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HomeMy WebLinkAboutTIR-4221 Lindbergh High School Modernization and Additions Technical Information Report Original Date: April 15, 2022 Revised: October 26, 2022 The information contained in this report was prepared by and under the direct supervision of the undersigned: Owner: Renton School District 300 SW 7th St Renton, WA 98057 (425) 204-2300 Contact: Brianne Tomlin Prepared for: Laurie Pfarr, P.E. LPD Engineering, PLLC 1932 1st Ave, Suite 201 Seattle, WA 98101 (206) 725-1211 Bassetti Architects 71 Columbia St, Suite 500 Seattle, WA 98104 (206) 340-9500 Contact: Steve Zang DEVELOPMENT ENGINEERING Michael Sippo 02/02/2023 LINDBERGH HS – MODERNIZATION AND ADDITIONS TECHNICAL INFORMATION REPORT TABLE OF CONTENTS Section 1 – Project Overview .................................................................................................................................. 1 Section 2 – Conditions and Requirements Summary ........................................................................................ 2 Section 3 – Offsite Analysis ...................................................................................................................................... 4 Section 4 – Flow Control and Water Quality Facility Analysis and Design ................................................ 7 Section 5 – Conveyance Systems Analysis and Design ................................................................................... 11 Section 6 – Special Reports and Studies .............................................................................................................. 11 Section 7 – Other Permits ...................................................................................................................................... 12 Section 8 – CSWPPP Analysis and Design ......................................................................................................... 12 Section 9 – Bond Quantities, Facility Summaries, and Declaration of Covenant .................................... 12 Section 10 – Operations and Maintenance Manual .......................................................................................... 12 FIGURES Figure 1: TIR Worksheet Figure 2: Vicinity Map Figure 3: Existing Conditions Figure 4: Proposed Conditions Figure 5: Downstream Drainage Map APPENDICES Appendix A – Design Drawings Appendix B – Design Calculations and Supporting Information Appendix C – Construction Stormwater Pollution Prevention Plan (SWPPP) Narrative Appendix D – Operations and Maintenance Manual Appendix E – Special Reports and Studies Appendix F – Facility Summaries and Declaration of Drainage Covenant LPD Engineering PLLC Page 1 Lindbergh HS – Modernization and Additions Revised Technical Information Report, October 26, 2022 LINDBERGH HS – MODERNIZATION AND ADDITIONS TECHNICAL INFORMATION REPORT ORIGINAL DATE: APRIL 15, 2022 REVISED: OCTOBER 26, 2022 SECTION 1 – PROJECT OVERVIEW This Technical Information Report (TIR) is for the onsite and frontage improvements for proposed building renovations at Lindbergh High School. Refer to Figure 1 – TIR Worksheet for basic site information. The school site consists of three contiguous parcels associated with the primary address of 16426 128th Avenue SE in Renton, Washington. The main high school facility spans the two largest adjacent parcels (parcel numbers: 2823059004 and 2823059042). The existing science wing resides on the easternmost parcel, and the administrative/health center sits on the westernmost parcel. The school property totals 37 acres. The property is bounded by residential properties to the north and east, Renton Park and Renton Park Chapel to the south, and 128th Avenue SE to the west. The site is located in Section 28, Township 23 North, Range 5 East, Willamette Meridian. Refer to Figure 2 – Vicinity Map. The City of Renton has adopted the 2016 King County Surface Water Design Manual (KCSWDM) with the City’s 2017 Surface Water Design Manual amendment (RSWDMA). According to Figure 1.1.2.A of the RSWDMA, Flow Chart for Determining Type of Drainage Review Required, the project is subject to a “Full Drainage Review” because the project results in greater than 2,000 square feet (SF) of new plus replaced impervious surface, and it is not defined as a large project or single-family residential project. Per the “Full Drainage Review” requirements in Table 1.1.2.A, the TIR addresses Core Requirements #1-9 and Special Requirements #1-5 of the 2017 RSWDMA. Existing Conditions The property currently contains the main school building, a pool building, portables, several playfields, and associated parking lots. See Figure 3 – Existing Conditions. Renton GIS mapping shows regulated slopes designated throughout the school site including within the proposed building renovation areas. Topographically, the specific renovation site area is relatively flat, but generally slopes down from the east to the west from a high elevation of approximately 430-feet. Elevations descend to a low point approximately 400-feet at the surface parking area adjacent to the west of the major portions of the school facility. Renton GIS also shows that a small portion of the southeast corner of the property is within a seismic hazard area. The proposed project site is outside of this area. Per the USDA web soil survey, the soil consists of Alderwood gravelly sandy loam (AgC) which may have some infiltrative capabilities. However, based on the existing stormwater infrastructure on-site, there are no implications of infiltrative facilities being utilized for stormwater management. A geotechnical report was prepared for the site by Associated Earth Sciences, Inc (AESI), dated February 7, 2022. AESI also prepared a subsequent limited geotechnical engineering study for the parking lot, LPD Engineering PLLC Page 2 Lindbergh HS – Modernization and Additions Revised Technical Information Report, October 26, 2022 dated January 3, 2022. Borings encountered a layer of fill ranging from 4 to 9 feet below ground surface. Dense to very dense Vashon Lodgement Till was encountered below the fill layer and extended to the maximum depth explored, 35 feet below ground surface. Neither of these soil layers is a suitable infiltration receptor. Perched groundwater seepage was observed is several borings at depths from 1 to 7 feet below ground surface, and directly below the asphalt in one of the parking lot borings. There are two distinct drainage systems onsite which divide the site into two threshold discharge areas (TDA). The North TDA system collects flow from some of the building roof, the northern parking lot and driveway, and the softball and baseball fields. This system leaves the site at the northwest corner of the property and discharges to the public storm main in 128th Avenue SE. The South TDA system collects flow from some of the building roof, the southwest parking lot and driveway, the tennis courts, and the track and field. This system leaves the site at the southeast corner of the property to an adjacent private system before outfalling to Molasses Creek. Proposed Conditions The project proposes approximately of 157,400 SF (3.613 acres) of disturbed area in various locations around the school property. The project involves improvements in both the North and South TDAs and will be designed to maintain existing drainage patterns. Improvements in the North TDA include the proposed building additions and associated walkways, and sidewalk and curb ramps in the frontage along 128th Ave SE. Improvements in the South TDA include the replaced asphalt parking lot and a small portion of concrete walkway on the northeast side of the school building. Refer to Section 4 – Flow Control and Water Quality Analysis and Design for further information on the storm drainage design. SECTION 2 – CONDITIONS AND REQUIREMENTS SUMMARY This section addresses the requirements set forth by the 2017 Renton SWDM, Core and Special Requirements listed in Chapter 1. Core Requirements Core Requirement 1 – Discharge at Natural Location (1.2.1): The proposed conditions will maintain the existing discharge locations to the maximum extent feasible. The site is divided into two threshold discharge areas which will not be altered by the project. Refer to the Offsite Analysis section of this report for a description of the existing discharge points from the site. Core Requirement 2 – Off-site Analysis (1.2.2): A Level 1 Downstream Analysis is included in Section 3 of this report. Core Requirement 3 – Flow Control (1.2.3): Per the City of Renton Flow Control Application Map, Reference 15-A in the RSWDMA, both threshold discharge areas associated with the project are located within a Flow Control Duration Standard area. The target surfaces include new impervious and new pervious surfaces not fully dispersed. Exception 3 in the RSWDMA states that flow control LPD Engineering PLLC Page 3 Lindbergh HS – Modernization and Additions Revised Technical Information Report, October 26, 2022 facility requirements are waived for any threshold discharge area in which the target surfaces cause less than a 0.15 cfs increase in the 100-year peak flow compared to the forested (historical) site conditions. Both the North and South TDAs meet this condition so flow control facilities are not required. Refer to Section 4 of this report for a more detailed description of the flow control requirements. Core Requirement 4 – Conveyance System (1.2.4): Refer to Section 5 of this report for conveyance analysis. Core Requirement 5 – Erosion and Sedimentation Control (1.2.5): A Temporary Erosion and Sediment Control (TESC) plan has been included with the plan set. The TESC plan will be considered the minimum for anticipated site conditions. The Contractor will be responsible for implementing all TESC measures and upgrading as necessary. The TESC facilities will be in place prior to any demolition, clearing, grubbing or construction. Core Requirement 6 – Maintenance and Operations (1.2.6): The Operations and Maintenance Manual for the project is in Appendix D. Core Requirement 7 – Financial Guarantees and Liability (1.2.7): Financial guarantees and liability are not anticipated to be required since the Owner is a public agency. Core Requirement 8 – Water Quality (1.2.8): Per Exemption 3 in Section 1.2.8 of the RSWDMA, water quality is not required since the following is true for both TDAs: 1. The total valuation of the project is less than 50% of the value of the existing site improvements. 2. The project proposes less than 5,000 square feet of new pollution-generating impervious surface (PGIS) and less than ¾ acre of new pollution-generating pervious surface. Although not required, the owner will be providing water quality treatment for a portion of the replaced parking lot to improve the quality of stormwater runoff leaving the site. For further information regarding the water quality design requirements, refer to Section 4 of this report. Core Requirement 9 – On-Site BMPs (1.2.9): The project site proposed more than 2,000 SF of new plus replaced impervious surfaces which will require an evaluation of BMP feasibility for all target surfaces. Per section 1.2.9.2 of the 2017 RSWDMA, this project will be subject to Large Lot BMP Requirements since the project site is larger than 22,000 SF. Refer to the On-Site BMPs evaluation within Section 4 of this report. Special Requirements Special Requirement 1 – Other Adopted Area-Specific Requirements (1.3.1): The City of Renton Surface Water Design Manual is one of several adopted regulations in the City of Renton that apply requirements for controlling drainage on an area-specific basis. Other adopted area-specific regulations include requirements that have a more direct bearing on the drainage design of a proposed project. These regulations include the following: • Master Drainage Plans (MDPs) – The project is not within an area covered by an approved Master Drainage Plan. Project is not a Master Planned Development, a Planned Unit Development, a subdivision that will have more than 100 lots, a commercial LPD Engineering PLLC Page 4 Lindbergh HS – Modernization and Additions Revised Technical Information Report, October 26, 2022 development that will construct more than 50 acres of impervious surface, and will not clear more than 500 acres within a drainage sub-basin. Therefore, a Master Drainage Plan is not required. • Basin Plans (BPs) – The Watershed Management Committee Lower Cedar River Basin and Nonpoint Pollution Action Plan, adopted 1997, was reviewed to determine if there are regulations applicable to this site. There are no additional water quality requirements listed by the report. • Salmon Conservation Plans (SCPs) – The project is not within an area governed by SCPs. • Lake Management Plans (LMPs) – The project is not within an area governed by an LMP. • Hazard Mitigation Plan – The proposed project is not within an area with a Hazard Mitigation Plan. • Shared Facility Drainage Plans (SFDPs) – The proposed project is not within an area with an SFDP. Special Requirement 2 – Flood Hazard Area Delineation (1.3.2): According to King County iMap, the project does not contain nor is it adjacent to a Flood Hazard Area. Special Requirement 3 – Flood Protection Facilities (1.3.3): The project does not have existing flood protection facilities, nor does it propose new flood protection facilities. Special Requirement 4 – Source Control (1.3.4): The owner shall maintain the stormwater drainage system as described in the Operation and Maintenance manual, included in Section 10 of this report. No other source control BMPs, including those listed in Section 1.3.4 of the 2017 RSWDMA are applicable to the scope of proposed improvements. Special Requirement 5 – Oil Control (1.3.5): The project will not have high-use site characteristics nor is it an existing high-use site; therefore, oil control is not required. Special Requirement 6 – Aquifer Protection Area (1.3.6): The project is not located within an aquifer protection area. SECTION 3 – OFFSITE ANALYSIS The following is the Level 1 downstream analysis for the proposed project. Refer to Figures 5 - Downstream Drainage Map. The following resources have been reviewed for the project area: Task 1 – Study Area Definition and Maps The downstream analysis for the project area is based upon the following resources: • Site Survey • On-site Investigation • King County iMap • City of Renton GIS Mapping LPD Engineering PLLC Page 5 Lindbergh HS – Modernization and Additions Revised Technical Information Report, October 26, 2022 • A subsurface exploration and geotechnical feasibility study prepared by Associated Earth Sciences, Inc.; dated February 7, 2022 Task 2 – Resource Review Floodway Map The site is not located within a Floodway or Floodplain per the Washington State Department of Ecology Flood Maps and King County iMap. Sensitive Areas The following is a summary of SAO sensitive areas located within the project area or within the downstream drainage course from the project area. The King County iMap and Renton COR Maps were used to examine the SAOs.  SAO Erosion Hazard – The project site is not located within an erosion hazard area.  SAO Seismic Hazard – The southwestern corner of the school property is located within a seismic hazard area. However, the project site is outside of this area.  SAO Landslide Hazard – There are no landslide hazard areas located within the project site.  SAO Coal Mine – There are no coal mines located within the project site.  SAO Stream – According to King County iMap, there are no unclassified stream or any waterbodies through the developed school site.  SAO Wetland – There are no wetlands located within one mile downstream of the project site.  Groundwater Contamination – According to iMap, the project site has no mapped susceptibility to groundwater contamination.  Sole Source Aquifer – Per King County iMap, the project site is not located within a sole source aquifer area.  Critical Aquifer Recharge Area – The project site is not considered a Critical Aquifer Recharge Area.  Channel Migration Hazard – Per King County iMap, the project site is not located within a channel migration hazard zone. Topographic Map The detailed topographic information for the project area is shown on the design drawings. Drainage Complaints According to the COR Map, there have been no drainage complaints within the last 10 years within the project site, upstream area, or downstream area. Migrating River Studies According to King County’s iMap program, the project site is not located within or adjacent to a channel migration hazard area. LPD Engineering PLLC Page 6 Lindbergh HS – Modernization and Additions Revised Technical Information Report, October 26, 2022 Water Quality Problems Per the 2017 Renton SWDM, King County-identified water quality problems do not apply to the City. Task 3 – Field Inspection A field inspection and Level 1 Downstream analysis was conducted by LPD on November 5th, 2021 to verify the on-site conditions, downstream drainage paths, and upstream basins. The weather during the site investigation was clear and sunny, with a temperature of approximately 48 degrees Fahrenheit. Refer to Drainage System Description and Problem Descriptions below for information about the existing conditions and downstream analysis. Task 4 – Drainage System Description and Problem Descriptions As stated previously, the site is divided into two separate threshold discharge areas, denoted as the North TDA and the South TDA. Below is a description of the downstream drainage system from the project area to a distance of approximately one-quarter mile downstream for each TDA. Refer to Figure 5 – Downstream Drainage Map for details. North TDA The North TDA includes portions of the building roof, the northern parking lots and driveways, the softball and baseball fields, and the 128th Ave SE frontage. Runoff on site is collected by catch basins and coveyed to the northwest corner of the property via two separate piped systems before discharging to catch basins on the east side of 128th Ave SE. Runoff from the frontage is collected by catch basins and conveyed north in the public system via 18-inch pipe before combining with flow from the site near the northwest corner of the property. From here, the downstream drainage course is as follows: 1. Runoff flows north in a 12-inch pipe for about 150 feet to a catch basin at the intersection of 128th Ave SE and SE 164th St. 2. Stormwater is then conveyed west in a 24-inch concrete pipe for 410 feet to a catch basin along the south side of 164th St. 3. From here, runoff continues west in a 24-inch corrugated polyethylene pipe for 333 feet to a catch basin at the intersection of 127th Ave SE and SE 164th St. 4. Flow then travels north in a 36-inch concrete pipe for 258 feet to a catch basin on the west side of 127th Ave SE. 5. From this catch basin, runoff is conveyed west for 393 feet, passing the quarter-mile downstream point before entering a catch basin near the entrance to Cascade Park. 6. From here, stormwater flows west in a 36-inch corrugated metal pipe to a catch basin in Cascade Park before continuing to the north west and eventually discharging to Ginger Creek near the north end of the park. Ginger Creek is a tributary of the Cedar River. South TDA The South TDA includes flow from portions of the building roof, the southwest parking lot and driveway, the tennis courts, and the track and field. Runoff from the southeast parking lot is treated by several existing Filterra water quality facilities and then routed to a detention facility. There is also a detention facility near the southeast corner of the building which mitigates portions of the building roof and north parking lot cul-de-sac. This South TDA storm system leaves the site at the southeast corner of the property in a 15-inch corrugated metal pipe, traveling east for about 165 feet before discharging to a LPD Engineering PLLC Page 7 Lindbergh HS – Modernization and Additions Revised Technical Information Report, October 26, 2022 privately owned catch basin on the west side of 132nd Place SE. From here, the downstream drainage course is as follows: 7. Flow continues northeast in the 15-inch private storm system for about 190 feet before discharging to Molasses Creek within a single-family residential property. 8. Molasses Creek generally flows north, passing the quarter-mile downstream point near the cul-de-sac at the end of 133rd Place SE. Molasses creek continues north, crossing SE Fairwood Boulevard and SE 163rd St in a 48-inch corrugated metal culvert and eventually discharges to the cedar river. Task 5 – Mitigation of Existing or Potential Problems During the field investigation there were no signs of erosion or overtopping of the downstream drainage system. At this time, the existing downstream drainage course appears to have adequate capacity to convey the proposed flows from the project. SECTION 4 –LOW IMPACT DEVELOPMENT (LID), FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN Existing Site Hydrology Please refer to Section 1- Project Overview and Section 3- Off-site Analysis of this report for a description of the existing hydrology. Developed Site Hydrology Please refer to Section 1- Project Overview and the Flow Control System section below in this report for a description of the proposed hydrology. Performance Standards Please refer to Section 2- Conditions and Requirements Summary, and the On-Site BMPs, Flow Control System, and Water Quality sections of this report for a description of the required standards applicable to this report. Flow Control Facility Standard As stated previously, the project site is located within Flow Control Duration Standard area. Therefore, the flow duration of predeveloped rates for forested (historical) site conditions over the range of flows extending from 50% of 2-year up to the full 50- year flow AND matches peaks for the 2- and 10-year return periods. Per Section 1.2.3.1.B. of the 2017 RSWDMA, below is a description and evaluation of the target surfaces for this project: 1. New impervious surface that is not fully dispersed per the criteria on Section 1.2.3.2.C, as specified in Appendix C. For individual lots within residential subdivision projects, the extent of new impervious surface shall be assumed as specified in Chapter 3. Note, any new impervious surface such as a bridge or boardwalk that spans the ordinary high water of a stream, pond, or lake may be excluded as a target surface if the runoff from such span is conveyed to the ordinary high water area in accordance with Criteria (b), (c), (d), and (e) of the "Direct Discharge Exemption" (p 1-39) LPD Engineering PLLC Page 8 Lindbergh HS – Modernization and Additions Revised Technical Information Report, October 26, 2022 Interpretation: New impervious surfaces that cannot be fully dispersed are considered to be a target surface. 2. New pervious surface that is not fully dispersed as specified in Appendix C. For individual lots within residential subdivision projects, the extent of new pervious surface shall be assumed to be the entire lot area, except the assumed impervious portion and any portion in which native conditions are preserved by covenant, tract, or easement. In addition, the new pervious surface on individual lots shall be assumed to be 100% grass. Interpretation: The definition of new pervious surface from the 2017 RSWDMA includes the conversion of a native vegetated surface or other native surface to non-native pervious surface (e.g. conversion of forest or meadow to pasture land, grass land, cultivated land, lawn, landscaping, bare soils, etc.), or any alteration of existing non-native pervious surface that significantly increases surface and storm water runoff (e.g., conversion of pasture land, grass land, or cultivated land to lawn, landscaping, or bare soil). The majority of the landscape improvements will be amended as lawn area which are in areas where the existing site was non-native lawn. 3. Replaced impervious surface that is not fully dispersed as specified in Appendix C on a non-redevelopment project in which the total of new plus replaced impervious surface is 5,000 square feet or more, OR new pervious surface is ¾ acre or more. Interpretation: Since the project is a redevelopment project, this item does not apply to this project. 4. Replaced impervious surface that is not fully dispersed on a transportation redevelopment project in which new impervious surface is 5,000 square feet or more and totals 50% or more of the existing impervious surface within the project limits. Interpretation: Since the project is not a transportation redevelopment project, this item does not apply to this project. 5. Replaced impervious surface that is not fully dispersed as specified in Appendix C, on a parcel redevelopment project in which the total of new plus replaced impervious surface is 5,000 square feet or more and whose valuation of proposed improvements (including interior improvements and excluding required mitigation improvements) exceeds 50% of the assessed value of the existing site improvements. Interpretation: The project is a redevelopment but the proposed improvements do not exceed 50% of the value of the existing site improvements. Therefore, this item does not apply to this project. As determined above, new impervious surfaces, and new pervious surfaces not fully dispersed are considered the “target surface” requiring flow control mitigation and BMPs. Water Quality Treatment Standards As described in Section 2 of this report, the project meets Exemption 3 in Section 1.2.8 of the RSWDMA and is not required to provide water quality facilities. However, due to the lack of feasibility for establishment of On-site BMPs, the owner will be providing water quality treatment for a portion of the LPD Engineering PLLC Page 9 Lindbergh HS – Modernization and Additions Revised Technical Information Report, October 26, 2022 replaced parking lot to improve the quality of stormwater runoff leaving the site. See section below for details. On-Site BMPs Per Core Requirement #9, the project site proposed more than 2,000 SF of new plus replaced impervious surfaces which will require an evaluation of BMP feasibility for all target surfaces. Per section 1.2.9.2 of the 2017 RSWDMA, this project will be subject to Large Lot BMP Requirements since the project site is larger than 22,000 SF. For each TDA, the feasibility of on-site BMPs must be evaluated for each BMP listed in Section 1.2.9.2.2 of the RSWDMA. Due to the fill and lodgement till found on the project site, there is no suitable stormwater infiltration receptor for infiltration BMPs. For these reasons, the LID performance standard cannot be achieved. Below is the alternate BMP list approach for the site and frontage improvements within the two TDAs. North and South TDA BMP Evaluation: 1. Full Dispersion: Full dispersion of runoff from target surfaces is not feasible for both the site area and road frontage according to Section C.2.1.1 of the RSWDMA due to the limited native vegetated surface downstream of each of these areas on site. 2. Full Infiltration of Roof Runoff: Per the geotechnical report, the site soils consist of fill and lodgment till which are not suitable stormwater infiltration receptors. Infiltration is not recommended by the Geotechnical Engineer. 3. Since the target impervious surfaces could not be mitigated by Requirements 1 and 2 above, the following has been reviewed and implemented where feasible: • Full Infiltration: Full infiltration of runoff from target surfaces is not feasible. As stated above: fill and lodgement till soils are not suitable as stormwater infiltration receptors; and stormwater infiltration is not recommended by the Geotechnical Engineer. • Limited Infiltration: As stated above: fill and lodgement till soils are not suitable as stormwater infiltration receptors; and stormwater infiltration is not recommended by the Geotechnical Engineer. Therefore, limited infiltration is considered infeasible. • Bioretention: Per Section C.2.6, bioretention facilities without underdrains are considered infeasible as stated above due to fill and lodgement till soils which are not suitable as stormwater infiltration receptors. Underdrains are not permitted by the City to meet Core Requirement #9. • Permeable Pavement: As stated above: fill and lodgement till soils are not suitable as stormwater infiltration receptors; and stormwater infiltration is not recommended by the Geotechnical Engineer. 4. Basic Dispersion: is not feasible to be used as BMP per Section C.2.4 of the RSWDMA due to the limited vegetative flow path downstream of the target surfaces. Flow Control Analysis and Design As previously mentioned, the project is required to meet the forested Flow Control Duration standard. However, flow control facilities are not required because the project meets Exception 3 in Section 1.2.3 B of the RSWDMA which states: LPD Engineering PLLC Page 10 Lindbergh HS – Modernization and Additions Revised Technical Information Report, October 26, 2022 The facility requirement in Flow Control Duration Standard Matching Forested Site Conditions Areas is waived for any threshold discharge area in which there is no more than a 0.15-cfs difference (when modeled using 15 minute time steps) in the sum of developed 100-year peak flows for those target surfaces subject to this requirement and the sum of forested (historical) site conditions 100-year peak flows (modeled using same time step unit (e.g., 15 minute) used to calculate the developed flow) for the same surface areas. As previously determined, the target surfaces required to be evaluated against this threshold include the new impervious surfaces, and new pervious surfaces not fully dispersed. The project does not propose any new pervious surfaces. In coordination with the City, due to the frontage improvement requirements, the existing impervious area to be removed and replaced with vegetated area has been subtracted from the total new targeted impervious surfaces. The project is divided into two TDAs. Refer to Figure 4 – Proposed Conditions for a clear delineation of the TDAs and the target surfaces. Stormwater modeling was conducted using MGSFlood Version 4, an approved continuous-modeling software by the RSWDMA. The MGSFlood output is attached in Appendix B. North TDA The North TDA includes 3,328 SF of new impervious surface. As shown in the table below, this area causes no more than a 0.15 cfs difference in the 100-year peak flow. Therefore, flow control facilities are not required in the North TDA. Table 1 – North TDA 100-Year Peak Flow Increase Storm Event (15-Minute Timesteps) Historic Conditions (Forested) Proposed Conditions (Impervious) Delta 100-yr 0.0062 cfs 0.0885 cfs 0.0823 cfs South TDA The South TDA includes 1,544 SF of new impervious surface. As shown in the table below, this area causes no more than a 0.15 cfs difference in the 100-year peak flow. Therefore, flow control facilities are not required in the South TDA. Table 1 – South TDA 100-Year Peak Flow Increase EStorm Event (15-Minute Timesteps) Historic Conditions (Forested) Proposed Conditions (Impervious) Delta 100-yr 0.00283 cfs 0.0407 cfs 0.0379 cfs LPD Engineering PLLC Page 11 Lindbergh HS – Modernization and Additions Revised Technical Information Report, October 26, 2022 Frontage There will be replaced pavement in the frontage associated with curb ramp and asphalt roadway replacement. The total amount of replaced hard surface in the frontage is 10,116 SF (0.232 acres). As mentioned, all of these are replaced hard surfaces, and thus not counted as part of the target surface for consideration in flow control evaluation in the previous models. The areas of replacement are diagrammatically shown on Figure 4. Water Quality Design As previously mentioned, the project is not required to provide water quality treatment. However, due to the lack of feasibility for establishment of On-site BMPs. The owner will be providing water quality treatment for a portion of the replaced parking lot. Water Quality Treatment will be provided by Contech’s Filterra systems. Contech’s Filterra systems have been reviewed and certified by the Washington State Technology Assessment Protocol – Ecology program (TAPE). The area of the parking lot to be treated totals 10,390 SF which include the majority of the western most parking bay. The Filterra water quality treatment facility is approximately 4-feet by 4-feet in dimension and will connect to the existing downstream stormwater system within the parking lot. Refer to Appendix B for MGSFlood results and sizing calculations of the Filterra system. SECTION 5 – CONVEYANCE SYSTEMS ANALYSIS AND DESIGN An analysis of the onsite conveyance system was performed for the South TDA and the North TDA. Refer to the Conveyance Analysis Spreadsheet and accompanying MGS Flood reports included in Appendix B. Per section 1.2.4.1 of the 2017 RSWDMA, the conveyance system shall be designed to accommodate the 25-year storm event. The 25-year peak runoff rates were compared with the full-flow capacity of the conveyance pipe. The peak runoff rates from each of the tributary areas were determined using MGS Flood with 15-minute time steps. The full flow capacity of the conveyance pipe was determined using Manning’s equation. South TDA For the parking lot replacement, there is an existing 12-inch pipe that is the point of discharge (Pipe Run #1). The 12-inch pipe with Manning’s n value of 0.011, at 0.7% slope yields full-flow capacity of 3.53 cubic feet per second (cfs). The 25-year and the 100-year peak flows from MGSFlood were found to be under the pipe’s capacity limitations. North TDA For the science classroom additions, there is an existing 12-inch pipe that is the point of discharge ( Pipe Run #2). The 12-inch pipe with Manning’s n value of 0.011, at 0.5% slope yields full-flow capacity of 2.99 cubic feet per second (cfs). The 25-year and the 100-year peak flows from MGSFlood were found to be under the pipe’s capacity limitations. SECTION 6 – SPECIAL REPORTS AND STUDIES A geotechnical report has been prepared by Associated Earth Sciences, Inc (AESI). dated February 7, 2022. AESI also prepared a subsequent limited geotechnical engineering study for the parking lot, dated January 3, 2022. Both have been added to Appendix E of this report. LPD Engineering PLLC Page 12 Lindbergh HS – Modernization and Additions Revised Technical Information Report, October 26, 2022 SECTION 7 – OTHER PERMITS Coverage under the Construction Stormwater General Permit through the Department of Ecology will be required for the project because it disturbs over one (1) acre of land area. The NOI and public noticing required for this permit will be completed later in the design process, prior to construction. SECTION 8 – CSWPPP ANALYSIS AND DESIGN The construction storm water pollution prevention plan (CSWPPP) consists of the TESC plan in the drawing set and a Stormwater Pollution Prevention Plan narrative (SWPPP) based upon Ecology’s Construction Stormwater General Permit SWPPP Template which is provided in Appendix C. The TESC plan includes temporary sediment settling tanks, sized using the methodology from the 2017 RSWDMA. A copy of the Sediment Facility Sizing Calculations worksheet and the associated output from MGS Flood used for the sediment tank sizing are included in Appendix B. SECTION 9 – BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT Bond quantities for the project have been submitted under separate cover. The Facility Summary Sheet and Declaration of Covenant are attached in Appendix F SECTION 10 – OPERATIONS AND MAINTENANCE MANUAL The Operations and Maintenance Manual is provided in Appendix D of this report. This will include maintenance recommendations associated with the conveyance pipes, catch basins, and Filterra (water quality facility). FIGURES Figure 1: TIR Worksheet Figure 2: Vicinity Map Figure 3: Existing Conditions Figure 4: Proposed Conditions Figure 5: Downstream Drainage Map KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND PROJECT ENGINEER Part 2 PROJECT LOCATION AND DESCRIPTION Project Owner ___________________________ Phone _________________________________ Address _______________________________ _______________________________________ Project Engineer _________________________ Company ______________________________ Phone _________________________________ Project Name _________________________ DPER Permit # ________________________ Location Township ______________ Range ________________ Section ________________ Site Address __________________________ _____________________________________ Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS  Landuse (e.g.,Subdivision / Short Subd. / UPD)  Building (e.g.,M/F / Commercial / SFR)  Clearing and Grading  Right-of-Way Use  Other _______________________  DFW HPA  COE 404  DOE Dam Safety  FEMA Floodplain  COE Wetlands  Other ________  Shoreline Management  Structural Rockery/Vault/_____  ESA Section 7 Part 5 PLAN AND REPORT INFORMATION Technical Information Report Site Improvement Plan (Engr. Plans) Type of Drainage Review (check one): Date (include revision dates): Date of Final:  Full  Targeted  Simplified  Large Project  Directed ____________________________________ __________________ Plan Type (check one): Date (include revision dates): Date of Final:  Full  Modified  Simplified ____________________________________ __________________ Part 6 SWDM ADJUSTMENT APPROVALS Type (circle one): Standard / Experimental / Blanket Description: (include conditions in TIR Section 2) ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ Approved Adjustment No. ______________________ Date of Approval: ______________________ 2016 Surface Water Design Manual 4/24/2016 1 Renton School District (425) 204-2340 300 South 7th Street Renton, WA 98057 Laurie Pfarr, PE LPD Engineering, PLLC (206) 725-1211 Lindbergh HS 23 North 5 East 10 Duvall Avenue NE Renton, WA 98059 X X X KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 7 MONITORING REQUIREMENTS Monitoring Required: Yes / No Start Date: _______________________ Completion Date: _______________________ Describe: _________________________________ _________________________________________ _________________________________________ Re: KCSWDM Adjustment No. ________________ Part 8 SITE COMMUNITY AND DRAINAGE BASIN Community Plan : ____________________________________________________________________ Special District Overlays: ______________________________________________________________ Drainage Basin: _____________________________________________________________________ Stormwater Requirements: ____________________________________________________________ Part 9 ONSITE AND ADJACENT SENSITIVE AREAS  River/Stream ________________________  Lake ______________________________  Wetlands ____________________________  Closed Depression ____________________  Floodplain ___________________________  Other _______________________________ _______________________________  Steep Slope __________________________  Erosion Hazard _______________________  Landslide Hazard ______________________  Coal Mine Hazard ______________________  Seismic Hazard _______________________  Habitat Protection ______________________  _____________________________________ Part 10 SOILS Soil Type _________________ _________________ _________________ _________________ Slopes _________________ _________________ _________________ _________________ Erosion Potential _________________ _________________ _________________ _________________  High Groundwater Table (within 5 feet)  Other ________________________________  Sole Source Aquifer  Seeps/Springs  Additional Sheets Attached 2016 Surface Water Design Manual 4/24/2016 2 N/A N/A N/A Molasses Creek; Ginger Creek Alderwood gravelly sandy loam 8 to 15 % KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 11 DRAINAGE DESIGN LIMITATIONS REFERENCE  Core 2 – Offsite Analysis_________________  Sensitive/Critical Areas__________________  SEPA________________________________  LID Infeasibility________________________  Other________________________________  _____________________________________ LIMITATION / SITE CONSTRAINT _______________________________________ _______________________________________ _______________________________________ _______________________________________ _______________________________________ _______________________________________  Additional Sheets Attached Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Threshold Discharge Area: (name or description) Core Requirements (all 8 apply): Discharge at Natural Location Number of Natural Discharge Locations: Offsite Analysis Level: 1 / 2 / 3 dated:__________________ Flow Control (include facility summary sheet) Level: 1 / 2 / 3 or Exemption Number ____________ Flow Control BMPs _______________________________ Conveyance System Spill containment located at: _________________________ Erosion and Sediment Control / Construction Stormwater Pollution Prevention CSWPP/CESCL/ESC Site Supervisor: _____________________ Contact Phone: _________________________ After Hours Phone: _________________________ Maintenance and Operation Responsibility (circle one): Private / Public If Private, Maintenance Log Required: Yes / No Financial Guarantees and Liability Provided: Yes / No Water Quality (include facility summary sheet) Type (circle one): Basic / Sens. Lake / Enhanced Basic / Bog or Exemption No. ______________________ Landscape Management Plan: Yes / No Special Requirements (as applicable): Area Specific Drainage Requirements Type: CDA / SDO / MDP / BP / LMP / Shared Fac. / None Name: ________________________ Floodplain/Floodway Delineation Type (circle one): Major / Minor / Exemption / None 100-year Base Flood Elevation (or range): ______________ Datum: Flood Protection Facilities Describe: 2016 Surface Water Design Manual 4/24/2016 3 N/A 3 N/A #1 KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Source Control (commercial / industrial land use) Describe land use: Describe any structural controls: Oil Control High-use Site: Yes / No Treatment BMP: ________________________________ Maintenance Agreement: Yes / No with whom? ____________________________________ Other Drainage Structures Describe: Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION  Clearing Limits  Cover Measures  Perimeter Protection  Traffic Area Stabilization  Sediment Retention  Surface Water Collection  Dewatering Control  Dust Control  Flow Control  Protection of Flow Control BMP Facilities (existing and proposed)  Maintain BMPs / Manage Project MINIMUM ESC REQUIREMENTS AFTER CONSTRUCTION  Stabilize exposed surfaces  Remove and restore Temporary ESC Facilities  Clean and remove all silt and debris, ensure operation of Permanent Facilities, restore operation of Flow Control BMP Facilities as necessary  Flag limits of SAO and open space preservation areas  Other ______________________ Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and Sketch) Flow Control Type/Description Water Quality Type/Description  Detention  Infiltration  Regional Facility  Shared Facility  Flow Control BMPs  Other ________________ ________________ ________________ ________________ ________________ ________________  Vegetated Flowpath  Wetpool  Filtration  Oil Control  Spill Control  Flow Control BMPs  Other ________________ ________________ ________________ ________________ ________________ ________________ ________________ 2016 Surface Water Design Manual 4/24/2016 4 X Filterra KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS  Drainage Easement  Covenant  Native Growth Protection Covenant  Tract  Other ___________________________  Cast in Place Vault  Retaining Wall  Rockery > 4’ High  Structural on Steep Slope  Other ______________________________ Part 17 SIGNATURE OF PROFESSIONAL ENGINEER I, or a civil engineer under my supervision, have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attached Technical Information Report. To the best of my knowledge the information provided here is accurate. Signed/Date 2016 Surface Water Design Manual 4/24/2016 5 4/15/22 engineering pllc 1932 1st Ave, Suite 201, Seattle, WA 98101 p. 206.725.1211 f. 206.973.5344 www.lpdengineering.com LINDBERGH HIGH SCHOOL 2VICINITY MAP 1932 1st Ave,Suite 201,Seattle, WA 98101p. 206.725.1211f. 206.973.5344www.lpdengineering.comengineering pllc2022 LPD Engineering PLLC©LINDBERGH HIGH SCHOOL3EXISTING CONDITIONS NO PARKING FIRE LANE 1932 1st Ave,Suite 201,Seattle, WA 98101p. 206.725.1211f. 206.973.5344www.lpdengineering.comengineering pllc2022 LPD Engineering PLLC©LINDBERGH HIGH SCHOOL4PROPOSED CONDITIONS engineering pllc2022 LPD Engineering PLLC©LINDBERGH HIGH SCHOOL51932 1st Ave,Suite 201,Seattle, WA 98101p. 206.725.1211f. 206.973.5344www.lpdengineering.comDOWNSTREAM DRAINAGEMAPAPPROXIMATE TDABOUNDARYSOUTH TDA15" CMP48" CMP18" CONC12" CONC24" CONC24" CPEP36" CONC36" CMPEX DETENTIONFACILITYEX DETENTIONFACILITYEX WATER QUALITYFACILITIESSOUTH TDA DISCHARGEPOINT FROM PROPERTYNORTH TDA DISCHARGEPOINTS FROM PROPERTYAPPROXIMATELY 1/4 MILEDOWNSTREAM FROM SITEAPPROXIMATELY 1/4 MILEDOWNSTREAM FROM SITEPROJECT AREALIMITS (TYP)MOLASSESCREEKEVENTUALDISCHARGE TOGINGER CREEKAND CEDAR RIVEREVENTUAL DISCHARGETO CEDAR RIVERDISCHARGE TOMOLASSES CREEKNORTH TDACASCADE PARK APPENDIX A Design Drawings NO PARK IN G F I RE L A N E IN COMPLIANCE WITH CITY OF RENTON STANDARDSTED-40-4221LUA22-000106PR22-000038C22002856LAURIEJ.PFA R R LINDBERGH HS MODERNIZATION AND ADDITIONSR-422102 IN COMPLIANCE WITH CITY OF RENTON STANDARDSTED-40-4221LUA22-000106PR22-000038C22002856LAURIEJ.PFA R R LINDBERGH HS MODERNIZATION AND ADDITIONSR-422103 IN COMPLIANCE WITH CITY OF RENTON STANDARDSTED-40-4221LUA22-000106PR22-000038C22002856LAURIEJ.PFA R R LINDBERGH HS MODERNIZATION AND ADDITIONSR-422104 IN COMPLIANCE WITH CITY OF RENTON STANDARDSTED-40-4221LUA22-000106PR22-000038C22002856LAURIEJ.PFA R R LINDBERGH HS MODERNIZATION AND ADDITIONSR-422105 NO PARKING FIRE LANEIN COMPLIANCE WITH CITY OF RENTON STANDARDSTED-40-4221LUA22-000106PR22-000038C22002856LAURIEJ.PFA R R LINDBERGH HS MODERNIZATION AND ADDITIONSR-422106 IN COMPLIANCE WITH CITY OF RENTON STANDARDSTED-40-4221LUA22-000106PR22-000038C22002856LAURIEJ.PFA R R LINDBERGH HS MODERNIZATION AND ADDITIONSR-422107 IN COMPLIANCE WITH CITY OF RENTON STANDARDSTED-40-4221LUA22-000106PR22-000038C22002856LAURIEJ.PFA R R LINDBERGH HS MODERNIZATION AND ADDITIONSR-422108 IN COMPLIANCE WITH CITY OF RENTON STANDARDSTED-40-4221LUA22-000106PR22-000038C22002856LAURIEJ.PFA R R LINDBERGH HS MODERNIZATION AND ADDITIONSR-422109 IN COMPLIANCE WITH CITY OF RENTON STANDARDSTED-40-4221LUA22-000106PR22-000038C22002856LAURIEJ.PFA R R LINDBERGH HS MODERNIZATION AND ADDITIONSR-422110 IN COMPLIANCE WITH CITY OF RENTON STANDARDSTED-40-4221LUA22-000106PR22-000038C22002856LAURIEJ.PFA R R LINDBERGH HS MODERNIZATION AND ADDITIONSR-422111 NO PARK IN G F I RE L A N E SL1SL1SL1SL1SL1SL1SL1SL11. REFER TO CIVIL, LANDSCAPE AND SURVEY DRAWINGS FO2. COORDINATE PLACEMENT OF SITE LIGHTING, VAULTS ANDLANDSCAPE CONTRACTORS. COORDINATE WITH TREE PREXISTING TREES. COMMUNICATE CONFLICTS TO THE ARCWORK.3. COORDINATE STREET LIGHTING CIRCUIT EXTENSION WITHCOMPLY WITH PSE'S ELECTRICAL INSTALLATION REQUIREJENNY.CHAU@PSE.COM FOR ADDITIONAL REQUIREMENTS4. PROVIDE 2"C AND #8 AWG MINIMUM CONDUCTOR SIZE FOSHEET, UNLESS OTHERWISE NOTED.5. PROVIDE UNDERGROUND CONDUIT PER TRENCHING DETA6. PROVIDE CONCRETE BASE FOR STREET LIGHTING POLESCONCRETE BASES FOR STREET LIGHTING. COORDINATE WAPPROVAL PRIOR TO PROCUREMENT.7. REFER TO VAULT SCHEDULE ON THIS SHEET FOR VAULT TADDITIONAL INFORMATION.FLAG NOTES:SHEET NOTES:SEE CITY OF RENTON DETAIL 121, 117.1A, 117.2, ANSEE CITY OF RENTON DETAIL 117.1, 117.3, AND 121 SEE CITY OF RENTON DETAIL 119 AND 120 FOR MORCOORDINATE INSTALLATION OF LUMINAIRE CONCRRETAINING WALL.CONDUIT AND CONDUCTORS FURNISHED AND INSTSAWCUT AND TRENCH ACROSS THE EXISTING ROAMATERIAL FURNISHED AND INSTALLED BY UTILITY. EXCAVATION AND BACKFILL.1STREET LIGHTING NOTES:1. THE CONTRACTOR SHALL ACQUIRE AN ELECTRICAL PERM2. UPON COMPLETION OF UNDERGROUND INSTALLATION OCABINET, NOTIFY THE BUILDING DEPARTMENT. UPON FININSPECTOR WILL PLACE AN APPROVAL TAG NEXT TO THEAUTHORIZED.3. COORDINATE POWER SOURCE AND SERVICE LOCATION W4. CONTACT THE UTILITIES UNDERGROUND LOCATION CENTEARTHWORK.5. SEE CITY OF RENTON MUNICIPAL CODE AND SECTION J ILINFORMATION.6. SEE STREET LIGHTING DETAILS ON SHEETS E7.03 AND E77. LOCATE LIGHT POLE BASES, JUNCTION BOXES, AND CONMUNICIPAL STANDARDS AND ALLOWING FOR SL1 LUMINAREQUIREMENTS.234566VAULT SCHEDULEVAULT TYPE MANUFACTURER VAULT MODEL COVER MODELV1OLDCASTLETYPE-1 -MNOTES1.COORDINATE WITH CITY OF RENTON REQUIREMENTS STANDARDS 1191234417567777SL1IN COMPLIANCE WITH CITY OF RENTON STANDARDSTED-40-4221LUA22-000106PR22-000038C22002856LAURIEJ.PFA R R LINDBERGH HS MODERNIZATION AND ADDITIONSR-422112 IN COMPLIANCE WITH CITY OF RENTON STANDARDSTED-40-4221LUA22-000106PR22-000038C22002856LAURIEJ.PFA R R LINDBERGH HS MODERNIZATION AND ADDITIONSR-422113 IN COMPLIANCE WITH CITY OF RENTON STANDARDSTED-40-4221LUA22-000106PR22-000038C22002856LAURIEJ.PFA R R LINDBERGH HS MODERNIZATION AND ADDITIONSR-422114 IN COMPLIANCE WITH CITY OF RENTON STANDARDSTED-40-4221LUA22-000106PR22-000038C22002856LAURIEJ.PFA R R LINDBERGH HS MODERNIZATION AND ADDITIONSR-422115 NO PARKING FI RE LANEIN COMPLIANCE WITH CITY OF RENTON STANDARDSTED-40-4221LUA22-000106PR22-000038C22002856LAURIEJ.PFA R R LINDBERGH HS MODERNIZATION AND ADDITIONSR-422116 IN COMPLIANCE WITH CITY OF RENTON STANDARDSTED-40-4221LUA22-000106PR22-000038C22002856LAURIEJ.PFA R R LINDBERGH HS MODERNIZATION AND ADDITIONSR-4221INLET SHAPING(NOT BY CONTECH)CURB(NOT BY CONTECH)AAVAULT WIDTHPLAN VIEWSECTION A-ASDR 35 OUTLET COUPLING CAST INTO PRECAST VAULT WALL(OUTLET PIPE LOCATION MAY VARY)TREE FRAME AND GRATECAST INTO TOP SLABTOP SLABENERGY DISSIPATION ROCKSGALVANIZED ANGLE NOSINGCURB AND GUTTER(NOT BY CONTECH)SEE FILTERRA STANDARDOFFLINE CURB INLET DETAILSHEETSTREET4" - 6"Ø UNDERDRAINFLOWKIT (VARIES BY SIZE)PROVIDED BY CONTECH21" FILTERRA MEDIA, TYP.PROVIDED BY CONTECH6" UNDERDRAINSTONE LAYER, TYP.PROVIDED BY CONTECH3" MULCH LAYER, TYP.PROVIDED BY CONTECHTREE GRATECLEAN OUTCURB INLETOPENINGSTREETPLANT PROVIDED BY CONTECH2"Ø IRRIGATIONPORT, TYP.3 PLACES17 IN COMPLIANCE WITH CITY OF RENTON STANDARDSTED-40-4221LUA22-000106PR22-000038C22002856LAURIEJ.PFA R R LINDBERGH HS MODERNIZATION AND ADDITIONSR-422118 APPENDIX B Design Calculations and Supporting Information Lindbergh HSAreas Spreadsheet - NORTH TDAExisting ConditionsNORTH TDA: Area SummaryPervious[SF]Impervious[SF][AC]PGIS6,2320.143NPGIS25,1880.578Total Existing Impervious31,4200.721Total Existing Pervious 44,6311.025Total Basin Disturbed1.746Proposed ConditionsNORTH TDA: Area SummaryPervious[SF]Impervious[SF][AC]Landscape Area41,303 0.948PGIS6,3010.145NPGIS28,4470.653Total New Plus Replaced Impervious34,7480.798Total Pervious41,3030.948Total Basin Disturbed1.746Total Target Areas (New Impervious)0.07676,0513,32876,051 Lindbergh HSAreas Spreadsheet - SOUTH TDAExisting ConditionsSOUTH TDA: Area SummaryPervious[SF]Impervious[SF][AC]PGIS59,6721.370NPGIS2800.006Total Impervious59,9521.376Total Pervious22,6340.520Total Basin Disturbed1.896Modeled Proposed ConditionsSOUTH TDA: Area SummaryPervious[SF]Impervious[SF][AC]Landscape Area21,090 0.484PGIS60,8411.397NPGIS6550.015Total Impervious61,4961.412Total Pervious 21,0900.484Total Basin Disturbed1.896Total Target Areas (New Impervious)0.035SUBBASIN: to WQ FacilityPervious[SF]Impervious[SF][AC]PGIS10,3900.23982,5861,54482,586 ————————————————————————————————— MGS FLOOD PROJECT REPORT – North TDA FC Exemption Program Version: MGSFlood 4.57 Program License Number: 201410003 Project Simulation Performed on: 05/20/2022 5:25 PM Report Generation Date: 05/20/2022 5:25 PM ————————————————————————————————— Input File Name: North TDA Flow Increase.fld Project Name: Lindbergh HS Analysis Title: North TDA Flow Increase Comments: ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Climatic Region Number: 16 Full Period of Record Available used for Routing Precipitation Station : 96004405 Puget East 44 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961044 Puget East 44 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : Ecology Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 0.076 0.076 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 0.076 0.076 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Predev ---------- -------Area (Acres) -------- C, Forest, Flat 0.076 ---------------------------------------------- Subbasin Total 0.076 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Postdev ---------- -------Area (Acres) -------- SIDEWALKS/FLAT 0.076 ---------------------------------------------- Subbasin Total 0.076 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 0 **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 0 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Predev 14.463 _____________________________________ Total: 14.463 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Postdev 0.000 _____________________________________ Total: 0.000 Total Predevelopment Recharge is Greater than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 0.092 ac-ft/year, Post Developed: 0.000 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Links: 0 ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Predev Scenario Postdeveloped Compliance Subbasin: Postdev *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 1.914E-03 2-Year 3.120E-02 5-Year 3.015E-03 5-Year 4.021E-02 10-Year 3.751E-03 10-Year 4.736E-02 25-Year 5.167E-03 25-Year 5.932E-02 50-Year 5.673E-03 50-Year 7.108E-02 100-Year 6.150E-03 100-Year 8.851E-02 200-Year 9.104E-03 200-Year 9.432E-02 500-Year 1.307E-02 500-Year 0.102 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals ————————————————————————————————— MGS FLOOD PROJECT REPORT - South TDA FC Exemption Program Version: MGSFlood 4.57 Program License Number: 201410003 Project Simulation Performed on: 04/14/2022 1:33 PM Report Generation Date: 04/14/2022 1:33 PM ————————————————————————————————— Input File Name: South TDA Flow Increase.fld Project Name: Lindbergh HS Analysis Title: South TDA Flow Increase Comments: ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Climatic Region Number: 16 Full Period of Record Available used for Routing Precipitation Station : 96004405 Puget East 44 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961044 Puget East 44 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : Ecology Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 0.035 0.035 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 0.035 0.035 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Predev ---------- -------Area (Acres) -------- C, Forest, Flat 0.035 ---------------------------------------------- Subbasin Total 0.035 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Postdev ---------- -------Area (Acres) -------- SIDEWALKS/FLAT 0.035 ---------------------------------------------- Subbasin Total 0.035 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 0 **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 0 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Predev 6.661 _____________________________________ Total: 6.661 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Postdev 0.000 _____________________________________ Total: 0.000 Total Predevelopment Recharge is Greater than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 0.042 ac-ft/year, Post Developed: 0.000 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Links: 0 ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Predev Scenario Postdeveloped Compliance Subbasin: Postdev *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 8.813E-04 2-Year 1.437E-02 5-Year 1.388E-03 5-Year 1.852E-02 10-Year 1.727E-03 10-Year 2.181E-02 25-Year 2.380E-03 25-Year 2.732E-02 50-Year 2.613E-03 50-Year 3.274E-02 100-Year 2.832E-03 100-Year 4.076E-02 200-Year 4.193E-03 200-Year 4.344E-02 500-Year 6.021E-03 500-Year 4.687E-02 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals 1 June 2020 GENERAL USE LEVEL DESIGNATION FOR BASIC (TSS), ENHANCED, PHOSPHORUS & OIL TREATMENT For CONTECH Engineered Solutions Filterra® Ecology’s Decision: Based on Contech’s submissions, including the Final Technical Evaluation Reports, dated August 2019, March 2014, December 2009, and additional information provided to Ecology dated October 9, 2009, Ecology hereby issues the following use level designations: 1. A General Use Level Designation for Basic, Enhanced, Phosphorus, and Oil Treatment for the Filterra® system constructed with a minimum media thickness of 21 inches (1.75 feet), at the following water quality design hydraulic loading rates: Treatment Infiltration Rate (in/hr) for use in Sizing Basic 175 Phosphorus 100 Oil 50 Enhanced 175 2. The Filterra is not appropriate for oil spill-control purposes. 3. Ecology approves Filterra systems for treatment at the hydraulic loading rates listed above, and sized based on the water quality design flow rate for an off-line system. Calculate the water quality design flow rates using the following procedures:  Western Washington: for treatment installed upstream of detention or retention, the water quality design flow rate is the peak 15-minute flow rate as calculated using the latest version of the Western Washington Hydrology Model or other Ecology-approved continuous runoff model.  Eastern Washington: For treatment installed upstream of detention or retention, the water quality design flow rate is the peak 15-minute flow rate as calculated using one of the three flow rate based methods described in Chapter 2.7.6 of the Stormwater Management Manual for Eastern Washington (SWMMEW) or local manual.  Entire State: For treatment installed downstream of detention, the water quality design flow rate is the full 2-year release rate of the detention facility. 2 4. This General Use Level Designation has no expiration date, but Ecology may revoke or amend the designation, and is subject to the conditions specified below. Ecology’s Conditions of Use: Filterra systems shall comply with these conditions shall comply with the following conditions: 1. Design, assemble, install, operate, and maintain the Filterra systems in accordance with applicable Contech Filterra manuals and this Ecology Decision. 2. The minimum size filter surface-area for use in Washington is determined by using the design water quality flow rate (as determined in this Ecology Decision, Item 3, above) and the Infiltration Rate from the table above (use the lowest applicable Infiltration Rate depending on the level of treatment required). Calculate the required area by dividing the water quality design flow rate (cu-ft/sec) by the Infiltration Rate (converted to ft/sec) to obtain required surface area (sq-ft) of the Filterra unit. 3. Each site plan must undergo Contech Filterra review before Ecology can approve the unit for site installation. This will ensure that design parameters including site grading and slope are appropriate for use of a Filterra unit. 4. Filterra media shall conform to the specifications submitted to and approved by Ecology and shall be sourced from Contech Engineered Solutions, LLC with no substitutions. 5. Maintenance includes removing trash, degraded mulch, and accumulated debris from the filter surface and replacing the mulch layer. Use inspections to determine the site-specific maintenance schedules and requirements. Follow maintenance procedures given in the most recent version of the Filterra Operation and Maintenance Manual. 6. Maintenance: The required maintenance interval for stormwater treatment devices is often dependent upon the degree of pollutant loading from a particular drainage basin. Therefore, Ecology does not endorse or recommend a “one size fits all” maintenance cycle for a particular model/size of manufactured treatment device.  Contech designs Filterra systems for a target maintenance interval of 6 months in the Pacific Northwest. Maintenance includes removing and replacing the mulch layer above the media along with accumulated sediment, trash, and captured organic materials therein, evaluating plant health, and pruning the plant if deemed necessary.  Conduct maintenance following manufacturer’s guidelines. 7. Filterra systems come in standard sizes. 8. Install the Filterra in such a manner that flows exceeding the maximum Filterra operating rate are conveyed around the Filterra mulch and media and will not resuspend captured sediment. 9. Discharges from the Filterra units shall not cause or contribute to water quality standards violations in receiving waters. 3 Approved Alternate Configurations Filterra Internal Bypass - Pipe (FTIB-P) 1. The Filterra® Internal Bypass – Pipe allows for piped-in flow from area drains, grated inlets, trench drains, and/or roof drains. Design capture flows and peak flows enter the structure through an internal slotted pipe. Filterra® inverted the slotted pipe to allow design flows to drop through to a series of splash plates that then disperse the design flows over the top surface of the Filterra® planter area. Higher flows continue to bypass the slotted pipe and convey out the structure. 2. To select a FTIB-P unit, the designer must determine the size of the standard unit using the sizing guidance described above. Filterra Internal Bypass – Curb (FTIB-C) 1. The Filterra® Internal Bypass –Curb model (FTIB-C) incorporates a curb inlet, biofiltration treatment chamber, and internal high flow bypass in one single structure. Filterra® designed the FTIB-C model for use in a “Sag” or “Sump” condition and will accept flows from both directions along a gutter line. An internal flume tray weir component directs treatment flows entering the unit through the curb inlet to the biofiltration treatment chamber. Flows in excess of the water quality treatment flow rise above the flume tray weir and discharge through a standpipe orifice; providing bypass of untreated peak flows. Americast manufactures the FTIB-C model in a variety of sizes and configurations and you may use the unit on a continuous grade when a single structure providing both treatment and high flow bypass is preferred. The FTIB-C model can also incorporate a separate junction box chamber to allow larger diameter discharge pipe connections to the structure. 2. To select a FTIB-C unit, the designer must determine the size of the standard unit using the sizing guidance described above. Filterra® Shallow 1. The Filterra Shallow provides additional flexibility for design engineers and designers in situations where various elevation constraints prevent application of a standard Filterra configuration. Engineers can design this system up to six inches shallower than any of the previous Filterra unit configurations noted above. 2. Ecology requires that the Filterra Shallow provide a media contact time equivalent to that of the standard unit. This means that with a smaller depth of media, the surface area must increase. 3. To select a Filterra Shallow System unit, the designer must first identify the size of the standard unit using the modeling guidance described above. 4. Once the size of the standard Filterra unit is established using the sizing technique described above, use information from the following table to select the appropriate size Filterra Shallow System unit. 4 Shallow Unit Basic, Enhanced, Phosphorus, and Oil Treatment Sizing Standard Depth Equivalent Shallow Depth 4x4 4x6 or 6x4 4x6 or 6x4 6x6 4x8 or 8x4 6x8 or 8x6 6x6 6x10 or 10x6 6x8 or 8x6 6x12 or 12x6 6x10 or 10x6 13x7 Notes: 1. Shallow Depth Boxes are less than the standard depth of 3.5 feet but no less than 3.0 feet deep (TC to INV). Applicant: Contech Engineered Solutions, LLC. Applicant’s Address: 11815 NE Glenn Widing Drive Portland, OR 97220 Application Documents:  State of Washington Department of Ecology Application for Conditional Use Designation, Americast (September 2006)  Quality Assurance Project Plan Filterra® Bioretention Filtration System Performance Monitoring, Americast (April 2008)  Quality Assurance Project Plan Addendum Filterra® Bioretention Filtration System Performance Monitoring, Americast (June 2008)  Draft Technical Evaluation Report Filterra® Bioretention Filtration System Performance Monitoring, Americast (August 2009)  Final Technical Evaluation Report Filterra® Bioretention Filtration System Performance Monitoring, Americast (December 2009)  Technical Evaluation Report Appendices Filterra® Bioretention Filtration System Performance Monitoring, Americast, (August 2009)  Memorandum to Department of Ecology Dated October 9, 2009 from Americast, Inc. and Herrera Environmental Consultants  Quality Assurance Project Plan Filterra® Bioretention System Phosphorus treatment and Supplemental Basic and Enhanced Treatment Performance Monitoring, Americast (November 2011)  Filterra® letter August 24, 2012 regarding sizing for the Filterra® Shallow System.  University of Virginia Engineering Department Memo by Joanna Crowe Curran, Ph. D dated March 16, 2013 concerning capacity analysis of Filterra® internal weir inlet tray.  Terraphase Engineering letter to Jodi Mills, P.E. dated April 2, 2013 regarding Terraflume Hydraulic Test, Filterra® Bioretention System and attachments.  Technical Evaluation Report, Filterra® System Phosphorus Treatment and Supplemental Basic Treatment Performance Monitoring. March 27th, 2014.  State of Washington Department of Ecology Application for Conditional Use Level Designation, Contech Engineered Solutions (May 2015) 5  Quality Assurance Project Plan Filterra® Bioretention System, Contech Engineered Solutions (May 2015)  Filterra Bioretention System Armco Avenue General Use Level Designation Technical Evaluation Report, Contech Engineered Solutions (August 2019) Applicant’s Use Level Request: General Level Use Designation for Basic (175 in/hr), Enhanced (175 in/hr), Phosphorus (100 in/hr), and Oil Treatment (50 in/hr). Applicant’s Performance Claims: Field-testing and laboratory testing show that the Filterra® unit is promising as a stormwater treatment best management practice and can meet Ecology’s performance goals for basic, enhanced, phosphorus, and oil treatment. Findings of Fact: Field Testing 2015-2019 1. Contech completed field testing of a 4 ft. x 4 ft. Filterra® unit at one site in Hillsboro, Oregon from September 2015 to July 2019. Throughout the monitoring period a total of 24 individual storm events were sampled, of which 23 qualified for TAPE sampling criteria. 2. Contech encountered several unanticipated events and challenges that prevented them from collecting continuous flow and rainfall data. An analysis of the flow data from the sampled events, including both the qualifying and non-qualifying events, demonstrated the system treated over 99 % of the influent flows. Peak flows during these events ranged from 25 % to 250 % of the design flow rate of 29 gallons per minute. 3. Of the 23 TAPE qualified sample events, 13 met requirements for TSS analysis. Influent concentrations ranged from 20.8 mg/L to 83 mg/L, with a mean concentration of 46.3 mg/L. The UCL95 mean effluent concentration was 15.9 mg/L, meeting the 20 mg/L performance goal for Basic Treatment. 4. All 23 TAPE qualified sample events met requirements for dissolved zinc analysis. Influent concentrations range from 0.0384 mg/L to 0.2680 mg/L, with a mean concentration of 0.0807 mg/L. The LCL 95 mean percent removal was 62.9 %, meeting the 60 % performance goal for Enhanced Treatment. 5. Thirteen of the 23 TAPE qualified sample events met requirements for dissolved copper analysis. Influent concentrations ranged from 0.00543 mg/L to 0.01660 mg/L, with a mean concentration of 0.0103 mg/L. The LCL 95 mean percent removal was 41.2 %, meeting the 30 % performance goal for Enhanced Treatment. 6. Total zinc concentrations were analyzed for all 24 sample events. Influent EMCs for total zinc ranged from 0.048 mg/L to 5.290 mg/L with a median of 0.162 mg/L. Corresponding effluent EMCs for total zinc ranged from 0.015 mg/L to 0.067 mg/L with a median of 6 0.029 mg/L. Total event loadings for the study for total zinc were 316.85 g at the influent and 12.92 g at the effluent sampling location, resulting in a summation of loads removal efficiency of 95.9 %. 7. Total copper concentrations were analyzed for all 24 sample events. Influent EMCs for total copper ranged from 0.003 mg/L to 35.600 mg/L with a median value of 0.043 mg/L. Corresponding effluent EMCs for total copper ranged from 0.002 mg/L to 0.015 mg/L with a median of 0.004 mg/L. Total event loadings for total copper for the study were 1,810.06 g at the influent and 1.90 g at the effluent sampling location, resulting in a summation of loads removal efficiency of 99.9 %. Field Testing 2013 1. Filterra completed field-testing of a 6.5 ft x 4 ft. unit at one site in Bellingham, Washington. Continuous flow and rainfall data collected from January 1, 2013 through July 23, 2013 indicated that 59 storm events occurred. Water quality data was obtained from 22 storm events. Not all the sampled storms produced information that met TAPE criteria for storm and/or water quality data. 2. The system treated 98.9 % of the total 8-month runoff volume during the testing period. Consequently, the system achieved the goal of treating 91 % of the volume from the site. Stormwater runoff bypassed Filterra treatment during four of the 59 storm events. 3. Of the 22 sampled events, 18 qualified for TSS analysis (influent TSS concentrations ranged from 25 to 138 mg/L). The data were segregated into sample pairs with influent concentration greater than and less than 100 mg/L. The UCL95 mean effluent concentration for the data with influent less than 100 mg/L was 5.2 mg/L, below the 20- mg/L threshold. Although the TAPE guidelines do not require an evaluation of TSS removal efficiency for influent concentrations below 100 mg/L, the mean TSS removal for these samples was 90.1 %. Average removal of influent TSS concentrations greater than 100 mg/L (three events) was 85 %. In addition, the system consistently exhibited TSS removal greater than 80 % at flow rates equivalent to a 100 in/hr infiltration rate and was observed at 150 in/hr. 4. Ten of the 22 sampled events qualified for TP analysis. Americast augmented the dataset using two sample pairs from previous monitoring at the site. Influent TP concentrations ranged from 0.11 to 0.52 mg/L. The mean TP removal for these twelve events was 72.6 %. The LCL95 mean percent removal was 66.0, well above the TAPE requirement of 50 %. Treatment above 50 % was evident at 100 in/hr infiltration rate and as high as 150 in/hr. Consequently, the Filterra test system met the TAPE Phosphorus Treatment goal at 100 in/hr. Influent ortho-P concentrations ranged from 0.005 to 0.012 mg/L; effluent ortho-P concentrations ranged from 0.005 to 0.013 mg/L. The reporting limit/resolution for the ortho-P test method is 0.01 mg/L, therefore the influent and effluent ortho-P concentrations were both at and near non-detect concentrations. 7 Field Testing 2008-2009 1. Filterra completed field-testing at two sites at the Port of Tacoma. Continuous flow and rainfall data collected during the 2008-2009 monitoring period indicated that 89 storm events occurred. The monitoring obtained water quality data from 27 storm events. Not all the sampled storms produced information that met TAPE criteria for storm and/or water quality data. 2. During the testing at the Port of Tacoma, 98.96 to 99.89 % of the annual influent runoff volume passed through the POT1 and POT2 test systems respectively. Stormwater runoff bypassed the POT1 test system during nine storm events and bypassed the POT2 test system during one storm event. Bypass volumes ranged from 0.13 % to 15.3% of the influent storm volume. Both test systems achieved the 91 % water quality treatment-goal over the 1-year monitoring period. 3. Consultants observed infiltration rates as high as 133 in/hr during the various storms. Filterra did not provide any paired data that identified percent removal of TSS, metals, oil, or phosphorus at an instantaneous observed flow rate. 4. The maximum storm average hydraulic loading rate associated with water quality data is <40 in/hr, with the majority of flow rates < 25 in/hr. The average instantaneous hydraulic loading rate ranged from 8.6 to 53 in/hr. 5. The field data showed a removal rate greater than 80 % for TSS with an influent concentration greater than 20 mg/L at an average instantaneous hydraulic loading rate up to 53 in/hr (average influent concentration of 28.8 mg/L, average effluent concentration of 4.3 mg/L). 6. The field data showed a removal rate generally greater than 54 % for dissolved zinc at an average instantaneous hydraulic loading rate up to 60 in/hr and an average influent concentration of 0.266 mg/L (average effluent concentration of 0.115 mg/L). 7. The field data showed a removal rate generally greater than 40 % for dissolved copper at an average instantaneous hydraulic loading rate up to 35 in/hr and an average influent concentration of 0.0070 mg/L (average effluent concentration of 0.0036 mg/L). 8. The field data showed an average removal rate of 93 % for total petroleum hydrocarbon (TPH) at an average instantaneous hydraulic loading rate up to 53 in/hr and an average influent concentration of 52 mg/L (average effluent concentration of 2.3 mg/L). The data also shows achievement of less than 15 mg/L TPH for grab samples. Filterra provided limited visible sheen data due to access limitations at the outlet monitoring location. 9. The field data showed low percentage removals of total phosphorus at all storm flows at an average influent concentration of 0.189 mg/L (average effluent concentration of 0.171 mg/L). We may relate the relatively poor treatment performance of the Filterra system at this location to influent characteristics for total phosphorus that are unique to the Port of Tacoma site. It appears that the Filterra system will not meet the 50 % removal performance goal when the majority of phosphorus in the runoff is expected to be in the dissolved form. 8 Laboratory Testing 1. Filterra performed laboratory testing on a scaled down version of the Filterra unit. The lab data showed an average removal from 83-91 % for TSS with influents ranging from 21 to 320 mg/L, 82-84 % for total copper with influents ranging from 0.94 to 2.3 mg/L, and 50-61 % for orthophosphate with influents ranging from 2.46 to 14.37 mg/L. 2. Filterra conducted permeability tests on the soil media. 3. Lab scale testing using Sil-Co-Sil 106 showed removals ranging from 70.1 % to 95.5 % with a median removal of 90.7 %, for influent concentrations ranging from 8.3 to 260 mg/L. Filterra ran these laboratory tests at an infiltration rate of 50 in/hr. 4. Supplemental lab testing conducted in September 2009 using Sil-Co-Sil 106 showed an average removal of 90.6 %. These laboratory tests were run at infiltration rates ranging from 25 to 150 in/hr for influent concentrations ranging from 41.6 to 252.5 mg/L. Regression analysis results indicate that the Filterra system’s TSS removal performance is independent of influent concentration in the concentration rage evaluated at hydraulic loading rates of up to 150 in/hr. Contact Information: Applicant: Jeremiah Lehman Contech Engineered Solutions, LLC. 11815 Glenn Widing Dr Portland, OR 97220 (503) 258-3136 jlehman@conteches.com Applicant’s Website: http://www.conteches.com Ecology web link: http://www.ecy.wa.gov/programs/wq/stormwater/newtech/index.html Ecology: Douglas C. Howie, P.E. Department of Ecology Water Quality Program (360) 407-6444 douglas.howie@ecy.wa.gov Date Revision December 2009 GULD for Basic, Enhanced, and Oil granted, CULD for Phosphorus September 2011 Extended CULD for Phosphorus Treatment September 2012 Revised design storm discussion, added Shallow System. January 2013 Revised format to match Ecology standards, changed Filterra contact information February 2013 Added FTIB-P system March 2013 Added FTIB-C system April 2013 Modified requirements for identifying appropriate size of unit 9 June 2013 Modified description of FTIB-C alternate configuration March 2014 GULD awarded for Phosphorus Treatment. GULD updated for a higher flow-rate for Basic Treatment. June 2014 Revised sizing calculation methods March 2015 Revised Contact Information June 2015 CULD for Basic and Enhanced at 100 in/hr infiltration rate September 2019 GULD for Basic and Enhanced at 175 in/hr infiltration rate February 2020 Revised sizing language to note sizing based on off-line calculations June 2020 Added Phosphorus to Filterra Shallow sizing table Lindbergh HS Conveyance Analysis Spreadsheet Pipe Run Tributary Basins Size Mannings N Plan Slope Qfull Total Tributary Area Tributary Impervious Tributary Grass Qtrib, 25-year(MGS Flood, 5 min)% Full(25-year)Qtrib, 100-year(MGS Flood, 5 min)% Full(25-year)(inches)(ft/ft)(cfs)(ac)(ac)(ac)(cfs)(cfs) 1 Proposed Classroom Additions and Existing Conditions Tributary to POC 12 0.011 0.007 3.53 2.118 1.462 0.656 2.04 58%3.48 98% 2 South Basin - Proposed Parking Lot and Existing Conditions Tributary to POC 12 0.011 0.01 4.22 1.759 1.394 0.365 1.90 45%3.13 74% ————————————————————————————————— MGS FLOOD PROJECT REPORT – Pipe Run #1 North Conveyance Analysis Program Version: MGSFlood 4.57 Program License Number: 201410003 Project Simulation Performed on: 04/14/2022 12:33 PM Report Generation Date: 04/14/2022 4:16 PM ————————————————————————————————— Input File Name: North.fld Project Name: Lindbergh HS Analysis Title: North Conveyance Comments: ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 5 Extended Precipitation Time Series Selected Climatic Region Number: 16 Full Period of Record Available used for Routing Precipitation Station : 96004405 Puget East 44 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961044 Puget East 44 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : Ecology Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 2.118 2.118 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 2.118 2.118 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Predev ---------- -------Area (Acres) -------- C, Lawn, Mod 0.656 SIDEWALKS/MOD 1.462 ---------------------------------------------- Subbasin Total 2.118 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Postdev ---------- -------Area (Acres) -------- C, Lawn, Mod 0.656 SIDEWALKS/MOD 1.462 ---------------------------------------------- Subbasin Total 2.118 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 0 **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 0 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Predev 84.462 _____________________________________ Total: 84.462 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Postdev 84.462 _____________________________________ Total: 84.462 Total Predevelopment Recharge Equals Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 0.535 ac-ft/year, Post Developed: 0.535 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Links: 0 ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Predev Scenario Postdeveloped Compliance Subbasin: Postdev *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 1.010 2-Year 1.010 5-Year 1.395 5-Year 1.395 10-Year 1.703 10-Year 1.703 25-Year 2.039 25-Year 2.039 50-Year 2.597 50-Year 2.597 100-Year 3.477 100-Year 3.477 200-Year 3.993 200-Year 3.993 500-Year 4.662 500-Year 4.662 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals ————————————————————————————————— MGS FLOOD PROJECT REPORT – Pipe Run #2 South Conveyance Analysis Program Version: MGSFlood 4.57 Program License Number: 201410003 Project Simulation Performed on: 04/14/2022 12:43 PM Report Generation Date: 04/14/2022 12:44 PM ————————————————————————————————— Input File Name: South.fld Project Name: Lindbergh HS Analysis Title: South Conveyance Comments: ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 5 Extended Precipitation Time Series Selected Climatic Region Number: 16 Full Period of Record Available used for Routing Precipitation Station : 96004405 Puget East 44 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961044 Puget East 44 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : Ecology Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 1.759 1.759 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 1.759 1.759 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Predev ---------- -------Area (Acres) -------- C, Lawn, Mod 0.365 SIDEWALKS/MOD 1.394 ---------------------------------------------- Subbasin Total 1.759 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Postdev ---------- -------Area (Acres) -------- C, Lawn, Mod 0.365 SIDEWALKS/MOD 1.394 ---------------------------------------------- Subbasin Total 1.759 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 0 **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 0 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Predev 46.995 _____________________________________ Total: 46.995 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Postdev 46.995 _____________________________________ Total: 46.995 Total Predevelopment Recharge Equals Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 0.297 ac-ft/year, Post Developed: 0.297 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Links: 0 ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Predev Scenario Postdeveloped Compliance Subbasin: Postdev *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 0.922 2-Year 0.922 5-Year 1.268 5-Year 1.268 10-Year 1.571 10-Year 1.571 25-Year 1.897 25-Year 1.897 50-Year 2.313 50-Year 2.313 100-Year 3.130 100-Year 3.130 200-Year 3.589 200-Year 3.589 500-Year 4.186 500-Year 4.186 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals Sediment Facility Sizing Calculations - North Basin Per the City of Renton Surface Water Design Manual 2017 Section D.2.1.5.1 Project Name:Lindbergh High School - North Required Sediment Facility Surface Area (SA): SA =2*Q/Vsed Where:Q =10-year developed flow rate from MGS Flood Vsed =Settling Velocity (0.00096 ft/sec) Calculation:multiplier =2 Q =0.4220 cfs Vsed =0.00096 fps Required SA =879.2 square feet Equivalent Sediment Trap Volume: Length of Top Surface Area =30 feet Width of Top Surface Area =30 feet Surface Area Provided =900 square feet Side Slope =3 (H:1V) Total Depth of Sediment Trap =3.5 feet Bottom Length of Sediment Trap =9 feet Bottom Width of Sediment Trap =9 feet Total pond Volume =1716.75 cubic feet 12841.29 gallons To determine the minimum sediment trap volume, an equivalent sediment trap was sized based upon the required surface area. Sediment Facility Sizing Calculations - South Basin Per the City of Renton Surface Water Design Manual 2017 Section D.2.1.5.1 Project Name:Lindbergh High School - South Required Sediment Facility Surface Area (SA): SA =2*Q/Vsed Where:Q =10-year developed flow rate from MGS Flood Vsed =Settling Velocity (0.00096 ft/sec) Calculation:multiplier =2 Q =0.7150 cfs Vsed =0.00096 fps Required SA =1489.6 square feet Equivalent Sediment Trap Volume: Length of Top Surface Area =39 feet Width of Top Surface Area =39 feet Surface Area Provided =1521 square feet Side Slope =3 (H:1V) Total Depth of Sediment Trap =3.5 feet Bottom Length of Sediment Trap =18 feet Bottom Width of Sediment Trap =18 feet Total pond Volume =3228.75 cubic feet 24151.05 gallons To determine the minimum sediment trap volume, an equivalent sediment trap was sized based upon the required surface area. ————————————————————————————————— MGS FLOOD PROJECT REPORT –North TESC Program Version: MGSFlood 4.57 Program License Number: 201410003 Project Simulation Performed on: 04/14/2022 4:30 PM Report Generation Date: 04/14/2022 4:30 PM ————————————————————————————————— Input File Name: North TESC.fld Project Name: Lindbergh HS Analysis Title: North TESC Comments: ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Climatic Region Number: 16 Full Period of Record Available used for Routing Precipitation Station : 96004405 Puget East 44 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961044 Puget East 44 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : Ecology Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 1.725 1.725 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 1.725 1.725 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Predev ---------- -------Area (Acres) -------- C, Lawn, Mod 0.947 SIDEWALKS/FLAT 0.778 ---------------------------------------------- Subbasin Total 1.725 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Postdev ---------- -------Area (Acres) -------- C, Lawn, Mod 0.947 SIDEWALKS/FLAT 0.778 ---------------------------------------------- Subbasin Total 1.725 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 0 **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 0 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Predev 121.968 _____________________________________ Total: 121.968 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Postdev 121.968 _____________________________________ Total: 121.968 Total Predevelopment Recharge Equals Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 0.772 ac-ft/year, Post Developed: 0.772 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Links: 0 ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Predev Scenario Postdeveloped Compliance Subbasin: Postdev *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 0.422 2-Year 0.422 5-Year 0.569 5-Year 0.569 10-Year 0.703 10-Year 0.703 25-Year 0.904 25-Year 0.904 50-Year 1.194 50-Year 1.194 100-Year 1.499 100-Year 1.499 200-Year 1.535 200-Year 1.535 500-Year 1.573 500-Year 1.573 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals ————————————————————————————————— MGS FLOOD PROJECT REPORT – South TESC Program Version: MGSFlood 4.57 Program License Number: 201410003 Project Simulation Performed on: 04/14/2022 4:26 PM Report Generation Date: 04/14/2022 4:26 PM ————————————————————————————————— Input File Name: South TESC.fld Project Name: Lindbergh HS Analysis Title: South TESC Comments: ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Climatic Region Number: 16 Full Period of Record Available used for Routing Precipitation Station : 96004405 Puget East 44 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961044 Puget East 44 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : Ecology Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 1.888 1.888 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 1.888 1.888 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Predev ---------- -------Area (Acres) -------- C, Lawn, Mod 0.479 SIDEWALKS/MOD 1.409 ---------------------------------------------- Subbasin Total 1.888 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Postdev ---------- -------Area (Acres) -------- C, Lawn, Mod 0.479 SIDEWALKS/MOD 1.409 ---------------------------------------------- Subbasin Total 1.888 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 0 **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 0 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Predev 61.693 _____________________________________ Total: 61.693 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Postdev 61.693 _____________________________________ Total: 61.693 Total Predevelopment Recharge Equals Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 0.390 ac-ft/year, Post Developed: 0.390 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Links: 0 ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Predev Scenario Postdeveloped Compliance Subbasin: Postdev *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 0.715 2-Year 0.715 5-Year 0.972 5-Year 0.972 10-Year 1.188 10-Year 1.188 25-Year 1.513 25-Year 1.513 50-Year 1.817 50-Year 1.817 100-Year 2.381 100-Year 2.381 200-Year 2.635 200-Year 2.635 500-Year 2.958 500-Year 2.958 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals ————————————————————————————————— MGS FLOOD PROJECT REPORT – Water Quality Flow Program Version: MGSFlood 4.57 Program License Number: 201410003 Project Simulation Performed on: 05/11/2022 2:10 PM Report Generation Date: 05/11/2022 2:19 PM ————————————————————————————————— Input File Name: Water Quality Flow.fld Project Name: Lindbergh HS Analysis Title: Water Quality Comments: ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Climatic Region Number: 16 Full Period of Record Available used for Routing Precipitation Station : 96004405 Puget East 44 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961044 Puget East 44 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : Ecology Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 0.239 0.239 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 0.239 0.239 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Predev ---------- -------Area (Acres) -------- SIDEWALKS/FLAT 0.239 ---------------------------------------------- Subbasin Total 0.239 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Postdev ---------- -------Area (Acres) -------- SIDEWALKS/FLAT 0.239 ---------------------------------------------- Subbasin Total 0.239 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 1 ------------------------------------------ Link Name: New Copy Lnk1 Link Type: Copy Downstream Link: None **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 1 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Predev 0.000 _____________________________________ Total: 0.000 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: Postdev 0.000 Link: New Copy Lnk1 0.000 _____________________________________ Total: 0.000 Total Predevelopment Recharge Equals Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 0.000 ac-ft/year, Post Developed: 0.000 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Links: 1 ********** Link: New Copy Lnk1 ********** 2-Year Discharge Rate : 0.098 cfs 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 0.038 cfs Off-line Design Discharge Rate (91% Exceedance): 0.022 cfs ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Predev Scenario Postdeveloped Compliance Link: New Copy Lnk1 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 9.811E-02 2-Year 9.811E-02 5-Year 0.126 5-Year 0.126 10-Year 0.149 10-Year 0.149 25-Year 0.187 25-Year 0.187 50-Year 0.224 50-Year 0.224 100-Year 0.278 100-Year 0.278 200-Year 0.297 200-Year 0.297 500-Year 0.320 500-Year 0.320 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals APPENDIX C Construction Stormwater Pollution Prevention Plan (SWPPP) Narrative Page 1 Lindbergh HS – Modernization and Additions SWPPP Narrative LINDBERGH HS – MODERNIZATION AND ADDITIONS CONSTRUCTION SWPPP NARRATIVE OCTOBER 26, 2022 The following Preliminary Construction Storm Water Pollution Prevention Plan (SWPPP) Narrative for the Lindbergh High School modernization and addition project supplements the Temporary Erosion and Sediment Control drawings. This narrative and the drawings address the requirements of Section 3.3 of Volume II of the 2014 Washington State Department of Ecology (DOE) Stormwater Management Manual for Western Washington. The project will also require a NPDES permit application (Notice of Intent) for a Construction Stormwater General Permit through the DOE, which will be included with the final permit. 1. CONSTRUCTION STORMWATER POLLUTION PREVENTION ELEMENTS 1) Mark Clearing Limits: Clearing limits will be defined by erosion control components, construction fencing, and/or the existing fence, as shown on the TESC and Site Demolition plan. The actual limits of clearing will most likely be smaller than the limit of work area, but this identifies the maximum extent of the clearing limits. Existing paved area and areas to be cleared will be maintained in an undisturbed condition until required to be impacted. Areas impacted and not anticipated to be covered with final measures shall be stabilized using approved ESC methods. 2) Establish Construction Access: A temporary construction access (BMP C105) will be installed prior to construction. Construction access is provided off of 128th Ave SE via the existing driveways. The Contractor shall provide a wheel wash if necessary. 3) Control Flow Rates: Stormwater flow control during construction is anticipated to be mitigated by routing runoff to temporary sediment storage tanks. Refer to the Sediment Tank Sizing calculations and the MGS Flood output included within Appendix B of the project’s Stormwater Technical Information Report. 4) Install Sediment Controls: DOE approved BMPs for sediment controls are shown on the TESC plan. Sediment will be controlled using storm drain inlet protection (BMP C220), and the proposed sediment settling tanks. Refer to TESC plans for approximate locations and required volumes. It is the Contractor’s responsibility to upgrade erosion control as necessary to meet applicable requirements. In order to complete the turbidity monitoring required by the project’s DOE Stormwater General Permit, and in the event that unexpected conditions arise during construction, the Contractor is expected to contract with a third-party erosion control monitor to help manage the site and prevent any discharges of turbid water to the downstream system. If turbidity monitoring indicates that the discharged stormwater does not meet the acceptable discharge requirements, the Contractor shall immediately plug the point of discharge and provide additional TESC measures as necessary. The Contractor’s Certified Erosion and Sediment Control Lead (CESCL) will be responsible for coordinating with the third-party monitoring company regarding the required sampling of stormwater discharges from the site as required by the DOE stormwater permit. The Contractor’s CESCL will be required to coordinate the required sampling of stormwater discharges from the site at the upstream and downstream turbidity monitoring locations, in accordance with the requirements of the NPDES permit. Since the project Page 2 Lindbergh HS – Modernization and Additions SWPPP Narrative site is over 1 acre, turbidity monitoring must be conducted weekly and within 24 hours of a discharge. Water quality testing results will be kept on site for reference and review if requested by the Renton School District, City of Renton, or other agencies. Monthly summary reports (Discharge Monitoring Reports) are required to be submitted to the DOE via the web DMR application. The Contractor will be the permit holder once the Owner completes the Stormwater General Permit Transfer of Coverage at the beginning of construction. The CESCL is also required to perform weekly (at a minimum) inspections of TESC BMPs throughout the site. 5) Stabilize Soils: It is possible that some of the earthwork and grading may occur in wet weather conditions. The site must be stabilized and no soils will be allowed to remain un-stabilized for more than two days between October 1st and April 30th. From May 1 through September 30, install cover measures to protect disturbed areas that will remain unworked for seven days or more. By October 8, seed all areas that will remain unworked from October 1 through April 30. Mulch all seeded areas. Exposed slopes will be protected by DOE-approved coverage methods. BMPs including, but not limited to: C101, Preserving Natural Vegetation; C121, Mulching; C123, Plastic Covering; C130, Surface Roughening; C140, Dust Control; and T5.13 Post Construction Soil Amendment will be used to stabilize on-site soils during construction. 6) Protect Slopes: DOE-approved BMPs for slope protection will be utilized during construction. Concentrated discharges shall not be allowed to flow over the top of steep slopes. BMPs including, but not limited to C101, Preserving Natural Vegetation; C121, Mulching; C123, Plastic Covering; C130, Surface Roughening; C140, Dust Control; C200, Interceptor Dike and Swale; C207, Check Dams; and C233, Silt Fence are to be utilized to protect slopes during construction. 7) Protect Drain Inlets: Drainage structures in areas where no work occurs will remain and will be protected; discharge points to the public storm drain main line will also be protected. To prevent discharge of turbid water downstream, all existing catch basins located within the disturbance area and outside of the disturbance area within approximately 300 ft downstream of the site will be protected with storm drain inlet protection (BMP C220). Proposed inlets will also be protected with catch basin inserts, and where feasible, their outlets will be temporarily plugged until the site is stabilized. The Contractor shall remove inlet protection at the end of the project without releasing captured sediment into the storm system. 8) Stabilize Channels and Outlets: DOE-approved BMPs for channel stabilization will be utilized during construction, including, but not limited to C207, Check Dams. 9) Control Pollutants: Temporary protection of the disturbed soils provides the first level of protection for pollution control, and perimeter measures downstream will mitigate the remaining pollutants. The temporary protection of disturbed soils may be mitigated with a temporary sump and pump facility to provide the second level of interception of pollutants. This collection system filters sediments prior to the pump system. The pump system will then route stormwater into the temporary sediment settling tranks. All construction debris will be removed from the site. Contractor will be responsible for managing their construction equipment per DOE-approved BMPs. The stabilized construction entrance is assumed to be sufficient for the construction period. If something more substantial is required, the Contractor is to coordinate with the Owner’s Representative and the King County inspector. If a truck wheel wash is required, truck Page 3 Lindbergh HS – Modernization and Additions SWPPP Narrative wheel wash water and concrete truck washout water shall be collected and discharged to the public sanitary sewer (SS) system. To apply for SS release, contact the local sewer purveyor for authorization. 10) Control De-Watering: The majority of the earthwork on the project will be constructed during the dry season, therefore it is not anticipated that groundwater will be encountered in the excavations for this project. In the event that perched groundwater is encountered during any wet season construction, the Contractor shall route it to the sediment settling trap by pumping it out of the excavation. 11) Maintain BMPs: DOE-approved standard BMP maintenance will be required in accordance with the Erosion and Sedimentation Control Plan and Notes. 12) Manage the Project: All phases of construction will be managed by the Contractor. The site must be stabilized and no soils will be allowed to remain exposed and unworked for more than two days between October 1st and April 30th and for more than seven days between May 1st and September 30th. The Contractor will provide maintenance and monitoring of TESC BMPs. Work of all contractors will be coordinated to minimize the duration of disturbance on the site. The best management practices shown on the TESC plan are minimum requirements. Failure to maintain SWPPP measures in accordance with adopted standards may result in the work being performed at the County’s direction and the costs assessed as a lien against the property where such facilities are located. 13) Protect Low Impact Development BMPs: The project does not propose the use of any Low Impact Development BMPs. 2. PROJECT DESCRIPTION Improvements include the proposed building additions on the east and west sides of the main school building with new walkways, and replacement of the asphalt parking lot in the southeast corner of the site. There are also sidewalk and curb ramp improvements in the frontage along 128th Ave SE. 3. EXISTING SITE CONDITIONS The property currently contains the main school building, a pool building, portables, several playfields, and associated parking lots. Topographically, the specific renovation site area is relatively flat, but generally slopes down from the east to the west from a high elevation of approximately 430-feet. Elevations descend to a low point approximately 400-feet at the surface parking area adjacent to the west of the major portions of the school facility. There are two distinct drainage systems onsite which divide the site into two threshold discharge areas (TDA). The North TDA system collects flow from some of the building roof, the northern parking lot and driveway, and the softball and baseball fields. This system leaves the site at the northwest corner of the property and discharges to the public storm main in 128th Avenue SE. The South TDA system collects flow from some of the building roof, the southwest parking lot and driveway, the tennis courts, and the track and field. This system leaves the site at the Page 4 Lindbergh HS – Modernization and Additions SWPPP Narrative southeast corner of the property to an adjacent private system before outfalling to Molasses Creek. 4. ADJACENT AREAS The property is bounded by residential properties to the north and east, Renton Park and Renton Park Chapel to the south, and 128th Avenue SE to the west. The site is located in Section 28, Township 23 North, Range 5 East, Willamette Meridian. 5. CRITICAL AREAS Renton GIS mapping shows regulated slopes designated throughout the school site including within the proposed building renovation areas. However, according to the Geotechnical Report no slopes greater than 40% were observed within or near the project areas. The southwestern corner of the school property is located within a seismic hazard area. However, the project site is outside of this area. There are no other critical areas on or adjacent to the project site. 6. SOILS A geotechnical report was prepared for the site by Associated Earth Sciences, Inc (AESI), dated February 7, 2022. AESI also prepared a subsequent limited geotechnical engineering study for the parking lot, dated January 3, 2022. Borings encountered a layer of fill ranging from 4 to 9 feet below ground surface. Dense to very dense Vashon Lodgement Till was encountered below the fill layer and extended to the maximum depth explored, 35 feet below ground surface. Neither of these soil layers is a suitable infiltration receptor. Perched groundwater seepage was observed is several borings at depths from 1 to 7 feet below ground surface, and directly below the asphalt in one of the parking lot borings. 7. POTENTIAL EROSION PROBLEM AREAS The erosion hazard of the site soils is expected to be low. Per the proposed contract documents, the contractor is to provide protection for soils to limit the exposure to erosion. The limitation of disturbance, adequate cover practices, and runoff control are the most effective methods for reduction of turbidity in stormwater runoff. Any runoff that does occur will be directed to the sediment tanks. Areas that have not been permanently stabilized will be addressed using DOE-approved BMPs, per the construction documents. 8. CONSTRUCTION PHASING Project phases is not anticipated for this project. 9. CONSTRUCTION SCHEDULE Construction is expected to begin in June 2022 and be complete by September 2023. 10. FINANCIAL/OWNERSHIP RESPONSIBILITIES The property is owned and operated by the Renton School District. The accepted low bidder on the project will be responsible for posting a performance and payment bond with the Renton Page 5 Lindbergh HS – Modernization and Additions SWPPP Narrative School District, thus will be the responsible party for any liability associated with erosion and sedimentation impact. 11. ENGINEERING CALCULATIONS A copy of any calculations performed during design of the project and relevant storm drainage modeling discussions is included in the project’s Stormwater Technical Information Report. 12. CERTIFIED EROSION CONTROL SPECIALIST The contractor will name their Certified Erosion Control Specialist and provide contact information at the pre-construction meeting. APPENDIX D Operations and Maintenance Manual Filterra Owner’s Manual ® Bioretention Systems ENGINEERED SOLUTIONS This Owner’s Manual applies to all precast Filterra Configurations, including Filterra Bioscape Vault. www.ContechES.com/filterra | 800-338-1122 3 Table of Contents Introduction ................................................................................4 Activation Overview .....................................................................4 Filterra Plant Selection Overview ...................................................6 Warranty Overview ......................................................................6 Routine Maintenance Guidelines...................................................6 Maintenance Visit Procedure .........................................................9 Appendix 1 – Activation Checklist ...............................................12 Appendix 2 – Planting Requirements for Filterra Systems ................13 Appendix 3 – Filterra Tree Grate Opening Expansion Procedure ....15 ® Bioretention Systems ENGINEERED SOLUTIONS www.ContechES.com/filterra | 800-338-11224 Introduction Thank you for your purchase of the Filterra® Bioretention System. Filterra is a specially engineered stormwater treatment system incorporating high performance biofiltration media to remove pollutants from stormwater runoff. The system’s biota (vegetation and soil microorganisms) then further breakdown and absorb captured pollutants. All components of the system work together to provide a sustainable long-term solution for treating stormwater runoff. The Filterra system has been delivered to you with protection in place to resist intrusion of construction related sediment which can contaminate the biofiltration media and result in inadequate system performance. These protection devices are intended as a best practice and cannot fully prevent contamination. It is the purchaser’s responsibility to provide adequate measures to prevent construction related runoff from entering the Filterra system. Included with your purchase is Activation of the Filterra system by the manufacturer as well as a 1-year warranty from delivery of the system and 1-year of routine maintenance (mulch replacement, debris removal, and pruning of vegetation) up to twice during the first year after activation. Design and Installation Each project presents different scopes for the use of Filterra systems. Information and help may be provided to the design engineer during the planning process. Correct Filterra box sizing (by rainfall region) is essential to predict pollutant removal rates for a given area. The engineer shall submit calculations for approval by the local jurisdiction. The contractor is responsible for the correct installation of Filterra units as shown in approved plans. A comprehensive installation manual is available at www.ContechES.com. Activation Overview Activation of the Filterra system is a procedure completed by the manufacturer to place the system into working condition. This involves the following items: • Removal of construction runoff protection devices • Planting of the system’s vegetation • Placement of pretreatment mulch layer using mulch certified for use in Filterra systems. Activation MUST be provided by the manufacturer to ensure proper site conditions are met for Activation, proper installation of the vegetation, and use of pretreatment mulch certified for use in Filterra systems. www.ContechES.com/filterra | 800-338-1122 5 Minimum Requirements The minimum requirements for Filterra Activation are as follows: 1. The site landscaping must be fully stabilized, i.e. full landscaping installed and some grass cover (not just straw and seed) is required to reduce sediment transport. Construction debris and materials should be removed from surrounding area. 2. Final paving must be completed. Final paving ensures that paving materials will not enter and contaminate the Filterra system during the paving process, and that the plant will receive runoff from the drainage area, assisting with plant survival for the Filterra system. 3. Where curb inlets are included as part of the Filterra system, Filterra throat opening should be at least 4” in order to ensure adequate capacity for inflow and debris. An Activation Checklist is included on page 12 to ensure proper conditions are met for Contech to perform the Activation services. A charge of $500.00 will be invoiced for each Activation visit requested by Customer where Contech determines that the site does not meet the conditions required for Activation. www.ContechES.com/filterra | 800-338-11226 Filterra Plant Selection Overview A Plant List is available on the Contech website highlighting recommended plants for Filterra systems in your area. Keep in mind that plants are subject to availability due to seasonality and required minimum size for the Filterra system. Plants installed in the Filterra system are container plants (max 15 gallon) from nursery stock and will be immature in height and spread at Activation. It is the responsibility of the owner to provide adequate irrigation when necessary to the plant of the Filterra system. The “Planting Requirements for Filterra Systems” document is included as an appendix and discusses proper selection and care of the plants within Filterra systems. Warranty Overview Refer to the Contech Engineered Solutions LLC Stormwater Treatment System LIMITED WARRANTY for further information. The following conditions may void the Filterra system’s warranty and waive the manufacturer provided Activation and Maintenance services: • Unauthorized activation or performance of any of the items listed in the activation overview • Any tampering, modifications or damage to the Filterra system or runoff protection devices • Removal of any Filterra system components • Failure to prevent construction related runoff from entering the Filterra system • Failure to properly store and protect any Filterra components (including media and underdrain stone) that may be shipped separately from the vault Routine Maintenance Guidelines With proper routine maintenance, the biofiltration media within the Filterra system should last as long as traditional bioretention media. Routine maintenance is included by the manufacturer on all Filterra systems for the first year after activation. This includes a maximum of 2 visits to remove debris, replace pretreatment mulch, and prune the vegetation. More information is provided in the Operations and Maintenance Guidelines. Some Filterra systems also contain pretreatment or outlet bays. Depending on site pollutant loading, these bays may require periodic removal of debris, however this is not included in the first year of maintenance, and would likely not be required within the first year of operation. These services, as well as routine maintenance outside of the included first year, can be provided by certified maintenance providers listed on the Contech website. Training can also be provided to other stormwater maintenance or landscape providers. www.ContechES.com/filterra | 800-338-1122 7 Why Maintain? All stormwater treatment systems require maintenance for effective operation. This necessity is often incorporated in your property’s permitting process as a legally binding BMP maintenance agreement. Other reasons to maintain are: • Avoiding legal challenges from your jurisdiction’s maintenance enforcement program. • Prolonging the expected lifespan of your Filterra media. • Avoiding more costly media replacement. • Helping reduce pollutant loads leaving your property. Simple maintenance of the Filterra is required to continue effective pollutant removal from stormwater runoff before discharge into downstream waters. This procedure will also extend the longevity of the living biofilter system. The unit will recycle and accumulate pollutants within the biomass, but is also subjected to other materials entering the inlet. This may include trash, silt and leaves etc. which will be contained above the mulch layer. Too much silt may inhibit the Filterra’s flow rate, which is the reason for site stabilization before activation. Regular replacement of the mulch stops accumulation of such sediment. When to Maintain? Contech includes a 1-year maintenance plan with each system purchase. Annual included maintenance consists of a maximum of two (2) scheduled visits. Additional maintenance may be necessary depending on sediment and trash loading (by Owner or at additional cost). The start of the maintenance plan begins when the system is activated. Maintenance visits are typically scheduled seasonally; the spring visit aims to clean up after winter loads including salts and sands while the fall visit helps the system by removing excessive leaf litter. It has been found that in regions which receive between 30-50 inches of annual rainfall, (2) two visits are generally required; regions with less rainfall often only require (1) one visit per annum. Varying land uses can affect maintenance frequency; e.g. some fast food restaurants require more frequent trash removal. Contributing drainage areas which are subject to new development wherein the recommended erosion and sediment control measures have not been implemented may require additional maintenance visits. Some sites may be subjected to extreme sediment or trash loads, requiring more frequent maintenance visits. This is the reason for detailed notes of maintenance actions per unit, helping the Supplier and Owner predict future maintenance frequencies, reflecting individual site conditions. Owners must promptly notify the maintenance provider of any damage to the plant(s), which constitute(s) an integral part of the bioretention technology. Owners should also advise other landscape or maintenance contractors to leave all maintenance to the Supplier (i.e. no pruning or fertilizing) during the first year. www.ContechES.com/filterra | 800-338-11228 Exclusion of Services Clean up due to major contamination such as oils, chemicals, toxic spills, etc. will result in additional costs and are not covered under the Supplier maintenance contract. Should a major contamination event occur the Owner must block off the outlet pipe of the Filterra (where the cleaned runoff drains to, such as drop inlet) and block off the throat of the Filterra. The Supplier should be informed immediately. Maintenance Visit Summary Each maintenance visit consists of the following simple tasks (detailed instructions below). 1. Inspection of Filterra and surrounding area 2. Removal of tree grate (where applicable) and erosion control stones 3. Removal of debris, trash and mulch 4. Mulch replacement 5. Plant health evaluation and pruning or replacement as necessary 6. Clean area around Filterra 7. Complete paperwork Maintenance Tools, Safety Equipment and Supplies Ideal tools include: camera, bucket, shovel, broom, pruners, hoe/rake, and tape measure. Appropriate Personal Protective Equipment (PPE) should be used in accordance with local or company procedures. This may include impervious gloves where the type of trash is unknown, high visibility clothing and barricades when working in close proximity to traffic and also safety hats and shoes. A T-Bar or crowbar should be used for moving the tree grates, where applicable (up to 170 lbs each). If tree grate opening expansion is necessary, safety glasses/goggles and a 3lb or greater mini sledgehammer are required. Most visits require minor trash removal and a full replacement of mulch. See below for actual number of bagged mulch that is required in each media bay size. Mulch should be a double shredded, hardwood variety. Some visits may require additional Filterra engineered soil media available from the Supplier. Media Bay Length Media Bay Width Filter Surface Area (ft²)Volume at 3” (ft³)# of 2 ft³ Mulch Bags 4 4 16 4 2 6 4 24 6 3 8 4 32 8 4 6 6 36 9 5 8 6 48 12 6 10 6 60 15 8 12 6 72 18 9 13 7 91 23 12 Other sizes not listed - 1 bag per 8 ft² of media. www.ContechES.com/filterra | 800-338-1122 9 1. Inspection of Filterra and surrounding area • Record individual unit before maintenance with photograph (numbered). Record on Maintenance Report (see example in this document) the following: 2. Removal of tree grate (if applicable) and erosion control stones • Remove cast iron grates for access into Filterra box (if applicable). • Dig out silt (if any) and mulch and remove trash & foreign items. 3. Removal of debris, trash and mulch • After removal of mulch and debris, measure distance from the top of the Filterra engineered media soil to the top of the top slab. Compare the measured distance to the distance shown on the approved Contract Drawings for the system. Add Filterra media (not top soil or other) to bring media up as needed to distance indicated on drawings. Record on Maintenance Report the following: Standing Water yes | no Damage to Box Structure yes | no Damage to Grate (if applicable) yes | no Is Bypass Clear yes | no If yes answered to any of these observations, record with close-up photograph (numbered). Record on Maintenance Report the following: Silt/Clay yes | no Cups/ Bags yes | no Leaves yes | no Buckets Removed ________ Record on Maintenance Report the following: Distance to Top of Top Slab (inches) ________ Inches of Media Added ________ Maintenance Visit Procedure Keep sufficient documentation of maintenance actions to predict location specific maintenance frequencies and needs. An example Maintenance Report is included in this manual. www.ContechES.com/filterra | 800-338-112210 4. Mulch replacement • Add double shredded mulch evenly across the entire unit to a depth of 3”. • Refer to Filterra Mulch Specifications for information on acceptable sources. • Ensure correct repositioning of erosion control stones by the Filterra inlet to allow for entry of trash during a storm event. • Replace Filterra grates (if applicable) correctly using appropriate lifting or moving tools, taking care not to damage the plant. • Where applicable, if 6” tree grate opening is too close to plant trunk, the grate opening may be expanded to 12” using a mini sledgehammer. Refer to instructions in Appendix 3. 5. Plant health evaluation and pruning or replacement as necessary • Examine the plant’s health and replace if necessary. • Prune as necessary to encourage growth in the correct directions 6. Clean area around Filterra • Clean area around unit and remove all refuse to be disposed of appropriately. 7. Complete paperwork • Deliver Maintenance Report and photographs to appropriate location (normally Contech during maintenance contract period). • Some jurisdictions may require submission of maintenance reports in accordance with approvals. It is the responsibility of the Owner to comply with local regulations. Record on Maintenance Report the following: Height above top of Filterra Unit __________________(ft) Width at Widest Point __________________(ft) Health healthy | unhealthy Damage to Plant yes | no Plant Replaced yes | no www.ContechES.com/filterra | 800-338-1122 11 Maintenance Checklist Filterra Inspection & Maintenance Log Filterra System Size/Model: _____________________________Location: ____________________________________________ Drainage System Failure Problem Conditions to Check Condition that Should Exist Actions Inlet Excessive sediment or trash accumulation. Accumulated sediments or trash impair free flow of water into Filterra. Inlet should be free of obstructions allowing free distributed flow of water into Filterra. Sediments and/or trash should be removed. Mulch Cover Trash and floatable debris accumulation.Excessive trash and/or debris accumulation.Minimal trash or other debris on mulch cover. Trash and debris should be removed and mulch cover raked level. Ensure bark nugget mulch is not used. Mulch Cover “Ponding” of water on mulch cover. “Ponding” in unit could be indicative of clogging due to excessive fine sediment accumulation or spill of petroleum oils. Stormwater should drain freely and evenly through mulch cover. Recommend contact manufacturer and replace mulch as a minimum. Vegetation Plants not growing or in poor condition. Soil/mulch too wet, evidence of spill. Incorrect plant selection. Pest infestation. Vandalism to plants. Plants should be healthy and pest free.Contact manufacturer for advice. Vegetation Plant growth excessive. Plants should be appropriate to the species and location of Filterra. Trim/prune plants in accordance with typical landscaping and safety needs. Structure Structure has visible cracks. Cracks wider than 1/2 inch or evidence of soil particles entering the structure through the cracks. Vault should be repaired. Maintenance is ideally to be performed twice annually. Date Mulch & Debris Removed Depth of Mulch Added Mulch Brand Height of Vegetation Above Top of Vault Vegetation Species Issues with System Comments 1/1/17 5 – 5 gal Buckets 3”Lowe’s Premium Brown Mulch 4’Galaxy Magnolia - Standing water in downstream structure - Removed blockage in downstream structure www.ContechES.com/filterra | 800-338-112212 Appendix 1 – Filterra® Activation Checklist Project Name: ________________________________________Company: ______________________________________________ Site Contact Name: _______________________________________Site Contact Phone/Email: ____________________________ Site Owner/End User Name: _________________________Site Owner/End User Phone/Email: ____________________________ Preferred Activation Date: ___________________________________(provide 2 weeks minimum from date this form is submitted) Site Designation System Size Final Pavement / Top Coat Complete Landscaping Complete / Grass Emerging Construction materials / Piles / Debris Removed Throat Opening Measures 4” Min. Height Plant Species Requested  Yes  No  Yes  No  Yes  No  Yes  No  N/A  Yes  No  Yes  No  Yes  No  Yes  No  N/A  Yes  No  Yes  No  Yes  No  Yes  No  N/A  Yes  No  Yes  No  Yes  No  Yes  No  N/A  Yes  No  Yes  No  Yes  No  Yes  No  N/A  Yes  No  Yes  No  Yes  No  Yes  No  N/A  Yes  No  Yes  No  Yes  No  Yes  No  N/A  Yes  No  Yes  No  Yes  No  Yes  No  N/A  Yes  No  Yes  No  Yes  No  Yes  No  N/A NOTE: A charge of $500.00 will be invoiced for each Activation visit requested by Customer where Contech determines that the site does not meet the conditions required for Activation. ONLY Contech authorized representatives can perform Activation of Filterra systems; unauthorized Activations will void the system warranty and waive manufacturer supplied Activation and 1st Year Maintenance. Attach additional sheets as necessary. Signature Date ENGINEERED SOLUTIONS www.ContechES.com/filterra | 800-338-1122 13 Appendix 2 – Planting Requirements for Filterra® Systems Plant Material Selection • Select plant(s) as specified in the engineering plans and specifications. • Select plant(s) with full root development but not to the point where root bound. • Use local nursery container plants only. Ball and burlapped plants are not permitted. • For precast Filterra systems with a tree grate, plant(s) must not have scaffold limbs at least 14 inches from the crown due to spacing between the top of the mulch and the tree grate. Lower branches can be pruned away provided there are sufficient scaffold branches for tree or shrub development. • For precast Filterra systems with a tree grate, at the time of installation, it is required that plant(s) must be at least 6” above the tree grate opening at installation for all Filterra configurations. This DOES NOT apply to Full Grate Cover designs. • Plant(s) shall not have a mature height greater than 25 feet. • For standard 21” media depth, a 7 – 15 gallon container size shall be used. Media less than 21” (Filterra boxes only) may require smaller container plants. • For precast Filterra systems, plant(s) should have a single trunk at installation, and pruning may be necessary at activation and maintenance for some with a tree grate of the faster growing species, or species known to produce basal sprouts. Plant Installation • During transport protect the plant foliage from wind and excessive jostling. • Prior to removing the plant(s) from the container, ensure the soil moisture is sufficient to maintain the integrity of the root ball. If needed, pre-wet the container plant. • Cut away any roots which are growing out of the container drain holes. Plants with excessive root growth from the drain holes should be rejected. • Plant(s) should be carefully removed from the pot by gently pounding on the sides of the container with the fist to loosen root ball. Then carefully slide out. Do not lift plant(s) by trunk as this can break roots and cause soil to fall off. Extract the root ball in a horizontal position and support it to prevent it from breaking apart. Alternatively the pot can be cut away to minimize root ball disturbance. • Remove any excess soil from above the root flare after removing plant(s) from container. • Excavate a hole with a diameter 4” greater than the root ball, gently place the plant(s). • If plant(s) have any circling roots from being pot bound, gently tease them loose without breaking them. • If root ball has a root mat on the bottom, it should be shaved off with a knife just above the mat line. • Plant the tree/shrub/grass with the top of the root ball 1” above surrounding media to allow for settling. • All plants should have the main stem centered in the tree grate (where applicable) upon completion of installation. • With all trees/shrubs, remove dead, diseased, crossed/rubbing, sharply crotched branches or branches growing excessively long or in wrong direction compared to majority of branches. • To prevent transplant shock (especially if planting takes place in the hot season), it may be necessary to prune some of the foliage to compensate for reduced root uptake capacity. This is accomplished by pruning away some of the smaller secondary branches or a main scaffold branch if there are too many. Too much foliage relative to the root ball can dehydrate and damage the plant. • Plant staking may be required. www.ContechES.com/filterra | 800-338-112214 Mulch Installation • Only mulch that meets Contech Engineered Solutions’ mulch specifications can be used in the Filterra system. • Mulch must be applied to a depth of 3” evenly over the surface of the media. Irrigation Requirements • Each Filterra system must receive adequate irrigation to ensure survival of the living system during periods of drier weather. • Irrigation sources include rainfall runoff from downspouts and/or gutter flow, applied water through the top/tree grate or in some cases from an irrigation system with emitters installed during construction. • At Activation: Apply about one (cool climates) to two (warm climates) gallons of water per inch of trunk diameter over the root ball. • During Establishment: In common with all plants, each Filterra plant will require more frequent watering during the establishment period. One inch of applied water per week for the first three months is recommended for cooler climates (2 to 3 inches for warmer climates). If the system is receiving rainfall runoff from the drainage area, then irrigation may not be needed. Inspection of the soil moisture content can be evaluated by gently brushing aside the mulch layer and feeling the soil. Be sure to replace the mulch when the assessment is complete. Irrigate as needed**. • Established Plants: Established plants have fully developed root systems and can access the entire water column in the media. Therefore irrigation is less frequent but requires more applied water when performed. For a mature system assume 3.5 inches of available water within the media matrix. Irrigation demand can be estimated as 1” of irrigation demand per week. Therefore if dry periods exceed 3 weeks, irrigation may be required. It is also important to recognize that plants which are exposed to windy areas and reflected heat from paved surfaces may need more frequent irrigation. Long term care should develop a history which is more site specific. ** Five gallons per square yard approximates 1 inch of water Therefore for a 6’ by 6’ Filterra approximately 20-60 gallons of water is needed. To ensure even distribution of water it needs to be evenly sprinkled over the entire surface of the filter bed, with special attention to make sure the root ball is completely wetted. NOTE: if needed, measure the time it takes to fill a five gallon bucket to estimate the applied water flow rate then calculate the time needed to irrigate the Filterra. For example, if the flow rate of the sprinkler is 5 gallons/minute then it would take 12 minutes to irrigate a 6’ by 6’ filter. www.ContechES.com/filterra | 800-338-1122 15 Appendix 3 – Filterra® Tree Grate Opening Expansion Procedure The standard grates used on all Filterra configurations that employ Tree Grates are fabricated with a 6” opening that is designed with a breakaway section that can be removed, allowing the grate opening to be expanded to 12” as the tree matures and the trunk widens. The following tools are required to expand the opening: • Mini sledgehammer (3 lb. or greater) • Safety Glasses / Goggles The following guidelines should be followed to properly expand the tree opening from 6” to 12”: 1. Remove the grate from the Filterra frame, place it flat on a hard surface, and support the grate by stepping on the edge or using other weighted items such as a few mulch bags if this is being done during a Filterra maintenance event. Put on safety glasses/goggles. Align the mini sledgehammer as shown in the figure to the left. The head of the sledgehammer should be aimed just inside the wide cast iron bar between the larger grate section and the breakaway section. 2. Repeatedly hit the grate at this spot with the mini sledgehammer. 3. After several hits, the breakaway section should snap cleanly off of the larger grate section. Reinstall the grate into the Filterra grate frame. Recycle or dispose of the breakaway section per local guidelines. PDF 6/21 © 2021 Contech Engineered Solutions LLC, a QUIKRETE Company 9025 Centre Pointe Drive, Suite 400 West Chester, OH 45069 info@conteches.com | 800-338-1122 www.ContechES.com ALL RIGHTS RESERVED. PRINTED IN THE USA. NOTHING IN THIS CATALOG SHOULD BE CONSTRUED AS A WARRANTY. APPLICATIONS SUGGESTED HEREIN ARE DESCRIBED ONLY TO HELP READERS MAKE THEIR OWN EVALUATIONS AND DECISIONS, AND ARE NEITHER GUARANTEES NOR WARRANTIES OF SUITABILITY FOR ANY APPLICATION. CONTECH MAKES NO WARRANTY WHATSOEVER, EXPRESS OR IMPLIED, RELATED TO THE APPLICATIONS, MATERIALS, COATINGS, OR PRODUCTS DISCUSSED HEREIN. ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND ALL IMPLIED WARRANTIES OF FITNESS FOR ANY PARTICULAR PURPOSE ARE DISCLAIMED BY CONTECH. SEE CONTECH’S CONDITIONS OF SALE (AVAILABLE AT WWW.CONTECHES.COM/COS) FOR MORE INFORMATION. ® Bioretention Systems ENGINEERED SOLUTIONS 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 1/3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin. No trash or debris in the 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 is 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 1/4 inch wide at 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 Sedimentaccumulation 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. 2016 Surface Water Design Manual – Appendix A 4/24/2016A-9 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 7/8 inch. 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. 4/24/2016 2016 Surface Water Design Manual – Appendix AA-10 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 toslopes 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. 2016 Surface Water Design Manual – Appendix A 4/24/2016A-11 APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2017 City of Renton Surface Water Design Manual 12/12/2016 A-17 NO. 11 – GROUNDS (LANDSCAPING) 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 City personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where City 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. Excessive growth of grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches. Trees and Shrubs Hazard tree identified Any tree or limb of a tree identified as having a potential to fall and cause property damage or threaten human life. A hazard tree identified by a qualified arborist must be removed as soon as possible. No hazard trees in facility. Damaged tree or shrub identified Limbs or parts of trees or shrubs that are split or broken which affect more than 25% of the total foliage of the tree or shrub. Trees and shrubs with less than 5% of total foliage with split or broken limbs. Trees or shrubs that have been blown down or knocked over. No blown down vegetation or knocked over vegetation. Trees or shrubs free of injury. Trees or shrubs which are not adequately supported or are leaning over, causing exposure of the roots. Tree or shrub in place and adequately supported; dead or diseased trees removed. APPENDIX E Special Reports and Studies associated earth sciences incorporated Associated Earth Sciences, Inc. 911 5th Avenue Kirkland, WA 98033 P (425) 827 7701 Subsurface Exploration, Geologic Hazard, and Geotechnical Engineering Report LINDBERGH HIGH SCHOOL ADDITIONS Renton, Washington Prepared For: RENTON SCHOOL DISTRICT NO. 403 Project No. 20000669E005 February 7, 2022 Kirkland | Tacoma | Mount Vernon 425-827-7701 | www.aesgeo.com February 7, 2022 Project No. 20000669E005 Renton School District No. 403 7812 South 124th Street Seattle, Washington 98178 Attention: Mr. Stewart Shusterman Subject: Subsurface Exploration, Geologic Hazard, and Geotechnical Engineering Report Lindbergh High School Additions 16426 128th Avenue SE Renton, Washington Dear Mr. Shusterman: We are pleased to present the enclosed copy of the referenced report. This report summarizes the results of tasks including subsurface exploration, geologic hazard analysis, and geotechnical engineering and offers recommendations for design of the project. This report is based on a 100% Design Development plan set dated January 12, 2022. This report should be reviewed and updated as needed if project plans change substantially. A separate stand-alone geotechnical report was prepared for improvements to the southwest parking lot. We have enjoyed working with you on this study and are confident that the recommendations presented in this report will aid in the successful completion of your project. Please contact me if you have any questions or if we can be of additional help to you. Sincerely, ASSOCIATED EARTH SCIENCES, INC. Kirkland, Washington ______________________________ Bruce W. Guenzler, L.E.G. Senior Associate Geologist BWG/ld - 20000669E005-006 SUBSURFACE EXPLORATION, GEOLOGIC HAZARD, AND GEOTECHNICAL ENGINEERING REPORT LINDBERGH HIGH SCHOOL ADDITIONS Renton, Washington Prepared for: Renton School District No. 403 7812 South 124th Street Seattle, Washington 98178 Prepared by: Associated Earth Sciences, Inc. 911 5th Avenue Kirkland, Washington 98033 425-827-7701 February 7, 2022 Project No. 20000669E005 Subsurface Exploration, Geologic Hazard, Lindbergh High School Additions and Geotechnical Engineering Report Renton, Washington Project and Site Conditions February 7, 2022 ASSOCIATED EARTH SCIENCES, INC. ART/ld - 20000669E005-006 Page 1 I.PROJECT AND SITE CONDITIONS 1.0 INTRODUCTION This report presents the results of Associated Earth Sciences, Inc.’s (AESI’s) subsurface exploration, geologic hazard analysis, and geotechnical engineering study for the proposed building additions to Lindbergh High School in Renton, Washington. Our recommendations are based on a 100% Design Development plan set dated January 12, 2022. The site location is shown on the “Vicinity Map,” Figure 1. The approximate locations of explorations completed for this study are shown on the “Existing Site and Exploration Plan,” Figure 2. Interpretive exploration logs of subsurface explorations completed for this study are included in Appendix A. AESI prepared a separate geotechnical report in support of renovation of the southwest parking lot dated January 3, 2022. 1.1 Purpose and Scope The purpose of this study is to provide subsurface soil and groundwater data to be utilized in the design of the Lindbergh High School additions project. Our study included reviewing selected available geologic literature, advancing three exploration borings (EB-1 through EB-3), advancing two hand-auger borings (HB-1 and HB-2), reviewing three previous AESI geotechnical engineering studies (2003, 2004, and 2010) done in support of earlier projects on campus, and performing a geologic study of subsurface sediment and groundwater conditions. Geotechnical engineering studies were completed to formulate our recommendations for site preparation, earthwork, the type of suitable foundations and floor slabs, allowable foundation soil bearing pressures, anticipated foundation settlements, erosion considerations, and drainage considerations. This report summarizes our current fieldwork and offers design recommendations based on current project plans dated January 12, 2022. Our recommendations should be reviewed and updated if needed if plans change substantially. 1.2 Authorization Authorization to proceed with this study was given to AESI by means of District Purchase Order 2012000181 dated August 18, 2021. Our study was accomplished in general accordance with our proposal, dated August 10, 2021. This report has been prepared for the exclusive use of Renton School District and its agents, for specific application to this project. Within the limitations of scope, schedule, and budget, our services have been performed in accordance with generally accepted geotechnical engineering and engineering geology practices in effect in this area at the time our report was prepared. No other warranty, express or implied, is made. Subsurface Exploration, Geologic Hazard, Lindbergh High School Additions and Geotechnical Engineering Report Renton, Washington Project and Site Conditions February 7, 2022 ASSOCIATED EARTH SCIENCES, INC. ART/ld - 20000669E005-006 Page 2 2.0 PROJECT AND SITE DESCRIPTION The project site is that of the existing Lindbergh High School. The proposed project areas are flat to gently sloping and were graded to the existing configuration during previous earthwork completed to construct the existing campus. Topography of the project vicinity is characterized by an upland plateau with gentle to moderate slopes. A review of mapped critical areas on King County iMAP shows that an undeveloped area along the southeast edge of the project site is flagged as a potential seismic hazard area. No other geotechnical critical areas are flagged on or immediately adjacent to the site. It appears unlikely that building additions constructed near the newly completed explorations will need to address geotechnical critical areas requirements. The proposed project will include substantial building renovations, several building additions, and improvements to the existing southwest parking lot. 2.1 Historical Geotechnical Work AESI had previously provided geotechnical engineering for twelve projects onsite. Three of the previous studies included subsurface explorations near the currently proposed building improvement areas. Previous subsurface explorations onsite by AESI generally encountered surficial loose existing fill typically up to about 9 feet thick, underlain by very dense lodgement till. In general, loose existing fill is not suitable for structural support, and dense lodgement till is suitable for structural support with proper preparation. With respect to stormwater infiltration potential, existing fill is not permitted to serve as an infiltration receptor, and lodgement till is not a suitable infiltration receptor due to low permeability. This report relies, in part, on selected subsurface data from previous AESI geotechnical engineering studies onsite. Where we used existing data exploration locations are shown on the “Existing Site and Exploration Plan, Figure 2,” and copies of exploration logs are included in Appendix A. Subsurface data from previous AESI studies onsite included many additional explorations outside of the current work areas, and those more distant explorations are not shown on Figure 2 or included in Appendix A. AESI prepared a geotechnical engineering report dated January 3, 2022 for planned improvements to the existing southwest parking lot. 3.0 SITE EXPLORATION Our most recent field investigation for the current study was conducted in September 2021 and included advancing three exploration borings and two hand-auger borings. This study is supplemented with subsurface information gathered from our previous reports dated 2003, 2004, and 2010. The existing site conditions, and the approximate locations of subsurface explorations referenced in this study are presented on the “Existing Site and Exploration Plan” Subsurface Exploration, Geologic Hazard, Lindbergh High School Additions and Geotechnical Engineering Report Renton, Washington Project and Site Conditions February 7, 2022 ASSOCIATED EARTH SCIENCES, INC. ART/ld - 20000669E005-006 Page 3 (Figure 2). The various types of sediments, as well as the depths where the characteristics of the sediments changed, are indicated on the exploration logs presented in Appendix A. The depths indicated on the logs where conditions changed may represent gradational variations between sediment types. If changes occurred between sample intervals in our exploration borings, they were interpreted. Our explorations were approximately located in the field by measuring from known site features depicted on the aerial photograph used as a basis for Figure 2. The conclusions and recommendations presented in this report are based, in part, on the explorations completed for this study and previous on-site studies completed by AESI. The number, locations, and depths of the explorations were completed within site and budgetary constraints. Because of the nature of exploratory work below ground, extrapolation of subsurface conditions between field explorations is necessary. It should be noted that differing subsurface conditions may be present due to the random nature of deposition and the alteration of topography by past grading and/or filling. The nature and extent of variations between the field explorations may not become fully evident until construction. If variations are observed at that time, it may be necessary to re-evaluate specific recommendations in this report and make appropriate changes. 3.1 Exploration Borings For this study, the three exploration borings were completed by advancing a 3.25-inch, inside-diameter, hollow-stem auger using a track-mounted drill. During the drilling process, samples were generally obtained at 2½- to 5-foot-depth intervals. The borings were continuously observed and logged by a geologist from our firm. The exploration logs presented in Appendix A are based on the field logs, drilling action, and visual observation of the samples collected. Disturbed, but representative samples were obtained by using the Standard Penetration Test (SPT) procedure in accordance with ASTM International (ASTM) D-1586. This test and sampling method consists of driving a standard 2-inch, outside-diameter, split-barrel sampler a distance of 18 inches into the soil with a 140-pound hammer free-falling a distance of 30 inches. The number of blows for each 6-inch interval is recorded, and the number of blows required to drive the sampler the final 12 inches is known as the Standard Penetration Resistance (“N”) or blow count. If a total of 50 is recorded within one 6-inch interval, the blow count is recorded as the number of blows for the corresponding number of inches of penetration. The resistance, or N-value, provides a measure of the relative density of granular soils or the relative consistency of cohesive soils; these values are plotted on the attached exploration boring logs. The samples obtained from the split-barrel sampler were classified in the field and representative portions placed in watertight containers. The samples were then transported to our laboratory for further visual classification. Subsurface Exploration, Geologic Hazard, Lindbergh High School Additions and Geotechnical Engineering Report Renton, Washington Project and Site Conditions February 7, 2022 ASSOCIATED EARTH SCIENCES, INC. ART/ld - 20000669E005-006 Page 4 4.0 SUBSURFACE CONDITIONS 4.1 Regional Geology and Soils Mapping Published geologic mapping for the site and immediate vicinity were reviewed on the United States Geological Survey (USGS) National Geologic Map Database1 , and on the Washington State Department of Natural Resources (DNR) Geologic Information Portal2. These published regional geologic maps indicate that the site is underlain at shallow depths by Vashon lodgement till. Lodgement till sediments are suitable for support of moderate to heavily loaded structures with normal preparation but are not suitable for use as an infiltration receptor for collected stormwater. Subsurface conditions observed in explorations for this study were generally consistent with the referenced published geologic mapping. Review of the Natural Resources Conservation Service (NRCS) Web Soils Survey shows that the site is mapped as Alderwood gravelly sandy loam (AgC). The survey describes the soils being formed from the weathering of glacial sediments which is also generally consistent with our on-site exploration observations. 4.2 Site Stratigraphy Subsurface conditions at the project site were inferred from the field explorations accomplished for this study, visual reconnaissance of the site, and review of selected applicable geologic literature. As shown on the exploration logs, soils encountered at the site consisted of fill of variable thickness overlying native sediments interpreted as Vashon lodgement till. The following sections presents more detailed subsurface information on the sediment types encountered at the site. Fill Fill soils (those not naturally placed) were encountered in all of our recent and previous explorations in the current project area with interpreted fill thicknesses ranging between 4 to 9 feet below the existing ground surface. Fill thicknesses at the two hand-augered boring locations exceeded the depth drilled of 3 feet at each location. Figure 2 of this report includes the observed fill thickness at each of the exploration locations at the time of drilling. The fill generally consisted of loose to medium dense, moist, gray to brown, fine to medium sand with variable silt content and variable gravel content. Looser fill with organic content was encountered in exploration boring EB-6 (2003) at depths ranging between 0 and 5 feet below existing ground surface. Deleterious materials such as plywood, plastic, and metal fragments were observed in 1 https://ngmdb.usgs.gov/ngmdb/ngmdb_home.html 2 https://www.dnr.wa.gov/geologyportal Subsurface Exploration, Geologic Hazard, Lindbergh High School Additions and Geotechnical Engineering Report Renton, Washington Project and Site Conditions February 7, 2022 ASSOCIATED EARTH SCIENCES, INC. ART/ld - 20000669E005-006 Page 5 explorations EB-1 (2010), EB-1 (2004), EB-6 (2003) and HB-2 (2021). Existing fill is not recommended for foundation support and may require remedial preparation below new paving. Excavated existing fill material is suitable for reuse in structural fill applications if such reuse is specifically allowed by project plans and specifications, if excessively organic and any other deleterious materials are removed, and if moisture content is adjusted to allow compaction to the specified level and to a firm and unyielding condition. Existing fill is not suitable for infiltration of stormwater. Vashon Lodgement Till In all of our exploration borings with the exception of the hand-augered borings, we observed dense to very dense, unsorted, silty fine sand with varying amounts of gravels interpreted to represent lodgement till sediments. The observed depth to the top of lodgement till sediments ranged between 4 and 9 feet (EB-2, 2004 and EB-1, 2004, respectively) below existing ground surface elevation. In each boring that lodgement till was observed it extended beyond the depths of the explorations, with the deepest observations at 35 feet (EB-1, 2010). The upper 4 to 6 feet of the lodgement till in EB-1 (2010) and EB-6 (2003) was generally weathered and less dense, oxidized, and siltier than the lower, unweathered portions of the unit seen in other explorations. The till was deposited directly from basal, debris-laden glacial ice during the Vashon Stade of the Fraser Glaciation approximately 12,500 to 15,000 years ago. The high relative density of the unweathered till is due to its consolidation by the massive weight of the glacial ice from which it was deposited. Consequently, these materials are dense to very dense, possess high-strength, low-compressibility characteristics, and are relatively impermeable. The lodgement till is suitable for foundation support with proper preparation. Excavated lodgement till is suitable for use in structural fill applications if allowed by project specifications and provided that the moisture content is adjusted to allow compaction to a firm and unyielding condition at the specified level. The lodgement till has a large proportion of fine-grained material making it susceptible to disturbance when wet. Lodgement till is not a suitable infiltration receptor. 4.3 Hydrology Groundwater seepage was encountered in exploration borings EB-1 (July 2010) at 30 feet, EB-1 (March 2004) at 4 feet, EB-2 (March 2004) at 1 foot, and EB-3 (March 2004) at 5 to 7 feet. It is our opinion that the groundwater in each of these borings except EB-1 (July 2010) was perched near the interface between overlying existing fill and underlying lodgement till. Perched water occurs when surface water infiltrates down through relatively permeable soils, such as existing fill or weathered lodgement till and becomes trapped or “perched” atop a comparatively low-permeability barrier, such as the unweathered lodgement till. When water becomes perched within fill or above the unweathered till, it may travel laterally and may follow flow paths related to permeable zones that may not correspond to ground surface topography. Groundwater Subsurface Exploration, Geologic Hazard, Lindbergh High School Additions and Geotechnical Engineering Report Renton, Washington Project and Site Conditions February 7, 2022 ASSOCIATED EARTH SCIENCES, INC. ART/ld - 20000669E005-006 Page 6 deeper within the till such as at the location of EB-1 (July 2010) can accumulate in coarser-grained pockets or lenses and is typically discontinuous. The presence and quantity of groundwater will largely depend on the soil grain-size distribution, topography, seasonal precipitation, site use, on- and off-site land usage, and other factors. Subsurface Exploration, Geologic Hazard, Lindbergh High School Additions and Geotechnical Engineering Report Renton, Washington Geologic Hazards and Mitigations February 7, 2022 ASSOCIATED EARTH SCIENCES, INC. ART/ld - 20000669E005-006 Page 7 II.GEOLOGIC HAZARDS AND MITIGATIONS We reviewed mapped geologic hazards on the King County iMap, the previously referenced DNR map, and the City of Renton GIS (https://maps.rentonwa.gov/). The reviewed maps do not identify the presence of regulated critical slopes or erosion hazard areas on or immediately adjacent to the project areas. However, the DNR map and King County iMap show that there is a section near the southeastern edge of the project site that is mapped as a potential liquefaction hazard, which is discussed further below. It appears unlikely, in our opinion, that the current project will need to address requirements related to geotechnical critical areas. 5.0 LANDSLIDE HAZARDS AND MITIGATIONS The topography of the current project areas is relatively flat to gently sloping. We reviewed topographic contours presented on Figure 2 and did not identify any slopes greater than 40 percent within or near the project areas. Based on visual reconnaissance of the site existing slopes appear to have performed well with no visual indications of unusual erosion, slope instability, or emergent groundwater seepage. Given the subsurface conditions on the site and the inclination and height of the slopes, it is our opinion that the risk of damage to the proposed improvements by landslide activity on these slopes under both static and seismic conditions is low. No detailed quantitative assessment of slope stability was completed as part of this study, and none is warranted to support the project as currently proposed, in our opinion. 6.0 SEISMIC HAZARDS AND MITIGATIONS All of Western Washington is at risk of strong seismic events resulting from movement of the tectonic plates associated with the Cascadia Subduction Zone (CSZ), where the offshore Juan de Fuca plate subducts beneath the continental North American plate. The site lies within a zone of strong potential shaking from subduction zone earthquakes associated with the CSZ. The CSZ can produce earthquakes up to magnitude 9.0, and the recurrence interval is estimated to be on the order of 500 years. Geologists infer the most recent subduction zone earthquake occurred in 1700 (Goldfinger et al., 20121). Three main types of earthquakes are typically associated with subduction zone environments: crustal, intraplate, and interplate earthquakes. Seismic records in the Puget Sound region document a distinct zone of shallow crustal seismicity (e.g., the Seattle Fault Zone). These shallow fault zones may include surficial expressions of previous seismic 1 Goldfinger, C., Nelson, C.H., Morey, A.E., Johnson, J.E., Patton, J.R., Karabanov, E., Gutierrez-Pastor, J., Eriksson, A.T., Gracia, E., Dunhill, G., Enkin, R.J, Dallimore, A., and Vallier, T., 2012, Turbidite Event History—Methods and Implications for Holocene Paleoseismicity of the Cascadia Subduction Zone: U.S. Geological Survey Professional Paper 1661–F, 170 . Subsurface Exploration, Geologic Hazard, Lindbergh High School Additions and Geotechnical Engineering Report Renton, Washington Geologic Hazards and Mitigations February 7, 2022 ASSOCIATED EARTH SCIENCES, INC. ART/ld - 20000669E005-006 Page 8 events, such as fault scarps, displaced shorelines, and shallow bedrock exposures. The shallow fault zones typically extend from the surface to depths ranging from 16 to 19 miles. A deeper zone of seismicity is associated with the subducting Juan de Fuca plate. Subduction zone seismic events produce intraplate earthquakes at depths ranging from 25 to 45 miles beneath the Puget Lowland including the 1949, 7.2-magnitude event; the 1965, 6.5-magnitude event; and the 2001, 6.8-magnitude event and interplate earthquakes at shallow depths near the Washington coast including the 1700 earthquake, which had a magnitude of approximately 9.0. The 1949 earthquake appears to have been the largest in this region during recorded history and was centered in the Olympia area. Evaluation of earthquake return rates indicates that an earthquake of the magnitude between 5.5 and 6.0 is likely within a given 20-year period. Generally, there are four types of potential geologic hazards associated with large seismic events: 1) surficial ground rupture, 2) seismically induced landslides or lateral spreading, 3) liquefaction, 4)ground motion. The potential for each of these hazards to adversely impact the proposed project is discussed below. 6.1 Surficial Ground Rupture Generally, the largest earthquakes that have occurred in the Puget Sound area are sub-crustal events with epicenters ranging from 50 to 70 kilometers in depth. Earthquakes that are generated at such depths usually do not result in fault rupture at the ground surface. Surficial ground rupture is possible during shallower crustal events in areas close to the Seattle Fault Zone, which is located approximately 4.5 miles to the north and is the closest mapped fault zone to the project. Due to the suspected long recurrence interval, and the distance of the site to known fault traces, the potential for surficial ground rupture to occur at the project site is considered to be low during the expected life of the proposed structures. 6.2 Liquefaction Liquefaction is a process through which unconsolidated soil loses strength as a result of vibrations, such as those which occur during a seismic event. During normal conditions, the weight of the soil is supported by both grain-to-grain contacts and by the fluid pressure within the pore spaces of the soil below the water table. Extreme vibratory shaking can disrupt the grain-to-grain contact, increase the pore pressure, and result in a temporary decrease in soil shear strength. The soil is said to be liquefied when nearly all of the weight of the soil is supported by pore pressure alone. Liquefaction can result in deformation of the sediment and settlement of overlying structures. Areas most susceptible to liquefaction include those areas underlain by very soft to stiff, non-cohesive silt and very loose to medium dense, non-silty to silty sands with low relative densities, accompanied by a shallow water table. Subsurface Exploration, Geologic Hazard, Lindbergh High School Additions and Geotechnical Engineering Report Renton, Washington Geologic Hazards and Mitigations February 7, 2022 ASSOCIATED EARTH SCIENCES, INC. ART/ld - 20000669E005-006 Page 9 There is a portion of the southeastern edge of the site that is mapped as a liquefaction hazard. The mapped hazard is outside of the proposed improvement areas. The proposed project is not expected to have high risk of damage due to liquefaction because substantial deposits of saturated loose granular sediments were not observed. A detailed liquefaction hazard analysis was not performed as part of this study, and none is warranted based on existing subsurface data, in our opinion. 6.3 Ground Motion/Seismic Site Class (2018 International Building Code) Structural design of the new building additions should follow 2018 International Building Code (IBC) standards. We recommend that the project be designed in accordance with Site Class “C” in accordance with the 2018 IBC, and the publication American Society of Civil Engineers (ASCE) 7 referenced therein, the most recent version of which is ASCE 7-16. 7.0 EROSION CONTROL Project plans should include implementation of temporary erosion controls in accordance with local standards of practice. Control methods should include limiting earthwork to seasonally drier periods, if possible, use of perimeter silt fences, stabilized construction entrances, and straw mulch in exposed areas. Removal of existing vegetation should be limited to those areas that are required to construct the project, and new landscaping and vegetation with equivalent erosion mitigation potential should be established as soon as practical after grading is complete. During construction, surface water should be collected as close as possible to the source to minimize silt entrainment that could require treatment or detention prior to discharge. Timely implementation of permanent drainage control measures should also be a part of the project plans, and will help reduce erosion and generation of silty surface water onsite. The Ecology Construction Storm Water General Permit requires weekly Temporary Erosion and Sedimentation Control (TESC) inspections, turbidity monitoring and pH monitoring for all sites 1 or more acre in size that discharge stormwater to surface waters of the state. Because we anticipate that the proposed project will not require disturbance of more than 1 acre, we anticipate that these inspection and reporting requirements will not be triggered. The following recommendations are related to general erosion potential and mitigation. Best management practices (BMPs) should include but not be limited to: 1.Construction activity should be scheduled or phased as much as possible to reduce the amount of earthwork activity that is performed during the winter months. 2.The winter performance of a site is dependent on a well-conceived plan for control of site erosion and stormwater runoff. The site plan should include ground-cover measures, Subsurface Exploration, Geologic Hazard, Lindbergh High School Additions and Geotechnical Engineering Report Renton, Washington Geologic Hazards and Mitigations February 7, 2022 ASSOCIATED EARTH SCIENCES, INC. ART/ld - 20000669E005-006 Page 10 access roads, and staging areas. The contractor should be prepared to implement and maintain the required measures to reduce the amount of exposed ground. 3.TESC measures for a given area to be graded or otherwise worked should be installed soon after ground clearing. The recommended sequence of construction within a given area after clearing would be to install TESC elements and perimeter flow control prior to starting grading. 4.During the wetter months of the year, or when large storm events are predicted during the summer months, each work area should be stabilized so that if showers occur, the work area can receive the rainfall without excessive erosion or sediment transport. The required measures for an area to be “buttoned-up” will depend on the time of year and the duration the area will be left unworked. During the winter months, areas that are to be left unworked for more than 2 days should be mulched or covered with plastic. During the summer months, stabilization will usually consist of seal-rolling the subgrade. Such measures will aid in the contractor’s ability to get back into a work area after a storm event. The stabilization process also includes establishing temporary stormwater conveyance channels through work areas to route runoff to the approved treatment/discharge facilities. 5.All disturbed areas should be revegetated as soon as possible. If it is outside of the growing season, the disturbed areas should be covered with mulch, as recommended in the erosion control plan. Straw mulch provides a cost-effective cover measure and can be made wind-resistant with the application of a tackifier after it is placed. 6.Surface runoff and discharge should be controlled during and following development. Uncontrolled discharge may promote erosion and sediment transport. Under no circumstances should concentrated discharges be allowed to flow over the top of steep slopes. 7.Soils that are to be reused around the site should be stored in such a manner as to reduce erosion from the stockpile. Protective measures may include, but are not limited to, covering with plastic sheeting, the use of low stockpiles in flat areas, or the use of silt fences around pile perimeters. It is our opinion that with the proper implementation of the TESC plans and by field-adjusting appropriate mitigation elements (BMPs) during construction, the potential adverse impacts from erosion hazards on the project may be mitigated. Subsurface Exploration, Geologic Hazard, Lindbergh High School Additions and Geotechnical Engineering Report Renton, Washington Design Recommendations February 7, 2022 ASSOCIATED EARTH SCIENCES, INC. ART/ld - 20000669E005-006 Page 11 III.DESIGN RECOMMENDATIONS 8.0 INTRODUCTION Our explorations indicate that, from a geotechnical engineering standpoint, the proposed building additions are feasible provided the recommendations contained herein are properly followed. The project area is underlain by a layer of existing fill that is variable in thickness and density. Existing fill or loose soils are not suitable for support of new foundations, and warrant remedial preparation where occurring below paving. Area A - Building addition Area A, is underlain by existing loose fill of various thickness. Area A building additions will be supported on pin piles that derive their support from dense soils below the fill. Areas F2 and F3 - These building addition areas will be supported on a combination of shallow foundations and pin piles that derive their support from dense soils below the fill. 9.0 SITE PREPARATION Erosion and surface water control should be established around the perimeter of the excavation to satisfy City of Renton requirements. Building Pad Areas - Site preparation should include removal of all existing pavement, structures, buried utilities, and any other deleterious material from below the new building additions. Existing fill should be removed to expose suitable native materials suitable for structural support. Structural fill may then be placed as needed to reach building pad grade. At the time this report is written a site development plan has not been selected. We should be allowed to review the site development plan when one is selected and discuss possible site preparation and structural support plans that are appropriate to the project plan. Paving Areas - Areas of planned paving should be prepared by stripping existing vegetation and topsoil, removing structures and utilities to be demolished, and excavating to planned paving subgrade elevation. The resulting subgrade should then be evaluated visually, compacted, and proof-rolled. Exposed soils are expected to consist of existing fill and lodgement till depending on the location and finished subgrade elevation. Areas with organic or deleterious material, or areas that yield during proof-rolling should receive additional preparation tailored to proof- rolling results and field conditions at the time of construction. Subsurface Exploration, Geologic Hazard, Lindbergh High School Additions and Geotechnical Engineering Report Renton, Washington Design Recommendations February 7, 2022 ASSOCIATED EARTH SCIENCES, INC. ART/ld - 20000669E005-006 Page 12 9.1 Site Drainage and Surface Water Control The site should be graded to prevent water from ponding in construction areas and/or flowing into excavations. Exposed grades should be crowned, sloped, and smooth drum-rolled at the end of each day to facilitate drainage. Accumulated water must be removed from subgrades and work areas immediately prior to performing further work in the area. Equipment access may be limited, and the amount of soil rendered unfit for use as structural fill may be greatly increased if drainage efforts are not accomplished in a timely sequence. If an effective drainage system is not utilized, project delays and increased costs could be incurred due to the greater quantities of wet and unsuitable fill, or poor access and unstable conditions. We do not anticipate the need for extensive dewatering in advance of excavations. However, the contractor should be prepared to intercept any groundwater seepage entering the excavations and route it to a suitable discharge location. Final exterior grades should promote free and positive drainage away from buildings at all times. Water must not be allowed to pond or to collect adjacent to foundations or within immediate building areas. We recommend that a gradient of at least 3 percent for a minimum distance of 10 feet from the building perimeters be provided, except in paved locations. In paved locations, a minimum gradient of 1 percent should be provided, unless provisions are included for collection and disposal of surface water adjacent to the structure. 9.2 Subgrade Protection If building construction will proceed during the winter, we recommend the use of a working surface of sand and gravel, crushed rock, or quarry spalls to protect exposed soils, particularly in areas supporting concentrated equipment traffic. In winter construction staging areas and areas that will be subjected to repeated heavy loads, such as those that occur during construction of masonry walls, a minimum thickness of 12 inches of quarry spalls or 18 inches of pit run sand and gravel is recommended. If subgrade conditions are soft and silty, a geotextile separation fabric, such as Mirafi 500X or approved equivalent, should be used between the subgrade and the new fill. For building pads where floor slabs and foundation construction will be completed in the winter, a similar working surface should be used, composed of at least 6 inches of pit run sand and gravel or crushed rock. Construction of working surfaces from advancing fill pads could be used to avoid directly exposing the subgrade soils to vehicular traffic. Foundation subgrades may require protection from foot and equipment traffic and ponding of runoff during wet weather conditions. Typically, compacted crushed rock or a lean-mix concrete mat placed over a properly prepared subgrade provides adequate subgrade protection. Foundation concrete should be placed and excavations backfilled as soon as possible to protect the bearing surface. Subsurface Exploration, Geologic Hazard, Lindbergh High School Additions and Geotechnical Engineering Report Renton, Washington Design Recommendations February 7, 2022 ASSOCIATED EARTH SCIENCES, INC. ART/ld - 20000669E005-006 Page 13 9.3 Proof-Rolling and Subgrade Compaction Following the recommended clearing, site stripping, planned excavation, and any overexcavation required to remove existing fill, the stripped subgrade within the building areas should be proof-rolled with heavy, rubber-tired construction equipment, such as a fully-loaded tandem- axle dump truck. Proof-rolling should be performed prior to structural fill placement or foundation excavation. The proof-roll should be monitored by the geotechnical engineer so that any soft or yielding subgrade soils can be identified. Any soft/loose, yielding soils should be removed to a stable subgrade. The subgrade should then be scarified, adjusted in moisture content, and recompacted to the required density. Proof-rolling should only be attempted if soil moisture contents are at or near optimum moisture content. Proof-rolling of wet subgrades could result in further degradation. Low areas and excavations may then be raised to the planned finished grade with compacted structural fill. Subgrade preparation and selection, placement, and compaction of structural fill should be performed under engineering-controlled conditions in accordance with the project specifications. 9.4 Overexcavation/Stabilization Construction during extended wet weather periods could create the need to overexcavate exposed soils if they become disturbed and cannot be recompacted due to elevated moisture content and/or weather conditions. Even during dry weather periods, soft/wet soils, which may need to be overexcavated, may be encountered in some portions of the site. If overexcavation is necessary, it should be confirmed through continuous observation and testing by AESI. Soils that have become unstable may require remedial measures in the form of one or more of the following: 1.Drying and recompaction. Selective drying may be accomplished by scarifying or windrowing surficial material during extended periods of dry and warm weather. 2.Removal of affected soils to expose a suitable bearing subgrade and replacement with compacted structural fill. 3.Mechanical stabilization with a coarse crushed aggregate compacted into the subgrade, possibly in conjunction with a geotextile. 4.Soil/cement admixture stabilization. 9.5 Wet Weather Conditions If construction proceeds during an extended wet weather construction period and the moisture-sensitive site soils become wet, they will become unstable. Therefore, the bids for site Subsurface Exploration, Geologic Hazard, Lindbergh High School Additions and Geotechnical Engineering Report Renton, Washington Design Recommendations February 7, 2022 ASSOCIATED EARTH SCIENCES, INC. ART/ld - 20000669E005-006 Page 14 grading operations should be based upon the time of year that construction will proceed. It is expected that in wet conditions additional soils may need to be removed and/or other stabilization methods used, such as a coarse crushed rock working mat to develop a stable condition if silty subgrade soils are disturbed in the presence of excess moisture. The severity of construction disturbance will be dependent, in part, on the precautions that are taken by the contractor to protect the moisture- and disturbance-sensitive site soils. If overexcavation is necessary, it should be confirmed through continuous observation and testing by a representative of our firm. 9.6 Temporary and Permanent Cut Slopes In our opinion, stable construction slopes should be the responsibility of the contractor and should be determined during construction. For estimating purposes, however, we anticipate that temporary, unsupported cut slopes in the existing fill can be made at a maximum slope of 1.5H:1V or flatter. Temporary slopes in dense to very dense till sediments may be planned at 1H:1V. As is typical with earthwork operations, some sloughing and raveling may occur, and cut slopes may have to be adjusted in the field. If groundwater seepage is encountered in cut slopes, or if surface water is not routed away from temporary cut slope faces, flatter slopes will be required. In addition, WISHA/OSHA regulations should be followed at all times. Permanent cut and structural fill slopes that are not intended to be exposed to surface water should be designed at inclinations of 2H:1V or flatter. All permanent cut or fill slopes should be compacted to at least 95 percent of the modified Proctor maximum dry density, as determined by ASTM D-1557, and the slopes should be protected from erosion by sheet plastic until vegetation cover can be established during favorable weather. 9.7 Frozen Subgrades If earthwork takes place during freezing conditions, all exposed subgrades should be allowed to thaw and then be recompacted prior to placing subsequent lifts of structural fill or foundation components. Alternatively, the frozen material could be stripped from the subgrade to reveal unfrozen soil prior to placing subsequent lifts of fill or foundation components. The frozen soil should not be reused as structural fill until allowed to thaw and adjusted to the proper moisture content, which may not be possible during winter months. 10.0 STRUCTURAL FILL Structural fill should be placed and compacted according to the recommendations presented in this section and requirements included in project specifications. All references to structural fill in this report refer to subgrade preparation, fill type, placement, and compaction of materials, as discussed in this section. If a percentage of compaction is specified under another section of this report, the value given in that section should be used. Subsurface Exploration, Geologic Hazard, Lindbergh High School Additions and Geotechnical Engineering Report Renton, Washington Design Recommendations February 7, 2022 ASSOCIATED EARTH SCIENCES, INC. ART/ld - 20000669E005-006 Page 15 Structural fill is defined as non-organic soil, acceptable to the geotechnical engineer, placed in maximum 8-inch loose lifts, with each lift being compacted to at least 95 percent of the modified Proctor maximum dry density using ASTM D-1557 as the standard. In the case of roadway and utility trench filling, the backfill should be placed and compacted in accordance with City of Renton standards. For planning purposes, we recommend the use of a well-graded sand and gravel for road and utility trench backfill. At this time we are not aware of any planned right-of-way work associated with the project. The contractor should note that AESI should evaluate any proposed fill soils prior to their use in fills. This would require that we have a sample of the material at least 3 business days in advance of filling activities to perform a Proctor test and determine its field compaction standard. Soils in which the amount of fine-grained material (smaller than the No. 200 sieve) is greater than approximately 5 percent (measured on the minus No. 4 sieve size) should be considered moisture-sensitive. Use of moisture-sensitive soil in structural fills is not recommended during the winter months or under wet site and weather conditions. Most of the on-site soils are moisture-sensitive and have natural moisture contents over optimum for compaction and will likely require moisture-conditioning before use as structural fill. In addition, construction equipment traversing the site when the soils are wet can cause considerable disturbance. If import soil is required, a select import material consisting of a clean, free-draining gravel and/or sand should be used. Free-draining fill consists of non-organic soil with the amount of fine-grained material limited to 5 percent by weight when measured on the minus No. 4 sieve fraction and at least 30 percent retained on the No. 4 sieve. A representative from our firm should observe the subgrades and be present during placement of structural fill to observe the work and perform a representative number of in-place density tests. In this way, the adequacy of the earthwork may be evaluated as filling progresses and any problem areas may be corrected at that time. It is important to understand that taking random compaction tests on a part-time basis will not assure uniformity or acceptable performance of a fill. As such, we are available to aid the owner in developing a suitable monitoring and testing frequency. 11.0 FOUNDATIONS The project uses a combination of conventional shallow foundations and pin piles to support new structures. Pin piles are currently planned below portions of Area A and Area F2. Subsurface Exploration, Geologic Hazard, Lindbergh High School Additions and Geotechnical Engineering Report Renton, Washington Design Recommendations February 7, 2022 ASSOCIATED EARTH SCIENCES, INC. ART/ld - 20000669E005-006 Page 16 11.1 Shallow Foundations We expect the depth from existing grade to bearing soil in building addition areas will vary, however we anticipate that existing fill does not extend deeper than foundation level for existing buildings adjacent to the additions. The existing on-site fill was thickest (about 9 feet in depth) in the southwestern portion of the site, in the vicinity of EB-1 (2004). Where present, existing fill should be removed below the building pad, exposing medium dense to very dense native sediments. Spread footings may be used for building support when founded directly on undisturbed native sediments, on structural fill placed over suitable native sediments. If foundations will be supported by a combination of very dense native sediments and new structural fill, we recommend that an allowable bearing pressure of 3,000 pounds per square foot (psf) be used for design purposes, including both dead and live loads. Higher foundation soil bearing pressures may be suitable if new footings will be supported entirely on dense to very dense native soils. An increase of one-third may be used for short-term wind or seismic loading. Perimeter footings should be buried at least 18 inches into the surrounding soil for frost protection. However, all footings must penetrate to the prescribed bearing stratum, and no footing should be founded in or above organic or loose soils. It should be noted that the area bound by lines extending downward at 1H:1V from any footing must not intersect another footing or intersect a filled area that has not been compacted to at least 95 percent of ASTM D-1557. In addition, a 1.5H:1V line extending down from any footing must not daylight because sloughing or raveling may eventually undermine the footing. Thus, footings should not be placed near the edge of steps or cuts in the bearing soils. Anticipated settlement of footings founded as described above should be on the order of ¾ inch or less. However, disturbed soil not removed from footing excavations prior to footing placement and footings placed above loose soils could result in increased settlements. All footing areas should be inspected by AESI prior to placing concrete to verify that the design bearing capacity of the soils has been attained and that construction conforms to the recommendations contained in this report. Such inspections may be required by the governing municipality. Perimeter footing drains should be provided, as discussed under the “Drainage Considerations” Section 14.0 of this report. 11.2 Pin Piles Pin piles should be installed by a local contractor with demonstrated expertise in pin pile installations. Current plans call for the use of pin piles with axial compressive capacity of 12,000 pounds on a 3-inch-diameter pile. Piles with smaller and larger capacities are possible, Subsurface Exploration, Geologic Hazard, Lindbergh High School Additions and Geotechnical Engineering Report Renton, Washington Design Recommendations February 7, 2022 ASSOCIATED EARTH SCIENCES, INC. ART/ld - 20000669E005-006 Page 17 if needed. We have reviewed current project plans dated January 12, 2022 for geotechnical aspects of pin pile construction and find pin piles depicted on those plans consistent with our geotechnical engineering recommendations. In general, pin piles are installed with an air or hydraulic impact hammer until the specified refusal criteria are met. If multiple pipe sections are required, the pipes should be joined with an extension pin inside the pipe, and/or a sleeve on the outside. If uplift loads are expected to be placed on the piles at any time, the connections should also be securely welded to prevent pipe separation at joints. Although vertical pin piles can provide small uplift and lateral capacities, we recommend that these contributions be neglected in designing the new foundation system. The structural engineer should provide pile spacing, locations, splicing details, foundation connection details, and any other structural design recommendations that are needed. Pin piles are driven until specific refusal criteria are achieved. Pile lengths are difficult to estimate in advance. At this site in addition to achieving the required driving resistance, piles are required to reach a minimum depth. We recommend that piles fully penetrate existing fill soils to bear on lodgement till, and that all piles achieve a minimum penetration depth of 5 feet below the level of any adjacent temporary or permanent excavations. It should be noted that the subsurface conditions that will be encountered during pile driving could include construction waste and compacted fill soils. We recommend that we be allowed to observe the installation of pin piles. We would observe materials, equipment, and procedures, and confirm refusal for each pile. The purpose of our observations is to confirm that the conditions observed in our explorations and assumed in preparation of our recommendations are consistent with those encountered at the time of construction, and to confirm that the materials, procedures, and refusal criteria are consistent with those we assumed while formulating our recommendations contained in this report. We recommend that we be allowed to agree on mutually acceptable driving resistance criteria with the pile contractor selected for the project, and that the agreed-on driving criteria be verified by at least one load test for each pile type. 12.0 FLOOR SUPPORT If crawl-space floors are used, an impervious moisture barrier should be provided above the soil surface within the crawl space. Slab-on-grade floors may be used over medium dense to very dense native soils, or over structural fill placed as recommended in the “Site Preparation” and “Structural Fill” sections of this report. Slab-on-grade floors should be cast atop a minimum of 4 inches of washed pea gravel or washed crushed “chip” rock with less than 3 percent passing Subsurface Exploration, Geologic Hazard, Lindbergh High School Additions and Geotechnical Engineering Report Renton, Washington Design Recommendations February 7, 2022 ASSOCIATED EARTH SCIENCES, INC. ART/ld - 20000669E005-006 Page 18 the U.S. No. 200 sieve to act as a capillary break. The floors should also be protected from dampness by covering the capillary break layer with an impervious moisture barrier at least 10 mils in thickness. If any of the building addition areas will use pin pile support for foundations, floors could be supported on pin piles. Alternatively, floor slabs could be supported by a new layer of compacted structural fill at least 2 feet thick, underlain by existing fill soils. If this alternative is selected, the existing fill soil should be prepared in accordance with the “Site Preparation” section of this report, and new fill should be placed as recommended in the “Structural Fill” section. If existing fill is left in place below new floors and pin piles are not used for floor support, there is some potential for larger than normal post-construction settlement. The settlement risk is offset by substantial cost savings at the time of construction. We are available on request to discuss floor support over existing fill. 13.0 FOUNDATION WALLS All backfill behind foundation walls or around foundation units should be placed as per our recommendations for structural fill and as described in this section of the report. Horizontally backfilled walls, which are free to yield laterally at least 0.1 percent of their height, may be designed to resist active earth pressure represented by an equivalent fluid equal to 35 pounds per cubic foot (pcf). Fully restrained, horizontally backfilled, rigid walls that cannot yield should be designed for an equivalent fluid of 50 pcf. Walls with sloping backfill up to a maximum gradient of 2H:1V should be designed using an equivalent fluid of 55 pcf for yielding conditions or 75 pcf for fully restrained conditions. If parking areas are adjacent to walls, a surcharge equivalent to 2 feet of soil should be added to the wall height in determining lateral design forces. As required by the 2018 IBC, retaining wall design should include a seismic surcharge pressure in addition to the equivalent fluid pressures presented above. Considering the site soils and the recommended wall backfill materials, we recommend a seismic surcharge pressure of 5H and 10H psf, where H is the wall height in feet for the “active” and “at-rest” loading conditions, respectively. The seismic surcharge should be modeled as a rectangular distribution with the resultant applied at the midpoint of the walls. The lateral pressures presented above are based on the conditions of a uniform backfill consisting of excavated on-site soils, or imported structural fill compacted to 90 percent of ASTM D-1557. A higher degree of compaction is not recommended, as this will increase the pressure acting on the walls. A lower compaction may result in settlement of the slab-on-grade or other structures supported above the walls. Thus, the compaction level is critical and must be tested by our firm during placement. Surcharges from adjacent footings or heavy construction equipment must be Subsurface Exploration, Geologic Hazard, Lindbergh High School Additions and Geotechnical Engineering Report Renton, Washington Design Recommendations February 7, 2022 ASSOCIATED EARTH SCIENCES, INC. ART/ld - 20000669E005-006 Page 19 added to the above values. Perimeter footing drains should be provided for all retaining walls, as discussed under the “Drainage Considerations” section of this report. It is imperative that proper drainage be provided so that hydrostatic pressures do not develop against the walls. This would involve installation of a minimum, 1-foot-wide blanket drain to within 1 foot of finish grade for the full wall height using imported, washed gravel against the walls. A prefabricated drainage mat is not a suitable substitute for the gravel blanket drain unless all backfill against the wall is free-draining. 13.1 Passive Resistance and Friction Factors Lateral loads can be resisted by friction between the foundation and the natural glacial soils or supporting structural fill soils, and by passive earth pressure acting on the buried portions of the foundations. The foundations must be backfilled with structural fill and compacted to at least 95 percent of the maximum dry density to achieve the passive resistance provided below. We recommend the following allowable design parameters: •Passive equivalent fluid = 250 pcf •Coefficient of friction = 0.35 14.0 DRAINAGE CONSIDERATIONS All retaining and perimeter foundation walls should be provided with a drain at the base of the footing elevation. Drains should consist of rigid, perforated, PVC pipe surrounded by washed drain rock. The level of the perforations in the pipe should be set at or slightly below the bottom of the footing grade beam, and the drains should be constructed with sufficient gradient to allow gravity discharge away from the building. In addition, all retaining walls should be lined with a minimum, 12-inch-thick, washed gravel blanket that extends to within 1 foot of the surface and is continuous with the foundation drain. Roof and surface runoff should not discharge into the foundation drain system, but should be handled by a separate, rigid, tightline drain. In planning, exterior grades adjacent to walls should be sloped downward away from the structure to achieve surface drainage. 15.0 PAVEMENT AND SIDEWALK RECOMMENDATIONS The pavement sections included in this report section are for driveway and parking areas onsite, and are not applicable to right-of-way improvements. At this time, we are not aware of any planned right-of-way improvements; however, if any new paving of public streets is required, we should be allowed to offer situation-specific recommendations. Subsurface Exploration, Geologic Hazard, Lindbergh High School Additions and Geotechnical Engineering Report Renton, Washington Design Recommendations February 7, 2022 ASSOCIATED EARTH SCIENCES, INC. ART/ld - 20000669E005-006 Page 20 Pavement and sidewalk areas should be prepared in accordance with the “Site Preparation” section of this report. Soft or yielding areas should be overexcavated to provide a suitable subgrade and backfilled with structural fill. New paving may include areas subject only to light traffic loads from passenger vehicles driving and parking, and may also include areas subject to heavier loading from vehicles that may include buses, fire trucks, food service trucks, and garbage trucks. In light traffic areas, we recommend a pavement section consisting of 3 inches of hot-mix asphalt (HMA) underlain by 4 inches of crushed surfacing base course. In heavy traffic areas, we recommend a minimum pavement section consisting of 4 inches of HMA underlain by 2 inches of crushed surfacing top course and 4 inches of crushed surfacing base course. The crushed rock courses must be compacted to 95 percent of the maximum density, as determined by ASTM D-1557. All paving materials should meet gradation criteria contained in the current Washington State Department of Transportation (WSDOT) Standard Specifications. Depending on construction staging and desired performance, the crushed base course material may be substituted with asphalt treated base (ATB) beneath the final asphalt surfacing, if desired. The substitution of ATB should be as follows: 4 inches of crushed rock can be substituted with 3 inches of ATB, and 6 inches of crushed rock may be substituted with 4 inches of ATB. ATB should be placed over a native or structural fill subgrade compacted to a minimum of 95 percent relative density, and a 1½- to 2-inch thickness of crushed rock to act as a working surface. If ATB is used for construction access and staging areas, some rutting and disturbance of the ATB surface should be expected to result from construction traffic. The contractor should remove any ATB areas damaged by construction equipment and replace them with properly compacted ATB prior to final surfacing. 16.0 INFILTRATION FEASIBILITY The on-site soils consist of fill and dense silty glacial till. The existing fill is not permitted to serve as an infiltration receptor, and lodgement till is not a suitable infiltration receptor due to low permeability. Stormwater infiltration is not recommended. 17.0 PROJECT DESIGN AND CONSTRUCTION MONITORING We recommend that AESI perform a geotechnical review of the plans prior to final design completion. In this way, we can confirm that our recommendations have been correctly interpreted and implemented in the design. The City of Renton may require a plan review by the geotechnical engineer as a condition of permitting. Subsurface Exploration, Geologic Hazard, Lindbergh High School Additions and Geotechnical Engineering Report Renton, Washington Design Recommendations February 7, 2022 ASSOCIATED EARTH SCIENCES, INC. ART/ld - 20000669E005-006 Page 21 We recommend that AESI be retained to provide geotechnical special inspections during construction, and preparation of a final summary letter when construction is complete. The City of Renton may require such geotechnical special inspections. The integrity of the earthwork and foundations depends on proper site preparation and construction procedures. In addition, engineering decisions may have to be made in the field in the event that variations in subsurface conditions become apparent. We have enjoyed working with you on this study and are confident these recommendations will aid in the successful completion of your project. If you should have any questions or require further assistance, please do not hesitate to call. Sincerely, ASSOCIATED EARTH SCIENCES, INC. Kirkland, Washington ______________________________ Bruce W. Guenzler, L.E.G. Kurt D. Merriman. P.E. Senior Associate Geologist Senior Principal Engineer Attachments: Figure 1. Vicinity Map Figure 2. Existing Site and Exploration Plan Appendix A. Exploration Logs KING COUNTY KING COUNTY RENTON PROJ NO. NOTE: BLACK AND WHITE REPRODUCTION OF THIS COLORORIGINAL MAY REDUCE ITSEFFECTIVENESS AND LEAD TOINCORRECT INTERPRETATION DATE:FIGURE: ±\\kirkfile2\GIS\GIS_Projects\aY00post0716\000669 Lindbergh HS\aprx\20000669E005 F1 VM_Lindbergh.aprx | 20000669E005 F1 VM_Lindbergh | 9/13/2021 2:53 PMDATA SOURCES / REFERENCES: USGS: 7.5' SERIES TOPOGRAPHIC MAPS, ESRI/I-CUBED/NGS 2013 KING CO: STREETS, CITY LIMITS, PARCELS, PARKS 3/20 LOCATIONS AND DISTANCES SHOWN ARE APPROXIMATE 0 2000 Feet VICINITY MAP LINDBERGH HS IMPROVEMENTS RENTON, WASHINGTON 20000669E005 9/21 1 King County ¥ ¥ ¥ ¬« ¬«169 !( SITE King County !( !( !( !( !( !( !( !( !( !( 420410 4304 0 0 410400430 420 39042 0400 King CountyRentonHB-1 HB-2 EB-6, 5.5FT EB-1, 8FT EB-1, 4FT EB-2, 7FT EB-3, 6FT EB-1, 9FT EB-2, 4FT EB-3, 5FT EagleView Technologies, Inc. ± BLACK AND WHITE REPRODUCTION OF THIS COLOR ORIGINAL MAY REDUCE ITSEFFECTIVENESS AND LEAD TO INCORRECT INTERPRETATION \\kirkfile2\gis\GIS_Projects\aY00post0716\000669 Lindbergh HS\aprx\20000669E005 F2 ES_Lindbergh.aprx | 20000669E005 F2 ES_Lindbergh | 9/27/2021 9:23 AMPROJ NO.DATE:FIGURE: 0 80 FEET NOTE: HISTORICAL EXPLORATIONS OUTSIDE THE CURRENT WORK AREA ARE NOT SHOWN ON THE FIGURE AND NOT INCLUDED IN THE APPENDIX DATA SOURCES / REFERENCES: PSLC: KING COUNTY 2016, GRID CELL SIZE IS 3'.DELIVERY 1 FLOWN 2/24/16 - 3/28/16CONTOURS FROM LIDAR KING CO: STREETS, PARCELS, 3/20 AERIAL PICTOMETRY INT. 2019 LOCATIONS AND DISTANCES SHOWN ARE APPROXIMATE 20000669E005 9/21 2 EXISTING SITE AND EXPLORATION PLAN LINDBERGH HS ADDITIONS RENTON, WASHINGTON LEGEND SITE !(EXPLORATION BORING, DEPTH OF FILL (2021) !(HAND BORING (2021) !(EXPLORATION BORING, DEPTH OF FILL (2010) !(EXPLORATION BORING, DEPTH OF FILL (2004) !(EXPLORATION BORING, DEPTH OF FILL (2003) CITY BOUNDARY PARCEL CONTOUR 10 FT CONTOUR 2 FT APPENDIX A Exploration Logs Topsoil - 4 to 6 inches Fill Moist, grayish brown, silty, fine SAND, some medium to coarse sand, tracegravel; unsorted (SM). Vashon Lodgement Till Moist, grayish brown, silty, fine SAND, some medium to coarse sand,some gravel; unsorted (SM). As above. Driller reports hard drilling. Moist, grayish brown, silty, fine SAND, some medium to coarse sand,some broken gravel; diamict (SM). Moist, grayish brown, silty, fine SAND, some medium to coarse sand, tracegravel; diamict (SM). Driller reports hard drilling. Moist to very moist, grayish brown, silty, fine SAND, some medium tocoarse sand; contains broken gravel; occasional sand lens; diamict (SM). S-1 S-2 S-3 S-4 S-5 S-6 202627 122027 203550/5" 2650/3" 50/6" 354350/5" Bottom of exploration boring at 21.4 feetNo groundwater encountered. Ground Surface Elevation (ft) Grab SampleSymbol 3.25 inch ID, +/- 8 inch OD 40 Datum Hammer Weight/Drop Sampler Type (ST): ~425 5 10 15 20 EB-1 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name Water Level ()Approved by: 30 Blows/Foot SamplesDepth (ft)S T Exploration Number20000669E005 9/11/21,9/11/21 Logged by: Shelby Tube Sample 140# / 30Advanced Drill Technologies / D-50 Track Mount Exploration Boring Water Level at time of drilling (ATD) Lindbergh High School Additions M - Moisture Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet1 of 1 NAVD 88 WellAESIBOR 20000669E005.GPJ September 27, 202153 4747 5050/5" 5050/3" 5050/6" 5050/5" Topsoil - 4 to 6 inches Fill Moist, brownish gray with faint iron oxide staining, silty, fine SAND, somemedium to coarse sand, some gravel; unsorted (SM) Moist, grayish brown, silty, fine SAND, some medium to coarse sand, tracegravel; unsorted (SM). Drilling action changes at 7 feet. Vashon Lodgement Till Moist, grayish brown, silty, fine SAND, some medium to coarse sand, tracegravel; diamict (SM). Moist, grayish brown, silty, fine SAND, trace medium to coarse sand;diamict (SM). Moist, grayish brown, silty, fine SAND, some medium to coarse sand, tracegravel; diamict (SM). No recovery due to gravel. S-1 S-2 S-3 S-4 S-5 S-6 643 338 3050/6" 2050/6" 50/6" 50/2" Bottom of exploration boring at 20.2 feetNo groundwater encountered. Ground Surface Elevation (ft) Grab SampleSymbol 3.25 inch ID, +/- 8 inch OD 40 Datum Hammer Weight/Drop Sampler Type (ST): ~427.5 5 10 15 20 EB-2 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name Water Level ()Approved by: 30 Blows/Foot SamplesDepth (ft)S T Exploration Number20000669E005 9/11/21,9/11/21 Logged by: Shelby Tube Sample 140# / 30Advanced Drill Technologies / D-50 Track Mount Exploration Boring Water Level at time of drilling (ATD) Lindbergh High School Additions M - Moisture Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet1 of 1 NAVD 88 WellAESIBOR 20000669E005.GPJ September 27, 202177 1111 5050/6" 5050/6" 5050/6" 5050/2" Topsoil - 4 to 6 inches Fill Moist, brownish gray with oxidation, silty, fine SAND, some medium tocoarse sand; unsorted (SM). Moist, grayish brown, silty, fine SAND, some medium to coarse sand, tracegravel; fill lifts; unsorted (SM). Vashon Lodgement TillDrill change at 6 feet. Moist, grayish brown, silty, fine SAND, some medium to coarse sand, tracebroken gravel; diamict (SM). As above. As above; faint iron oxide staining. As above. S-1 S-2 S-3 S-4 S-5 S-6 325 152028 1450/6" 1950/6" 50/4" 50/5" Bottom of exploration boring at 20.4 feetNo groundwater encountered. Ground Surface Elevation (ft) Grab SampleSymbol 3.25 inch ID, +/- 8 inch OD 40 Datum Hammer Weight/Drop Sampler Type (ST): ~422.5 5 10 15 20 EB-3 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name Water Level ()Approved by: 30 Blows/Foot SamplesDepth (ft)S T Exploration Number20000669E005 9/11/21,9/11/21 Logged by: Shelby Tube Sample 140# / 30Advanced Drill Technologies / D-50 Track Mount Exploration Boring Water Level at time of drilling (ATD) Lindbergh High School Additions M - Moisture Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet1 of 1 NAVD 88 WellAESIBOR 20000669E005.GPJ September 27, 202177 4848 5050/6" 5050/6" 5050/4" 5050/5" Landscaping Mulch - 2 to 3 inches Fill Loose, moist, light brown, silty, fine SAND, some gravel, some medium tocoarse sand; unsorted (SM). As above. S-1 S-2 Bottom of exploration boring at 3 feetNo groundwater encountered. Ground Surface Elevation (ft) Grab SampleSymbol 3.25 inch ID, +/- 8 inch OD 40 Datum Hammer Weight/Drop Sampler Type (ST): ~425 5 HB-1 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name Water Level ()Approved by: 30 Blows/Foot SamplesDepth (ft)S T Exploration Number20000669E005 9/11/21,9/11/21 Logged by: Shelby Tube Sample 140# / 30Hand Auger Exploration Boring Water Level at time of drilling (ATD) Lindbergh High School Additions M - Moisture Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet1 of 1 NAVD 88 WellAESIBOR 20000669E005.GPJ September 27, 2021 Landscaping Mulch - 4 to 6 inches Fill Loose, moist, light brown, fine SAND, some silt, some gravel, somemedium to coarse sand; unsorted (SP-SM). Loose, moist, light brown, fine SAND, some silt, some gravel, somemedium to coarse sand; metal debris; unsorted (SP-SM). S-1 S-2 Bottom of exploration boring at 2.5 feetNo groundwater encountered. Ground Surface Elevation (ft) Grab SampleSymbol 3.25 inch ID, +/- 8 inch OD 40 Datum Hammer Weight/Drop Sampler Type (ST): ~397.5 5 HB-2 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name Water Level ()Approved by: 30 Blows/Foot SamplesDepth (ft)S T Exploration Number20000669E005 9/11/21,9/11/21 Logged by: Shelby Tube Sample 140# / 30Hand Auger Exploration Boring Water Level at time of drilling (ATD) Lindbergh High School Additions M - Moisture Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet1 of 1 NAVD 88 WellAESIBOR 20000669E005.GPJ September 27, 2021 Kirkland | Tacoma | Mount Vernon 425-827-7701 | www.aesgeo.com January 3, 2022 Project No. 20000669E005 Renton School District No. 403 7812 South 124th Street Seattle, Washington 98178 Attention: Mr. Stewart Shusterman Subject: Subsurface Exploration and Limited Geotechnical Engineering Study Lindbergh High School Southwestern Parking Lot Paving Repair 16426 128th Avenue SE Renton, Washington Dear Mr. Shusterman: As requested, Associated Earth Sciences, Inc. (AESI) is pleased to provide this letter-report summarizing observed surface and subsurface conditions, and presenting our geotechnical recommendations for repair of existing parking lot paving. Our recommendations are based on available topographic and geologic data, completion of three subsurface exploration borings, and our experience working on previously completed projects onsite. Authorization to proceed with this study was given to AESI by means of District Purchase Order 202100033 dated November 30, 2021. Our study was accomplished in general accordance with our proposal, dated November 15, 2021. This letter-report has been prepared for the exclusive use of the Renton School District and its agents, for specific application to this project. Within the limitations of scope, schedule, and budget, our services have been performed in accordance with generally accepted geotechnical engineering and engineering geology practices in effect in this area at the time our letter-report was prepared. No other warranty, express or implied, is made. Our observations, findings, and opinions are a means to identify and reduce the inherent risks to the owner. Site and Project Description The project site is that of the Lindbergh High School campus (Figure 1). The proposed project will include repairing existing paving in the southwestern parking lot west of the pool building. The existing parking lot paving has areas of tree root damage, polygonal “alligator” cracking, Lindbergh High School Southwestern Parking Lot Paving Repair Subsurface Exploration and Limited Renton, Washington Geotechnical Engineering Study January 3, 2022 ASSOCIATED EARTH SCIENCES, INC. BWG/ld - 20000669E005-005 Page 2 and linear cracking. The existing parking area is relatively flat and was graded to the existing configuration during previous earthwork at the time it was constructed. Topography of the project vicinity is characterized by an upland plateau with gentle to moderate slopes. AESI has previously provided geotechnical engineering for fourteen projects onsite. Two of the previous studies (2010 and 2017) included subsurface exploration borings in the current project area. Previously completed borings in the current project area encountered surficial existing fill underlain by very dense lodgement till. Review of Previous AESI Studies The two previous on-site AESI studies relevant to the current project include: •“Underground Injection Control Well Feasibility Assessment - Lindbergh High School Improvements,” AESI Project Number KE090426A, dated July 22, 2010. •“Limited Pavement Remediation Recommendations - Lindbergh High School Bus Loop, AESI Project Number 20170046E001, dated June 6, 2017. The referenced reports contain subsurface explorations in the current project area that encountered existing fill underlain by very dense native lodgement till sediments. The fill was observed to be thickest in explorations EB-102 (>6.5 feet) and EB-104 (5 feet) which were located north and south of the parking lot along the access road. The fill in EB-102 and EB-104 was described as medium dense to dense, moist to very moist, silty, fine sand with small amounts of organic inclusions in the upper section of EB-102. Fill soils were also observed in EB-6 (3 feet). The fill in EB-6 was described as a dense, moist, silty, fine sand with organics and woody debris in the upper 4 inches. Fill was only encountered in the above three borings. In the remainder of the borings, underlying the asphalt and gravel base, we observed very dense, silty, fine sand, with variable gravel content which was interpreted to be Vashon lodgement till sediments. The asphalt thicknesses in the explorations ranged between 1 and 3 inches. Subsurface exploration logs from the two previous studies referenced above were relied on in preparation of our recommendations and are included in this letter-report. Exploration locations are shown on the “Site and Exploration Plan,” Figure 2, and exploration logs are included in the attachments. This letter-report only includes selected explorations from the referenced reports that fall within the current project area. We can provide additional historical information on request. Site Exploration Our field investigations for the current study were conducted on December 3, 2021. It included advancing three shallow exploration borings using hand tools. The locations of subsurface explorations referenced in this study are presented relative to existing site features on Figure 2. Lindbergh High School Southwestern Parking Lot Paving Repair Subsurface Exploration and Limited Renton, Washington Geotechnical Engineering Study January 3, 2022 ASSOCIATED EARTH SCIENCES, INC. BWG/ld - 20000669E005-005 Page 3 The various types of sediments, as well as the depths where the characteristics of the sediments changed, are indicated on the exploration logs presented in the attachments. Our explorations were approximately located in the field by measuring from known site features depicted on the aerial photograph used as a basis for Figure 2. The conclusions and recommendations presented in this letter-report are based, in part, on the explorations completed for this study. The number, locations, and depths of the explorations were completed within site and budgetary constraints. Because of the nature of exploratory work below ground, extrapolation of subsurface conditions between field explorations is necessary. It should be noted that differing subsurface conditions may be present due to the random nature of deposition and the alteration of topography by past grading and/or filling. The nature and extent of variations between the field explorations may not become fully evident until construction. If variations are observed at that time, it may be necessary to re-evaluate specific recommendations in this letter-report and make appropriate changes. Exploration Hand Borings For this study, the three explorations were completed by using a 4-inch-diameter hand auger, posthole digger, and digging bar (HB-1, HB-2, and HB-3). Prior to advancing the exploration borings, the asphalt was cored in each location, using a subcontracted firm (Seattle Concrete Core Drilling). The exploration borings allowed direct observation of in situ subsurface conditions. The exploration borings were continuously observed and logged by a geologist from our firm. The exploration logs presented in the attachments are based on the field logs, digging action, and visual observation of the samples collected. Each boring was advanced until refusal was met, which ranged between 2.5 and 4 feet below existing ground surface. Once completed, the explorations were backfilled with soil generated from the explorations and a Portland cement patch flush with adjacent paving. The samples obtained from exploration borings were classified in the field and representative portions placed in watertight containers. The samples were then transported to our laboratory for further visual classification. Laboratory testing results are presented in the attachments. Subsurface Conditions Regional Geology and Soils Mapping Review of the regional geologic map, Geologic Map of the Renton Quadrangle, King County, Washington, scale 1:24,000, U.S. Geological Survey, D.R. Mullineaux, Geologic Quadrangle Map-GQ-405, 1965, shows that the subject site is mapped as Vashon-aged lodgement till. Lodgement till is typically well suited to structural support with proper preparation. Lodgement till typically comprises a very dense, unsorted mixture of silts, sands, gravels, cobbles, and boulders, all deposited and consolidated by the weight of the advancing glacier. The reviewed mapped geology was consistent with our subsurface soil observations. Lindbergh High School Southwestern Parking Lot Paving Repair Subsurface Exploration and Limited Renton, Washington Geotechnical Engineering Study January 3, 2022 ASSOCIATED EARTH SCIENCES, INC. BWG/ld - 20000669E005-005 Page 4 Site Stratigraphy Subsurface conditions at the project site were inferred from the field explorations accomplished for this study, visual reconnaissance of the site, and review of selected applicable geologic literature. As shown on the exploration logs, soils encountered at the subject site were overlain by asphalt paving and a gravel base of varying thicknesses. The underlying soils consisted of previously placed fill soils and Vashon-aged lodgement till sediments. The following sections present more detailed subsurface information on the sediment types encountered at the site. Asphalt and Gravel Base In each exploration completed we observed sections of asphalt with an underlying gravel base course. The asphalt in each exploration ranged in thickness from 2.5 inches (HB-1), 1.75 inches (HB-2), and 2.25 inches (HB-3). The asphalt cores came out intact and were observed to be originally placed in one lift. The crushed gravel base courses in each exploration varied in thickness and gradation. In HB-1 we observed a relatively loose, 2.5-inch base course section consisting almost entirely of crushed, clean, 1¼-inch aggregate. In HB-2, we observed a dense, 2-inch base course section consisting of crushed aggregate with a fine to medium sand matrix and trace silt. In HB-3, we observed a dense, 4.75-inch base course section consisting of fine to medium sand, with some crushed aggregate and trace silt, resembling 5/8-inch minus. Observed paving and base course thicknesses at exploration locations are reported on exploration logs included in the attachments. Fill Fill soils (those not naturally placed) were encountered in two of our current explorations (HB-1 and HB-3) with observed thicknesses of 1.5 and 1.8 feet below existing ground surface, respectively. Three of the previously completed explorations included in the attachments to this letter-report encountered existing fill, the thickest at EB-102 where the depth of fill exceeded the boring depth of 6.5 feet. The fill generally consisted of loose to dense silty sand and gravel. Dark brown silty inclusions and shredded wood debris was observed in some of the recovered samples of existing fill. Existing fill may require visual assessment and remedial preparation below new paving in any location where paving will be constructed directly on top of subgrade soils. Excavated existing fill material is suitable for reuse in structural fill applications if such reuse is specifically allowed by project plans and specifications, if excessively organic and any other deleterious materials are removed, and if moisture content is adjusted to allow compaction to the specified level and to a firm and unyielding condition. Existing fill is not suitable for use as an infiltration receptor for stormwater. Lindbergh High School Southwestern Parking Lot Paving Repair Subsurface Exploration and Limited Renton, Washington Geotechnical Engineering Study January 3, 2022 ASSOCIATED EARTH SCIENCES, INC. BWG/ld - 20000669E005-005 Page 5 Vashon Lodgement Till In all of our exploration borings in the current project area except EB-102, we observed dense to very dense, unsorted, silty fine sand with varying amounts of gravel and cobbles interpreted to represent lodgement till sediments. The lodgement till was deposited directly from basal, debris-laden glacial ice during the Vashon Stade of the Fraser Glaciation approximately 12,500 to 15,000 years ago. The high relative density of the unweathered till is due to its consolidation by the massive weight of the glacial ice from which it was deposited. Consequently, these materials are dense to very dense, possess high-strength and low- compressibility characteristics, and are relatively impermeable. The lodgement till is suitable for support of new and overlay paving with proper preparation. Excavated lodgement till is suitable for use in structural fill applications provided that the moisture content is adjusted to allow compaction to a firm and unyielding condition at the specified level. The lodgement till has a large proportion of fine-grained material making it susceptible to disturbance when wet. Lodgement till is not a suitable infiltration receptor. Hydrology Moderate groundwater seepage was encountered in our previous exploration borings EB-101 and EB-104, directly below the asphalt (March 2017). Moderate groundwater seepage was also observed in one of our most recent explorations HB-3, directly below the asphalt (December 2021). It is our opinion that the groundwater observed was perched. Perched water occurs when surface water infiltrates down through relatively permeable soils, such as gravel base courses, existing fill, or coarser-grained lodgement till strata and becomes trapped or “perched” atop a comparatively low-permeability barrier, such as siltier zones within the lodgement till. When water becomes perched it may travel laterally. The presence and quantity of groundwater will largely depend on the soil grain-size distribution, topography, seasonal precipitation, site use, on- and off-site land usage, and other factors. Perched groundwater directly under asphalt can contribute to cracking and settlement failures such as observed inside the project area. Critical Areas - Geologic Hazards City of Renton Municipal Code section 4-3-050E, MAPS, 4, defines regulated critical areas as those designated on City of Renton maps (COR Maps). The COR Maps were reviewed at https://www.rentonwa.gov/city_hall/executive_services/Information_technology/maps___g_i _s_data and no geotechnical critical areas are mapped in or adjacent to the current project limits. Although no mapped erosion hazards were identified, the project plans should include implementation of temporary erosion controls in accordance with the City of Renton’s standards of practice. Control methods should include limiting earthwork to seasonally drier periods if possible, use of perimeter silt fences, stabilized construction entrances, and straw Lindbergh High School Southwestern Parking Lot Paving Repair Subsurface Exploration and Limited Renton, Washington Geotechnical Engineering Study January 3, 2022 ASSOCIATED EARTH SCIENCES, INC. BWG/ld - 20000669E005-005 Page 6 mulch in exposed areas. Removal of existing vegetation should be limited to those areas that are required to construct the project, and new landscaping and vegetation with equivalent erosion mitigation potential should be established as soon as practical after grading is complete. During construction, surface water should be collected as close as possible to the source to minimize silt entrainment that could require treatment or detention prior to discharge. Timely implementation of permanent drainage control measures should also be a part of the project plans and will help reduce erosion and generation of silty surface water onsite. Conclusions The existing parking lot paving is in fair to poor condition, with areas of tree root damage, polygonal cracking, and linear cracking. Tree damage appears to be affected by the presence of dense lodgement till soils at shallow depths, which encourages shallower root zones within the surficial fill. Poor drainage of the native lodgement till sediments and shallow perched seepage zones appear to be strong contributors to areas of polygonal cracking. Linear cracking in a passenger car parking lot is likely to be related to age, thermal effects, and to a lesser extent by poor drainage in the paving base course. Tree Damage Areas In general, tree root damage is best repaired by removal of the affected paving, removal and sterilization of the roots causing the problem, and constructing a new paving section to match the existing adjacent area. Polygonal Cracking Areas Polygonal cracking related to poor subsurface drainage is difficult to cure effectively without full reconstruction of the paving that incorporates cutoff drains at the pavement edge. For renovation of existing paving, we recommend placement of an asphalt-impregnated geotextile such as Petromat 4597 that is selectively applied over cracked areas to be treated, followed by an asphalt overlay. Glasgrid 8511 may also be used in the same manner and provides substantial tensile strength in addition to crack sealing. We are available to discuss equivalent alternative pavement overlay geotextiles on request. Linear Cracking Areas Areas of linear cracking could be treated with an asphalt-impregnated geotextile as recommended above for areas of polygonal cracking, or manual crack sealing in preparation for an asphalt overlay. Lindbergh High School Southwestern Parking Lot Paving Repair Subsurface Exploration and Limited Renton, Washington Geotechnical Engineering Study January 3, 2022 ASSOCIATED EARTH SCIENCES, INC. BWG/ld - 20000669E005-005 Page 7 General Procedure - Remove and Replace Remove existing paving, assess and repair subgrade soils as needed, and repave. We recommend that the distressed portions of the existing pavement be proof-rolled with a loaded dump truck to observe the degree of yielding and help define the limits of paving replacement. Should pavement yielding be observed, the underlying subgrade soils can be removed and replaced with crushed surfacing base course or gravel borrow compacted to 95 percent of the maximum density, as determined by ASTM D-1557. All paving materials should meet gradation criteria contained in the current Washington State Department of Transportation (WSDOT) Standard Specifications. General Procedure - Grind and Overlay In areas of minor deterioration, we recommend that the pavement surface be cold planed (ground) and provided with a new asphalt overlay. Pavement planing is not recommended in areas of significant polygonal cracking. We recommend a minimum depth of cold planing of 1 inch, and a minimum thickness of new asphalt overlay of 2 inches. The total combined thickness of the new asphalt and existing asphalt should be 3 inches in areas of planned passenger car driving and parking, and 4 inches of asphalt in drive areas subjected to heavier loads. General Procedure - Geotextile and Overlay Geotextiles are particularly effective at sealing areas of pervasive polygonal cracking in preparation for an overlay. If subgrade instability is present or suspected, a geotextile should be selected with tensile strength to reduce the potential for future reflective cracking. Asphalt-impregnated geotextiles have manufacturer-recommended installation procedures that are product-specific. We are available to assist in selection, specification, and submittal approval of pavement repair geotextiles on request. Project Design and Construction Monitoring We recommend that AESI perform a geotechnical review of the plans prior to final design completion. In this way, we can confirm that our recommendations have been correctly interpreted and implemented in the design. The City of Renton may require a plan review by the geotechnical engineer as a condition of permitting. We recommend that AESI be retained to provide geotechnical special inspections during construction, and preparation of a final summary letter when construction is complete. The City of Renton may require such geotechnical special inspections. The integrity of the proposed improvements depend on proper site preparation and construction procedures. In addition, engineering decisions may have to be made in the field in the event that variations in subsurface conditions become apparent. Lindbergh High School Southwestern Parking Lot Paving Repair Subsurface Exploration and Limited Renton, Washington Geotechnical Engineering Study January 3, 2022 ASSOCIATED EARTH SCIENCES, INC. BWG/ld - 20000669E005-005 Page 8 We have enjoyed working with you on this study and are confident these recommendations will aid in the successful completion of your project. If you should have any questions or require further assistance, please do not hesitate to call. Sincerely, ASSOCIATED EARTH SCIENCES, INC. Kirkland, Washington Bruce W. Guenzler, L.E.G. Kurt D. Merriman, P.E. Senior Associate Geologist Senior Principal Engineer Attachments: Figure 1. Vicinity Map Figure 2. Site and Exploration Plan Exploration Logs Laboratory Testing Results KING COUNTY KING COUNTY RENTON PROJ NO. NOTE: BLACK AND WHITE REPRODUCTION OF THIS COLORORIGINAL MAY REDUCE ITSEFFECTIVENESS AND LEAD TOINCORRECT INTERPRETATION DATE:FIGURE: ±\\kirkfile2\GIS\GIS_Projects\aY00post0716\000669 Lindbergh HS\aprx\20000669E005 F1 VM_Lindbergh.aprx | 20000669E005 F1 VM_Lindbergh | 12/8/2021 9:38 AMDATA SOURCES / REFERENCES: USGS: 7.5' SERIES TOPOGRAPHIC MAPS, ESRI/I-CUBED/NGS 2013 KING CO: STREETS, CITY LIMITS, PARCELS, PARKS 3/20 LOCATIONS AND DISTANCES SHOWN ARE APPROXIMATE 0 2000 Feet VICINITY MAP LINDBERGH HS IMPROVEMENTS RENTON, WASHINGTON 20000669E005 12/21 1 King County ¥ ¥ ¥ ¬« ¬«169 !( SITE King County !( !( !( !(!( !(!( !( !( !( !(!( 430 420 41 0 400 440430 4 0 0 128th Ave SEEB-6 EB-7 EB-101 EB-102EB-103 EB-104 EB-105 EB-106 EB-107 HB-3 HB-4 HB-5 EagleView Technologies, Inc. ± BLACK AND WHITE REPRODUCTION OF THIS COLOR ORIGINAL MAY REDUCE ITSEFFECTIVENESS AND LEAD TO INCORRECT INTERPRETATION \\kirkfile2\GIS\GIS_Projects\aY00post0716\000669 Lindbergh HS\aprx\20000669E005 F2 ES_Lindbergh_1221.aprx | 20000669E005 F2 ES_Lindbergh_1221 | 12/8/2021 4:24 PMPROJ NO.DATE:FIGURE: 0 80 FEET NOTE: HISTORICAL EXPLORATIOS OUTSIDE THE CURRENT WORK AREA ARE NOT SHOWN ON THE FIGURE AND NOTINCLUDED IN THE APPENDIX DATA SOURCES / REFERENCES:PSLC: KING COUNTY 2016, GRID CELL SIZE IS 3'.DELIVERY 1 FLOWN 2/24/16 - 3/28/16 CONTOURS FROM LIDAR KING CO: STREETS, PARCELS, 3/20 AERIAL PICTOMETRY INT. 2019 LOCATIONS AND DISTANCES SHOWN ARE APPROXIMATE 20000669E005 12/21 2 EXISTING SITE AND EXPLORATION PLAN LINDBERGH HS ADDITIONS RENTON, WASHINGTON LEGEND SITE !(HAND BORING, 2021 !(EXPLORATION BORING, 2017 !(EXPLORATION BORING, 2009 PARCEL CONTOUR 10 FT CONTOUR 2 FT Asphalt - 2 inches Vashon Lodgement Till Very dense, moist, light gray-brown, silty, fine SAND, trace gravel;unsorted; some oxidation (SM). Very dense, moist, light gray-brown, silty, fine SAND, trace gravel;unsorted; no oxidation (SM). As above. 62141 3350/4" 3850/3" S-1 S-2 S-3 Bottom of exploration boring at 6 feetModerate seepage below asphalt layer. No visible seepage in native soils. 1 of 1 N/A Sheet Depth (ft)Exploration Number170046E001 M - Moisture 6 inches 40 Datum S T Graphic10 Other TestsHole Diameter (in) DESCRIPTION Location Water Level ()Approved by: 30 Blows/Foot Driller/Equipment Blows/6"Boretec / Mini-Track Well5 10 15 Water LevelProject Name EB-101 SymbolTAG2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)JHSCompletionSamples Ground Surface Elevation (ft) Grab Sample 3/30/17,3/30/17 Logged by: Shelby Tube Sample 140# / 30" Ring Sample No Recovery Water Level at time of drilling (ATD) Lindbergh HS Project Number 20 Renton, WA Date Start/Finish Hammer Weight/Drop Sampler Type (ST): Exploration Log AESIBOR 170046.GPJ April 20, 201762 5050/4" 5050/3" Asphalt - 3 inches Fill Very dense, moist, light gray-brown, very silty, fine SAND, trace gravel;dark brown inclusion (SM). Dense, moist, light gray-brown, very silty, fine SAND, trace gravel (SM). 2550/6" 342219 S-1 S-2 Bottom of exploration boring at 6.5 feetNo visible seepage. 1 of 1 N/A Sheet Depth (ft)Exploration Number170046E001 M - Moisture 6 inches 40 Datum S T Graphic10 Other TestsHole Diameter (in) DESCRIPTION Location Water Level ()Approved by: 30 Blows/Foot Driller/Equipment Blows/6"Boretec / Mini-Track Well5 10 15 Water LevelProject Name EB-102 SymbolTAG2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)JHSCompletionSamples Ground Surface Elevation (ft) Grab Sample 3/30/17,3/30/17 Logged by: Shelby Tube Sample 140# / 30" Ring Sample No Recovery Water Level at time of drilling (ATD) Lindbergh HS Project Number 20 Renton, WA Date Start/Finish Hammer Weight/Drop Sampler Type (ST): Exploration Log AESIBOR 170046.GPJ April 20, 20175050/6" 4141 Asphalt - 3 inches Vashon Lodgement Till Dense, moist, light gray-brown, very silty, fine SAND, trace gravel;unsorted; some oxidation; low recovery (SM). Very dense, moist, light gray-brown, very silty, fine SAND, trace gravel;unsorted; no oxidation; low recovery (SM). 162225 3450/5" S-1 S-2 Bottom of exploration boring at 6 feetNo visible seepage. 1 of 1 N/A Sheet Depth (ft)Exploration Number170046E001 M - Moisture 6 inches 40 Datum S T Graphic10 Other TestsHole Diameter (in) DESCRIPTION Location Water Level ()Approved by: 30 Blows/Foot Driller/Equipment Blows/6"Boretec / Mini-Track Well5 10 15 Water LevelProject Name EB-103 SymbolTAG2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)JHSCompletionSamples Ground Surface Elevation (ft) Grab Sample 3/30/17,3/30/17 Logged by: Shelby Tube Sample 140# / 30" Ring Sample No Recovery Water Level at time of drilling (ATD) Lindbergh HS Project Number 20 Renton, WA Date Start/Finish Hammer Weight/Drop Sampler Type (ST): Exploration Log AESIBOR 170046.GPJ April 20, 20174747 5050/5" Asphalt - 1 inch Fill Medium dense, very moist, light gray-brown, silty, fine to medium SAND,trace gravel (SM). Vashon Lodgement Till Very dense, moist, light gray-brown, very silty, fine SAND, trace gravel;unsorted; some oxidation (SM). 13109 142830 S-1 S-2 Bottom of exploration boring at 6.5 feetModerate seepage from 3 feet to bottom of boring. 1 of 1 N/A Sheet Depth (ft)Exploration Number170046E001 M - Moisture 6 inches 40 Datum S T Graphic10 Other TestsHole Diameter (in) DESCRIPTION Location Water Level ()Approved by: 30 Blows/Foot Driller/Equipment Blows/6"Boretec / Mini-Track Well5 10 15 Water LevelProject Name EB-104 SymbolTAG2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)JHSCompletionSamples Ground Surface Elevation (ft) Grab Sample 3/30/17,3/30/17 Logged by: Shelby Tube Sample 140# / 30" Ring Sample No Recovery Water Level at time of drilling (ATD) Lindbergh HS Project Number 20 Renton, WA Date Start/Finish Hammer Weight/Drop Sampler Type (ST): Exploration Log AESIBOR 170046.GPJ April 20, 20171919 68 Asphalt - 2 inches Vashon Lodgement Till Very dense, moist, light gray-brown, very silty, fine SAND, trace gravel;unsorted; some oxidation (SM). Very dense, moist, light gray-brown, very silty, fine SAND, trace gravel;unsorted, no oxidation; low recovery (SM). As above. 72231 50/5" 3550/5" S-1 S-2 S-3 Bottom of exploration boring at 6 feetNo visible seepage. 1 of 1 N/A Sheet Depth (ft)Exploration Number170046E001 M - Moisture 6 inches 40 Datum S T Graphic10 Other TestsHole Diameter (in) DESCRIPTION Location Water Level ()Approved by: 30 Blows/Foot Driller/Equipment Blows/6"Boretec / Mini-Track Well5 10 15 Water LevelProject Name EB-105 SymbolTAG2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)JHSCompletionSamples Ground Surface Elevation (ft) Grab Sample 3/30/17,3/30/17 Logged by: Shelby Tube Sample 140# / 30" Ring Sample No Recovery Water Level at time of drilling (ATD) Lindbergh HS Project Number 20 Renton, WA Date Start/Finish Hammer Weight/Drop Sampler Type (ST): Exploration Log AESIBOR 170046.GPJ April 20, 201753 5050/5" 5050/5" Asphalt - 2 inches Vashon Lodgement Till Very dense, moist, light gray-brown, very silty, fine SAND, trace gravel;unsorted (SM). As above. As above. 122232 3050/4" 163350/6" S-1 S-2 S-3 Bottom of exploration boring at 6.5 feetNo visible seepage. 1 of 1 N/A Sheet Depth (ft)Exploration Number170046E001 M - Moisture 6 inches 40 Datum S T Graphic10 Other TestsHole Diameter (in) DESCRIPTION Location Water Level ()Approved by: 30 Blows/Foot Driller/Equipment Blows/6"Boretec / Mini-Track Well5 10 15 Water LevelProject Name EB-106 SymbolTAG2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)JHSCompletionSamples Ground Surface Elevation (ft) Grab Sample 3/30/17,3/30/17 Logged by: Shelby Tube Sample 140# / 30" Ring Sample No Recovery Water Level at time of drilling (ATD) Lindbergh HS Project Number 20 Renton, WA Date Start/Finish Hammer Weight/Drop Sampler Type (ST): Exploration Log AESIBOR 170046.GPJ April 20, 201754 5050/4" 83 Asphalt - 2 inches Vashon Lodgement Till Very dense, moist, light gray-brown, very silty, fine SAND, trace gravel;unsorted (SM). As above. 192631 3950/5" S-1 S-2 Bottom of exploration boring at 6 feetNo visible seepage. 1 of 1 N/A Sheet Depth (ft)Exploration Number170046E001 M - Moisture 6 inches 40 Datum S T Graphic10 Other TestsHole Diameter (in) DESCRIPTION Location Water Level ()Approved by: 30 Blows/Foot Driller/Equipment Blows/6"Boretec / Mini-Track Well5 10 15 Water LevelProject Name EB-107 SymbolTAG2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)JHSCompletionSamples Ground Surface Elevation (ft) Grab Sample 3/30/17,3/30/17 Logged by: Shelby Tube Sample 140# / 30" Ring Sample No Recovery Water Level at time of drilling (ATD) Lindbergh HS Project Number 20 Renton, WA Date Start/Finish Hammer Weight/Drop Sampler Type (ST): Exploration Log AESIBOR 170046.GPJ April 20, 201757 5050/5" Asphalt - 2.5 inches Gravel Base Course Clean, angular, 1/4-inch base course aggregate (GP). Fill Loose, moist, dark brown, silty, fine to medium SAND, some gravel;unsorted; contains organics (SM). Loose, moist, light brown, silty, fine SAND, some gravel; contains woodydebris (3 inch diameter); unsorted (SM). Vashon Lodgement Till Very dense, moist, brownish gray, silty, fine SAND, some gravel; unsorted;digs up in clasts (SM). S-1 S-2 S-3 S-4 Bottom of exploration boring at 4 feetNo groundwater encountered. Ground Surface Elevation (ft) Grab SampleSymbol 5 40 Datum Hammer Weight/Drop Sampler Type (ST): ~434 5 HB-3 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name Water Level ()Approved by: 30 Blows/Foot SamplesDepth (ft)S T Exploration Number20000669E005 12/3/21,12/3/21 Logged by: Shelby Tube Sample Hand Auger Exploration Boring Water Level at time of drilling (ATD) Lindbergh High School Additions M - Moisture Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet1 of 1 NAVD 88 WellAESIBOR 20000669E005.GPJ December 30, 2021 Asphalt - 1.75 inches Gravel Base CourseDense, moist, grayish brown, fine to medium sandy, GRAVEL, some silt;unsorted; gravel is angular (GP-GM). Vashon Lodgement TillVery dense, moist, brownish gray, silty, fine SAND, some gravel; unsorted;digs up in clasts (SM). Iron oxide mottling 0 to 1 foot. S-1 S-2 Bottom of exploration boring at 2.5 feetNo groundwater encountered. Refusal due to large cobble. Ground Surface Elevation (ft) Grab SampleSymbol 5 40 Datum Hammer Weight/Drop Sampler Type (ST): ~432 5 HB-4 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name Water Level ()Approved by: 30 Blows/Foot SamplesDepth (ft)S T Exploration Number20000669E005 12/3/21,12/3/21 Logged by: Shelby Tube Sample Hand Auger Exploration Boring Water Level at time of drilling (ATD) Lindbergh High School Additions M - Moisture Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet1 of 1 NAVD 88 WellAESIBOR 20000669E005.GPJ December 30, 2021 Asphalt - 2.25 inches Base Course Dense, moist to wet, grayish brown, fine to medium gravelly, SAND, somecoarse sand, trace silt; unsorted (SP). Fill Loose, moist, dark brown, silty, fine SAND, some gravel, trace cobbles;contains shredded wood debris; unsorted (SM). Vashon Lodgement Till Very dense, moist, gray, silty, fine SAND to fine sandy, SILT, some gravel;occasional cobbles; unsorted (SM). S-1 S-2 S-3 Bottom of exploration boring at 3 feetSlow groundwater seepage ~3 to 6 inches. Refusal due to large cobbles. Ground Surface Elevation (ft) Grab SampleSymbol 5 40 Datum Hammer Weight/Drop Sampler Type (ST): ~430 5 HB-5 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"JHS ART2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name Water Level ()Approved by: 30 Blows/Foot SamplesDepth (ft)S T Exploration Number20000669E005 12/3/21,12/3/21 Logged by: Shelby Tube Sample Hand Auger Exploration Boring Water Level at time of drilling (ATD) Lindbergh High School Additions M - Moisture Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet1 of 1 NAVD 88 WellAESIBOR 20000669E005.GPJ December 30, 2021 Particle Size Distribution Report PERCENT FINER0 10 20 30 40 50 60 70 80 90 100 GRAIN SIZE - mm. 0.0010.010.1110100 % +3"Coarse % Gravel Fine Coarse Medium % Sand Fine Silt % Fines Clay 0.0 0.0 22.7 9.0 15.4 27.7 25.26 in.3 in.2 in.1½ in.1 in.¾ in.½ in.3/8 in.#4#10#20#30#40#60#100#140#200TEST RESULTS Opening Percent Spec.*Pass? Size Finer (Percent) (X=Fail) Material Description Atterberg Limits (ASTM D 4318) Classification Coefficients Date Received:Date Tested: Tested By: Checked By: Title: Date Sampled:Location: Onsite - Fill Sample Number: HB-5 Depth: 1' Client: Project: Project No:Figure gravelly, silty SAND 1" 3/4" 5/8" 1/2" 3/8" #4 #8 #10 #20 #40 #60 #100 #200 100.0 100.0 97.7 93.5 85.6 77.3 69.8 68.3 60.8 52.9 43.8 34.8 25.2 NP NV SM A-2-4(0) 11.1732 9.2723 0.7830 0.3531 0.1083 12/9/2021 12/13/2021 CI ART/BG 12/3/2021 Renton School District No. 403 Lindbergh HS Improvements 20000669 E005 PL=LL=PI= USCS (D 2487)=AASHTO (M 145)= D90=D85=D60= D50=D30=D15= D10=Cu=Cc= Remarks *(no specification provided) Particle Size Distribution Report PERCENT FINER0 10 20 30 40 50 60 70 80 90 100 GRAIN SIZE - mm. 0.0010.010.1110100 % +3"Coarse % Gravel Fine Coarse Medium % Sand Fine Silt % Fines Clay 0.0 9.0 20.2 6.8 15.5 26.9 21.66 in.3 in.2 in.1½ in.1 in.¾ in.½ in.3/8 in.#4#10#20#30#40#60#100#140#200TEST RESULTS Opening Percent Spec.*Pass? Size Finer (Percent)(X=Fail) Material Description Atterberg Limits (ASTM D 4318) Classification Coefficients Date Received:Date Tested: Tested By: Checked By: Title: Date Sampled:Location: Onsite - Till Sample Number: HB-4 Depth: 2' Client: Project: Project No:Figure gravelly, silty SAND 1.5" 1" 3/4" 5/8" 1/2" 3/8" #4 #8 #10 #20 #40 #60 #100 #200 100.0 94.5 91.0 82.3 81.1 78.4 70.8 65.1 64.0 58.0 48.5 37.3 29.0 21.6 NP NV SM A-1-b 18.6381 16.9262 1.0891 0.4616 0.1613 12/9/2021 12/13/2021 CI ART/BG 12/3/2021 Renton School District No. 403 Lindbergh HS Improvements 20000669 E005 PL=LL=PI= USCS (D 2487)=AASHTO (M 145)= D90=D85=D60= D50=D30=D15= D10=Cu=Cc= Remarks *(no specification provided) Particle Size Distribution Report PERCENT FINER0 10 20 30 40 50 60 70 80 90 100 GRAIN SIZE - mm. 0.0010.010.1110100 % +3"Coarse % Gravel Fine Coarse Medium % Sand Fine Silt % Fines Clay 0.0 8.3 10.4 6.3 15.4 26.9 32.76 in.3 in.2 in.1½ in.1 in.¾ in.½ in.3/8 in.#4#10#20#30#40#60#100#140#200TEST RESULTS Opening Percent Spec.*Pass? Size Finer (Percent)(X=Fail) Material Description Atterberg Limits (ASTM D 4318) Classification Coefficients Date Received:Date Tested: Tested By: Checked By: Title: Date Sampled:Location: Onsite - Till Sample Number: HB-5 Depth: 2.5' Client: Project: Project No:Figure gravelly, very silty SAND 1.5" 1" 3/4" 5/8" 1/2" 3/8" #4 #8 #10 #20 #40 #60 #100 #200 100.0 94.1 91.7 91.7 90.8 87.5 81.3 76.2 75.0 68.9 59.6 48.4 40.0 32.7 NP NV SM A-2-4(0) 11.6794 7.5175 0.4349 0.2707 12/9/2021 12/13/2021 CI ART/BG 12/3/2021 Renton School District No. 403 Lindbergh HS Improvements 20000669 E005 PL=LL=PI= USCS (D 2487)=AASHTO (M 145)= D90=D85=D60= D50=D30=D15= D10=Cu=Cc= Remarks *(no specification provided) APPENDIX F Facility Summaries and Declaration of Drainage Covenant 2016 KING COUNTY SURFACE WATER DESIGN MANUAL, REFERENCE D 4/24/2016Page 1STORMWATER FACILITY SUMMARY SHEET DPER Permit No.___________________(provide one Stormwater Facility Summary Sheet per Natural Discharge Location)Date ___________________OVERVIEW:NPDES Permit No.___________________Project NameParcel No.____________________________Project LocationRetired Parcel No.____________________________Downstream Drainage Basins:Project includes Landscape Management Plan?yes Major Basin Name ______________________________________________(include copy with TIR as Appendix)no Immediate Basin Name ______________________________________________GENERAL FACILITY INFORMATION: Leachable MetalsInfiltration Impervious Surface LimitType # of Type # of Type# of facilities Flow Control BMPsPonds______ Ponds ______ Ponds ______ Basic Clearing LimitVaults______ Tanks ______ Vaults ______ Conservation Drainage FacilityTanks______ Trenches _____ Tanks ______ Flood Problem Landscape Management PlanIf no flow control facility, check one: Project qualifies for KCSWDM Exemption (KCSWDM 1.2.3): Basic Exemption (Applies to Commercial parcels only)Area % of Total  Redevelopment projects Cost Exemption for Parcel Redevelopment projects Direct Discharge Exemption Other _____________________ Total impervious surface served by Project qualifies for 0.1 cfs Exception per KCSWDM 1.2.3 flow control facility(ies) (sq ft)  Impervious surface served by flow KCSWDM Adjustment No. ___________________ control facility(ies) designed 1990 or later (sq ft) approved KCSWDM Adjustment No. __________________ Impervious surface served by Shared Facility Name/Location: _________________________ pervious surface absorption (sq ft) No flow control required (other, provide justification): Impervious surface served by approved ____________________________________________________ water quality facility(ies) (sq ft)Flow ControlPerformance StdDeclarations of CovenantRecording No.Water QualityDetentionTREATMENT SUMMARY FOR TOTAL IMPERVIOUS SURFACES ----- Total Impervious Acreage (ac)No flow control required per approvedFlow control provided in regional/shared facility per approved PROVIDE FACILITY DETAILS AND FACILITY SKETCH FOR EACH FACILITY ON REVERSE. USE ADDITIONAL SHEETS AS NEEDED FOR ADDITIONAL FACILITIESImpervious Surface Exemption for Transportation Total Acreage (ac)Lindbergh HS Modernization and Additions16426 128th Avenue SE, Renton, WA 98058Lower Cedar RiverMolasses creek (South TDA)18TBDTBDTBD1.901.41740.0210.0210.52272823059004, 2823059042, 2823059093 2016 KING COUNTY SURFACE WATER DESIGN MANUAL, REFERENCE D 4/24/2016Page 2STORMWATER FACILITY SUMMARY SHEET DPER Permit No.___________________(provide one Stormwater Facility Summary Sheet per Natural Discharge Location)Project Name Downstream Drainage Basins:Major Basin Name _______________________________Project LocationImmediate Basin Name ___________________________FLOW CONTROL FACILITY:Basin:Facility Name/Number _______________________________________ New Facility Project Impervious Facility Location ____________________________________________ Existing FacilityAcres Served ________UIC?පLJĞƐපŶŽUIC Site ID:% of Total Project Impervious cu.ft.Volume FactorAcres Served _____________________ ac.ft.____________of Safety_______ No. of Lots Served ________Control Structure location: _______________________________________________ Type of Control Structure: No. of Orifices/Restrictions __________ Riser in vault Size of Orifice/Restriction (in.) No.1 ______ cu.ft. Riser in Type II CB(numbered starting with lowestNo.2 ______ ac.ft. Weir in Type II CBorifice): No.3 ______(inches in decimal format) No.4 ______WATER QUALITY FACILITIES Design InformationIndicate no. of water quality facilities/BMPs for each type:Water Quality design flow (cfs)_______Flow dispersion Water Quality treated volume (sandfilter) (cu.ft.)_______Filter strip Water Quality storage volume (wetpool) (cu.ft.)_______Biofiltration swale regular, wet or Landscape management plan Farm management plan continuous inflow_______Wetvault combined w/detention______High flow bypass structure (e.g., flow-splitter catch basin) _______Wetpond basic large combined w/detention______Oil/water separator baffle coalescing plate_______Pre-settling pond ______Storm filter_______Stormwater wetland ______Pre-settling structure (Manufacturer:______________________)_______Sand filter basic large Sand bed depth ______Catch basin inserts (Manufacturer:________________________) regular linear vault(inches)________ ______Source controls _________________________________________ භIs facility lined? yes noIf so, what marker is used above liner?_____________________________________________________ Facility Summary Sheet Sketch: All detention, infiltration and water quality facilities must include a detailed sketch (11"x17" reduced size plan sheets preferred). Dam Safety Regulations (WA State Dept of Ecology):Reservoir Volume above natural gradeDepth of Reservoir above natural grade (ft)Live Storage VolumeLive Storage Depth (ft)Lindbergh HS Modernization and Additions16426 128th Avenue SE, Renton, WA 98058TBDLower Cedar RiverMolasses creek0.0221FILTERRA Page 1 of ___ Return Address: City Clerk’s Office City of Renton 1055 S Grady Way Renton, WA 98057 DECLARATION OF COVENANT FOR INSPECTION AND MAINTENANCE OF DRAINAGE FACILITIES AND ON-SITE BMPS Grantor: Grantee: City of Renton, a Washington municipal corporation Legal Description: Assessor's Tax Parcel ID#: IN CONSIDERATION of the approved City of Renton (check one of the following) Residential Building Permit Commercial Building Permit Clearing and Grading Permit Civil Construction or Utility Permit for Permit(s)_____________________ (Construction/Building/Utility Permit #) relating to the real property ("Property") described above, the Grantor(s), the owner(s) in fee of that Property, hereby covenants (covenant) with the City of Renton (“City of Renton” or “City”), a municipal corporation of the state of Washington, that he/she (they) will observe, consent to, and abide by the conditions and obligations set forth and described in Paragraphs 1 through 9 below with regard to the Property, and hereby grants (grant) an easement as described in Paragraphs 2 and 3. Grantor(s) hereby grants (grant), covenants (covenant), and agrees (agree) as follows: 1.The Grantor(s) or his/her (their) successors in interest and assigns ("Owners ") shall at their own cost, operate, maintain, and keep in good repair, the Property's drainage facilities constructed as required in the approved construction plans and specifications __________________ (Project Plan #) on file with the City of Renton and submitted to the City of Renton for the review and approval of permit(s) _____________________________ (Construction/Building/Utility Permit #). The Property's drainage facilities are shown and/or listed on Exhibit A – Site Plan. The Property’s drainage facilities shall be maintained in compliance with the operation and maintenance schedule included and attached herein as Exhibit B – Operations and Maintenance. Drainage facilities include pipes, channels, flow control facilities, water quality facilities, on-site best management practices (BMPs) and other engineered structures designed to manage and/or Renton School District See Exhibit C 2823059004, 2823059042 TBD TBD TBD 25 4 4 Page 2 of ___ treat stormwater on the Property. On-site BMPs include dispersion and infiltration devices, bioretention, permeable pavements, rainwater harvesting systems, tree retention credit, reduced impervious surface footprint, vegetated roofs and other measures designed to mimic pre-developed hydrology and minimize stormwater runoff on the Property. 2.City of Renton shall have the right to ingress and egress over those portions of the Property necessary to perform inspections of the stormwater facilities and BMPs and conduct maintenance activities specified in this Declaration of Covenant and in accordance with the Renton Municipal Code. City of Renton shall provide at least thirty (30) days’ written notice to the Owners that entry on the Property is planned for the inspection of drainage facilities. After the thirty (30) days, the Owners shall allow the City of Renton to enter for the sole purpose of inspecting drainage facilities. In lieu of inspection by the City, the Owners may elect to engage a licensed civil engineer registered in the state of Washington who has expertise in drainage to inspect the drainage facilities and provide a written report describing their condition. If the engineer option is chosen, the Owners shall provide written notice to the City of Renton within fifteen (15) days of receiving the City’s notice of inspection. Within thirty (30) days of giving this notice, the Owners, or engineer on behalf of the Owners, shall provide the engineer’s report to the City of Renton. If the report is not provided in a timely manner as specified above, the City of Renton may inspect the drainage facilities without further notice. 3.If City of Renton determines from its inspection, or from an engineer’s report provided in accordance with Paragraph 2, that maintenance, repair, restoration, and/or mitigation work is required to be done to any of the drainage facilities, City of Renton shall notify the Owners of the specific maintenance, repair, restoration, and/or mitigation work (“Work”) required pursuant to the Renton Municipal Code. The City shall also set a reasonable deadline for the Owners to complete the Work, or to provide an engineer’s report that verifies completion of the Work. After the deadline has passed, the Owners shall allow the City access to re-inspect the drainage facilities unless an engineer’s report has been provided verifying completion of the Work. If the Work is not completed within the time frame set by the City, the City may initiate an enforcement action and/or perform the Work and hereby is given access to the Property for such purposes. Written notice will be sent to the Owners stating the City’s intention to perform such Work. This Work will not commence until at least seven (7) days after such notice is mailed. If, within the sole discretion of the City, there exists an imminent or present danger, the seven (7) day notice period will be waived and Work will begin immediately. 4.The Owners shall assume all responsibility for the cost of any Work, or any measures taken by the City to address conditions as described in Paragraph 3. Such responsibility shall include reimbursement to the City within thirty (30) days of the receipt of the invoice for any such Work performed. Overdue payments will require payment of interest at the maximum legal rate allowed by RCW 19.52.020 (currently twelve percent (12%)). If the City initiates legal action to enforce this agreement, the prevailing party in such action is entitled to recover reasonable litigation costs and attorney’s fees. 5.The Owners are required to obtain written approval from City of Renton prior to filling, piping, cutting, or removing vegetation (except in routine landscape maintenance) in open vegetated stormwater facilities (such as swales, channels, ditches, ponds, etc.), or performing any alterations or modifications to the drainage facilities referenced in this Declaration of Covenant. 25 Page 3 of ___ 6.Any notice or consent required to be given or otherwise provided for by the provisions of this Agreement shall be effective upon personal delivery, or three (3) days after mailing by Certified Mail, return receipt requested. 7.With regard to the matters addressed herein, this agreement constitutes the entire agreement between the parties, and supersedes all prior discussions, negotiations, and all agreements whatsoever whether oral or written. 8.This Declaration of Covenant is intended to protect the value and desirability and promote efficient and effective management of surface water drainage of the real property described above, and shall inure to the benefit of all the citizens of the City of Renton and its successors and assigns. This Declaration of Covenant shall run with the land and be binding upon Grantor(s), and Grantor's(s') successors in interest, and assigns. 9.This Declaration of Covenant may be terminated by execution of a written agreement by the Owners and the City that is recorded by King County in its real property records. IN WITNESS WHEREOF, this Declaration of Covenant for the Inspection and Maintenance of Drainage Facilities is executed this _____ day of ____________________, 20_____. GRANTOR, owner of the Property GRANTOR, owner of the Property STATE OF WASHINGTON ) COUNTY OF KING )ss. On this day personally appeared before me: , to me known to be the individual(s) described in and who executed the within and foregoing instrument and acknowledged that they signed the same as their free and voluntary act and deed, for the uses and purposes therein stated. Given under my hand and official seal this _____ day of ___________________, 20_____. Printed name Notary Public in and for the State of Washington, residing at My appointment expires 25 EXHIBIT A - SITE PLAN LINDBERGH HIGH SCHOOL PAGE 4 OF 25 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 1/3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin. No trash or debris in the 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 is 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 1/4 inch wide at 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 Sedimentaccumulation 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. 2016 Surface Water Design Manual – Appendix A 4/24/2016A-9 EXHIBIT B - OPERATIONS AND MAINTENANCE PAGE 5 OF 25 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 7/8 inch. 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. 4/24/2016 2016 Surface Water Design Manual – Appendix AA-10PAGE 6 OF 25 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 toslopes 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. 2016 Surface Water Design Manual – Appendix A 4/24/2016A-11PAGE 7 OF 25 APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2017 City of Renton Surface Water Design Manual 12/12/2016 A-17 NO. 11 – GROUNDS (LANDSCAPING) 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 City personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where City 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. Excessive growth of grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches. Trees and Shrubs Hazard tree identified Any tree or limb of a tree identified as having a potential to fall and cause property damage or threaten human life. A hazard tree identified by a qualified arborist must be removed as soon as possible. No hazard trees in facility. Damaged tree or shrub identified Limbs or parts of trees or shrubs that are split or broken which affect more than 25% of the total foliage of the tree or shrub. Trees and shrubs with less than 5% of total foliage with split or broken limbs. Trees or shrubs that have been blown down or knocked over. No blown down vegetation or knocked over vegetation. Trees or shrubs free of injury. Trees or shrubs which are not adequately supported or are leaning over, causing exposure of the roots. Tree or shrub in place and adequately supported; dead or diseased trees removed. PAGE 8 OF 25 Filterra Owner’s Manual ® Bioretention Systems ENGINEERED SOLUTIONS This Owner’s Manual applies to all precast Filterra Configurations, including Filterra Bioscape Vault. PAGE 9 OF 25 PAGE 10 OF 25 www.ContechES.com/filterra | 800-338-1122 3 Table of Contents Introduction ................................................................................4 Activation Overview .....................................................................4 Filterra Plant Selection Overview ...................................................6 Warranty Overview ......................................................................6 Routine Maintenance Guidelines...................................................6 Maintenance Visit Procedure .........................................................9 Appendix 1 – Activation Checklist ...............................................12 Appendix 2 – Planting Requirements for Filterra Systems ................13 Appendix 3 – Filterra Tree Grate Opening Expansion Procedure ....15 ® Bioretention Systems ENGINEERED SOLUTIONS PAGE 11 OF 25 www.ContechES.com/filterra | 800-338-11224 Introduction Thank you for your purchase of the Filterra® Bioretention System. Filterra is a specially engineered stormwater treatment system incorporating high performance biofiltration media to remove pollutants from stormwater runoff. The system’s biota (vegetation and soil microorganisms) then further breakdown and absorb captured pollutants. All components of the system work together to provide a sustainable long-term solution for treating stormwater runoff. The Filterra system has been delivered to you with protection in place to resist intrusion of construction related sediment which can contaminate the biofiltration media and result in inadequate system performance. These protection devices are intended as a best practice and cannot fully prevent contamination. It is the purchaser’s responsibility to provide adequate measures to prevent construction related runoff from entering the Filterra system. Included with your purchase is Activation of the Filterra system by the manufacturer as well as a 1-year warranty from delivery of the system and 1-year of routine maintenance (mulch replacement, debris removal, and pruning of vegetation) up to twice during the first year after activation. Design and Installation Each project presents different scopes for the use of Filterra systems. Information and help may be provided to the design engineer during the planning process. Correct Filterra box sizing (by rainfall region) is essential to predict pollutant removal rates for a given area. The engineer shall submit calculations for approval by the local jurisdiction. The contractor is responsible for the correct installation of Filterra units as shown in approved plans. A comprehensive installation manual is available at www.ContechES.com. Activation Overview Activation of the Filterra system is a procedure completed by the manufacturer to place the system into working condition. This involves the following items: • Removal of construction runoff protection devices • Planting of the system’s vegetation • Placement of pretreatment mulch layer using mulch certified for use in Filterra systems. Activation MUST be provided by the manufacturer to ensure proper site conditions are met for Activation, proper installation of the vegetation, and use of pretreatment mulch certified for use in Filterra systems. PAGE 12 OF 25 www.ContechES.com/filterra | 800-338-1122 5 Minimum Requirements The minimum requirements for Filterra Activation are as follows: 1. The site landscaping must be fully stabilized, i.e. full landscaping installed and some grass cover (not just straw and seed) is required to reduce sediment transport. Construction debris and materials should be removed from surrounding area. 2. Final paving must be completed. Final paving ensures that paving materials will not enter and contaminate the Filterra system during the paving process, and that the plant will receive runoff from the drainage area, assisting with plant survival for the Filterra system. 3. Where curb inlets are included as part of the Filterra system, Filterra throat opening should be at least 4” in order to ensure adequate capacity for inflow and debris. An Activation Checklist is included on page 12 to ensure proper conditions are met for Contech to perform the Activation services. A charge of $500.00 will be invoiced for each Activation visit requested by Customer where Contech determines that the site does not meet the conditions required for Activation. PAGE 13 OF 25 www.ContechES.com/filterra | 800-338-11226 Filterra Plant Selection Overview A Plant List is available on the Contech website highlighting recommended plants for Filterra systems in your area. Keep in mind that plants are subject to availability due to seasonality and required minimum size for the Filterra system. Plants installed in the Filterra system are container plants (max 15 gallon) from nursery stock and will be immature in height and spread at Activation. It is the responsibility of the owner to provide adequate irrigation when necessary to the plant of the Filterra system. The “Planting Requirements for Filterra Systems” document is included as an appendix and discusses proper selection and care of the plants within Filterra systems. Warranty Overview Refer to the Contech Engineered Solutions LLC Stormwater Treatment System LIMITED WARRANTY for further information. The following conditions may void the Filterra system’s warranty and waive the manufacturer provided Activation and Maintenance services: • Unauthorized activation or performance of any of the items listed in the activation overview • Any tampering, modifications or damage to the Filterra system or runoff protection devices • Removal of any Filterra system components • Failure to prevent construction related runoff from entering the Filterra system • Failure to properly store and protect any Filterra components (including media and underdrain stone) that may be shipped separately from the vault Routine Maintenance Guidelines With proper routine maintenance, the biofiltration media within the Filterra system should last as long as traditional bioretention media. Routine maintenance is included by the manufacturer on all Filterra systems for the first year after activation. This includes a maximum of 2 visits to remove debris, replace pretreatment mulch, and prune the vegetation. More information is provided in the Operations and Maintenance Guidelines. Some Filterra systems also contain pretreatment or outlet bays. Depending on site pollutant loading, these bays may require periodic removal of debris, however this is not included in the first year of maintenance, and would likely not be required within the first year of operation. These services, as well as routine maintenance outside of the included first year, can be provided by certified maintenance providers listed on the Contech website. Training can also be provided to other stormwater maintenance or landscape providers. PAGE 14 OF 25 www.ContechES.com/filterra | 800-338-1122 7 Why Maintain? All stormwater treatment systems require maintenance for effective operation. This necessity is often incorporated in your property’s permitting process as a legally binding BMP maintenance agreement. Other reasons to maintain are: • Avoiding legal challenges from your jurisdiction’s maintenance enforcement program. • Prolonging the expected lifespan of your Filterra media. • Avoiding more costly media replacement. • Helping reduce pollutant loads leaving your property. Simple maintenance of the Filterra is required to continue effective pollutant removal from stormwater runoff before discharge into downstream waters. This procedure will also extend the longevity of the living biofilter system. The unit will recycle and accumulate pollutants within the biomass, but is also subjected to other materials entering the inlet. This may include trash, silt and leaves etc. which will be contained above the mulch layer. Too much silt may inhibit the Filterra’s flow rate, which is the reason for site stabilization before activation. Regular replacement of the mulch stops accumulation of such sediment. When to Maintain? Contech includes a 1-year maintenance plan with each system purchase. Annual included maintenance consists of a maximum of two (2) scheduled visits. Additional maintenance may be necessary depending on sediment and trash loading (by Owner or at additional cost). The start of the maintenance plan begins when the system is activated. Maintenance visits are typically scheduled seasonally; the spring visit aims to clean up after winter loads including salts and sands while the fall visit helps the system by removing excessive leaf litter. It has been found that in regions which receive between 30-50 inches of annual rainfall, (2) two visits are generally required; regions with less rainfall often only require (1) one visit per annum. Varying land uses can affect maintenance frequency; e.g. some fast food restaurants require more frequent trash removal. Contributing drainage areas which are subject to new development wherein the recommended erosion and sediment control measures have not been implemented may require additional maintenance visits. Some sites may be subjected to extreme sediment or trash loads, requiring more frequent maintenance visits. This is the reason for detailed notes of maintenance actions per unit, helping the Supplier and Owner predict future maintenance frequencies, reflecting individual site conditions. Owners must promptly notify the maintenance provider of any damage to the plant(s), which constitute(s) an integral part of the bioretention technology. Owners should also advise other landscape or maintenance contractors to leave all maintenance to the Supplier (i.e. no pruning or fertilizing) during the first year. PAGE 15 OF 25 www.ContechES.com/filterra | 800-338-11228 Exclusion of Services Clean up due to major contamination such as oils, chemicals, toxic spills, etc. will result in additional costs and are not covered under the Supplier maintenance contract. Should a major contamination event occur the Owner must block off the outlet pipe of the Filterra (where the cleaned runoff drains to, such as drop inlet) and block off the throat of the Filterra. The Supplier should be informed immediately. Maintenance Visit Summary Each maintenance visit consists of the following simple tasks (detailed instructions below). 1. Inspection of Filterra and surrounding area 2. Removal of tree grate (where applicable) and erosion control stones 3. Removal of debris, trash and mulch 4. Mulch replacement 5. Plant health evaluation and pruning or replacement as necessary 6. Clean area around Filterra 7. Complete paperwork Maintenance Tools, Safety Equipment and Supplies Ideal tools include: camera, bucket, shovel, broom, pruners, hoe/rake, and tape measure. Appropriate Personal Protective Equipment (PPE) should be used in accordance with local or company procedures. This may include impervious gloves where the type of trash is unknown, high visibility clothing and barricades when working in close proximity to traffic and also safety hats and shoes. A T-Bar or crowbar should be used for moving the tree grates, where applicable (up to 170 lbs each). If tree grate opening expansion is necessary, safety glasses/goggles and a 3lb or greater mini sledgehammer are required. Most visits require minor trash removal and a full replacement of mulch. See below for actual number of bagged mulch that is required in each media bay size. Mulch should be a double shredded, hardwood variety. Some visits may require additional Filterra engineered soil media available from the Supplier. Media Bay Length Media Bay Width Filter Surface Area (ft²)Volume at 3” (ft³)# of 2 ft³ Mulch Bags 4 4 16 4 2 6 4 24 6 3 8 4 32 8 4 6 6 36 9 5 8 6 48 12 6 10 6 60 15 8 12 6 72 18 9 13 7 91 23 12 Other sizes not listed - 1 bag per 8 ft² of media. PAGE 16 OF 25 www.ContechES.com/filterra | 800-338-1122 9 1. Inspection of Filterra and surrounding area • Record individual unit before maintenance with photograph (numbered). Record on Maintenance Report (see example in this document) the following: 2. Removal of tree grate (if applicable) and erosion control stones • Remove cast iron grates for access into Filterra box (if applicable). • Dig out silt (if any) and mulch and remove trash & foreign items. 3. Removal of debris, trash and mulch • After removal of mulch and debris, measure distance from the top of the Filterra engineered media soil to the top of the top slab. Compare the measured distance to the distance shown on the approved Contract Drawings for the system. Add Filterra media (not top soil or other) to bring media up as needed to distance indicated on drawings. Record on Maintenance Report the following: Standing Water yes | no Damage to Box Structure yes | no Damage to Grate (if applicable) yes | no Is Bypass Clear yes | no If yes answered to any of these observations, record with close-up photograph (numbered). Record on Maintenance Report the following: Silt/Clay yes | no Cups/ Bags yes | no Leaves yes | no Buckets Removed ________ Record on Maintenance Report the following: Distance to Top of Top Slab (inches) ________ Inches of Media Added ________ Maintenance Visit Procedure Keep sufficient documentation of maintenance actions to predict location specific maintenance frequencies and needs. An example Maintenance Report is included in this manual. PAGE 17 OF 25 www.ContechES.com/filterra | 800-338-112210 4. Mulch replacement • Add double shredded mulch evenly across the entire unit to a depth of 3”. • Refer to Filterra Mulch Specifications for information on acceptable sources. • Ensure correct repositioning of erosion control stones by the Filterra inlet to allow for entry of trash during a storm event. • Replace Filterra grates (if applicable) correctly using appropriate lifting or moving tools, taking care not to damage the plant. • Where applicable, if 6” tree grate opening is too close to plant trunk, the grate opening may be expanded to 12” using a mini sledgehammer. Refer to instructions in Appendix 3. 5. Plant health evaluation and pruning or replacement as necessary • Examine the plant’s health and replace if necessary. • Prune as necessary to encourage growth in the correct directions 6. Clean area around Filterra • Clean area around unit and remove all refuse to be disposed of appropriately. 7. Complete paperwork • Deliver Maintenance Report and photographs to appropriate location (normally Contech during maintenance contract period). • Some jurisdictions may require submission of maintenance reports in accordance with approvals. It is the responsibility of the Owner to comply with local regulations. Record on Maintenance Report the following: Height above top of Filterra Unit __________________(ft) Width at Widest Point __________________(ft) Health healthy | unhealthy Damage to Plant yes | no Plant Replaced yes | no PAGE 18 OF 25 www.ContechES.com/filterra | 800-338-1122 11 Maintenance Checklist Filterra Inspection & Maintenance Log Filterra System Size/Model: _____________________________Location: ____________________________________________ Drainage System Failure Problem Conditions to Check Condition that Should Exist Actions Inlet Excessive sediment or trash accumulation. Accumulated sediments or trash impair free flow of water into Filterra. Inlet should be free of obstructions allowing free distributed flow of water into Filterra. Sediments and/or trash should be removed. Mulch Cover Trash and floatable debris accumulation.Excessive trash and/or debris accumulation.Minimal trash or other debris on mulch cover. Trash and debris should be removed and mulch cover raked level. Ensure bark nugget mulch is not used. Mulch Cover “Ponding” of water on mulch cover. “Ponding” in unit could be indicative of clogging due to excessive fine sediment accumulation or spill of petroleum oils. Stormwater should drain freely and evenly through mulch cover. Recommend contact manufacturer and replace mulch as a minimum. Vegetation Plants not growing or in poor condition. Soil/mulch too wet, evidence of spill. Incorrect plant selection. Pest infestation. Vandalism to plants. Plants should be healthy and pest free.Contact manufacturer for advice. Vegetation Plant growth excessive. Plants should be appropriate to the species and location of Filterra. Trim/prune plants in accordance with typical landscaping and safety needs. Structure Structure has visible cracks. Cracks wider than 1/2 inch or evidence of soil particles entering the structure through the cracks. Vault should be repaired. Maintenance is ideally to be performed twice annually. Date Mulch & Debris Removed Depth of Mulch Added Mulch Brand Height of Vegetation Above Top of Vault Vegetation Species Issues with System Comments 1/1/17 5 – 5 gal Buckets 3”Lowe’s Premium Brown Mulch 4’Galaxy Magnolia - Standing water in downstream structure - Removed blockage in downstream structure PAGE 19 OF 25 www.ContechES.com/filterra | 800-338-112212 Appendix 1 – Filterra® Activation Checklist Project Name: ________________________________________Company: ______________________________________________ Site Contact Name: _______________________________________Site Contact Phone/Email: ____________________________ Site Owner/End User Name: _________________________Site Owner/End User Phone/Email: ____________________________ Preferred Activation Date: ___________________________________(provide 2 weeks minimum from date this form is submitted) Site Designation System Size Final Pavement / Top Coat Complete Landscaping Complete / Grass Emerging Construction materials / Piles / Debris Removed Throat Opening Measures 4” Min. Height Plant Species Requested  Yes  No  Yes  No  Yes  No  Yes  No  N/A  Yes  No  Yes  No  Yes  No  Yes  No  N/A  Yes  No  Yes  No  Yes  No  Yes  No  N/A  Yes  No  Yes  No  Yes  No  Yes  No  N/A  Yes  No  Yes  No  Yes  No  Yes  No  N/A  Yes  No  Yes  No  Yes  No  Yes  No  N/A  Yes  No  Yes  No  Yes  No  Yes  No  N/A  Yes  No  Yes  No  Yes  No  Yes  No  N/A  Yes  No  Yes  No  Yes  No  Yes  No  N/A NOTE: A charge of $500.00 will be invoiced for each Activation visit requested by Customer where Contech determines that the site does not meet the conditions required for Activation. ONLY Contech authorized representatives can perform Activation of Filterra systems; unauthorized Activations will void the system warranty and waive manufacturer supplied Activation and 1st Year Maintenance. Attach additional sheets as necessary. Signature Date ENGINEERED SOLUTIONS PAGE 20 OF 25 www.ContechES.com/filterra | 800-338-1122 13 Appendix 2 – Planting Requirements for Filterra® Systems Plant Material Selection • Select plant(s) as specified in the engineering plans and specifications. • Select plant(s) with full root development but not to the point where root bound. • Use local nursery container plants only. Ball and burlapped plants are not permitted. • For precast Filterra systems with a tree grate, plant(s) must not have scaffold limbs at least 14 inches from the crown due to spacing between the top of the mulch and the tree grate. Lower branches can be pruned away provided there are sufficient scaffold branches for tree or shrub development. • For precast Filterra systems with a tree grate, at the time of installation, it is required that plant(s) must be at least 6” above the tree grate opening at installation for all Filterra configurations. This DOES NOT apply to Full Grate Cover designs. • Plant(s) shall not have a mature height greater than 25 feet. • For standard 21” media depth, a 7 – 15 gallon container size shall be used. Media less than 21” (Filterra boxes only) may require smaller container plants. • For precast Filterra systems, plant(s) should have a single trunk at installation, and pruning may be necessary at activation and maintenance for some with a tree grate of the faster growing species, or species known to produce basal sprouts. Plant Installation • During transport protect the plant foliage from wind and excessive jostling. • Prior to removing the plant(s) from the container, ensure the soil moisture is sufficient to maintain the integrity of the root ball. If needed, pre-wet the container plant. • Cut away any roots which are growing out of the container drain holes. Plants with excessive root growth from the drain holes should be rejected. • Plant(s) should be carefully removed from the pot by gently pounding on the sides of the container with the fist to loosen root ball. Then carefully slide out. Do not lift plant(s) by trunk as this can break roots and cause soil to fall off. Extract the root ball in a horizontal position and support it to prevent it from breaking apart. Alternatively the pot can be cut away to minimize root ball disturbance. • Remove any excess soil from above the root flare after removing plant(s) from container. • Excavate a hole with a diameter 4” greater than the root ball, gently place the plant(s). • If plant(s) have any circling roots from being pot bound, gently tease them loose without breaking them. • If root ball has a root mat on the bottom, it should be shaved off with a knife just above the mat line. • Plant the tree/shrub/grass with the top of the root ball 1” above surrounding media to allow for settling. • All plants should have the main stem centered in the tree grate (where applicable) upon completion of installation. • With all trees/shrubs, remove dead, diseased, crossed/rubbing, sharply crotched branches or branches growing excessively long or in wrong direction compared to majority of branches. • To prevent transplant shock (especially if planting takes place in the hot season), it may be necessary to prune some of the foliage to compensate for reduced root uptake capacity. This is accomplished by pruning away some of the smaller secondary branches or a main scaffold branch if there are too many. Too much foliage relative to the root ball can dehydrate and damage the plant. • Plant staking may be required. PAGE 21 OF 25 www.ContechES.com/filterra | 800-338-112214 Mulch Installation • Only mulch that meets Contech Engineered Solutions’ mulch specifications can be used in the Filterra system. • Mulch must be applied to a depth of 3” evenly over the surface of the media. Irrigation Requirements • Each Filterra system must receive adequate irrigation to ensure survival of the living system during periods of drier weather. • Irrigation sources include rainfall runoff from downspouts and/or gutter flow, applied water through the top/tree grate or in some cases from an irrigation system with emitters installed during construction. • At Activation: Apply about one (cool climates) to two (warm climates) gallons of water per inch of trunk diameter over the root ball. • During Establishment: In common with all plants, each Filterra plant will require more frequent watering during the establishment period. One inch of applied water per week for the first three months is recommended for cooler climates (2 to 3 inches for warmer climates). If the system is receiving rainfall runoff from the drainage area, then irrigation may not be needed. Inspection of the soil moisture content can be evaluated by gently brushing aside the mulch layer and feeling the soil. Be sure to replace the mulch when the assessment is complete. Irrigate as needed**. • Established Plants: Established plants have fully developed root systems and can access the entire water column in the media. Therefore irrigation is less frequent but requires more applied water when performed. For a mature system assume 3.5 inches of available water within the media matrix. Irrigation demand can be estimated as 1” of irrigation demand per week. Therefore if dry periods exceed 3 weeks, irrigation may be required. It is also important to recognize that plants which are exposed to windy areas and reflected heat from paved surfaces may need more frequent irrigation. Long term care should develop a history which is more site specific. ** Five gallons per square yard approximates 1 inch of water Therefore for a 6’ by 6’ Filterra approximately 20-60 gallons of water is needed. To ensure even distribution of water it needs to be evenly sprinkled over the entire surface of the filter bed, with special attention to make sure the root ball is completely wetted. NOTE: if needed, measure the time it takes to fill a five gallon bucket to estimate the applied water flow rate then calculate the time needed to irrigate the Filterra. For example, if the flow rate of the sprinkler is 5 gallons/minute then it would take 12 minutes to irrigate a 6’ by 6’ filter. PAGE 22 OF 25 www.ContechES.com/filterra | 800-338-1122 15 Appendix 3 – Filterra® Tree Grate Opening Expansion Procedure The standard grates used on all Filterra configurations that employ Tree Grates are fabricated with a 6” opening that is designed with a breakaway section that can be removed, allowing the grate opening to be expanded to 12” as the tree matures and the trunk widens. The following tools are required to expand the opening: • Mini sledgehammer (3 lb. or greater) • Safety Glasses / Goggles The following guidelines should be followed to properly expand the tree opening from 6” to 12”: 1. Remove the grate from the Filterra frame, place it flat on a hard surface, and support the grate by stepping on the edge or using other weighted items such as a few mulch bags if this is being done during a Filterra maintenance event. Put on safety glasses/goggles. Align the mini sledgehammer as shown in the figure to the left. The head of the sledgehammer should be aimed just inside the wide cast iron bar between the larger grate section and the breakaway section. 2. Repeatedly hit the grate at this spot with the mini sledgehammer. 3. After several hits, the breakaway section should snap cleanly off of the larger grate section. Reinstall the grate into the Filterra grate frame. Recycle or dispose of the breakaway section per local guidelines. PAGE 23 OF 25 PDF 6/21 © 2021 Contech Engineered Solutions LLC, a QUIKRETE Company 9025 Centre Pointe Drive, Suite 400 West Chester, OH 45069 info@conteches.com | 800-338-1122 www.ContechES.com ALL RIGHTS RESERVED. PRINTED IN THE USA. NOTHING IN THIS CATALOG SHOULD BE CONSTRUED AS A WARRANTY. APPLICATIONS SUGGESTED HEREIN ARE DESCRIBED ONLY TO HELP READERS MAKE THEIR OWN EVALUATIONS AND DECISIONS, AND ARE NEITHER GUARANTEES NOR WARRANTIES OF SUITABILITY FOR ANY APPLICATION. CONTECH MAKES NO WARRANTY WHATSOEVER, EXPRESS OR IMPLIED, RELATED TO THE APPLICATIONS, MATERIALS, COATINGS, OR PRODUCTS DISCUSSED HEREIN. ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND ALL IMPLIED WARRANTIES OF FITNESS FOR ANY PARTICULAR PURPOSE ARE DISCLAIMED BY CONTECH. SEE CONTECH’S CONDITIONS OF SALE (AVAILABLE AT WWW.CONTECHES.COM/COS) FOR MORE INFORMATION. ® Bioretention Systems ENGINEERED SOLUTIONS PAGE 24 OF 25 EXHIBIT C – LEGAL DESCRIPTION PARCEL A: THE EAST 500 FEET OF THE NORTH 1121 FEET OF THE SOUTHEAST QUARTER OF THE NORTHEAST QUARTER OF SECTION 28, TOWNSHIP 23 NORTH, RANGE 5 EAST OF THE WILLAMETTE MERIDIAN, IN KING COUNTY, WASHINGTON. PARCEL B: THE EASTERLY 330 FEET OF THE SOUTHERLY 216.47 FEET, MORE OR LESS, OF SOUTHEAST QUARTER OF THE NORTHEAST QUARTER OF SECTION 28, TOWNSHIP 23 NORTH, RANGE 5 EAST OF THE WILLAMETTE MERIDIAN, IN KING COUNTY, WASHINGTON. PARCEL C: THE SOUTHEAST QUARTER OF THE NORTHEAST QUARTER OF SECTION 28, TOWNSHIP 23 NORTH, RANGE 5 EAST OF THE WILLAMETTE MERIDIAN, IN KING CUONTY WASHINGTON; EXCEPTING THEREFROM THE EAST 500 FEET OF THE NORTH 1121 FEET; ALSO EXCEPTING THEREFROM THE EAST 330 FEET OF THE SOUTH 216.47 FEET; ALSO EXCEPTING THEREFROM THE SOUTH 250 FEET OF THE EAST 523 FEET OF THE WEST 553 FEET; ALSO EXCEPTING THEREFROM ANY PORTION LYING WIHTIN THE BOUNDARIES OF 128TH AVENUE SE. PAGE 25 OF 25