 Catch Basin Inserts each 2-4 Steel"T" Posts each 12-24 Maintenance • All materials with the exception of the quarry spalls, steel"T"posts, Standards and gravel should be kept covered and out of both sun and rain. • Re-stock materials used as needed. 4-42 Volume 1l—Construction Stormwater Pollution Prevention February 2005 BMP C151: Concrete Handling Purpose Concrete work can generate process water and slurry that contain fine particles and high pH,both of which can violate water quality standards in the receiving water. This BMP is intended to minimize and eliminate concrete process water and slurry from entering waters of the state. Conditions of Use Any time concrete is used,these management practices shall be utilized. Concrete construction projects include, but are not limited to, the following: • Curbs • Sidewalks • Roads • Bridges • Foundations • Floors • Runways Design and • Concrete truck chutes,pumps,and internals shall be washed out only Installation into formed areas awaiting installation of concrete or asphalt. Specifications • Unused concrete remaining in the truck and pump shall be returned to the originating batch plant for recycling. • Hand tools including, but not limited to, screeds, shovels, rakes, floats, and trowels shall be washed off only into formed areas awaiting installation of concrete or asphalt. • Equipment that cannot be easily moved, such as concrete pavers, shall only be washed in areas that do not directly drain to natural or constructed stormwater conveyances. • Washdown from areas such as concrete aggregate driveways shall not drain directly to natural or constructed stormwater conveyances. • When no formed areas are available, washwater and leftover product shall be contained in a lined container. Contained concrete shall be disposed of in a manner that does not violate groundwater or surface water quality standards. Maintenance Containers shall be checked for holes in the liner daily during concrete Standards pours and repaired the same day. February 2005 Volume 11—Construction Stormwater Pollution Prevention 4-43 BMP C152: Sawcutting and Surfacing Pollution Prevention Purpose Sawcutting and surfacing operations generate slurry and process water that contains fine particles and high pH(concrete cutting), both of which can violate the water quality standards in the receiving water. This BMP is intended to minimize and eliminate process water and slurry from entering waters of the State. Conditions of Use Anytime sawcutting or surfacing operations take place, these management practices shall be utilized. Sawcutting and surfacing operations include, but are not limited to, the following: • Sawing • Coring • Grinding • Roughening • Hydro-demolition • Bridge and road surfacing Design and • Slurry and cuttings shall be vacuumed during cutting and surfacing Installation operations. Specifications • Slurry and cuttings shall not remain on permanent concrete or asphalt pavement overnight. • Slurry and cuttings shall not drain to any natural or constructed drainage conveyance. • Collected slurry and cuttings shall be disposed of in a manner that does not violate groundwater or surface water quality standards. • Process water that is generated during hydro-demolition, surface roughening or similar operations shall not drain to any natural or constructed drainage conveyance and shall be disposed of in a manner that does not violate groundwater or surface water quality standards. • Cleaning waste material and demolition debris shall be handled and disposed of in a manner that does not cause contamination of water. If the area is swept with a pick-up sweeper, the material must be hauled out of the area to an appropriate disposal site. Maintenance Continually monitor operations to determine whether slurry, cuttings, or Standards process water could enter waters of the state. If inspections show that a violation of water quality standards could occur, stop operations and immediately implement preventive measures such as berms, barriers, secondary containment, and vacuum trucks. 4-44 Volume I/—Construction Stormwater Pollution Prevention February 2005 BMP C153: Material Delivery, Storage and Containment Purpose Prevent, reduce, or eliminate the discharge of pollutants from material delivery and storage to the stormwater system or watercourses by minimizing the storage of hazardous materials onsite, storing materials in a designated area, and installing secondary containment. Conditions of Use These procedures are suitable for use at all construction sites with delivery and storage of the following materials: • Petroleum products such as fuel, oil and grease • Soil stabilizers and binders (e.g. Polyacrylamide) • Fertilizers,pesticides and herbicides • Detergents • Asphalt and concrete compounds • Hazardous chemicals such as acids, lime, adhesives, paints, solvents and curing compounds • Any other material that may be detrimental if released to the environment Design and The following steps should be taken to minimize risk: Installation Temporary storage area should be located away from vehicular traffic, Specifications near the construction entrance(s), and away from waterways or storm drains. • Material Safety Data Sheets (MSDS) should be supplied for all materials stored. Chemicals should be kept in their original labeled containers. • Hazardous material storage on-site should be minimized. • Hazardous materials should be handled as infrequently as possible. • During the wet weather season(Oct 1 —April 30), consider storing materials in a covered area. • Materials should be stored in secondary containments, such as earthen dike, horse trough, or even a children's wading pool for non-reactive materials such as detergents, oil, grease, and paints. Small amounts of material may be secondarily contained in"bus boy" trays or concrete mixing trays. • Do not store chemicals, drums, or bagged materials directly on the ground. Place these items on a pallet and, when possible, in secondary containment. February 2005 Volume 1l—Construction Stormwater Pollution Prevention 4-45 • If drums must be kept uncovered, store them at a slight angle to reduce ponding of rainwater on the lids to reduce corrosion. Domed plastic covers are inexpensive and snap to the top of drums,preventing water from collecting. Material Storage Areas and Secondary Containment Practices: • Liquids, petroleum products, and substances listed in 40 CFR Parts 110, 117, or 302 shall be stored in approved containers and drums and shall not be overfilled. Containers and drums shall be stored in temporary secondary containment facilities. • Temporary-secondary containment facilities shall provide for a spill containment volume able to contain precipitation from a 25 year, 24 hour storm event,plus 10% of the total enclosed container volume of all containers, or 110% of the capacity of the largest container within its boundary, whichever is greater. • Secondary containment facilities shall be impervious to the materials stored therein for a minimum contact time of 72 hours. • Secondary containment facilities shall be maintained free of accumulated rainwater and spills. In the event of spills or leaks, accumulated rainwater and spills shall be collected and placed into drums. These liquids shall be handled as hazardous waste unless testing determines them to be non-hazardous. • Sufficient separation should be provided between stored containers to allow for spill cleanup and emergency response access. • During the wet weather season(Oct I —April 30), each secondary containment facility shall be covered during non-working days,prior to and during rain events. • Keep material storage areas clean, organized and equipped with an ample supply of appropriate spill clean-up material(spill kit). • The spill kit should include, at a minimum: 1-Water Resistant Nylon Bag • 3-011 Absorbent Socks 3"x 4' 2-011 Absorbent Socks 3"x 10' • 12-011 Absorbent Pads 17"x19" • 1-Pair Splash Resistant Goggles • 3-Pair Nitrile Gloves • 10-Disposable Bags with Ties • Instructions 4-46 Volume 11—Construction Stormwater Pollution Prevention February 2005 BMP C160: Certified Erosion and Sediment Control Lead Purpose The project proponent designates at least one person as the responsible representative in charge of erosion and sediment control (ESC),and water quality protection. The designated person shall be the Certified Erosion and Sediment Control Lead(CESCL) who is responsible for ensuring compliance with all local, state, and federal erosion and sediment control and water quality requirements. Conditions of Use A CESCL shall be made available on projects one acre or larger that discharge stormwater to surface waters of the state • The CESCL shall: • Have a current certificate proving attendance in an erosion and sediment control training course that meets the minimum ESC training and certification requirements established by Ecology (see details below). Ecology will maintain a list of ESC training and certification providers at: www.ecy.wa.gov/programs/wq/stormwater. OR • Be a Certified Professional in Erosion and Sediment Control (CPESC); for additional information go to: www.cpesc.net Specifications . Certification shall remain valid for three years. • The CESCL shall have authority to act on behalf of the contractor or developer and shall be available, on call, 24 hours per day throughout the period of construction. • The Construction SWPPP shall include the name, telephone number, fax number, and address of the designated CESCL. A CESCL may provide inspection and compliance services for multiple construction projects in the same geographic region. Duties and responsibilities of the CESCL shall include, but are not limited to the following: • Maintaining permit file on site at all times which includes the SWPPP and any associated permits and plans. • Directing BMP installation, inspection, maintenance, modification, and removal. • Updating all project drawings and the Construction SWPPP with changes made. February 2005 Volume 11—Construction Stormwater Pollution Prevention 4-47 • Keeping daily logs, and inspection reports. Inspection reports should include: • Inspection date/time. • Weather information; general conditions during inspection and approximate amount of precipitation since the last inspection. • A summary or list of all BMPs implemented, including observations of all erosion/sediment control structures or practices. The following shall be noted: 1)Locations of BMPs inspected, 2) Locations of BMPs that need maintenance, 3) Locations of BMPs that failed to operate as designed or intended, and 4) Locations of where additional or different BMPs are required. • Visual monitoring results, including a description of discharged stormwater. The presence of suspended sediment, turbid water, discoloration,and oil sheen shall be noted, as applicable. •Any water quality monitoring performed during inspection. •General comments and notes, including a brief description of any BMP repairs, maintenance or installations made as a result of the inspection. • Facilitate, participate in, and take corrective actions resulting from inspections performed by outside agencies or the owner. 4-48 Volume lI—Construction Stormwater Pollution Prevention February 2005 Minimum Requirements for ESC Training and Certification Courses General Requirements 1. The course shall teach the construction stormwater pollution prevention guidance provided in the most recent version of: a. The Washington State Dept. of Ecology Stormwater Management Manual for Western Washington, b. Other equivalent stonmwater management manuals approved by Ecology. 2. Upon completion of course, each attendee shall receive documentation of certification, including, at a minimum, a wallet-sized card that certifies completion of the course. Certification shall remain valid for three years. Recertification may be obtained by completing the 8-hour refresher course or by taking the initial 16-hour training course again. 3. The initial certification course shall be a minimum of 16 hours (with a reasonable time allowance for lunch, breaks, and travel to and from field)and include a field element and test. a. The field element must familiarize students with the proper installation, maintenance and inspection of common erosion and sediment control BMPs including,but not limited to, blankets, check dams, silt fence, straw mulch, plastic, and seeding. b. The test shall be open book and a passing score is not required for certification. Upon completion of the test, the correct answers shall be provided and discussed. 4. The refresher course shall be a minimum of 8 hours and include a test. a. The refresher course shall include: i. Applicable updates to the Stormwater Management Manual that is used to teach the course, including new or updated BMPs; and ii. Applicable changes to the NPDES General Permit for Construction Activities. b. The refresher course test shall be open book and a passing score is not required - for certification. Upon completion of the test, the correct answers shall be provided and discussed. c. The refresher course may be taught using an alternative format (e.g. internet, CD ROM,etc.) if the module is approved by Ecology. Required Course Elements 1. Erosion and Sedimentation Impacts a. Examples/Case studies February 2005 Volume /I—Construction Stormwater Pollution Prevention 4-49 2. Erosion and Sedimentation Processes a. Definitions b. Types of erosion c. Sedimentation I. Basic settling concepts ii. Problems with clays/turbidity 3. Factors Influencing Erosion Potential a. Soil b. Vegetation c. Topography d. Climate 4. Regulatory Requirements a. NPDES - Construction Stormwater General Permit b. Local requirements and permits c. Other regulatory requirements 5_ Stormwater Pollution Prevention Plan(SWPPP) a. SWPPP is a living document—should be revised as necessary b. 12 Elements of a SWPPP; discuss suggested BMPs (with examples) 1_ Mark Clearing Limits 2. Establish Construction Access 3. Control Flow Rates 4_ Install Sediment Controls 5. Stabilize Soils 6. Protect Slopes 7_ Protect Drain Inlets 8_ Stabilize Channels and Outlets 9. Control Pollutants 10. Control De-watering 11. Maintain BMPs 12. Manage the Project 6. Monitoring/Reporting/Recordkeeping a. Site inspections/visual monitoring i. Disturbed areas if. BMPs iii. Stormwater discharge points b. Water quality sampling/analysis i_ Turbidity it. pH c. Monitoring frequency i_ Set by NPDES permit ii. Inactive sites - reduced frequency 4-50 Volume !l—Construction Stormwater Pollution Prevention February 2005 d. Adaptive Management i. When monitoring indicates problem, take appropriate action (e.g. install/maintain BMPs) ii. Document the corrective action(s) in SWPPP c_ Reporting i. Inspection reports/checklists 11. Discharge Monitoring Reports(DMR) in. Non-compliance notification Instructor Qualifications 1. Instructors must be qualified'to effectively teach the required course elements. 2. At a minimum, instructors must have: a. Current certification as a Certified Professional in Erosion and Sediment Control (CPESC),or b. Completed a training program for teaching the required course elements, or c. The academic credentials and instructional experience necessary for teaching the required course elements. 3. Instructors must demonstrate competent instructional skills and knowledge of the applicable subject matter. l February 2005 Volume /t-Construction Stormwater Pollution Prevention 4-51 BMP C161: Payment of Erosion Control Work Purpose As with any construction operation, the contractor should be paid for erosion control work. Payment for erosion control must be addressed during project development and design. Method of payment should be identified in the SWPPP. Conditions of Use Erosion control work should never be"incidental" to the contract as it is extremely difficult for the contractor to bid the work. Work that is incidental to the contract is work where no separate measurement or payment is made. The cost for incidental work is included in payments made for applicable bid items in the Schedule of Unit Prices. For example, any erosion control work associated with an item called "Clearing and Grubbing" is bid and paid for as part of that item, not separately. Several effective means for payment of erosion control work are described below. These include: • Temporary Erosion and Sediment Control (TESC) Lump Sum. • TESC-Force Account. • Unit Prices_ • Lump Sum. TESC Lump Sum One good method for achieving effective erosion and sediment control is to set up a Progress Payment system whereby the contract spells out exactly what is expected and allows for monthly payments over the life of the contract. For example, an Item called "TESC Lump Sum"' is listed in the Bid Schedule of Unit Prices. An amount, such as $10,000, is written in both the Unit Price and Amount columns. This requires all bidders to bid $10,000 for the item. If$10,000 is not shown in the Amount column,each contractor bids the amount. Often this is under-bid, which can cause compliance difficulties later. In this example, the contractor is required to revise the project Construction SWPPP by developing a Contractor's Erosion and Sediment Control Plan(CESCP) that is specific to their operations. Next, the following language is included in the TESC specification Payment section: Based upon lump sum Bid Item"TESC Lump Sum', payments will be made as follows.- A. Upon receipt of the Contractors CESCP, 25 percent. B. After Notice To Proceed and before Substantial Completion, 50 percent will be pro rated and paid monthly for compliance with the 4-52 Volume 11—Construction Stormwater Pollution Prevention February 2005 CESCP. Non-compliance will result in withholding of payment for the month of non-compliance. C_ At Final Payment, 25 percent for a clean site. Payment for"TESC Lump Sum"will be full compensation for furnishing all labor, equipment, materials and tools to implement the CESCP, install, inspect, maintain, and remove temporary erosion and sediment controls as detailed in the drawings and specified herein, with the exception of those items measured and paid for separately. TESC Force Account One good method for ensuring that contingency money is available to address unforeseen erosion and sediment control problems is to set up an item called "TESC-Force Account". For example, an amount such as $15,000 is written in both the Unit Price and Amount columns for the item. This requires all bidders to bid $15,000 for the item. The Force Account is used only at the discretion of the contracting agency or developer. If there are no unforeseen erosion problems, the money is not used. If there are unforeseen erosion problems, the contracting agency would direct the work to be done and pay an agreed upon amount for the work (such as predetermined rates under a Time and Materials setting). Contract language for this item could look like this: Measurement and Payment for"TESC-Force Account"will be on a Force Account basis in accordance with (include appropriate section of the Contract Specifications). The amount entered in the Schedule of Unit Prices is an estimate. Unit Prices When the material or work can be quantified, it can be paid by Unit Prices. For example, the project designer knows that 2 acres will need to be hydroseeded and sets up an Item of Work for Hydroseed, with a Bid Quantity of 2, and a Unit for Acre. The bidder writes in the unit Prices _ and Amount. Unit Price items can be used in conjunction with TESC-Force Account and TESC-Lump Sum. Lump Sum In contracts where all the work in a project is paid as a Lump Sum, erosion control is usually not paid as a separate item. In order to ensure that appropriate amounts are bid into the contract, the contracting agency can request a Schedule of Values and require that all erosion control costs be identified. February 2005 Volume ll—Construction Stormwater Pollution Prevention 4-53 BMP C162: Scheduling Purpose Sequencing a construction project reduces the amount and duration of soil exposed to erosion by wind, rain, runoff, and vehicle tracking. Conditions of Use The construction sequence schedule is an orderly listing of all major land- disturbing activities together with the necessary erosion and sedimentation control measures planned for the project. This type of schedule guides the contractor on work to be done before other work is started so that serious erosion and sedimentation problems can be avoided. Following a specified work schedule that coordinates the timing of land- disturbing activities and the installation of control measures is perhaps the most cost-effective way of controlling erosion during construction. The removal of surface ground cover leaves a site vulnerable to accelerated erosion. Construction procedures that limit land clearing, provide timely installation of erosion and sedimentation controls, and restore protective cover quickly can significantly reduce the erosion potential of a site. Design • Avoid rainy periods. Considerations . Schedule projects to disturb only small portions of the site at any one time. Complete grading as soon as possible_ Immediately stabilize the disturbed portion before grading the next portion. Practice staged seeding in order to revegetate cut and fill slopes as the work progresses. 4-54 Volume/I—Construction Stormwater Pollution Prevention February 2005 BMP C180: Small Project Construction Stormwater Pollution Prevention Purpose To prevent the discharge of sediment and other pollutants to the maximum extent practicable from small construction projects_ Conditions of Use On small construction projects, those adding or replacing less than 2,000 square feet of impervious surface or clearing less than 7,000 square feet. Design and Plan and implement proper clearing and grading of the site. It is most Installation important only to clear the areas needed, thus keeping exposed areas Specifications to a minimum. Phase clearing so that only those areas that are actively being worked are uncovered. Note_ Clearing limits should be flagged in the lot or area prior to initiating clearing. • Soil shall be managed in a manner that does not permanently compact or deteriorate the final soil and landscape system. If disturbance and/or compaction occur the impact must be corrected at the end of the construction activity. This shall include restoration of soil depth, soil - quality, permeability, and percent organic matter. Construction practices must not cause damage to or compromise the design of permanent landscape or infiltration areas. • Locate excavated basement soil a reasonable distance behind the curb, such as in the backyard or side yard area. This will increase the distance eroded soil must travel to reach the storm sewer system. Soil piles should be covered until the soil is either used or removed. Piles should be situated so that sediment does not run into the street or adjoining yards. • Backfill basement walls as soon as possible and rough grade the lot. This will eliminate large soil mounds, which are highly erodible, and prepares the lot for temporary cover, which will further reduce erosion potential. Remove excess soil from the site as soon as possible after backfilling. This will eliminate any sediment loss from surplus fill. • If a lot has a soil bank higher than the curb, a trench or berm should be installed moving the bank several feet behind the curb. This will reduce the occurrence of gully and rill erosion while providing a storage and settling area for stormwater. • The construction entrance should be stabilized where traffic will be leaving the construction site and traveling on paved roads or other paved areas within 1,000 feet of the site_ February 2005 Volume 11-Construction Stormwater Pollution Prevention 4-55 • Provide for periodic street cleaning to remove any sediment that may have been tracked out. Sediment should be removed by shoveling or sweeping and carefully removed to a suitable disposal area where it will not be re-eroded. • Utility trenches that run up and down slopes must be backfilled within seven days. Cross-slope trenches may remain open throughout construction to provide runoff interception and sediment trapping, provided that they do not convey turbid runoff off site. 4-56 Volume /!—Construction Stormwater Pollution Prevention February 2005 4.2 Runoff Conveyance and Treatment BMPs BMP C200: Interceptor Dike and Swale Purpose Provide a ridge of compacted soil, or a ridge with an upslope swale, at the top or base of a disturbed slope or along the perimeter of a disturbed construction area to convey stormwater. Use the dike and/or Swale to intercept the runoff from unprotected areas and direct it to areas where erosion can be controlled. This can prevent storm runoff from entering the work area or sediment-laden runoff from leaving the construction site_ Conditions of Use Where the runoff from an exposed site or disturbed slope must be conveyed to an erosion control facility which can safely convey the stormwater. • Locate upslope of a construction site to prevent runoff from entering disturbed area. When placed horizontally across a disturbed slope, it reduces the amount and velocity of runoff flowing down the slope. Locate downslope to collect runoff from a disturbed area and direct it to a sediment basin. Design and . Dike and/or Swale and channel must be stabilized with temporary or Installation permanent vegetation or other channel protection during construction. Specifications . Channel requires a positive grade for drainage; steeper grades require channel protection and check dams. • Review construction for areas where overtopping may occur. • Can be used at top of new fill before vegetation is established. May be used as a permanent diversion channel to carry the runoff. • Sub-basin tributary area should be one acre or less. • Design capacity for the peak flow from a 10-year, 24-hour storm, assuming a Type IA rainfall distribution, for temporary facilities. Alternatively, use 1.6 times the I0-year, I-hour flow indicated by an approved continuous runoff model. For facilities that will also serve on a permanent basis, consult the local government's drainage requirements. Interceptor dikes shall meet the following criteria: Top Width 2 feet minimum. Height 1.5 feet minimum on berm. Side Slope 2:1 or flatter. Grade Depends on topography, however, dike system minimum is 0.5%, maximum is 1%. Compaction Minimum of 90 percent ASTM D698 standard proctor. February 2005 Volume 11—Construction Stormwater Pollution Prevention 4-57 Horizontal Spacing of Interceptor Dikes: Average Slope Slope Percent Flowpath Length 20H:1 V or less 3-5% 300 feet (10 to 20)H:1 V 5-10% 200 feet (4 to ]0)H:I V 10-25% 100 feet (2 to 4)H:1 V 25-50% 50 feet Stabilization depends on velocity and reach Slopes <5% Seed and mulch applied within 5 days of dike construction (see BMP C121, Mulching). Slopes 5 -40% Dependent on runoff velocities and dike materials. Stabilization should be done immediately using either sod or riprap or other measures to avoid erosion. • The upslope side of the dike shall provide positive drainage to the dike outlet. No erosion shall occur at the outlet. Provide energy dissipation measures as necessary. Sediment-laden runoff must be released through a sediment trapping facility. • Minimize construction traffic over temporary dikes. Use temporary cross culverts for channel crossing. Interceptor swales shall meet the following criteria: Bottom Width 2 feet minimum; the bottom shall be level. Depth I-foot minimum. Side Slope 2:1 or flatter. Grade Maximum 5 percent, with positive drainage to a suitable outlet(such as a sediment pond). Stabilization Seed as per BMP C120, Temporary and Permanent Seeding,or BMP C202, Channel Lining, 12 inches thick of riprap pressed into the bank and extending at least 8 inches vertical from the bottom. • Inspect diversion dikes and interceptor swales once a week and after every rainfall. Immediately remove sediment from the flow area. • Damage caused by construction traffic or other activity must be repaired before the end of each working day. Check outlets and make timely repairs as needed to avoid gully formation. When the area below the temporary diversion dike is permanently stabilized, remove the dike and fill and stabilize the channel to blend with the natural surface. 4-58 Volume 11—Construction Stormwater Pollution Prevention February 2005 BMP C201: Grass-Lined Channels Purpose To provide a channel with a vegetative lining for conveyance of runoff. See Figure 4.7 for typical grass-lined channels. Conditions of Use This practice applies to construction sites where concentrated runoff nee& to be contained to prevent erosion or flooding. • When a vegetative lining can provide sufficient stability for the channel cross section and at lower velocities of water(normally dependent on grade). This means that the channel slopes are generally less than 5 percent and space is available for a relatively large cross section. • Typical uses include roadside ditches, channels at property boundaries, outlets for diversions, and other channels and drainage ditches in low areas. • Channels that will be vegetated should be installed before major earthwork and hydroseeded with a bonded fiber matrix (BFM). The vegetation should be well established(i.e., 75 percent cover)before water is allowed to flow in the ditch. With channels that will have high flows, erosion control blankets should be installed over the hydroseed. If vegetation cannot be established from seed before water is allowed in the ditch, sod should be installed in the bottom of the ditch in lieu of hydromulch and blankets. Design and Locate the channel where it can conform to the topography and other Installation features such as roads. Specifications Locate them to use natural drainage systems to the greatest extent possible. • Avoid sharp changes in alignment or bends and changes in grade. • Do not reshape the landscape to fit the drainage channel. • The maximum design velocity shall be based on soil conditions, type of vegetation, and method of revegetation,but at no times shall velocity exceed 5 feet/second. The channel shall not be overtopped by the peak runoff from a 10-year, 24-hour storm,assuming a Type 1 A rainfall distribution." Alternatively, use 1.6 times the 10-year, 1-hour flow indicated by an approved continuous runoff model to determine a flow rate which the channel must contain. • Where the grass-lined channel will also function as a permanent stormwater conveyance facility,consultant the drainage conveyance requirements of the local government with jurisdiction. • An established grass or vegetated lining is required before the channel can be used to convey stormwater, unless stabilized with nets_ or blankets. February 2005 Volume 11—Construction Stormwater Pollution Prevention 4-59 • If design velocity of a channel to be vegetated by seeding exceeds 2 ft/sec, a temporary channel liner is required. Geotextile or special mulch protection such as fiberglass roving or straw and netting provide stability until the vegetation is fully established_ See Figure 4.9. • Check dams shall be removed when the grass has matured sufficiently - to protect the ditch or swale unless the slope of the Swale is greater than 4 percent. The area beneath the check dams shall be seeded and mulched immediately after dam removal. • If vegetation is established by sodding, the permissible velocity for established vegetation may be used and no temporary liner is needed. • Do not subject grass-lined channel to sedimentation from disturbed areas_ Use sediment-trapping BMPs upstream of the channel. • V-shaped grass channels generally apply where the quantity of water is small, such as in short reaches along roadsides. The V-shaped cross section is least desirable because it is difficult to stabilize the bottom where velocities may be high. • Trapezoidal grass channels are used where runoff volumes are large and slope is low so that velocities are nonerosive to vegetated linings. (Note: it is difficult to construct small parabolic shaped channels.) • Subsurface drainage, or riprap channel bottoms, may be necessary on sites that are subject to prolonged wet conditions due to long duration flows or a high water table. • Provide outlet protection at culvert ends and at channel intersections. • Grass channels, at a minimum, should carry peak runoff for temporary construction drainage facilities from the 10-year, 24-hour storm without eroding. Where flood hazard exists, increase the capacity according to the potential damage. • Grassed channel side slopes generally are constructed 3:1 or flatter to aid in the establishment of vegetation and for maintenance. • Construct channels a minimum of 0.2 foot larger around the periphery to allow for soil bulking during seedbed preparations and sod buildup. Maintenance During the establishment period, check grass-lined channels after every .Standards rainfall. • After grass is established, periodically check the channel; check it after every heavy rainfall event. Immediately make repairs. • It is particularly important to check the channel outlet and all road crossings for bank stability and evidence of piping or scour holes. • Remove all significant sediment accumulations to maintain the designed carrying capacity. Keep the grass in a healthy, vigorous condition at all times, since it is the primary erosion protection for the channel_ 4-60 Volume Il—Construction Stormwater Pollution Prevention February 2005 Typical V-Shaped Channel Cross-section a\O_Wv \\//\ Filter_ /. (150-225mm) \,\\ /\\� Fabric /i�/I Key in Fabric Grass-Lined L With Rock Center Typical Parabolic Channel Cross-Section 9*1 \/\�/\\/////\\j✓\\/,./ (1 Key 1n 02Fabr+ic / /\� Filter Fabric With Channel Liner With Rock Center for Base Flow Typical Trapezoidal Channel Cross-Section b\j lU I` . Design Depth �� 1+++v1VU i' vercut channel 2"(50mm) to allow bulking during seedbed preparation and growth of vegetation. Filter With Rock Center For Base Flow Fabric Figure 4.8—Typical Grass-Lined Channels February 2005 Volume 11—Construction Stormwater Pollution Prevention 4-61 Overlap 6"(150mm) minimum y Excavate Channel to Design /I -. ✓/ Grade and Cross Section yI I Design Depth \v\ OVERCUTCHANNEL �'� \ Longitudinal 2-(50mm) TOALLOW =u 1Vt anchor trench BUL/(ING OURING SEEORE9 `'/ tA�,/, Al N, ,Ii, PREPARATION 6'(t50mm) TYPICAL INSTALLATION /\\ WITH EROSION CONTROL ��/•• � _ � A/� i� �� BLANKETS OR TURF \\ \\ REINFORCEMENT MATS (150mm) i/\//\�/\/ `�\�%\\�, \(,SOmm/ \i`•,`\,.\��, Intermittent Check Slot Longitudinal Anchor Trench Shingle-lap spliced ends or begin new roll in an intermittent check slot ,L, �WV j-•V�✓ - W 0 W Prepare soil and apply seed before p installing blankets, mats or other temporary channel liner system �7 /> rc NOTES: I- Design velocities exceeding 2 ft/sec(0-5m/sec)require temporary blankets,mats or similar liners to protect seed and soil until vegetation becomes established- 2. Grass-lined channels with design velocities exceeding 6 ft/sec (2m/sec)should include turf reinforcement mats. Figure 4.9—Temporary Channel Liners 4-62 Volume 11—Construction Stormwater Pollution Prevention February 2005 BMP C202: Channel Lining Purpose To protect erodible channels by providing a channel liner using either blankets or riprap. Conditions of Use When natural soils or vegetated stabilized soils in a channel are not adequat( to prevent channel erosion. • When a permanent ditch or pipe system is to be installed and a temporary measure is needed. • In almost all cases, synthetic and organic coconut blankets are more effective than riprap for protecting channels from erosion. Blankets can be used with and without vegetation. Blanketed channels can be designed to handle any expected flow and longevity requirement. Some synthetic blankets have a predicted life span of 50 years or more, even in sunlight. • Other reasons why blankets are better than rock include the availability of blankets over rock. In many areas of the state, rock is not easily obtainable or is very expensive to haul to a site. Blankets can be delivered anywhere. Rock requires the use of dump trucks to haul and heavy equipment to place. Blankets usually only require laborers with hand tools, and sometimes a backhoe. _ • The Federal Highway Administration recommends not using flexible liners whenever the slope exceeds 10 percent or the shear stress exceeds 8 Ibs/ft2. Design and See BMP C 122 for information on blankets. Installation Since riprap is used where erosion potential is high,construction must be Specifications sequenced so that the riprap is put in place with the minimum possible delay. • Disturbance of areas where riprap is to be placed should be undertaken only when final preparation and placement of the riprap can follow immediately behind the initial disturbance. Where riprap is used for outlet protection, the riprap should be placed before or in conjunction with the construction of the pipe or channel so that it is in place when the pipe or channel begins to operate_ • The designer, after determining the riprap size that will be stable under the flow conditions, shall consider that size to be a minimum size and then, based on riprap gradations actually available in the area, select the size or sizes that equal or exceed the minimum size. The possibility of drainage structure damage by children shall be considered in selecting a riprap size, especially if there is nearby water or a gully in which to toss the stones. • Stone for riprap shall consist of field stone or quarry stone of approximately rectangular shape. The stone shall be hard and angular and of such quality that it will not disintegrate on exposure to water or February 2005 Volume 11— Construction Stormwater Pollution Prevention 4-63 weathering and it shall be suitable in all respects for the purpose intended. - • Rubble concrete may be used provided it has a density of at least 150 pounds per cubic foot, and otherwise meets the requirement of this standard and specification_ • A lining of engineering fitter fabric (geotextile)shall be placed between the riprap and the underlying soil surface to prevent soil movement into or through the riprap. The geotextile should be keyed in at the top of the bank. • Filter fabric shall not be used on slopes greater than 1-1/2:1 as slippage may occur. It should be used in conjunction with a layer of coarse aggregate(granular filter blanket)when the riprap to be placed is 12 inches and larger_ 4-64 Volume 11-Construction Stormwater Pollution Prevention February 2005 BMP C203: Water Bars Purpose A small ditch or ridge of material is constructed diagonally across a road or right-of-way to divert stormwater runoff from the road surface, wheel tracks,or a shallow road ditch. Conditions of use Clearing right-of-way and construction of access for power lines, pipelines, and other similar installations often require long narrow right-of-ways over sloping terrain. Disturbance and compaction promotes gully formation in these cleared strips by increasing the volume and velocity of runoff. Gully formation may be especially severe in tire tracks and ruts. To prevent gullying, runoff can often be diverted across the width of the right-of-way to undisturbed areas by using small predesigned diversions. • Give special consideration to each individual outlet area, as well as to the cumulative effect of added diversions. Use gravel to stabilize the diversion where significant vehicular traffic is anticipated. Design and Height: 8-inch minimum measured from the channel bottom to the ridge top Installation Specifications • Side slope of channel: 2:1 maximum; 3:1 or flatter when vehicles will cross. • Base width of ridge: 6-inch minimum. • Locate them to use natural drainage systems and to discharge into well vegetated stable areas. • Guideline for Spacing: Slope % Spacing(ft) < 5 125 5 - 10 100 10 - 20 75 20- 35 50 > 35 Use rock lined ditch • Grade of water bar and angle: Select angle that results in ditch slope less than 2 percent. • Install as soon as the clearing and grading is complete. Reconstruct when construction is complete on a section when utilities are being - installed. • Compact the ridge when installed. • Stabilize, seed and mulch the portions that are not subject to traffic. Gravel the areas crossed by vehicles. February 2005 Volume 11-Construction Stormwater Pollution Prevention 4-65 37aintenance Periodically inspect right-of-way diversions for wear and after every heavy Standards rainfall for erosion damage. • Immediately remove sediment from the flow area and repair the dike. • Check outlet areas and make timely repairs as needed. • When permanent road drainage is established and the area above the temporary right-of-way diversion is permanently stabilized, remove the dike and fill the channel to blend with the natural ground, and appropriately stabilize the disturbed area. 4-66 Volume 11—Construction Stormwater Pollution Prevention February 2005 BMP C204: Pipe Slope Drains Purpose To use a pipe to convey stormwater anytime water needs to be diverted away from or over bare soil to prevent gullies, channel erosion, and saturation of slide-prone soils. Conditions of Use Pipe slope drains should be used when a temporary or permanent stormwater conveyance is needed to move the water down a steep slope to avoid erosion(Figure 4.10). On highway projects, they should be used at bridge ends to collect runoff and pipe it to the base of the fill slopes along bridge approaches. These can be designed into a project and included as bid items. Another use on road projects is to collect runoff from pavement and pipe it away from side slopes_ These are useful because there is generally a time lag between having the first lift of asphalt installed and the curbs, gutters, and permanent drainage installed. Used in conjunction with sand bags,or other temporary diversion devices, these will prevent massive amounts of sediment from leaving a project. Water can be collected, channeled with sand bags,Triangular Silt Dikes, berms, or other material, and piped to temporary sediment ponds. Pipe slope drains can be: • Connected to new catch basins and used temporarily until all permanent piping is installed; • Used to drain water collected from aquifers exposed on cut slopes and take it to the base of the slope; • Used to collect clean runoff from plastic sheeting and direct it away from exposed soil; • Installed in conjunction with silt fence to drain collected water to a controlled area; • Used to divert small seasonal streams away from construction. They have been used successfully on culvert replacement and extension jobs. Large flex pipe can be used on larger streams during culvert removal, repair, or replacement; and, • Connected to existing down spouts and roof drains and used to divert water away from work areas during building renovation,demolition, and construction projects. There are now several commercially available collectors that are attached to the pipe inlet and help prevent erosion at the inlet. February 2005 Volume ll—Construction Stormwater Pollution Prevention 4-67 Design and Size the pipe to convey the flow. The capacity for temporary drains shall be Installation sufficient to handle the peak flow from a 10-year, 24-hour storm event, Specifications assuming a Type IA rainfall distribution. Alternatively, use 1.6 times the I0-year, I-hour flow indicated by an approved continuous runoff model. Consult local drainage requirements for sizing permanent pipe slope drains. • Use care in clearing vegetated slopes for installation. • Re-establish cover immediately on areas disturbed by installation. • Use temporary drains on new cut or fill slopes. - • Use diversion dikes or swales to collect water at the top of the slope. • Ensure that the entrance area is stable and large enough to direct flow into the pipe. • Piping of water through the berm at the entrance area is a common failure mode. • The entrance shall consist of a standard flared end section for culverts 12 inches and larger with a minimum 6-inch metal toe plate to prevent runoff from undercutting the pipe inlet. The slope of the entrance shall be at least 3 percent. Sand bags may also be used at pipe entrances as a temporary measure. • The soil around and under the pipe and entrance section shall be thoroughly compacted to prevent undercutting. • The flared inlet section shall be securely connected to the slope drain and have watertight connecting bands. • Slope drain sections shall be securely fastened together, fused or have gasketed watertight fittings, and shall be securely anchored into the soil. • Thrust blocks should be installed anytime 90 degree bends are utilized. Depending on size of pipe and flow, these can be constructed with j sand bags, straw bales staked in place, "t"posts and wire, or ecology blocks. • Pipe needs to be secured along its full length to prevent movement. This can be done with steel "t"posts and wire_ A post is installed on each side of the pipe and the pipe is wired to them. This should be done every 10-20 feet of pipe length or so, depending on the size of the pipe and quantity of water to diverted. • Interceptor dikes shall be used to direct runoff into a slope drain. The height of the dike shall be at least I foot higher at all points than the top of the inlet pipe. • The area below the outlet must be stabilized with a riprap apron(see BMP C209 Outlet Protection, for the appropriate outlet material). 4-68 Volume 11—Construction Stormwater Pollution Prevention February 2005 i • If the pipe slope drain is conveying sediment-laden water, direct all flows into the sediment trapping facility. • Materials specifications for any permanent piped system shall be set by the local government_ Maintenance Check inlet and outlet points regularly, especially after storms. Standards The inlet should be free of undercutting, and no water should be going around the point of entry. If there are problems, the headwall should be reinforced with compacted earth or sand bags. • The outlet point should be free of erosion and installed with appropriate outlet protection. • For permanent installations, inspect pipe periodically for vandalism and physical distress such as slides and wind-throw. • Normally the pipe slope is so steep that clogging is not a problem with smooth wall pipe, however, debris may become lodged in the pipe. Dike material compacted 900/6 modified proctor CPEP or equivalent pipe _ Interceptor Dike Provide nprap pad _J— �� or equivalent energy — dissipation Discharge to a stabilized % T J watercourse,sediment retention ( Standard andard flared facility,or stabilized outlet end section r r Inlet and all sections must be securely fastened together with gasketed watertight fittings Figure 4.10 - Pipe Slope Drain February 2005 Volume 11-Construction Stormwater Pollution Prevention 4-69 BMP C205: Subsurface Drains Purpose To intercept,collect, and convey ground water to a satisfactory outlet, using a perforated pipe or conduit below the ground surface. Subsurface drains are also known as"french drains." The perforated pipe provides a dewatering mechanism to drain excessively wet soils, provide a stable base for construction, improve stability of structures with shallow foundations, or to reduce hydrostatic pressure to improve slope stability. Conditions of Use Use when excessive water must be removed from the soil. The soil permeability, depth to water table and impervious layers are all factors which may govern the use of subsurface drains. Design and Relief drains are used either to lower the water table in large,relatively Installation flat areas, improve the growth of vegetation, or to remove surface water. Specifications They are installed along a slope and drain in the direction of the slope. They can be installed in a grid pattern, a herringbone pattern, or a random pattern. • Interceptor drains are used to remove excess ground water from a slope, stabilize steep slopes, and lower the water table immediately below a slope to prevent the soil from becoming saturated. They are installed perpendicular to a slope and drain to the side of the slope. They usually consist of a single pipe or series of single pipes instead of a patterned layout. • Depth and spacing of interceptor drains--The depth of an interceptor drain is determined primarily by the depth to which the water table is to be lowered or the depth to a confining layer. For practical reasons, the maximum depth is usually limited to 6 feet, with a minimum cover of 2 feet to protect the conduit. • The soil should have depth and sufficient permeability to permit installation of an effective drainage system at a depth of 2 to 6 feet. • An adequate outlet for the drainage system must be available either by gravity or by pumping. • The quantity and quality of discharge needs to be accounted for in the receiving stream(additional detention may be required). • This standard does not apply to subsurface drains for building _ foundations or deep excavations. • The capacity of an interceptor drain is determined by calculating the maximum rate of ground water flow to be intercepted. Therefore, it is good practice to make complete subsurface investigations, including 4-70 Volume 11—Construction Stormwater Pollution Prevention February 2005 hydraulic conductivity of the soil, before designing a subsurface drainage system. • Size of drain--Size subsurface drains to carry the required capacity without pressure flow. Minimum diameter for a subsurface drain is 4 inches. • The minimum velocity required to prevent silting is 1.4 ft./sec. The line shall be graded to achieve this velocity at a minimum. The maximum allowable velocity using a sand-gravel filter or envelope is 9 ft/sec. • Filter material and fabric shall be used around all drains for proper bedding and filtration of fine materials. Envelopes and filters should surround the drain to a minimum of 3-inch thickness. • The outlet of the subsurface drain shall empty into a sediment pond through a catch basin. If free of sediment, it can then empty into a receiving channel, swale, or stable vegetated area adequately protected from erosion and undermining. • The trench shall be constructed on a continuous grade with no reverse grades or low spots_ • Soft or yielding soils under the drain shall be stabilized with gravel or other suitable material. Backfilling shall be done immediately after placement of the pipe. No sections of pipe shall remain uncovered overnight or during a rainstorm. Backfill material shall be placed in the trench in such a manner that the drain pipe is not displaced or damaged. • Do not install permanent drains near trees to avoid the tree roots that tend to clog the line. Use solid pipe with watertight connections where it is necessary to pass a subsurface drainage system through a stand of trees. • Outlet--Ensure that the outlet of a drain empties into a channel or other watercourse above the normal water level. • Secure an animal guard to the outlet end of the pipe to keep out rodents. • Use outlet pipe of corrugated metal,cast iron, or heavy-duty plastic without perforations and at least 10 feet long. Do not use an envelope or filter material around the outlet pipe, and bury at least two-thirds of the pipe length. • When outlet velocities exceed those allowable for the receiving stream, outlet protection must be provided. February 2005 Volume 1!— Construction Stormwater Pollution Prevention 4-71 Maintenance Subsurface drains shall be checked periodically to ensure that they are Standards free-flowing and not clogged with sediment or roots. • The outlet shall be kept clean and free of debris. • Surface inlets shall be kept open and free of sediment and other debris. • Trees located too close to a subsurface drain often clog the system with their roots_ If a drain becomes clogged, relocate the drain or remove the trees as a last resort. Drain placement should be planned to minimize this problem. • Where drains are crossed by heavy vehicles, the line shall be checked to ensure that it is not crushed. 4-72 Volume/I—Construction Stormwater Pollution Prevention February 2005 BMP C206: Level Spreader Purpose To provide a temporary outlet for dikes and diversions consisting of an excavated depression constructed at zero grade across a slope. To convert concentrated runoff to sheet flow and release it onto areas stabilized by existing vegetation or an engineered filter strip. Conditions of Use Used when a concentrated flow of water needs to be dispersed over a large area with existing stable vegetation. • Items to consider are: 1. What is the risk of erosion or damage if the flow may become concentrated? 2. is an easement required if discharged to adjoining property? 3. Most of the flow should be as ground water and not as surface flow. 4. Is there an unstable area downstream that cannot accept additional ground water? • Use only where the slopes are gentle, the water volume is relatively low, and the soil will adsorb most of the low flow events_ Design and Use above undisturbed areas that are stabilized by existing vegetation. Installation If the level spreader has any low points, flow will concentrate,create - Specifications channels and may cause erosion. • Discharge area below the outlet must be uniform with a slope of less than 5H:IV. • Outlet to be constructed level in a stable, undisturbed soil profile(not- on fill)_ • The runoff shall not reconcentrate after release unless intercepted by another downstream measure. • The grade of the channel for the last 20 feet of the dike or interceptor entering the level spreader shall be less than or equal to 1 percent. The grade of the level spreader shall be 0 percent to ensure uniform spreading of storm runoff. • A 6-inch high gravel berm placed across the level lip shall consist of washed crushed rock,2-to 4-inch or 3/4-inch to I Vz-inch size. • The spreader length shall be determined by estimating the peak flow expected from the I 0-year, 24-hour design storm. The length of the spreader shall be a minimum of 15 feet for 0.1 cfs and shall be 10 feet for each 0.1 cfs there after to a maximum of 0.5 cfs per spreader. Use multiple spreaders for higher flows. • The width of the spreader should be at least 6 feet. February 2005 Volume I!—Construction Stormwater Pollution Prevention 4-73 • The depth of the spreader as measured from the lip should be at least 6 inches and it should be uniform across the entire length. • Level spreaders shall be setback from the property line unless there is an easement for flow. • Level spreaders, when installed every so often in grassy swales, keep the flows from concentrating. Materials that can be used include sand bags, lumber, logs,concrete, and pipe. To function properly, the material needs to be installed level and on contour. Figures 4.1 1 and 4.12 provide a cross-section and a detail of a level spreader. Maintenance The spreader should be inspected after every runoff event to ensure that it Standards is functioning correctly. • The contractor should avoid the placement of any material on the structure and should prevent construction traffic from crossing over the structure. • If the spreader is damaged by construction traffic, it shall be immediately repaired. Densely vegetated for a Pressure-Treated 2"x10" Min. of 100'and slope +" less than 5 1 .� VIT 1'Min 11 Imo' -� 3'Min.-� Figure 4.11 —Cross Section of Level Spreader Treated 2"x10"may be abutted end to Spreader must be level end for max, spreader length of 50' 6"min_ I"Min. I_I 6"min. I=III llllll_ - - - „- - - - _ _ IIIIIII Illtlltll� itili��ilIi��liI�E�III��IIEHIII��Illi=,IIItIItll� i Iltlltlli-� 18"min. rebar supports 8'max.spacing Figure 4.12 - Detail of Level Spreader 4-74 Volume 11—Construction Stormwater Pollution Prevention February 2005 BMP C207: Check Dams Purpose Construction of small dams across a swale or ditch reduces the velocity of concentrated flow and dissipates energy at the check dam. Conditions of Use Where temporary channels or permanent channels are not yet vegetated, channel lining is infeasible, and velocity checks are required. • Check dams may not be placed in streams unless approved by the State Department of Fish and Wildlife. Check dams may not be placed in wetlands without approval from a permitting agency. • Check dams shall not be placed below the expected backwater from any salmonid bearing water between October I and May 31 to ensure that there is no loss of high flow refuge habitat for overwintering juvenile salmonids and emergent salmonid fry. Design and Whatever material is used, the dam should form a triangle when viewed Installation from the side. This prevents undercutting as water flows over the face of Specifications the dam rather than falling directly onto the ditch bottom. Check dams in association with sumps work more effectively at slowing _ flow and retaining sediment than just a check dam alone. A deep sump should be provided immediately upstream of the check dam. • In some cases, if carefully located and designed, check dams can remain as permanent installations with very minor regrading. They may be left as either spillways, in which case accumulated sediment would be graded and seeded, or as check dams to prevent further sediment from leaving the site. • Check dams can be constructed of either rock or pea-gravel filled bags. Numerous new products are also available for this purpose. They tend to be re-usable,quick and easy to install, effective, and cost efficient. • Check dams should be placed perpendicular to the flow of water. • The maximum spacing between the dams shall be such that the toe of the upstream dam is at the same elevation as the top of the downstream dam. • Keep the maximum height at 2 feet at the center of the dam. • Keep the center of the check dam at least 12 inches lower than the outer edges at natural ground elevation. • Keep the side slopes of the check dam at 2:1 or flatter. • Key the stone into the ditch banks and extend it beyond the abutments a minimum of 18 inches to avoid washouts from overflow around the dam. February 2005 Volume 11—Construction Stormwater Pollution Prevention 4-75 • Use filter fabric foundation under a rock or sand bag check dam. If a blanket ditch liner is used, this is not necessary. A piece of organic or synthetic blanket cut to fit will also work for this purpose. • Rock check dams shall be constructed of appropriately sized rock. The rock must be placed by hand or by mechanical means(no dumping of rock to form dam) to achieve complete coverage of the ditch or Swale and to ensure that the center of the dam is lower than the edges. The rock used must be large enough to stay in place given the expected design flow through the channel. • In the case of grass-lined ditches and swales, all check dams and accumulated sediment shall be removed when the grass has matured sufficiently to protect the ditch or swale- unless the slope of the swale is greater than 4 percent. The area beneath the check dams shall be seeded and mulched immediately after dam removal. • Ensure that channel appurtenances, such as culvert entrances below check dams, are not subject to damage or blockage from displaced stones. Figure 4.13 depicts a typical rock check dam. Maintenance Check dams shall be monitored for performance and sediment Standards accumulation during and after each runoff producing rainfall. Sediment shall be removed when it reaches one half the sump depth. • Anticipate submergence and deposition above the check dam and erosion from high flows around the edges of the dam. • If significant erosion occurs between dams, install a protective riprap liner in that portion of the channel. 4-76 Volume 11—Construction Stormwater Pollution Prevention February 2005 View Looking Upstream 18 (o.5m) A E , 12"(150mm) 24"(0.6m) Do�Q O.oO�a o�/000��._�..�. NOTE: aD Do o Key stone into channel banks and extend it beyond the abutments a minimum of 18"(0.5m)to prevent A flow around dam. Section A - A FLOW �— 24"(0.6m) o O,Oo� o0 °pro o0< 8' (2.4m) - Spacing Between Check Dams •L'= the distance such that points•A'and •B'are of equal elevation. p' ° °goo-0 POINT'A' POINT B' NOT TO SCALE Figure 4.13—Check Dams February 2005 Volume 11—Construction Stormwater Pollution Prevention 4-77 BMP C208: Triangular Silt Dike (Geotextile-Encased Check Dam) Purpose Triangular silt dikes may be used as check dams, for perimeter protection, for temporary soil stockpile protection, for drop inlet protection, or as a temporary interceptor dike. Conditions of use May be used in place of straw bales for temporary check dams in ditches of any dimension. • May be used on soil or pavement with adhesive or staples. • TSDs have been used to build temporary: 1. sediment ponds; 2. diversion ditches; 3. concrete wash out facilities; 4. curbing; 5. water bars; b. level spreaders; and, 7. berms. Design and Made of urethane foam sewn into a woven geosynthetic fabric. Installation It is triangular, 10 inches to 14 inches high in the center, with a 20-inch to Specifications 28-inch base. A 2—foot apron extends beyond both sides of the triangle along its standard section of 7 feet. A sleeve at one end allows attachment of additional sections as needed. • Install with ends curved up to prevent water from flowing around the ends. • The fabric flaps and check dam units are attached to the ground with wire staples. Wire staples should be No. I 1 gauge wire and should be 200 mm to 300 mm in length. • When multiple units are installed, the sleeve of fabric at the end of the unit shall overlap the abutting unit and be stapled. • Check dams should be located and installed as soon as construction will allow. • Check dams should be placed perpendicular to the flow of water. • When used as check dams,the leading edge must be secured with rocks, sandbags,or a small key slot and staples. • In the case of grass-lined ditches and swales, check dams and accumulated sediment shall be removed when the grass has matured sufficiently to protect the ditch or swale unless the slope of the swale is greater than 4 percent. The area beneath the check dams shall be seeded and mulched immediately after dam removal. Maintenance • Triangular silt dams shall be monitored for performance and sediment Standards accumulation during and after each runoff producing rainfall- 4-78 Volume lI—Construction Stormwater Pollution Prevention February 2005 Sediment shall be removed when it reaches one half the height of the dam. • Anticipate submergence and deposition above the triangular silt dam and erosion from high flows around the edges of the dam. Immediately repair any damage or any undercutting of the dam. February 2005 Volume 11—Construction Stormwater Pollution Prevention 4-79 BMP C209: Outlet Protection Purpose Outlet protection prevents scour at conveyance outlets and minimizes the potential for downstream erosion by reducing the velocity of concentrated stormwater flows. Conditions of use Outlet protection is required at the outlets of all ponds,pipes,ditches, or other conveyances, and where runoff is conveyed to a natural or manmade drainage feature such as a stream, wetland, lake, or ditch. Design and The receiving channel at the outlet of a culvert shall be protected from Installation erosion by rock lining a minimum of 6 feet downstream and extending up Specifications the channel sides a minimum of 1—foot above the maximum tailwater elevation or I-foot above the crown, whichever is higher. For large pipes (more than 18 inches in diameter), the outlet protection lining of the channel is lengthened to four times the diameter of the culvert. • Standard wingwalls, and tapered outlets and paved channels should also be considered when appropriate for permanent culvert outlet protection. (See WSDOT Hydraulic Manual, available through WSDOT Engineering Publications). • Organic or synthetic erosion blankets, with or without vegetation, are usually more effective than rock, cheaper, and easier to install. Materials can be chosen using manufacturer product specifications. ASTM test results are available for most products and the designer can - choose the correct material for the expected flow. • With low flows, vegetation(including sod) can be effective. • The following guidelines shall be used for riprap outlet protection: 1. If the discharge velocity at the outlet is less than 5 fps(pipe slope less than 1 percent), use 2-inch to 8-inch riprap. Minimum thickness is 1-foot. 2. For 5 to 10 fps discharge velocity at the outlet(pipe slope less than 3 percent), use 24-inch to 4-foot riprap. Minimum thickness is 2 feet. 3. For outlets at the base of steep slope pipes(pipe slope greater than 10 percent), an engineered energy dissipater shall be used. • Filter fabric or erosion control blankets should always be used under riprap to prevent scour and channel erosion. • New pipe outfalls can provide an opportunity for low-cost fish habitat improvements. For example, an alcove of low-velocity water can be created by constructing the pipe outfall and associated energy dissipater back from the stream edge and digging a channel, over- widened to the upstream side, from the outfall. Overwintering juvenile and migrating adult salmonids may use the alcove as shelter during 4-80 Volume 11—Construction Stormwater Pollution Prevention February 2005 high flows. Bank stabilization, bioengineering, and habitat features may be required for disturbed areas. See Volume V for more information on outfall system design. Maintenance • Inspect and repair as needed. Standards • Add rock as needed to maintain the intended function. • Clean energy dissipater if sediment builds up. February 2005 Volume /I— Construction Stormwater Pollution Prevention 4-81 BMP C220: Storm Drain Inlet Protection Purpose To prevent coarse sediment from entering drainage systems prior to permanent stabilization of the disturbed area. Conditions of Use Where storm drain inlets are to be made operational before permanent stabilization of the disturbed drainage area. Protection should be provided for all storm drain inlets downslope and within 500 feet of a disturbed or construction area, unless the runoff that enters the catch basin will be conveyed to a sediment pond or trap. Inlet protection may be used anywhere to protect the drainage system. It is likely that the drainage system will still require cleaning. Table 4.9 lists several options for inlet protection. All of the methods for storm drain inlet protection are prone to plugging and require a high frequency of maintenance. Drainage areas should be limited to 1 acre or less. Emergency overflows may be required where stormwater ponding would cause a hazard. If an emergency overflow is provided, additional end-of-pipe treatment may be required. Table 4.9 Storm Drain Inlet Protetion Applicable for Type of Inlet Emergency Paved/Earthen Protection Overflow Surfaces Conditions of Use Drop Inlet Protection Excavated drop inlet. Yes. Earthen Applicable for heavy flows. Easy protection temporary to maintain. Large area flooding will Requirement: 30'X 307acre occur Block and gravel drop Yes Paved or Earthen Applicable for heavy concentrated inlet protection flows. Will not pond. Gravel and wire drop No Applicable for heavy concentrated inlet protection flows. Will pond. Can withstand traffic. Catch basin filters Yes Paved or Earthen Frequent maintenance required. Curb Inlet Protection Curb inlet protection Small capacity Paved Used for sturdy, more compact with a wooden weir overflow installation_ Block and gravel curb Yes Paved Sturdy,but limited filtration. inlet protection Culvert Inlet Protection Culvert inlet sediment 18 month expected life- trap 4-82 Volume 11—Construction Stormwater Pollution Prevention February 2005 Design and Excavated Drop Inlet Protection - An excavated impoundment around the Installation storm drain. Sediment settles out of the stormwater prior to entering the Specifications storm drain. • Depth 1-2 ft as measured from the crest of the inlet structure. • Side Slopes of excavation no steeper than 2:1. • Minimum volume of excavation 35 cubic yards. • Shape basin to fit site with longest dimension oriented toward the longest inflow area. • Install provisions for draining to prevent standing water problems. • Clear the area of all debris. • Grade the approach to the inlet uniformly. • Drill weep holes into the side of the inlet. • Protect weep holes with screen wire and washed aggregate. • Seal weep holes when removing structure and stabilizing area. • It may be necessary to build a temporary dike to the down slope side of the structure to prevent bypass flow. Block and Gravel Filter- A barrier formed around the storm drain inlet with standard concrete blocks and gravel. See Figure 4.14. Height 1 to 2 feet above inlet. Recess the first row 2 inches into the ground for stability. • Support subsequent courses by placing a 2x4 through the block opening. • Do not use mortar. • Lay some blocks in the bottom row on their side for dewatering the pool. • Place hardware cloth or comparable wire mesh with '/z-inch openings over all block openings. Place gravel just below the top of blocks on slopes of 2:1 or flatter. • An alternative design is a gravel donut. • Inlet slope of 3:1. • Outlet slope of 2:1. • 1-foot wide level stone area between the structure and the inlct. • Inlet slope stones 3 inches in diameter or larger. • Outlet slope use gravel ''/z- to 3/<-inch at a minimum thickness of 1-foot. February 2005 Volume 11—Construction Stormwater Pollution Prevention 4-83 Plan View A Drain 'I,n) Grate 4 �nc a.U • to ?4P1 0 Concrete Block n. � ao'� 'c ..00 Gravel o,e°o a �C o Backfill 2, A Section A - A Concrete Block Wire Screen or Filter Fabric Gravel Backfill Overflow Water Ponding Height C> W.oeater i-E MFM_rd12_M 0 X Drop Inlet Notes- 1.Drop inlet sediment barriers are to be used for small,nearly level drainage areas-(less than 5%) 2.Excavate a basin of sufficient size adjacent to the drop inlet 3.The top of the structure(ponding height)must be well below the ground elevation downslope to prevent runot"I'from bypassing the inlet. A temporary dike may be necessary on the dowslope side of the structure. Figure 4.14—Block and Gravel Filter Gravel and Wire Mesh Filter-A gravel barrier placed over the top of the inlet. This structure does not provide an overflow. • Hardware cloth or comparable wire mesh with '/2-Inch openings. • Coarse aggregate. • Height 1-foot or more, 18 inches wider than inlet on all sides. • Place wire mesh over the drop inlet so that the wire extends a minimum of 1-foot beyond each side of the inlet structure. • If more than one strip of mesh is necessary, overlap the strips. • Place coarse aggregate over the wire mesh. • The depth of the gravel should be at least 12 inches over the entire inlet opening and extend at least 18 inches on all sides. 4-84 Volume Construction Stormwater Pollution Prevention February 2005 Cacchbasin Filters- Inserts should be designed by the manufacturer for use at construction sites. The limited sediment storage capacity increases the amount of inspection and maintenance required, which may be daily for heavy sediment loads. The maintenance requirements can be reduced by combining a catchbasin filter with another type of inlet protection. This type of inlet protection provides flow bypass without overflow and therefore may be a better method for inlets located along active rights-of- way. • 5 cubic feet of storage. • Dewatering provisions. • High-flow bypass that will not clog under normal use at a construction site. • The catchbasin filter is inserted in the catchbasin just below the grating. Curb Inlet Protection with Wooden Weir Barrier formed around a curb inlet with a wooden frame and gravel. • Wire mesh with '/2-inch openings. • Extra strength filter cloth. • Construct a frame. • Attach the wire and filter fabric to the frame. • Pile coarse washed aggregate against wire/fabric. • Place weight on frame anchors. Block and Gravel Curb Inlet Protection— Barrier formed around an inlet with concrete blocks and gravel. See Figure 4.14. • Wire mesh with '/z-inch openings. • Place two concrete blocks on their sides abutting the curb at either side of the inlet opening. These are spacer blocks_ • Place a 2x4 stud through the outer holes of each spacer block to align the front blocks. • Place blocks on their sides across the front of the inlet and abutting the spacer blocks. • Place wire mesh over the outside vertical face. • Pile coarse aggregate against the wire to the top of the barrier. Curb and Gutter Sediment Barrier— Sandbag or rock berm(riprap and aggregate) 3 feet high and 3 feet wide in a horseshoe shape. See Figure 4.16. • Construct a horseshoe shaped berm, faced with coarse aggregate if using riprap, 3 feet high and 3 feet wide, at least 2 feet from the inlet. • Construct a horseshoe shaped sedimentation trap on the outside of the berm sized to sediment trap standards for protecting a culvert inlet. February 2005 Volume 11-Construction Stormwater Pollution Prevention 4-85 Maintenance • Catch basin filters should be inspected frequently, especially after Standards storm events. If the insert becomes clogged, it should be cleaned or replaced. • For systems using stone filters: If the stone filter becomes clogged with sediment, the stones must be pulled away from the inlet and cleaned or replaced. Since cleaning of gravel at a construction site may be difficult, an alternative approach would be to use the clogged stone as fill and put fresh stone around the inlet. • Do not wash sediment into storm drains while cleaning. Spread all excavated material evenly over the surrounding land area or stockpile and stabilize as appropriate. 4-86 Volume It—Construction Stormwater Pollution Prevention February 2005 Plan View Back of Sidewalk A Catch Basin I i �I iI ,I n 2x4 Wood Stud Back of Curb "l Concrete Block Curb Inlet Q^ � .^ems. I I i � •..k.�°-�^ti�n � --��aocc800 °dro• •. °R !O' O0. °�•o p• "• ;`c��-.'"F`o�e�'�•c4�` p: a C :n a CG �G:.'.:.gip.` C.. �'✓'� e°p'OpaQ'oeq�' 44Qo°O�•Q 4-.Oo'Q gOo-Q: °�o"� 40✓- o°�•°•4�^``��,°,•O W° o'a, °' °•C �°o•°-pa ate- J o• o- CCc°.�•o•p•�cd c'c Wire Screen r Filter Fabric A —-' Concrete Block Section A - A '/' Drain Gravel (20mm) '/."Drain Gravel (20mm) Ponding Height _ Concrete Block ' Curb Inlet �X Wire Screen or \� Filter Fabric \ Catch Basin ' �•' 4 Wood Stud i N (100x50 Timber Stud) r\� "/ NOTES: 1-Use block and gravel type sediment barrier when curb inlet is located in gently sloping street segment, where water can pond and allow sediment to separate from runoff. 2. Barrier shall allow for overflow from severe storm event. 3-Inspect barriers and remove sediment after each storm event- Sediment and gravel must be removed from the traveled way immediately. Figure 4.15—Block and Gravel Curb Inlet Protection February 2005 Volume 11— Construction Stormwater Pollution Prevention 4-87 Plan View Back of Sidewalk Burlap Sacks to Catch Basin _ Overlap onto Curb Curb Inlet -- -`• __ __ Back of Curt,, I; RUNOFF `I. RUNOFF SPILLWAY.'/,% Gravel Filled Sandbags Stacked Tightly NOTES: 1.Place curb type sediment barriers on gently sloping street segments,where water can pond and alloy sediment to separate from runoff_ 2.Sandbags of either burlap or woven'geotextile'fabric,are filled with gravel,layered and packed tightly- 3.Leave a one sandbag gap in the top row to provide a spillway for overflow. 4_ Inspect barriers and remove sediment after each storm event_Sediment and gravel must be removed from the traveled way immediately. Figure 4.16—Curb and Gutter Barrier 4-88 Volume ll—Construction Stormwater Pollution Prevention February 2005 BMP C230: Straw Bale Barrier Pu,pose To decrease the velocity of sheet flows and intercept and detain small amounts of sediment from disturbed areas of limited extent, preventing sediment from leaving the site. See Figure 4.17 for details on straw bale barriers. Conditions of Use Below disturbed areas subject to sheet and rill erosion. • Straw bales are among the most used and least effective BMPs. The best use of a straw bale is hand spread on the site. • Where the size of the drainage area is no greater than 1/4 acre per 100 feet of barrier length; the maximum slope length behind the barrier is 100 feet; and the maximum slope gradient behind the barrier is 2:1. • Where effectiveness is required for less than three months. • Under no circumstances should straw bale barriers be constructed in streams, channels,or ditches. • Straw bale barriers should not be used where rock or hard surfaces prevent the full and uniform anchoring of the barrier. Design and Bales shall be placed in a single row, lengthwise on the contour, with ends Installation of adjacent bales tightly abutting one another. Specifications All bales shall be either wire-bound or string-tied. Straw bales shall be installed so that bindings are oriented around the sides rather than along the tops and bottoms of the bales in order to prevent deterioration of the bindings. • The barrier shall be entrenched and backfilled. A trench shall be excavated the width of a bale and the length of the proposed barrier to a minimum depth of 4 inches. The trench must be deep enough to remove all grass and other material that might allow underflow. After the bales are staked and chinked(filled by wedging), the excavated soil shall be backfilled against the barrier. Backfill soil shall conform to the ground level on the downhill side and shall be built up to 4 inches against the uphill side of the barrier. • Each bale shall be securely anchored by at least two stakes or re-bars driven through the bale. The first stake in each bale shall be driven toward the previously laid bale to force the bales together. Stakes or re-bars shall be driven deep enough into the ground to securely anchor the bales. Stakes should not extend above the bales but instead should be driven in flush with the top of the bale for safety reasons. • The gaps between the bales shall be chinked(filled by wedging) with straw to prevent water from escaping between the bales. Loose straw scattered over the area immediately uphill from a straw bale barrier tends to increase barrier efficiency. Wedging must be done carefully in order not to separate the bales. February 2005 Volume Il—Construction Stormwater Pollution Prevention 4-89 ,Maintenance Straw bale barriers shall be inspected immediately after each runoff- Standards producing rainfall and at least daily during prolonged rainfall. • Close attention shall be paid to the repair of damaged bales, end runs, and undercutting beneath bales. • Necessary repairs to barriers or replacement of bales shall be accomplished promptly. • Sediment deposits should be removed after each runoff-producing rainfall. They must be removed when the level of deposition reaches approximately one-half the height of the barrier. • Any sediment deposits remaining in place after the straw bale barrier is no longer required shall be dressed to conform to the existing grade, prepared and seeded. • Straw bales used as a temporary straw bale barrier shall be removed after project completion and stabilization to prevent sprouting of unwanted vegetation. 4-90 Volume /l—Construction Stormwater Pollution Prevention February 2005 Section A - A - 5'-6' ! If Ponding Height t\ Embed Straw Bale 4"(100mm)Minimum into Soil I�J j Angle Stake Toward Previous Bale to Section B - B Provide Tight Fit r_�_�,.—.___ _ —r _ �_�__,; _._.._,.__.�-•---- ____--vim--- IA �W.od,. ke or Rebar Driven Through Bale. Plan 3 B B NOTES: 1.The straw bales shall be placed on slope contour 2.Bales to be placed in a row with the ends tightly abutting 3.Key in bales to prevent erosion or flow under bales. Figure 4.17 Straw Bale Barrier February 2005 Volume ll-Construction Stormwater Pollution Prevention 4-91 BMP C231: Brush Barrier Purpose The purpose of brush barriers is to reduce the transport of coarse sediment from a construction site by providing a temporary physical barrier to sediment and reducing the runoff velocities of overland flow. Conditions of Use Brush barriers may be used downslope of all disturbed areas of less than one-quarter acre. • Brush barriers are not intended to treat concentrated flows. nor are they intended to treat substantial amounts of overland flow. Any concentrated flows must be conveyed through the drainage system to a sediment pond. The only circumstance in which overland flow can be treated solely by a barrier, rather than by a sediment pond, is when the area draining to the barrier is small. • Brush barriers should only be installed on contours. Design and • Height 2 feet(minimum) to 5 feet (maximum)_ Installation . Width 5 feet at base(minimum) to 15 feet (maximum)_ Specifications • Filter fabric(geotextile) may be anchored over the brush berm to enhance the filtration ability of the barrier. Ten-ounce burlap is an adequate alternative to filter fabric. • Chipped site vegetation,composted mulch, or wood-based mulch (hog fuel)can be used to construct brush barriers. • A 100 percent biodegradable installation can be constructed using 10- ounce burlap held in place by wooden stakes. Figure 4.18 depicts a typical brush barrier. Maintenance • There shall be no signs of erosion or concentrated runoff under or Standards around the barrier. If concentrated flows are bypassing the barrier, it must be expanded or augmented by toed-in filter fabric. • The dimensions of the barrier must be maintained. If required,drape filter fabric over brush and secure in 4N4" min.trench with compact backfill. Anchor downhill edge of / fitter fabric with stakes. sandbags.or equivalent. _r 2'Min.He'ght Min.5'wide brush barrier with max.6"diameter woody debris. Alternatively topsoil strippings may be used to form the barrier- Figure 4.18—Brush Barrier 4-92 Volume 11—Construction Stormwater Pollution Prevention February 2005 BMP C232: Gravel Filter Berm Purpose A gravel filter berm is constructed on rights-of-way or traffic areas within a construction site to retain sediment by using a filter berm of gravel or crushed rock. Conditions of Use Where a temporary measure is needed to retain sediment from rights-of- way or in traffic areas on construction sites. Design and • Berm material shall be 3/ to 3 inches in size,washed well-grade gravel Installation or crushed rock with less than 5 percent fines. Specifications • Spacing of berms: — Every 300 feet on slopes less than 5 percent — Every 200 feet on slopes between 5 percent and 10 percent — Every 100 feet on slopes greater than 10 percent --' • Berm dimensions: — I foot high with 3:1 side slopes — 8 linear feet per I cfs runoff based on the 10-year, 24-hour design storm Maintenance Regular inspection is required. Sediment shall be removed and filter Standards material replaced as needed. February 2005 Volume 11—Construction Stormwater Pollution Prevention 4-93 BMP C233: Silt Fence Purpose Use of a silt fence reduces the transport of coarse sediment from a construction site by providing a temporary physical barrier to sediment and reducing the runoff velocities of overland flow. See Figure 4.19 for details on silt fence construction. Conditions of Use Silt fence may be used downslope of all disturbed areas. • Silt fence is not intended to treat concentrated flows, nor is it intended to treat substantial amounts of overland flow. Any concentrated flows must be conveyed through the drainage system to a sediment pond. The only circumstance in which overland flow can be treated solely by a silt fence, rather than by a sediment pond, is when the area draining to the fence is one acre or less and flow rates are less than 0.5 cfs. • Silt fences should not be constructed in streams or used in V-shaped ditches. They are not an adequate method of silt control for anything deeper than sheet or overland flow. Joints in filter fabric shall be spliced at posts.Use staples,wire rings or equivalent to attach fabric to posts 2"x2"by 14 Ga.wire or equivalent,if standard strength fabric used — 1 ' I Filter fabric - I I i - ! illl I =1t i - -ll III _i-II� I_Llill '_! i 6 max I I ! Minimum 4"x4 trench It c I II � � Backfill trench with native soil �) Post spacing may be increased or TC-1.5"washed gravel to 8'if wire backing is used 2"x2"wood posts,steel fence posts,or equivalent Figure 4.19—Silt Fence Design and • Drainage area of 1 acre or less or in combination with sediment basin Installation in a larger site. Specifications • Maximum slope steepness(normal (perpendicular)to fence line) 1:1. • Maximum sheet or overland flow path length to the fence of 100 feet. • No flows greater than 0.5 cfs. • The geotextile used shall meet the following standards. All geotextile properties listed below are minimum average roll values(i.e., the test result for any sampled roll in a lot shall meet or exceed the values shown in Table 4.10): 4-94 Volume 11— Construction Stormwater Pollution Prevention February 2005 Table 4.10 Geotextile Standards Polymeric Mesh AOS 0.60 mm maximum for slit film wovens(#30 sieve). 0.30 (ASTM D4751) mm maximum for all other geotextile types(#50 sieve). 0.15 mm minimum for all fabric types(#100 sieve). Water Permittivity 0.02 sec minimum (ASTM D4491) Grab Tensile Strength 180 lbs.Minimum for extra strength fabric. (ASTM D4632) 100 Ibs minimum for standard strength fabric. Grab Tensile Strength 30%maximum (ASTM D4632) Ultraviolet Resistance 70%minimum (ASTM D4355) • Standard strength fabrics shall be supported with wire mesh, chicken wire, 2-inch x 2-inch wire, safety fence, or jute mesh to increase the strength of the fabric. Silt fence materials are available that have synthetic mesh backing attached. • Filter fabric material shall contain ultraviolet ray inhibitors and stabilizers to provide a minimum of six months of expected usable construction life at a temperature range of 0°F. to 120°F_ 100 percent biodegradable silt fence is available that is strong, long lasting, and can be left in place after the project is completed, if permitted by local regulations_ • Standard Notes for construction plans and specifications follow. Refer to Figure 4.19 for standard slit fence details. The contractor shall install and maintain temporary silt fences at the locations shown in the Plans. The silt fences shall be constructed in the areas of clearing, grading, or drainage prior to starting those activities. A silt fence shall not be considered temporary if the silt fence must function beyond the life of the contract_ The silt fence shall prevent soil carried by runoff water from going beneath, through, or over the top of the silt fence, but shall allow the water to pass through the fence. The minimum height of the top of silt fence shall be 2 feet and the maximum height shall be 2'h feet above the original ground surface. The geotextile shall be sewn together at the point of manufacture, or at an approved location as determined by the Engineer, to form geotextile lengths as required. All sewn seams shall be located at a support post. Alternatively, two sections of silt fence can be overlapped, provided the Contractor can demonstrate, to the satisfaction of the Engineer, that the overlap is long enough and that the adjacent fence sections are close enough together to prevent silt laden water from escaping through the fence at the overlap. February 2005 Volume 11—Construction Stormwater Pollution Prevention 4-95 The geotextile shall be attached on the up-slope side of the posts and support system with staples, wire, or in accordance with the -- manufacturer's recommendations. The geotextile shall be attached to the posts in a manner that reduces the potential for geotextile tearing at the staples, wire,or other connection device. Silt fence back-up support for the geotextile in the form of a wire or plastic mesh is dependent on the properties of the geotextile selected for use. If wire or plastic back-up mesh is used, the mesh shall be fastened securely to the up-slope of the posts with the geotextile being up-slope of the mesh back-up support. The geotextile at the bottom of the fence shall be buried in a trench to a minimum depth of 4 inches below the ground surface. The trench shall be backfilled and the soil tamped in place over the buried portion of the geotextile, such that no flow can pass beneath the fence and scouring can not occur. When wire or polymeric back-up support mesh is used, the wire or polymeric mesh shall extend into the trench a minimum of 3 inches. The fence posts shall be placed or driven a minimum of 18 inches_ A minimum depth of 12 inches is allowed if topsoil or other soft subgrade soil is not present and a minimum depth of 18 inches cannot be reached. Fence post depths shall be increased by 6 inches if the fence is located on slopes of 3:1 or steeper and the slope is perpendicular to the fence. If required post depths cannot be obtained, the posts shall be adequately secured by bracing or guying to prevent overturning of the fence due to sediment loading_ Silt fences shall be located on contour as much as possible, except at the ends of the fence, where the fence shall be turned uphill such that the silt fence captures the runoff water and prevents water from flowing around the end of the fence. If the fence must cross contours, with the exception of the ends of the fence, gravel check dams placed perpendicular to the back of the fence shall be used to minimize concentrated flow and erosion along the back of the fence. The gravel check dams shall be approximately I- foot deep at the back of the fence. It shall be continued perpendicular to the fence at the same elevation until the top of the check dam intercepts the ground surface behind the fence. The gravel check dams shall consist of crushed surfacing base course, gravel backfill for walls, or shoulder ballast_ The gravel check dams shall be located every 10 feet along the fence where the fence must cross contours_ The slope of the fence line where contours must be crossed shall not be steeper than 3:1. Wood, steel or equivalent posts shall be used. Wood posts shall have minimum dimensions of 2 inches by 2 inches by 3 feet minimum length, and shall be free of defects such as knots, splits, or gouges. 4-96 Volume 11—Construction Stormwater Pollution Prevention February 2005 Steel posts shall consist of either size No. 6 rebar or larger, ASTM A 120 steel pipe with a minimum diameter of 1-inch, U, T, L,or C shape steel posts with a minimum weight of 1.35 lbs./ft.or other steel posts having equivalent strength and bending resistance to the post sizes listed. The spacing of the support posts shall be a maximum of 6 feet. Fence back-up support, if used, shall consist of steel wire with a maximum mesh spacing of 2 inches, or a prefabricated polymeric mesh. The strength of the wire or polymeric mesh shall be equivalent to or greater than 180 lbs. grab tensile strength. The polymeric mesh must be as resistant to ultraviolet radiation as the geotextile it supports. • Silt fence installation using the slicing method specification details follow. Refer to Figure 4.20 for slicing method details. The base of both end posts must be at least 2 to 4 inches above the top of the silt fence fabric on the middle posts for ditch checks to drain properly. Use a hand level or string level, if necessary,to mark base points before installation. Install posts 3 to 4 feet apart in critical retention areas and 6 to 7 feet apart in standard applications. Install posts 24 inches deep on the downstream side of the silt fence, and as close as possible to the fabric,enabling posts to support the fabric from upstream water pressure. Install posts with the nipples facing away from the silt fence fabric. Attach the fabric to each post with three ties, all spaced within the top 8 inches of the fabric. Attach each tie diagonally 45 degrees through the fabric, with each puncture at least 1 inch vertically apart. In addition, each tie should be positioned to hang on a post nipple when tightening to prevent sagging. Wrap approximately 6 inches of fabric around the end posts and secure with 3 ties. No more than 24 inches of a 36-inch fabric is allowed above ground level. The rope lock system must be used in all ditch check applications. The installation should be checked and corrected for any deviation before compaction. Use a flat-bladed shovel to tuck fabric deeper into the ground if necessary. Compaction is vitally important for effective results. Compact the soil immediately next to the silt fence fabric with the front wheel of the tractor, skid steer, or roller exerting at least 60 pounds per square inch. Compact the upstream side first and then each side twice for a total of four trips. February 2005 Vo/ume 11—Construction Stormwater Pollution Prevention 4-97 • Any damage shall be repaired immediately. Maintenance If concentrated flows are evident uphill of the fence, they must be Standards intercepted and conveyed to a sediment pond. • It is important to check the uphill side of the fence for signs of the fence clogging and acting as a barrier to flow and then causing channelization of flows parallel to the fence. If this occurs, replace the fence or remove the trapped sediment. • Sediment deposits shall either be removed when the deposit reaches approximately one-third the height of the silt fence, or a second silt fence shall be installed. • If the filter fabric(geotextile) has deteriorated due to ultraviolet breakdown it shall be replaced. p.nding height POST SPACING: mac 24- 7'maw on op.n runs .. pooling ............ -- .............•Top of Fabric 4•max_on areas awca rat..tr w Beft upsbes,a slag oT past FLOW----- txfr.e.....ach rld.at POST DEPTH: Tr •tn fence 2 m a thaw As much tral ground .rtta a.vtce•wrtlr� u fabfie ae•w ground tW ps.l_er greater r �>al a[IaCMnera tm.c t to'R,cenysctlew dOL&A- i \ \ \r \\\\\\\\ \\ anACHME T DETMs: \ \/ j // / / th�� \ \\/\\// •Gaer fabdC at posts.f needed, \ / / / / //�//\\\//�/ /\��\�//\\//\\\ •Utirae tress ties p«post am wkNn top g-or rabdc. \\\\\\ \\\/ _ /\\/�/\\/� •Position each tie n-d—sr t-ed gy.P r nles vert ra a y•Hang each be on a pet nipple and tighten sec eery_ No more Umn 24'of a 3(r fabric use_hle gee(sons,[«soR w:a. is allowed above ground. Rog of sd fence �� Opprstion Past inta®ed after worn cbnn ^ Fabic Sit Fence 200-300mm i 9 Nonzoreal cMel point Siting[lade (76—�AdL4 (18 nwn vNdgt) Completed kviaiadon Vibratory plow is not acceptable because of hokornal compaction Figure 4.20-Silt Fence Installation by Slicing Method 4-98 Volume 11-Construction Stormwater Pollution Prevention February 2005 BMP C234: Vegetated Strip Purpose Vegetated strips reduce the transport of coarse sediment from a construction site by providing a temporary physical barrier to sediment and reducing the runoff velocities of overland flow. Conditions of Use 0 Vegetated strips may be used downslope of all disturbed areas. • Vegetated strips are not intended to treat concentrated flows, nor are they intended to treat substantial amounts of overland flow. Any concentrated flows must be conveyed through the drainage system to a sediment pond. The only circumstance in which overland flow can be treated solely by a strip, rather than by a sediment pond, is when the following criteria are met(see Table 4.11): Table 4.11 Vegetated Strips Average Sloe Slope Percent Flow path Length 1.5H:1 V or less 67%or less 100 feet 2H:1 V or less 50%or less 1 l 5 feet 4H:1 V or less 25%or less ISO feet 6H:1 V or less 16.7%or less 200 feet 1 OH:I V or less 10%or less 250 feet Design and The vegetated strip shall consist of a minimum of a 25-foot wide Installation continuous strip of dense vegetation with a permeable topsoil. Grass- Specifications covered, landscaped areas are generally not adequate because the volume of sediment overwhelms the grass. Ideally, vegetated strips shall consist of undisturbed native growth with a well-developed soil that allows for infiltration of runoff. • The slope within the strip shall not exceed 4H:I V. • The uphill boundary of the vegetated strip shall be delineated with clearing limits. Maintenance Any areas damaged by erosion or construction activity shall be seeded Standards immediately and protected by mulch. • If more than 5 feet of the original vegetated strip width has had vegetation removed or is being eroded, sod must be installed. • If there are indications that concentrated flows are traveling across the - buffer, surface water controls must be installed to reduce the flows entering the buffer,or additional perimeter protection must be installed. February 2005 Volume tl—Construction Stormwater Pollution Prevention 4-99 BMP C235: Straw Wattles Purpose Straw wattles are temporary erosion and sediment control barriers consisting of straw that is wrapped in biodegradable tubular plastic or similar encasing material. They reduce the velocity and can spread the flow of rill and sheet runoff, and can capture and retain sediment. Straw wattles are typically 8 to 10 inches in diameter and 25 to 30 feet in length. The wattles are placed in shallow trenches and staked along the contour of disturbed or newly constructed slopes. See Figure 4.21 for typical construction details. Conditions of U.ve • Disturbed areas that require immediate erosion protection. • Exposed soils during the period of short construction delays, or over winter months. • On slopes requiring stabilization until permanent vegetation can be established. • Straw wattles are effective for one to two seasons. • If conditions are appropriate, wattles can be staked to the ground using willow cuttings for added revegetation. • Rilling can occur beneath wattles if not properly entrenched and water can pass between wattles if not tightly abutted together. Design Criteria . It is critical that wattles are installed perpendicular to the flow direction and parallel to the slope contour. • Narrow trenches should be dug across the slope on contour to a depth of 3 to 5 inches on clay soils and soils with gradual slopes. On loose soils, steep slopes, and areas with high rainfall, the trenches should be dug to a depth of 5 to 7 inches, or 1/2 to 2/3 of the thickness of the wattle_ • Start building trenches and installing wattles from the base of the slope and work up. Excavated material should be spread evenly along the uphill slope and compacted using hand tamping or other methods. • Construct trenches at contour intervals of 3 to 30 feet apart depending - on the steepness of the slope, soil type, and rainfall. The steeper the slope the closer together the trenches. • Install the wattles snugly into the trenches and abut tightly end to end. Do not overlap the ends. • Install stakes at each end of the wattle, and at 4-foot centers along entire length of wattle. • If required, install pilot holes for the stakes using a straight bar to drive holes through the wattle and into the soil. • At a minimum, wooden stakes should be approximately 3/4 x 3/4 x 24 inches_ Willow cuttings or 3/8-inch rebar can also be used for stakes. 4-100 Volume 11—Construction Stormwater Pollution Prevention February 2005 Maintenance . Stakes should be driven through the middle of the wattle, leaving 2 to 3 Standards inches of the stake protruding above the wattle. • Wattles may require maintenance to ensure they are in contact with soil and thoroughly entrenched, especially after significant rainfall on steep sandy soils. • Inspect the slope after significant storms and repair any areas where wattles are not tightly abutted or water has scoured beneath the wattles. 3'-4' (1.2m) s <' \. \, Straw Rolls Must ` Be Placed Along ; �jl�j Lv l Slope Contours ;\ Adjacent rolls shall \ tightly abut /ZG '\ `o X' Spacing Depends \ on Soil Type and \ /<\//\�i; Sediment,organic matter, Slope Steepness \�\ and native seeds are captured behind the rolls. 3"-5"(75-125mm) 8%10"DIA. (200-250mm) Live Stake \� 1" X 1" Stake w not to scale (25 x 25mm) I l� NOTE l.Strain roll installation requires the placement and secure staking of the roll in a trench,Y-5"(75-125mm) deep.duL on contour. runoff must not be allowed to run under or around roll. Figure 4.21 —Straw Wattles February 2005 Volume 11—Construction Stormwater Pollution Prevention 4-101 BMP C240: Sediment Trap Purpose A sediment trap is a small temporary ponding area with a gravel outlet used to collect and store sediment from sites cleared and/or graded during construction. Sediment traps, along with other perimeter controls, shall be installed before any land disturbance takes place in the drainage area. Conditions of Use Prior to leaving a construction site, stormwater runoff must pass through a sediment pond or trap or other appropriate sediment removal best management practice. Non-engineered sediment traps may be used on-site prior to an engineered sediment trap or sediment pond to provide additional sediment removal capacity. It is intended for use on sites where the tributary drainage area is less than 3 acres, with no unusual drainage features, and a projected build-out time of six months or less. The sediment trap is a temporary measure(with a design life of approximately 6 months)and shall be maintained until the site area is permanently protected against erosion by vegetation and/or structures. Sediment traps and ponds are only effective in removing sediment down to about the medium silt size fraction. Runoff with sediment of finer grades(fine silt and clay)will pass through untreated, emphasizing the need to control erosion to the maximum extent first. Whenever possible, sediment-laden water shall be discharged into onsite, relatively level, vegetated areas(see BMP C234—Vegetated Strip). This is the only way to effectively remove fine particles from runoff unless chemical treatment or filtration is used. This can be particularly useful after initial treatment in a sediment trap or pond. The areas of release must be evaluated on a site-by-site basis in order to determine appropriate locations for and methods of releasing runoff. Vegetated wetlands shall not be used for this purpose. Frequently, it may be possible to pump water from the collection point at the downhill end of the site to an upslope vegetated area. Pumping shall only augment the treatment system, not replace it, because of the possibility of pump failure or runoff volume in excess of pump capacity. All projects that are constructing permanent facilities for runoff quantity control should use the rough-graded or final-graded permanent facilities for traps and ponds. This includes combined facilities and infiltration facilities. When permanent facilities are used as temporary sedimentation facilities, the surface area requirement of a sediment trap or pond must be met. If the surface area requirements are larger than the surface area of the permanent facility, then the trap or pond shall be enlarged to comply with the surface area requirement. The permanent pond shall also be divided into two cells as required for sediment ponds. 4-102 Volume It-Construction Stormwater Pollution Prevention February 2005 Either a permanent control structure or the temporary control structure (described in BMP C241, Temporary Sediment Pond)can be used. If a permanent control structure is used, it may be advisable to partially restrict the lower orifice with gravel to increase residence time while still allowing dewatering of the pond. A shut-off valve may be added to the control structure to allow complete retention of stormwater in emergency situations. In this case, an emergency overflow weir must be added. A skimmer may be used for the sediment trap outlet if approved by the Local Permitting Authority. Design and • See Figures 4.22 and 4.23 for details_ Installation Specifications • If permanent runoff control facilities are part of the project, they should be used for sediment retention. • To determine the sediment trap geometry, first calculate the design surface area(SA)of the trap, measured at the invert of the weir. Use the following equation: SA = FS(Q2/Vs) where Q2 = Design inflow based on the peak discharge from the developed 2-year runoff event from the contributing drainage area as computed in the hydrologic analysis. The 10-year peak flow shall be used if the project size, expected timing and duration of construction, or downstream conditions warrant a higher level of protection. If no hydrologic analysis is required, the Rational Method may be used. Vs = The settling velocity of the soil particle of interest_ The 0.02 mm (medium silt) particle with an assumed density of 2.65 g/cm3 has been selected as the particle of interest and has a settling velocity (Vs)of 0.00096 ft/sec. FS = A safety factor of 2 to account for non-ideal settling. Therefore, the equation for computing surface area becomes: SA = 2 x Q2/0.00096 or 2080 square feet per cfs of inflow Note: Evenif e f v permanent anent facilities are used,they must still have a surface area that is at least as large as that derived from the above formula. If they do not, the pond must be enlarged. • To aid in determining sediment depth, all sediment traps shall have a staff gauge with a prominent mark 1-foot above the bottom of the trap. February 2005 Volume 11—Construction Stormwater Pollution Prevention 4-103 • Sediment traps may not be feasible on utility projects due to the limited work space or the short-term nature of the work. Portable tanks may be used in place of sediment traps for utility projects. Maintenance a Sediment shall be removed from the trap when it reaches 1-foot in Standards depth. • Any damage to the pond embankments or slopes shall be repaired. Surface area determine 4'Min. at top of weir 1' Min. Overflow �y - - T - - - - - - - - 1'Min. 'L� 3.5'-5' 1 Min. �ln Flat Bottom 2'-4"Rock RipRap Washed gravel Note:Trap may be formed by berm or by Geotextile partial or complete excavation Discharge to stabilized conveyance, outlet,or level spreader Figure 4.22 Cross Section of Sediment Trap F� 6'Min. =I 11=I 11=I I I-1 I I-1 11=11 1'Min. depth overflow spillway —IIII=I 11=1 I I=I I I—I 11=I III— =I Native soil or �'_III : ,. : .: I I=_ Min. 1'deP th _ compacted backfill I 1 —I 11- 2"-4"'rock Geotextile -111=III=III=III=111=III=III III=11 I Min. 1'depth 3/4"-1.5" .III-1 I I-1 11-1 11 I I I 11 I I I 1=1 I I. I' washed gravel Figure 4.23 Sediment Trap Outlet 4-104 Volume 11—Construction Stormwater Pollution Prevention February 2005 BMP C241: Temporary Sediment Pond Purpose Sediment ponds remove sediment from runoff originating from disturbed areas of the site. Sediment ponds are typically designed to remove sediment no smaller than medium silt(0.02 mm)_ Consequently, they usually reduce turbidity only slightly. Conditions of[lve Prior to leaving a construction site, stormwater runoff must pass through a sediment pond or other appropriate sediment removal best management practice. A sediment pond shall be used where the contributing drainage area is 3 acres or more.. Ponds must be used in conjunction with erosion control practices to reduce the amount of sediment flowing into the basin. Design and Sediment basins must be installed only on sites where failure of the Installation structure would not result in loss of life, damage to homes or Specifications buildings, or interruption of use or service of public roads or utilities. Also, sediment traps and ponds are attractive to children and can be very dangerous. Compliance with local ordinances regarding health and safety must be addressed. If fencing of the pond is required, the - type of fence and its location shall be shown on the ESC plan. • Structures having a maximum storage capacity at the top of the dam of 10 acre-ft(435,600 ft)or more are subject to the Washington Dam Safety Regulations(Chapter 173-175 WAC). • See Figure 4.24, Figure 4.25, and Figure 4.26 for details. • If permanent runoff control facilities are part of the project, they should be used for sediment retention. The surface area requirements of the sediment basin must be met. This may require enlarging the permanent basin to comply with the surface area requirements. If a permanent control structure is used, it may be advisable to partially restrict the lower orifice with gravel to increase residence time while still allowing dewatering of the basin. • Use of infiltration facilities for sedimentation basins during construction tends to clog the soils and reduce their capacity to infiltrate. If infiltration facilities are to be used, the sides and bottom of the facility must only be rough excavated to a minimum of 2 feet above final grade. Final grading of the infiltration facility shall occur only when all contributing drainage areas are fully stabilized. The infiltration pretreatment facility should be fully constructed and used with the sedimentation basin to help prevent clogging. • Determining Pond Geometry Obtain the discharge from the hydrologic calculations of the peak flow for the 2-year runoff event (Q2). The 10-year peak flow shall be used if the project size, expected timing and duration of construction,or downstream conditions warrant a higher level of protection. If no hydrologic analysis is required, the Rational Method may be used. February 2005 Volume 11-Construction Stormwater Pollution Prevention 4-105 Detennine the required surface area at the top of the riser pipe with the equation: SA = 2 x Q210.00096 or 2080 square feet per cfs of inflow See BMP C240 for more information on the derivation of the surface area calculation. The basic geometry of the pond can now be determined using the following design criteria: • Required surface area SA (from Step 2 above)at top of riser. • Minimum 3.5-foot depth from top of riser to bottom of pond. • Maximum 3A interior side slopes and maximum 2:1 exterior slopes. The interior slopes can be increased to a maximum of 2:1 if fencing is provided at or above the maximum water surface. • One foot of freeboard between the top of the riser and the crest of the emergency spillway. • Flat bottom. • Minimum 1-foot deep spillway. • Length-to-width ratio between 3:1 and 6:1. • Sizing of Discharge Mechanisms. The outlet for the basin consists of a combination of principal and emergency spillways_ These outlets must pass the peak runoff expected from the contributing drainage area for a 100-year storm. If,due to site conditions and basin geometry,a separate emergency spill-way is not feasible, the principal spillway must pass the entire peak runoff expected from the 100-year storm. However,an attempt to provide a separate emergency spillway should always be made. The runoff calculations should be based on the site conditions during construction. The flow through the dewatering orifice cannot be utilized when calculating the 100-year storm elevation because of its potential to become clogged; therefore,available spillway storage must begin at the principal spillway riser crest. The principal spillway designed by the procedures contained in this standard will result in some reduction in the peak rate of runoff. However,the riser outlet design will not adequately control the basin discharge to the predevelopment discharge limitations as stated in Minimum Requirement#T Flow Control. However, if the basin for a permanent stormwater detention pond is used for a temporary sedimentation basin, the control structure for the permanent pond can be used to maintain predevelopment discharge limitations. The size of the basin,the expected life of the construction project, the anticipated downstream effects and the anticipated weather conditions during construction, should be considered to determine the need of additional discharge control. See Figure 4.28 for riser inflow curves. 4-106 Volume 11—Construction Stormwater Pollution Prevention February 2005 Key divider into slope to prevent tow arour�t a 4. Sediment ��C1iisser it The pond length shall be 3 to 6 �P�np times the maximum pond width '��~— \ Emergency overflow \'� AI r spillway Pond length `-.7.---.--- rser Inflow—.� Silt fence or Discharge to stabilized - equivalent e \\ � divider i conveyance,outlet,or ° level spreader Note:Pond may be formed by berm or`��by partial or complete excavation Figure 4.24-Sediment Pond Plan View Riser pipe (principal spillway) Crest of open at top with emergen Spillway 6'min_Width trash rack Embankment compacted 95% i-___-_ Dewatering device /IIIi� r ________ rvious materials such as I (see riser detail \ _, gravel or clean sand shall not be used --------------- ; -----=-------- --�yTr Hi E 1 Tii I -ij Discharge to stabilized Wire-backed silt fence DeWatering Concrete base staked haybales wrapped orifice conveyance outlet or with fitter fabric,or {see riser detail) level spreader equivalent divider Figure 4.25-Sediment Pond Cross Section Polyethylene cap Provide adequate strapping _f Perforated polyethylene = Corrugated drainage tubing,diameter _ metal riser min 2-larger than dewatering orifice. - 3.5-min_ Tubing shall comply - Watertight with ASTM F667 and Oewaterin orifice,schedule. - 9 AASHTO M294 coupling Tack weld 40 steel stub min. Diameter as per calculations •;nrr 6"min. r--- 18"min. T Alternatively,metal stakes Concrete base and wire may be used to prevent flotation �--2X riser dia.Mn.--� Figure 4.26-Sediment Pond Riser Detail February 2005 Volume 11-Construction Stormwater Pollution Prevention 4-107 too i 72 54 48 i 42 36 i 33 000, 000 ' 30 Ole I i 27 100, 0001 i 24 j t t1000I 21 .On 01- Ic a I j t 0 I o f 18 w 1 Q i P i t o 1 5 to 1 U 3 U Q 12 f j 10 f I t I 1 I i 0.1 f to HEAD IN FEET (measured from crest of riser) Ow,j,=9.739 DH312 O.,;e;«=3.782 D2H112 0 in cfs, D and H in feet Slope change occurs at weir-orifice transition Figure 4.27—Riser Inflow Curves 4-108 Volume 11—Construction Stormwater Pollution Prevention February 2005 Principal Spillway: Determine the required diameter for the principal spillway (riser pipe). The diameter shall be the minimum necessary to pass the pre-developed 10-year peak flow (Q10). Use Figure 4.28 to determine this diameter(h = 1-foot). Note:A permanent control structure may be used instead of a temporary riser. Emergency Overflow Spillway: Determine the required size and design of the emergency overflow spillway for the developed 100-year peak flow using the method contained in Volume III. Dewatering Orifice: Determine the size of the dewatering orifice(s) (minimum 1-inch diameter) using a modified version of the discharge equation fora vertical orifice and a basic equation for the area of a circular orifice. Determine the required area of the orifice with the following equation: AS(2h)o.s A° 0.60600Tgos where Ao = orifice area(square feet) As = pond surface area(square feet) h = head of water above orifice(height of riser in feet) T = dewatering time(24 hours) g = acceleration of gravity (32.2 feet/second2) Convert the required surface area to the required diameter D of the orifice: D = 24x r-IrL = 13.54x A° The vertical,perforated tubing connected to the dewatering orifice must be at least 2 inches larger in diameter than the orifice to improve flow characteristics. The size and number of perforations in the tubing should be large enough so that the tubing does not restrict flow. The orifice should control the flow rate. • Additional Design Specifications The pond shall be divided into two roughly equal volume cells by a - permeable divider that will reduce turbulence while allowing movement of water between cells. The divider shall be at least one- half the height of the riser and a minimum of one foot below the top of the riser. Wire-backed, 2-to 3-foot high, extra strength filter fabric supported by treated 4"x4"s can be used as a divider. Alternatively, staked straw bales wrapped with filter fabric (geotextile)may be used. If the pond is more than 6 feet deep, a different mechanism must be proposed. A riprap embankment is one acceptable method of separation for deeper ponds. Other designs that satisfy the intent of February 2005 Volume 11— Construction Stormwater Pollution Prevention 4-109 this provision are allowed as long as the divider is permeable, structurally sound, and designed to prevent erosion under or around the barrier. To aid in determining sediment depth, one-foot intervals shall be prominently marked on the riser. If an embankment of more than 6 feet is proposed, the pond must comply with the criteria contained in Volume III regarding dam safety for detention BMPs. • The most common structural failure of sedimentation basins is caused by piping.. Piping refers to two phenomena: (1) water seeping through fine-grained soil, eroding the soil grain by grain and forming pipes or tunnels; and,(2)water under pressure flowing upward through a granular soil with a head of sufficient magnitude to cause soil grains to lose contact and capability for support. The most critical construction sequences to prevent piping will be: l. Tight connections between riser and barrel and other pipe connections. 2. Adequate anchoring of riser. 3. Proper soil compaction of the embankment and riser footing. 4. Proper construction of anti-seep devices_ Maintenance • Sediment shall be removed from the pond when it reaches I-foot in Standards depth. • Any damage to the pond embankments or slopes shall be repaired. 4-110 Volume 11—Construction Stormwater Pollution Prevention February 2005 BMP C250: Construction Stormwater Chemical Treatment Purpose This BMP applies when using stormwater chemicals in batch treatment or flow-through treatment_ Turbidity is difficult to control once fine particles are suspended in stormwater runoff from a construction site. Sedimentation ponds are effective at removing larger particulate matter by gravity settling, but are ineffective at removing smaller particulates such as clay and fine silt. Traditional erosion and sediment control BMPs may not be adequate to ensure compliance with the water quality standards for turbidity in receiving water. Chemical treatment can reliably provide exceptional reductions of turbidity and associated pollutants. Chemical treatment may be required to meet turbidity stormwater discharge requirements, especially when construction is to proceed through the wet season. Conditions of Use Formal written approval from Ecology is required for the use of chemical treatment regardless of site size. The Local Permitting Authority may also require review and approval. When approved, the chemical treatment system must be included in the Stormwater Pollution Prevention Plan (SWPPP). Design and See Appendix II-B for background information on chemical treatment. Installation Specifications Criteria for Chemical Treatment Product Use: Chemically treated stormwater discharged from construction sites must be nontoxic to aquatic organisms. The Chemical Technology Assessment Protocol(CTAPE) must be used to evaluate chemicals proposed for stormwater treatment. Only chemicals approved by Ecology under the CTAPE may be used for stormwater treatment_ The approved chemicals, their allowable application techniques(batch treatment or flow-through treatment), allowable application rates, and conditions of use can be found at the Department of Ecology Emerging Technologies website: http://www.ecy.wa.gov.programs/wq/stormwater/newtech/index.html Treatment System Design Considerations: The design and operation of a chemical treatment system should take into consideration the factors that determine optimum, cost-effective performance. It is important to recognize the following: • Only Ecology approved chemicals may be used and must follow approved dose rates. • The pH of the stormwater must be in the proper range for the polymers to be effective, which is typically 6.5 to 8.5. • The coagulant must be mixed rapidly into the water to ensure proper dispersion. February 2005 Volume 11— Construction Stormwater Pollution Prevention 1 • A flocculation step is important to increase the rate of settling, to produce the lowest turbidity, and to keep the dosage rate as low as possible. • Too little energy input into the water during the flocculation phase results in flocs that are too small and/or insufficiently dense. Too much energy can rapidly destroy floc as it is formed. • Care must be taken in the design of the withdrawal system to minimize outflow velocities and to prevent floc discharge. Discharge from a batch treatment system should be directed through a physical filter such as a vegetated swale that would catch any unintended floc discharge.' Currently, flow-through systems always discharge through the chemically enhanced sand filtration system. • System discharge rates must take into account downstream conveyance integrity. Polymer Batch 'Treatment Process Description.- A batch chemical treatment system consists of the stormwater collection system (either temporary diversion or the permanent site drainage system), an untreated stormwater storage pond,pumps, a chemical feed system, treatment cells, and interconnecting piping. The batch treatment system shall use a minimum of two lined treatment cells in addition to the untreated stormwater storage pond_ Multiple treatment cells allow for clarification of treated water while other cells are being filled or emptied. Treatment cells may be ponds or tanks. Ponds with constructed earthen embankments greater than six feet high require special engineering analyses. Stormwater is collected at interception point(s)on the site and is diverted by gravity or by pumping to an untreated stormwater storage pond or other untreated stormwater holding area. The stormwater is stored until treatment occurs. It is important that the holding pond be large enough to provide adequate storage. The first step in the treatment sequence is to check the pH of the stormwater in the untreated stormwater storage pond. The pH is adjusted _ by the application of carbon dioxide or a base until the stormwater in the storage pond is within the desired pH range,6.5 to 8.5. When used, carbon dioxide is added immediately downstream of the transfer pump. Typically sodium bicarbonate(baking soda) is used as a base, although other bases may be used. When needed, base is added directly to the untreated stormwater storage pond. The stormwater is recirculated with the treatment pump to provide mixing in the storage pond. Initial'pH February 2005 Volume 11— Construction Stormwater Pollution Prevention 2 adjustments should be based on daily bench tests. Further pH adjustments can be made at any point in the process. Once the stormwater is within the desired pH range(dependant on polymer being used), the stormwater is pumped from the untreated stormwater storage pond to a treatment cell as polymer is added_ The polymer is added upstream of the pump to facilitate rapid mixing. After polymer addition, the water is kept in a lined treatment cell for clarification of the sediment-floc. In a batch mode process, clarification typically takes from 30 minutes to several hours. Prior to discharge samples are withdrawn for analysis of pH and turbidity. If both are acceptable, the treated water is discharged. Several configurations have been developed to withdraw treated water from the treatment cell. The original configuration is a device that withdraws the treated water from just beneath the water surface using a float with adjustable struts that prevent the float from settling on the cell bottom. This reduces the possibility of picking up sediment-floc from the bottom of the pond. The struts are usually set at a minimum clearance of about 12 inches; that is, the float will come within 12 inches of the bottom of the cell. Other systems have used vertical guides or cables which constrain the float, allowing it to drift up and down with the water level. More recent designs have an H-shaped array of pipes, set on the horizontal This scheme provides for withdrawal from four points rather than one. This configuration reduces the likelihood of sucking settled solids from the bottom. It also reduces the tendency for a vortex to form. Inlet diffusers, a long floating or fixed pipe with many small holes in it, are also an option. Safety is a primary concern. Design should consider the hazards associated with operations, such as sampling. Facilities should be designed to reduce slip hazards and drowning. Tanks and ponds should have life rings, ladders, or steps extending from the bottom to the top. Polymer Flow-Through Treatment Process Description: At a minimum, a flow-through chemical treatment system consists of the stormwater collection system (either temporary diversion or the permanent site drainage system), an untreated stormwater storage pond, and the chemically enhanced sand filtration system. Stormwater is collected at interception point(s)on the site and is diverted by gravity or by pumping to an untreated stormwater storage pond or other untreated stormwater holding area. The stormwater is stored until February 2005 Volume 11—Construction Stormwater Pollution Prevention 3 treatment occurs. It is important that the holding pond be large enough to provide adequate storage. Stormwater is then pumped from the untreated stormwater storage pond to the chemically enhanced sand filtration system where polymer is added. - Adjustments to pH may be necessary before chemical addition. The sand filtration system continually monitors the stormwater for turbidity and pH. If the discharge water is ever out of an acceptable range for turbidity or pH, the water is recycled to the untreated stormwater pond where it can be retreated. For batch treatment and flow-through treatment, the following equipment should be located in a lockable shed: • the chemical injector; • secondary non-corrosive containment for acid, caustic, buffering compound, and treatment chemical; • emergency shower and eyewash, and • monitoring equipment. System Sizing Certain sites are required to implement flow control for the developed sites. These sites must also control stormwater release rates during construction. Generally, these are sites that discharge stormwater directly, or indirectly, through a conveyance system, into a fresh water. System sizing is dependent on flow control requirements. Sizing Criteria for Batch Treatment Systems for Flow Control Exempt Water Bodies: The total volume of the untreated stormwater storage pond and treatment - ponds or tanks must be large enough to treat the volume of stormwater that is produced during multiple day storm events. It is recommended that at a minimum the untreated stormwater storage pond be sized to hold 1.5 times the runoff volume of the 10-year, 24-hour storm event. Bypass should be provided around the chemical treatment system to accommodate extreme storm events. Runoff volume shall be calculated using the methods presented in Volume 3, Chapter 2. Worst-case land cover conditions(i.e.,producing the most runoff) should be used for analyses(in most cases, this would be the land cover conditions just prior to final landscaping). Primary settling should be encouraged in the untreated stormwater storage pond. A forebay with access for maintenance may be beneficial. February 2005 Volume /1—Construction Stormwater Pollution Prevention 4 There are two opposing considerations in sizing the treatment cells. A larger cell is able to treat a larger volume of water each time a batch is processed. However, the larger the cell the longer the time required to empty the cell. A larger cell may also be less effective at flocculation and therefore require a longer settling time. The simplest approach to sizing the treatment cell is to multiply the allowable discharge flow rate times the desired drawdown time. A 4-hour drawdown time allows one batch per cell per 8-hour work period, given 1 hour of flocculation followed by two hours of settling. If the discharge is directly to a lake, flow control exempt receiving water listed in Appendix E of Volume I,or to an infiltration system, there is no discharge flow limit. Ponds sized for flow control water bodies must at a minimum meet the sizing criteria for flow control exempt waters. Sizing Criteria for Flow-Through Treatment Systems for Flow Control Exempt Water Bodies: When sizing storage ponds or tanks for flow-through systems for flow control exempt water bodies,the treatment system capacity should be a factor. The untreated stormwater storage pond or tank should be sized to hold 1.5 times the runoff volume of the 10-year, 24-hour storm event minus the treatment system flowrate for an 8-hour period. For a chitosan- enhanced sand filtration system, the treatment system flowrate should be sized using a hydraulic loading rate between 6-8 gpm/ft2. Other hydraulic loading rates may be more appropriate for other systems. Bypass should be provided around the chemical treatment system to accommodate extreme storms. Runoff volume shall be calculated using the methods presented in Volume 3,Chapter 2. Worst-case land cover conditions (i.e., producing the most runoff) should be used for analyses(in most cases, this would be the land cover conditions just prior to final landscaping). Sizing Criteria for Flow Control Water Bodies: Sites that must implement flow control for the developed site condition must also control stormwater release rates during construction. Construction site stormwater discharges shall not exceed the discharge durations of the pre-developed condition for the range of pre-developed discharge rates from '/z of the 2-year flow through the 10-year flow as predicted by an approved continuous runoff model. The pre-developed condition to be matched shall be the land cover condition immediately prior to the development project. This restriction on release rates can affect the size of the storage pond and treatment cells. The following is how WWHM can be used to determine the release rates from the chemical treatment systems: February 2005 Volume 11—Construction Stormwater Pollution Prevention 5 1. Determine the pre-developed flow durations to be matched by entering the land use area under the"Pre-developed"scenario in WWHM_ The default flow range is from '/2 of the 2-year flow through the 10-year flow. 2. Enter the post developed land use area in the"Developed Unmitigated" scenario in WWHM. 3. Copy the land use information from the"Developed Unmitigated" to"Developed Mitigated—scenario. 4. While in the"Developed Mitigated" scenario, add a pond element under the basin element containing the post-developed land use areas. This pond element represents information on the available untreated stormwater storage and discharge from the chemical treatment system. In cases where the discharge from the chemical treatment system is controlled by a pump, a stage/storage/discharge(SSD) table representing the pond must be generated outside WWHM and imported into WWHM. WWHM - can route the runoff from the post-developed condition through this SSD table(the pond) and determine compliance with the flow duration standard. This would be an iterative design procedure where if the initial SSD table proved to be inadequate, the designer would have to modify the SSD table outside WWHM and re- import in WWHM and route the runoff through it again. The iteration will continue until a pond that complies with the flow duration standard is correctly sized. Notes on SSD table characteristics: • The pump discharge rate would likely be initially set at just below '/z of the 2-year flow from the pre-developed condition. As runoff coming into the untreated stormwater storage pond increases and the available untreated stormwater storage volume gets used up, it would be necessary to increase the pump discharge rate above '/z of the 2-year. The increase(s) above '/2 of the 2-year must be such that they provide some relief to the untreated stormwater storage needs but at the same time will not cause violations of the flow duration standard at the higher flows. The final design SSD table will identify the appropriate pumping rates and the corresponding stage and storages. • When building such a flow control system, the design must ensure that any automatic adjustments to the pumping rates will be as a result of changes to the available storage in accordance with the final design SSD table. 5. It should be noted that the above procedures would be used to meet the flow control requirements. The chemical treatment system February 2005 Volume 11—Construction Stormwater Pollution Prevention 6 must be able to meet the runoff treatment requirements. It is likely that the discharge flow rate of% of the 2-year or more may exceed the treatment capacity of the system. If that is the case, the untreated stormwater discharge rate(s)(i.e., influent to the treatment system) must be reduced to allow proper treatment. Any reduction in the flows would likely result in the need for a larger untreated stormwater storage volume. • If the discharge is to a municipal storm drainage system, the allowable discharge rate may be limited by the capacity of the public system. It may be necessary to clean the municipal storm drainage system prior to the start.of the discharge to prevent scouring solids from the drainage system. if the municipal storm drainage system discharges to a water body not on the flow control exempt list, the project site is subject to flow control requirements. If system design does not allow you to discharge at the slower rates as described above and if the site has a retention or detention pond that will serve the planned development,the discharge from the treatment system may be directed to the permanent retention/detention pond to comply with the flow control requirement. In this case, the untreated stormwater storage pond and treatment system will be sized according to the sizing criteria for flow-through treatment systems for flow control exempt water bodies described earlier except all discharge (water passing through the treatment system and stormwater bypassing the treatment system)will be directed into the permanent retention/detention pond_ If site constraints make locating the untreated stormwater storage pond difficult, the permanent retention/detention pond may be divided to serve as the untreated stormwater storage pond and the post-treatment flow control pond. A berm or barrier must be used in this case so the untreated water does not mix with the treated water. Both untreated stormwater storage requirements, and adequate post-treatment flow control must be achieved. The post-treatment flow control pond's revised dimensions must be entered into the WWHM and the WWHM must be run to confirm compliance with the flow control requirement. Maintenance Monitoring: At a minimum, the following monitoring shall be Standards conducted. Test results shall be recorded on a daily log kept on site. Additional testing may be required by the NPDES permit based on site conditions Operational Monitoring • Total volume treated and discharged • Flow must be continuously monitored and recorded at not greater than 15-minute intervals February 2005 Volume I!- Construction Stormwater Pollution Prevention 7 • Type and amount of chemical used for pH adjustment, if any • Quantity of chemical used for treatment • Settling time Compliance Monitoring • Influent and effluent pH and turbidity must be continuously monitored and recorded at not greater than 15-minute intervals. • pH and turbidity of the receiving water Biomomtonng Treated stormwater must be non-toxic to aquatic organisms. Treated stormwater must be tested for aquatic toxicity or residual chemical content. Frequency of biomouitoring will be determined by Ecology. Residual chemical tests must be approved by Ecology prior to their use. If testing treated stormwater for aquatic toxicity, you must test for acute (lethal)toxicity. Bioassays shall be conducted by a laboratory accredited by Ecology, unless otherwise approved by Ecology. Acute toxicity tests shall be conducted per the CTAPE protocol. Discharge Compliance: Prior to discharge, treated stormwater must be sampled and tested for compliance with pH and turbidity limits. These limits may be established by the Construction Stonuwater General Permit or a site-specific discharge permit. Sampling and testing for other pollutants may also be necessary at some sites. pH must be within the range of 6.5 to 8.5 standard units and not cause a change in the pH of the receiving water of more than 0.2 standard units. Treated stormwater samples and measurements shall be taken from the discharge pipe or another location representative of the nature of the treated stormwater discharge. Samples used for determining compliance with the water quality standards in the receiving water shall not be taken from the treatment pond prior to decanting. Compliance with the water quality standards is determined in the receiving water_ Operator Training: Each contractor who intends to use chemical treatment shall be trained by an experienced contractor on an active site. Standard BMPs: Surface stabilization BMPs should be implemented on site to prevent significant erosion. All sites shall use a truck wheel wash to prevent tracking of sediment off site. February 2005 Volume 11— Construction Stormwater Pollution Prevention 8 Sediment Removal and Disposal: • Sediment shall be removed from the storage or treatment cells as necessary. Typically, sediment removal is required at least once during a wet season and at the decommissioning of the cells. Sediment remaining in the cells between batches may enhance the settling process and reduce the required chemical dosage. • Sediment that is known to be non-toxic may be incorporated into the site away from drainages. February 2005 Volume 11— Construction Stormwater Pollution Prevention 9 BMP C251: Construction Stormwater Filtration Purpose Filtration removes sediment from runoff originating from disturbed areas of the site. Conditions of Use Traditional BMPs used to control soil erosion and sediment loss from sites under development may not be adequate to ensure compliance with the water quality standard for turbidity in the receiving water. Filtration may be used in conjunction with gravity settling to remove sediment as small as fine silt(0.5 µm). The reduction in turbidity will be dependent on the particle size distribution of the sediment in the stormwater. In some circumstances, sedimentation and filtration may achieve compliance with the water quality standard for turbidity. The use of construction stormwater filtration does not require approval from Ecology as long as treatment chemicals are not used. Filtration in conjunction with polymer treatment requires testing under the Chemical Technology Assessment Protocol—Ecology(CTAPE)before it can be initiated. Approval from the appropriate regional Ecology office must be obtained at each site where polymers use is proposed prior to use. For more guidance on stormwater chemical treatment see BMP C250. Background Information Filtration with sand media has been used for over a century to treat water and wastewater. The use of sand filtration for treatment of stormwater has developed recently, generally to treat runoff from streets,parking lots, and residential areas. The application of filtration to construction Stormwater is currently under development. Design and Installation Specifications Two types of filtration systems may be applied to construction stormwater treatment: rapid and slow. Rapid sand filters are the typical system used for water and wastewater treatment. They can achieve relatively high hydraulic flow rates, on the order of 2 to 20 gpm/sf, because they have automatic backwash systems to remove accumulated solids. In contrast, slow sand filters have very low hydraulic rates, on the order of 0.02 gpm/sf, because they do not have backwash systems. To date, slow sand filtration has generally been used to treat stormwater. Slow sand filtration is mechanically simple in comparison to rapid sand filtration but requires a much larger filter area. Filtration Equipment. Sand media filters are available with automatic backwashing features that can filter to 50 µm particle size. Screen or bag filters can filter down to 5 µm. Fiber wound filters can remove particles down to 0.5 µm. Filters should be sequenced from the largest to the smallest pore opening_ Sediment removal efficiency will be related to particle size distribution in the stormwater. February 2005 Volume 11—Construction Stormwater Pollution Prevention 10 Treatment Process Description. Stormwater is collected at interception point(s)on the site and is diverted to an untreated stormwater sediment pond or tank for removal of large sediment and storage of the stormwater before it is treated by the filtration system. The untreated stormwater is pumped from the trap, pond,or tank through the filtration system in a rapid sand filtration system. Slow sand filtration systems are designed as flow through systems using gravity. Maintenance Rapid sand filters typically have automatic backwash systems that are Standards triggered by a pre-set pressure drop across the filter. If the backwash water volume is not large or substantially more turbid than the untreated stormwater stored in the holding pond or tank, backwash return to the untreated stormwater pond or tank may be appropriate. However, other means of treatment and disposal may be necessary. • Screen,bag, and fiber filters must be cleaned and/or replaced when they become clogged. • Sediment shall be removed from the storage and/or treatment ponds as necessary. Typically, sediment removal is required once or twice during a wet season and at the decommissioning of the ponds. Sizing Criteria for Flow-Through Treatment Systems for Flow Control Exempt Water Bodies: When sizing storage ponds or tanks for flow-through systems for flow control exempt water bodies the treatment system capacity should be a factor. The untreated stormwater storage pond or tank should be sized to hold 1.5 times the runoff volume of the 10-year, 24-hour storm event minus the treatment system flowrate for an 8-hour period. For a chitosan- enhanced sand filtration system, the treatment system flowrate should be sized using a hydraulic loading rate between 6-8 gpm/ftz. Other hydraulic loading rates may be more appropriate for other systems. Bypass should be provided around the chemical treatment system to accommodate extreme storms. Runoff volume shall be calculated using the methods presented in Volume 3,Chapter 2. Worst-case conditions(i.e., producing the most runoff)should be used for analyses(most likely conditions present prior to final landscaping). Sizing Criteria for Flow Control Water Bodies: Sites that must implement flow control for the developed site condition must also control stormwater release rates during construction. Construction site stormwater discharges shall not exceed the discharge durations of the pre-developed condition for the range of pre-developed discharge rates from 1/2 of the 2-year flow through the 10-year flow as February 2005 Volume 11— Construction Stormwater Pollution Prevention 11 predicted by an approved continuous runoff model. The pre-developed condition to be matched shall be the land cover condition immediately prior to the development project. This restriction on release rates can affect the size of the storage pond, the filtration system, and the flow rate through the filter system. The following is how WWHM can be used to determine the release rates from the filtration systems: 1. Determine the pre-developed flow durations to be matched by entering the land use area under the"Pre-developed"scenario in WWH.M. The default flow range is from ''/z of the 2-year flow through the 10-year flow. 2. Enter the post developed land use area in the"Developed Unmitigated" scenario in WWHM. 3. Copy the land use information from the"Developed Unmitigated" to"Developed Mitigated" scenario. 4. There are two possible ways to model stormwater filtration systems: 4a. The stormwater filtration system uses an untreated stormwater storage pond/tank and the discharge from this pond/tank is pumped to one or more filters. In-line filtration chemicals would be added to the flow right after the pond/tank and before the filter(s). Because the discharge is pumped, WWHM can't generate a stage/storage/discharge(SSD) table for this system. This system is modeled the same way as described in BMP C250 and is as follows: While in the"Developed Mitigated"scenario, add a pond element under the basin element containing the post-developed land use areas. This pond element represents information on the available untreated stormwater storage and discharge from the filtration system. In cases where the discharge from the filtration system is controlled by a pump, a stage/storage/discharge(SSD)table representing the pond must be generated outside WWHM and imported into WWHM. WWHM can route the runoff from the post-developed condition through this SSD table(the pond) and determine compliance with the flow duration standard. This would be an iterative design procedure where if the initial SSD table proved to be out of compliance, the designer would have to modify the SSD table outside WWHM and re-import in WWHM and route the runoff through it again. The iteration will continue until a pond that enables compliance with the flow duration standard is designed. Notes on SSD table characteristics: February 2005 Volume II—Construction Stormwater Pollution Prevention 12 • The pump discharge rate would likely be initially set at just below '/2 if the 2-year flow from the pre-developed condition. As runoff coming into the untreated stormwater storage pond increases and the available untreated stormwater storage volume gets used up, it would be necessary to increase the pump discharge rate above '/2 of the 2-year. The increase(s) above '/2 of the 2-year must be such that they provide some relief to the untreated stormwater storage needs but at the same time they will not cause violations of the flow duration standard at the higher flows. The final design SSD table will identify the appropriate pumping rates and the corresponding stage and storages. • When building such a flow control system, the design must ensure that any automatic adjustments to the pumping rates will be as a result of changes to the available storage in accordance with the final design SSD table. 4b. The stormwater filtration system uses a storage pond/tank and the discharge from this pond/tank gravity flows to the filter. This is usually a slow sand filter system and it is possible to model it in WWHM as a Filter element or as a combination of Pond and Filter element placed in series. The stage/storage/discharge table(s) may then be generated within WWHM as follows: (1) While in the"Developed Mitigated"scenario, add a Filter element under the basin element containing the post- developed land use areas. The length and width of this filter element would have to be the same as the bottom length and width of the upstream untreated stormwater storage pond/tank. (ii) In cases where the length and width of the filter is not the same as those for the bottom of the upstream untreated stormwater storage tank/pond,the treatment system may be modeled as a Pond element followed by a Filter element. - By having these two elements, WWHM would then generate a SSD table for the storage pond which then gravity flows to the Filter element. The Filter element downstream of the untreated stormwater storage pond would have a storage component through the media, and an overflow component for when the filtration capacity is exceeded. WWHM can route the runoff from the post-developed condition through the treatment systems in 4b and determine compliance with the flow duration standard. This would be an iterative design procedure where if the initial sizing estimates for the treatment system proved to be inadequate, the designer would have to February 2005 Volume 11- Construction Stormwater Pollution Prevention 13 modify the system and route the runoff through it again. The iteration would continue until compliance with the flow duration standard is achieved. 5. It should be noted that the above procedures would be used to meet the flow control requirements. The filtration system must be able to meet the runoff treatment requirements_ It is likely that the discharge flow rate of%Z of the 2-year or more may exceed the treatment capacity of the system. If that is the case, the untreated stormwater discharge rate(s)(i.e., influent to the treatment system) must be reduced to allow proper treatment_ Any reduction in the flows would likely result in the need for a larger untreated stormwater storage volume. If system design does not allow you to discharge at the slower rates as described above and if the site has a retention or detention pond that will serve the planned development, the discharge from the treatment system may be directed to the permanent retention/detention pond to comply with the flow control requirements. In this case, the untreated stormwater storage pond and treatment system will be sized according to the sizing criteria for flow-through treatment systems for flow control exempt waterbodies described earlier except all discharges(water passing through the treatment system and stormwater bypassing the treatment system) will be directed into the permanent retention/detention pond. If site constraints make locating the untreated stormwater storage pond difficult,the permanent retention/detention pond may be divided to serve as the untreated stormwater discharge pond and the post-treatment flow control pond. A berm or barrier must be used in this case so the untreated water does not mix with the treated water. Both untreated stormwater storage requirements, and adequate post-treatment flow control must be achieved. The post-treatment flow control pond's revised dimensions must be entered into the WWHM and the WWHM must be run to confirm compliance with the flow control requirement. February 2005 Volume 11— Construction Stormwater Pollution Prevention 14 Appendix II-B Background Information on Chemical Treatment Coagulation and flocculation have been used for over a century to treat water. It is used less frequently for the treatment of wastewater. The use of coagulation and flocculation for treating stormwater is a very recent application. Experience with the treatment of water and wastewater has resulted in a basic understanding of the process, in particular factors that affect performance. This experience can provide insights as to how to most effectively design and operate similar systems in the treatment of stormwater. Fine particles suspended in water give it a milky appearance, measured as turbidity. Their small size,often much less than I µm in diameter, give them a very large surface area relative to their volume. These fine particles typically carry a negative surface charge. Largely because of these two factors,small size and negative charge, these particles tend to stay in suspension for extended periods of time. Thus, removal is not practical by gravity settling. These are called stable suspensions. Polymers, as well as inorganic chemicals such as alum, speed the process of clarification. The added chemical destabilizes the suspension and causes the smaller particles to agglomerate. The process consists of three steps: coagulation, flocculation, and settling or clarification. Each step is explained below as well as the factors that affect the efficiency of the process. Coagulation: Coagulation is the first step. It is the process by which negative charges on the fine particles that prevent their agglomeration are disrupted_ Chemical addition is one method of destabilizing the suspension, and polymers are one class of chemicals that are generally effective. Chemicals that are used for this purpose are called coagulants. Coagulation is complete when the suspension is destabilized by the neutralization of the negative charges. Coagulants perform best when they are thoroughly and evenly dispersed under relatively intense mixing. This rapid mixing involves adding the coagulant in a manner that promotes rapid dispersion, followed by a short time period for destabilization of the particle suspension. The particles are still very small and are not readily separated by clarification until flocculation occurs. Flocculation: Flocculation is the process by which fine particles that have been destabilized bind together to form larger particles that settle rapidly. Flocculation begins naturally following coagulation, but is enhanced by gentle mixing of the destabilized suspension. Gentle mixing helps to bring particles in contact with one another such that they bind and continually grow to form "flocs." As the size of the flocs increases they become heavier and tend to settle more rapidly. Clarification: The final step is the settling of the particles. Particle density, size and shape are important during settling. Dense, compact flocs settle more readily than less dense, fluffy flocs. Because of this, flocculation to form dense, compact flocs is particularly important during water treatment. Water temperature is important during settling. Both the density and viscosity of water are affected by temperature; these in turn February 2005 Volume It—Construction Stormwater Pollution Prevention 15 affect settling. Cold temperatures increase viscosity and density, thus slowing down the rate at which the particles settle. The conditions under which clarification is achieved can affect performance. Currents can affect settling. Currents can be produced by wind, by differences between the temperature of the incoming water and the water in the clarifier, and by flow conditions near the inlets and outlets. Quiescent water such as that which occurs during batch clarification provides a good environment for effective performance as many of these factors become less important in comparison to typical sedimentation basins. One source of currents that is likely important in batch systems is movement of the water leaving the clarifier unit. Given that flocs are relatively small and light the exit velocity of the water must be as low as possible. Sediment on the bottom of the basin can be resuspended and removed by fairly modest velocities. Coagulants: Polymers are large organic molecules that are made up of subunits linked together in a chain-like structure. Attached to these chain-like structures are other groups that carry positive or negative charges, or have no charge. Polymers that carry groups with positive charges are called cationic,those with negative charges are called anionic, and those with no charge(neutral) are called nonionic. Cationic polymers can be used as coagulants to destabilize negatively charged turbidity particles present in natural waters, wastewater and stormwater. Aluminum sulfate(alum) can also be used as this chemical becomes positively charged when dispersed in water. In practice, the only way to determine whether a polymer is effective for a specific application is to perform preliminary or on-site testing_ Polymers are available as powders,concentrated liquids, and emulsions(which appear as milky liquids). The latter are petroleum based, which are not allowed for construction stormwater treatment. Polymer effectiveness can degrade with time and also from other influences. Thus, manufacturers'recommendations for storage should be followed. Manufacturer's recommendations usually do not provide assurance of water quality protection or safety to aquatic organisms. Consideration of water quality protection is necessary in the selection and use of all polymers. Application Considerations. Application of coagulants at the appropriate concentration or dosage rate for optimum turbidity removal is important for management of chemical cost, for effective performance, and to avoid aquatic toxicity. The optimum dose in a given application depends on several site-specific features. Turbidity of untreated water can be important with turbidities greater than 5,000 NTU. The surface charge of particles to be removed is also important. Environmental factors that can influence dosage rate are water temperature, pH, and the presence of constituents that consume or otherwise affect polymer effectiveness. Laboratory experiments indicate that mixing previously settled sediment(floc sludge)with the untreated stormwater significantly improves clarification, therefore reducing the effective dosage rate. Preparation of working solutions and - thorough dispersal of polymers in water to be treated is also important to establish the appropriate dosage rate. February 2005 Volume 11—Construction Stormwater Pollution Prevention 16 For a given water sample, there is generally an optimum dosage rate that yields the lowest residual turbidity after settling. When dosage rates below this optimum value (underdosing) are applied, there is an insufficient quantity of coagulant to react with, and therefore destabilize, all of the turbidity present. The result is residual turbidity(after flocculation and settling)that is higher than with the optimum dose. Overdosing, application of dosage rates greater than the optimum value,can also negatively impact performance. Again, the result is higher residual turbidity than that with the optimum dose. Mixing in Coagulation/Flocculation: The G-value, or just "G," is often used as a measure of the mixing intensity applied during coagulation and flocculation. The symbol G stands for"velocity gradient', which is related in part to the degree of turbulence generated during mixing. High G-values mean high turbulence,and vice versa. High G-values provide the best conditions for coagulant addition. With high G's, turbulence is high and coagulants are rapidly dispersed to their appropriate concentrations for effective destabilization of particle suspensions. Low G-values provide the best conditions for flocculation. Here, the goal is to promote formation of dense,compact flocs that will settle readily. Low G's provide low turbulence to promote particle collisions so that flocs can form. Low G's generate sufficient turbulence such that collisions are effective in floc formation, but do not break up flocs that have already formed. Design engineers wishing to review more detailed presentations on this subject are referred to the following textbooks. • Fair, G., J. Geyer and D_ Okun, Water and Wastewater Engineering, Wiley and Sons, NY, 1968. • American Water Works Association, Water Quality and Treatment, McGraw-Hill, NY, 1990. • Weber, W.J., Physiochemical Processes for Water Quality Control, Wiley and Sons, NY, 1972. Adjustment of the pH and Alkalinity: The pH must be in the proper range for the polymers to be effective, which is 6.5 to 8.5 for Calgon CatFloc 2953, the most commonly used polymer. As polymers tend to lower the pH, it is important that the stormwater have sufficient buffering capacity. Buffering capacity is a function of alkalinity. Without sufficient alkalinity, the application of the polymer may lower the pH to below 6.5. A pH below 6.5 not only reduces the effectiveness of the polymer, it may create a toxic condition for aquatic organisms. Stormwater may not be discharged without readjustment of the pH to above 6.5. The target pH should be within 0.2 standard units of the receiving water pH. February 2005 Volume 11-Construction Stormwater Pollution Prevention 17 Experience gained at several projects in the City of Redmond has shown that the alkalinity needs to be at least 50 mg/L to prevent a drop in pH to below 6.5 when the - polymer is added_ February 2005 Volume Jl—Construction Stormwater Pollution Prevention 18 BMP C251: Construction Stormwater Filtration Purpose Filtration removes sediment from runoff originating from disturbed areas of the site. Conditions of Use Traditional BMPs used to control soil erosion and sediment loss from sites under development may not be adequate to ensure compliance with the water quality standard for turbidity in the receiving water. Filtration may be used in conjunction with gravity settling to remove sediment as small as fine silt(0.5 µm). The reduction in turbidity will be dependent on the particle size distribution of the sediment in the stormwater. In some circumstances,sedimentation and filtration may achieve compliance with the water quality standard for turbidity. Unlike chemical treatment,the use of construction stormwater filtration does not require approval from Ecology. Filtration may also be used in conjunction with polymer treatment in a portable system to assure capture of the flocculated solids. Design and Background Information Installation Specifications Filtration with sand media has been used for over a century to treat water and wastewater. The use of sand filtration for treatment of stormwater has developed recently, generally to treat runoff from streets, parking lots, and residential areas. The application of filtration to construction stormwater treatment is currently under development. Two types of filtration systems may be applied to construction stormwater treatment: rapid and slow. Rapid sand filters are the typical system used for water and wastewater treatment. They can achieve relatively high hydraulic flow rates,on the order of 2 to 20 gpm/sf, because they have automatic backwash systems to remove accumulated solids. In contrast, slow sand filters have very low hydraulic rates, on the order of 0.02 gpm/sf, because they do not have backwash systems. To date, slow sand filtration has generally been used to treat stormwater- Slow sand filtration is mechanically simple in comparison to rapid sand filtration but requires a much larger filter area. Filtration Equipment. Sand media filters are available with automatic backwashing features that can filter to 50 µm particle size. Screen or bag filters can filter down to 5 µm. Fiber wound filters can remove particles down to 0.5 µm. Filters should be sequenced from the largest to the smallest pore opening. Sediment removal efficiency will be related to particle size distribution in the stormwater. Treatment Process Description. Stormwater is collected at interception point(s)on the site and is diverted to a sediment pond or tank for removal of large sediment and storage of the stormwater before it is treated by the February 2005 Volume 11-Construction Stormwater Pollution Prevention 4-117 filtration system. The stormwater is pumped from the trap,pond, or tank through the filtration system in a rapid sand filtration system. Slow sand filtration systems are designed as flow through systems using gravity. If large volumes of concrete are being poured, pH adjustment may be necessary. Maintenance Rapid sand filters typically have automatic backwash systems that are Standards triggered by a pre-set pressure drop across the filter_ If the backwash water volume is not large or substantially more turbid than the stormwater stored in the holding pond or tank, backwash return to the pond or tank may be appropriate. However, land application or another means of treatment and disposal may be necessary. • Screen, bag, and fiber filters must be cleaned and/or replaced when they become clogged. • Sediment shall be removed from the storage and/or treatment ponds as necessary. Typically, sediment removal is required once or twice during a wet season and at the decommissioning of the ponds. 4-118 Volume 11—Construction Stormwater Pollution Prevention February 2005 BMP C252: High pH Neutralization using CO2 Description When pH levels in stormwater rise above 8.5 it is necessary to lower the pH levels to the acceptable range of 6.5 to 8.5, this process is called pH neutralization. pH neutralization involves the use of solid or compressed carbon dioxide gas in water requiring neutralization. Neutralized stormwater may be discharged to surface waters under the General Construction NPDES permit but neutralized process water must be managed to prevent discharge to surface waters. Process wastewater includes wastewaters such as concrete truck wash-out, hydro-demolition, or saw-cutting slurry. Reason for pH neutralization A pH level range of 6.5 to 8.5 is typical for most natural watercourses, and this neutral pH is required for the survival of aquatic organisms. Should the pH rise or drop out of this range, fish and other aquatic organisms may become stressed and may die. Calcium hardness can contribute to high pH values and cause toxicity that is associated with high pH conditions. A high level of calcium hardness in waters of the state is not allowed. The water quality standard for pH in Washington State is in the range of 6.5 to 8.5. Groundwater standard for calcium and other dissolved solids in Washington State is less than 500 mg/l. Causes of high pH High pH at construction sites is most commonly caused by the contact of stormwater with poured or recycled concrete, cement, mortars, and other Portland cement or lime- containing construction materials. (See BMP C 151: Concrete Handling for more information on concrete handling procedures). The principal caustic agent in cement is calcium hydroxide(free lime). Advantages of CO2 Sparging • Rapidly neutralizes high pH water. • Cost effective and safer to handle than acid compounds. • CO2 is self-buffering. It is difficult to overdose and create harmfully low pH levels. • Material is readily available. The Chemical Process When carbon dioxide(CO2) is added to water(H20), carbonic acid(H2CO3) is formed which can further dissociate into a proton (H)and a bicarbonate anion(HCO3-) as shown below: " CO2 + H2O F4 H2CO3 F4 H+ + HCO3_ The free proton is a weak acid that can lower the pH. Water temperature has an effect on the reaction as well. The colder the water temperature is the slower the reaction occurs and the warmer the water temperature is the quicker the reaction occurs. Most construction applications in Washington State have water temperatures in the 50°F or higher range so the reaction is almost simultaneous. Treatment Procedures High pH water may be treated using continuous treatment,continuous discharge systems. These manufactured systems continuously monitor influent and effluent pH to ensure that pH values are within an acceptable range before being discharged. All systems must have fail safe automatic shut off switches in the event that pH is not within the acceptable discharge range. Only trained operators may operate manufactured systems. System manufacturers often provide trained operators or training on their devices. The following procedure may be used when not using a continuous discharge system: • Prior to treatment, the appropriate jurisdiction should be notified in accordance with the regulations set by the jurisdiction. • Every effort should be made to isolate the potential high pH water in order to treat it separately from other stormwater on-site. • Water should be stored in an acceptable storage facility, detention pond, or containment cell prior to treatment. • Transfer water to be treated to the treatment structure. Ensure that treatment structure size is sufficient to hold the amount of water that is to be treated. Do not fill tank completely, allow at least 2 feet of freeboard. • The operator samples the water for pH and notes the clarity of the water. As a rule of thumb, less CO2 is necessary for clearer water. This information should be recorded. • In the pH adjustment structure, add CO2 until the pH falls in the range of 6.9-7.1. Remember that pH water quality standards apply so adjusting pH to within 0.2 pH units of receiving water(background pH) is recommended. It is unlikely that pH can be adjusted to within 0.2 pH units using dry ice. Compressed carbon dioxide gas should be introduced to the water using a carbon dioxide diffuser located near the bottom of the tank, this will allow carbon dioxide to bubble up through the water and diffuse more evenly. • Slowly release the water to discharge making sure water does not get stirred up in the process. Release about 80%of the water from the structure leaving any sludge behind. • Discharge treated water through a pond or drainage system. • Excess sludge needs to be disposed of properly as concrete waste. If several batches of water are undergoing pH treatment, sludge can be left in treatment structure for the next batch treatment. Dispose of sludge when it fills 50%of tank volume. Sites that must implement flow control for the developed site must also control stormwater release rates during construction. All treated stormwater must go through a flow control facility before being released to surface waters which require flow control. Safety and Materials Handling • All equipment should be handled in accordance with OSHA rules and regulations. • Follow manufacturer guidelines for materials handling. Operator Records Each operator should provide: • a diagram of the monitoring and treatment equipment and • a description of the pumping rates and capacity the treatment equipment is capable of treating. Each operator should keep a written record of the following: • client name and phone number, • date of treatment, • weather conditions, • project name and location, • volume of water treated, • pH of untreated water, • amount of COZ needed to adjust water to a pH range of 6.9-7.1, • pH of treated water and, • discharge point location and description. - A copy of this record should be given to the client/contractor who should retain the record for three years. BMP C253: pH Control for High pH Water Description When pH levels in stormwater rise above 8.5 it is necessary to Iower the pH levels to the acceptable range of 6.5 to 8.5, this process is called pH neutralization. Stormwater with pH levels exceeding water quality standards may be treated by infiltration, dispersion in vegetation or compost, pumping to a sanitary sewer,disposal at a permitted concrete batch plant with pH neutralization capabilities, or carbon dioxide sparging. BMP C252 gives guidelines for carbon dioxide sparging. Reason for pH neutralization A pH level between 6.5 and 8.5 is typical for most natural watercourses, and this pH range is required for the survival of aquatic organisms. Should the pH rise or drop out of this range, fish and other aquatic organisms may become stressed and may die_ Causes of high pH High pH levels at construction sites are most commonly caused by the contact of stormwater with poured or recycled concrete,cement, mortars, and other Portland cement or lime-containing construction materials. (See BMP C151: Concrete Handling for more information on concrete handling procedures). The principal caustic agent in cement is calcium hydroxide (free lime). Disposal Methods Infiltration • Infiltration is only allowed if soil type allows all water to infiltrate(no surface runoff)without causing or contributing to a violation of surface or groundwater quality standards. • Infiltration techniques should be consistent with Volume V, Chapter 7 Dispersion Use BMP T5.30 Full Dispersion Sanitary Sewer Disposal • Local sewer authority approval is required prior to disposal via the sanitary sewer. Concrete Batch Plant Disposal 0 Only permitted facilities may accept high pH water. • Facility should be contacted before treatment to ensure they can accept the high pH water. Stormwater Discharge Any pH treatment options that generate treated water that must be discharged off site are subject to flow control requirements. Sites that must implement flow control for the developed site must also control stormwater release rates during construction. All treated stormwater must go through a flow control facility before being released to surface waters which require flow control. Appendix E — Site Inspection Forms The results of each inspection and monitoring event shall be summarized in an inspection report or checklist that is entered into or attached to the site log book. An Inspection Report has been included in this appendix for reference. Completed inspection forms should be kept onsite at all times during construction. , Inspections should be performed and documented as outlined below: Inspection date/times Weather information: general conditions during inspection, approximate amount of precipitation since the last inspection, and approximate amount of precipitation within the last 24 hours. A summary or list of all BMPs that have been implemented, including observations of all erosion/sediment control structures or practices. • locations of BMPs that need maintenance, • the reason maintenance is needed, • locations of BMPs that failed to operate as designed or intended, and locations where additional or different BMPs are needed, and the reason(s)why A description of stormwater discharged from the site. The presence of suspended sediment, turbid water, discoloration, and/or oil sheen shall be noted, as applicable. A description of any water quality monitoring performed during inspection, and the results of that monitoring_ General comments and notes, including a brief description of any BMP repairs, maintenance or installations made as a result of the inspection. A statement that, in the judgment of the person conducting the site inspection, the site is either in compliance or out of compliance with the terms and conditions of the SWPPP and the NPDES permit. If the site inspection indicates that the site is out of compliance, the inspection report shall include a summary of the remedial actions required to bring the site back into compliance, as well as a schedule of implementation. Name, title, and signature of person conducting the site inspection; and the following statement: "I certify under penalty of law that this report is true, accurate, and complete, to the best of my knowledge and belief'_ When the site inspection indicates that the site is not in compliance with any terms and conditions of the NPDES permit, the Permittee shall take immediate action(s) to: stop, contain, and clean up the unauthorized discharges, or otherwise stop the noncompliance; correct the problem(s); implement appropriate Best Management Practices (BMPs), and/or conduct maintenance of existing BMPs; and achieve compliance with all applicable standards and permit conditions. In addition, if the noncompliance causes a threat to human health or the environment, the Permittee shall comply with the Noncompliance Notification requirements in Special Condition S5.F of the permit Construction Site Erosion & Sediment Control Inspection Sheet Project: Date: Inspected by: Time: Weather: Duration since last rainfall? Currently 24 hours 2-3 days >5 days BMP Observations, Comments, Corrective Actions Construction Access OK Not OK Sediment,mud and debris cleaned from public roads?Stablilized.rocked entrance to the site? Adequate provisions to prevent mud and tracking off-site? Soil Stabilization OK Not OK Sediment traps,barriers and basins clean and functioning properly?Site seeded and mulched or blanketed(estimated%coverage&growth)? Stockpiles located in approved areas and protected from erosion? Slope Protection OK Not OK Exposed slopes protected from erosion through acceptable soil stabilization practices? Perimeter Control OK Not OK Silt fencing propoeriy installed/functioning. No blow out or erosion around prerimeter. Dust Control OK Not OK Visible dust in air for extended duration? Outlet Protection OK Not OK Outlets(ponds,pipes,bypasses,spreaders) protected w/rock or equiv.to prevent erosion? Inlet Protection OK Not OK Socks installed&functional? Sediment removed from around CB? Conveyances Stable OK Not OK Channels protected,check dams inplace,signs of erosion/undercutting? Sediment Pond(s)Traps(s) OK Not OK Adequate detention/storage volumes? Sediment being removed as needed?Erosion on inside slopes of structure? Spill Prevention OK Not OK Material handling and storage and equipment storage and maintenance areas clean and free of spils and leaks? - BMP Maintenance OK Not OK Erosion Control practices in place and functioning?BMPs in accordance with the site's SWPPP? Outfall/Pond Monitoring Location Visual Observation NTU pH Clear Cloudy Mudd Clear Cloudy Mudd Clear Cloudy Mudd Clear Cloudy Mudd Clear Cloudy Mudd Water Quality Observations, Comments, Corrective Actions I certify that this report is true, accurate, and complete to the best of my knowledge and belief. Inspector Initials: Appendix E: Temporary Erosion and Sedimentation Control Plans C N i-_-_R_A` I, IT F J O\ AN' S7 U L. HA A,.E NE k OP EL,;W GRO,;NDWAIE R[XCA%A1. A 'dIN MUM ANC 9ACKF,l W His-LAN RUSH_) RV, „► .,. III Yc _ ' ,.1` [:2:7>CCVER ALL EX CSEE --ARP SUP-G„ES All-I SLO=ES FLA'IEP _HAN C 1. NI H S,RAW 440LC ✓/ ♦ __ CCVER ALI FX . EF -A t- UP N H t I SLOPES OF 21 R STFFPFR, WI I- PLA"IC <.. SH_"'\C, PER rt F3__>THE WEEKLY INSPECTION CuNE cti .i - - --•< CONTRACTOR/ESC SUPLR!ISO^ WILL INC,,D: INSPECTION Cf 7-E CIL/WATER SEPAPATCP. FCR • SEDIMENT AND OI- B:ILDCP A ` CONSTRUCTION 5LOCK AND GRAVEL CURT INLET PROTECTION AND CATC OF T CN ) EAS\ ILTE PER T - CORSTE, PLAN: :< 216.30- TvPCAL OPEN CATCH EASN - -. - ! "'.. _,__ • GRATES UP TC ,GO DOWNSTREAM OF P;3, } MITS i a :NS"ALL THE BAG LADY INC CGN:TR CTIGN cN RANCE PLAIL CP AcPRO LE) 'OUA -_ - I� '..ILQL EXISTIK CATCH EAST\ AS SAMPLIN ...- _ _ STATION. SEE TESL NC'ES fCE WATER \ 'e - - - EFFLUENT REOUIRENEMS c 3 1 — x 3. may' 1. s c KI ' 15 - av A (I- � C T LOCA710N I C752 71 - i I - .ro t ( ns3 C155 J t CIS- . C158 \-_.- I b I Ci67 - Ct67 64 c- - Ct65 ^i cl C 169 I \ I C17D -'A I SCALE IN FEE'--- - r 1 r MATCH LINE FOR CONTINUATION SEE. SHEET EC168D ISSUE FOR CONSTRUCTION MAGNUSSON JUNE 15,2011 KLEMENCIC ASSOCIATES ■ TID Ml=rzoem 201 - 4[NSgN P'* sDDRpAC IY�I SYY RMSON ffi WPRpAO DAl[ NDE SUR , CUAREx•F S.. S•u9p, Da'C - ACCEPTABILITY BW.ROEERTSON 06.15.n TEMP.EROSI NAND .'1R y SPECWIIL IS�,S ANDRED N.J.JDNE$ 06.15.1I SEDIMENTATION CONTROL PLAN S�E� - - -- -- BOElNc® RE 4-55 BE[ BUILDING EC157D D 81 DEP. p TE N.J. %45 D6.15.I7 o � ! crtEa BUILDING 04-68-75 08 „-,3676 DYo MD 'I w'T - CIVIL MASTER RENTON°MG h0 R'\-vD-EC,57D x i I �. i�;F K'', 'V-1 Ems, MATCH LINE FOR CONTINUATION SEE SHEET EC157D L F s ON ANY c R IL IRES RE NCR OR '-ELO 'i_♦t ��tiF a EGEX F _ A tJ 11M-M �. 6" / AND -4CK W H Q[AN RUSH ROCK CC''-R A- k SEC E ART SURF c cS ER THAN 2 1, AH S7PAVj MULC.. CC'..R A..,. krOSED EAFT' c R;ACFS &7;— SLR ES 01 21 CR SE_ ER, to"H _gcT;r S , SH--[NC PER THE WEEKL. INS PECT'.ON E,CNE El CCN?RAC-CR/ESC SC:PERV,SOR A'IL'_ INCLUDE INSPECTICN Cr TTE O'L/WATER SEPARATOR FOR SE'IMEN' AND OC EUI;DUP. } OONSTR-CTION NOTE _ _ • - ` . "-, ' D�- CLOCK AND ',RAVE. CURB INLET PROTECTION PER CI-Y OF RENTON (COR) STD PLAN 216.40 •' `, ? _` - AND CATCH BASIN Ft-ER PER CCR SC PLAN - 2'6.20 TOPICAL AT OPEN CATCH BASIN I i GRA'ES U'F TC tOC' DOWNSTREAM CE PROJECT I > I,7IUZE SEW 637 (LOCATED AT THE OUTLET __ . . c c., F TH� Ohm/WATER SEPARATOR) a_ .,AMPL,NG SATION. SEE iESC NOTES FOR WATER :FFLu ENT REQUIREMENTS. - _ I z -- _ _ KEY PLAN EAN ..i., ♦ > ` h` -. 7-4 0. B C D E F G H j K _. 'SD IF MUT ti •.o s , 1 , 7 \ - 57 1 i.D y-_\ C,59 � o c , C1Et _-__— i !5 6 .`' ! I •t` a--._- -. _._. '-__._ -_. _...__ - C167 y l to " - ... I _ /i \ z _GALE N _E' �I BE O ATEC a l CA. cDMH ISSUE FOR CONSTRUCTION CT MAGNUSSONKILEMENCIC JUNE 15,2011 ASSOCIATES ■ :�oa�n tmormszri tm+ cvM RCYISKIN Bt /F=aCx2C Gc'C SYu. RE`n50f. 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CLEAR TO BLDG FF = 22.28' a Ci6' E 21.9E FOUNDATION Z C168 _ _ •20.51 g19.43 J C169 1 2 3J 19�91' U C170 'q i 2-1- 2w '20.1& Q 07.• N i �l �C 20.63 ; I ., 20 t� �0 22 2E SCALE M FEET c 68 20E9 MATCH LINE FOR CONTINUATION SEE SHEET C158D ISSUE FOR CONSTRUCTION mAGNUSSON JUNE 15,2011 xLEnAENcTES �'9a,D,9ln ASSOCIATES ■ 7.mem,mG E.main iza 5•'M R[N15gx P+' WRRCvEE Gs't _ REMSgN 8• aRRADdG GAR SUETME CIMREN`REVS'. 5"u L r fY-E -- v ACCEPTABRITY B.W.ROBERTSON o6,15.11 GRADING PLAN a _ ,� THIS DESIGN aND/OF 1 171, E76 _ 06.15.11 ARMING i0' 1<_- REI }-12-04 E NEW BUILDING FOR 0FE-IFC 1171367E MKA M.J.JONES 06.15.11 t` ' y SPEC",CAT",r MRRO<7D M.J.JONES 06.15.11 sNEE' 7 A S`;L'E FOR CONSIRJ'TION JFC'_1D-8 REI DEC E-4-&K RDNED B, DER-. peiE M.J,JDNES 06.15.11 .na 4-68 BFE BUILDING C / D - BOE/NG „EN D 8 DRAWING Or RECORC itc31098-- REI OEC 'tt-4-D4 ..�, _ BUILDING 04-68-75 , Np. 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O �' 22.15 22,26 / r I 1 ; � y / / // s % �. � INSTALL 5' WIDE FLAT LANDING WITH DETECTABLE w, l 21.9� WARNING PATTERN. _ �', ) }-ab � t-� � NI, 2.96 5 � 5 ��'• �� _�i __--h 2 6i ,.. cf) • - _ L--3 = t INSTALL HEAVY DUTY ASPHALT PAVEMENT - f e 2'2_% PER 4 w y, -t% W '� 20.33 20.8a 0.57. 21.t8 _ fn �- CT58D C581 z a� - _. 21.62 6cL b Z STALL CONCRETE PAVEMENT PER ~¢ a a. - - — - -- - - _ ..._ ...-SAwcuT LINE __ -- // 2. } - _ _ _ - z - - O MCt58D C582 f----- - 2195 -- Z i INSTALL 2' WIDE OPENING IN CURB. O KEY PLAN ' i s .• / i O ` OYA lem#Bt6ILL A B C D E F G N K L W 1 .. - NFL NP,W WAc /f a c15C a"r W 27.b5 X VA-CH. _, E a63123 9B5b./. = C151 _ M 7 (.,) `- �. G EX - = y 4 (. / p a6C _ T l 61 I ° T C160 9.� 1 � I P ---- 's _I - - --- - - - i ? ----- SCALE 9 TEE' 2 1 40 MATCH LINE FOR CONTINUATION SEE SHEET C159D y ISSUE FOR CONSTRUCTION MAGNUSSON '"° "� `""" KLEMENCIC JUNE 15, 2011 ASSOCIATES . 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II J.. - 'Y �' �C8 TYPE t a INV Ttj t8'0 1 MIN SLOPE=C.sT _ I E!�> CONNECT 6- STORM DRAIN PIPE TO ACO 4 8 INV(8C.32.18 1 t 6.76 .. ,� -�,, - - CB TYPE 1 / I POWERORAIN S3CCK TRENCH DPAIN WITH NLINE j( RIM=2028 - CATCH BASIN.INV(8)17,10 `i_; _ I CONCRETE ENCASE STORM DRAIN PIPES A THE $y - �• =- _` ;E d 1 RCAC!iMADDEPH� LtiAT,ALLGWS KFOR AIM'HNYM OC 1 3" BETWEEN HE 'OP Of FIPE AND THE BOTTCM d I OF CONCRETE SLA;—q r3 C17DTC582 - - m✓168< lO III /� INS-ALL 6" HOPE 5'ORM DRAIN PIPE. ' ,M _ _- L '8.8a-G iE E< INSTALL 8" HDPE STORM DRAIN PIPE. - ttiu t7 09 �L2 INSTALL i2 HOPEE STORM RM DRAIN PIPE-4 T INSTALL STORM DRAIN CLEAN OUT PER DETAIL CCP - \ I STD PLAN 403.`. CONNECT ROOD DOWNSPOUTS TO - ? 19.18 RIu N 4 CB TYPE 1 I PROPOSED STORM DRAIN. Nv C.E'.12)1E 69 - RIM=18,41 INV(6-,E-)15.79 D�:-INSTALL TYPE 2 STORM DRAIN CATCH BASIN, 48"0 PER CDR STD P-AN 201.0C WITH RECTANGULAR VANED GATE PER COP STD P-AN 204.20. Il •• INV 17.17 I 4-68 BFE BUILDING IN-TALL 12" N"LOPLAST DRAIN DASIN WITH A 12' INV 1673 LIG�l DUTY COUPLING I DOME CDR I\SlA-L BASINDTO[DUCTILE `<' \7 �y IRON PIPE. V�>IN57ALL 18" D..CT'-E IRON STORM DRAIN PIPE. ' 1 - IE 12"= 18,14 - CCNNECT TO EX'STING $TRLCiURE AT INVERT - \4• N, I ELEVATION SHOWN. ti I I 2 C' 40. i SCALE IN CEET ISSUE FOR CONSTRUCTION MAGNUSSON JUNE 15, 2011 KLEMENCTES ASSOCIATES ■ T:A6M1A0 E.1p61!%,101 RC4151A+ a. Aror+tMC Coz Sw Ii('ASRM. gv MPRO'+FD 6IL s,e'I•,E CWREx'PE�nsrou Swap` DAiE NEW J ACCEPTABILITY FIX ROBERTSGN 0&15.1t SITE PLAN 11713676 1 06.15.11 cfM NEW BJILDII•M FOR BFE-IFS it7:3676- MK4 u.J.JONES 06.75.t1 A WESI SHOP DEMO J 30306 REI DED 9.30.03 sa' THIS DE50N AND/OP /' < '♦ SPE[6KA701`IS APPROVED M.J.JOKE 06.15.11 s+Ct- JPDATED U/G UULIT-MAPPING-DHA,INC. JGC DNi 72/37/97 E PMK.NG l07 15 RE[ DED 3/12/04 0 aovEp e. OEr. owE M.J.JONES 06.15.11 1oEe 4-68 rFE BUILDINGCHECKED C 17D ADDED EMCS UNDERGROUND UTILITIES-IXV.,INC. GRE MUM 1.102198 C ISSUE FOR CONSTRUCTION J/031098 RE[ DID 6.4.04 JPDATE OUIFALL MTERCCPTOR MAPPING-KCM,INC. JLE JV+L d/30/99 D2 DRAWING OF RECORD(see Archive to,DI J�140882 RE! OED +.2.12.07 III q'tf E BUILDING 04-68-75 ace 11713676 caw UPDATED U/G C/!MITl MAPPING,DHA INC. AK DAH 10/07.99 E a-6B BFE BWLDMG- Ic(' 1ODt 11523990 MKA M.J.JOKES O4.OB.It b�15, r",D`A`EA-- CryIL MASTER RENTON RiN-YD-C17D i i MATCH LINE-FOR CONTINUATION SEE SHEET C17D Iv F N-R,AL NOTES IE :2'_ 7.89 — _ — — — — — — — PI=L BEDDING & TRENCHING PER P-2G1ON ANY STRUC'URES THAT ARE NEAR ORRBELOW N /��\ GROt:NDWATER, CVER EXCAVA'E A MINIMUM OF 6" I E(8 12 1(CIS $ IS AND BACK FILL WITH CLEAN CRUSHED ROCK. 'j a --IE +2'_ '7.65 yT R-ONST UCTION N 0 ES ✓ INSTALL UTILITY BOLLARD PER 3 C78D C581 I , IF t2' 17,40 INSTALL POST INDICATOR VALVE. lw 4-66 BFE BUILDING [3:,_-�l INSTALL 8"DUCTILE IRON CLASS 52 FIRE SERVICE. k CONNECT 10 EXISTING 8" DCCTILE IRON FIRE MAIN PER COR STD PLAN 300.1. p CONNECT TO 8" BUILDING FIRE SERVICE. 1' ,� INSALL 4"x4" TEE AND CONNECT TO EXISTING `t Al IL 12'= 17.15 6 . WATER SERVICE. 1 i 6 I 1 I � INSTALL 4" DUCTILE IRON WATER SERVICE. " 2C.81 N "CONN TO M[CN 8 - I ® INSTALL 4" GATE VALVE PER CDR STD. PLAN f 3301. <: MINVSLoOE csz zo n \ I IF lz'= 1690 - I� INSALL 8" DUCTILE IRON STORM DRAIN PIPE. RIM 121762 .16.83 5 1 vu 7PE.1 - -� .1 1 INS-ALL 6" HDPE STORM DRAIN PIPE. _ i3?3'PvC S'S N.S IE.25 m 9 INSTALL 8" HDPE STORM DRAIN PIPE. 2 8 DI Si 8 t550 - _ 1 _ INSTALL 12" HDPE STORM DRAIN PIPE a '" _ INV 18.0 •o, � �, INv 20 46 r' - • - - INSTALL 12 DUCTILE IRON STORM DRAIN PIPE. u) CB TYPE �y r 4 INS-ALL ACID PO ERGRAIN S300K TRENCH DRAIN . M69RI 'f CONNECT 6" STO RM DRAIN PIPE TO AC O POWERDRAIN S300K TRENCH DRAIN WITH IN IN E CATCH BASIN,F R�:_ INSTALL TYPE I STORM DRAIN CATCH BASIN. PER �I CDR STD PLAN 200.00 WITH RECTANGULAR 81-DIRECTIONAL VANED GATE PER CDR STD PLAN Y LU ai 204.30. INSTALL STORM DRAIN CLEAN OUT PER DETAIL CDR STD PLAN 403.1.PROPOSED STORM DRAIN. CT ROOF DOWNSPOUTS T IN.N 1 E SE INSTALL METAL EXISp R G SOLID D COVER ON NG CATCH BASIN PER CDR SID. PLAN 204.10. ,` u ---- --- — [3:�> INS-ALL 8X6-2L FILTERRA INTERNAL BYPASS UNIT I I BEHIND CURB WITH HIGH FLOW BYPASS PIPE CONNECTION TO EXISTING CATCH BASIN. 8" IE _ 16.58. D___ INSALL 8x4-2R FILTERRA INTERNAL BYPASS UNIT a �) ----- ------ ---- BE^IND CURB WIT, HIGH FLOW BYPASS PIPE CONNECTION TO EXISTING CATCH BASIN. 8" IE _ "m J1�M - _ _ --. 1648 . 7r ilp -- -- Vj__> INSTALL THREE 3" SCH 40 PVC STORM DRAIN ! - PIPES THROUGH THE CURB AT THE FLOWLINE ELRIATIONS SHOWN. MAINTAIN A MINIMUM OF 3 FROM OUTSIDE " E 0� PIPE 10 OUTSIDE OF PPE.I CCNNECT 70 EXISTING STRL'C'URE Al INVERT ----- ____._...__ .._ _ -.._. - >� L ELEVATION SHOWN. i` .a _ £ ,. --— SCALE N FEET - I MATCH LINE-FOR CONTINUATION SEE SHEET CI9D ISSUE FOR CONSTRUCTION MAGNUSSON JUNE 15, 2011 KLEMENCIC ASSOCIATES tfoem lm F.sYml]Ol 5w REV" 6* APRRDrTD DATE SY R[MSIDA Br APPRMD DAIC A' SVBTir CU N*Ms, ACCEPTABILITY ACCEPTABILITY D.W.ROBERTSON 06.15.t` F 4-68 BFE BUILDING-IFC 100% 11523990 MKA M.J.JONES 104.OB17 A RECORD DWG.WATER REHA6 PH.6E KARAL'JS GAK 07.1 ZOI cv4 ..;,.�9P THIS DESIGN AND/Ok SITE PLAN t 17t3676 IJ 06.15.11 a SPECIEICATON 6 ARPRmD MJ.JONES 06.15,11 SWEET G NEW BUILDING FOR BEE-6C 11713676 MKA MJ JONES 06.15.11 B PARKING LOT 15,16,&17 J 130306 R6 CEO 9 30 0_ ® + 4-68 BFE BUILDING C18D I I' BOE/A/G - R�vTD B�' JEF'. CkTE yHJ�JONES a 5.11 UPDATED U/G UT0.1T,'MAPPING-DNA,INC. SDP I 05/01/98 C PARKING LOT 15 RE'. DID 3/12/04 ADDED IMCS UNDERGROUND UTILITIES-DR4 W. GRE MJM 11/03/98 D ISSUE FOR CONSTRUCTION J1037098 RP DFD 6.a,0a oI F ,` E BUILDING 04-68-75 JOB N0 11713676 ca RD UPDATE OUTFALL INTERCEPTOR MAPPING- KCM,INC. JLF JWL 18/30/99 E DRAWING OF RECORD JP'40882 REi DED t2.12.C7 SUONAE e CIVIL MASTER RENTON o No. RTN-YD-C18D