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04139M Final TIR
Core Design, Inc. MERLINO SHORT PLAT i Merlino Short Plat Table of Contents 1 PROJECT OVERVIEW ................................................................................................................ 1 Figure 1-1: Vicinity Map ........................................................................................................ 2 2 CONDITIONS AND REQUIREMENTS SUMMARY ................................................................ 3 2.1 Core Requirements ................................................................................................................ 3 2.1.1 Core Requirement #1: Discharge at the Natural Location ............................................ 3 2.1.2 Core Requirement #2: Offsite Analysis ......................................................................... 3 2.1.3 Core Requirement #3: Flow Control ............................................................................. 3 2.1.4 Core Requirement #4: Conveyance System .................................................................. 3 2.1.5 Core Requirements #5: Erosion and Sediment Control ................................................. 3 2.1.6 Core Requirement #6: Maintenance and Operations ..................................................... 3 2.1.7 Core Requirement #7: Financial Guarantees and Liability ............................................ 3 2.1.8 Core Requirement #8: Water Quality ............................................................................ 3 2.2 Special Requirement #1: Other Adopted Area-Specific Requirements ................................ 3 2.2.1 Critical Drainage Areas ................................................................................................. 3 2.2.2 Master Drainage Plan .................................................................................................... 4 2.2.3 Basin Plans..................................................................................................................... 4 2.2.4 Salmon Conservation Plans (SCPs) ............................................................................... 4 2.2.5 Stormwater Compliance Plans (SWCPs) ....................................................................... 4 2.2.6 Lake Management Plans (LMPs) .................................................................................. 4 2.2.7 Flood Hazard Reduction Plan Updates (FHRPs) ........................................................... 4 2.2.8 Shared Facility Drainage Plans (SFDPs) ....................................................................... 4 2.3 Special Requirement #2: Floodplain / Floodway Delineation .............................................. 4 2.4 Special Requirement #3: Flood Protection Facilities ............................................................ 4 2.5 Special Requirement #4: Source Controls ............................................................................ 4 2.6 Special Requirement #5: Oil Control .................................................................................... 4 3 OFFSITE ANALYSIS .................................................................................................................. 5 3.1 Study Area Definition and Maps ........................................................................................... 5 3.2 Resource Review ................................................................................................................... 5 Basin Reconnaissance Summary Reports ............................................................................... 5 FEMA Maps ........................................................................................................................... 5 Sensitive Areas Folio .............................................................................................................. 5 City of Renton Soil Survey ..................................................................................................... 5 Downstream Drainage Complaints ......................................................................................... 5 Core Design, Inc. MERLINO SHORT PLAT ii 3.3 Field Investigation ................................................................................................................. 5 Upstream Tributary Area ........................................................................................................ 5 Level 1 Downstream Analysis ................................................................................................ 6 Field Investigation .............................................................................................................. 6 3.4 Mitigation of Existing and Potential Problems ................................................................... 10 Downstream Drainage Problems Requiring Special Attention ............................................ 10 Department of Ecology 303d Listings .................................................................................. 10 Drainage Adjustments .......................................................................................................... 10 4 FLOW CONTROL AND WATER QUALITY DESIGN ........................................................... 11 4.1 Existing Site Hydrology ...................................................................................................... 11 4.2 Developed Site Hydrology .................................................................................................. 12 Figure 4-1: Existing Conditions Basin Exhibit .................................................................... 13 Figure 4-2: Developed Conditions Exhibit .......................................................................... 14 4.3 Performance Standards........................................................................................................ 15 Flow Control: Duration Standard Matching Forested Site Conditions ................................ 15 Conveyance Capacity ........................................................................................................... 15 Water Quality: Basic Water Quality Menu .......................................................................... 15 4.4 Flow Control System ......................................................................................................... 15 Calculation of Lot Impervious Area ..................................................................................... 15 Flow Control BMPs/Individual Lot BMPs ........................................................................... 16 Bypass Area .......................................................................................................................... 17 Detention Pond Modeling ..................................................................................................... 17 KCRTS Vault Calculation ................................................................................................ 17 4.5 Water Quality Calculations ................................................................................................. 18 Basic Wetvault ...................................................................................................................... 18 5 CONVEYANCE SYSTEM ANALYSIS AND DESIGN ........................................................... 21 5.1 Rational Method .................................................................................................................. 21 5.2 Backwater Analysis ............................................................................................................. 22 Figure 5-1: Catch Basin Tributary Areas Exhibit ............................................................ 25 6 SPECIAL REPORTS AND STUDIES ....................................................................................... 27 7 OTHER PERMITS ...................................................................................................................... 29 8 ESC ANALYSIS AND DESIGN ................................................................................................ 31 9 BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT .................................................................................................................................. 35 Bond Quantities ......................................................................................................................... 35 Facility Summaries ................................................................................................................... 35 Declaration of Covenant ........................................................................................................... 35 Core Design, Inc. MERLINO SHORT PLAT iii 10 OPERATIONS AND MAINTENANCE .................................................................................. 37 Appendix A – Parcel & Basin Information King County Parcel Report (2225069082) King County Parcel Report (2225069083) Appendix B – Resource Review & Off-site Analysis Documentation FEMA Map (53033C0977F) City of Renton Aquifer Protection Zones City of Renton Groundwater Protection Areas City of Renton Sensitive Area Maps City of Renton Soil Survey Drainage Complaints Exhibit Downstream Drainage Map Appendix C – Pond Sizing City of Renton Flow Control Map Rainfall Region & Regional Scale Factor (Figure 3.2.2.A) KCRTS Hydrologic Soils Group Table (Table 3.2.2.B) Mean Annual Storm Precipitation (Figure 6.4.1.A) KCRTS Input Vault Summary Peaks Analysis Durations Analysis Appendix D – Conveyance Calculations Rational Method Runoff Calculations Backwater Calculations Appendix E – Special Reports and Studies Drainage Design for the WSDOT Exchange Property – I-405 Corridor Design-Builders, Revised July 7, 2010 Coal Mine Hazzard Assessment - Icicle Creek Engineers, April 23, 2014 Critical Areas Report - Icicle Creek Engineers, April 23, 2014 Core Design, Inc. MERLINO SHORT PLAT Page 1 1 PROJECT OVERVIEW The project site is located at Cedar Avenue S and SE 7th Street in the City of Renton, King County. Specifically the project is in the northwest quarter of Section 20, Township 23 North, Range 5 East, W.M. The site is bordered by the Cedar Crest Condominiums to the north, single-family residential homes on the east, the Puget Sound Energy transmission line to the south and I- 405 to the west. The King County Parcel Reports before the boundary line adjustment was completed are included in Appendix A. Table 1 below shows the project area after Lot Combination was completed in November 2014. Table 1: Parcel Information Parcel Area (SF) Lot 2 3.68 ac The project site is approximately 1.60 (including the frontage area) acres in size and is currently covered in grass. Cedar Avenue S drains south though an existing storm drain system and outlets to a Class 5 stream south of the proposed project. The 2:1 slope constructed in 2010 as part of the construction of the WSDOT I-405, I-5 to SR 169 Stage 2 Corridor Widening Project drains west to a ditch flowing south on the west boundary of the site. The flatter portion of the site drains south to an existing onsite ditch north of the WSDOT access road where it has its confluence with the ditch on the west boundary. The site does not receive any upstream flow. The site was mass graded as part of the I-405 project, so there will be no clearing and minimal grading to construct seven single-family lots, the stormwater vault and the associated utilities. Half-street frontage improvements on Cedar Avenue S will be completed to provide 13.5 feet of pavement from the right of way centerline, curb and gutter an 8-foot planter and a 5-foot sidewalk. See Figure 1-1: Vicinity Map, provided below. The project will be designed using the guidelines and requirements established in the 2009 King County Surface Water Design Manual (2009 KCSWDM) and City of Renton Amendments to the King County Surface Water Manual (COR Amendments) The project is required to apply a Flow Duration Standard to Forested Conditions and Basic Water Quality. The drainage analysis for detention sizing was modeled using the King County Runoff Time Series (KCRTS) software. The water quality facility sizing calculations are based on methods described in Chapter 6 of the 2009 KCSWDM. The conveyance calculations will be completed using the Rational Method and the King County Backwater program. One combined detention and water quality treatment vault will be located at the south end of Cedar Avenue S in the cul-de-sac. The treated and detained flows will then be discharged west into the existing ditch north of the WSDOT access road where it will combine with a ditch flowing south at the bottom of the 2:1 slope. Core Design, Inc. MERLINO SHORT PLAT Page 2 Figure 1-1: Vicinity Map PROJECT Core Design, Inc. MERLINO SHORT PLAT Page 3 2 CONDITIONS AND REQUIREMENTS SUMMARY The proposed project is classified as requiring “Full Drainage Review” per the COR Amendments. Therefore, all eight core requirements and five special requirements will be addressed per Section 1.1 of the 2009 KCSWDM). 2.1 Core Requirements 2.1.1 Core Requirement #1: Discharge at the Natural Location The combined detention and water quality vault will discharge at the natural discharge location to the ditch north of the WSDOT access road and the ditch at the bottom of the 2:1 slope on the west side of the project. 2.1.2 Core Requirement #2: Offsite Analysis This core requirement is addressed in Section 3 of this report. 2.1.3 Core Requirement #3: Flow Control The detention vault has been designed to a flow control duration standard matching forested site conditions per page 1-35 of the COR Amendments. This requires that the developed condition discharge durations match the existing condition durations from 50% of the 2-year to the 50-year storm events and that the developed 2-year and 10-year peak discharge rates do not exceed the existing 2-year and 10-year peak discharge rates, respectively. 2.1.4 Core Requirement #4: Conveyance System The backwater analysis included in Section 5 shows that the proposed conveyance system provides sufficient capacity for the 100-year storm as calculated by the Rational Method. 2.1.5 Core Requirements #5: Erosion and Sediment Control Erosion and sediment control will be provided through catch basin protection, silt fencing and mulching. The permanent detention/water quality vault will also be utilized as a temporary sediment pond during construction. 2.1.6 Core Requirement #6: Maintenance and Operations The City of Renton will own and maintain the detention/water quality vault. 2.1.7 Core Requirement #7: Financial Guarantees and Liability A bond quantities worksheet has been included in Section 9. 2.1.8 Core Requirement #8: Water Quality Basic water quality treatment will be provided by dead storage in the vault. 2.2 Special Requirement #1: Other Adopted Area-Specific Requirements 2.2.1 Critical Drainage Areas This project is not in an aquifer protection zone or groundwater protection area. Core Design, Inc. MERLINO SHORT PLAT Page 4 2.2.2 Master Drainage Plan Not applicable. 2.2.3 Basin Plans Not applicable. 2.2.4 Salmon Conservation Plans (SCPs) Not applicable. 2.2.5 Stormwater Compliance Plans (SWCPs) Not applicable. 2.2.6 Lake Management Plans (LMPs) Not applicable. 2.2.7 Flood Hazard Reduction Plan Updates (FHRPs) This project is not within a floodplain (see FEMA map included in Appendix B) and is not within an area with an applicable Flood Hazard Reduction Plan. Therefore, additional requirements from a Flood Hazard Reduction Plan do not apply. 2.2.8 Shared Facility Drainage Plans (SFDPs) Not applicable. 2.3 Special Requirement #2: Floodplain / Floodway Delineation This project is not located within the 100-year floodplain (see FEMA Map included in Appendix B). 2.4 Special Requirement #3: Flood Protection Facilities As this project is not located within a 100-year floodplain there are no levees, revetments or berms within the project. 2.5 Special Requirement #4: Source Controls These requirements are not applicable as the project is not a commercial, industrial or multi-family development. 2.6 Special Requirement #5: Oil Control This requirement does not apply because the project is not a commercial or industrial development nor is it expected to have more than 15,000 vehicles per day. Core Design, Inc. MERLINO SHORT PLAT Page 5 3 OFFSITE ANALYSIS 3.1 Study Area Definition and Maps Per the Lot Combination completed in November 2014, the proposed project contains Lot 2 which is 160,943 square feet. A new parcel number has not been issued by the King County Assessor at this time. A map of the downstream can be found in Appendix B Downstream Drainage Map. 3.2 Resource Review Basin Reconnaissance Summary Reports No Basin Reconnaissance Summary Reports are available for the area that is within one mile of this project site. FEMA Maps A FEMA map dated May 16, 1995 number 53033C0977F was reviewed. The site is not located within a floodplain as it is covered by “Zone X – Outside of 500-year floodplain. The FEMA Map is included in Appendix B. Sensitive Areas Folio The City of Renton Sensitive Area Maps are included in Appendix B. Below is a summary of the project site regarding Coal Mine Hazards, Erosion Hazards, Steep Slopes and Landslides: • Coal Mine Hazard – Moderate (A small portion of the south end of the site is located within the moderate region.) • Erosion Hazard – High • Steep Slopes – Due to the 2:1 slopes a majority of the site is located within the 40% to 90% slope range with the remainder of the site no steeper than 10%. • Landslide Hazard - Moderate City of Renton Soil Survey The City of Renton Soil Survey Reference 11-C shows the site as having BeD or Beausite (Till) soils. The Soils Map exhibit is included in Appendix B. Downstream Drainage Complaints Drainage complaints were researched within the study area. King County lists only one complaint (for dumping) downstream of the site which is over a quarter of a mile away and was closed in 1995, therefore there are no current documented downstream problems associated with this project site. See the Drainage Complaint Exhibit Appendix B. 3.3 Field Investigation Upstream Tributary Area There is no upstream tributary area for this project. Core Design, Inc. MERLINO SHORT PLAT Page 6 Level 1 Downstream Analysis Field Investigation A field investigations was conducted on March 7, 2014. The weather was sunny, clear and approximately 60 degrees. Cedar Avenue S drains south though an existing storm drain system and outlets to a Class 5 stream south of the proposed project. The 2:1 slope constructed in 2010 as part of the construction of the WSDOT I-405, I-5 to SR 169 Stage 2 Corridor Widening Project drains west to a ditch at the bottom of the slope. The flatter portion of the site drains south to an existing onsite ditch north of the WSDOT access road where it has its confluence with the ditch at the bottom of the 2:1 slope. The two ditches drain to a 54-inch catch basin with a birdcage into a piped system continuing west for 250 feet down the side slope on the east side of I-405 to a drainage structure in the shoulder. Drainage continues north for approximately 2,800 feet through a series of catch basins and pipes in I-405 to a WSDOT Spill Containment Pond located west of I-405 and east of S 3rd Street. Level 2 Downstream Analysis A technical memorandum entitled Drainage Design for the WSDOT Exchange Property, revised on July 7, 2010 was completed as part of the I-405 widening and has been included in Appendix E. The WEP is located in the Cedar River Threshold Discharge Area which is a flow control exempt basin according to the WSDOT Highway Runoff Manual (2008). The technical memo summarizes the analysis completed to assess the downstream capacity of the existing WSDOT drainage system and to determine if the increased flowrate due to the land cover of the WSDOT Exchange Property (WEP) going from second growth forest to grass can be conveyed by the existing system. The conveyance analysis determined that WSDOT’s existing downstream system of the proposed project can safely convey the 100-year undetained flow of the WEP (or the project site) with a land cover of grass. This project is providing Level 2 flow control modeling the pre-developed conditions as completely forested, so the downstream system including the existing WSDOT Spill Containment Pond and conveyance pipes will have adequate capacity for the project’s stormwater. Core Design, Inc. MERLINO SHORT PLAT Page 7 1 – Looking west from the west side of Cedar Avenue S 2 – Looking north from the east property line 3 – Looking west from the top of the 2:1 slope 4 – Looking south west at an existing rock lined ditch on the north side of the WSDOT access road Core Design, Inc. MERLINO SHORT PLAT Page 8 5 – Looking south west at the existing WSDOT access road 6 – Looking north at a ditch at the toe of the 1.75:1 slope 7 – Birdcage structure at the downstream end of the ditch in photo 6 8 – Looking northwest at a grass lined ditch flowing down to I-405 Core Design, Inc. MERLINO SHORT PLAT Page 9 9 – Catch basin on the east side of I-405 10 – Looking south on the west side of Cedar Ave S at the driveway for the Cedar Crest Condos Core Design, Inc. MERLINO SHORT PLAT Page 10 3.4 Mitigation of Existing and Potential Problems Downstream Drainage Problems Requiring Special Attention Type 1 – Conveyance System Nuisance Problems There are no known, reported or observed current downstream conveyance nuisance problems. Type 2 – Severe Erosion Problems There are no known, reported or observed current downstream severe erosion problems Type 3-Severe Flooding Problems There are no known, reported or observed current downstream severe flooding problems. Department of Ecology 303d Listings Type 1 – Bacteria Problems There are no known or reported bacteria problems. Type 2 – Dissolved Oxygen (DO) Problems There are no known or reported dissolved oxygen problems. Type 3 – Temperature Problems There are no known or reported temperature problems. Type 4 – Metals Problems There are no known or reported downstream metals problems. Type 5 – Phosphorous Problems There are no known or reported downstream phosphorous problems. Type 6 – Turbidity Problems There are no known or reported downstream turbidity problems. Type 7 – High pH Problems There are no known or reported high pH problems. Drainage Adjustments There is no drainage adjustment proposed for this project. Core Design, Inc. MERLINO SHORT PLAT Page 11 4 FLOW CONTROL AND WATER QUALITY DESIGN 4.1 Existing Site Hydrology The project site is approximately 1.60 acres in size and is currently covered in grass. Cedar Avenue S drains south at approximately 2.5% though an existing storm drain system and outlets to a Class 5 stream south of the proposed project. The 2:1 slope constructed in 2010 as part of the construction of the WSDOT I-405, I-5 to SR 169 Stage 2 Corridor Widening Project drains west to a ditch flowing south on the west boundary of the site. The flatter portion of the site drains south to an existing onsite ditch north of the WSDOT access road where it has its confluence with the ditch on the west boundary. See Table 4-1 below and Figure 4-1: Existing Conditions. A site Soils Map is included in Appendix B and the KCRTS Hydrologic Soils Group table (Table 3.2.2.B) is included in Appendix C. There are approximately 0.10 acres of existing impervious area from Cedar Avenue S which will enter the proposed drainage system due to the frontage improvements. This area has been modeled as impervious in the pre-developed conditions. Historic site conditions are assumed for all existing onsite area of 1.50 acres per Section 1.2.3.1 of the 2009 KCSWDM (page 1-43) and are modeled as Till Forest. Table 4-1 Existing Conditions Areas GROUND COVER AREA (acres) Till-Forest 1.50 Impervious 0.10 TOTAL 1.60 The peak flow rates for the pre-developed conditions as determined by KCRTS (one hour time steps) are shown below. A regional scale factor of ST 1.0 was used as determined by Figure 3.2.2.A in Appendix C. Flow Frequency Analysis Time Series File:04139m_pre.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.116 2 2/09/01 15:00 0.175 1 100.00 0.990 0.054 7 1/05/02 16:00 0.116 2 25.00 0.960 0.105 3 2/28/03 3:00 0.105 3 10.00 0.900 0.035 8 8/26/04 2:00 0.103 4 5.00 0.800 0.063 6 1/05/05 8:00 0.094 5 3.00 0.667 0.103 4 1/18/06 16:00 0.063 6 2.00 0.500 0.094 5 11/24/06 4:00 0.054 7 1.30 0.231 0.175 1 1/09/08 9:00 0.035 8 1.10 0.091 Computed Peaks 0.156 50.00 0.980 Core Design, Inc. MERLINO SHORT PLAT Page 12 4.2 Developed Site Hydrology The site was mass graded as part of the I-405 project, so there will be no clearing and minimal grading to construct seven single-family lots, stormwater vault and associated utilities. All of the lots will drain to Cedar Avenue S. Half street frontage improvements on Cedar Avenue S will be completed to provide 13.5 feet of pavement from the right of way centerline, curb and gutter, an 8-foot planter and a 5-foot sidewalk. The developed condition areas are summarized in Table 4-2 and Figure 4-2 Developed Conditions Map. Table 4-2 Developed Condition Areas GROUND COVER AREA (acres) Till-Grass 0.65 Impervious 0.95 TOTAL 1.60 The undetained peak flow rates for the developed conditions as determined by KCRTS (one hour time steps) are shown below. Flow Frequency Analysis Time Series File:04139m_dev.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.289 6 2/09/01 2:00 0.586 1 100.00 0.990 0.232 8 1/05/02 16:00 0.362 2 25.00 0.960 0.348 3 2/27/03 7:00 0.348 3 10.00 0.900 0.249 7 8/26/04 2:00 0.306 4 5.00 0.800 0.300 5 10/28/04 16:00 0.300 5 3.00 0.667 0.306 4 1/18/06 16:00 0.289 6 2.00 0.500 0.362 2 10/26/06 0:00 0.249 7 1.30 0.231 0.586 1 1/09/08 6:00 0.232 8 1.10 0.091 Computed Peaks 0.511 50.00 0.980 Core Design, Inc. MERLINO SHORT PLAT Page 15 4.3 Performance Standards All stormwater facilities will be designed in accordance with the 2009 KCSWDM with the COR Amendments, with Flow Control Duration Standard Matching Forested Site Conditions. The proposed water quality treatment system will meet requirements from the Basic Water Quality Protection Menu. Flow Control: Duration Standard Matching Forested Site Conditions The Flow Control Duration Standard Matching Forested Site Conditions requires maintaining the durations of developed flows at their pre-development levels for all flows greater than one-half of the 2-year peak flow through the 50-year peak flow. The pre-development peak flow rates for the 2-year and 10-year runoff events must also be maintained under this requirement. Conveyance Capacity The proposed conveyance system will be designed with sufficient capacity to convey and contain the 25- year peak flow as determined by the Rational Method. It will also be verified that the 100-year peak flow will not create or aggravate a severe flooding or erosion problem per Section 1.2.2. Water Quality: Basic Water Quality Menu The Basic Water Quality Menu includes one pollutant removal targets: • Total Suspended Solids = 80% reduction The Basic Water Quality Menu, described in detail in Section 6.1.1 of the 2009 KCSWDM (page 6-4), provides eight options to meet the pollutant removal targets listed above. • Option 1: Biofiltration Swale • Option 2: Filter Strip • Option 3: Wetpond • Option 4: Wetvault • Option 5: Stormwater Wetland • Option 6: Combined Detention and Wetpool Facilities • Option 7: Sand Filter • Option 8: Stormfilter The project proposes to apply Option 4, a Wetvault. More detailed discussion and preliminary sizing calculations of the flow control and water quality treatment facility proposed for this project follows later in this section. 4.4 Flow Control System Calculation of Lot Impervious Area The impervious area per lot applied to the developed basin time series file was determined using the criteria in the 2009 KCSWDM page 3-27 and page 3-2 of the COR Amendments. The proposed development is urban residential. The site zoned R-8. The minimum impervious area per lot per the 2009 KCSWDM (page 3-27) would either be 4,000 square feet or the maximum impervious area as stated in Section 3.2.2.1 of the COR SWDMA, whichever is less. The maximum impervious surface allowed in the R-8, zone in the City of Renton, is 75%. Core Design, Inc. MERLINO SHORT PLAT Page 16 Flow Control BMPs/Individual Lot BMPs This project will not be served by an infiltration facility and therefore must apply flow control BMPs to supplement the flow mitigation provided by the detention vault. This project has lots less than 22,000 square feet so it is subject to the small lot BMP requirements. Full dispersion and full infiltration of the roof runoff is not feasible due to the steep slopes and landslide hazard area, so one or more of the following BMPs must be applied to an impervious area equal to at least 10% of the lot for lots up to 11,000 square feet and 20% of the lot for lots between 11,000 and 22,000 square feet. • Limited Infiltration • Basic Dispersion • Rain Garden • Permeable Pavement • Rainwater Harvesting • Vegetated Roof • Reduced Impervious Surface Credit • Native Growth Retention Credit This project will be implementing either basic dispersion (depending on the space available) or a reduced impervious surface credit to meet the requirements for individual lot BMPs. The individual lot BMP will be selected during the building permit process. If a reduced impervious credit is selected a covenant will be placed on each lot indicating that the maximum impervious area will be equal to the Reduced Impervious Area shown below in Table 4-3, which is 4,000 square feet minus the individual lot BMP area. As a conservative measure, the vault has been sized with an effective impervious area of 0.95 ac and a pervious area of 0.65 ac which assumes basic dispersion as the individual lot BMP. Table 4-3 Onsite Areas Lot Total Area (sf) Land Use Area Impervious (sf) Effective Impervious (sf) New Pervious Surface (sf) Individual Lot BMP (sf) Reduced Impervious (sf) 1 7,112 4,000 3,644 3,468 711 3,289 2 6,709 4,000 3,665 3,044 671 3,329 3 6,652 4,000 3,667 2,985 665 3,335 4 6,595 4,000 3,670 2,925 660 3,341 5 7,080 4,000 3,646 3,434 708 3,292 6 7,013 4,000 3,649 3,364 701 3,299 7 7,989 4,000 3,601 4,388 799 3,201 ROW 14,307 9,620 9,620 4,687 Offsite 6,175 6,175 6,175 0 TOTAL to Vault 69,632 41,338 28,295 TOTAL to Vault (ac) 1.60 0.95 0.65 Notes: 1. Impervious Area = 4,000 sf or 75% of the Total Area, whichever is less 2. Effective Impervious Area = Impervious Area – (50%)Individual Lot BMP (assuming basic dispersion) 3. New Pervious Surface = Total Area – Effective Impervious Area 4. Individual Lot BMP Area = 10% of Total Area (This area would not drain to the vault.) Core Design, Inc. MERLINO SHORT PLAT Page 17 5. Reduced Impervious Area = Impervious – Individual Lot BMP area (Max impervious if Reduced Impervious Area credit taken) Bypass Area Due to topographic constraints about 0.04 acres southwest of the cul-de-sac will not drain to the detention vault, so an equivalent area of existing pavement will be treated and detained in lieu of this area. Detention Pond Modeling The proposed detention vault will be located at the south end of Cedar Avenue S with 7 feet of live storage. KCRTS Vault Calculation Type of Facility: Detention Vault Facility Length: 56.00 ft Facility Width: 40.00 ft Facility Area: 2240. sq. ft Effective Storage Depth: 7.00 ft Stage 0 Elevation: 216.00 ft Storage Volume: 15680. cu. ft Riser Head: 7.00 ft Riser Diameter: 12.00 inches Number of orifices: 3 Full Head Pipe Orifice # Height Diameter Discharge Diameter (ft) (in) (CFS) (in) 1 0.00 0.75 0.040 2 4.00 0.81 0.031 4.0 3 5.10 0.94 0.033 4.0 Top Notch Weir: None Outflow Rating Curve: None The proposed detention vault includes a three orifice control structure. The first orifice is 3/4 inches in diameter and is at the bottom of the riser. The second orifice is 4.0 feet above the live/dead interface elevation and is 13/16 inches in diameter and the third orifice is 5.1 feet above the live/dead interface and 15/16 inch in diameter. The proposed vault will require a storage volume of 15,680 cubic feet with 7.0 feet of live storage. Hyd Inflow Outflow Peak Storage Target Calc Stage Elev (Cu-Ft) (Ac-Ft) 1 0.59 ******* 0.42 7.10 223.10 15906. 0.365 2 0.29 ******* 0.10 6.94 222.94 15535. 0.357 3 0.29 0.10 0.09 6.09 222.09 13650. 0.313 4 0.35 ******* 0.07 5.46 221.46 12230. 0.281 5 0.31 ******* 0.07 5.32 221.32 11912. 0.273 6 0.18 0.06 0.04 4.10 220.10 9189. 0.211 7 0.23 ******* 0.03 3.31 219.31 7414. 0.170 8 0.25 ******* 0.02 2.52 218.52 5637. 0.129 The outflow from the detention vault control structure releases 0.04 cfs for the 2-year event and 0.09 cfs for the 10-year event. These release rates are below the pre-developed peak flows of 0.06 cfs and 0.10 cfs for the 2-year and 10-year rates, respectively. Therefore, the proposed facility meets the peak release rate requirements. Core Design, Inc. MERLINO SHORT PLAT Page 18 The flow duration comparison analysis results for the provided detention vault are shown below. There is less than 10% excursion between the 2-year and 50-year release rate and the curve is entirely under the target curve for the required range of 50% 2-year to 2-year. Therefore, the proposed detention facility meets the flow duration requirement. Duration Comparison Anaylsis Base File: 04139m_pre.tsf New File: rdout.tsf Cutoff Units: Discharge in CFS -----Fraction of Time----- ---------Check of Tolerance------- Cutoff Base New %Change Probability Base New %Change 0.031 | 0.61E-02 0.52E-02 -14.4 | 0.61E-02 0.031 0.030 -3.5 0.037 | 0.48E-02 0.46E-02 -3.8 | 0.48E-02 0.037 0.036 -3.0 0.043 | 0.37E-02 0.33E-02 -8.5 | 0.37E-02 0.043 0.041 -5.1 0.049 | 0.27E-02 0.25E-02 -7.8 | 0.27E-02 0.049 0.048 -2.9 0.055 | 0.20E-02 0.16E-02 -20.7 | 0.20E-02 0.055 0.052 -6.7 0.062 | 0.14E-02 0.14E-02 -2.3 | 0.14E-02 0.062 0.061 -0.6 0.068 | 0.99E-03 0.10E-02 4.9 | 0.99E-03 0.068 0.068 0.8 0.074 | 0.80E-03 0.80E-03 0.0 | 0.80E-03 0.074 0.074 0.8 0.080 | 0.55E-03 0.59E-03 5.9 | 0.55E-03 0.080 0.080 0.9 0.086 | 0.38E-03 0.34E-03 -8.7 | 0.38E-03 0.086 0.085 -0.9 0.092 | 0.15E-03 0.23E-03 55.6 | 0.15E-03 0.092 0.097 6.4 0.098 | 0.98E-04 0.11E-03 16.7 | 0.98E-04 0.098 0.100 1.9 0.104 | 0.65E-04 0.00E+00 -100.0 | 0.65E-04 0.104 0.101 -2.2 0.110 | 0.16E-04 0.00E+00 -100.0 | 0.16E-04 0.110 0.103 -5.8 Maximum positive excursion = 0.006 cfs ( 6.4%) occurring at 0.092 cfs on the Base Data:04139m_pre.tsf and at 0.097 cfs on the New Data:rdout.tsf Maximum negative excursion = 0.004 cfs (-10.8%) occurring at 0.035 cfs on the Base Data:04139m_pre.tsf and at 0.031 cfs on the New Data:rdout.tsf 4.5 Water Quality Calculations Basic Wetvault A Basic Wetvault includes a permanent wetpool that allows for the removal of 80% of Total Suspended Solids. Section 6.4.1.1 outlines a 4-step process to calculate the required wetpool volume. Step 1: Identify required wetpool volume factor (f) A basic wetpond requires a volume factor of 3.0. Step 2: Determine rainfall (R) for the mean annual storm Figure 6.4.1.A (page 6-71 in the 2009 KCSWDM, included below and in Appendix C) is used to determine the rainfall, in inches, for the mean annual storm. The rainfall is then converted into feet for use in Equation 6-13 (shown below). Core Design, Inc. MERLINO SHORT PLAT Page 19 The mean annual storm rainfall for this project site is 0.47” as noted on the project-specific Figure 6.4.1.A included in Appendix C. Step 3: Calculate runoff from the mean annual storm (Vr) for the developed site The land cover types and associated areas for each in the developed project site are used to calculate the amount of rainfall, in cubic feet, that runs off each land cover type. Coefficients specific to the four U.S. Department of Agriculture soil survey cover categories are weighted by the drainage areas and then multiplied by the rainfall, R, from Step 2. Equation 6-13 𝑉𝑉𝑟𝑟=(0.9𝐴𝐴𝑖𝑖+0.25𝐴𝐴𝑡𝑡𝑡𝑡+0.10𝐴𝐴𝑡𝑡𝑡𝑡+0.01𝐴𝐴𝑜𝑜)𝑥𝑥(𝑅𝑅) where Vr = calculated volume of runoff from mean annual storm Ai = area of impervious surface (41,338 sf) Atg = area of till soil covered with grass (28,295 sf) Atf = area of till soil covered with forest (0 sf) Ao = area of outwash soil covered with grass or forest (0 sf) R = rainfall from mean annual storm (0.039 ft) Using Equation 6-13 above and the land cover areas in the developed basin calculations, the volume of runoff from the mean annual storm is 1,734 cubic feet. Step 4: Calculate wetpool volume (Vb) The numbers / results from the previous steps are used in Equation 6-14 (shown below) to calculate the required wetpool volume. Equation 6-14 𝑉𝑉𝑏𝑏=𝑓𝑓𝑉𝑉𝑟𝑟 where Vb = calculated required minimum wetpool volume (5,203 cf) f = volume factor from Step 1 (3.0) Vr = volume of runoff from mean annual storm (1,734 cf) Using Equation 6-14 above and the results from the previous steps, the required minimum wetpool volume, Vb is 5,203cubic feet. The proposed wetpool yields a volume of 5,440 cubic feet. Core Design, Inc. MERLINO SHORT PLAT Page 20 Core Design, Inc. MERLINO SHORT PLAT Page 21 5 CONVEYANCE SYSTEM ANALYSIS AND DESIGN The onsite conveyance system has been analyzed using a backwater spreadsheet per Figure 4.2.1.B and the requirements described in Chapter 4 of the 2009 KCSWDM. The spreadsheet applies the Manning equation in the Backwater Analysis Method described in Section 4.2.1.2 (page 4-21) of the 2009 KCSWDM. Refer to Figure 5-1: Catch Basin Tributary Areas located at the end of this Section to aid in the following discussion and the conveyance calculations are included in Appendix D. 5.1 Rational Method The conveyance system has been designed to provide sufficient capacity to convey and contain, at a minimum, the 100-year peak developed condition flow as determined by the Rational Method. This flow is divided by the total project area to determine the per acre flowrate at the 100-year design storm. Section 3.2.1 of the 2009 KCSWDM outlines the process for determining QR for the project site area. The peak 100-year flow is determined by the following equation: Equation 3-1 𝑄𝑄𝑅𝑅=𝐶𝐶𝐶𝐶𝐼𝐼𝑅𝑅𝐴𝐴 Where: QR = peak flow for a storm of return frequency R (3.04 cfs, Equation 3-1) CC = composite estimated runoff coefficient (0.64, see “C” Value Calculation below) IR = peak rainfall intensity for a storm of return frequency R (3.19 in/hr, see “IR” Peak Rainfall Intensity Calculation below) A = drainage subbasin area (1.60 acres) “C” Value Calculation The allowable runoff coefficients to be used in the Rational Method are shown in Table 3.2.1.A of the 2009 KCSWDM (page 3-13) by type of land cover. The composite “C” value, CC, is determined by the following equation: Equation 3-2 𝐶𝐶𝐶𝐶=(𝐶𝐶1𝐴𝐴1 +𝐶𝐶2𝐴𝐴2 +⋯+𝐶𝐶𝑛𝑛𝐴𝐴𝑛𝑛)/𝐴𝐴𝑇𝑇 Where: AT = total area (1.60 acres) A1,2,…n = areas of land cover types (acres, see table below) C1, 2,…n = runoff coefficients for each land cover type ( see table below) Table 5-1 Composite “C” Value Cover Type C A Lawns / landscaping 0.25 0.65 Pavement and roofs 0.90 0.95 CC = 0.64 AT = 1.60 “IR” Peak Rainfall Intensity Calculation The peak rainfall intensity, IR, for the specified design storm of return frequency R (100-year) is determined using the following equations: Equation 3-3 𝐼𝐼𝑅𝑅=(𝑃𝑃𝑅𝑅)(𝑖𝑖𝑅𝑅) Equation 3-4 𝑖𝑖𝑅𝑅=(𝑎𝑎𝑅𝑅)(𝑇𝑇𝑐𝑐)−𝑏𝑏𝑅𝑅 Where: IR = peak rainfall intensity (3.19 in/hr, Equation 3-3) Core Design, Inc. MERLINO SHORT PLAT Page 22 PR = total precipitation at the project site for the 24-hour, 100-year storm (3.9 in, Figure 3.2.1.C, page 3-17) iR = unit peak rainfall intensity factor (0.82 in/hr, Equation 3-4) Tc = time of concentration (6.3 minutes, see “Tc” Time of Concentration Calculation below) aR, bR = Table 3.2.1.B (100-year) adjustment coefficients 2.61 and 0.63 respectively) “Tc” Time of Concentration Calculation The time of concentration is defined as “…the time it takes runoff to travel overland (from the onset of precipitation) from the most hydraulically distant location in the drainage basin to the point of discharge.” The value for time of concentration, Tc, used in equation 3-4 above is the sum total of the time of concentration for each overland flowpath segment, Tt. The equations for calculating Tc, therefore, are as follows: Equation 3-5 𝑇𝑇𝑐𝑐=𝑇𝑇1 +𝑇𝑇2 +⋯+𝑇𝑇𝑛𝑛 Equation 3-6 𝑇𝑇1,2,…𝑛𝑛=𝐿𝐿60𝑉𝑉 Where: T1, 2,…n = travel time (6.3 minutes, see calculation and discussion below) L = distance of flow across a given segment V = average velocity across the land cover =𝑘𝑘𝑅𝑅�𝑠𝑠0) kR = time of concentration velocity factor (per Table 3.2.1.C, page 3-13) s0 = slope of flowpath However, due to the urban nature of this project, the minimum Tc of 6.3 minutes (per Page 3-12 in the 2009 KCSWDM) was used and the actual time of concentration was not calculated. Peak Flow per Acre The QR calculation below determines the flow per acre to be applied to the areas tributary to each onsite catch basin. QR/acre = 3.27 cfs/1.60 acres = 2.04 cfs/acre Onsite Catch Basin Tributary Areas & Flows The 2.04 cfs/acre was applied to the tributary areas to determine the peak flow to each catch basin. The areas and corresponding catchment flow rates are graphically represented on Figure 5-1: Tributary Catch Basin Areas Table 5-2 Tributary Flows CB Incremental Area (ac) Q100 CB4 0.80 1.63 CB3 0.63 1.29 CB7 0.16 0.33 5.2 Backwater Analysis The onsite conveyance system is designed with the tailwater elevation set at the maximum water surface elevation of the proposed vault. All conveyance systems are designed to safely convey the 100-year Core Design, Inc. MERLINO SHORT PLAT Page 23 storm event. Core Requirement #4 in the 2009 KCSWDM requires storm pipes to safely convey the 25- year storm. Table 5-3 below shows the calculated freeboard at each catch basin analyzed. The backwater spreadsheet is included in Appendix D. Table 5-3 Catch Basin Freeboard (at 100-yr event) CB HGL Elevation (feet) Rim Elevation (feet) Freeboard (feet) CB1 223.02 227.81 4.80 CB2 223.59 228.98 5.40 CB3 224.83 230.00 5.19 CB4 228.07 232.91 4.89 CB5 223.03 227.50 4.48 CB6 223.03 224.90 1.87 Core Design, Inc. MERLINO SHORT PLAT Page 24 Core Design, Inc. MERLINO SHORT PLAT Page 27 6 SPECIAL REPORTS AND STUDIES The following special reports and studies have been prepared for this project and are included in Appendix E of this report. Ø Drainage Design for the WSDOT Exchange Property I-405 to SR 169 Stage 2 Widening and SR 515 Interchange Project July 29, 2009 Revised August 13, 2009, July 7, 2010 Prepared By: I-405 Corridor Design-Builders Ø Geological Engineering Services Coal Mine Hazard Assessment Merlino Short Plat Proposed 7-Lot Residential Development Renton, Washington April 23, 2014 Prepared By: Icicle Creek Engineers, Inc. Ø Geotechnical Engineering Services Critical Areas Report Merlino Short Plat Proposed 7-Lot Residential Development Renton, Washington April 23, 2014 Prepared By: Icicle Creek Engineers, Inc. Core Design, Inc. MERLINO SHORT PLAT Page 28 THIS PAGE INTENTIONALLY LEFT BLANK Core Design, Inc. MERLINO SHORT PLAT Page 29 7 OTHER PERMITS Ø NPDES Permit Ø Building Permits Ø ROW Use Permit Core Design, Inc. MERLINO SHORT PLAT Page 30 THIS PAGE INTENTIONALLY LEFT BLANK Core Design, Inc. MERLINO SHORT PLAT Page 31 8 ESC ANALYSIS AND DESIGN The site will utilize Appendix D of the 2009 KCSWDM for the erosion and sedimentation control design to reduce the discharge of sediment-laden runoff from the site. Clearing limits will be established prior to any earthwork on the project site. Perimeter protection will be provided by silt fencing along the entire perimeter of the site to limit the downstream transport of sediment to streams, wetlands and neighboring properties. Dust control, if required, will be provided by a water truck. A Certified Erosion and Sediment Control Lead inspector will be present onsite during earthwork activities. The inspector shall determine frequency of watering of the project site and will authorize and direct any additional erosion and sediment control measures as needed during all construction activities. The plan will be comprised of temporary measures (filter fabric protection, silt fence, interceptor swales, etc.) as well as permanent measures (detention vault, hydroseeding, etc.). In general, construction activities will be sequenced such that the permanent detention/water quality vault will be constructed and used for temporary erosion and sedimentation control. Runoff from the site will sheet flow across cleared areas into temporary interceptor swales and into temporary pipes that discharge into the permanent vault or into the permanent conveyance system, when installed. Although the permanent detention vault will be used as the TESC pond for the project, the minimum TESC pond area, dewatering orifice diameter, and emergency spillway length are calculated below and compared to the proposed detention vault to verify adequate TESC functionality. The TESC pond area was calculated for the project site using the 10-year storm event with the potential of work during the wet season (October 1 to April 30). Per Section D.3.5.2 of the 2009 KCSWDM, the KCRTS 10-year, 15- minute time step developed condition peak flow rate used for TESC pond area sizing is Q10 = 0.64 cfs. Flow Frequency Analysis Time Series File:04139m_dev15.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.452 6 8/27/01 18:00 1.45 1 100.00 0.990 0.327 8 1/05/02 15:00 0.999 2 25.00 0.960 0.999 2 12/08/02 17:15 0.635 3 10.00 0.900 0.364 7 8/23/04 14:30 0.591 4 5.00 0.800 0.591 4 11/17/04 5:00 0.548 5 3.00 0.667 0.548 5 10/27/05 10:45 0.452 6 2.00 0.500 0.635 3 10/25/06 22:45 0.364 7 1.30 0.231 1.45 1 1/09/08 6:30 0.327 8 1.10 0.091 Computed Peaks 1.30 50.00 0.980 TESC Pond Surface Area Calculation TESC Pond minimum surface area, SA, is determined by the following equation: SA = 2080 sf/cfs * (Total Q10-developed) (page D-47, 2009 KCSWDM) Where: SA = minimum TESC pond surface area (sf) Q10-developed = 10-year developed, 15-minute, peak flow (0.64 cfs) SAmin = 1,331 sf Core Design, Inc. MERLINO SHORT PLAT Page 32 The design surface area of the proposed detention vault is approximately 2,240 square feet which is more than enough surface area to provide adequate erosion and sedimentation control. Principal Spillway (Riser Pipe) The TESC pond (permanent detention vault) is designed to function with 0.5 feet (6 inches) of head. The riser pipe must pass the developed condition 10-year peak flow using KCRTS 15-minute time steps. Using Figure 5.3.4.H (page 5-47 2009 KCSWDM) the minimum riser pipe diameter is 10 inches. The proposed permanent detention vault riser pipe diameter is 12 inches, which is more than enough to provide adequate erosion and sedimentation control. Emergency Overflow Spillway The TESC pond must safely convey the developed condition 100-year KCRTS 15-minute peak flow. Since the permanent detention vault is to be used as the TESC pond and it has been sized to provide Flood Problem Flow Control with a 100-year release rate at or below the existing 100-year flow rate, it is adequate to provide appropriate erosion and sedimentation control. Dewatering Orifice The dewatering orifice diameter must be at least 1 inch and is sized using a three step process, outlined on page D-48 of the 2009 KCSWDM. 1. Determine the required area of the orifice A modified version of the discharge equation for a vertical orifice is used to determine the required orifice surface area, as follows: 𝐴𝐴𝑂𝑂=𝐴𝐴𝑆𝑆(2ℎ)0.50.6𝑥𝑥3600𝑥𝑥𝑇𝑇𝑡𝑡0.5 Where: AO = orifice area (sf) AS = required pond surface area (1,331 sf) h = head of water above orifice (3.5 ft, minimum per Section D.3.5.2 2009 KCSWDM) T = dewatering time (24 hours, page D-48 2009 KCSWDM) g = acceleration due to gravity (32.2 ft/s2) AO = 0.012 sf 2. Convert the required surface area to the required diameter, D (inches) The required surface area of the orifice is converted to the required diameter, D, using a basic equation for the area of a circular orifice, as follows: 𝐷𝐷=24𝑥𝑥�𝐴𝐴𝑂𝑂𝜋𝜋 D = 1.48” = 1.5” inches 3. Determine the size of the vertical, perforated tubing connected to the dewatering orifice Core Design, Inc. MERLINO SHORT PLAT Page 33 The minimum diameter for the perforated tubing connected to the dewatering orifice is 2 inches larger than the orifice. Therefore, the minimum tubing diameter = 3 1/2 inches, or a design diameter of 6 inches. Core Design, Inc. MERLINO SHORT PLAT Page 34 THIS PAGE INTENTIONALLY LEFT BLANK Core Design, Inc. MERLINO SHORT PLAT Page 35 9 BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT Bond Quantities A Site Improvement Bond Quantity Worksheet has been provided at the end of this section. Facility Summaries Not applicable. Declaration of Covenant Not applicable. Core Design, Inc. MERLINO SHORT PLAT Page 36 THIS PAGE INTENTIONALLY LEFT BLANK Site Improvement Bond Quantity Worksheet Original bond computations prepared by:Name: Date:PE Registration Number: Tel/ #:Firm Name:Address: Project No.:Stabilization/Erosion Sediment Control (ESC) (A) $Existing Right-of-Way Improvements (B) $Future Public Road Improvements & Drainage Facilities (C) $ Private Improvements (D) $Construction Bond* Amount (A+B+C-D) = TOTAL(T) $Minimum bond* amount is $1000.Maintenance/Defect Bond* Total $ $68,686.72(B+C) x 0.20 =NAME OF PERSON PREPARING BOND* REDUCTION: Sheri Murata Date: 2/23/2015* NOTE: The word "bond" as used in this document means any financial guarantee acceptable to the City of Renton.** NOTE: All prices include labor, equipment, materials, overhead and profit. Prices are from RS Means data adjusted for the Seattle area or from local sources if not included in the RS Means database.REQUIRED BOND* AMOUNTS ARE SUBJECT TO REVIEW AND MODIFICATION BY RDSDPage 1 of 115,575.33105,619.19237,814.3858,138.96300,869.95PUBLIC ROAD & DRAINAGEMAINTENANCE/DEFECT BOND*,**2/23/2015425-885-787704139MSheri Murata41846Core Design, Inc.14711 Ne 29th Place, Suite 101 Bellevue, WA 98007ROAD IMPROVEMENTS & DRAINAGE FACILITIES FINANCIAL GUARANTEE REQUIREMENTSPERFORMANCE BOND*,**AMOUNTREF 8-H BOND QUANTITY WORKSHEET.XLSUnity proces updates: 2/12/02Version: 4/22/02Report Date: 1/19/10 Site Improvement Bond Quantity Worksheet Unit Price UnitGENERAL ITEMS No.Backfill & Compaction- embankment GI - 1 $ 5.62CY 0.00 0.00 0.00 0.00Backfill & Compaction- trench GI - 2 $ 8.53CY 0.00 0.00 0.00 0.00Clear/Remove Brush, by hand GI - 3 $ 0.36SY 0.00 0.00 0.00 0.00Clearing/Grubbing/Tree Removal GI - 4 $ 8,876.16 Acre0.00 0.00 0.00 0.00Excavation - bulk GI - 5 $ 1.50 CY 0.00 0.00 0.00 0.00Excavation - Trench GI - 6 $ 4.06 CY 260 1055.60 0.00 130 527.80 0.00Fencing, cedar, 6' high GI - 7 $ 18.55 LF 0.00 0.00 625 11593.75 0.00Fencing, chain link, vinyl coated, 6' highGI - 8 $ 13.44 LF 0.00 0.00 0.00 0.00Fencing, chain link, gate, vinyl coated, 20 GI - 9 $ 1,271.81 Each 0.000.00 0.00 0.00Fencing, split rail, 3' high GI - 10 $ 12.12 LF 0.00 0.00 85 1030.20 0.00Fill & compact - common barrow GI - 11$ 22.57 CY0.00 0.00 0.00 0.00Fill & compact - gravel base GI - 12$ 25.48 CY0.00 0.00 0.00 0.00Fill & compact - screened topsoil GI - 13$ 37.85 CY0.00 0.00 0.00 0.00Gabion, 12" deep, stone filled mesh GI - 14 $ 54.31SY 0.00 0.00 0.00 0.00Gabion, 18" deep, stone filled mesh GI - 15 $ 74.85SY 0.00 0.00 0.00 0.00Gabion, 36" deep, stone filled mesh GI - 16 $ 132.48SY 0.00 0.00 0.00 0.00Grading, fine, by hand GI - 17 $ 2.02 SY0.00 0.00 0.00 0.00Grading, fine, with grader GI - 18 $ 0.95 SY 0.00 0.00 7744 7356.80 0.00Monuments, 3' long GI - 19 $ 135.13 Each 0.00 0.00 0.00 0.00Sensitive Areas Sign GI - 20 $ 2.88 Each 0.00 0.00 0.00 0.00Sodding, 1" deep, sloped ground GI - 21 $ 7.46SY 0.00 0.00 0.00 0.00Surveying, line & grade GI - 22$ 788.26 Day 0.00 0.00 0.00 0.00Surveying, lot location/lines GI - 23$ 1,556.64 Acre 0.000.00 1.6 2490.62 0.00Traffic control crew ( 2 flaggers ) GI - 24$ 85.18 HR 12 1022.16 0.00 0.00 0.00Trail, 4" chipped wood GI - 25 $ 7.59 SY0.00 0.00 0.00 0.00Trail, 4" crushed cinder GI - 26 $ 8.33 SY0.00 0.00 0.00 0.00Trail, 4" top course GI - 27 $ 8.19 SY0.00 0.00 0.00 0.00Wall, retaining, concrete GI - 28 $ 44.16 SF 0.00 0.00 285 12585.60 0.00Wall, rockery GI - 29 $ 9.49 SF 0.00 0.00 0.00 0.00Page 2 of 7 SUBTOTAL $2,077.76 $0.00 $35,584.77 $0.00PrivateImprovementsQuantity Completed (Bond Reduction)*Quant. CompleteCostQuant. CostQuant. CostQuant. CostExistingRight-of-WayFuture PublicRoad Improvements& Drainage FacilitiesREF 8-H BOND QUANTITY WORKSHEET.XLSUnity proces updates: 2/12/02Version: 4/22/02Report Date: 1/19/10 Site Improvement Bond Quantity Worksheet Unit Price UnitROAD IMPROVEMENT No.AC Grinding, 4' wide machine < 1000sy RI - 1 $ 23.00SY 0.00 0.00 0.00 0.00AC Grinding, 4' wide machine 1000-2000 RI - 2 $ 5.75 SY 0.00 0.00 0.00 0.00AC Grinding, 4' wide machine > 2000sy RI - 3 $ 1.38 SY 0.00 0.00 0.00 0.00AC Removal/Disposal/Repair RI - 4 $ 41.14 SY 70028798.00 0.00 0.00 0.00Barricade, type I RI - 5 $ 30.03 LF 0.00 0.00 0.00 0.00Barricade, type III ( Permanent ) RI - 6 $ 45.05 LF 0.000.00 0.00 0.00Curb & Gutter, rolled RI - 7 $ 13.27 LF 0.00 0.00 0.00 0.00Curb & Gutter, vertical RI - 8 $ 9.69 LF 640 6201.60 0.00 0.00 0.00Curb and Gutter, demolition and disposal RI - 9 $ 13.58 LF 0.000.00 0.00 0.00Curb, extruded asphalt RI - 10 $ 2.44 LF 0.00 0.00 0.00 0.00Curb, extruded concrete RI - 11 $ 2.56 LF0.00 0.00 0.00 0.00Sawcut, asphalt, 3" depth RI - 12 $ 1.85 LF 650 1202.50 0.00 0.00 0.00Sawcut, concrete, per 1" depth RI - 13 $ 1.69 LF 650 1098.50 0.00 0.00 0.00Sealant, asphalt RI - 14 $ 0.99 LF 0.00 0.00 0.00 0.00Shoulder, AC, ( see AC road unit price ) RI - 15 $ - SYShoulder, gravel, 4" thick RI - 16 $ 7.53 SY0.00 0.00 0.00 0.00Sidewalk, 4" thick RI - 17 $ 30.52 SY 0.00 300 9156.00 0.00 0.00Sidewalk, 4" thick, demolition and disposaRI - $ 27.73 SY0.00 0.00 0.00 0.00Sidewalk, 5" thick RI - 19 $ 34.94 SY 0.00 0.00 0.00 0.00Sidewalk, 5" thick, demolition and disposaRI - $ 34.65 SY0.00 0.00 0.00 0.00Sign, handicap RI - 21 $ 85.28 Each 0.000.00 0.00 0.00Striping, per stall RI - 22 $ 5.82 Each0.00 0.00 0.00 0.00Striping, thermoplastic, ( for crosswalk ) RI - 23 $ 2.38 SF0.00 0.00 0.00 0.00Striping, 4" reflectorized line RI - 24 $ 0.25 LF 0.00 0.00 0.00 0.00Page 3 of 7 SUBTOTAL $37,300.60 $9,156.00 $0.00 $0.00ExistingRight-of-wayFuture PublicRoad Improvements& Drainage FacilitiesPrivateImprovementsBond Reduction*Quant. CompleteCostQuant. CostQuant. CostQuant. CostREF 8-H BOND QUANTITY WORKSHEET.XLSUnity proces updates: 2/12/02Version: 4/22/02Report Date: 1/19/10 Site Improvement Bond Quantity Worksheet Unit Price UnitFor KCRS '93, (additional 2.5" base) add: RS - 1 $ 3.60 SY 0.00 0.00 0.00 0.00AC Overlay, 1.5" AC RS - 2 $ 7.39 SY0.00 0.00 0.00 0.00AC Overlay, 2" AC RS - 3 $ 8.75 SY 1015 8881.25 460 4025.00 0.00 0.00AC Road, 2", 4" rock, First 2500 SY RS - 4 $ 17.24SY 0.00 0.00 0.00 0.00AC Road, 2", 4" rock, Qty. over 2500SY RS - 5 $ 13.36 SY 0.00 0.00 0.00 0.00AC Road, 3", 4" rock, First 2500 SY RS - 6 $ 19.69SY 0.00 0.00 0.00 0.00AC Road, 3", 4" rock, Qty. over 2500 SYRS - 7 $ 15.81 SY 0.00 0.00 0.00 0.00AC Road, 5", First 2500 SY RS - 8 $ 14.57 SY 1015 14788.55460 6702.20 0.00 0.00AC Road, 5", Qty. Over 2500 SY RS - 9 $ 13.94SY 0.00 0.00 0.00 0.00AC Road, 6", First 2500 SY RS - $ 16.76 SY0.00 0.00 0.00 0.00AC Road, 6", Qty. Over 2500 SY RS - $ 16.12 SY0.00 0.00 0.00 0.00Asphalt Treated Base, 4" thick RS - $ 9.21 SY 0.00 0.00 0.00 0.00Gravel Road, 4" rock, First 2500 SY RS - $ 11.41 SY 0.00 0.00 0.00 0.00Gravel Road, 4" rock, Qty. over 2500 SY RS - $ 7.53 SY 0.00 0.00 0.00 0.00PCC Road, 5", no base, over 2500 SY RS - $ 21.51SY 0.00 0.00 0.00 0.00PCC Road, 6", no base, over 2500 SY RS - $ 21.87 SY 0.00 0.00 0.00 0.00Thickened Edge RS - $ 6.89 LF 0.00 0.00 0.00 0.00Page 4 of 7 SUBTOTAL $23,669.80 $10,727.20 $0.00 $0.00ExistingRight-of-wayFuture PublicRoad Improvements& Drainage FacilitiesPrivateImprovementsBond Reduction*Quant. CompleteCostQuant. CostQuant. CostQuant. CostROAD SURFACING (4" Rock = 2.5 base & 1.5" top course) For '93 KCRS ( 6.5" Rock= 5" base & 1.5" top course)REF 8-H BOND QUANTITY WORKSHEET.XLSUnity proces updates: 2/12/02Version: 4/22/02Report Date: 1/19/10 Site Improvement Bond Quantity Worksheet Unit Price UnitAccess Road, R/D D - 1 $ 16.74 SY 0.00 0.00 0.00 0.00Bollards - fixed D - 2 $ 240.74 Each 0.000.00 0.00 0.00Bollards - removable D - 3 $ 452.34 Each 0.00 0.00 0.00 0.00CB Type I D - 4 $ 1,257.64Each 1 1257.64 0.00 0.00 0.00CB Type IL D - 5 $ 1,433.59 Each 0.00 0.00 0.00 0.00CB Type II, 48" diameter D - 6 $ 2,033.57 Each 3 6100.712 4067.14 0.00 0.00for additional depth over 4' D - 7 $ 436.52 FT 11.2 4889.02 0.00 0.00 0.00CB Type II, 54" diameter D - 8 $ 2,192.54 Each 0.00 0.00 0.00 0.00for additional depth over 4' D - 9 $ 486.53 FT 0.00 0.00 0.00 0.00CB Type II, 60" diameter D - 10$ 2,351.52 Each 0.00 0.00 0.00 0.00for additional depth over 4' D - 11$ 536.54 FT 0.00 0.00 0.00 0.00CB Type II, 72" diameter D - 12$ 3,212.64 Each 0.00 0.00 0.00 0.00for additional depth over 4' D - 13$ 692.21 FT 0.00 0.00 0.00 0.00Through-curb Inlet Framework (Add) D - 14 $ 366.09 Each0.00 0.00 0.00 0.00Cleanout, PVC, 4" D - 15 $ 130.55 Each 0.000.00 0.00 0.00Cleanout, PVC, 6" D - 16 $ 174.90 Each 0.00 0.00 7 1224.30 0.00Cleanout, PVC, 8" D - 17 $ 224.19 Each 0.000.00 0.00 0.00Culvert, PVC, 4" D - 18 $ 8.64 LF 0.00 0.00 0.00 0.00Culvert, PVC, 6" D - 19 $ 12.60 LF 0.000.00 0.00 0.00Culvert, PVC, 8" D - 20 $ 13.33 LF 0.00 0.00 0.00 0.00Culvert, PVC, 12" D - 21 $ 21.77 LF 0.000.00 0.00 0.00Culvert, CMP, 8" D - 22 $ 17.25 LF 0.00 0.00 0.00 0.00Culvert, CMP, 12" D - 23 $ 26.45 LF 0.00 0.00 0.00 0.00Culvert, CMP, 15" D - 24 $ 32.73 LF 0.00 0.00 0.00 0.00Culvert, CMP, 18" D - 25 $ 37.74 LF 0.00 0.00 0.00 0.00Culvert, CMP, 24" D - 26 $ 53.33 LF 0.00 0.00 0.00 0.00Culvert, CMP, 30" D - 27 $ 71.45 LF 0.00 0.00 0.00 0.00Culvert, CMP, 36" D - 28 $ 112.11 LF 0.000.00 0.00 0.00Culvert, CMP, 48" D - 29 $ 140.83 LF 0.000.00 0.00 0.00Culvert, CMP, 60" D - 30 $ 235.45 LF 0.000.00 0.00 0.00Culvert, CMP, 72" D - 31 $ 302.58 LF 0.000.00 0.00 0.00Page 5 of 7 SUBTOTAL $12,247.37 $4,067.14 $1,224.30 $0.00ExistingRight-of-wayFuture PublicRoad Improvements& Drainage FacilitiesPrivateImprovementsBond Reduction*Quant. CompleteCostQuant. CostQuant. CostQuant. CostDRAINAGE (CPP = Corrugated Plastic Pipe, N12 or Equivalent) For Culvert prices, Average of 4' cover was assumed. Assume perforated PVC is same price as solid pipe.* (CBs include frame and lid)REF 8-H BOND QUANTITY WORKSHEET.XLSUnity proces updates: 2/12/02Version: 4/22/02Report Date: 1/19/10 Site Improvement Bond Quantity Worksheet No. Unit Price Unit Quant. Cost Quant. Cost Quant. CostCulvert, Concrete, 8" D - 32 $ 21.02 LF 0.00 0.00 0.00 0.00Culvert, Concrete, 12" D - 33 $ 30.05 LF 0.00 0.00 0.00 0.00Culvert, Concrete, 15" D - 34 $ 37.34 LF 0.00 0.00 0.00 0.00Culvert, Concrete, 18" D - 35 $ 44.51 LF 0.00 0.00 0.00 0.00Culvert, Concrete, 24" D - 36 $ 61.07 LF 0.00 0.00 0.00 0.00Culvert, Concrete, 30" D - 37 $ 104.18 LF 0.00 0.00 0.00 0.00Culvert, Concrete, 36" D - 38 $ 137.63 LF 0.00 0.00 0.00 0.00Culvert, Concrete, 42" D - 39 $ 158.42 LF 0.00 0.00 0.00 0.00Culvert, Concrete, 48" D - 40 $ 175.94 LF 0.00 0.00 0.00 0.00Culvert, CPP, 6" D - 41 $ 10.70 LF 0.00 0.00 556 5949.20 0.00Culvert, CPP, 8" D - 42 $ 16.10 LF 0.00 0.00 0.00 0.00Culvert, CPP, 12" D - 43 $ 20.70 LF 0.00 434 8983.80 0.00 0.00Culvert, CPP, 15" D - 44 $ 23.00 LF 0.00 0.00 0.00 0.00Culvert, CPP, 18" D - 45 $ 27.60 LF 0.00 0.00 0.00 0.00Culvert, CPP, 24" D - 46 $ 36.80 LF 0.00 0.00 0.00 0.00Culvert, CPP, 30" D - 47 $ 48.30 LF 0.00 0.00 0.00 0.00Culvert, CPP, 36" D - 48 $ 55.20 LF 0.00 0.00 0.00 0.00Ditching D - 49 $ 8.08 CY 0.000.00 0.00 0.00Flow Dispersal Trench (1,436 base+)D - 50 $ 25.99 LF 0.00 0.00 0.00 0.00French Drain (3' depth) D - 51 $ 22.60 LF0.00 0.00 0.00 0.00Geotextile, laid in trench, polypropylene D - 52 $ 2.40 SY 0.00 0.00 0.00 0.00Infiltration pond testing D - 53 $ 74.75 HR0.00 0.00 0.00 0.00Mid-tank Access Riser, 48" dia, 6' deep D - 54 $ 1,605.40Each 0.00 0.00 0.00 0.00Pond Overflow Spillway D - 55 $ 14.01 SY 0.00 0.00 0.00 0.00Restrictor/Oil Separator, 12" D - 56 $ 1,045.19 Each0.00 0.00 0.00 0.00Restrictor/Oil Separator, 15" D - 57 $ 1,095.56 Each0.00 0.00 0.00 0.00Restrictor/Oil Separator, 18" D - 58 $ 1,146.16 Each0.00 0.00 0.00 0.00Riprap, placed D - 59 $ 39.08 CY 0.000.00 0.00 0.00Tank End Reducer (36" diameter) D - 60 $ 1,000.50 Each0.00 0.00 0.00 0.00Trash Rack, 12" D - 61 $ 211.97 Each 0.000.00 0.00 0.00Trash Rack, 15" D - 62 $ 237.27 Each 0.000.00 0.00 0.00Trash Rack, 18" D - 63 $ 268.89 Each 0.000.00 0.00 0.00Trash Rack, 21" D - 64 $ 306.84 Each 0.000.00 0.00 0.00Page 6 of 7 SUBTOTAL $0.00 $8,983.80 $5,949.20 $0.00DRAINAGE CONTINUEDExistingRight-of-wayFuture PublicRoad Improvements& Drainage FacilitiesPrivateImprovementsBond Reduction*Quant. CompleteCostREF 8-H BOND QUANTITY WORKSHEET.XLSUnity proces updates: 2/12/02Version: 4/22/02Report Date: 1/19/10 Site Improvement Bond Quantity Worksheet Unit Price UnitNo.2" AC, 2" top course rock & 4" borrow PL - 1 $ 15.84 SY 0.00 0.00 0.00 0.002" AC, 1.5" top course & 2.5" base cours PL - 2 $ 17.24 SY 0.00 0.00 0.00 0.004" select borrow PL - 3 $ 4.55 SY 0.00 0.00 0.00 0.001.5" top course rock & 2.5" base coursePL - 4 $ 11.41 SY 0.00 0.00 0.00 0.00(Such as detention/water quality vaults.) No.Detention/WQ Vault WI - 1 $150,000.00 Each 0.00 1 150000.00 0.00 0.003" Gravel Access Road WI - 2 $10.00 SY 0.00 0.00 130 1300.00 0.00Cememt Conc Driveway WI - 3 $850.00 Each 7 5950.00 0.00 0.00 0.00Culvert, CPP, 4" WI - 4 $8.00 LF 0.00 0.00 83 664.00 0.00WI - 6 0.00 0.00 0.00 0.00WI - 7 0.00 0.00 0.00 0.00WI - 8 0.00 0.00 0.00 0.00WI - 9 0.00 0.00 0.00 0.00WI - 10 0.00 0.00 0.00 0.00SUBTOTAL 5950.00 150000.00 1964.00 0.00SUBTOTAL (SUM ALL PAGES): 81245.53 182934.14 44722.27 0.0030% CONTINGENCY & MOBILIZATION: 24373.6602 54880.242 13416.6822 0GRANDTOTAL: 105619.19 237814.38 58138.96 0.00COLUMN: BC D EPage 7 of 7Quant. CompleteCostQuant. PriceQuant. CostQuant. CostExistingRight-of-wayFuture PublicRoad Improvements& Drainage FacilitiesPARKING LOT SURFACINGWRITE-IN-ITEMSPrivateImprovementsBond Reduction*REF 8-H BOND QUANTITY WORKSHEET.XLSUnity proces updates: 2/12/02Version: 4/22/02Report Date: 1/19/10 Reference # Unit Quantity# ofApplicationsCostNumberESC-1$5.62CY0ESC-2SWDM 5.4.6.3 $ 67.51 Each8 1 540.08ESC-3WSDOT 9-03.9(3) $ 85.45 CY0ESC-4$8.08CY50 1 404ESC-5$1.5CY0ESC-6SWDM 5.4.3.1 $ 1.38 LF1040 1 1435.2ESC-7$1.38LF0ESC-8SWDM 5.4.2.4 $ 0.59 SY6350 1 3746.5ESC-9SWDM 5.4.2.2 $ 1.45 SY0ESC-10SWDM 5.4.2.1 $ 2.01 SY0ESC-11SWDM 5.4.2.1 $ 0.53 SY0ESC-12$ 10.7 LF0ESC-13$ 16.1 LF49 1 788.9ESC-14$ 20.7 LF0ESC-15SWDM 5.4.2.3 $ 2.3 SY250 1 575ESC-16WSDOT 9-13.1(2) $ 39.08 CY0ESC-17SWDM 5.4.4.1 $ 1464.34 Each1 1 1464.34ESC-18SWDM 5.4.4.1 $ 2928.68 Each0ESC-19SWDM 5.4.5.2 $ 1949.38 Each0ESC-20SWDM 5.4.5.1 $ 17.91 LF0ESC-21SWDM 5.4.5.1 $ 68.54 LF0Seeding, by handESC-22SWDM 5.4.2.4 $ 0.51 SY0ESC-23SWDM 5.4.2.5 $ 6.03 SY0ESC-24SWDM 5.4.2.5 $ 7.45 SY0ESC-25$ 74.75 HR20 1 1495ESC-26SWDM 5.4.7 $ 97.75 HR8 1 782$ 125 Each6 1 750ESC SUBTOTAL:$ 11,981.0230% CONTINGENCY & MOBILIZATION:$ 3,594.31ESC TOTAL:$ 15,575.33COLUMN:AUnitPriceEROSION/SEDIMENT CONTROLFence, siltFence, Temporary (NGPE)HydroseedingJute MeshMulch, by hand, straw, 3" deepBackfill & compaction-embankmentCheck dams, 4" minus rockCrushed surfacing 1 1/4" minusDitchingExcavation-bulkRip Rap, machine placed; slopesRock Construction Entrance, 50'x15'x1'Rock Construction Entrance, 100'x15'x1'Sediment pond riser assemblySediment trap, 5' high bermMulch, by machine, straw, 2" deepPiping, temporary, CPP, 6"Piping, temporary, CPP, 8"Piping, temporary, CPP, 12"Plastic covering, 6mm thick, sandbaggedSed. trap, 5' high, riprapped spillway berm sectionSodding, 1" deep, level groundSodding, 1" deep, sloped groundTESC SupervisorWater truck, dust controlWRITE-IN-ITEMS Filter Fabric Protection Core Design, Inc. MERLINO SHORT PLAT Page 37 10 OPERATIONS AND MAINTENANCE The operations and maintenance information has been provided through select portions from Appendix A of the 2009 KCSWDM. KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES This appendix contains the maintenance requirements for the following typical stormwater control facilities and components: No. 1 – Detention Ponds (p. A-2) No. 2 – Infiltration Facilities (p. A-3) No. 3 – Detention Tanks and Vaults (p. A-5) No. 4 – Control Structure/Flow Restrictor (p. A-7) No. 5 – Catch Basins and Manholes (p. A-9) No. 6 – Conveyance Pipes and Ditches (p. A-11) No. 7 – Debris Barriers (e.g., Trash Racks) (p. A-12) No. 8 – Energy Dissipaters (p. A- 13) No. 9 – Fencing (p. A-14) No. 10 – Gates/Bollards/Access Barriers (p. A-15) No. 11 – Grounds (Landscaping) (p. A-16) No. 12 – Access Roads (p. A-17) No. 13 – Basic Biofiltration Swale (grass) (p. A-18) No. 14 – Wet Biofiltration Swale (p. A-19) No. 15 – Filter Strip (p. A-20) No. 16 – Wetpond (p. A-21) No. 17 – Wetvault (p. A-23) No. 18 – Stormwater Wetland (p. A-24) No. 19 – Sand Filter Pond (p. A-26) No. 20 – Sand Filter Vault (p. A-28) No. 21 – Stormfilter (Cartridge Type) (p. A-30) No. 22 – Baffle Oil/Water Separator (p. A-32) No. 23 – Coalescing Plate Oil/Water Separator (p. A-33) No. 24 – Catch Basin Insert (p. A-35) 2009 Surface Water Design Manual – Appendix A 1/9/2009 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 3 – DETENTION TANKS AND VAULTS Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Site Trash and debris Any trash and debris which exceed 1 cubic foot per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard size office garbage can). In general, there should be no visual evidence of dumping. Trash and debris cleared from site. Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to County personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where County personnel or the public might normally be. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches. Tank or Vault Storage Area Trash and debris Any trash and debris accumulated in vault or tank (includes floatables and non-floatables). No trash or debris in vault. Sediment accumulation Accumulated sediment depth exceeds 10% of the diameter of the storage area for ½ length of storage vault or any point depth exceeds 15% of diameter. Example: 72-inch storage tank would require cleaning when sediment reaches depth of 7 inches for more than ½ length of tank. All sediment removed from storage area. Tank Structure Plugged air vent Any blockage of the vent. Tank or vault freely vents. Tank bent out of shape Any part of tank/pipe is bent out of shape more than 10% of its design shape. Tank repaired or replaced to design. Gaps between sections, damaged joints or cracks or tears in wall A gap wider than ½-inch at the joint of any tank sections or any evidence of soil particles entering the tank at a joint or through a wall. No water or soil entering tank through joints or walls. Vault Structure Damage to wall, frame, bottom, and/or top slab Cracks wider than ½-inch, any evidence of soil entering the structure through cracks or qualified inspection personnel determines that the vault is not structurally sound. Vault is sealed and structurally sound. Inlet/Outlet Pipes Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. 2009 Surface Water Design Manual – Appendix A 1/9/2009 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 3 – DETENTION TANKS AND VAULTS Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Access Manhole Cover/lid not in place Cover/lid is missing or only partially in place. Any open manhole requires immediate maintenance. Manhole access covered. Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs of lift. Cover/lid can be removed and reinstalled by one maintenance person. Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards. Allows maintenance person safe access. Large access doors/plate Damaged or difficult to open Large access doors or plates cannot be opened/removed using normal equipment. Replace or repair access door so it can opened as designed. Gaps, doesn't cover completely Large access doors not flat and/or access opening not completely covered. Doors close flat and covers access opening completely. Lifting Rings missing, rusted Lifting rings not capable of lifting weight of door or plate. Lifting rings sufficient to lift or remove door or plate. 2009 Surface Water Design Manual – Appendix A 1/9/2009 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Structure Trash and debris Trash or debris of more than ½ cubic foot which is located immediately in front of the structure opening or is blocking capacity of the structure by more than 10%. No Trash or debris blocking or potentially blocking entrance to structure. Trash or debris in the structure that exceeds 1/ 3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin. No trash or debris in the structure. Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents. Sediment Sediment exceeds 60% of the depth from the bottom of the structure to the invert of the lowest pipe into or out of the structure or the bottom of the FROP-T section or is within 6 inches of the invert of the lowest pipe into or out of the structure or the bottom of the FROP-T section. Sump of structure contains no sediment. Damage to frame and/or top slab Corner of frame extends more than ¾ inch past curb face into the street (If applicable). Frame is even with curb. Top slab has holes larger than 2 square inches or cracks wider than ¼ inch. Top slab is free of holes and cracks. Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab. Frame is sitting flush on top slab. Cracks in walls or bottom Cracks wider than ½ inch and longer than 3 feet, any evidence of soil particles entering structure through cracks, or maintenance person judges that structure is unsound. Structure is sealed and structurally sound. Cracks wider than ½ inch and longer than 1 foot at the joint of any inlet/outlet pipe or any evidence of soil particles entering structure through cracks. No cracks more than 1/ inch wide at 4 the joint of inlet/outlet pipe. Settlement/ misalignment Structure has settled more than 1 inch or has rotated more than 2 inches out of alignment. Basin replaced or repaired to design standards. Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the structure at the joint of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of inlet/outlet pipes. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Ladder rungs missing or unsafe Ladder is unsafe due to missing rungs, misalignment, rust, cracks, or sharp edges. Ladder meets design standards and allows maintenance person safe access. FROP-T Section Damage T section is not securely attached to structure wall and outlet pipe structure should support at least 1,000 lbs of up or down pressure. T section securely attached to wall and outlet pipe. Structure is not in upright position (allow up to 10% from plumb). Structure in correct position. Connections to outlet pipe are not watertight or show signs of deteriorated grout. Connections to outlet pipe are water tight; structure repaired or replaced and works as designed. Any holes—other than designed holes—in the structure. Structure has no holes other than designed holes. Cleanout Gate Damaged or missing Cleanout gate is missing. Replace cleanout gate. 2009 Surface Water Design Manual – Appendix A 1/9/2009 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Cleanout gate is not watertight. Gate is watertight and works as designed. Gate cannot be moved up and down by one maintenance person. Gate moves up and down easily and is watertight. Chain/rod leading to gate is missing or damaged. Chain is in place and works as designed. Orifice Plate Damaged or missing Control device is not working properly due to missing, out of place, or bent orifice plate. Plate is in place and works as designed. Obstructions Any trash, debris, sediment, or vegetation blocking the plate. Plate is free of all obstructions and works as designed. Overflow Pipe Obstructions Any trash or debris blocking (or having the potential of blocking) the overflow pipe. Pipe is free of all obstructions and works as designed. Deformed or damaged lip Lip of overflow pipe is bent or deformed. Overflow pipe does not allow overflow at an elevation lower than design Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. Metal Grates (If Applicable) Unsafe grate opening Grate with opening wider than 7/ inch. 8 Grate opening meets design standards. Trash and debris Trash and debris that is blocking more than 20% of grate surface. Grate free of trash and debris. footnote to guidelines for disposal Damaged or missing Grate missing or broken member(s) of the grate. Grate is in place and meets design standards. Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent maintenance. Cover/lid protects opening to structure. Locking mechanism Not Working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to Remove One maintenance person cannot remove cover/lid after applying 80 lbs. of lift. Cover/lid can be removed and reinstalled by one maintenance person. 2009 Surface Water Design Manual – Appendix A 1/9/2009 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 5 – CATCH BASINS AND MANHOLES Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Structure Sediment Sediment exceeds 60% of the depth from the bottom of the catch basin to the invert of the lowest pipe into or out of the catch basin or is within 6 inches of the invert of the lowest pipe into or out of the catch basin. Sump of catch basin contains no sediment. Trash and debris Trash or debris of more than ½ cubic foot which is located immediately in front of the catch basin opening or is blocking capacity of the catch basin by more than 10%. No Trash or debris blocking or potentially blocking entrance to catch basin. Trash or debris in the catch basin that exceeds 1/ the depth from the bottom of basin to invert the 3 lowest pipe into or out of the basin. No trash or debris in the catch basin. Dead animals or vegetation that could generate odors that could cause complaints or dangerous gases (e.g., methane). No dead animals or vegetation present within catch basin. Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents. Damage to frame and/or top slab Corner of frame extends more than ¾ inch past curb face into the street (If applicable). Frame is even with curb. Top slab has holes larger than 2 square inches or cracks wider than ¼ inch. Top slab is free of holes and cracks. Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the top slab. Frame is sitting flush on top slab. Cracks in walls or bottom Cracks wider than ½ inch and longer than 3 feet, any evidence of soil particles entering catch basin through cracks, or maintenance person judges that catch basin is unsound. Catch basin is sealed and structurally sound. Cracks wider than ½ inch and longer than 1 foot at the joint of any inlet/outlet pipe or any evidence of soil particles entering catch basin through cracks. No cracks more than 1/ inch wide at 4 the joint of inlet/outlet pipe. Settlement/ misalignment Catch basin has settled more than 1 inch or has rotated more than 2 inches out of alignment. Basin replaced or repaired to design standards. Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the catch basin at the joint of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of inlet/outlet pipes. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. 2009 Surface Water Design Manual – Appendix A 1/9/2009 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 5 – CATCH BASINS AND MANHOLES Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Metal Grates (Catch Basins) Unsafe grate opening Grate with opening wider than 7/ inch. 8 Grate opening meets design standards. Trash and debris Trash and debris that is blocking more than 20% of grate surface. Grate free of trash and debris. footnote to guidelines for disposal Damaged or missing Grate missing or broken member(s) of the grate. Any open structure requires urgent maintenance. Grate is in place and meets design standards. Manhole Cover/Lid Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent maintenance. Cover/lid protects opening to structure. Locking mechanism Not Working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to Remove One maintenance person cannot remove cover/lid after applying 80 lbs. of lift. Cover/lid can be removed and reinstalled by one maintenance person. 2009 Surface Water Design Manual – Appendix A 1/9/2009 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 6 – CONVEYANCE PIPES AND DITCHES Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Pipes Sediment & debris accumulation Accumulated sediment or debris that exceeds 20% of the diameter of the pipe. Water flows freely through pipes. Vegetation/roots Vegetation/roots that reduce free movement of water through pipes. Water flows freely through pipes. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Damage to protective coating or corrosion Protective coating is damaged; rust or corrosion is weakening the structural integrity of any part of pipe. Pipe repaired or replaced. Damaged Any dent that decreases the cross section area of pipe by more than 20% or is determined to have weakened structural integrity of the pipe. Pipe repaired or replaced. Ditches Trash and debris Trash and debris exceeds 1 cubic foot per 1,000 square feet of ditch and slopes. Trash and debris cleared from ditches. Sediment accumulation Accumulated sediment that exceeds 20% of the design depth. Ditch cleaned/flushed of all sediment and debris so that it matches design. Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to County personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where County personnel or the public might normally be. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Vegetation Vegetation that reduces free movement of water through ditches. Water flows freely through ditches. Erosion damage to slopes Any erosion observed on a ditch slope. Slopes are not eroding. Rock lining out of place or missing (If Applicable) One layer or less of rock exists above native soil area 5 square feet or more, any exposed native soil. Replace rocks to design standards. 2009 Surface Water Design Manual – Appendix A 1/9/2009 APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 9 – FENCING Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Site Erosion or holes under fence Erosion or holes more than 4 inches high and 12- 18 inches wide permitting access through an opening under a fence. No access under the fence. Wood Posts, Boards and Cross Members Missing or damaged parts Missing or broken boards, post out of plumb by more than 6 inches or cross members broken No gaps on fence due to missing or broken boards, post plumb to within 1½ inches, cross members sound. Weakened by rotting or insects Any part showing structural deterioration due to rotting or insect damage All parts of fence are structurally sound. Damaged or failed post foundation Concrete or metal attachments deteriorated or unable to support posts. Post foundation capable of supporting posts even in strong wind. Metal Posts, Rails and Fabric Damaged parts Post out of plumb more than 6 inches. Post plumb to within 1½ inches. Top rails bent more than 6 inches. Top rail free of bends greater than 1 inch. Any part of fence (including post, top rails, and fabric) more than 1 foot out of design alignment. Fence is aligned and meets design standards. Missing or loose tension wire. Tension wire in place and holding fabric. Deteriorated paint or protective coating Part or parts that have a rusting or scaling condition that has affected structural adequacy. Structurally adequate posts or parts with a uniform protective coating. Openings in fabric Openings in fabric are such that an 8-inch diameter ball could fit through. Fabric mesh openings within 50% of grid size. 2009 Surface Water Design Manual – Appendix A 1/9/2009 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 17 – WETVAULT Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Site Trash and debris Trash and debris accumulated on facility site. Trash and debris removed from facility site. Treatment Area Trash and debris Any trash and debris accumulated in vault (includes floatables and non-floatables). No trash or debris in vault. Sediment accumulation Sediment accumulation in vault bottom exceeds the depth of the sediment zone plus 6 inches. No sediment in vault. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations. Source control BMPs implemented if appropriate. No contaminants present other than a surface oil film. Vault Structure Damage to wall, frame, bottom, and/or top slab Cracks wider than ½-inch, any evidence of soil entering the structure through cracks, vault does not retain water or qualified inspection personnel determines that the vault is not structurally sound. Vault is sealed and structurally sound. Baffles damaged Baffles corroding, cracking, warping and/or showing signs of failure or baffle cannot be removed. Repair or replace baffles or walls to specifications. Ventilation Ventilation area blocked or plugged. No reduction of ventilation area exists. Inlet/Outlet Pipe Sediment accumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. Gravity Drain Inoperable valve Valve will not open and close. Valve opens and closes normally. Valve won’t seal Valve does not seal completely. Valve completely seals closed. Access Manhole Access cover/lid damaged or difficult to open Access cover/lid cannot be easily opened by one person. Corrosion/deformation of cover/lid. Access cover/lid can be opened by one person. Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. Cover/lid difficult to remove One maintenance person cannot remove cover/lid after applying 80 lbs of lift. Cover/lid can be removed and reinstalled by one maintenance person. Access doors/plate has gaps, doesn't cover completely Large access doors not flat and/or access opening not completely covered. Doors close flat and covers access opening completely. Lifting Rings missing, rusted Lifting rings not capable of lifting weight of door or plate. Lifting rings sufficient to lift or remove door or plate. Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards. Allows maintenance person safe access. 2009 Surface Water Design Manual – Appendix A 1/9/2009 APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES NO. 24 – CATCH BASIN INSERT Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Media Insert Visible Oil Visible oil sheen passing through media Media inset replaced. Insert does not fit catch basin properly Flow gets into catch basin without going through media. All flow goes through media. Filter media plugged Filter media plugged. Flow through filter media is normal. Oil absorbent media saturated Media oil saturated. Oil absorbent media replaced. Water saturated Catch basin insert is saturated with water, which no longer has the capacity to absorb. Insert replaced. Service life exceeded Regular interval replacement due to typical average life of media insert product, typically one month. Media replaced at manufacturer’s recommended interval. Seasonal maintenance When storms occur and during the wet season. Remove, clean and replace or install new insert after major storms, monthly during the wet season or at manufacturer’s recommended interval. 2009 Surface Water Design Manual – Appendix A 1/9/2009 A-35 Appendix A Parcel & Basin Information King County Parcel Report (2225069082) King County Parcel Report (2225069083) This report was generated on 3/3/2014 4:27:16 PM Contact us at giscenter@kingcounty.gov. © 2010 King County Electoral Districts King County planning and critical areas designations King County Districts and Development Conditions for parcel 0007200194 Parcel number 0007200194 Address Not Available Jurisdiction Renton Zipcode 98057 Kroll Map page 337 Thomas Guide page 656 Drainage Basin Black River and Lower Cedar River Watershed Duwamish - Green River and Cedar River / Lake Washington WRIA Duwamish-Green (9) and Cedar-Sammamish (8) PLSS NW - 20 - 23 - 5 Latitude 47.47216 Longitude -122.20223 Voting district RNT 11-1015 King County Council district District 5, Dave Upthegrove (206) 296-1005 Congressional district 9 Legislative district 11 School district Renton #403 Seattle school board district does not apply (not in Seattle) District Court electoral district Southeast Fire district does not apply Water district does not apply Sewer district does not apply Water & Sewer district does not apply Parks & Recreation district does not apply Hospital district Public Hospital District No. 1 Rural library district Rural King County Library System Tribal Lands?No King County zoning NA, check with jurisdiction Development conditions None Comprehensive Plan does not apply Urban Growth Area Urban Community Service Area does not apply Community Planning Area Newcastle Coal mine hazards?Yes Erosion hazards?Yes Landslide hazards?None mapped Seismic hazards?None mapped Potential annexation area does not apply Rural town?No Water service planning area does not apply Roads MPS zone 329 Transportation Concurrency Management does not apply Forest Production district?No Agricultural Production district?No Critical aquifer recharge area?None mapped 100-year flood plain?None mapped Wetlands at this parcel?None mapped This report was generated on 3/3/2014 4:29:50 PM Contact us at giscenter@kingcounty.gov. © 2010 King County Electoral Districts King County planning and critical areas designations King County Districts and Development Conditions for parcel 2023059085 Parcel number 2023059085 Address 700 BENSON RD S Jurisdiction Renton Zipcode 98057 Kroll Map page 337 Thomas Guide page 656 Drainage Basin Black River and Lower Cedar River Watershed Duwamish - Green River and Cedar River / Lake Washington WRIA Duwamish-Green (9) and Cedar-Sammamish (8) PLSS NW - 20 - 23 - 5 Latitude 47.47216 Longitude -122.20322 Voting district RNT 11-1015 King County Council district District 5, Dave Upthegrove (206) 296-1005 Congressional district 9 Legislative district 11 School district Renton #403 Seattle school board district does not apply (not in Seattle) District Court electoral district Southeast Fire district does not apply Water district does not apply Sewer district does not apply Water & Sewer district does not apply Parks & Recreation district does not apply Hospital district Public Hospital District No. 1 Rural library district Rural King County Library System Tribal Lands?No King County zoning NA, check with jurisdiction Development conditions None Comprehensive Plan does not apply Urban Growth Area Urban Community Service Area does not apply Community Planning Area Newcastle and Green River Valley Coal mine hazards?Yes Erosion hazards?Yes Landslide hazards?None mapped Seismic hazards?None mapped Potential annexation area does not apply Rural town?No Water service planning area does not apply Roads MPS zone 329 Transportation Concurrency Management does not apply Forest Production district?No Agricultural Production district?No Critical aquifer recharge area?None mapped 100-year flood plain?None mapped Wetlands at this parcel?None mapped Appendix B Resource Review & Off-site Analysis Documentation FEMA Map (53033C0977F) City of Renton Aquifer Protection Zones City of Renton Groundwater Protection Areas City of Renton Sensitive Area Maps City of Renton Soil Survey Drainage Complaints Exhibit Downstream Drainage Map Appendix C Pond Sizing City of Renton Flow Control Map Rainfall Region & Regional Scale Factor (Figure 3.2.2.A) KCRTS Hydrologic Soils Group Table (Table 3.2.2.B) Mean Annual Storm Precipitation (Figure 6.4.1.A) KCRTS Input Vault Summary Peaks Analysis Durations Analysis Page 1 KCRTS Program...File Directory: C:\KC_SWDM\KC_DATA\ [C] CREATE a new Time Series ST 1.50 0.00 0.000000 Till Forest 0.00 0.00 0.000000 Till Pasture 0.00 0.00 0.000000 Till Grass 0.00 0.00 0.000000 Outwash Forest 0.00 0.00 0.000000 Outwash Pasture 0.00 0.00 0.000000 Outwash Grass 0.00 0.00 0.000000 Wetland 0.10 0.00 0.000000 Impervious 04139M_Pre.tsf T 1.00000 T [T] Enter the Analysis TOOLS Module [P] Compute PEAKS and Flow Frequencies 04139M_Pre.tsf 04139M_Pre.pks [R] RETURN to Previous Menu [C] CREATE a new Time Series ST 0.00 0.00 0.000000 Till Forest 0.00 0.00 0.000000 Till Pasture 0.65 0.00 0.000000 Till Grass 0.00 0.00 0.000000 Outwash Forest 0.00 0.00 0.000000 Outwash Pasture 0.00 0.00 0.000000 Outwash Grass 0.00 0.00 0.000000 Wetland 0.95 0.00 0.000000 Impervious 04139M_Dev.tsf T 1.00000 T [T] Enter the Analysis TOOLS Module [P] Compute PEAKS and Flow Frequencies 04139M_Dev.tsf 04139M_Dev.pks [R] RETURN to Previous Menu [C] CREATE a new Time Series ST 0.00 0.00 0.000000 Till Forest 0.00 0.00 0.000000 Till Pasture 0.65 0.00 0.000000 Till Grass 0.00 0.00 0.000000 Outwash Forest 0.00 0.00 0.000000 Outwash Pasture 0.00 0.00 0.000000 Outwash Grass 0.00 0.00 0.000000 Wetland 0.95 0.00 0.000000 Impervious 04139M_Dev15.tsf T 1.00000 F Page 2 [T] Enter the Analysis TOOLS Module [P] Compute PEAKS and Flow Frequencies 04139M_Dev15.tsf 04139M_Dev15.pks [D] Compute Flow DURATION and Exceedence 04139M_Pre.tsf 04139M_Pre.dur F F 36 0.0036 0.0315 [R] RETURN to Previous Menu Retention/Detention Facility Type of Facility: Detention Vault Facility Length: 56.00 ft Facility Width: 40.00 ft Facility Area: 2240. sq. ft Effective Storage Depth: 7.00 ft Stage 0 Elevation: 216.00 ft Storage Volume: 15680. cu. ft Riser Head: 7.00 ft Riser Diameter: 12.00 inches Number of orifices: 3 Full Head Pipe Orifice # Height Diameter Discharge Diameter (ft) (in) (CFS) (in) 1 0.00 0.75 0.040 2 4.00 0.81 0.031 4.0 3 5.10 0.94 0.033 4.0 Top Notch Weir: None Outflow Rating Curve: None Stage Elevation Storage Discharge Percolation (ft) (ft) (cu. ft) (ac-ft) (cfs) (cfs) 0.00 216.00 0. 0.000 0.000 0.00 0.01 216.01 22. 0.001 0.001 0.00 0.02 216.02 45. 0.001 0.002 0.00 0.03 216.03 67. 0.002 0.003 0.00 0.04 216.04 90. 0.002 0.003 0.00 0.05 216.05 112. 0.003 0.004 0.00 0.06 216.06 134. 0.003 0.004 0.00 0.20 216.20 448. 0.010 0.007 0.00 0.34 216.34 762. 0.017 0.009 0.00 0.47 216.47 1053. 0.024 0.011 0.00 0.61 216.61 1366. 0.031 0.012 0.00 0.75 216.75 1680. 0.039 0.013 0.00 0.89 216.89 1994. 0.046 0.014 0.00 1.02 217.02 2285. 0.052 0.015 0.00 1.16 217.16 2598. 0.060 0.016 0.00 1.30 217.30 2912. 0.067 0.017 0.00 1.44 217.44 3226. 0.074 0.018 0.00 1.57 217.57 3517. 0.081 0.019 0.00 1.71 217.71 3830. 0.088 0.020 0.00 1.85 217.85 4144. 0.095 0.021 0.00 1.98 217.98 4435. 0.102 0.021 0.00 2.12 218.12 4749. 0.109 0.022 0.00 2.26 218.26 5062. 0.116 0.023 0.00 2.40 218.40 5376. 0.123 0.024 0.00 2.53 218.53 5667. 0.130 0.024 0.00 2.67 218.67 5981. 0.137 0.025 0.00 2.81 218.81 6294. 0.144 0.026 0.00 2.94 218.94 6586. 0.151 0.026 0.00 3.08 219.08 6899. 0.158 0.027 0.00 3.22 219.22 7213. 0.166 0.027 0.00 3.36 219.36 7526. 0.173 0.028 0.00 3.49 219.49 7818. 0.179 0.029 0.00 3.63 219.63 8131. 0.187 0.029 0.00 3.77 219.77 8445. 0.194 0.030 0.00 3.91 219.91 8758. 0.201 0.030 0.00 4.00 220.00 8960. 0.206 0.031 0.00 4.01 220.01 8982. 0.206 0.031 0.00 4.02 220.02 9005. 0.207 0.031 0.00 4.03 220.03 9027. 0.207 0.033 0.00 4.04 220.04 9050. 0.208 0.034 0.00 4.05 220.05 9072. 0.208 0.035 0.00 4.06 220.06 9094. 0.209 0.035 0.00 4.07 220.07 9117. 0.209 0.035 0.00 4.08 220.08 9139. 0.210 0.036 0.00 4.21 220.21 9430. 0.216 0.040 0.00 4.35 220.35 9744. 0.224 0.042 0.00 4.49 220.49 10058. 0.231 0.045 0.00 4.63 220.63 10371. 0.238 0.047 0.00 4.76 220.76 10662. 0.245 0.049 0.00 4.90 220.90 10976. 0.252 0.051 0.00 5.04 221.04 11290. 0.259 0.052 0.00 5.10 221.10 11424. 0.262 0.053 0.00 5.11 221.11 11446. 0.263 0.054 0.00 5.12 221.12 11469. 0.263 0.054 0.00 5.13 221.13 11491. 0.264 0.055 0.00 5.14 221.14 11514. 0.264 0.057 0.00 5.15 221.15 11536. 0.265 0.058 0.00 5.16 221.16 11558. 0.265 0.060 0.00 5.17 221.17 11581. 0.266 0.060 0.00 5.18 221.18 11603. 0.266 0.061 0.00 5.32 221.32 11917. 0.274 0.067 0.00 5.45 221.45 12208. 0.280 0.071 0.00 5.59 221.59 12522. 0.287 0.075 0.00 5.73 221.73 12835. 0.295 0.079 0.00 5.86 221.86 13126. 0.301 0.082 0.00 6.00 222.00 13440. 0.309 0.085 0.00 6.14 222.14 13754. 0.316 0.088 0.00 6.28 222.28 14067. 0.323 0.091 0.00 6.41 222.41 14358. 0.330 0.094 0.00 6.55 222.55 14672. 0.337 0.096 0.00 6.69 222.69 14986. 0.344 0.099 0.00 6.83 222.83 15299. 0.351 0.101 0.00 6.96 222.96 15590. 0.358 0.104 0.00 7.00 223.00 15680. 0.360 0.104 0.00 7.10 223.10 15904. 0.365 0.414 0.00 7.20 223.20 16128. 0.370 0.979 0.00 7.30 223.30 16352. 0.375 1.710 0.00 7.40 223.40 16576. 0.381 2.500 0.00 7.50 223.50 16800. 0.386 2.790 0.00 7.60 223.60 17024. 0.391 3.040 0.00 7.70 223.70 17248. 0.396 3.280 0.00 7.80 223.80 17472. 0.401 3.500 0.00 7.90 223.90 17696. 0.406 3.710 0.00 8.00 224.00 17920. 0.411 3.900 0.00 8.10 224.10 18144. 0.417 4.090 0.00 8.20 224.20 18368. 0.422 4.270 0.00 8.30 224.30 18592. 0.427 4.440 0.00 8.40 224.40 18816. 0.432 4.600 0.00 8.50 224.50 19040. 0.437 4.760 0.00 8.60 224.60 19264. 0.442 4.910 0.00 8.70 224.70 19488. 0.447 5.060 0.00 8.80 224.80 19712. 0.453 5.200 0.00 Hyd Inflow Outflow Peak Storage Target Calc Stage Elev (Cu-Ft) (Ac-Ft) 1 0.59 ******* 0.42 7.10 223.10 15906. 0.365 2 0.29 ******* 0.10 6.94 222.94 15535. 0.357 3 0.29 0.10 0.09 6.09 222.09 13650. 0.313 4 0.35 ******* 0.07 5.46 221.46 12230. 0.281 5 0.31 ******* 0.07 5.32 221.32 11912. 0.273 6 0.18 0.06 0.04 4.10 220.10 9189. 0.211 7 0.23 ******* 0.03 3.31 219.31 7414. 0.170 8 0.25 ******* 0.02 2.52 218.52 5637. 0.129 ---------------------------------- Route Time Series through Facility Inflow Time Series File:04139m_dev.tsf Outflow Time Series File:rdout Inflow/Outflow Analysis Peak Inflow Discharge: 0.586 CFS at 6:00 on Jan 9 in Year 8 Peak Outflow Discharge: 0.419 CFS at 9:00 on Jan 9 in Year 8 Peak Reservoir Stage: 7.10 Ft Peak Reservoir Elev: 223.10 Ft Peak Reservoir Storage: 15906. Cu-Ft : 0.365 Ac-Ft Flow Frequency Analysis Time Series File:rdout.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) (ft) Period 0.103 2 2/09/01 20:00 0.419 7.10 1 100.00 0.990 0.028 7 12/28/01 18:00 0.103 6.94 2 25.00 0.960 0.071 4 3/06/03 22:00 0.087 6.09 3 10.00 0.900 0.024 8 8/26/04 7:00 0.071 5.46 4 5.00 0.800 0.037 6 1/05/05 16:00 0.067 5.32 5 3.00 0.667 0.067 5 1/18/06 23:00 0.037 4.10 6 2.00 0.500 0.087 3 11/24/06 8:00 0.028 3.31 7 1.30 0.231 0.419 1 1/09/08 9:00 0.024 2.52 8 1.10 0.091 Computed Peaks 0.313 7.07 50.00 0.980 Flow Duration from Time Series File:rdout.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS % % % 0.002 36988 60.320 60.320 39.680 0.397E+00 0.004 4075 6.645 66.965 33.035 0.330E+00 0.007 4660 7.599 74.565 25.435 0.254E+00 0.010 3838 6.259 80.824 19.176 0.192E+00 0.013 4025 6.564 87.387 12.613 0.126E+00 0.016 2727 4.447 91.835 8.165 0.817E-01 0.019 1561 2.546 94.380 5.620 0.562E-01 0.022 1246 2.032 96.412 3.588 0.359E-01 0.025 726 1.184 97.596 2.404 0.240E-01 0.028 664 1.083 98.679 1.321 0.132E-01 0.030 440 0.718 99.397 0.603 0.603E-02 0.033 56 0.091 99.488 0.512 0.512E-02 0.036 21 0.034 99.522 0.478 0.478E-02 0.039 35 0.057 99.579 0.421 0.421E-02 0.042 43 0.070 99.649 0.351 0.351E-02 0.045 18 0.029 99.679 0.321 0.321E-02 0.048 29 0.047 99.726 0.274 0.274E-02 0.051 24 0.039 99.765 0.235 0.235E-02 0.053 41 0.067 99.832 0.168 0.168E-02 0.056 8 0.013 99.845 0.155 0.155E-02 0.059 4 0.007 99.852 0.148 0.148E-02 0.062 9 0.015 99.866 0.134 0.134E-02 0.065 10 0.016 99.883 0.117 0.117E-02 0.068 8 0.013 99.896 0.104 0.104E-02 0.071 11 0.018 99.914 0.086 0.864E-03 0.074 4 0.007 99.920 0.080 0.799E-03 0.076 6 0.010 99.930 0.070 0.701E-03 0.079 6 0.010 99.940 0.060 0.603E-03 0.082 10 0.016 99.956 0.044 0.440E-03 0.085 5 0.008 99.964 0.036 0.359E-03 0.088 6 0.010 99.974 0.026 0.261E-03 0.091 2 0.003 99.977 0.023 0.228E-03 0.094 2 0.003 99.980 0.020 0.196E-03 0.097 3 0.005 99.985 0.015 0.147E-03 0.100 3 0.005 99.990 0.010 0.978E-04 0.102 4 0.007 99.997 0.003 0.326E-04 Duration Comparison Anaylsis Base File: 04139m_pre.tsf New File: rdout.tsf Cutoff Units: Discharge in CFS -----Fraction of Time----- ---------Check of Tolerance------- Cutoff Base New %Change Probability Base New %Change 0.031 | 0.61E-02 0.52E-02 -14.4 | 0.61E-02 0.031 0.030 -3.5 0.037 | 0.48E-02 0.46E-02 -3.8 | 0.48E-02 0.037 0.036 -3.0 0.043 | 0.37E-02 0.33E-02 -8.5 | 0.37E-02 0.043 0.041 -5.1 0.049 | 0.27E-02 0.25E-02 -7.8 | 0.27E-02 0.049 0.048 -2.9 0.055 | 0.20E-02 0.16E-02 -20.7 | 0.20E-02 0.055 0.052 -6.7 0.062 | 0.14E-02 0.14E-02 -2.3 | 0.14E-02 0.062 0.061 -0.6 0.068 | 0.99E-03 0.10E-02 4.9 | 0.99E-03 0.068 0.068 0.8 0.074 | 0.80E-03 0.80E-03 0.0 | 0.80E-03 0.074 0.074 0.8 0.080 | 0.55E-03 0.59E-03 5.9 | 0.55E-03 0.080 0.080 0.9 0.086 | 0.38E-03 0.34E-03 -8.7 | 0.38E-03 0.086 0.085 -0.9 0.092 | 0.15E-03 0.23E-03 55.6 | 0.15E-03 0.092 0.097 6.4 0.098 | 0.98E-04 0.11E-03 16.7 | 0.98E-04 0.098 0.100 1.9 0.104 | 0.65E-04 0.00E+00 -100.0 | 0.65E-04 0.104 0.101 -2.2 0.110 | 0.16E-04 0.00E+00 -100.0 | 0.16E-04 0.110 0.103 -5.8 Maximum positive excursion = 0.006 cfs ( 6.4%) occurring at 0.092 cfs on the Base Data:04139m_pre.tsf and at 0.097 cfs on the New Data:rdout.tsf Maximum negative excursion = 0.004 cfs (-10.8%) occurring at 0.035 cfs on the Base Data:04139m_pre.tsf and at 0.031 cfs on the New Data:rdout.tsf ---------------------------------- Route Time Series through Facility Inflow Time Series File:04139m_dev.tsf Outflow Time Series File:rdout Inflow/Outflow Analysis Peak Inflow Discharge: 0.586 CFS at 6:00 on Jan 9 in Year 8 Peak Outflow Discharge: 0.419 CFS at 9:00 on Jan 9 in Year 8 Peak Reservoir Stage: 7.10 Ft Peak Reservoir Elev: 223.10 Ft Peak Reservoir Storage: 15906. Cu-Ft : 0.365 Ac-Ft Flow Frequency Analysis Time Series File:rdout.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) (ft) Period 0.103 2 2/09/01 20:00 0.419 7.10 1 100.00 0.990 0.028 7 12/28/01 18:00 0.103 6.94 2 25.00 0.960 0.071 4 3/06/03 22:00 0.087 6.09 3 10.00 0.900 0.024 8 8/26/04 7:00 0.071 5.46 4 5.00 0.800 0.037 6 1/05/05 16:00 0.067 5.32 5 3.00 0.667 0.067 5 1/18/06 23:00 0.037 4.10 6 2.00 0.500 0.087 3 11/24/06 8:00 0.028 3.31 7 1.30 0.231 0.419 1 1/09/08 9:00 0.024 2.52 8 1.10 0.091 Computed Peaks 0.313 7.07 50.00 0.980 Flow Duration from Time Series File:rdout.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS % % % 0.002 36988 60.320 60.320 39.680 0.397E+00 0.004 4075 6.645 66.965 33.035 0.330E+00 0.007 4660 7.599 74.565 25.435 0.254E+00 0.010 3838 6.259 80.824 19.176 0.192E+00 0.013 4025 6.564 87.387 12.613 0.126E+00 0.016 2727 4.447 91.835 8.165 0.817E-01 0.019 1561 2.546 94.380 5.620 0.562E-01 0.022 1246 2.032 96.412 3.588 0.359E-01 0.025 726 1.184 97.596 2.404 0.240E-01 0.028 664 1.083 98.679 1.321 0.132E-01 0.030 440 0.718 99.397 0.603 0.603E-02 0.033 56 0.091 99.488 0.512 0.512E-02 0.036 21 0.034 99.522 0.478 0.478E-02 0.039 35 0.057 99.579 0.421 0.421E-02 0.042 43 0.070 99.649 0.351 0.351E-02 0.045 18 0.029 99.679 0.321 0.321E-02 0.048 29 0.047 99.726 0.274 0.274E-02 0.051 24 0.039 99.765 0.235 0.235E-02 0.053 41 0.067 99.832 0.168 0.168E-02 0.056 8 0.013 99.845 0.155 0.155E-02 0.059 4 0.007 99.852 0.148 0.148E-02 0.062 9 0.015 99.866 0.134 0.134E-02 0.065 10 0.016 99.883 0.117 0.117E-02 0.068 8 0.013 99.896 0.104 0.104E-02 0.071 11 0.018 99.914 0.086 0.864E-03 0.074 4 0.007 99.920 0.080 0.799E-03 0.076 6 0.010 99.930 0.070 0.701E-03 0.079 6 0.010 99.940 0.060 0.603E-03 0.082 10 0.016 99.956 0.044 0.440E-03 0.085 5 0.008 99.964 0.036 0.359E-03 0.088 6 0.010 99.974 0.026 0.261E-03 0.091 2 0.003 99.977 0.023 0.228E-03 0.094 2 0.003 99.980 0.020 0.196E-03 0.097 3 0.005 99.985 0.015 0.147E-03 0.100 3 0.005 99.990 0.010 0.978E-04 0.102 4 0.007 99.997 0.003 0.326E-04 Cumulative ProbabilityDischarge (CFS)-2105-1105010 oo ooo R 1 2 5 10 20 30 40 50 2 60 70 80 5 90 10 95 20 98 50 99 100Return Period rdout.pks in Sea-Tac04139M_Pre.pks Probability ExceedenceDischarge (CFS)0.000.020.040.060.080.100.12-510 -410 -310 -210 -110 010 o oo ooo R rdout.dur 04139M_Pre.dur Appendix D Conveyance Calculations BACKWATER CALCULATIONS PROJECT NAME: Merlino Short PlatPREPARED BY: SM PROJECT NUMBER: 04139MDESIGN STORM: 100 YEARENTRANCE ENTRANCE EXIT OUTLET INLET APPROACH BEND JUNCTIONPIPE PIPE MANNING'S OUTLET INLET PIPE FULL VELOCITY TAILWATER FRICTION HGL HEAD HEAD CONTROL CONTROL VELOCITY HEAD HEAD HEADWATER RIMFROM TO Q LENGTH SIZE "n" ELEVATION ELEVATION AREA VELOCITY HEAD ELEVATION LOSS ELEVATION LOSS LOSS ELEVATION ELEVATION HEAD LOSS LOSS ELEVATION ELEVATION FREEBOARDCB CB (CFS) (FT) (IN) VALUE (FT) (FT) (SQ FT) (FT/SEC) (FT) (FT) (FT) (FT) (FT) (FT) (FT) (FT) (FT) (FT) (FT) (FT) (FT) (FT)VAULT CB1 3.12 5 12 0.012220.70 220.74 0.79 3.97 0.25 222.30 0.03 222.33 0.12 0.25 222.70 222.03 0.00 0.32 0.00 223.02 227.81 4.79CB1 CB2 3.12 59 12 0.012 220.74 221.33 0.79 3.97 0.25 223.02 0.38 223.41 0.12 0.25 223.77 222.62 0.20 0.00 0.02 223.60 228.98 5.38CB2 CB3 2.83 35 12 0.012 221.33 223.50 0.79 3.60 0.20 223.60 0.19 224.50 0.10 0.20 224.80 224.66 0.07 0.00 0.09 224.83 230.00 5.17CB3 CB4 1.64 178 12 0.012 223.50 226.97 0.79 2.09 0.07 224.83 0.32 227.97 0.03 0.07 228.07 227.97 0.00 0.00 0.00 228.07 232.91 4.84CB2 CB5 0.33 49 12 0.012 221.33 221.57 0.79 0.42 0.00 223.02 0.00 223.03 0.00 0.00 223.03 222.57 0.00 0.00 0.00 223.03 227.50 4.47CB5 CB6 0.33 55 12 0.012 221.57 221.90 0.79 0.42 0.00 223.03 0.00 223.04 0.00 0.00 223.04 222.90 0.00 0.00 0.00 223.04 224.90 1.86PIPESEGMENT LOCATION / DESIGN STORM YEAR:JOB NAME: Merlino Short Plat JOB NUMBER: 04139M PREPARED BY: SHMINCREMENTAL RUNOFF EFFECTIVE TIME OF RAINFALL TRIBUTARY PIPE PIPE PIPE ACTUAL TRAVELPIPE CAPACITY SUMMARYPIPE SEGMENT AREA COEFFICIENT AREA SUM OF CONC. INTENSITY FLOW MANNING'S DIAMETER SLOPE LENGTH VELOCITY TIME Q(FULL) V(FULL) Q(ACT)/Q(FULL)FROM TO (ACRES) "C" (A * C) (A * C) (MINUTES) (IN/HR) (CFS) "n" (INCHES) (PERCENT) (FEET) (FT/SEC) (MINUTES) (CFS) (FT/SEC) (PERCENT)CB4 CB3 0.80 0.64 0.512 0.512 6.30 3.21 1.642 0.012 12 2.200 1586.23 0.42 5.725 7.29 28.7%CB3 CB2 0.63 0.64 0.403 0.915 6.72 3.10 2.833 0.012 12 6.300 3510.55 0.06 9.688 12.33 29.2% CB6 CB5 0.160.64 0.102 0.102 6.30 3.210.328 0.012 12 0.600 55 2.40 0.38 2.990 3.81 11.0%CB5 CB2 0.000.64 0.000 0.102 6.68 3.110.318 0.012 12 0.500 48 2.19 0.37 2.729 3.47 11.7%CB2 CB1 0.00 0.64 0.000 1.018 6.78 3.08 3.136 0.012 12 1.000 5912.75 0.08 3.860 4.91 81.2%CB1 VAULT 0.000.64 0.000 1.018 6.85 3.063.1160.012 12 1.000 4 5.45 0.01 3.860 4.91 80.7%STORM CONVEYANCE SYSTEM DESIGNSEATTLE / 100 YEAR2/20/2015 CORE DESIGN, INC. PAGE 1 Appendix E Special Reports and Studies Drainage Design for the WSDOT Exchange Property I-405 to SR 169 Stage 2 Widening and SR 515 Interchange Project July 29, 2009 Revised August 13, 2009, July 7, 2010 Prepared By: I-405 Corridor Design-Builders Geological Engineering Services Coal Mine Hazard Assessment Merlino Short Plat Proposed 7-Lot Residential Development Renton, Washington April 23, 2014 Prepared By: Icicle Creek Engineers, Inc. Geotechnical Engineering Services Critical Areas Report Merlino Short Plat Proposed 7-Lot Residential Development Renton, Washington April 23, 2014 Prepared By: Icicle Creek Engineers, Inc. Report Geological Engineering Services Coal Mine Hazard Assessment Merlino Short Plat Proposed 7-Lot Residential Development Renton, Washington April 23, 2014 ICE File No. 0864-001 Prepared For: Merlino Land Development Co., Inc. Prepared By: Icicle Creek Engineers, Inc. April 23, 2014 Merlino Land Development Co., Inc. Attn: Gary Merlino 5050 1st Ave S, Suite 102 Seattle, Washington 98134-2400 Report Geological Engineering Services Coal Mine Hazard Assessment Merlino Short Plat Proposed 7-Lot Residential Development Renton, Washington ICE File No. 0864-001 1.0 INTRODUCTION This report summarizes the results of Icicle Creek Engineers’ (ICE’s) coal mine hazard assessment for the Merlino Short Plat (referred to as the Merlino Property in this report) 7-Lot Residential Development located southwest of the intersection of South 7th Street and Cedar Avenue South in Renton, Washington. The Merlino Property is shown relative to nearby physical features on the Vicinity Map, Figure 1. The general layout of the Merlino Property is shown on the Site Plan, Figure 2. Our services were completed in general accordance with our Scope of Services and Fee Estimate dated April 22, 2009 and our Proposal dated February 4, 2014; these services were authorized in writing by Gary Merlino on April 24, 2009 and March 17, 2014, respectively. 2.0 BACKGROUND INFORMATION ICE previously completed coal mine hazard assessments of the subject property for a previous property owner, GWC, Inc. (GWC); the results of those assessments are presented in our reports dated January 17 and June 10, 2005. Those reports included the Merlino Property as well as additional property that GWC owned to the east and south of the southerly part of the Merlino Property. ICE also completed a hydrogeologic report for GWC dated March 24, 2006 and a geotechnical report for GWC dated September 30, 2005. The approximate locations of subsurface explorations completed on the Merlino Property for those 2005 studies are shown on Figure 2. In addition, ICE completed a geotechnical critical areas report of the Merlino Property; the results are summarized in our report dated April 23, 2014. We understand that, subsequent to the reports we prepared in 2005 and 2006, GWC sold the portion of the GWC property that lies between Cedar Avenue South (and its southerly extension) and Interstate 405 (I-405) to the Washington State Department of Transportation (WSDOT) because preliminary plans for I-405 widening indicated encroachment into this property depending on final I-405 roadway configuration and the need for slope support measures. Thereafter, as part of the I-405 widening project, WSDOT’s design-build team for the I-405 widening project, I-405 Corridor Design Builders (CDB), Merlino Land Development Co., Inc. Attn: Gary Merlino April 23, 2014 Page 2 I c i c l e C r e e k E n g i n e e r s 0864001/042314 placed excess soil that was excavated from an adjacent portion of the I-405 project onto what is now the Merlino Property (property that at the time was owned by WSDOT). The fill was designed as a Reinforced Soil Slope (RSS – the RSS is referred to as the “Engineered Fill” in the remainder of this report) by CDB (with CDB joint venturer CH2M Hill providing the I-405 project’s geotechnical engineering). David Halinen, attorney for MLDC, forwarded to ICE a copy of the CDB report entitled Technical Memorandum, I-405 Renton Stage 2 Design/Build Project, WSDOT Exchange Property Reinforced Soil Slope, Geotechnical Design Recommendations Memorandum, dated August 14, 2009, a technical memorandum that was prepared specifically for that Engineered Fill. That technical memorandum is attached to this report (Attachment A). Page 6 of the CDB Technical Memorandum states an assumption that “structures (e.g., residences) will be constructed on the Engineered Fill in the future” and noted that the factors of safety (FOS) used in the CDB Technical Memorandum were based on that assumption. For that purpose, CDB evaluated the stability of the Engineered Fill for sliding, global stability, compound failure, internal stability, and seismic stability. The final design of the Engineered Fill required a minimum FOS of at least 1.5 for all the factors evaluated. In ICE’s June 2005 coal mine hazard assessment (completed for GWC) that included 12 test pits and three test borings in the Merlino Property area, we concluded that a “High Coal Mine Hazard Area” occurs at the south end of Cedar Avenue South. We reached that conclusion by evaluating historical mine maps and data from borings completed outside of that immediate area. Additional subsurface evaluation completed for this study (2009 ground proofing – seven test borings) targeted the High Coal Mine Hazard Area consistent with Renton Municipal Code (RMC) 4-3-050J.1 (Geologic Hazards - Applicability) and 4-3-050J.2 (Geologic Hazards - Special Studies Required). 3.0 SCOPE OF SERVICES The purpose of our services was to explore subsurface soil and bedrock conditions as a basis for evaluating the High Coal Mine Hazard Area within the Merlino Property. Specifically, our services included the following: Completion of a detailed geologic reconnaissance along the pre-Engineered Fill embankment slope bordering Cedar Avenue South in order to evaluate surface conditions related to underground mine- related collapse (sinkholes) (a reconnaissance completed in 2009 with a post-Engineered Fill reconnaissance on February 2, 2014). Evaluation of subsurface soil and bedrock conditions through a ground-proofing program by means of drilling seven test borings to depths ranging from 53 to 84 feet to evaluate the coal seam and location/collapse status of the mine workings that potentially underlie the south end of Cedar Avenue South (an evaluation completed in 2009). Based on the results of the ground-proofing program, reclassification, if appropriate, of the High Coal Mine Hazard Area as either a Low or Medium Coal Mine Hazard Area. Evaluation of the potential for regional ground subsidence in Medium Coal Mine Hazard Areas (vertical ground subsidence, ground tilt and ground strain), if appropriate. Development of mitigation recommendations for future development within High and Medium Coal Mine Hazard Areas, as needed. 4.0 GEOLOGIC SETTING The surficial geology at the site has been mapped by the US Geological Survey (USGS - D. R. Mullineaux, 1965, “Geologic Map of the Renton Quadrangle, King County, Washington,” Geologic Quadrangle Map Merlino Land Development Co., Inc. Attn: Gary Merlino April 23, 2014 Page 3 I c i c l e C r e e k E n g i n e e r s 0864001/042314 GQ-405) as “undifferentiated glacial sediments” underlain by “Renton Formation” bedrock. Undifferentiated glacial sediments are described by the USGS as consisting of layers of glacial till (ice deposited silty sand with gravel), glacial outwash (stream-deposited sand and gravel), glaciolacustrine deposits (lake-deposited clay and sand), and nonglacial sand and clay. Renton Formation bedrock is described by the USGS as interbedded (layered) sedimentary rock consisting of sandstone, siltstone, shale, claystone, carbonaceous shale and coal beds. Structurally, the bedrock has been uplifted, folded and faulted over time. This structural deformation of the bedrock has caused the “bedding” of the rock to be tilted about 10 to 14 degrees down to the east in the Merlino Property area. 5.0 SITE CONDITIONS 5.1 SURFACE CONDITIONS Surface reconnaissance of the Merlino Property was performed and completed by Brian Beaman of ICE on April 27, 2009 and February 2, 2014. The Merlino Property is located on a west-facing hillside overlooking the City of Renton and is bordered by Cedar Avenue South to the east, Cedar Crest Condominiums to the north, I-405 to the west and undeveloped WSDOT-owned forest land and a Puget Sound Energy (PSE) transmission line easement to the south. Before placement of the Engineered Fill, the portion of the subject property immediately west of Cedar Avenue South was characterized by a steep (60 percent grade) road embankment long-ago-created for Cedar Avenue South, an embankment that was about 5- to 15-feet high and that transitioned to a natural slope inclined downward to the west at about a 20 to 30 percent grade. The natural slope tended to flatten gradually to the west. Mine Rock Fill (Coal Spoils) consisting of broken rock and coal fines were observed during field reconnaissance and test pits (Test Pits TP-8, TP-14 and TP-16) completed for our previously described 2005 study; these test pit locations are shown on Figure 2. Presently, the Engineered Fill has formed along most of the Merlino Property’s east side abutting the west edge of Cedar Avenue South a nearly-level plateau area that extends west the west edge of the existing Cedar Avenue South right-of-way about 112- to 122-feet to the plateau’s crest. This nearly-level plateau area is where the seven residential lots are planned. From the west edge of the plateau, a slope field measured at about 30 degrees (about 1.75H:1V – horizontal to vertical) extends down to the west toward the I-405 right-of-way. The nearly-level plateau area is vegetated with grass. The slope is vegetated with Douglas fir trees about 8-feet high and with shrubs. No surface water was observed within the Merlino Property at the time of our 2009 and 2014 site reconnaissance efforts. We also did not observe topographic anomalies, such as steep-sided pits (sinkholes), which could indicate underground mine collapse within Merlino Property pre- or post- Engineered Fill. 5.2 ABANDONED UNDERGROUND COAL MINES 5.2.1 Documented Mining The Renton Mine was active in the vicinity of the Merlino Property from about 1874 to 1933 on the No. 3 Coal Seam. Typically, coal was removed from this mine using room-and-pillar mining methods; coal “pillars” were left in place for support of the “rooms” where the coal was removed. Eventually, most, or all, of the coal pillars were removed upon retreat of these production areas to promote collapse of the Merlino Land Development Co., Inc. Attn: Gary Merlino April 23, 2014 Page 4 I c i c l e C r e e k E n g i n e e r s 0864001/042314 mined-out areas. A “barrier pillar” of intact coal was usually left in place in the shallowest areas of the coal mine to reduce the risk of causing a collapse of the ground surface. The thickness of coal mined was about 8 feet according to historical records. The total thickness of the No. 3 Coal Seam is about 12 feet. Based on our review of the previously-referenced available information and site observations, the original main slope coal mine entries (referred to as the “Main Entry” and “Fan House” for the Renton Mine) are located about 170 feet south of the central portion of the Merlino Property’s south property line as shown on Figure 2. As the mine expanded, a rock tunnel was driven from the main slope west- northwest to a point along the east side of the current location of Benson Road (a road that lies along the base of the hill adjacent to the current location of Sam’s Club). The rock tunnel provided an easier means for removing coal from the underground mine workings. The rock tunnel crosses under the WSDOT property to the south of the Merlino Property and extends west-northwest under I-405, as shown on Figure 2, to where the backfilled (currently inaccessible) mine entry to the west is located. The location of that mine entry is not shown on Figure 2 as it is west-northwest of the mapped area. The mine workings extend north-northeast and east from the rock tunnel at an approximately 10 degree angle below horizontal with a series of haulageways and production or room areas that were driven at right angles to the main slope. Each haulageway along with its production area was referred to as a “Level.” Underlying a portion of the southeast part of the Merlino Property in the vicinity of the south end of Cedar Avenue South is the 1st Level of the Renton Mine. The Renton Mine ultimately contained 12 levels extending underground a distance of over 1 mile east of the south end of the Merlino Property. 5.2.2 Undocumented Mining The Renton Mine is located in an area where undocumented mining occurred. We observed no evidence of undocumented mining during our field reconnaissance and observation efforts within the Merlino Property or its immediate vicinity. 5.3 2009 GROUND-PROOFING PROGRAM SUMMARY Subsurface conditions in the area of the south end of Cedar Avenue South (High Coal Mine Hazard Area) were explored by drilling seven, three-inch-diameter borings (Borings B-5 through B-11) at the approximate locations shown on Figure 2. Exploration locations were established by measuring from physical features at the site. The number of borings was determined such that the probability of drilling through “support pillars” was reduced to a very low level. The borings were drilled on April 27, 2009 to depths ranging from 53 to 84 feet below the ground surface in the area likely underlain by a portion of the 1st Level of the Renton Mine. The borings were advanced using track-mounted, hydraulic/air- percussion drilling equipment owned and operated by McCallum Rock Drilling, Inc. of Chehalis, Washington. Borings B-5, B-10 and B-11 were drilled at a vertical orientation. Borings B-6 through B-9 were drilled at an angle (varying from 25 to 30 degrees off of vertical) from the surface location of Boring B-5. The purpose of drilling the angle borings was to evaluate the conditions of the Renton Mine and the No. 3 Coal Seam in areas that were otherwise inaccessible. Soil and bedrock samples (drill cuttings) were observed continuously as the borings were advanced. The subsurface explorations were continuously logged by a geological engineer from our firm. Soils were classified in general accordance with ASTM Test Method D 2488 as shown on the Explanation for Boring Merlino Land Development Co., Inc. Attn: Gary Merlino April 23, 2014 Page 5 I c i c l e C r e e k E n g i n e e r s 0864001/042314 Logs, Figure 4. Bedrock was classified in general accordance with the WSDOT Geotechnical Design Manual. The boring logs are presented in Figures 5 through 11. The borings for this study were supplemented by three test borings (Borings B-1 through B-3) that were previously completed by ICE for GWC (ICE, June 10, 2005). The locations of these supplemental borings are shown on Figure 2. Boring B-4 (not shown on Figure 2) was completed for GWC on a nearby property and into a different coal seam (No. 2 Coal Seam) not related to this project. The logs of Borings B-1 through B-3 are included in Attachment B. A summary of the subsurface conditions observed in the current and supplemental borings is presented below. Test Boring Number Total Depth (feet) Depth to Bedrock (feet) Depth to Coal Seam/Mine (feet) Uncollapsed (full height mine void) Unmined (intact coal) Thickness Intact Coal (feet) B-1 (2005) 110 7 7 - Yes 12 B-2 (2005) 60 8 8 - Yes 11½ B-3 (2005) 60 10 10 - Yes 13½ B-5 (2009) 71 5 57 - Yes 13 B-6 (2009) 77 6 65 12-foot void No - B-7 (2009) 53 6 39 14-foot void No - B-8 (2009) 83 6 51 - Yes 15 B-9 (2009) 84 6 59 - Yes 14 B-10 (2009) 59 5 36 - Yes 13 B-11 (2009) 59 5 41 - Yes 11 Note: The thickness of void indicated is not corrected for drilling at an angle; the actual thickness of void is likely 2 to 3 feet less than that indicated by the drilling penetration. Borings B-1 through B-3 encountered the top of the No. 3 Coal Seam (intact – not mined) immediately below the overburden soils at a depth ranging from 7 to 10 feet below the ground surface. Borings B-5 through B-11 encountered about 5 to 6 feet of overburden soils. Borings B-5 through B-11 encountered a 3- to 5-foot thick layer of carbonaceous shale overlying the No. 3 Coal Seam or Renton Mine, which is generally overlain by sandstone. Borings B-5 and B-7 through B-11 encountered sandstone underlying the No. 3 Coal Seam. We encountered “intact bedrock” at the base of the Renton Mine void in Borings B-6 and B-7, but were unable to observe drill cuttings because of the loss of air circulation caused by the void. No groundwater was observed in Borings B-1 through B-3 or Borings B-5 through B-11 at the time of drilling. 5.4 GENERAL DESCRIPTION OF HAZARDS ASSOCIATED WITH COAL MINES The principal physical hazards associated with abandoned underground coal mines include the following: Sinkholes (High Coal Mine Hazard Areas) Regional ground subsidence (Medium Coal Mine Hazard Areas) Merlino Land Development Co., Inc. Attn: Gary Merlino April 23, 2014 Page 6 I c i c l e C r e e k E n g i n e e r s 0864001/042314 5.5 THE CITY OF RENTON’S DEFINITIONS OF THREE CLASSES OF COAL MINE HAZARD AREAS RMC 4-3-050J.1.e defines coal mine hazards as follows: High Coal Mine Hazards - Areas with abandoned and improperly sealed mine openings and areas underlain by mine workings shallower than two hundred feet (200') in depth for steeply dipping seams, or shallower than fifteen (15) times the thickness of the seam or workings for gently dipping seams. These areas may be affected by collapse or other subsidence. Medium Coal Mine Hazards – Areas where the mine workings are deeper than two hundred feet (200’) for steeply dipping seams, or deeper than fifteen (15) times the thickness of the seam for gently dipping seams. These areas may be affected by subsidence. Low Coal Mine Hazards – Areas with no known mine workings and no predicted subsidence. While no mines are known in these areas, undocumented mining is known to have occurred. 6.0 ANALYSIS OF COAL MINE HAZARDS 6.1 HIGH COAL MINE HAZARD AREAS As previously mentioned, the goal of ICE’s 2009 ground-proofing program was to further evaluate the location and coal seam/mine condition within the Merlino Property. Our June 2005 report completed for GWC includes three test borings (Borings B-1, B-2, and B-3) within the Merlino Property; seven additional test borings (Borings B-5 through B-11) within the Merlino Property and within the adjacent south end of the Cedar Avenue South right-of-way were completed in 2009. These boring locations are shown on Figure 2. Based on the results of these explorations, we were able to accurately locate the 1st Level of the Renton Mine (encountered in Borings B-6 and B-7) and also locate intact coal, commonly referred to as a “barrier pillar,” that was left in place to protect the ground surface. It appears that the 1st Level of the Renton Mine is located about 30 feet east and about 25 feet south of the location shown in ICE’s June 2005 report. Our reinterpretation of the High Coal Mine Hazard Area at the Merlino Property, which is based on Borings B-5 through B-11, is shown on the Coal Mine Hazard Map, Figure 3. 6.2 MEDIUM COAL MINE HAZARD AREAS No ground subsidence should occur outside of the High Coal Mine Hazard Area because it appears (based on ground proofing) to be underlain by intact coal (a barrier pillar) that was left in-place to protect the ground surface. No Medium Coal Mine Hazard Areas exist outside of the High Coal Mine Hazard area within the Merlino Property or within adjacent Cedar Avenue South. 6.3 LOW COAL MINE HAZARD AREAS Based on our site observations in 2009 and 2014, and review of the regional mapping of coal mine hazards by the City of Renton, portions of this area are where no known mine workings occur and no predicted subsidence is probable. Although undocumented coal mining could have occurred in this area, no evidence was observed during our reconnaissance efforts completed for this study. The Low Coal Mine Hazard Area within the Merlino Property and within abutting Cedar Avenue South is shown on Figure 3. Merlino Land Development Co., Inc. Attn: Gary Merlino April 23, 2014 Page 7 I c i c l e C r e e k E n g i n e e r s 0864001/042314 7.0 CONCLUSIONS Based on our review of available information, site observations, ground proofing and analysis of coal mine hazards within the Merlino Property and Cedar Avenue South, we have developed the following conclusions: The results of our ground-proofing program (Borings B-5 through B-11) suggest that the 1st Level of the Renton Mine is situated slightly east (about 30 feet) and south (about 25 feet) of the location indicated in ICE’s June 2005 report. Borings B-6 and B-7 encountered uncollapsed mine workings (1st Level, Renton Mine, No. 3 Coal Seam) at depths of 65 feet and 39 feet, respectively. At these depths, a portion of the Renton Mine is located beneath the southeast corner of the Merlino Property at the south end of Cedar Avenue South. Borings B-5 and B-8 through B-11 encountered intact coal (unmined No. 3 Coal Seam), indicating a barrier pillar that was left in-place to protect the ground surface from subsidence. The presence of the intact coal (barrier pillar) is consistent with the results of Borings B-1 through B-3 that were completed to the west and north of the south end of Cedar Avenue South (ICE, June 2005). Based on the results of Borings B-5 through B-11, we conclude that the High Coal Mine Hazard Area should be delineated as shown on Figure 3. Other areas that were previously delineated as a High Coal Mine Hazard Area in ICE’s June 2005 report should be reclassified as a Low Coal Mine Hazard Area. The Medium Coal Mine Hazard Area is included (subsumed) within the High Coal Mine Hazard Area. None of the proposed seven lots lie within the High Coal Mine Hazard Area or within the Medium Coal Mine Hazard Area as shown on Figure 3. Most of the area of Cedar Avenue South proposed to be widened lies outside of the High Coal Mine Hazard Area as shown on Figure 3. Based on our site observations in 2009 and 2014, and knowledge of the location of the Renton Mine, Low Coal Mine Hazard Areas are shown on Figure 3. 8.0 RECOMMENDATIONS No structures should be constructed in High Coal Mine Hazard Areas. In our opinion, fill may be placed in High Coal Mine Hazard Areas provided that the fill is not used to support structures. The stormwater vault and underground pipes could be supported by a deep foundation that extends below the underground mine, or structurally designed to span a void of 10 feet in diameter along with the drag forces caused by caving soils around these structures should a sinkhole occur. Manholes would need to be structurally supported on the side of the vault. Road access, including fill placement for road access (no cuts), may be constructed in the High Coal Mine Hazard Areas. 9.0 USE OF THIS REPORT We have prepared this report for use by Merlino Land Development Co., Inc. The data and report should be used for land use planning, but our report, conclusions and interpretations should not be construed as a warranty of subsurface conditions. There are probable variations in subsurface conditions between the explorations; variation in subsurface conditions may also occur with time. A contingency for unanticipated conditions should be included in the short plat infrastructure construction’s budget and schedule. During construction, sufficient observation, testing and consultation by our firm should be provided to (1) evaluate whether the Merlino Land Development Co., Inc. Attn: Gary Merlino April 23, 2014 Page 8 I c i c l e C r e e k E n g i n e e r s 0864001/042314 conditions encountered are consistent with those indicated by the explorations, (2) provide recommendations for design changes if the conditions encountered during construction differ from those anticipated, and (3) evaluate whether earthwork activities comply with contract plans and specifications. Within the limitations of scope, schedule and budget, our services have been executed in accordance with generally accepted practices in this area at the time the report was prepared. No warranty or other conditions, express or implied, should be understood. ******************* We trust this information meets your present needs. If you have any questions or if we can be of further assistance to you, please call. Yours very truly, Icicle Creek Engineers, Inc. Brian R. Beaman, PE, LEG, LHG Principal Engineer/Geologist/Hydrogeologist Kathy S. Killman, LEG Principal Engineering Geologist Document ID: 0864001.CMH.Report Attachments: Vicinity Map – Figure 1 Site Plan – Figure 2 Coal Mine Hazard Map – Figure 3 Explanation for Boring Logs – Figure 4 Boring Logs – Figures 5 through 11 Attachment A – I-405 CDB Technical Memorandum, August 14, 2009 Attachment B – Supplemental Boring Logs Submitted via surface mail (three original copies) cc: David Halinen, Halinen Law (email as pdf, surface mail – one original copy) I c i c l e C r e e k E n g i n e e r s 0864001/042314 FIGURES 0 ICE FILE NUMBERIcicle Creek Engineers, Inc. 29335 NE 20th Street Carnation, Washington 98014 (425) 333-0093 FigureCHECKED: KSK DRAWN: BRB DESIGNED: --- SCALE: As Shown DATE: April 23, 2014 MERLINO SHORT PLAT - PROPOSED 7-LOT RESIDENTIAL DEVELOPMENT RENTON, WASHINGTON VICINITY MAP 1 0864-001 2,0000 4,000BensonRoadBensonRoadMerlino Property Approximate Scale in Feet ICE FILE NUMBERIcicle Creek Engineers, Inc. 29335 NE 20th Street Carnation, Washington 98014 (425) 333-0093 Figure 0864-001 CHECKED: KSK DRAWN: BRB DESIGNED: --- SCALE: 1 inch - 100 feet DATE: April 23, 2014 MERLINO SHORT PLAT - PROPOSED 7-LOT RESIDENTIAL DEVELOPMENT RENTON, WASHINGTON Base map provided by Core Design, undated Cedar Avenue SouthSouth 7th StreetProposed Right-of-Way Line Existing Right-of-Way Line Merlino Property WSDOT Property 180 Borings B-5 through B-9 were drilled from the same location; Boring B-5 was vertically oriented and Borings B-6 through B-9 were drilled at an angle varying from 25 to 30 degrees off of vertical. B-2(2005)B-2(2005) TP-5 B-1(2005)TP-6B-3(2005) TP-3 TP-4 TP-13TP-12 TP-2 TP-1 Mine Rock Fill (Coal Spoils) (based on 2005 field reconnaissance) removed or covered during I-405 expansion) EXPLANATION Backfilled Mine Opening Boring Location (2009) TP-1 Test Pit Location (2005) B-5 Boring Location (2005)B-3 B-5 B-6 B-7B-8 B-9 B-10 B-11 B-6 B-9 B-5 B-7B-8 B-10 B-11 Approximate Scale in Feet 0 100 200 TP-16 TP-14TP-14 TP-8 TP-7 TP-15 SITE PLAN Main Entry (backfilled mine opening - Renton Mine) Fan House (backfilled mine opening - Renton Mine) Renton Mine Rock Tunnel Area 2 ICE FILE NUMBERIcicle Creek Engineers, Inc. 29335 NE 20th Street Carnation, Washington 98014 (425) 333-0093 Figure 0864-001 CHECKED: KSK DRAWN: BRB DESIGNED: --- SCALE: 1 inch - 100 feet DATE: April 23, 2014 MERLINO SHORT PLAT - PROPOSED 7-LOT RESIDENTIAL DEVELOPMENT RENTON, WASHINGTON Base map provided by Core Design, undated Cedar Avenue SouthSouth 7th StreetProposed Right-of-Way Line Existing Right-of-Way Line Merlino Property WSDOT Property EXPLANATION High Coal Mine Hazard Area Areas with abandoned and improperly sealed mine openings and areas underlain by mine workings shallower than 200 feet in depth (RMC 4-3-050J.1.e.iii.). No structures should be planned in this area; fill placement is OK. Low Coal Mine Hazard Area Areas with no known mine workings and no predicted subsidence J.1.e.i.). Building and road development should be allowed; no mitigation recommended. (RMC 4-3-050 COAL MINE HAZARD MAP Approximate Scale in Feet 0 100 200 3 MAJOR DIVISIONS Soil Classification and Generalized Group Description Coarse- Grained Soils More than 50% retained on the No. 200 sieve Fine- Grained Soils More than 50% passing the No. 200 sieve Highly Organic Soils GRAVEL More than 50% of coarse fraction retained on the No. 4 sieve SAND More than 50% of coarse fraction passes the No. 4 sieve SILT AND CLAY Liquid Limit less than 50 SILT AND CLAY Liquid Limit greater than 50 CLEAN GRAVEL GRAVEL WITH FINES CLEAN SAND SAND WITH FINES INORGANIC ORGANIC INORGANIC ORGANIC GW GP GM GC SW SP SM SC ML CL OL MH CH OH PT Well-graded gravels Poorly-graded gravels Gravel and silt mixtures Gravel and clay mixtures Well-graded sand Poorly-graded sand Sand and silt mixtures Sand and clay mixtures Low-plasticity silts Low-plasticity clays Low plasicity organic silts and organic clays High-plasticity silts High-plasticity clays High-plasticity organic silts and organic clays PeatPrimarily organic matter with organic odor Unified Soil Classification System Component Size Range Boulders Coarser than 12 inch Cobbles 3 inch to 12 inch Gravel 3 inch to No. 4 (4.78 mm) Coarse 3 inch to 3/4 inch Fine 3/4 inch to No. 4 (4.78 mm) Sand Coarse No. 4 (4.78 mm) to No. 200 (0.074mm) No. 4 (4.78 mm) to No. 10 (2.0 mm) Medium No. 10 (2.0 mm) to No. 40 (0.42 mm) Fine No. 40 (0.42 mm) to No. 200 (0.074 mm) Silt and Clay Finer than No. 200 (0.074 mm) Soil Particle Size Definitions Soil Moisture Description Dry Moist Wet Absence of moisture Damp, but no visible water Visible water Soil Moisture ModifiersNotes: 1) Soil classification based on visual classification of soil is based on ASTM D2488. 2) Soil classification using laboratory tests is based on ASTM D2487. 3) Description of soil density or consistency is based on interpretation of blow count data and/or test data. Sampling Method Boring Log Symbol Description Blows required to drive a 2.4 inch I.D. split-barrel sampler 12-inches or other indicated distance using a 300-pound hammer falling 30 inches. Blows required to drive a 1.5- inch I.D. split barrel sampler (SPT - Standard Penetration Test) 12-inches or other indicated distance using a 140-pound hammer falling 30 inches. 34 12 21 14 30 P Location of relatively undisturbed sample Location of disturbed sample Location of sample attempt with no recovery Location of sample obtained in general accordance with Standard Penetration Test (ASTM D-1586) test procedures. Location of SPT sampling attempt with no recovery. Pushed Sampler Grab Sample Sampler pushed with the weight of the hammer or against weight of the drilling rig. Sample obtained from drill cuttings.G Key to Boring Log Symbols Test Symbol Density Grain Size Percent Fines Atterberg Limits Hydrometer Analysis Consolidation Compaction Permeability Unconfined Compression Consolidated Undrained TX Consolidated Drained TX Chemical Analysis Laboratory Tests DN GS PF AL HA CN CP PM UC CU CD CA Unconsolidated Undrained TX UU Note: The lines separating soil types on the logs represents approximate boundaries only. The actual boundaries may vary or be gradual. Moisture Content MC ICE FILE NUMBERIcicle Creek Engineers, Inc. 29335 NE 20th Street Carnation, Washington 98014 (425) 333-0093 FigureCHECKED: KSK DRAWN: BRB DESIGNED: --- SCALE: N/A DATE: April 23, 2014 MERLINO SHORT PLAT - PROPOSED 7-LOT DEVELOPMENT RENTON, WASHINGTON EXPLANATION FOR BORING LOGS 4 0864-002 0 5 10 15 20 25 30 35 40 45 50 Soil/Rock Profile Description Graphic Log Depth in FeetApproximate Ground Surface Elevation: 200 feet Page 1 of 2 Boring Log - Figure 5 Comments Groundwater Observations 0 5 10 15 20 25 30 35 40 45 50Depth in FeetSoilClassificationSymbolSampleLocationIcicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB BRB: 04/29/09Rock Rock Rock Rock Rock SM Forest duff and topsoil Rock Bedrock encountered at 5 feet Brown silty fine to medium SAND (completely weathered bedrock) Brown medium-grained SANDSTONE (slightly weathered, very weak) (Renton Formation bedrock) Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Light brown medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Dark brown CARBONACEOUS SHALE (fresh, very weak) (Renton Formation bedrock) Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Rock Rock Rock Boring B-5 50 55 60 65 70 75 80 85 90 95 100 Soil/Rock Profile Description Graphic Log Depth in FeetBoring B-5 Page 2 of 2 Comments 50 55 60 65 70 75 80 85 90 95 100Depth in FeetSoilClassificationSymbolSampleLocationBoring Log - Figure 5 Groundwater Observations Icicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB BRB:04/29/09Boring completed at 71 feet on April 27, 2009 RockLight gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Dark brown CARBONACEOUS SHALE (fresh, very weak) (Renton Formation bedrock) Black COAL (fresh, very weak) (Renton Formation bedrock) Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) NO. 3 COAL SEAM (coal seam intact from 57 - 70 feet - not mined) Rock Rock Rock Rock No groundwater observed 0 5 10 15 20 25 30 35 40 45 50 Soil/Rock Profile Description Graphic Log Depth in FeetApproximate Ground Surface Elevation: 200 feet Page 1 of 2 Boring Log - Figure 6 Comments Groundwater Observations 0 5 10 15 20 25 30 35 40 45 50Depth in FeetSoilClassificationSymbolSampleLocationIcicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB JMS:04/30/09Rock Rock Rock Rock Rock Forest duff and topsoil Rock Bedrock encountered at 6 feet Brown silty fine to medium SAND (completely weathered bedrock) Brown medium-grained SANDSTONE (slightly weathered, very weak) (Renton Formation bedrock) Light brown medium-grained SANDSTONE (fresh, very weak) (Renton formation bedrock) Dark brown CARBONACEOUS SHALE (fresh, very weak) (Renton Formation bedrock) Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Rock Rock SM Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock)Rock Rock Boring B-6 (top hole location at Boring B-5 oriented o oat 25 from vertical at azimuth 090 ) 50 55 60 65 70 75 80 85 90 95 100 Soil/Rock Profile Description Graphic Log Depth in FeetBoring B-6 Page 2 of 2 Comments 50 55 60 65 70 75 80 85 90 95 100Depth in FeetSoilClassificationSymbolSampleLocationBoring Log - Figure 6 Groundwater Observations Icicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB JMS:04/30/09Boring completed at 77 feet on April 27, 2009 RockLight gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Dark brown CARBONACEOUS SHALE (fresh, very weak) (Renton Formation bedrock) RENTON MINE (open mine workings - uncollapsed) Rock Rock Void VoidVoid Void Complete loss of compressed air circulation at 65 feet Drilling resistance indicates intact rock (not mined) at 77 feet RENTON MINE (open from 65 - 77 feet - mined out) No groundwater observed 0 5 10 15 20 25 30 35 40 45 50 Soil/Rock Profile Description Graphic Log Depth in FeetBoring B-7 (top hole location at Boring B-5 oriented o oat 30 from vertical at azimuth 180 Approximate Ground Surface Elevation: 200 feet Page 1 of 2 Boring Log - Figure 7 Comments Groundwater Observations 0 5 10 15 20 25 30 35 40 45 50Depth in FeetSoilClassificationSymbolSampleLocationIcicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB JMS: 04/30/09Rock Rock Rock Rock Void Forest duff and topsoil Void Bedrock encountered at 6 feet Brown silty fine to medium SAND (completely weathered bedrock) Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Rock Rock SM Dark brown CARBONACEOUS SHALE (fresh, very weak) (Renton Formation bedrock) RENTON MINE (open from 39 - 53 feet - mined out) Complete loss of compressed air circulation at 39 feetRENTON MINE (open mine workings - uncollapsed) 50 55 60 65 70 75 80 85 90 95 100 Soil/Rock Profile Description Graphic Log Depth in FeetBoring B-7 Page 2 of 2 Comments 50 55 60 65 70 75 80 85 90 95 100Depth in FeetSoilClassificationSymbolSampleLocationBoring Log - Figure 7 Groundwater Observations Icicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB JMS:04/30/09Boring completed at 53 feet on April 27, 2009 Void RENTON MINE (open from 39 - 53 feet - mined out) Drilling resistance indicates intact rock (not mined) at 53 feet RENTON MINE (open mine workings - uncollapsed) No groundwater observed 0 5 10 15 20 25 30 35 40 45 50 Soil/Rock Profile Description Graphic Log Depth in FeetApproximate Ground Surface Elevation: 200 feet Page 1 of 2 Boring Log - Figure 8 Comments Groundwater Observations 0 5 10 15 20 25 30 35 40 45 50Depth in FeetSoilClassificationSymbolSampleLocationIcicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB JMS: 04/30/09Rock Rock Rock Rock Rock Forest duff and topsoil Rock Bedrock encountered at 6 feet Brown silty fine to medium SAND (completely weathered bedrock) Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) SM Rock Rock RockDark brown CARBONACEOUS SHALE (fresh, very weak) (Renton Formation bedrock) Boring B-8 (top hole location at Boring B-5 oriented o oat 30 from vertical at azimuth 000 ) 50 55 60 65 70 75 80 85 90 95 100 Soil/Rock Profile Description Graphic Log Depth in FeetBoring B-8 Page 2 of 2 Comments 50 55 60 65 70 75 80 85 90 95 100Depth in FeetSoilClassificationSymbolSampleLocationBoring Log - Figure 8 Groundwater Observations Icicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB JMS:04/30/09Boring completed at 83 feet on April 27, 2009 RockDark brown CARBONACEOUS SHALE (fresh, very weak) (Renton Formation bedrock) Black COAL (fresh, very weak) (Renton Formation bedrock) NO. 3 COAL SEAM (coal seam intact from 51 - 66 feet - not mined) Rock Rock Rock Rock Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Rock Rock Rock No groundwater observed 0 5 10 15 20 25 30 35 40 45 50 Soil/Rock Profile Description Graphic Log Depth in FeetApproximate Ground Surface Elevation: 200 feet Page 1 of 2 Boring Log - Figure 9 Comments Groundwater Observations 0 5 10 15 20 25 30 35 40 45 50Depth in FeetSoilClassificationSymbolSampleLocationIcicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB JMS: 04/30/09Rock Rock Rock Rock Rock SM Forest duff and topsoil Rock Bedrock encountered at 6 feet Brown silty fine to medium SAND (completely weathered bedrock) Light brown medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Light gray medium-grained SANDSTONE (slightly weathered bedrock, very weak) (Renton Formation bedrock) Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Rock Rock Rock Dark brown CARBONACEOUS SHALE (fresh, very weak) (Renton Formation bedrock) Rock Boring B-9 (top hole location at Boring B-5 oriented o oat 30 from vertical at azimuth 312 50 55 60 65 70 75 80 85 90 95 100 Soil/Rock Profile Description Graphic Log Depth in FeetBoring B-9 Page 2 of 2 Comments 50 55 60 65 70 75 80 85 90 95 100Depth in FeetSoilClassificationSymbolSampleLocationBoring Log - Figure 9 Groundwater Observations Icicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB JMS:04/30/09Boring completed at 84 feet on April 27, 2009 RockLight gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Dark brown CARBONACEOUS SHALE (fresh, very weak) (Renton Formation bedrock) Black COAL (fresh, very weak) (Renton Formation bedrock) NO. 3 COAL SEAM (coal seam intact from 59 - 73 feet - not mined) Rock Rock Rock Rock Rock Rock Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) No groundwater observed 0 5 10 15 20 25 30 35 40 45 50 Soil/Rock Profile Description Graphic Log Depth in FeetBoring B-10 Approximate Ground Surface Elevation: 186 feet Page 1 of 2 Boring Log - Figure 10 Comments Groundwater Observations 0 5 10 15 20 25 30 35 40 45 50Depth in FeetSoilClassificationSymbolSampleLocationIcicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB JMS: 04/30/09Rock Rock Rock Rock Rock Forest duff and topsoil Rock Bedrock encountered at 5 feet Brown silty fine to medium SAND (completely weathered bedrock) Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Rock Rock Rock SM Dark brown CARBONACEOUS SHALE (fresh, very weak) (Renton Formation bedrock) Black COAL (fresh, very weak) (Renton Formation bedrock) NO. 3 COAL SEAM (coal seam intact from 36 - 49 feet - not mined) Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock)Rock 50 55 60 65 70 75 80 85 90 95 100 Soil/Rock Profile Description Graphic Log Depth in FeetBoring B-10 Page 2 of 2 Comments 50 55 60 65 70 75 80 85 90 95 100Depth in FeetSoilClassificationSymbolSampleLocationBoring Log - Figure 10 Groundwater Observations Icicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB JMS:04/30/09Boring completed at 59 feet on April 27, 2009 RockLight gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Rock No groundwater observed 0 5 10 15 20 25 30 35 40 45 50 Soil/Rock Profile Description Graphic Log Depth in FeetBoring B-11 Approximate Ground Surface Elevation: 185 feet Page 1 of 2 Boring Log - Figure 11 Comments Groundwater Observations 0 5 10 15 20 25 30 35 40 45 50Depth in FeetSoilClassificationSymbolSampleLocationIcicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB JMS: 04/30/09Rock Rock Rock Rock Rock Forest duff and topsoil Rock Bedrock encountered at 5 feet Brown silty fine to medium SAND (completely weathered bedrock) Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Rock Rock Rock SM Dark brown CARBONACEOUS SHALE (fresh, very weak) (Renton Formation bedrock) Black COAL (fresh, very weak) (Renton Formation bedrock) NO. 3 COAL SEAM (coal seam intact from 41 - 52 feet - not mined) 50 55 60 65 70 75 80 85 90 95 100 Soil/Rock Profile Description Graphic Log Depth in FeetBoring B-11 Page 2 of 2 Comments 50 55 60 65 70 75 80 85 90 95 100Depth in FeetSoilClassificationSymbolSampleLocationBoring Log - Figure 11 Ground Water Observations Icicle Creek Engineers See Figure 4 for explanation of symbols ICE Project No. 0864-001Project Name: I-405 PropertyLogged by: BRB JMS:04/30/09Boring completed at 59 feet on April 27, 2009 Rock Light gray medium-grained SANDSTONE (fresh, very weak) (Renton Formation bedrock) Rock Black COAL (fresh, very weak) (Renton Formation bedrock) NO. 3 COAL SEAM (coal seam intact from 41 - 52 feet - not mined) No groundwater observed I c i c l e C r e e k E n g i n e e r s 0864001/042314 ATTACHMENT A I-405 CORRIDOR DESIGN BUILDERS TECHNICAL MEMORANDUM DATED AUGUST 14, 2009 I-405 RENTON STAGE 2 DESIGN/BUILD PROJECT WSDOT EXCHANGE PROPERTY REINFORCED SOIL SLOPE GEOTECHNICAL DESIGN RECOMMENDATIONS MEMORANDUM REV 0 RTN/RS2_EXCHANGEPOPERTY_RSS_DESIGNRECOMMENDATIONS_REV0_081409.DOC 2 COPYRIGHT 2009 BY I-405 CORRIDOR DESIGN BUILDERS • COMPANY CONFIDENTIAL Subsurface Conditions Geotechnical conditions for the WSDOT Exchange Property area were established on the basis of existing geotechnical explorations supplemented by 3 new explorations advanced by Icicle Creek Engineers in support of the Renton Stage 2 Project. The new boring logs were used with the existing site soil information to develop geotechnical parameters for analysis and design of RSS slope. Geotechnical Explorations The following exploration locations were used in the evaluation of the site conditions and in the creation of soil profiles beneath the RSS. The boring and test pit logs were also used to develop geotechnical parameters for analysis and design of the RSS. The source of the exploration information is summarized in Table 1. Figure 2 shows the approximate locations of the explorations. Figure 3 shows the interpreted typical subsurface. Copies of the exploration logs are included in Attachment B. TABLE 1: WSDOT EXCHANGE PROPERTY EXPLORATION LOCATIONS Exploration Location Type Source B-1 Boring Icicle Creek Engineers, Inc., 2005 B-2 Boring Icicle Creek Engineers, Inc., 2005 B-3 Boring Icicle Creek Engineers, Inc., 2005 TP-1 Test pit Icicle Creek Engineers, Inc., 2005 TP-2 Test pit Icicle Creek Engineers, Inc., 2005 TP-3 Test pit Icicle Creek Engineers, Inc., 2005 TP-4 Test pit Icicle Creek Engineers, Inc., 2005 TP-5 Test pit Icicle Creek Engineers, Inc., 2005 TP-6 Test pit Icicle Creek Engineers, Inc., 2005 TP-7 Test pit Icicle Creek Engineers, Inc., 2005 TP-8 Test pit Icicle Creek Engineers, Inc., 2005 TP-12 Test pit Icicle Creek Engineers, Inc., 2005 TP-13 Test pit Icicle Creek Engineers, Inc., 2005 TP-14 Test pit Icicle Creek Engineers, Inc., 2005 TP-15 Test pit Icicle Creek Engineers, Inc., 2005 TP-16 Test pit Icicle Creek Engineers, Inc., 2005 515-4-06 Boring Geoengineers, 2007 CDB-6p-08 Boring Geoengineers, 2007 SRX-20-05 Boring Geoengineers, 2007 REV 0 RTN/RS2_EXCHANGEPOPERTY_RSS_DESIGNRECOMMENDATIONS_REV0_081409.DOC 3 COPYRIGHT 2009 BY I-405 CORRIDOR DESIGN BUILDERS • COMPANY CONFIDENTIAL TABLE 1: WSDOT EXCHANGE PROPERTY EXPLORATION LOCATIONS Exploration Location Type Source 515-6-06 Boring Geoengineers, 2007 515-7-06 Boring Geoengineers, 2007 B-5 Boring Icicle Creek Engineers, Inc., 2009 B-10 Boring Icicle Creek Engineers, Inc., 2009 B-11 Boring Icicle Creek Engineers, Inc., 2009 Icicle Creek Engineers, Inc., “Report- Coal Mine Hazard Assessment and Preliminary Geotechnical Evaluation, Renton Hill Property, King County Parcel Nos. 2023059085 and 0007200194/196, Renton, Washington,” June 10, 2005. GeoEngineers, 2007, “Geotechnical Baseline Report I-405/1-5 to SR 169 Stage 2 – Widening and SR 515 Interchange, Renton, Washington,” September 7, 2007. Icicle Creek Engineers, Inc., “Report, Geological Engineering Services, Coal Mine Hazard Assessment, WSDOT Property, Renton, Washington,” May 11, 2009. Interpreted Geotechnical Conditions and Groundwater Location The existing WSDOT Exchange property is an undeveloped parcel of land located on the hillside between I-405 and Cedar Avenue. Slopes vary from 5 to over 90 percent, with slope lengths varying from 25 to over 100 feet. The site elevation varies from approximately 140 feet to 230 feet. The general subsurface profile consists of colluvium/fill overlying residual soils weathered from the Renton Formation overlying the Renton Formation. The colluvium/fill/residual soils are difficult to distinguish from each other and are considered as one unit for the analysis. The site is underlain by the Renton Formation sandstone bedrock. In the southwest portion of the site there are deposits of materials consisting of mine tailings and old municipal waste that are associated with the abandoned Renton Civic Dump site. The general characteristics of the predominant geologic units are as follows: • The colluvium/fill/residual soils vary from ~1 foot to 10 feet thick over the site. These soils are generally medium dense and consist primarily of silty sand. • The tailings/municipal waste thickness varies from a thin veneer to over 25 feet thick. These soils are loose to medium dense and contain a wide variety of materials including silt, sand, slag, ashes, glass, metal, debris, and other materials associated with municipal waste disposal. Mine tailings may also be incorporated in this material, either as cover soils, or as a result of previous mining activities that occurred in the same area. • The Renton Formation consists of weak sandstone bedrock with occasional siltstone layers and extends below the depth explored with borings at the site. Boring log information indicates that groundwater was found generally in the Renton Formation, below elevation 100 feet. REV 0 RTN/RS2_EXCHANGEPOPERTY_RSS_DESIGNRECOMMENDATIONS_REV0_081409.DOC 4 COPYRIGHT 2009 BY I-405 CORRIDOR DESIGN BUILDERS • COMPANY CONFIDENTIAL Seismicity and Ground Motions The Renton Stage 2 Project is being designed in accordance with WSDOT’s current seismic design requirements. These requirements include use of a design earthquake that has a 7 percent probability of exceedance in a 75-year exposure period. The seismic ground motions and liquefaction potential for this design earthquake are summarized below. Seismic Ground Motions Design peak ground acceleration (PGA) of 0.44g is used in analysis. This ground motion was determined using the AASHTO ground motions hazard map and a site coefficient for peak ground acceleration (Fpga) of 1.0 based on Site Class C site classification. Per the WSDOT GDM (2008), a horizontal pseudo-static acceleration coefficient, kh = 0.22 (F*PBA/2) was used in the global stability analysis. Use of this reduced seismic coefficient implies that several inches of permanent slope displacement is acceptable during the design seismic event. Liquefaction Potential Soils at the project site below the water table are the sandstone bedrock; therefore, liquefaction potential of site soils is very low. Surface water will be routed from the RSS and fill to prevent infiltration and possible ponding of water within the compacted fill layers and RSS. Geotechnical Design The design of RSS follows the steps outlined in Chapter 7 of FHWA Publication FHWA- NHI-00-043, “Mechanically Stabilized Earth Walls and Reinforced Soil Slopes Design and Construction Guidelines,” by Elias, et al. (2001). General Design Considerations The general design considerations for this project are listed below. • Traffic Surcharge assumed equivalent to 2.0 feet of soil surcharge (surcharge unit weight = 125 pcf) = 125 pcf x 2 feet = 250 psf. • Extensible (geosynthetic geogrid) reinforcement is to be used. • A wrapped face is not required because the slope is shallower than 1.2(H):1(V) (GDM, 2008). • Minimum length of reinforcing is 6 feet (GDM, 2008). • Primary reinforcing shall be vertically spaced at 3 feet or less (GDM, 2008). • Minimum long-term allowable strength of primary reinforcing = 1,250 lb/ft. REV 0 RTN/RS2_EXCHANGEPOPERTY_RSS_DESIGNRECOMMENDATIONS_REV0_081409.DOC 5 COPYRIGHT 2009 BY I-405 CORRIDOR DESIGN BUILDERS • COMPANY CONFIDENTIAL • Secondary reinforcing between layers of primary reinforcing shall be at a maximum vertical spacing of 1 foot (GDM, 2008). Secondary reinforcing shall not be included in the internal stability analysis of the RSS. • Minimum long-term allowable strength of secondary reinforcing = 115 lb/in. • Backfill within the reinforced zone of the RSS shall consist of Common Borrow, meeting the requirements of WSDOT Standard Specifications Section 9-03.14(3), as modified in the Project Technical Specification drafted for the RSS. As follows: Sieve Size Percent Passing 3-inch 100 No. 4 100 - 20 No. 200 0 - 35 Geotechnical Material Properties The following properties were used in the design of the RSS: New Fill: • Unit weight = 130 pcf • Internal angle of friction = 36 degrees • Cohesion (static case) = 0 psf • Internal angle of friction (seismic case) = 34 degrees • Apparent cohesion (seismic case) = 200 psf Residual soil/colluvium/fill: • Unit weight = 130 pcf • Internal angle of friction = 36 degrees • Cohesion (static case) = 0 psf • Apparent cohesion (seismic case) = 200 psf Renton Formation: • Uniaxial compressive strength = 300 psi (43.2 ksf) • Geologic strength index (GSI) = 40 • Intact rock constant (mi) for sandstone = 17 • Disturbance factor (D) for good quality excavation = 0.0 • Mohr-Coulomb fit (Hoek-Brown Criteria), internal angle of friction = 32 degrees • Mohr-Coulomb fit (Hoek-Brown Criteria), cohesion (seismic and static cases) = 2100 psf Municipal Waste: • Unit weight = 115 pcf • Internal angle of friction = 28 degrees • Cohesion (static case) = 300 psf • Apparent cohesion (seismic case) = 300 psf REV 0 RTN/RS2_EXCHANGEPOPERTY_RSS_DESIGNRECOMMENDATIONS_REV0_081409.DOC 6 COPYRIGHT 2009 BY I-405 CORRIDOR DESIGN BUILDERS • COMPANY CONFIDENTIAL Reinforcement Length Requirements Analyses were conducted at selected sections along the RSS to evaluate the minimum reinforcement lengths (Lmin) required to satisfy stability requirements. The analytical results were compared to GDM minimum acceptable criteria shown below. • Sliding FS 1.5 • Global Stability (outside of reinforced zone) FS 1.5 • Compound Failure (through face of RSS) FS 1.5 • Internal Slope Stability (through the reinforcing) FS 1.5 • Lateral Squeeze (bearing failure) FS 1.5 • Seismic Stability FS 1.1 The above factors of safety assume that structures (e.g., residences) will be constructed on the RSS fill in the future. For sliding, global stability, compound failure, internal stability, and seismic stability evaluations, the computer program SLIDE (Rocscience, 2008) was used. Lateral squeeze does not apply because the RSS is founded on competent bearing materials. To achieve the required FS, a geogrid with minimum long-term design strength of 1,250 lb/ft, coupled with the reinforcement lengths summarized in Table 2, is required. The length of reinforcing was generally controlled by a combination of static and seismic stability. The approximate station extents for the different Lmin are summarized in Table 2. All stations are based on a construction reference alignment CEDAR RW Line. For a given embankment location, all reinforcing lengths are constant for the entire embankment height. TABLE 2: REINFORCEMENT TABLE Beginning Station Ending Station Minimum Reinforcement Length (Lmin) Bottom Reinforcing Elevation (ft) Top Reinforcing Elevation (ft) 10+35 10+75 25 200 Varies, max 220 10+75 11+50 40 194 220 11+50 11+75 40 182 220 11+75 12+50 50 172 222 12+50 13+00 45 172 222 13+00 13+75 40 176 222 13+75 14+50 40 172 224 14+50 15+45 40 172 226 15+45 15+95 40 172 Varies, max 226 REV 0 RTN/RS2_EXCHANGEPOPERTY_RSS_DESIGNRECOMMENDATIONS_REV0_081409.DOC 7 COPYRIGHT 2009 BY I-405 CORRIDOR DESIGN BUILDERS • COMPANY CONFIDENTIAL Settlement Due to the granular consistency and/or heavily overconsolidated nature of the existing soils and bedrock, settlement is anticipated to be elastic in nature and is expected to occur during embankment construction. Construction Requirements The construction of the RSS and backfill require careful planning and construction control, including oversight by the project geotechnical engineer, to assure that the slope is constructed in such a manner that short- and long-term stability requirements are met. The following subsection summarizes key construction requirements. Specific requirements for construction of the RSS are included in the technical specification Reinforced Soil Slope, I.5:1 (Horizontal to Vertical) Slopes, included as Attachment C to this memorandum. Subgrade Preparation and Ground Improvement Before placement of fill or backfill for the RSS, all surface vegetation, topsoil, trash, construction debris, or other deleterious materials shall be removed from beneath the reinforced soil zone and properly disposed of offsite. Loose, soft, or wet material should also be removed and replaced with competent backfill. All sharp stone protrusions that could damage the reinforcing should also be removed. The subgrade within the footprint of the reinforced soil volume should be graded level as required for construction, proof rolled, and compacted to 95% of Standard Proctor Density (ASTM D698, AASHTO T99). Fill shall be keyed into the existing slope following Section 2- 03.3(14) “Hillside Terraces” of the Standard Specifications. Because of the variable nature of the site fill, field review and approval of the RSS subgrade and construction site preparation below the RSS by the project geotechnical engineer is required. Overexcavation may be required in areas where actual subgrade conditions do not meet the design recommendations. Depth and extent of overexcavation will be as directed by the geotechnical engineer. Fill and Backfill Requirements Backfill within the reinforced zone of the RSS shall consist of Common Borrow, meeting the requirements the RSS Project Technical Specification. The borrow source is expected to be the Renton Formation that is excavated to construct other project elements. The backfill material must be free of organics and other deleterious materials. The maximum particle size should be 3 inches. If wet-weather construction makes it difficult to achieve the required moisture and compaction density, Select Borrow (Section 9-03.14(2)) or Gravel Borrow (Section 9-03.14(1)) shall be used in lieu of Common Borrow. Backfill in the reinforced zone shall be placed in loose lifts of maximum 12-inch thickness and compacted to 95% of maximum density in accordance with the requirements of Section 2-03.3(14)C, Method C, of the WSDOT Standard Specifications and the project-specific technical specification (see Attachment C). REV 0 RTN/RS2_EXCHANGEPOPERTY_RSS_DESIGNRECOMMENDATIONS_REV0_081409.DOC 8 COPYRIGHT 2009 BY I-405 CORRIDOR DESIGN BUILDERS • COMPANY CONFIDENTIAL Backfill behind the reinforced zone shall be Common Borrow in accordance with the requirements of Section 9-03.14(3) of the Standard Specifications, provided that the material can be compacted in accordance with the requirements of Sections 2-03.3(14)C and 2- 03.3(14)D of the Standard Specifications. If wet-weather construction makes it difficult to achieve the required moisture and compaction density, Select Borrow (Section 9-03.14(2)) or Gravel Borrow (Section 9-03.14(1)) may be used in lieu of Common Borrow. Temporary Excavation Limited excavation may be required in order to construct the reinforced soil slope. Temporary excavations sloped to 1:1 should perform adequately during construction. If the Renton Formation bedrock is encountered in temporary excavations needed to place reinforcing grids, the lengths of the geogrid may be reduced, provided the project geotechnical engineer is notified in advance to verify subsurface conditions. In no case shall the reduced length of reinforcing be keyed into the Renton Formation less than 5 feet. Existing Utilities No known utilities cross beneath the proposed the RSS footprint. If any are encountered during construction, they should be brought to the attention of the project geotechnical engineer. In no case should the arrangement of slope reinforcing by modified to accommodate utilities without the approval of the project geotechnical engineer. Drainage and Erosion Control Temporary construction slopes shall direct water away from the RSS slope face to prevent erosion. The face of the RSS shall be stabilized following project temporary erosion and sediment control procedures and shall be planted with permanent vegetation in accordance with the project landscaping plans. References AASHTO (2002). Standard Specifications for Highway Bridges, 17th Edition (2002) – Allowable Stress Design. American Association of State Highway and Transportation Officials, 2002. AASHTO (2007). AASHTO LRFD Bridge Design Specifications, Fourth Edition. American Association of State Highway and Transportation Officials, 2007. FHWA (2001). Mechanically Stabilized Earth Walls and Reinforced Soil Slopes Design and Construction Guidelines. U.S. Department of Transportation, Federal Highway Administration. FHWA-NHI-00-043. March 2001. RocScience (2008). SLIDE Version 5.0 - User’s Manual. WSDOT (2008). Geotechnical Design Manual. Washington State Department of Transportation. WSDOT (2008). Standard Specifications for Road, Bridge, and Municipal Construction. Washington State Department of Transportation. M41-10. 90100100 100 100100100 110110 110 110 110 11 0120120 120120120 120 130 130 13 0 130 130 130 130140140140 140140140 150150 150 150 150 1 5 0 160160160 160 160 160 170 170 170 170 170 170 170180180 180 180 180180 190190 190 190 190 190200 200 200 200 200 200210 210 210 210 210210220 220 220 220 220 220230230230 230 230 230 240240240240 ROW CLF CLF 200 NO. Washington State Department of Transportation ISSUE DATE ISSUE RECORD - DESCRIPTION DESIGNED BY ENTERED BY CHECKED BY WASH10 NO.DESIGN MANAGER: DESIGN TASK LEAD: PACKAGE: REGION STATE CONTRACT NO. P.E. STAMP BOX DATEB07/29/09 K. LORENTSONFINAL DESIGN - 1B M. ROHILAC. HERMOGENES 08/14/09 K. LORENTSON M. ROHILAC. HERMOGENES0RELEASE FOR CONSTRUCTION - 1B WSDOT EXCHANGE PROPI-405 AND SR 515 INTERCHANGE STAGE 2 - WIDENING I-5 TO SR 169 SHEET OF SHEETS 7624_04_CG_1_01.dlv2:48:56 PM8/12/20097624 150 160 160 170170 170 180 180 180 190190 190200200 200210 210 220220 230 230230 1110 12 13 14 15 16 9 100101102103EE R.J NO RTHBOUND I-405 SOUTHBOUND I-405 J. BAUMAN K. LORENTSON SCALE IN FEET 0 30 60 A T. 23N. R. 5E. W.M. CG-0-02 CG-0-02 CEDAR RW LINE A S. FORMAN C. HERMOGENES CEDAR AVE S 1230 1230 B 06/19/09 PRELIMINARY DESIGN NB405 LINE SB405 LINE LEGEND 200 1.5:1CUT LINE CG-0-01 NOTES:2:12:11.5:11.5:12:1FILL LINE1.5:12:1 1.5:1 2:1 1.5:12:1 1 .5:1 2:11.5:12:1 1.5:1 CEDAR RW 10+91.62, 113.77’ RT ELEV 228.00 CEDAR RW 11+63.35, 113.00’ RT ELEV 230.00 CEDAR RW 12+86.86, 8.00’ LT ELEV 232.00 CEDAR RW 11+89.62, 8.00’ LT ELEV 230.00’ CEDAR RW 13+74.52, 114.82’ RT ELEV 234.00 CEDAR RW 14+69.96, 115.25’ RT ELEV 236.00 CEDAR RW 14+00.63, 8.00’ LT ELEV 234.00 CEDAR RW 15+39.28, 118.95’ RT ELEV 236.00 CEDAR RW 15+99.89, 0.00’ RT ELEV 238.00 CEDAR RW 14+97.08, 8.00’ LT ELEV 236.00 CONTOUR GRADING WSDOT EXCHANGE PROPERTY2:1CEDAR RW 12+60.26, 113.59’ RT ELEV 232.00 CEDAR RW 10+97.21, 10.78’ LT ELEV 228.00’ N1^26’53.75"E 2:1 A. BASTASCH DITCH, SEE DRAINAGE PLANS VARIES 2:1 MAX STREAM BUFFER THUNDER HILLS CREEK EXISTING MAJOR CONTOUR EXISTING MINOR CONTOUR PROPOSED MAJOR CONTOUR PROPOSED MINOR CONTOUR STREAM/ WETLAND BUFFER SLOPE ARROW LIMITED ACCESS WSDOT ROW AR LI NE 1. 2. 3. 4. ACCESS SEE CG-0-05 1.5:1 629 CEDAR AVE S CONDOMINIUMS FOR DITCH PROFILES, SEE DRAINAGE PLAN AND PROFILES. FOR SLOPE ROUNDING, SEE DLS-0-02. FOR REINFORCED SOIL SLOPE DETAILS, SEE SHEET CG-0-04. FOR EXISTING UTILITIES, SEE UTILITY PLANS. RFC - 1B E405 LINE LIMITS OF FILL WITHIN WSDOT RIGHT-OF-WAY NOT TO EXCEED SIX (6) FEET IN HEIGHT AND NOT TO ENCROACH OVER FILL LINE SHOWN Dense BrushTreesTreesTreesDense BrushBrushBrushBrushSSSSSSSSRandomSIGN Request 140780TR_SN_OverheadSignTR_SN_OverheadSignUTILITY Request 1TP_MM_UnknownObjectTP_MM_UnknownObjectRD_BR_BarrierFaceRD_BR_BarrierFace31379Copy of GEOTECH Request 1Random"EXIT 4""900 WEST""169 SOUTH"100100110110120120120130130130140140140 150150150160160160170170170180180180190190190200200200210210210220220220230230230240240240250250BL_LN_BreaklineGenericBL_LN_BreaklineGeneric1000Book 1BreaklineWSDOT EXCHANGE PROP!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>CEDAR AVENB I-405B-5B-3B-2B-1B-11B-10TP-8TP-7TP-6TP-5TP-4TP-3TP-2TP-1TP-16TP-15TP-14TP-13TP-12515-7-06515-6-06515-4-06SRX-20-05CDB-6p-08050 100 150 20025Feet³Figure 2: WSDOT Exchange PropertySubsurface Investigation Locations I c i c l e C r e e k E n g i n e e r s 0864001/042314 ATTACHMENT B SUPPLEMENTAL BORING LOGS 0 10 15 20 25 30 35 40 Soil/Rock Profile Description Graphic Log Depth in FeetBoring B-1 Approximate Ground Surface Elevation: 190 feet Icicle Creek Engineers Page 1 of 3 Boring Log - Figure A-2 Rock 5 Rock Rock Forest duff, topsoil and roots (drill cuttings)SM ICE File No. 0584-001Rock Rock Penetration Resistance(Blows/foot - ) 4020 60 80 Moisture Content (Percent - ) 20 40 60 80 LaboratoryTesting Installation - Ground Water Data Piezometer Soil-Bentonite BackfillGroupSymbolBlowCountSampleLocation5 Rock Rock RockLogged by: BRB/BES BRB:05/31/05Project Name: GWC, Inc., Renton Hill Property See Figure A-1 for explanation of symbols Bentonite Surface SealBrown fine SAND with silt (loose, moist) (drill cuttings) Black COAL (medium dense, moist) (Renton formation) (INTACT COAL - NO. 3 COAL SEAM - NOT MINED) occasional thin layers of carbonaceous shale grades to very dense Light-gray, fine-grained SANDSTONE (very dense, moist) (Renton formation) Brownish-gray , fine-grained SILTSTONE with thin layers of coal (Renton formation) Gray SILTSTONE (Renton formation) Black COAL (Renton formation) Grey SILTSTONE (Renton formation) SP-SM 20 63 50/6” 55 75 Soil Profile Description Graphic LogDepth in Feet20 40 60 80 20 40 60 80 Penetration Resistance(Blows/foot - ) Moisture Content (Percent - )LaboratoryTesting Piezometer Installation - Ground Water Data Boring B-1 Icicle Creek Engineers GroupSymbolBlowCountSampleLocationSample Data Page 2 of 3 45 65 See Figure A-1 for explanation of symbols Rock Soil-Bentonite Backfill 40 60 80 50 70 Rock Rock Rock Rock Rock Rock Rock Gray SILTSTONE (Renton formation)ICE File No. 0584-001Logged by: BRB/BES BRB:05/31/05Project Name: GWC, Inc., Renton Hill Property Boring Log - Figure A-2 Gray SILTSTONE with thin layers of coal (Renton formation) 95 115 Soil Profile Description Graphic LogDepth in Feet20 40 60 80 20 40 60 80 Penetration Resistance(Blows/foot - ) Moisture Content (Percent - )LaboratoryTesting Piezometer Installation - Ground Water Data Boring B-1 Icicle Creek Engineers GroupSymbolBlowCountSampleLocationSample Data Page 3 of 3 85 105 See Figure A-1 for explanation of symbols Soil-Bentonite Backfill 80 100 120 90 110 Rock Boring completed at 110 feet on May 4, 2005 Rock Gray SILTSTONE with thin layers of coal (Renton formation)ICE File No. 0584-001Logged by: BRB/BES BRB:05/31/05Project Name: GWC, Inc., Renton Hill Property Boring Log - Figure A-2 Gray SILTSTONE (Renton formation) Black COAL (Renton formation) Gray SILTSTONE (Renton formation) 0 10 15 20 25 30 35 40 Soil/Rock Profile Description Graphic Log Depth in FeetBoring B-2 Approximate Ground Surface Elevation: 190 feet Icicle Creek Engineers Page 1 of 2 Boring Log - Figure A-3 Rock 5 Rock Rock Forest duff, topsoil and roots (drill cuttings)SM ICE File No. 0584-001Rock Rock Penetration Resistance(Blows/foot - ) 4020 60 80 Moisture Content (Percent - ) 20 40 60 80 LaboratoryTesting Installation - Ground Water Data Piezometer Soil-Bentonite BackfillGroupSymbolBlowCountSampleLocation5 Rock Rock RockLogged by: BRB/BES BRB:05/31/05Project Name: GWC, Inc., Renton Hill Property See Figure A-1 for explanation of symbols Bentonite Surface SealSP-SM 26 34 50/5” Brown fine to medium SAND with silt and gravel (medium dense, moist) Black COAL (medium dense, moist) (Renton formation) (INTACT COAL - NO. 3 COAL SEAM - NOT MINED) occasional thin layers of carbonaceous shale grades to dense Light gray fine-grained SANDSTONE (very dense, moist) (Renton formation) Gray SILTSTONE (Renton formation) 78/9” 55 75 Soil Profile Description Graphic LogDepth in Feet20 40 60 80 20 40 60 80 Penetration Resistance(Blows/foot - ) Moisture Content (Percent - )LaboratoryTesting Piezometer Installation - Ground Water Data Boring B-2 Icicle Creek Engineers GroupSymbolBlowCountSampleLocationSample Data Page 2 of 2 45 65 See Figure A-1 for explanation of symbols Rock Soil-Bentonite Backfill 40 60 80 50 70 Rock Rock Rock Gray SILTSTONE (Renton formation)ICE File No. 0584-001Logged by: BRB/BES BRB:05/31/05Project Name: GWC, Inc., Renton Hill Property Boring Log - Figure A-3 Boring completed at 60 feet on May 5, 2005 Gray SILTSTONE with thin layers of coal (Renton formation) 0 10 15 20 25 30 35 40 Soil/Rock Profile Description Graphic Log Depth in FeetBoring B-3 Approximate Ground Surface Elevation: 200 feet Icicle Creek Engineers Page 1 of 2 Boring Log - Figure A-4 Rock 5 Rock Rock Forest duff, topsoil and roots (drill cuttings)SM ICE File No. 0584-001Rock Rock Penetration Resistance(Blows/foot - ) 4020 60 80 Moisture Content (Percent - ) 20 40 60 80 LaboratoryTesting Installation - Ground Water Data Piezometer Soil-Bentonite BackfillGroupSymbolBlowCountSampleLocation5 Rock Rock RockLogged by: BRB/BES BRB:05/31/05Project Name: GWC, Inc., Renton Hill Property See Figure A-1 for explanation of symbols Bentonite Surface SealSM 27 25 19 Brown silty fine SAND (medium dense, moist) Black COAL (medium dense, moist) (Renton formation) (INTACT COAL - NO. 3 COAL SEAM - NOT MINED) occasional thin layers of carbonaceous shale Light gray fine-grained SANDSTONE (very dense, moist) (Renton formation) 51 drill action indicates gravel from 7 to 10 feet Gray SILTSTONE (Renton formation) 55 75 Soil Profile Description Graphic LogDepth in Feet20 40 60 80 20 40 60 80 Penetration Resistance(Blows/foot - ) Moisture Content (Percent - )LaboratoryTesting Piezometer Installation - Ground Water Data Boring B-3 Icicle Creek Engineers GroupSymbolBlowCountSampleLocationSample Data Page 2 of 2 45 65 See Figure A-1 for explanation of symbols Rock Soil-Bentonite Backfill 40 60 80 50 70 Rock Rock Rock Gray SILTSTONE (Renton formation)ICE File No. 0584-001Logged by: BRB/BES BRB:05/31/05Project Name: GWC, Inc., Renton Hill Property Boring Log - Figure A-4 Boring completed at 60 feet on May 6, 2005 Brownish-gray SILTSTONE with thin layers of coal (Renton formation) Report Geotechnical Engineering Services Critical Areas Report Merlino Short Plat Proposed 7-Lot Residential Development Renton, Washington April 23, 2014 ICE File No. 0864-002 Prepared For: Merlino Land Development Co., Inc. Prepared By: Icicle Creek Engineers, Inc. April 23, 2014 Merlino Land Development Co., Inc. Attn: Gary Merlino 5050 1st Ave S, Suite 102 Seattle, Washington 98134-2400 Report Geotechnical Engineering Services Critical Areas Report Merlino Short Plat Proposed 7-Lot Residential Development Renton, Washington ICE File No. 0864-002 1.0 INTRODUCTION This report summarizes the results of Icicle Creek Engineers’ (ICE’s) geotechnical engineering services for a Critical Areas Report related to our evaluation of the Merlino Short Plat (referred to as the Merlino Property in this report) 7-Lot Residential Development located southwest of the intersection of South 7th Street and Cedar Avenue South in Renton, Washington. The Merlino Property is shown relative to nearby physical features on the Vicinity Map, Figure 1. The general layout of the Merlino Property is shown on the Site Plan, Figure 2. Our services were completed in general accordance with our Proposal dated January 31, 2014 and were authorized in writing by Gary Merlino of the Merlino Land Development Co., Inc. (MLDC) on January 31, 2014. 2.0 SCOPE OF SERVICES The purpose of our services was to review available geologic and geotechnical information and complete a site visit as a basis for evaluating Critical Areas (Geologic Hazards) consistent with the City of Renton Municipal Code (RMC) 4-3-050 (Critical Areas Regulations). Our evaluation of Critical Areas provides recommendations for mitigation, as appropriate, for these areas. Specifically, our services included the following: Review readily available information concerning project site topography, geology, soil conditions and other relevant site characteristics. Published materials include geologic maps prepared by the US Geological Survey and the Washington State Department of Natural Resources, and geotechnical reports prepared for the I-405 widening project. Complete a geologic reconnaissance of the property, with particular emphasis on Steep Slope (Protected Slope) areas. Evaluate the presence of Geologic Hazards including Steep Slopes (Protected and Sensitive Slopes), Coal Mine Hazards, Landslide Hazards, Erosion Hazards, Seismic Hazards, and Volcanic Hazards, as defined by the RMC. Merlino Land Development Co., Inc. Attn: Gary Merlino April 23, 2014 Page 2 I c i c l e C r e e k E n g i n e e r s 0864002/042314 Provide recommendations for the width(s) of a building setback from the top edge of the Protected Slope area, as appropriate. Provide recommendations for the mitigation for design of structures in Geologic Hazard areas (primarily Protected Slope), as appropriate. Evaluate risk associated with Geologic Hazards and the proposed development pursuant to RMC 4- 3-050J.2 3.0 BACKGROUND INFORMATION ICE previously completed coal mine hazard assessments of the subject property for a previous property owner, GWC, Inc. (GWC); the results of those assessments are presented in our reports dated January 17, 2005 and June 10, 2005. Those reports included what is currently the Merlino Property as well as additional property that GWC owned to the east and south of the southerly part of what is currently the Merlino Property. ICE also completed a hydrogeologic report for GWC dated March 24, 2006 and a geotechnical report for GWC dated September 30, 2005. In addition, ICE completed a coal mine hazard assessment of the Merlino Property; the results of that assessment are summarized in our report dated April 23, 2014. We understand that, subsequent to the reports we prepared in 2005 and 2006, GWC sold the portion of the GWC property that lies between Cedar Avenue South (and its southerly extension) and Interstate 405 (I-405) to the Washington State Department of Transportation (WSDOT) because preliminary plans for I-405 widening indicated encroachment into this property depending on final I-405 roadway configuration and the need for slope support measures. Thereafter, as part of the I-405 widening project, WSDOT’s design-build team for the I-405 widening project, I-405 Corridor Design Builders (CDB), placed excess soil that was excavated from an adjacent portion of the I-405 project onto what is now the Merlino Property (property that at the time was owned by WSDOT). The fill was designed as a Reinforced Soil Slope (RSS – the RSS is referred to as the “Engineered Fill” in the remainder of this report) by CDB (with CDB joint venturer CH2M Hill providing the I-405 project’s geotechnical engineering). David Halinen, attorney for MLDC, forwarded to ICE a copy of the CDB report entitled Technical Memorandum, I-405 Renton Stage 2 Design/Build Project, WSDOT Exchange Property Reinforced Soil Slope, Geotechnical Design Recommendations Memorandum, dated August 14, 2009, a technical memorandum that was prepared specifically for that Engineered Fill. That technical memorandum is attached to this report (Attachment A). Page 6 of the CDB Technical Memorandum states an assumption that “structures (e.g., residences) will be constructed on the Engineered Fill in the future” and noted that the factors of safety (FOS) used in the CDB Technical Memorandum were based on that assumption. For that purpose, CDB evaluated the stability of the Engineered Fill for sliding, global stability, compound failure, internal stability, and seismic stability. The final design of the Engineered Fill required a minimum FOS of at least 1.5 for all the factors evaluated. Mr. Halinen also arranged for ICE to review electronic copies of construction monitoring reports that were obtained by Chad Webley of Gary Merlino Construction Co., Inc. Based on our review of the construction monitoring reports, the construction monitoring was completed on a full-time basis by Mayes Testing Engineers, Inc. (Mayes) of Tacoma, Washington. We reviewed 39 Daily Field Reports (DFRs) that were prepared by Mayes dating from August 22 through October 19, 2009. Field density tests (FDTs) are included with 34 of the DFRs. Based on our review of the FDTs, a total of 109 in-situ field tests using a nuclear densometer were completed by Dan Quelhl of Mayes. It appears that T. Merlino Land Development Co., Inc. Attn: Gary Merlino April 23, 2014 Page 3 I c i c l e C r e e k E n g i n e e r s 0864002/042314 Bergstorm and Tom Robinson of Mayes filled-in for Mr. Quehl on at least three days. According to the FDT summary sheets, the fill that was placed on each specified day “meets compaction specifications” and/or “generally meets specifications as indicated by the test numbers.” Based on our review of the DFRs, Mayes was also checking to “assure that the proper type of Geogrid reinforcing was being used and was not damaged; assure the minimum embedment depth was attained according to approved plans & specs; and check that Geogrid was attached together with the subcontractor using twist ties” at the appropriate spacing. Mayes submitted a construction summary letter dated April 23, 2014 (signed and stamped by Michael S. Dolder, PE) for the Engineered Fill construction monitoring; that letter is included in this report as Attachment B. The Mayes summary letter states that “all work inspected was either (1) performed in accordance with or (2) corrected to conform to the I-405 Corridor Design Builder’s Geotechnical Design Recommendations Memorandum dated 8/14/09.” Based on information in the DFRs, it appears that the Engineered Fill mass was substantially completed by October 12, 2009. Based on (1) five Mayes DFRs that were completed after October 12, 2009 and (2) review of 108 date-stamped photographs from October 7 through November 3, 2009, final grading, cutting in and establishing ditchlines, and placement of erosion control fabric on slopes was being completed during that time period. In ICE’s June 2005 coal mine hazard assessment completed for GWC (an assessment that included 12 test pits and three test borings in the area of what is now the Merlino Property), we concluded that a “High Coal Mine Hazard Area” as defined in the RMC exists at the south end of Cedar Avenue South. Additional subsurface evaluation (seven test borings completed during 2009 and used for our current coal mine hazard assessment for the Merlino Property) targeted the High Coal Mine Hazard Area at the south end of Cedar Avenue South consistent with RMC 4-3-050J.1 (Geologic Hazards--Applicability) and RMC 4-3-050J.2 (Geologic Hazards--Special Studies Required). 4.0 PROJECT DESCRIPTION We understand that Core Design, Inc. has prepared a conceptual development plan of the Merlino Property dated March 19, 2014 that includes seven residential lots that are proposed to abut Cedar Avenue South’s west edge. The lots are positioned within the level, upper area (plateau) of the Engineered Fill. The west edge of all of the proposed lots is approximately located at the crest of the Engineered Fill. As part of the conceptual development plan, Cedar Avenue South is proposed to be widened along its west edge, with the widening to include construction of a cul-de-sac bulb at the south end. To construct the cul-de-sac bulb, a “sliver fill” and retaining wall up to about 6-feet thick/high will be required as shown on Figure 2. The sliver fill is to consist of a tapered thickness of soil fill (up to 6- feet thick) along the downhill side of the cul-de-sac where additional space is needed to provide the required radius for the cul-de-sac. An underground concrete stormwater vault is planned within the cul- de-sac bulb area. Water discharge from the stormwater vault will be to an existing rock-lined ditch that runs parallel to and along the north edge of a portion of the existing WSDOT gravel access road that extends toward WSDOT’s stream mitigation area on State-owned property to the south of the Merlino Property. 5.0 REGULATORY ISSUES 5.1 GENERAL Based on regional Critical Areas mapping by the City of Renton (City of Renton Map Gallery – Sensitive Areas) the Merlino Property contains Geologic Hazards including Steep Slopes (Protected and Sensitive Merlino Land Development Co., Inc. Attn: Gary Merlino April 23, 2014 Page 4 I c i c l e C r e e k E n g i n e e r s 0864002/042314 Slopes – 08/13/12)), Coal Mine Hazards (08/07/12), Landslide Hazards (08/12/12) and Erosion Hazards (08/13/12). No Seismic Hazards (RMC 4-3-050J.1.d) or Volcanic Hazards (RMC 4-11-220; USGS, 1998, Volcano Hazards from Mount Rainier, Washington, Open-File Report 98-428)are present within the Merlino Property based on the cited references. According to RMC 4-3-050J.2, special geotechnical studies by qualified professionals are required to be prepared when Geologic Hazards are present on a site. 5.2 STEEP SLOPES 5.2.1 Protected Slopes RMC 4-11-190 defines “Protected Slopes” as follows: “A hillside, or portion thereof, with an average slope, as identified in the City of Renton Steep Slope Atlas or in a method approved by the City, of forty percent (40%) or greater grade and having a minimum vertical rise of fifteen feet (15 feet).” Protected Slopes within the Merlino Property are currently present as shown on Figure 2. According to RMC 4-3-050J.5.a, generally “Development is prohibited on protected slopes.” However, an exception to the prohibition may be granted by the City of Renton under various subsections of RMC 4- 3-050J.5, including RMC 4-3-050J.5.d, which is a subsection that states: d. Exceptions through Waiver: Exceptions to the prohibition may be granted for installation of public utilities which are needed to protect slope stability, and public road widening where all the following provisions have been demonstrated: i. The utility or road improvement is consistent with the Renton Comprehensive Plan, adopted utility plans, and the Transportation Improvement Program where applicable. ii. Alternative locations have been determined to be economically or functionally infeasible. iii. A geotechnical evaluation indicates that the proposal will not increase the risk of occurrence of a geologic hazard, and measures are identified to eliminate or reduce risks. iv. The plan for the improvement is based on consideration of the best available science as described in WAC 365-195-905; or where there is an absence of valid scientific information, the steps in RMC 4-9-250F are followed. SubsectIon L (Top and Toe Setbacks) of RMC 4-4-060 (Grading, Excavation and Mining Regulations) addresses setbacks from the top and toe of cut and fill slopes. Subsection L states: 1. Setbacks – Minimum: The tops and toes of cut and fill slopes shall be set back from setback lines as far as necessary to preserve the setback for the safety and benefit of adjacent properties, the adequacy of foundations, and to prevent damage as a result of water runoff or erosion of the slopes. Setbacks shall be no less than the following: a. Tops of Slopes: Distance to the setback line for the top of slopes shall be a minimum of ten feet (10'). Merlino Land Development Co., Inc. Attn: Gary Merlino April 23, 2014 Page 5 I c i c l e C r e e k E n g i n e e r s 0864002/042314 b. Structures: Distance to structures, if any structures on the site shall be as follows: Slope Height Top Toe Less than 11’ 5’ 3’ 11 – 30.9’ 7’ Height/2’ 31’ and over 10’ 15’ (Ord. 5526, 2-1-2010) 5.2.1 Sensitive Slopes RMC 4-11-190 defines “Sensitive Slopes” as follows: “A hillside, or portion thereof, characterized by: (1) an average slope, as identified in the City of Renton Steep Slope Atlas or in a method approved by the City, of twenty five percent (25%) to less than forty percent (40%); or (2) an average slope, as identified in the City of Renton Steep Slope Atlas or in a method approved by the City, of forty percent (40%) or greater with a vertical rise of less than fifteen feet (15'), abutting an average slope, as identified in the City of Renton Steep Slope Atlas or in a method approved by the City, of twenty five percent (25%) to forty percent (40%). This definition excludes engineered retaining walls. Sensitive Slopes occurred over much of the Merlino Property prior to placement of the Engineered Fill. However, because of the Engineered Fill, no Sensitive Slopes currently exist within the Merlino Property. 5.3 COAL MINE HAZARDS High and Low Coal Mine Hazards exist within the Merlino Property according to Critical Areas mapping by the City of Renton (Map Gallery – Sensitive Areas) and previous studies of the Merlino Property and adjacent areas by ICE. Coal Mine Hazards are addressed in a separate ICE report dated April 23, 2014. 5.4 LANDSLIDE HAZARDS Prior to placement of the Engineered Fill, the Merlino Property was within a Moderate Landslide Hazard area according to regional Critical Areas mapping by the City of Renton (Map Gallery – Sensitive Areas). Because of the Engineered Fill, the designation of a Moderate Landslide Hazard area should be removed for the Merlino Property. 5.5 EROSION HAZARDS Prior to placement of the Engineered Fill, the Merlino Property was within an Erosion Hazard area according to regional Critical Areas mapping by the City of Renton (Map Gallery – Sensitive Areas). During a recent phone discussion with Steve Lee, Development Engineering Manager of the City of Renton’s Community & Economic Development Department’s Planning Division, Mr. Lee advised that the Erosion Hazard area designation on the Merlino Property now applies to the slope created by the Engineered Fill. This is reflected on Figure 2. 5.6 SEISMIC AND VOLCANIC HAZARDS No Seismic or Volcanic hazards have been regionally mapped by the City of Renton (Map Gallery – Sensitive Areas) or field identified by ICE within the Merlino Property. 6.0 GEOLOGIC SETTING The surficial geology at the site prior to the placement of the Engineered Fill was mapped by the US Geological Survey (USGS - D. R. Mullineaux, 1965, “Geologic Map of the Renton Quadrangle, King Merlino Land Development Co., Inc. Attn: Gary Merlino April 23, 2014 Page 6 I c i c l e C r e e k E n g i n e e r s 0864002/042314 County, Washington,” Geologic Quadrangle Map GQ-405) as “undifferentiated glacial sediments” underlain by “Renton Formation” bedrock. Undifferentiated glacial sediments are described by the USGS as consisting of layers of glacial till (ice-deposited silty sand with gravel), glacial outwash (stream- deposited sand and gravel), glaciolacustrine deposits (lake-deposited clay and sand), and nonglacial sand and clay. Renton Formation bedrock is described by the USGS as interbedded (layered) sedimentary rock consisting of sandstone, siltstone, shale, claystone, carbonaceous shale and coal beds. Structurally, the bedrock has been uplifted, folded and faulted over time. This structural deformation of the bedrock has caused the “bedding” of the rock to be tilted about 10 to 14 degrees down to the east in the Merlino Property area. 7.0 SITE CONDITIONS 7.1 SURFACE CONDITIONS Surface reconnaissance of the Merlino Property was completed by Brian Beaman of ICE on April 27, 2009 and again on February 2, 2014. The Merlino Property is located on a west-facing hillside overlooking the City of Renton and is bordered by Cedar Avenue South to the east, the Cedar Crest Condominiums to the north, I-405 to the west, and undeveloped WSDOT-owned forest land and a Puget Sound Energy (PSE) transmission line easement to the south. Before placement of the Engineered Fill, the portion of the subject property immediately west of Cedar Avenue South was characterized by a steep (60 percent grade) road embankment long-ago-created for Cedar Avenue South, an embankment that was about 5- to 15-feet high and that transitioned to a natural slope inclined downward to the west at about a 20 to 30 percent grade. The natural slope flattened gradually to the west. Mine Rock Fill (Coal Spoils) consisting of broken rock and coal fines were observed during our 2005 field reconnaissance and in Test Pits TP-8, TP-14 and TP-16 that were completed for our 2005 study for GWC. Presently, the Engineered Fill has created a nearly-level plateau area that ranges from about 112 feet to 122 feet east-west abutting the west edge of Cedar Avenue South. This plateau area is where the seven residential lots are planned. From the west edge of the plateau, a slope that ICE field-measured as being about 30 degrees (about 1.75H:1V – horizontal to vertical) extends down to the west toward the I-405 right-of-way. The plateau area is vegetated with grass. The bordering slope to the north, west and south of the plateau area (the Engineered Fill slope) is generally vegetated with Douglas-fir trees that are about 8-feet high and shrubs. No surface water was observed within the Merlino Property at the time of our 2009 and 2014 site reconnaissance efforts; these efforts included observation of the ground surface before and after the placement of the Engineered Fill. No surface evidence of landsliding was observed within the Merlino Property at the time of our 2009 and 2014 site reconnaissance efforts. 7.2 ABANDONED UNDERGROUND COAL MINES As previously described, abandoned underground coal mines and related coal mine hazards at the Merlino Property are described in a separate Coal Mine Hazard Assessment report by ICE dated April 23, 2014. This report does not duplicate the description of the abandoned coal mines and coal mine hazards set forth in the separate Coal Mine Hazard Assessment report or the results of subsurface explorations (test pits and test borings) that were set forth in reports completed in 2005 and 2009. Merlino Land Development Co., Inc. Attn: Gary Merlino April 23, 2014 Page 7 I c i c l e C r e e k E n g i n e e r s 0864002/042314 However, site data from those reports was used to supplement our understanding of the site subsurface conditions and was used, in part, as a basis for some of the conclusions in this report. 8.0 CONCLUSIONS AND RECOMMENDATIONS 8.1 GENERAL As previously noted, page 6 of the CDB 2009 Technical Memorandum indicated that the Engineered Fill was designed such that residences could be constructed on this fill. CH2M Hill evaluated the stability of the Engineered Fill for sliding, global stability, compound failure, internal stability, and seismic stability. The final design of the Engineered Fill slope required a minimum factor of safety (FOS) of at least 1.5 for all the factors evaluated. 8.2 STEEP SLOPES 8.2.1 Protected Slopes 8.2.1.1 Engineered Fill Slope Most of the Engineered Fill slope that borders the plateau area of the Merlino Property is a Protected Slope according our site observations and the City’s Protected Slope definition in RMC 4-11-190. In view of both (1) above-quoted subsectIon L (Top and Toe Setbacks) of RMC 4-4-060 (Grading, Excavation and Mining Regulations) and (2) our overall assessment of the Engineered Fill, we recommend (a) a building setback of 25 feet from the Engineered Protected Slope area along the west side of all seven of the proposed lots, (b) a building setback of 10 feet from the portion of the Engineered Fill slope area to the north of Lot 1, and (c) a building setback of 10 feet from the portion of the Engineered Fill slope area to the south of Lot 7, as shown on Figure 2. Our above-stated setback distance recommendations are contingent on vegetation in the Protected Slope areas (other than in the general area of the above-noted proposed sliver fill and/or retaining wall to the south and southwest of the southwest edge of the cul-de-sac) not being cut down or otherwise removed. ICE should be contacted to review tree removal plans if selected trees are to be cut down or otherwise removed from the Protected Slope area (other than in the specific area described above for the proposed sliver fill and retaining wall). We recommend that the west edge of the plateau at the crest of the Engineered Slope be slightly bermed/graded to prevent surface water runoff onto the slope from the plateau. Roof downspout drains and footing drains should discharge to a tightline system that discharges away from the Engineered Slope. 8.2.1.2 Protected Slope – Cedar Avenue South In our opinion, the portion(s) of the sliver fill and/or retaining wall proposed to be installed within the Protected Slope area to the south and southwest of the proposed cul-de-sac at the south end of Cedar Avenue South should be approved by the City pursuant to an “exception through waiver” under RMC 4- 3-050J.5.d, provided the following design and construction practices are followed in regard to the sliver fill and retaining wall: The surface of the applicable portion of the Engineered Fill should be stripped of topsoil and sod, with care taken to not damage the reinforcement fabric in the Engineered Fill. An Ecology block or similar (gravity-type) retaining wall should be used along the south side of the sliver fill where the wall height exceeds 2.5 feet, otherwise a rockery or modular block wall may be Merlino Land Development Co., Inc. Attn: Gary Merlino April 23, 2014 Page 8 I c i c l e C r e e k E n g i n e e r s 0864002/042314 used. Ecology blocks and Ultra Blocks are typically about 2.5- to 3-feet high and 5- or 6-feet long. ICE can provide design criteria for a gravity-type retaining wall system, if requested. The proposed retaining wall system, once the final design is known, should be evaluated by ICE for overall stability. Proper surface and subsurface drainage should be installed to reduce the potential for accumulation of ground water and to reduce the risk of erosion. New fill should be compacted as Structural Fill. Structural Fill should be compacted to at least 95 percent of the maximum dry density obtained using ASTM Test Method D 1557. Construction of the retaining wall and fills should be completed during an extended period of dry weather. ICE should be retained to review the construction plan for the cul-de-sac at the south end of Cedar Avenue South once the design details are available. ICE should be retained to observe and document the construction of the retaining wall and placement of Structural Fill for the retaining wall at the south end of Cedar Avenue South. 8.2.2 Sensitive Slopes As previously described, all Sensitive Slope areas within the Merlino Property have been eliminated by the Engineered Fill. No recommendations for mitigation are needed. 8.3 COAL MINE HAZARDS High and Low Coal Mine Hazards exist within portions of the Merlino Property. Coal Mine Hazards are addressed in a separate ICE report dated April 23, 2014. 8.4 LANDSLIDE HAZARDS The designation of a Moderate Landslide Hazard area should be removed because the Engineered Fill has mitigated this hazard designation. No recommendations for mitigation are needed. 8.5 EROSION HAZARDS As described above, the Erosion Hazard area designation applies to the slope created by the Engineered Fill as shown on Figure 2. Except as noted in the next paragraph, the Engineered Slope will not be disturbed by the development process. For this reason, no special erosion control measures are required other than assuring that the no stormwater runoff is allowed to flow to the slope area (other than the planned discharge from the proposed stormwater detention vault into the existing rock-lined ditch that runs parallel to and along the north edge of the existing gravel access road. We recommend that Core Design evaluate planned flow from the stormwater vault and the ability of the existing rock- lined ditch to accommodate this flow. Construction of the cul-de-sac bulb area will require disturbance of (1) the portion of the Erosion Hazard area underlying part of the southwesterly quadrant of the proposed cul-de-sac bulb and (2) the abutting sliver fill area. Proper temporary erosion and sediment control measures in accordance with local regulations should be provided within the project plans for these areas. 8.6 SEISMIC AND VOLCANIC HAZARDS No Seismic or Volcanic Hazards have been regionally mapped by the City of Renton or field identified by ICE within the Merlino Property. Thus, no recommendations for mitigation are needed. Merlino Land Development Co., Inc. Attn: Gary Merlino April 23, 2014 Page 9 I c i c l e C r e e k E n g i n e e r s 0864002/042314 9.0 RISK EVALUATION 9.1 COMMENTS RELATING TO SUBSECTIONS (iii) AND (iv) OF RMC 4-3-050J.5.d The above-stated design and construction practices are recommended to reduce risks. If these design and construction practices are implemented, in our opinion the proposal to modify the Engineered Slope in the area near the cul-de-sac with a sliver fill and retaining wall should not increase the risk of slope failure to an unacceptable level (FOS less than 1.5). In addition, the planned sliver fill and retaining wall improvement within the Protected Slope in the cul-de-sac bulb area is being designed using locally accepted current standards of engineering practice (“best available science” as described in WAC 365-195-905). 9.2 COMMENTS RELATING TO RMC 4-3-050J.2 Consistent with RMC 4-3-050J.2, (1) the project should not increase the risk of Geologic Hazards to adjacent or abutting properties beyond pre-development conditions, (2) the project should not adversely impact other Geologic Hazards, and (3) the development can be safely accommodated on the site with careful planning by the design team. 10.0 USE OF THIS REPORT We have prepared this report for use by Merlino Land Development Co., Inc. The data and report should be used for land use planning, but our report, conclusions, and interpretations should not be construed as a warranty of subsurface conditions. There are probable variations in subsurface conditions between the explorations completed for other studies; variation in subsurface conditions also may occur over time. A contingency for unanticipated conditions should be included in the short plat infrastructure’s construction budget and schedule. During construction, sufficient observation, testing and consultation by our firm should be provided to (1) evaluate whether the conditions encountered are consistent with those indicated by the explorations, (2) provide recommendations for design changes if the conditions encountered during construction differ from those anticipated, and (3) evaluate whether earthwork activities comply with contract plans and specifications. Within the limitations of scope, schedule and budget, our services have been executed in accordance with generally accepted practices in this area at the time the report was prepared. No warranty or other conditions, express or implied, should be understood. ******************* Merlino Land Development Co., Inc. Attn: Gary Merlino April 23, 2014 Page 10 I c i c l e C r e e k E n g i n e e r s 0864002/042314 We trust this information meets your present needs. If you have any questions or if we can be of further assistance to you, please call. Yours very truly, Icicle Creek Engineers, Inc. Brian R. Beaman, PE, LEG, LHG Principal Engineer/Geologist/Hydrogeologist Kathy S. Killman, LEG Principal Engineering Geologist Document ID: 0864002.REP Attachments: Vicinity Map – Figure 1 Site Plan – Figure 2 Attachment A – I-405 CDB Technical Memorandum, August 14, 2009 Attachment B – Mayes Testing Engineers, Inc. Construction Summary Letter, April 23, 2014 Submitted via surface mail (three original copies) cc: David Halinen, Halinen Law (email as pdf, surface mail – one original copy) I c i c l e C r e e k E n g i n e e r s 0864002/042314 FIGURES 0 ICE FILE NUMBERIcicle Creek Engineers, Inc. 29335 NE 20th Street Carnation, Washington 98014 (425) 333-0093 FigureCHECKED: KSK DRAWN: BRB DESIGNED: --- SCALE: As Shown DATE: April 23, 2014 MERLINO SHORT PLAT - PROPOSED 7-LOT RESIDENTIAL DEVELOPMENT RENTON, WASHINGTON VICINITY MAP 1 0864-002 2,0000 4,000BensonRoadBensonRoadMerlino Property Approximate Scale in Feet ICE FILE NUMBERIcicle Creek Engineers, Inc. 29335 NE 20th Street Carnation, Washington 98014 (425) 333-0093 Figure 0864-002 CHECKED: KSK DRAWN: BRB DESIGNED: --- SCALE: 1 inch - 100 feet DATE: April 23, 2014 MERLINO SHORT PLAT - PROPOSED 7-LOT RESIDENTIAL DEVELOPMENT RENTON, WASHINGTON 2 SITE PLAN EXPLANATION Protected Slope Area (RMC 4-11-190) Building Setback (RMC 4-4-060L)South 7th StreetBase map reference: Core Design, March 19, 2014, Merlino Short Plat, Renton, Washington, Preliminary Site Plan. 25 feet10 feet10 feetCedar Avenue SouthCedar Avenue South Approximate Scale in Feet 0 100 200 Retaining Wall Sliver Fill WSDOT Property Merlino Property Proposed Right-of-Way Line Existing Right-of-Way Line Erosion Hazard Area (RMC 4-3-050Q.3.b) I c i c l e C r e e k E n g i n e e r s 0864002/042314 ATTACHMENT A I-405 CORRIDOR DESIGN BUILDERS TECHNICAL MEMORANDUM DATED AUGUST 14, 2009 I-405 RENTON STAGE 2 DESIGN/BUILD PROJECT WSDOT EXCHANGE PROPERTY REINFORCED SOIL SLOPE GEOTECHNICAL DESIGN RECOMMENDATIONS MEMORANDUM REV 0 RTN/RS2_EXCHANGEPOPERTY_RSS_DESIGNRECOMMENDATIONS_REV0_081409.DOC 2 COPYRIGHT 2009 BY I-405 CORRIDOR DESIGN BUILDERS • COMPANY CONFIDENTIAL Subsurface Conditions Geotechnical conditions for the WSDOT Exchange Property area were established on the basis of existing geotechnical explorations supplemented by 3 new explorations advanced by Icicle Creek Engineers in support of the Renton Stage 2 Project. The new boring logs were used with the existing site soil information to develop geotechnical parameters for analysis and design of RSS slope. Geotechnical Explorations The following exploration locations were used in the evaluation of the site conditions and in the creation of soil profiles beneath the RSS. The boring and test pit logs were also used to develop geotechnical parameters for analysis and design of the RSS. The source of the exploration information is summarized in Table 1. Figure 2 shows the approximate locations of the explorations. Figure 3 shows the interpreted typical subsurface. Copies of the exploration logs are included in Attachment B. TABLE 1: WSDOT EXCHANGE PROPERTY EXPLORATION LOCATIONS Exploration Location Type Source B-1 Boring Icicle Creek Engineers, Inc., 2005 B-2 Boring Icicle Creek Engineers, Inc., 2005 B-3 Boring Icicle Creek Engineers, Inc., 2005 TP-1 Test pit Icicle Creek Engineers, Inc., 2005 TP-2 Test pit Icicle Creek Engineers, Inc., 2005 TP-3 Test pit Icicle Creek Engineers, Inc., 2005 TP-4 Test pit Icicle Creek Engineers, Inc., 2005 TP-5 Test pit Icicle Creek Engineers, Inc., 2005 TP-6 Test pit Icicle Creek Engineers, Inc., 2005 TP-7 Test pit Icicle Creek Engineers, Inc., 2005 TP-8 Test pit Icicle Creek Engineers, Inc., 2005 TP-12 Test pit Icicle Creek Engineers, Inc., 2005 TP-13 Test pit Icicle Creek Engineers, Inc., 2005 TP-14 Test pit Icicle Creek Engineers, Inc., 2005 TP-15 Test pit Icicle Creek Engineers, Inc., 2005 TP-16 Test pit Icicle Creek Engineers, Inc., 2005 515-4-06 Boring Geoengineers, 2007 CDB-6p-08 Boring Geoengineers, 2007 SRX-20-05 Boring Geoengineers, 2007 REV 0 RTN/RS2_EXCHANGEPOPERTY_RSS_DESIGNRECOMMENDATIONS_REV0_081409.DOC 3 COPYRIGHT 2009 BY I-405 CORRIDOR DESIGN BUILDERS • COMPANY CONFIDENTIAL TABLE 1: WSDOT EXCHANGE PROPERTY EXPLORATION LOCATIONS Exploration Location Type Source 515-6-06 Boring Geoengineers, 2007 515-7-06 Boring Geoengineers, 2007 B-5 Boring Icicle Creek Engineers, Inc., 2009 B-10 Boring Icicle Creek Engineers, Inc., 2009 B-11 Boring Icicle Creek Engineers, Inc., 2009 Icicle Creek Engineers, Inc., “Report- Coal Mine Hazard Assessment and Preliminary Geotechnical Evaluation, Renton Hill Property, King County Parcel Nos. 2023059085 and 0007200194/196, Renton, Washington,” June 10, 2005. GeoEngineers, 2007, “Geotechnical Baseline Report I-405/1-5 to SR 169 Stage 2 – Widening and SR 515 Interchange, Renton, Washington,” September 7, 2007. Icicle Creek Engineers, Inc., “Report, Geological Engineering Services, Coal Mine Hazard Assessment, WSDOT Property, Renton, Washington,” May 11, 2009. Interpreted Geotechnical Conditions and Groundwater Location The existing WSDOT Exchange property is an undeveloped parcel of land located on the hillside between I-405 and Cedar Avenue. Slopes vary from 5 to over 90 percent, with slope lengths varying from 25 to over 100 feet. The site elevation varies from approximately 140 feet to 230 feet. The general subsurface profile consists of colluvium/fill overlying residual soils weathered from the Renton Formation overlying the Renton Formation. The colluvium/fill/residual soils are difficult to distinguish from each other and are considered as one unit for the analysis. The site is underlain by the Renton Formation sandstone bedrock. In the southwest portion of the site there are deposits of materials consisting of mine tailings and old municipal waste that are associated with the abandoned Renton Civic Dump site. The general characteristics of the predominant geologic units are as follows: • The colluvium/fill/residual soils vary from ~1 foot to 10 feet thick over the site. These soils are generally medium dense and consist primarily of silty sand. • The tailings/municipal waste thickness varies from a thin veneer to over 25 feet thick. These soils are loose to medium dense and contain a wide variety of materials including silt, sand, slag, ashes, glass, metal, debris, and other materials associated with municipal waste disposal. Mine tailings may also be incorporated in this material, either as cover soils, or as a result of previous mining activities that occurred in the same area. • The Renton Formation consists of weak sandstone bedrock with occasional siltstone layers and extends below the depth explored with borings at the site. Boring log information indicates that groundwater was found generally in the Renton Formation, below elevation 100 feet. REV 0 RTN/RS2_EXCHANGEPOPERTY_RSS_DESIGNRECOMMENDATIONS_REV0_081409.DOC 4 COPYRIGHT 2009 BY I-405 CORRIDOR DESIGN BUILDERS • COMPANY CONFIDENTIAL Seismicity and Ground Motions The Renton Stage 2 Project is being designed in accordance with WSDOT’s current seismic design requirements. These requirements include use of a design earthquake that has a 7 percent probability of exceedance in a 75-year exposure period. The seismic ground motions and liquefaction potential for this design earthquake are summarized below. Seismic Ground Motions Design peak ground acceleration (PGA) of 0.44g is used in analysis. This ground motion was determined using the AASHTO ground motions hazard map and a site coefficient for peak ground acceleration (Fpga) of 1.0 based on Site Class C site classification. Per the WSDOT GDM (2008), a horizontal pseudo-static acceleration coefficient, kh = 0.22 (F*PBA/2) was used in the global stability analysis. Use of this reduced seismic coefficient implies that several inches of permanent slope displacement is acceptable during the design seismic event. Liquefaction Potential Soils at the project site below the water table are the sandstone bedrock; therefore, liquefaction potential of site soils is very low. Surface water will be routed from the RSS and fill to prevent infiltration and possible ponding of water within the compacted fill layers and RSS. Geotechnical Design The design of RSS follows the steps outlined in Chapter 7 of FHWA Publication FHWA- NHI-00-043, “Mechanically Stabilized Earth Walls and Reinforced Soil Slopes Design and Construction Guidelines,” by Elias, et al. (2001). General Design Considerations The general design considerations for this project are listed below. • Traffic Surcharge assumed equivalent to 2.0 feet of soil surcharge (surcharge unit weight = 125 pcf) = 125 pcf x 2 feet = 250 psf. • Extensible (geosynthetic geogrid) reinforcement is to be used. • A wrapped face is not required because the slope is shallower than 1.2(H):1(V) (GDM, 2008). • Minimum length of reinforcing is 6 feet (GDM, 2008). • Primary reinforcing shall be vertically spaced at 3 feet or less (GDM, 2008). • Minimum long-term allowable strength of primary reinforcing = 1,250 lb/ft. REV 0 RTN/RS2_EXCHANGEPOPERTY_RSS_DESIGNRECOMMENDATIONS_REV0_081409.DOC 5 COPYRIGHT 2009 BY I-405 CORRIDOR DESIGN BUILDERS • COMPANY CONFIDENTIAL • Secondary reinforcing between layers of primary reinforcing shall be at a maximum vertical spacing of 1 foot (GDM, 2008). Secondary reinforcing shall not be included in the internal stability analysis of the RSS. • Minimum long-term allowable strength of secondary reinforcing = 115 lb/in. • Backfill within the reinforced zone of the RSS shall consist of Common Borrow, meeting the requirements of WSDOT Standard Specifications Section 9-03.14(3), as modified in the Project Technical Specification drafted for the RSS. As follows: Sieve Size Percent Passing 3-inch 100 No. 4 100 - 20 No. 200 0 - 35 Geotechnical Material Properties The following properties were used in the design of the RSS: New Fill: • Unit weight = 130 pcf • Internal angle of friction = 36 degrees • Cohesion (static case) = 0 psf • Internal angle of friction (seismic case) = 34 degrees • Apparent cohesion (seismic case) = 200 psf Residual soil/colluvium/fill: • Unit weight = 130 pcf • Internal angle of friction = 36 degrees • Cohesion (static case) = 0 psf • Apparent cohesion (seismic case) = 200 psf Renton Formation: • Uniaxial compressive strength = 300 psi (43.2 ksf) • Geologic strength index (GSI) = 40 • Intact rock constant (mi) for sandstone = 17 • Disturbance factor (D) for good quality excavation = 0.0 • Mohr-Coulomb fit (Hoek-Brown Criteria), internal angle of friction = 32 degrees • Mohr-Coulomb fit (Hoek-Brown Criteria), cohesion (seismic and static cases) = 2100 psf Municipal Waste: • Unit weight = 115 pcf • Internal angle of friction = 28 degrees • Cohesion (static case) = 300 psf • Apparent cohesion (seismic case) = 300 psf REV 0 RTN/RS2_EXCHANGEPOPERTY_RSS_DESIGNRECOMMENDATIONS_REV0_081409.DOC 6 COPYRIGHT 2009 BY I-405 CORRIDOR DESIGN BUILDERS • COMPANY CONFIDENTIAL Reinforcement Length Requirements Analyses were conducted at selected sections along the RSS to evaluate the minimum reinforcement lengths (Lmin) required to satisfy stability requirements. The analytical results were compared to GDM minimum acceptable criteria shown below. • Sliding FS 1.5 • Global Stability (outside of reinforced zone) FS 1.5 • Compound Failure (through face of RSS) FS 1.5 • Internal Slope Stability (through the reinforcing) FS 1.5 • Lateral Squeeze (bearing failure) FS 1.5 • Seismic Stability FS 1.1 The above factors of safety assume that structures (e.g., residences) will be constructed on the RSS fill in the future. For sliding, global stability, compound failure, internal stability, and seismic stability evaluations, the computer program SLIDE (Rocscience, 2008) was used. Lateral squeeze does not apply because the RSS is founded on competent bearing materials. To achieve the required FS, a geogrid with minimum long-term design strength of 1,250 lb/ft, coupled with the reinforcement lengths summarized in Table 2, is required. The length of reinforcing was generally controlled by a combination of static and seismic stability. The approximate station extents for the different Lmin are summarized in Table 2. All stations are based on a construction reference alignment CEDAR RW Line. For a given embankment location, all reinforcing lengths are constant for the entire embankment height. TABLE 2: REINFORCEMENT TABLE Beginning Station Ending Station Minimum Reinforcement Length (Lmin) Bottom Reinforcing Elevation (ft) Top Reinforcing Elevation (ft) 10+35 10+75 25 200 Varies, max 220 10+75 11+50 40 194 220 11+50 11+75 40 182 220 11+75 12+50 50 172 222 12+50 13+00 45 172 222 13+00 13+75 40 176 222 13+75 14+50 40 172 224 14+50 15+45 40 172 226 15+45 15+95 40 172 Varies, max 226 REV 0 RTN/RS2_EXCHANGEPOPERTY_RSS_DESIGNRECOMMENDATIONS_REV0_081409.DOC 7 COPYRIGHT 2009 BY I-405 CORRIDOR DESIGN BUILDERS • COMPANY CONFIDENTIAL Settlement Due to the granular consistency and/or heavily overconsolidated nature of the existing soils and bedrock, settlement is anticipated to be elastic in nature and is expected to occur during embankment construction. Construction Requirements The construction of the RSS and backfill require careful planning and construction control, including oversight by the project geotechnical engineer, to assure that the slope is constructed in such a manner that short- and long-term stability requirements are met. The following subsection summarizes key construction requirements. Specific requirements for construction of the RSS are included in the technical specification Reinforced Soil Slope, I.5:1 (Horizontal to Vertical) Slopes, included as Attachment C to this memorandum. Subgrade Preparation and Ground Improvement Before placement of fill or backfill for the RSS, all surface vegetation, topsoil, trash, construction debris, or other deleterious materials shall be removed from beneath the reinforced soil zone and properly disposed of offsite. Loose, soft, or wet material should also be removed and replaced with competent backfill. All sharp stone protrusions that could damage the reinforcing should also be removed. The subgrade within the footprint of the reinforced soil volume should be graded level as required for construction, proof rolled, and compacted to 95% of Standard Proctor Density (ASTM D698, AASHTO T99). Fill shall be keyed into the existing slope following Section 2- 03.3(14) “Hillside Terraces” of the Standard Specifications. Because of the variable nature of the site fill, field review and approval of the RSS subgrade and construction site preparation below the RSS by the project geotechnical engineer is required. Overexcavation may be required in areas where actual subgrade conditions do not meet the design recommendations. Depth and extent of overexcavation will be as directed by the geotechnical engineer. Fill and Backfill Requirements Backfill within the reinforced zone of the RSS shall consist of Common Borrow, meeting the requirements the RSS Project Technical Specification. The borrow source is expected to be the Renton Formation that is excavated to construct other project elements. The backfill material must be free of organics and other deleterious materials. The maximum particle size should be 3 inches. If wet-weather construction makes it difficult to achieve the required moisture and compaction density, Select Borrow (Section 9-03.14(2)) or Gravel Borrow (Section 9-03.14(1)) shall be used in lieu of Common Borrow. Backfill in the reinforced zone shall be placed in loose lifts of maximum 12-inch thickness and compacted to 95% of maximum density in accordance with the requirements of Section 2-03.3(14)C, Method C, of the WSDOT Standard Specifications and the project-specific technical specification (see Attachment C). REV 0 RTN/RS2_EXCHANGEPOPERTY_RSS_DESIGNRECOMMENDATIONS_REV0_081409.DOC 8 COPYRIGHT 2009 BY I-405 CORRIDOR DESIGN BUILDERS • COMPANY CONFIDENTIAL Backfill behind the reinforced zone shall be Common Borrow in accordance with the requirements of Section 9-03.14(3) of the Standard Specifications, provided that the material can be compacted in accordance with the requirements of Sections 2-03.3(14)C and 2- 03.3(14)D of the Standard Specifications. If wet-weather construction makes it difficult to achieve the required moisture and compaction density, Select Borrow (Section 9-03.14(2)) or Gravel Borrow (Section 9-03.14(1)) may be used in lieu of Common Borrow. Temporary Excavation Limited excavation may be required in order to construct the reinforced soil slope. Temporary excavations sloped to 1:1 should perform adequately during construction. If the Renton Formation bedrock is encountered in temporary excavations needed to place reinforcing grids, the lengths of the geogrid may be reduced, provided the project geotechnical engineer is notified in advance to verify subsurface conditions. In no case shall the reduced length of reinforcing be keyed into the Renton Formation less than 5 feet. Existing Utilities No known utilities cross beneath the proposed the RSS footprint. If any are encountered during construction, they should be brought to the attention of the project geotechnical engineer. In no case should the arrangement of slope reinforcing by modified to accommodate utilities without the approval of the project geotechnical engineer. Drainage and Erosion Control Temporary construction slopes shall direct water away from the RSS slope face to prevent erosion. The face of the RSS shall be stabilized following project temporary erosion and sediment control procedures and shall be planted with permanent vegetation in accordance with the project landscaping plans. References AASHTO (2002). Standard Specifications for Highway Bridges, 17th Edition (2002) – Allowable Stress Design. American Association of State Highway and Transportation Officials, 2002. AASHTO (2007). AASHTO LRFD Bridge Design Specifications, Fourth Edition. American Association of State Highway and Transportation Officials, 2007. FHWA (2001). Mechanically Stabilized Earth Walls and Reinforced Soil Slopes Design and Construction Guidelines. U.S. Department of Transportation, Federal Highway Administration. FHWA-NHI-00-043. March 2001. RocScience (2008). SLIDE Version 5.0 - User’s Manual. WSDOT (2008). Geotechnical Design Manual. Washington State Department of Transportation. WSDOT (2008). Standard Specifications for Road, Bridge, and Municipal Construction. Washington State Department of Transportation. M41-10. 90100100 100 100100100 110110 110 110 110 11 0120120 120120120 120 130 130 13 0 130 130 130 130140140140 140140140 150150 150 150 150 1 5 0 160160160 160 160 160 170 170 170 170 170 170 170180180 180 180 180180 190190 190 190 190 190200 200 200 200 200 200210 210 210 210 210210220 220 220 220 220 220230230230 230 230 230 240240240240 ROW CLF CLF 200 NO. Washington State Department of Transportation ISSUE DATE ISSUE RECORD - DESCRIPTION DESIGNED BY ENTERED BY CHECKED BY WASH10 NO.DESIGN MANAGER: DESIGN TASK LEAD: PACKAGE: REGION STATE CONTRACT NO. P.E. STAMP BOX DATEB07/29/09 K. LORENTSONFINAL DESIGN - 1B M. ROHILAC. HERMOGENES 08/14/09 K. LORENTSON M. ROHILAC. HERMOGENES0RELEASE FOR CONSTRUCTION - 1B WSDOT EXCHANGE PROPI-405 AND SR 515 INTERCHANGE STAGE 2 - WIDENING I-5 TO SR 169 SHEET OF SHEETS 7624_04_CG_1_01.dlv2:48:56 PM8/12/20097624 150 160 160 170170 170 180 180 180 190190 190200200 200210 210 220220 230 230230 1110 12 13 14 15 16 9 100101102103EE R.J NO RTHBOUND I-405 SOUTHBOUND I-405 J. BAUMAN K. LORENTSON SCALE IN FEET 0 30 60 A T. 23N. R. 5E. W.M. CG-0-02 CG-0-02 CEDAR RW LINE A S. FORMAN C. HERMOGENES CEDAR AVE S 1230 1230 B 06/19/09 PRELIMINARY DESIGN NB405 LINE SB405 LINE LEGEND 200 1.5:1CUT LINE CG-0-01 NOTES:2:12:11.5:11.5:12:1FILL LINE1.5:12:1 1.5:1 2:1 1.5:12:1 1 .5:1 2:11.5:12:1 1.5:1 CEDAR RW 10+91.62, 113.77’ RT ELEV 228.00 CEDAR RW 11+63.35, 113.00’ RT ELEV 230.00 CEDAR RW 12+86.86, 8.00’ LT ELEV 232.00 CEDAR RW 11+89.62, 8.00’ LT ELEV 230.00’ CEDAR RW 13+74.52, 114.82’ RT ELEV 234.00 CEDAR RW 14+69.96, 115.25’ RT ELEV 236.00 CEDAR RW 14+00.63, 8.00’ LT ELEV 234.00 CEDAR RW 15+39.28, 118.95’ RT ELEV 236.00 CEDAR RW 15+99.89, 0.00’ RT ELEV 238.00 CEDAR RW 14+97.08, 8.00’ LT ELEV 236.00 CONTOUR GRADING WSDOT EXCHANGE PROPERTY2:1CEDAR RW 12+60.26, 113.59’ RT ELEV 232.00 CEDAR RW 10+97.21, 10.78’ LT ELEV 228.00’ N1^26’53.75"E 2:1 A. BASTASCH DITCH, SEE DRAINAGE PLANS VARIES 2:1 MAX STREAM BUFFER THUNDER HILLS CREEK EXISTING MAJOR CONTOUR EXISTING MINOR CONTOUR PROPOSED MAJOR CONTOUR PROPOSED MINOR CONTOUR STREAM/ WETLAND BUFFER SLOPE ARROW LIMITED ACCESS WSDOT ROW AR LI NE 1. 2. 3. 4. ACCESS SEE CG-0-05 1.5:1 629 CEDAR AVE S CONDOMINIUMS FOR DITCH PROFILES, SEE DRAINAGE PLAN AND PROFILES. FOR SLOPE ROUNDING, SEE DLS-0-02. FOR REINFORCED SOIL SLOPE DETAILS, SEE SHEET CG-0-04. FOR EXISTING UTILITIES, SEE UTILITY PLANS. RFC - 1B E405 LINE LIMITS OF FILL WITHIN WSDOT RIGHT-OF-WAY NOT TO EXCEED SIX (6) FEET IN HEIGHT AND NOT TO ENCROACH OVER FILL LINE SHOWN Dense BrushTreesTreesTreesDense BrushBrushBrushBrushSSSSSSSSRandomSIGN Request 140780TR_SN_OverheadSignTR_SN_OverheadSignUTILITY Request 1TP_MM_UnknownObjectTP_MM_UnknownObjectRD_BR_BarrierFaceRD_BR_BarrierFace31379Copy of GEOTECH Request 1Random"EXIT 4""900 WEST""169 SOUTH"100100110110120120120130130130140140140 150150150160160160170170170180180180190190190200200200210210210220220220230230230240240240250250BL_LN_BreaklineGenericBL_LN_BreaklineGeneric1000Book 1BreaklineWSDOT EXCHANGE PROP!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>!>CEDAR AVENB I-405B-5B-3B-2B-1B-11B-10TP-8TP-7TP-6TP-5TP-4TP-3TP-2TP-1TP-16TP-15TP-14TP-13TP-12515-7-06515-6-06515-4-06SRX-20-05CDB-6p-08050 100 150 20025Feet³Figure 2: WSDOT Exchange PropertySubsurface Investigation Locations I c i c l e C r e e k E n g i n e e r s 0864002/042314 ATTACHMENT B MAYES TESTING ENGINEERS, INC. CONSTRUCTION SUMMARY LETTER DATED APRIL 23, 2014 REINFORCED SOIL SLOPE AT WSDOT EXCHANGE PROPERTY