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HomeMy WebLinkAboutF_Sierra Heights ES Ballfield_TIR_Approved Sierra Heights Elementary School Playfield Renovations 2501 Union Avenue NE Renton, WA 98059 Technical Information Report June 11, 2021 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: Traci Brewer-Rogstad Prepared for: Nicole Hernandez, P.E. LPD Engineering, PLLC 1932 1st Ave, Suite 201 Seattle, WA 98101 (206) 725-1211 DA Hogan & Associates 119 1st Ave, Suite 110 Seattle, WA 98104 (206) 285-0400 Contact: Dave Anderson APPROVED 07/30/2021 msippo DEVELOPMENT ENGINEERING DIVISION SIERRA HEIGHTS ELEMENTARY SCHOOL PLAYFIELD RENOVATIONS STORMWATER TECHNICAL INFORMATION REPORT TABLE OF CONTENTS Section 1 – Project Overview ................................................................................................. 1 Section 2 – Conditions and Requirements Summary ......................................................... 1 Section 3 – Offsite Analysis ..................................................................................................... 4 Section 4 – Flow Control and Water Quality Facility Analysis and Design ...................... 8 Section 5 – Conveyance Systems Analysis and Design ..................................................... 10 Section 6 – Special Reports and Studies ............................................................................. 10 Section 7 – Other Permits .................................................................................................... 10 Section 8 – CSWPPP ............................................................................................................ 10 Section 9 – Bond Quantities, Facility Summaries, and Declaration of Covenant .......... 11 Section 10 – Operations and Maintenance Manual ........................................................... 11 FIGURES Figure 1: TIR Worksheet Figure 2: Vicinity Map Figure 3: Existing Impervious Coverage Figure 4: Soils Map Figure 5: Downstream Drainage Map Figure 6: Proposed Conditions Target Surfaces Figure 7: Proposed Conditions Modeled Areas APPENDICES Appendix A – Design Drawings Appendix B – Design Calculations and Supporting Information Appendix C – Stormwater Pollution Prevention and Spill Plan (SWPPS) & Construction Stormwater Pollution Prevention Plan (SWPPP) Narrative Appendix D – Operations and Maintenance Guidelines Appendix E – Geotechnical Report LPD Engineering PLLC Page 1 Sierra Heights Elementary School Playfield Renovations Technical Information Report, June 11, 2021 SIERRA HEIGHTS ELEMENTARY SCHOOL PLAYFIELD RENOVATIONS STORMWATER TECHNICAL INFORMATION REPORT JUNE 11, 2021 SECTION 1 – PROJECT OVERVIEW This Technical Information Report (TIR) is for the playfield renovations at Sierra Heights Elementary School, located at 2501 Union Avenue NE in Renton, Washington. Refer to Figure 1 – TIR Worksheet for general project information. The school property is located on two parcels (0423059069 and 0423059176), totaling approximately 15.38 acres. The site is located in Section 4, Township 23 North, Range 5 East, Willamette Meridian. Refer to Figure 2 – Vicinity Map. The project area consists of the existing natural grass playfield located on the west portion of the school property. The proposed project includes the conversion of the existing soil-based natural grass field to a sand-based natural grass field. The existing grass has been hard packed and stormwater currently sheet flows across the field. To improve the drainage of the field, furrows below the sand base surface are proposed. These furrows will be filled with pea gravel to allow stormwater to infiltrate vertically through the natural turf and sand layer and be captured in the furrows. The furrows will allow stormwater to migrate through the gravel layer and ultimately be collected in French drains around the perimeter of the field, if not infiltrated into the native soils. This TIR addresses the eight core requirements and five special requirements of the 2017 City of Renton Surface Water Design Manual (SWDM). According to Figure 1.1.2.A of the 2017 Renton SWDM, Flow Chart for Determining Type of Drainage Review Required, the project requires a Full Drainage Review. SECTION 2 – CONDITIONS AND REQUIREMENTS SUMMARY This section addresses the requirements set forth by the 2017 City of Renton SWDM, Core and Special Requirements listed in Chapter 1. Core Requirements Core Requirement 1 – Discharge at Natural Location (1.2.1): In the existing conditions, the field slopes from south to north with drainage being collected in catch basins and routed easterly to the existing system in Union Avenue NE. Upon restoration of the field in the proposed conditions, the stormwater will be captured and routed through gravel filled furrows to ultimately be collected in a French drain. The French drain will discharge storm water into the onsite catch basin and pipe system flowing eastbound. There will be no change in the natural discharge location. LPD Engineering PLLC Page 2 Sierra Heights Elementary School Playfield Renovations Technical Information Report, June 11, 2021 Core Requirement 2 – Off-site Analysis (1.2.2): A level 1 Downstream Analysis has been completed for the project site and is included in Section 3 of this report. Core Requirement 3 – Flow Control (1.2.3): The project site is located in a forested flow control duration standard area, as mapped by the City of Renton. The following is a summary of applicable target surfaces that will require flow control mitigation, per the 2017 Renton SWDM. The project is considered a “new development” project based upon the definition from the Renton SWDM as the existing site has less than 35% impervious coverage. The project site has approximately 31.4% existing impervious surface (See Figure 3 – Existing Impervious Coverage). According to the Renton SWDM Section 1.2.3.1.B “Target Surfaces,” facilities in Flow Control Duration Standard Areas must mitigate (either directly or in effect) the runoff from the following target developed surfaces within the threshold discharge area for which the facility is required: 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). Interpretation: New impervious surfaces will be considered a target surface. 2. New pervious surface that is not fully dispersed or not farmland 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 project is not creating any new pervious surface. The definition of new pervious surface from the 2017 Renton SWDM 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). Per the definitions above, the project is not creating any new pervious surface. Therefore, this item does not apply to this project. 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 this project is a non-redevelopment project with more than 5,000 square feet of new plus replaced impervious surface, and therefore replaced impervious surfaces are considered a target surface. There are no replaced impervious surfaces proposed for this project. LPD Engineering PLLC Page 3 Sierra Heights Elementary School Playfield Renovations Technical Information Report, June 11, 2021 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 does not propose more than 5,000 square feet of new plus replaced impervious surface, and thus this item does not apply. As determined above, both new and replaced impervious surfaces would be considered “target surface”. This project includes a limited amount of new impervious surface, below the threshold requiring flow control facilities. Refer to the detailed description in Section 4 of this report for the proposed drainage systems. 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. The Stormwater Pollution Prevention Plan (SWPPP) narrative and Stormwater Pollution Prevention and Spill (SWPPS) plan narrative are attached in Appendix C of this report. Core Requirement 6 – Maintenance and Operations (1.2.6): The Operations and Maintenance guidelines for the Modular Wetland System (water quality facility) is attached in Appendix D. Core Requirement 7 – Financial Guarantees and Liability (1.2.7): The financial guarantees and liability are not required as the Owner is the Renton School District, a public agency. Core Requirement 8 – Water Quality (1.2.8): This project does not propose any new plus replaced pollution-generating impervious surfaces (PGIS) or pollution-generating pervious surface (PGPS). Therefore, it would meet Exemption #1 (Surface Area) per Section 1.2.8 of the Renton SWDM. However, as natural grass fields are considered pollution-generating, and therefore a Modular Wetland System is proposed, which will provide enhanced treatment for the resurface field. Core Requirement 9 – On-Site BMPs (1.2.9): The evaluation of On-site BMPs is required, as the project involves greater than 7,000 square feet of land disturbing activity. The project will utilize sheet flow dispersion for the target surfaces requiring evaluation. Refer to the On-Site BMPs evaluation within Section 4 of this report. LPD Engineering PLLC Page 4 Sierra Heights Elementary School Playfield Renovations Technical Information Report, June 11, 2021 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 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 project site is within the May Creek Basin, which adopted the May Creek Basin Action Plan in 2001. The plan was reviewed to determine if there are any regulations applicable to this site. There are no additional water quality requirements listed be 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. • 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): In the proposed conditions, there will be no applicable activities matching those listed within the 2017 of Renton Surface Water Design Manual that will require the use of source control measures. 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. SECTION 3 – OFFSITE ANALYSIS The following is a Level 1 downstream analysis for the project site. Task 1 – Study Area Definition and Maps The project area totals approximately 3.40 acres and consists of an existing grass playfield to the west of the main school facilities. There is a sand infield in the southwest corner of the field area. The downstream analysis for the project area is based upon the following resources: • Site Survey • City of Renton GIS Mapping LPD Engineering PLLC Page 5 Sierra Heights Elementary School Playfield Renovations Technical Information Report, June 11, 2021 • King County iMap Task 2 – Resource Review The following resources have been reviewed for the project area: Basin Summary King County’s iMap identifies that the project area is located within the May Creek Drainage Basin. The field area is not underdrained, and based on the field topography, runoff would flow to the north edge of the field. The proposed collection system will connect with the existing piped storm system in the paved play area, east of the field. Thus, this path will be tracked for the downstream analysis. This will be described in further detail in Task 4. 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 application was used to examine the SAOs.  SAO Erosion Hazard – The project site is not located within an erosion hazard area. North of the project site is an erosion hazard area.  SAO Seismic Hazard – The project site is not located within a seismic hazard 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 streams or any waterbodies through the developed school site.  SAO Wetland – There are no SAO wetland on or adjacent to the 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 or adjacent to a channel migration hazard area. Critical Areas The critical areas within the upstream and one downstream of the project site were examined using the City of Renton GIS application. Based on the GIS mapping, the following are the critical area designations for the project site, upstream area and one mile downstream of the site. LPD Engineering PLLC Page 6 Sierra Heights Elementary School Playfield Renovations Technical Information Report, June 11, 2021  Critical Area Ordinance (CAO) Floodway: The downstream study areas are located with a special flood hazard area (100-year flood).  Renton Regulated Slopes: Per Renton Maps, both north and south of the field area has regulated slopes (15-25%).  Wetland: Per Renton Maps, there is a constructed wetland to the west of the field area. The stormwater runoff from the project area will not be directed to this wetland. Topographic Map The topographic information for the project site is shown on the topographical survey included in Appendix A of this report. The project area is relatively flat, with the topography of the existing field sloping from south to north, at a grade of approximately 1.5-2% and dropping about 6 feet across the entire field. There is a small grass hill directly south of the field with slope of about 20%. The adjacent paved play area slopes toward the field at approximately 1%. Drainage Complaints Drainage complaints for the project site and downstream drainage course have been investigated using King County iMap. There are no relevant drainage complaints along the downstream drainage path, from the site discharge point to the outfall into May Creek. King County Soils Survey According to the USDA Natural Resources Conservation Service, the underlying soils for the site is Alderwood gravelly sandy loam, 8 to 15 percent slopes. A small portion of the northern regions of the school property are mapped as consisting of Everett very gravelly sandy loam, 15 to 30 percent slopes (EvD). A geotechnical report has been prepared by Associated Earth Sciences, Inc., dated August 21, 2020. For the geotechnical borings in close proximity to the project area (EB-1 through EB-4), there was encountered fill at varying depths ranging from 6-inches to 19 feet. There was encountered Vashon lodgment till at varying depths ranging from 3.5 to 20.5 feet. No groundwater was encountered during any of the boring explorations. Four onsite hand borings were included in the reports from 2019 (HA-1 through HA-4). Fill was encountered at varying depths ranging from 6-inches to 3.5 feet. 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. 303d List of Polluted Waters Per the Department of Ecology Water Quality Atlas, May Creek has 303(d) category 5 listings. May Creek has two listings for temperature, one listing for bacteria, and one listing for bioassessment. Water Quality Problems Per the 2017 Renton SWDM, King County-identified water quality problems do not apply to the City of Renton. LPD Engineering PLLC Page 7 Sierra Heights Elementary School Playfield Renovations Technical Information Report, June 11, 2021 Task 3 – Field Inspection Existing Onsite Conditions The project area includes the existing natural grass playfield, located directly west of the paved play area. There is a dirt infield in the southwest corner for baseball/softball with a fenced backstop. There are a few portable buildings southeast of the field. The school campus is bounded by forested area to the north and west, single-family residential properties to the south, and Union Avenue NE to the east. The existing soil based natural grass field is not currently under-drained and has become hard-packed. Stormwater runoff currently sheet flows from south to north and is collected in catch basins located at the north end of the field. From here, stormwater is conveyed east along the downstream path described in Task 4. Upstream Basin There is a grass slope south of the field and the paved play area east of the field that comprise the upstream basin tributary to the project area. Conveyance calculations take this upstream area into account within the stormwater model. Task 4 – Drainage System Description and Problem Descriptions As noted previously, the existing soil based natural grass field is not currently under-drained and has become hard-packed. Stormwater runoff currently sheet flows from south to north and is collected in catch basins located at the north end of the field. The survey information was inconclusive, but is assumed that an existing catch basin in the northwest corner of the project site bypasses the existing on-site biofiltration swale and conveys stormwater directly to a catch basin located in the northeast corner of the school property. Additionally, several catch basins located in the northwest corner of the project site collect and convey stormwater through a series of conveyance pipes and a biofiltration swale until entering a catch basin located in the northeast corner of the school property (Refer to Figure 5 – Downstream Drainage Map). From this point, the downstream drainage course is described as follows: 1. From the catch basin, stormwater is conveyed east in a 15-inch conveyance pipe for approximately 80-feet until discharging into a catch basin located along Union Avenue NE, outside of the school property. 2. Stormwater is conveyed north in a 24-inch stormwater main for approximately 230 feet prior to discharging into a ditch on the west side of Union Avenue NE. 3. The ditch continues along the west side of Union Avenue NE for at least 150 feet. Renton GIS does not show further infrastructure on the west side of the street, and therefore it is assumed that stormwater is conveyed east at some point via culvert, to the ditch/culvert system on the east side of Union Avenue NE. 4. The ditch and culvert system conveys stormwater north for about 600 feet and enters a culvert southeast of the intersection of Union Avenue NE and SE 95th Way, crossing the ¼-mile point downstream from the site. 5. Stormwater is conveyed beneath SE 95th Way and entering an unnamed stream on the north side of the street. 6. The unnamed stream conveys water north approximately 420 feet, prior to discharging into May Creek. LPD Engineering PLLC Page 8 Sierra Heights Elementary School Playfield Renovations Technical Information Report, June 11, 2021 Task 5 – Mitigation of Existing or Potential Problems It is not anticipated that proposed project will adversely impact the downstream system. The majority of resurfacing is taking place with like materials and no underdrain network of pipes is being added. The grading design will maintain existing topographical patterns and the runoff in the proposed conditions will follow the same downstream drainage path as in the existing condition. SECTION 4 – FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN There is a small amount of concrete pavement proposed to the southwest of the field. Refer to Figure 6 – Proposed Conditions, which shows the proposed site conditions and a summary of the new plus replaced impervious areas. They are summarized in the following table: Table 1 – Target Surfaces Square Feet Acres Concrete Pavement (100% effective impervious) 1,650 sf 0.038 ac Total New Plus Replaced Impervious Area 1,650 sf 0.038 ac Total Target Surface 1,650 sf 0.038 ac This project proposes less than 5,000 square feet of new plus replaced impervious surface and does not involve any new pervious surface. Thus, this project would meet the Basic Exemption for flow control facilities. While water quality treatment is not required because the project does not propose any new plus replaced pollution-generating surfaces, a water quality facility will be provided. This is further described in the Water Quality section of this report. On-site BMP evaluation is required since the project involves more than 7,000 SF of land disturbing activity and will be described in the forthcoming On-site BMP section. Existing Site Hydrology Refer to Section 3 of this report for complete description of the existing hydrology and downstream drainage. Stormwater runoff from the existing grass field sheet flows to a series of catch basins throughout the project area and the stormwater is conveyed east through a series of pipes and catch basin, eventually connecting to storm system along Union Ave NE. The storm system then flows north, which eventually outfalls into a drainage ditch. From the drainage ditch the stormwater runs north for approximately 0.3 miles until joint an unknown creek. The creek then continues to flow north and eventually joins May Creek, approximately 0.4 miles from the project site. Developed Site Hydrology As described previously, the proposed project will involve conversion of the existing soil-based natural grass field to a sand-based natural grass field. The existing grass has been hard packed and storm water currently sheet flows across the field. LPD Engineering PLLC Page 9 Sierra Heights Elementary School Playfield Renovations Technical Information Report, June 11, 2021 To improve the drainage of the field, furrows below the sand base are proposed. These furrows will be filled with pea gravel to allow storm water to infiltrate vertically through the natural turf and sand layer and be captured in the furrows. The furrows will allow the storm water to migrate through the gravel layer and generally be collected in French drains at the extents of the field. Large storm events may continue to flow overland and be collected in the catch basin and pipe system. The proposed system is anticipated to slow storm water flow due to the hydraulic conductivity of this furrowed gravel layer, and will allow the stormwater to have greater residence time with the native subgrade. The discharge from the French drains will also be collected in a catch basin and pipe system and eventually conveyed to the existing piped storm system in the paved play area, east of the field. No flow control facilities or BMP are required, as the target surface amount is beneath the thresholds triggering these requirements. Water Quality System As previously ascertained, water quality treatment is not required, as the project does not involve any new or replaced pollution-generating impervious surfaces (PGIS) or pollution-generating pervious surfaces (PGPS), and would thus meet the Surface Area Exemption outlined in section 1.2.8 of the Renton SWDM. However, the project proposes to implement water quality treatment, since the current natural turf field would be considered a pollution-generating surface. The proposed water quality facility will be a Modular Wetland System, which does have General Use Level Designation (GULD) approval by DOE for enhanced treatment. There are no detention facilities proposed, so the water quality flow is the flow rate from the drainage basin at or below which 91% of the total runoff volume will be treated (section 6.2.1). Sizing of the Modular Wetland System will be conducted by the manufacturer, BioClean. BioClean uses the off-line water quality flow for flow-based sizing, which was found to be 0.042 cubic feet per second (cfs) as determined by MGS Flood. This would result in a 4’x4’ Modular Wetland vault. This preliminary detail and MGS flood report are available for reference in Appendix B. On-Site BMPs Due to the project involving more than 7,000 square feet of land disturbing activity, evaluation of On-site BMPs is required. Section 1.2.9 of the Renton SWDM states the following: “Projects that trigger Core Requirement #9 by disturbing 7,000 square feet or more of land, but where new plus replaced impervious is less than 2,000 square feet, may consider basic dispersion as an equal choice for treating the target impervious surfaces alongside full infiltration, limited infiltration, bioretention, and permeable pavement. These projects are not required to meet the minimum BMP implementation requirements described in “Small Lot BMP Requirements” and “Large Lot BMP Requirements,” (Requirement #5 on both lists), and are not required to comply with Core Requirement #6.” This project meets this condition, and proposes to sheet flow the new pavement area to the southwest, as it will be graded to slope away from the field area. The runoff will be sheet flow dispersed to native vegetation area, and thus fulfill the requirements for Core Requirement #9. LPD Engineering PLLC Page 10 Sierra Heights Elementary School Playfield Renovations Technical Information Report, June 11, 2021 SECTION 5 – CONVEYANCE SYSTEMS ANALYSIS AND DESIGN A conveyance analysis was completed for the outlet from the French drain that eventually connects to the existing on-site drainage system. Conveyance pipes will need to be sized to convey (at a minimum) the 25-year peak flow, per section 1.2.4.1 of the 2017 Renton SWDM. Additionally, the pipes were measured against the 100-year peak flow, as a conservative measure. MGS Flood was used to find the peak flow values (15-minute time steps), which were compared to the full-flow capacity of each pipe found using Manning’s Equation. The Conveyance Analysis Spreadsheet is attached in Appendix B, as well as the output reports from MGS Flood. For the 8-inch outlet from the French drain (Pipe Run #1), the tributary area was entered to reflect the true proposed drainage conditions (see Figure 6). The 8-inch corrugated polyethylene pipe (CPEP), with Manning’s n value of 0.012, at 2.0% slope yields full-flow capacity of 1.86 cubic feet per second (cfs). The 25-year and the 100-year peak flows from MGS Flood were found to be 1.06 cfs and 1.68 cfs respectively. Therefore, this pipe will have adequate capacity for both the 25-year and 100-year storm events. SECTION 6 – SPECIAL REPORTS AND STUDIES A geotechnical report prepared by Associated Earth Sciences, Inc., dated August 21, 2020, is attached in Appendix E of this report. SECTION 7 – OTHER PERMITS An NPDES permit from the Washington State Department of Ecology will be required for the project because it disturbs over one (1) acre of land area. SECTION 8 – CSWPPP 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 the DOE’s Construction Stormwater General Permit SWPPP Template. Also, the Stormwater Pollution Prevention and Spill (SWPPS) report per the KCSWDM is provided in Appendix C. A preliminary SWPPP narrative is attached within Appendix C, while the TESC plan is included in Appendix A of this report. The TESC plan includes temporary sediment settling tanks, sized using the methodology from the 2017 Renton SWDM. A volume of an equivalent sediment trap was calculated to find the necessary volume for a sediment tank for this project. 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. LPD Engineering PLLC Page 11 Sierra Heights Elementary School Playfield Renovations Technical Information Report, June 11, 2021 SECTION 9 – BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT A Bond Quantities Worksheet is not expected to be required by the City of Renton, as the owner is the Renton School District, which is a public agency; no bonding is required. SECTION 10 – OPERATIONS AND MAINTENANCE MANUAL The operations and maintenance guidelines associated with the Modular Wetland System are attached in Appendix D of this report. stormwater covenants for the biopod and interceptor trenches are required. FIGURES Figure 1: TIR Worksheet Figure 2: Vicinity Map Figure 3: Existing Impervious Coverage Figure 4: Soils Map Figure 5: Downstream Drainage Map Figure 6: Proposed Conditions Target Surfaces Figure 7: Proposed Conditions Modeled Areas 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 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 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 1 - N/A turn down elbow prior to modular wetland 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 N/A 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 ballfield fencing & dugouts NE 22 N D CT NE 1 0 6 T H S T WHITMAN CT NE engineering pllc 1932 1st Ave, Suite 201, Seattle, WA 98101 p. 206.725.1211 f. 206.973.5344 www.lpdengineering.com SIERRA HEIGHTS ELEMENTARY SCHOOL PLAYFIELD RENOVATIONS 2VICINITY MAPNEW PORT CT NE126TH AVE SE128TH AVE SEREDMOND AVE NENE 21ST ST WHITMAN AVE NE NE 20TH C TVASHON AVE NENE 22ND PL NE 23RD PL VASHON CT NEO L YM P I A A V E N E NE 22ND PL SE 105TH ST NE 22ND ST REDMOND AVE NEUNION AVE NENE 25TH PLSE 99TH ST WHITMAN AVE NEVASHON CT NEWHITMAN CT NE124TH AVE SENE 25TH ST125TH PL SESE 98TH ST NE 24TH ST SE 101ST ST125TH AVE SEUNION AVE NESE 9 5 T H W A Y126TH PL SESE 96TH PL SE 95T H W A Y SE 95TH WA Y UNNAMEDSE 95TH PL127TH PL SENE 2 4 T H S T SE M A Y C R E E K P A R K D R 1932 1st Ave,Suite 201,Seattle, WA 98101p. 206.725.1211f. 206.973.5344www.lpdengineering.comengineering pllc2021 LPD Engineering PLLC©SIERRA HEIGHTS ELEMENTARY SCHOOL PLAYFIELD RENOVATIONS3EXISTING IMPERVIOUSCOVERAGE engineering pllc 1932 1st Ave, Suite 201 Seattle, WA 98101 p. 206.725.1211 f. 206.973.5344 www.lpdengineering.com 4SOILS MAP SIERRA HEIGHTS ELEMENTARY SCHOOL PLAYFIELD RENOVATIONS NE 22ND PL NE 23RD PL NE 24TH PL NE 25TH PL NE 2 4 T H S T NE 24TH ST UNION AVE NE engineering pllc2020 LPD Engineering PLLC©SIERRA HEIGHTS ELEMENTARY SCHOOL PLAYFIELD RENOVATIONS51932 1st Ave,Suite 201,Seattle, WA 98101p. 206.725.1211f. 206.973.5344www.lpdengineering.comDOWNSTREAMDRAINAGE MAP engineering pllc2021 LPD Engineering PLLC©SIERRA HEIGHTS ELEMENTARY SCHOOL PLAYFIELD RENOVATIONS61932 1st Ave,Suite 201,Seattle, WA 98101p. 206.725.1211f. 206.973.5344www.lpdengineering.comPROPOSED CONDITIONS APPENDIX A Design Drawings APPENDIX B Design Calculations and Supporting Information ————————————————————————————————— MGS FLOOD PROJECT REPORT – WATER QUALITY FLOW Program Version: MGSFlood 4.50 Program License Number: 201410003 Project Simulation Performed on: 06/10/2021 9:32 AM Report Generation Date: 06/10/2021 9:50 AM ————————————————————————————————— Input File Name: Sierra Heights - WQ Flow.fld Project Name: Sierra Heights ES Analysis Title: WQ Flow 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 : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 2.852 2.852 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 2.852 2.852 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Till Grass 2.842 Impervious 0.010 ---------------------------------------------- Subbasin Total 2.852 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Till Grass 2.842 Impervious 0.010 ---------------------------------------------- Subbasin Total 2.852 ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 0 ----------------------SCENARIO: POSTDEVELOPED Number of Links: 1 ********** Link: New Copy Lnk1 ********** 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 0.07 cfs Off-line Design Discharge Rate (91% Exceedance): 0.04 cfs ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Subbasin 1 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 0.328 2-Year 0.328 5-Year 0.539 5-Year 0.539 10-Year 0.759 10-Year 0.759 25-Year 1.060 25-Year 1.060 50-Year 1.420 50-Year 1.420 100-Year 1.675 100-Year 1.675 200-Year 1.763 200-Year 1.763 500-Year 1.878 500-Year 1.878 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals STANDARD DETAIL STORMWATER BIOFILTRATION SYSTEM MWS-L-4-4-V GENERAL NOTES INSTALLATION NOTES SITE SPECIFIC DATA PLAN VIEW ELEVATION VIEW RIGHT END VIEW LEFT END VIEW Sierra Heights Elementary School 6/11/2021 Conveyance Analysis Spreadsheet Pipe Run No.Pipe Run Size Mannings N Plan Slope Qfull Tributary Basins Total Tributary Area Tributary Impervious Area Tributary Pervious Area Qtrib, 25-year (MGS Flood, 15 min) % Full (25-year) Qtrib, 100-year (MGS Flood, 15 min) % Full (100-year) (inches)(ft/ft)(cfs)(acres)(cfs)(cfs) 1 Outlet (French Drain)8 0.012 0.02 1.86 Conveyance Basin, Field & Pavement (see Figure 6) 2.852 0.010 2.842 1.06 57%1.68 90% ————————————————————————————————— MGS FLOOD PROJECT REPORT – CONVEYANCE (FRENCH DRAIN OUTLET) Program Version: MGSFlood 4.50 Program License Number: 201410003 Project Simulation Performed on: 06/10/2021 3:05 PM Report Generation Date: 06/10/2021 3:05 PM ————————————————————————————————— Input File Name: Sierra Heights - French Drain.fld Project Name: Sierra Heights ES Analysis Title: WQ Flow 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 : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 2.852 2.852 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 2.852 2.852 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Till Grass 2.842 Impervious 0.010 ---------------------------------------------- Subbasin Total 2.852 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Till Grass 2.842 Impervious 0.010 ---------------------------------------------- Subbasin Total 2.852 **********************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 ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Subbasin 1 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 0.328 2-Year 0.328 5-Year 0.539 5-Year 0.539 10-Year 0.759 10-Year 0.759 25-Year 1.060 25-Year 1.060 50-Year 1.420 50-Year 1.420 100-Year 1.675 100-Year 1.675 200-Year 1.763 200-Year 1.763 500-Year 1.878 500-Year 1.878 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals Sediment Facility Sizing Calculations Per the 2017 Renton County Surface Water Design Manual Project Name:Sierra Heights Elementary School - Playfield Renovations Required Sediment Trap Surface Area (SA): SA =2*Q/Vsed Where:Q =2-year developed flow rate from MGS Flood Vsed =Settling Velocity (0.00096 ft/sec) Calculation:multiplier =2 Q =0.2500 cfs Vsed =0.00096 fps Required SA =520.8 square feet Equivalent Sediment Trap Volume: Length of Top Surface Area =25 feet Width of Top Surface Area =21 feet Surface Area Provided =525 square feet Side Slope =3 (H:1V) Total Depth of Sediment Trap =3.5 feet Bottom Length of Sediment Trap =4 feet Bottom Width of Sediment Trap =0 feet Total Trap Volume =918.75 cubic feet 6,872 gallons To determine the minimum sediment tank volume, an equivalent sediment trap was sized based upon the required surface area. (2) 4,000 gal Adjustavalve Poly Tanks ————————————————————————————————— MGS FLOOD PROJECT REPORT – TESC SEDIMENT SIZING Program Version: MGSFlood 4.50 Program License Number: 201410003 Project Simulation Performed on: 06/10/2021 4:30 PM Report Generation Date: 06/10/2021 4:38 PM ————————————————————————————————— Input File Name: TESC Sizing.fld Project Name: Sierra Heights ES Analysis Title: Sediment Sizing Comments: ————————————————————————————————— ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Climatic Region Number: 15 Full Period of Record Available used for Routing Precipitation Station : 96004005 Puget East 40 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961040 Puget East 40 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 2.538 2.538 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 2.538 2.538 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Till Grass 2.500 Impervious 0.038 ---------------------------------------------- Subbasin Total 2.538 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : Subbasin 1 ---------- -------Area (Acres) -------- Till Grass 2.500 Impervious 0.038 ---------------------------------------------- Subbasin Total 2.538 **********************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 ***********Compliance Point Results ************* Scenario Predeveloped Compliance Subbasin: Subbasin 1 Scenario Postdeveloped Compliance Subbasin: Subbasin 1 *** 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 0.250 2-Year 0.250 5-Year 0.418 5-Year 0.418 10-Year 0.611 10-Year 0.611 25-Year 0.921 25-Year 0.921 50-Year 1.191 50-Year 1.191 100-Year 1.301 100-Year 1.301 200-Year 1.435 200-Year 1.435 500-Year 1.615 500-Year 1.615 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals APPENDIX C Stormwater Pollution Prevention and Spill Plan (SWPPS) & Construction Stormwater Pollution Prevention Plan (SWPPP) Narrative Page 1 Sierra Heights Elementary School Playfield Renovations Construction SWPPP Narrative June 11, 2021 SIERRA HEIGHTS ELEMENTARY SCHOOL PLAYFIELD RENOVATIONS CONSTRUCTION SWPPP NARRATIVE JUNE 11, 2021 The following Construction Storm Water Pollution Prevention Plan (SWPPP) Narrative is for the Sierra Heights Elementary School grass field improvements at 2501 Union Avenue NE in Renton, Washington. The narrative supplements the Temporary Erosion and Sediment Control (TESC) plan. This narrative has been prepared per Section 3.3.1 of Volume II of the 2014 Department of Ecology (DOE) Stormwater Management Manual for Western Washington. Refer to the TESC plan (Sheet F-0.2) and TESC details and notes (Sheet F-0.3) for more information regarding any erosion or sedimentation control measures involved in this project. 1. CONSTRUCTION STORMWATER POLLUTION PREVENTION ELEMENTS 1) Mark Clearing Limits: The limits of the disturbance are delineated by the “limit of work” line shown on Sheets F-0.2. Areas impacted and not anticipated to be covered with final stabilization measures shall be stabilized using approved TESC methods. 2) Establish Construction Access: The construction entrance will be established via the existing paved play area northeast of the playfield. Construction access can be supplemented with quarry spall construction access (BMP C105) as necessary. The Contractor shall provide wheel wash if necessary. 3) Control Flow Rates: Stormwater flow control during construction is anticipated to be mitigated by routing runoff to a temporary sediment storage tank. Refer to the Sediment Tank Sizing calculations and the MGS Flood output included within Appendix B of the project’s Technical Information Report. The project does not involve permanent flow control facilities. 4) Install Sediment Controls: DOE approved BMPs for sediment controls are shown on the TESC plan. Sediment will be controlled using silt fence (BMP C233) and storm drain inlet protection (BMP C220). 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 unstabilized 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: The 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; Page 2 Sierra Heights Elementary School Playfield Renovations Construction SWPPP Narrative June 11, 2021 C208, Triangular Silt Dike; 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 feet downstream of the site will be protected with storm drain inlet protection (BMP C220). 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: Channels are not proposed as part of this project and BMPs for channel stabilization are not expected. DOE-approved BMPs for channel stabilization include, but are not limited to: C200, Interceptor Dike and Swale; and 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 temporary sump and pump facilities 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 via force mains into the temporary sediment settling tanks. The tanks will be located east of the field area. Construction debris will be removed from the site. The Contractor will be responsible for managing their construction equipment per DOE-approved BMPs. If a truck wheel wash is required, truck wheel wash water and concrete truck washout water shall be collected and discharged to the public sanitary sewer (SS) system. To apply for and obtain a SS release, contact the local sewer purveyors (City of Renton and King County Metro) 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 facility by pumping it out of the excavation. 11) Maintain BMPs: DOE-approved standard BMP maintenance will be required in accordance with the City of Renton Erosion and Sedimentation Control Standard Plan Notes on Sheet F-0.3. 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 City’s direction and the costs assessed as a lien against the property where such facilities are located. Page 3 Sierra Heights Elementary School Playfield Renovations Construction SWPPP Narrative June 11, 2021 2. PROJECT DESCRIPTION This project will involve the conversion of the existing soil-based natural grass field to a sand- based natural grass playfield. To improve the drainage of the field, furrows below the sand base surface will be placed along with pea gravel. A small area of pavement for walkways and dugouts will be installed southwest of the field. Refer to the technical information report for more information. This project is not required to implement flow control facilities or water quality treatment. However, water quality treatment will be proposed with a Modular Wetland System treatment facility. The pavement area southwest of the field will utilize sheet flow dispersion as an On-Site BMP. Refer to the project’s technical information report for more information. Estimated earthwork quantities are to be determined. 3. EXISTING SITE CONDITIONS The project area includes the existing natural grass field is natural grass, with a sand infield in the southwest corner, located west of the main school facilities. The school property includes the main school building and parking lot on the eastern portion of the site. There is a wooded area that includes a constructed wetland on the west end of the parcel. The project area is relatively flat, with the topography of the existing field sloping from south to north, at a grade of approximately 1.5 -2% and dropping about 6 feet across the entire field. There is a small grass hill directly south of the field with slope of about 20%. The adjacent paved play area slopes toward the field at approximately 1%. According to the USDA Natural Resources Conservation Service, the underlying soils for the site is Alderwood gravelly sandy loam, 8 to 15 percent slopes. A small portion of the northern regions of the school property are mapped as consisting of Everett very gravelly sandy loam, 15 to 30 percent slopes (EvD). The site is located within the May Creek Drainage Basin, which is part of the Lake Washington and Cedar River Watershed. Stormwater runoff from the existing grass field sheet flows to a series of catch basins throughout the project area and the stormwater is conveyed east through a series of pipes and catch basin, eventually connecting to storm system along Union Ave NE. The storm system then flows north, and eventually joins May Creek, approximately 0.4 miles from the project site. 4. ADJACENT AREAS The project area is bounded by the paved play area to the east, forested areas to the north and west, and single-family residences to the south. Access to the school site is from Union Ave NE to the east of the school property. 5. CRITICAL AREAS Per the City of Renton GIS, there is a wetland on the west side of the property, outside of the project disturbance area. There are Renton regulated slopes (15-25%) to the south and north of the field. Per the Department of Ecology Water Quality Atlas, May Creek has 303(d) category 5 listings. May Creek has two listings for temperature, one listing for bacteria, and one listing for bioassessment. Page 4 Sierra Heights Elementary School Playfield Renovations Construction SWPPP Narrative June 11, 2021 6. SOILS According to the USDA Natural Resources Conservation Service, the underlying soils for the site is Alderwood gravelly sandy loam, 8 to 15 percent slopes. A small portion of the northern regions of the property are mapped as consisting of Everett very gravelly sandy loam, 15 to 30 percent slopes (EvD). A geotechnical report has been prepared by Associated Earth Sciences, Inc., dated August 21st, 2020. For the geotechnical borings in close proximity to the project area (EB-1 through EB-4), there was encountered fill at varying depths ranging from 6-inches to 19 feet. There was encountered Vashon lodgment till at varying depths ranging from 3.5 to 20.5 feet. No groundwater was encountered during any of the boring explorations. Four onsite hand borings were included in the reports from 2019 (HA-1 through HA-4). Fill was encountered at varying depths ranging from 6-inches to 3.5 feet. 7. POTENTIAL EROSION PROBLEM AREAS The site is not within an erosion hazard area. 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, seasonal work limitation, and runoff control are the most effective methods for reduction of turbidity in stormwater runoff. Any runoff that occurs will be directed to the temporary sump and then pumped to the sediment settling tank. Areas that have not been permanently stabilized will be addressed using DOE-approved BMPs, per the construction documents. 8. CONSTRUCTION PHASING At this time, it is not expected that the project will be formally phased. The contractor is responsible for coordinating work of all subcontractors to keep the duration of site disturbance limited to the maximum extent possible. 9. CONSTRUCTION SCHEDULE Construction is expected to begin in July 2021 and be completed by October 2021. Earthwork activities are not expected to take place in the wet season, October 1st to April 30th. Should any wet weather conditions occur during construction, the contractor shall implement the de-watering procedures outlined in this SWPPP and applicable BMPs including, but not limited to C123, Plastic Covering; C121, Mulching; C122, Nets and Blankets; C126, Polyacrylamide for Soil Erosion Protection; C130, Surface Roughening. Page 5 Sierra Heights Elementary School Playfield Renovations Construction SWPPP Narrative June 11, 2021 10. FINANCIAL/OWNERSHIP RESPONSIBILITIES This 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 School District, and 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 Technical Information Report. Page 1 Sierra Heights Elementary School Playfield Renovations Stormwater Pollution Prevention and Spill Plan June 11, 2021 SIERRA HEIGHTS ELEMENTARY SCHOOL PLAYFIELD RENOVATIONS STORMWATER POLLUTION PREVENTION AND SPILL PLAN JUNE 11, 2021 The following report is in accordance with the 2017 Renton Surface Water Design Manual (SWDM) Section 2.3.1.4 for the Stormwater Pollution Prevention and Spill (SWPPS) Plan. The following is a summary of the items to be addressed on the TESC Plan of the contract documents and an indication of their applicability to this project. PART A: ACTIVITY SPECIFIC INFORMATION REQUIRED Storage and Handling of Liquids: No petroleum products, fuel, solvents, detergents, paint, pesticides, and concrete admixtures are expected to be stored on site. There may be small quantities of paint or form oil stored on site during construction. They are expected to be stored in a protected area such as inside a construction trailer, or inside a fenced enclosure in the contractor’s work area. Exact quantities and storage locations are not known at this time. Storage and Stockpiling of Construction Materials and Wastes: Construction materials and waste may be stockpiled temporarily but shall be hauled off regularly. Refer to Note 2 below for additional information. Fueling: No stationary fuel tank will be allowed on site during construction. Fueling will be allowed on site during daylight hours only by a mobile fuel truck, and only in paved areas. Refer to notes 3, 4, and 5 below for additional information. Maintenance, Repairs, and Storage of Vehicles and Equipment: Equipment that requires significant repair will be removed from the site to repair. Minor repairs or maintenance may be allowed on site only in an approved area. Refer to note 6 below for additional information. Concrete Saw Cutting, Slurry, and Washwater Disposal: All concrete saw-cutting slurry, as well as rinsing of tools, shall be controlled such that it does not contaminate on-site stormwater. Concrete truck washout will not be allowed on site. Refer to note 7 below. Page 2 Sierra Heights Elementary School Playfield Renovations Stormwater Pollution Prevention and Spill Plan June 11, 2021 Handling of pH Elevated Water: Because construction stormwater runoff will be routed to a sediment settling tank(s), monitoring for elevated pH can be conducted as necessary by sampling from the tank. Application of Chemicals including Pesticides and Fertilizers: No chemicals are expected to be used in this project. PART B: SWPPS SITE PLAN Refer to Sheet F-0.4 of the drawings. Also, per Section 2.3.1.4.B of the Renton SWDM: 1. Liquids including petroleum products, fuel, solvents, detergents, pesticides, and concrete admixtures are not anticipated to be stored on site. If products such as fuel are required, these items will be brought in small quantities, used, and removed from the site. Items such as paint or form oils, if needed, will be delivered to the site in small quantities and stored inside a construction trailer prior to use. A note is included on the plan as follows: “No hazardous liquid products including but not limited to petroleum products, fuel, solvents, detergents, paint, pesticides, concrete admixtures and form oils shall be stored on-site without prior approval. If requested, the Contractor shall provide for spill containment in accordance with King County and the City of Renton requirements. Contractor shall provide a list of the types and sizes of liquids that will be stored/handled on site. Contractor will also show the proposed location for storage on a project site plan and will provide a proposed method of secondary containment. The Owner’s Representative and the City shall review and approve the plan prior to storage.” 2. Construction waste will be limited on this site due to the limited scope of removals. The proposed improvements will not require demolition of any existing buildings. Any demolished material will be removed immediately upon demolition. This project has no hazardous material to be removed. All pollutants, including waste materials and demolition debris, that occur onsite shall be handled and disposed of in a manner that does not cause contamination of stormwater. Good housekeeping and preventative measures will be taken to ensure that the site will be kept clean, well-organized, and free of debris. A note is included in the SWPPS notes as follows: “Construction waste shall be promptly removed from the site and shall not be stockpiled.” 3. No stationary tanks will be used for this project. A note is included in the SWPPS notes as follows: “No stationary fuel tank shall be allowed.” 4. If required, a mobile fuel truck will be brought to the site to fuel the excavation equipment. A note is included in the SWPPS notes as follows: “Fueling of construction equipment shall be by a mobile fuel truck and shall be allowed only in paved areas. Contractor shall provide a plan for fueling area spill containment to the Owner’s Representative and the City of Renton with a proposed method of secondary containment. The Owner’s Representative and the City of Renton shall Page 3 Sierra Heights Elementary School Playfield Renovations Stormwater Pollution Prevention and Spill Plan June 11, 2021 review and approve the plan prior to fueling. All spills, containment, and clean up shall be the contractor’s responsibility and at their own expense.” 5. Equipment will only be fueled during daylight hours. A note is included in the SWPPS notes as follows: “Fueling of construction equipment shall only be allowed during daylight hours.” 6. Equipment that requires significant repair will be removed from the site to repair. Minor repairs or maintenance may be allowed on site only in an approved area. A note is included in the SWPPS notes as follows: “The Contractor shall remove from the site all equipment that requires significant repair. Minor repairs or maintenance may be allowed on site in an approved area. The Contractor shall submit a plan for the proposed location of vehicle maintenance and repair and shall indicate the proposed method of containment for possible leaking vehicle fluids. The contractor shall also provide a plan to the Owner’s Representative and the City of Renton for the collection, storage, and disposal of the vehicle fluids. The Owner’s Representative and the City of Renton shall review and approve plan prior to any on-site maintenance.” 7. Truck washout will not be allowed on site. A note is included in the SWPPS notes as follows: “Truck washout shall not be allowed on site. The Contractor shall provide truck washout off-site at an approved and legal location.” 8. No chemicals are anticipated to be required for this project. 9. Selected Contractor shall provide location for spill response materials, and identify disposal methods for contaminated water and soil. A note is included in the SWPPS notes as follows: “Contractor shall provide to the Owner’s Representative and the City of Renton the location of spill response materials. Contractor will also identify disposal methods for contaminated water and soil after a spill.” PART C: POLLUTION PREVENTION REPORT The project will be publicly bid thus no excavation contractor is currently under contract. The possible sources of pollution are limited and are addressed above. In addition to the above information provided on the contract documents, the following notes are included to specifically address pollution prevention: • “The Contractor shall provide a report to the Owner’s Representative and the City of Renton identifying the personnel responsible for pollution prevention, including contact information, and clearly listing the responsibilities of these personnel.” • “The Contractor shall also provide a description of the procedures to be used in monitoring the pollution prevention BMPs and responding to a BMP that needs attention, including record keeping.” PART D: SPILL PREVENTION AND CLEANUP REPORT Due to the public bid process, an earthwork subcontractor is not yet under contract for Page 4 Sierra Heights Elementary School Playfield Renovations Stormwater Pollution Prevention and Spill Plan June 11, 2021 this project. The personnel responsible for spill prevention and cleanup will be identified at the pre-construction meeting for the project. Spill prevention is addressed with notes on the contract documents as stated above. The sources of potential spills are limited and have been addressed on the plan with notes. In addition to the above information provided on the contract documents, the following notes have been added in the SWPPS notes to specifically address spill prevention: • “The Contractor shall provide a report to the Owner’s Representative and the City of Renton identifying the personnel responsible for spill prevention, including contact information, and clearly listing the responsibilities of these personnel.” • “The Contractor shall provide a description of the procedures to be used in monitoring the spill prevention BMPs and responding to a spill incident, including record keeping.” APPENDIX D Operations and Maintenance Gudelines www.modularwetlands.com Maintenance Guidelines for Modular Wetland System - Linear Maintenance Summary o Remove Trash from Screening Device – average maintenance interval is 6 to 12 months.  (5 minute average service time). o Remove Sediment from Separation Chamber – average maintenance interval is 12 to 24 months.  (10 minute average service time). o Replace Cartridge Filter Media – average maintenance interval 12 to 24 months.  (10-15 minute per cartridge average service time). o Replace Drain Down Filter Media – average maintenance interval is 12 to 24 months.  (5 minute average service time). o Trim Vegetation – average maintenance interval is 6 to 12 months.  (Service time varies). System Diagram Access to screening device, separation chamber and cartridge filter Access to drain down filter Pre-Treatment Chamber Biofiltration Chamber Discharge Chamber Outflow Pipe Inflow Pipe (optional) www.modularwetlands.com Maintenance Procedures Screening Device 1. Remove grate or manhole cover to gain access to the screening device in the Pre- Treatment Chamber. Vault type units do not have screening device. Maintenance can be performed without entry. 2. Remove all pollutants collected by the screening device. Removal can be done manually or with the use of a vacuum truck. The hose of the vacuum truck will not damage the screening device. 3. Screening device can easily be removed from the Pre-Treatment Chamber to gain access to separation chamber and media filters below. Replace grate or manhole cover when completed. Separation Chamber 1. Perform maintenance procedures of screening device listed above before maintaining the separation chamber. 2. With a pressure washer spray down pollutants accumulated on walls and cartridge filters. 3. Vacuum out Separation Chamber and remove all accumulated pollutants. Replace screening device, grate or manhole cover when completed. Cartridge Filters 1. Perform maintenance procedures on screening device and separation chamber before maintaining cartridge filters. 2. Enter separation chamber. 3. Unscrew the two bolts holding the lid on each cartridge filter and remove lid. 4. Remove each of 4 to 8 media cages holding the media in place. 5. Spray down the cartridge filter to remove any accumulated pollutants. 6. Vacuum out old media and accumulated pollutants. 7. Reinstall media cages and fill with new media from manufacturer or outside supplier. Manufacturer will provide specification of media and sources to purchase. 8. Replace the lid and tighten down bolts. Replace screening device, grate or manhole cover when completed. Drain Down Filter 1. Remove hatch or manhole cover over discharge chamber and enter chamber. 2. Unlock and lift drain down filter housing and remove old media block. Replace with new media block. Lower drain down filter housing and lock into place. 3. Exit chamber and replace hatch or manhole cover. www.modularwetlands.com Maintenance Notes 1. Following maintenance and/or inspection, it is recommended the maintenance operator prepare a maintenance/inspection record. The record should include any maintenance activities performed, amount and description of debris collected, and condition of the system and its various filter mechanisms. 2. The owner should keep maintenance/inspection record(s) for a minimum of five years from the date of maintenance. These records should be made available to the governing municipality for inspection upon request at any time. 3. Transport all debris, trash, organics and sediments to approved facility for disposal in accordance with local and state requirements. 4. Entry into chambers may require confined space training based on state and local regulations. 5. No fertilizer shall be used in the Biofiltration Chamber. 6. Irrigation should be provided as recommended by manufacturer and/or landscape architect. Amount of irrigation required is dependent on plant species. Some plants may require irrigation. www.modularwetlands.com Maintenance Procedure Illustration Screening Device The screening device is located directly under the manhole or grate over the Pre-Treatment Chamber. It’s mounted directly underneath for easy access and cleaning. Device can be cleaned by hand or with a vacuum truck. Separation Chamber The separation chamber is located directly beneath the screening device. It can be quickly cleaned using a vacuum truck or by hand. A pressure washer is useful to assist in the cleaning process. www.modularwetlands.com Cartridge Filters The cartridge filters are located in the Pre-Treatment chamber connected to the wall adjacent to the biofiltration chamber. The cartridges have removable tops to access the individual media filters. Once the cartridge is open media can be easily removed and replaced by hand or a vacuum truck. Drain Down Filter The drain down filter is located in the Discharge Chamber. The drain filter unlocks from the wall mount and hinges up. Remove filter block and replace with new block. www.modularwetlands.com Trim Vegetation Vegetation should be maintained in the same manner as surrounding vegetation and trimmed as needed. No fertilizer shall be used on the plants. Irrigation per the recommendation of the manufacturer and or landscape architect. Different types of vegetation requires different amounts of irrigation. www.modularwetlands.com Inspection Form Modular Wetland System, Inc. P. 760.433-7640 F. 760-433-3176 E. Info@modularwetlands.com For Office Use Only (city) (Zip Code)(Reviewed By) Owner / Management Company (Date) Contact Phone ( )_ Inspector Name Date / / Time AM / PM Weather Condition Additional Notes Yes Depth: Yes No Modular Wetland System Type (Curb, Grate or UG Vault):Size (22', 14' or etc.): Other Inspection Items: Storm Event in Last 72-hours? No Yes Type of Inspection Routine Follow Up Complaint Storm Office personnel to complete section to the left. 2972 San Luis Rey Road, Oceanside, CA 92058 P (760) 433-7640 F (760) 433-3176 Inspection Report Modular Wetlands System Is the filter insert (if applicable) at capacity and/or is there an accumulation of debris/trash on the shelf system? Does the cartridge filter media need replacement in pre-treatment chamber and/or discharge chamber? Any signs of improper functioning in the discharge chamber? Note issues in comments section. Chamber: Is the inlet/outlet pipe or drain down pipe damaged or otherwise not functioning properly? Structural Integrity: Working Condition: Is there evidence of illicit discharge or excessive oil, grease, or other automobile fluids entering and clogging the unit? Is there standing water in inappropriate areas after a dry period? Damage to pre-treatment access cover (manhole cover/grate) or cannot be opened using normal lifting pressure? Damage to discharge chamber access cover (manhole cover/grate) or cannot be opened using normal lifting pressure? Does the MWS unit show signs of structural deterioration (cracks in the wall, damage to frame)? Project Name Project Address Inspection Checklist CommentsNo Does the depth of sediment/trash/debris suggest a blockage of the inflow pipe, bypass or cartridge filter? If yes, specify which one in the comments section. Note depth of accumulation in in pre-treatment chamber. Is there a septic or foul odor coming from inside the system? Is there an accumulation of sediment/trash/debris in the wetland media (if applicable)? Is it evident that the plants are alive and healthy (if applicable)? Please note Plant Information below. Sediment / Silt / Clay Trash / Bags / Bottles Green Waste / Leaves / Foliage Waste:Plant Information No Cleaning Needed Recommended Maintenance Additional Notes: Damage to Plants Plant Replacement Plant Trimming Schedule Maintenance as Planned Needs Immediate Maintenance www.modularwetlands.com Maintenance Report Modular Wetland System, Inc. P. 760.433-7640 F. 760-433-3176 E. Info@modularwetlands.com For Office Use Only (city) (Zip Code)(Reviewed By) Owner / Management Company (Date) Contact Phone ( )_ Inspector Name Date / / Time AM / PM Weather Condition Additional Notes Site Map # Comments: 2972 San Luis Rey Road, Oceanside, CA 92058 P. 760.433.7640 F. 760.433.3176 Inlet and Outlet Pipe Condition Drain Down Pipe Condition Discharge Chamber Condition Drain Down Media Condition Plant Condition Media Filter Condition Long: MWS Sedimentation Basin Total Debris Accumulation Condition of Media 25/50/75/100 (will be changed @ 75%) Operational Per Manufactures' Specifications (If not, why?) Lat:MWS Catch Basins GPS Coordinates of Insert Manufacturer / Description / Sizing Trash Accumulation Foliage Accumulation Sediment Accumulation Type of Inspection Routine Follow Up Complaint Storm Storm Event in Last 72-hours? No Yes Office personnel to complete section to the left. Project Address Project Name Cleaning and Maintenance Report Modular Wetlands System APPENDIX E Geotechnical Report associated earth sciences incorporated Associated Earth Sciences, Inc. 911 5th Avenue Kirkland, WA 98033 P (425) 827 7701 Subsurface Exploration and Preliminary Geotechnical Engineering Report SIERRA HEIGHTS ELEMENTARY SCHOOL PLAYFIELD UPGRADE Renton, Washington Prepared For: D.A. HOGAN & ASSOCIATES, INC. Project No. 20200141E001 August 21, 2020 Kirkland | Tacoma | Mount Vernon 425-827-7701 | www.aesgeo.com August 21, 2020 Project No. 20200141E001 D.A. Hogan & Associates, Inc. 119 1st Avenue South, Suite #110 Seattle, Washington 98104 Attention: Mr. Eric Gold Subject: Subsurface Exploration and Preliminary Geotechnical Engineering Report Sierra Heights Elementary School Playfield Upgrade 2501 Union Avenue NE Renton, Washington Dear Mr. Gold: Associated Earth Sciences, Inc. (AESI) is pleased to present the enclosed copies of our geotechnical engineering report for the referenced project. This report summarizes the results of our subsurface exploration and geotechnical engineering studies and offers geotechnical engineering recommendations for the preliminary design of the proposed project. 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 us 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. Associate Geologist BWG/ld 20200141E001-2 SUBSURFACE EXPLORATION AND PRELIMINARY GEOTECHNICAL ENGINEERING REPORT SIERRA HEIGHTS ELEMENTARY SCHOOL PLAYFIELD UPGRADE Renton, Washington Prepared for: D.A. Hogan & Associates, Inc. 119 1st Avenue South, Suite #110 Seattle, Washington 98104 Prepared by: Associated Earth Sciences, Inc. 911 5th Avenue Kirkland, Washington 98033 425-827-7701 August 21, 2020 Project No. 20200141E001 Sierra Heights Elementary School Subsurface Exploration and Playfield Upgrade Preliminary Geotechnical Engineering Report Renton, Washington Project and Site Conditions August 21, 2020 ASSOCIATED EARTH SCIENCES, INC. PEL/ld - 20200141E001-2 Page 1 I. PROJECT AND SITE CONDITIONS 1.0 INTRODUCTION This report presents the results of our subsurface exploration and preliminary geotechnical engineering studies for the proposed Sierra Heights Elementary School playfield improvements. The site location is shown on the “Vicinity Map,” Figure 1. Existing site features, and the approximate locations of the subsurface explorations referenced in this study are presented on the “Existing Site and Exploration Plan,” Figure 2. This report is based on a preliminary project description provided to us by D.A. Hogan & Associates, Inc. (D.A. Hogan), the field designer. At the time this report was written, no detailed plans had been formulated for the current athletic field renovations project. 1.1 Purpose and Scope The purpose of this study was to provide subsurface soil and shallow groundwater data to be utilized in the preliminary design of the proposed Sierra Heights Elementary School playfield improvements. Our study included a review of selected available geologic literature, completing four hollow-stem auger soil borings, and performing geologic studies to assess the type, thickness, distribution, and physical properties of the subsurface sediments and shallow groundwater. Logs of four hand-auger borings completed by Associated Earth Sciences, Inc. (AESI) within the current project limits in 2019 were reviewed, and are included with this report. Laboratory testing of grain-size distribution was completed on two selected samples retrieved from the borings and results of the laboratory tests are included in the Appendix. A preliminary geotechnical engineering study was completed to formulate recommendations regarding site preparation, structural fill, subgrade preparation, and general recommendations for site drainage design. This report summarizes our current fieldwork and offers development recommendations based on our present understanding of the project. 1.2 Authorization Our study was accomplished in general accordance with our proposal dated April 15, 2020. We were authorized to proceed by means of a subconsultant agreement with D.A. Hogan. This report has been prepared for the exclusive use of D.A. Hogan 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. Sierra Heights Elementary School Subsurface Exploration and Playfield Upgrade Preliminary Geotechnical Engineering Report Renton, Washington Project and Site Conditions August 21, 2020 ASSOCIATED EARTH SCIENCES, INC. PEL/ld - 20200141E001-2 Page 2 2.0 PROJECT AND SITE DESCRIPTION The project site consists of an existing natural turf playfield and loam ballfield to the west of the existing school buildings. The project area is approximately rectangular and measures approximately 330 feet north to south and 355 feet east to west. The existing field generally slopes down toward the north, with overall vertical relief across the project area of approximately 5 to 10 feet based on King County iMap aerial topographic data. The King County topographic data indicates that a portion of the north margin of the playfield is located near the top of a steep slope that is located on the adjoining property to the north. The proposed project would include installation of an underdrained natural turf playfield replacing the existing grass playfield. We anticipate that the new field will be constructed close to existing grade without deep earthwork excavations or thick fills. No walls or structures are anticipated. Stormwater infiltration feasibility is a key element for project planning and if infiltration is feasible the project will include infiltration facilities. 3.0 SITE EXPLORATION Our field studies for this project were conducted in July of 2020 and included four hollow-stem auger borings at the locations shown on Figure 2. Logs of our borings, labeled EB-1 to EB-4, are included with this report. The borings were completed by advancing a 3-inch inside-diameter, hollow-stem auger with a track-mounted drill rig. During the drilling process, samples were obtained at generally 2.5- to 5-foot-depth intervals. The exploration borings were continuously observed and logged by an engineering geologist from our firm. The various types of soils, as well as the depths where characteristics of the soils changed, are indicated on the exploration logs presented in the Appendix of this report. The exploration logs presented in the Appendix are based on the field logs, drilling action, and inspection of the samples secured. Our explorations were approximately located by measuring from known site features shown on the drawing that was provided to us. Because of the nature of exploratory work, extrapolation of subsurface conditions between field explorations is necessary. Differing subsurface conditions may be present due to the random nature of natural sediment deposition and the alteration of topography by past grading and filling. The nature and extent of any variations between the field explorations may not become fully evident until construction. If variations are observed at the time of construction, it may be necessary to re-evaluate specific recommendations in this report and make appropriate changes. Sierra Heights Elementary School Subsurface Exploration and Playfield Upgrade Preliminary Geotechnical Engineering Report Renton, Washington Project and Site Conditions August 21, 2020 ASSOCIATED EARTH SCIENCES, INC. PEL/ld - 20200141E001-2 Page 3 Disturbed, but representative samples were obtained by using the modified Standard Penetration Test (SPT) procedure. This test and sampling method consists of driving a 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 and laboratory testing, as necessary. 3.1 Previous Geotechnical Studies by AESI In 1993, AESI completed a geotechnical engineering study in support of design for a school expansion project, resulting in the buildings that now exist onsite. The 1993 study included several borings around the building footprint (at the time of the study) but none within the current project area. Borings completed onsite in 1993 generally encountered existing fill over Vashon lodgement till sediments. A more recent limited geotechnical study was conducted in the current project footprint by AESI in 2019. The 2019 study was a feasibility study related to creating a constructed wetland at Sierra Heights Elementary School to compensate for wetland impacts on a different District-owned property. The 2019 study included four hand borings within the current project area. The locations of the 2019 hand borings are noted alongside the new exploration locations on Figure 2. The 2019 hand boring logs are included in the Appendix. 4.0 SUBSURFACE CONDITIONS Subsurface conditions on the project site were inferred from the field explorations conducted for this study, review of previously completed subsurface explorations included in this report, visual reconnaissance of the site, and a review of selected applicable geologic literature. As shown on the field logs, all of our exploration borings encountered surficial fill. Observed fill depths are depicted on exploration logs in the Appendix. Below the fill, all of our exploration borings encountered dense to very dense silty sand with gravels which were interpreted as lodgement till. Sierra Heights Elementary School Subsurface Exploration and Playfield Upgrade Preliminary Geotechnical Engineering Report Renton, Washington Project and Site Conditions August 21, 2020 ASSOCIATED EARTH SCIENCES, INC. PEL/ld - 20200141E001-2 Page 4 4.1 Stratigraphy Sod and Topsoil All of the borings encountered existing natural turf approximately 2 to 3 inches thick. Natural turf within the existing field was underlain by 2 to 4 inches of roots and highly organic topsoil. Fill All four exploration borings and all four hand-auger borings depicted on Figure 2 encountered existing fill that was observed to be between 2 and 19 feet thick with the exception of HA-3 and HA-4 where fill was not fully penetrated and therefore the existing fill depth is unknown. The existing fill was typically loose to medium dense and typically consisted of silty sand with gravel and variable organic content. One should refer to the exploration logs attached with this report for more detailed information regarding the texture, density, and moisture content of the existing fill observed in our explorations. Vashon Lodgement Till All explorations that fully penetrated existing fill encountered dense to very dense sand with silt and gravel interpreted as lodgement till sediments. Lodgement till was deposited at the base of an active continental glacier and was subsequently compacted by the weight of the overlying glacial ice. Lodgement till typically possesses high-strength and low-compressibility attributes that are favorable for support of athletic fields. Lodgement till is silty and moisture-sensitive. In the presence of moisture contents above the optimum moisture content for compaction purposes, lodgement till can be easily disturbed by vehicles and earthwork equipment. Reuse of excavated lodgement till sediments in structural fill applications is feasible if such reuse is explicitly allowed by project specifications, and if the material is dried to achieve a moisture condition such that it can be compacted to a firm and unyielding condition at the specified level of compaction. 4.2 Laboratory Testing We selected two of our exploration boring samples for mechanical grain-size analysis testing, including samples of the fill and native soils encountered in EB-3. The results of the laboratory analysis are contained in the Appendix and summarized below in Table 1 with soil descriptions based on ASTM International (ASTM) D-2487 Unified Soil Classification System (USCS). Sierra Heights Elementary School Subsurface Exploration and Playfield Upgrade Preliminary Geotechnical Engineering Report Renton, Washington Project and Site Conditions August 21, 2020 ASSOCIATED EARTH SCIENCES, INC. PEL/ld - 20200141E001-2 Page 5 Table 1 Summary of Grain-Size Analysis Exploration Number Depth (feet) Geologic Unit USCS Soil Description Fines Content (%) EB-3 2.5 Fill Very Silty Fine SAND Trace Gravel (SM) 38 EB-3 10 Lodgment Till Very Silty Fine SAND Trace Gravel (SM) 35 USCS = Unified Soil Classification System % = percent of total weight passing the U.S. No. 200 Sieve 4.3 Hydrology With the exception of EB-2, groundwater was not observed in our explorations. A significant increase of moisture was noted at a depth of approximately 15 feet during sampling of EB-2 but taking into consideration the scope of work as well as the absence of groundwater in borings EB-1, EB-3, and EB-4, we do not expect any significant groundwater will be encountered at the time of construction. Shallow perched groundwater may be encountered in existing fill where it is underlain by lodgement till. Perched groundwater commonly occurs when surface water infiltrates down through relatively permeable soils, such as the topsoil/fill and becomes trapped or “perched” atop a comparatively impermeable barrier, such as the Vashon lodgement till sediments. Groundwater conditions, including depth and duration and quantity of seepage, should be expected to vary seasonally, and in response to changes in precipitation, soil grain-size distribution, topography, on- and off-site land usage, and other factors. 4.4 Regional Geologic Mapping We reviewed published geologic maps of the area (H.H. Waldron, B.A. Leisch, D.R. Mullineaux, and D.R. Crandell, 1961, Preliminary Geologic Map of Seattle and Vicinity, Washington: U.S. Geological Survey [USGS], Open-File Report OF-61-168, scale 1:24,000 and M.A. Jones, 1999, Geologic Framework for the Puget Sound Aquifer System, Washington and British Colombia, USGS Professional Paper PP-1424-C, scale 1:100,000). The referenced maps indicate that the site vicinity is underlain by Vashon lodgement till at shallow depths, with advance outwash mapped nearby at slightly lower elevations. Our interpretation of the sediments encountered in our explorations is in general agreement with the regional geologic mapping in that Vashon lodgement till was encountered beneath fill. Sierra Heights Elementary School Subsurface Exploration and Playfield Upgrade Preliminary Geotechnical Engineering Report Renton, Washington Geologic Hazards and Mitigations August 21, 2020 ASSOCIATED EARTH SCIENCES, INC. PEL/ld - 20200141E001-2 Page 6 II. GEOLOGIC HAZARDS AND MITIGATIONS The following discussion of potential geologic hazards is based on the geologic, slope, and ground and surface water conditions, as observed and discussed herein. 5.0 STEEP SLOPE HAZARDS AND MITIGATIONS The Renton Municipal Code (RMC 4-3-050.G.5) defines Steep Slopes and Landslide Hazards as the following: a. Steep Slope Types: i. Sensitive Slopes: A hillside, or portion thereof, characterized by: (a) an average slope of twenty five percent (25%) to less than forty percent (40%) as identified in the City of Renton Steep Slope Atlas or in a method approved by the City; or (b) an average slope of forty percent (40%) or greater with a vertical rise of less than fifteen feet (15') as identified in the City of Renton Steep Slope Atlas or in a method approved by the City; (c) abutting an average slope of twenty five percent (25%) to forty percent (40%) as identified in the City of Renton Steep Slope Atlas or in a method approved by the City. This definition excludes engineered retaining walls. ii. Protected Slopes: A hillside, or portion thereof, characterized by an average slope of forty percent (40%) or greater grade and having a minimum vertical rise of fifteen feet (15') as identified in the City of Renton Steep Slope Atlas or in a method approved by the City. b. Landslide Hazards: i. Low Landslide Hazard (LL): Areas with slopes less than fifteen percent (15%). ii. Medium Landslide Hazard (LM): Areas with slopes between fifteen percent (15%) and forty percent (40%) and underlain by soils that consist largely of sand, gravel or glacial till. iii. High Landslide Hazards (LH): Areas with slopes greater than forty percent (40%), and areas with slopes between fifteen percent (15%) and forty percent (40%) and underlain by soils consisting largely of silt and clay. iv. Very High Landslide Hazards (LV): Areas of known mapped or identified landslide deposits. Sierra Heights Elementary School Subsurface Exploration and Playfield Upgrade Preliminary Geotechnical Engineering Report Renton, Washington Geologic Hazards and Mitigations August 21, 2020 ASSOCIATED EARTH SCIENCES, INC. PEL/ld - 20200141E001-2 Page 7 Review of the City of Renton Steep Slope Atlas indicates that the slope along the northern edge of the project area is inclined between 15 to 25% with smaller areas inclined between 25 and 40%. Review of King County iMap topographic data indicates that these slopes are generally inclined at approximately 10 to 18%. City code only requires critical areas buffers for Very High Landslide Areas, and only requires structural setbacks for Very High Landslide Hazard Areas and Protected Slopes. The site does not contain either of these slope classifications, and therefore we do not anticipate that slope-related buffers or setbacks are required for the project as currently proposed. 6.0 SEISMIC HAZARDS AND MITIGATIONS Earthquakes occur regularly in the Puget Lowland. The majority of these events are small and are usually not felt by people. However, large earthquakes do occur, as evidenced by the 1949, 7.2-magnitude event; the 1965, 6.5-magnitude event; and the 2001, 6.8-magnitude event. 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 three types of potential geologic hazards associated with large seismic events: 1) surficial ground rupture, 2) liquefaction, and 3) 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. Current research indicates that surficial ground rupture is possible in areas close to the Seattle Fault Zone, the closest known fault zone to the project site. The site is approximately ¼ mile south of the mapped limits of the Seattle Fault Zone. In our opinion, the risk of surficial ground rupture at the site due to seismic faulting is low due its proximity to known fault zones. 6.2 Liquefaction Liquefaction is a process through which unconsolidated soil loses strength as a result of vibratory shaking, such as that which occurs during a seismic event. During normal conditions, the weight of the soil is supported by both grain-to-grain contacts and by the 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 decrease in soil shear Sierra Heights Elementary School Subsurface Exploration and Playfield Upgrade Preliminary Geotechnical Engineering Report Renton, Washington Geologic Hazards and Mitigations August 21, 2020 ASSOCIATED EARTH SCIENCES, INC. PEL/ld - 20200141E001-2 Page 8 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 clean sand or coarse silt with low relative densities accompanied by a shallow water table. In our opinion, the potential risk of damage to the proposed development by liquefaction is low due to the high relative density of the underlying sediments and the absence of adverse groundwater conditions. No detailed quantitative liquefaction assessment was completed as part of this study, and none is warranted, in our opinion. 6.3 Ground Motion/Seismic Site Class (2018 International Building Code) We recommend that the project be designed in accordance with seismic Site Class D in accordance with the 2018 International Building Code (IBC) standards, and the publication American Society of Civil Engineers (ASCE) 7 referenced therein, the most recent version of which is ASCE 7-10. 7.0 EROSION HAZARDS AND MITIGATIONS The Renton Municipal Code (RMC 21A.06.415) defines Erosion Hazard Areas as the following: c. Erosion Hazards: i. Low Erosion Hazard (EL): Areas with soils characterized by the Natural Resource Conservation Service (formerly U.S. Soil Conservation Service) as having slight or moderate erosion potential, and a slope less than fifteen percent (15%). ii. High Erosion Hazard (EH): Areas with soils characterized by the Natural Resource Conservation Service (formerly U.S. Soil Conservation Service) as having severe or very severe erosion potential, and a slope more than fifteen percent (15%). Review of the web-based U.S. Department of Agriculture Natural Resources Conservation Service Web Soil Survey indicates that the site is underlain by Urban Land-Alderwood Complex, situated on slopes ranging from 8 to 15 percent. This soil has an erosivity rating of slight to moderate. The site meets the code requirements to be classified as a Low Erosion Hazard Area. The on-site soils contain a significant amount of fine sand and silt that are prone to erosion during construction. To mitigate the construction site erosion potential, project plans should include implementation of temporary erosion controls in accordance with local standards of practice. Control methods should include limiting mass earthwork to seasonally drier periods, typically Sierra Heights Elementary School Subsurface Exploration and Playfield Upgrade Preliminary Geotechnical Engineering Report Renton, Washington Geologic Hazards and Mitigations August 21, 2020 ASSOCIATED EARTH SCIENCES, INC. PEL/ld - 20200141E001-2 Page 9 April 1 to October 31, 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 possible 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 and track-out onto streets should be avoided. 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. Sierra Heights Elementary School Subsurface Exploration and Playfield Upgrade Preliminary Geotechnical Engineering Report Renton, Washington Preliminary Design Recommendations August 21, 2020 ASSOCIATED EARTH SCIENCES, INC. PEL/ld - 20200141E001-2 Page 10 III. PRELIMINARY DESIGN RECOMMENDATIONS 8.0 INTRODUCTION In our opinion, the proposed playfield improvements are feasible from a geotechnical engineering standpoint, provided that the recommendations contained in this report are incorporated into the design. The existing fill is relatively loose and presents some risk of greater than normal post-construction settlement. The recommendations contained in this report are intended to reduce the potential for post-construction settlement, but not eliminate it. Elimination of all risk of greater than normal post-construction settlement is not expected to be economically feasible due to the depth of the existing fill soils that are potentially prone to consolidation and settlement. The settlement risk mitigation measures recommended in this report are expected to be reasonable to implement and economically viable, but more elaborate settlement risk mitigation measures are possible. We are available to discuss more aggressive settlement risk mitigation strategies and costs on request. The risk of post-construction settlement at this site is difficult to quantify with the existing data, but is expected to be relatively small, on the order of a few inches or less. Grain-size testing completed for this study suggests that subsurface soils at this site can be expected to drain slowly, and therefore, an underdrain system for the new improvements is warranted and stormwater infiltration is not recommended. 9.0 TEMPORARY EROSION AND SEDIMENTATION CONTROL The site includes areas that meet City of Renton criteria for treatment as Erosion Hazard Areas. The following discussion addresses Washington State Department of Ecology (Ecology) erosion control regulations that will be applicable to the project. We anticipate that if the project complies with Washington State requirements, it will also be acceptable with respect to City of Renton requirements. The most recent Ecology Construction Storm Water General Permit, issued November 18, 2015, (also known as the National Pollutant Discharge Elimination System [NPDES] permit) requires weekly Temporary Erosion and Sedimentation Control (TESC) inspections and turbidity and pH monitoring for all sites 1 or more acres in size that discharge stormwater to surface waters of the state. Because we anticipate that the proposed project will require disturbance of more than 1 acre, we anticipate that these inspection and reporting requirements will be triggered. The following recommendations are related to general erosion potential and mitigation. Sierra Heights Elementary School Subsurface Exploration and Playfield Upgrade Preliminary Geotechnical Engineering Report Renton, Washington Preliminary Design Recommendations August 21, 2020 ASSOCIATED EARTH SCIENCES, INC. PEL/ld - 20200141E001-2 Page 11 The erosion potential of the site soils is high. Maintaining cover measures atop disturbed ground typically provides the greatest reduction to the potential generation of turbid runoff and sediment transport. During the local wet season (October 1st through March 31st), exposed soil should not remain uncovered for more than 2 days unless it is actively being worked. Ground-cover measures can include erosion control matting, plastic sheeting, straw mulch, crushed rock or recycled concrete, or mature hydroseed. Project planning and construction should follow local standards of practice with respect to TESC. Best management practices (BMPs) should include but not be limited to: • Provide storm drain inlet protection; • Route surface water away from work areas; • Keep staging areas and travel areas clean and free of track-out; • Cover work areas and stockpiled soils when not in use; • Complete earthwork during dry weather and site conditions, if possible. 10.0 SITE PREPARATION 10.1 Fields Site preparation for the renovated field should include removal of existing utilities and any structures that will not remain, stripping sod and topsoil, and regrading to establish design subgrade elevation in preparation for the installation of the new underdrains and surfacing. We understand that the new playfield will be graded to similar elevation as the existing surface. Following demolition, stripping, any overexcavation and replacement, and recompaction, all athletic field subgrades should be proof-rolled using a loaded dump truck or other suitable equipment under the observation of the geotechnical engineer. If soft or yielding areas are observed during proof-rolling, additional preparation might be required. Depending upon field conditions at the time of construction, additional preparation could include overexcavation and replacement of yielding soils with structural fill, use of a geotextile fabric, soil cement admixture stabilization, or combinations of these methods. The amount of overexcavation will depend to some degree on the time of year construction occurs, the amount of precipitation during this time, and the amount of care the contractor takes in protecting the exposed subgrade. We recommend that project documents, budgeting, and scheduling include provisions for assessing existing subgrade conditions after proof-rolling, and completion of remedial preparation as appropriate for field conditions at the time of construction. Sierra Heights Elementary School Subsurface Exploration and Playfield Upgrade Preliminary Geotechnical Engineering Report Renton, Washington Preliminary Design Recommendations August 21, 2020 ASSOCIATED EARTH SCIENCES, INC. PEL/ld - 20200141E001-2 Page 12 The on-site soils contain a significant amount of fine-grained material, which makes them moderately moisture-sensitive and subject to disturbance when wet. The contractor must use care during site preparation and excavation operations so that the underlying soils are not softened. If disturbance occurs, the softened soils should be removed and the area brought to grade with structural fill. It should be noted that the moisture content of the site soils was visually estimated to typically be above the optimum moisture content for compaction purposes at the time of our study. 10.2 Permanent and Temporary Cut and Fill Slopes We do not anticipate that significant new permanent cut and fill slopes will be necessary for this project; however, the following recommendations may be applied to slopes shorter than 8 feet in height. Permanent cut and structural fill slopes should be graded no steeper than 2H:1V (Horizontal:Vertical). Slopes should be hydroseeded as soon as possible after grading. Cut slopes in natural soils that are steeper than 2H:1V may be protected by a rockery up to 4 feet tall or an engineered retaining wall. Rockeries should not be used to face fills unless the fills are reinforced. Unsupported temporary cut slopes into unsaturated existing fill should be made no steeper than 1.5H:1V. Unsupported temporary cuts in unsaturated lodgement till may be planned at 1H:1V or flatter. Actual cut slope angles may have to be adjusted depending upon actual field conditions at the time of construction. 11.0 STRUCTURAL FILL All references to structural fill in this report refer to subgrade preparation, fill type, placement, and compaction of materials, as discussed in this section. Our recommendations for the placement of structural fill are presented in the following sections. 11.1 Fill Placement After stripping, excavation, and any required overexcavation have been performed to the satisfaction of the geotechnical engineer/engineering geologist, the upper 12 inches of exposed ground should be recompacted to 90 percent of the modified Proctor maximum density using ASTM D-1557 as the standard. If the subgrade contains too much moisture, adequate recompaction may be difficult or impossible to obtain and should probably not be attempted. In lieu of recompaction, the area to receive fill should be blanketed with washed rock or quarry spalls to act as a capillary break between the new fill and the wet subgrade. Where the exposed ground remains soft and further overexcavation is impractical, placement of an engineering Sierra Heights Elementary School Subsurface Exploration and Playfield Upgrade Preliminary Geotechnical Engineering Report Renton, Washington Preliminary Design Recommendations August 21, 2020 ASSOCIATED EARTH SCIENCES, INC. PEL/ld - 20200141E001-2 Page 13 stabilization fabric may be necessary to prevent contamination of the free-draining layer by silt migration from below. After recompaction of the exposed ground is tested and approved, or a free-draining rock course is laid, structural fill may be placed to attain desired grades. 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 90 percent of the modified Proctor maximum density using ASTM D-1557 as the standard. In the case of utility trench filling, the backfill may also need to be placed and compacted in accordance with current local codes and standards. The top of the compacted fill should extend horizontally outward a minimum distance of 3 feet beyond the locations of athletic field and pavement edges before sloping down at a maximum angle of 2H:1V. The contractor should note that any proposed fill soils must be evaluated by AESI prior to their use in fills. This would require that we have a sample of the material 72 hours 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 should be limited to favorable dry weather conditions. The on-site soils contain significant amounts of silt and are considered highly moisture-sensitive. Existing fill was observed to contain low amounts of organic material but it should be noted that excessive organic content is not suitable in structural fill applications. We anticipate that most of the existing soils will be above optimum moisture content for compaction purposes and will need to be dried to be available for reuse in structural fill applications. The reuse of on-site soils in structural fill applications is contingent on removal of excessive organic material, moisture-conditioning to a moisture content that allows compaction to a firm and unyielding condition at the specified level, and is only permitted if specifically allowed by project plans and specifications. Construction equipment traversing the site when the soils are wet can cause considerable disturbance. If fill is placed during wet weather or if proper compaction cannot be obtained, 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 with at least 25 percent retained on the No. 4 sieve. 11.2 Subsurface Drains (Underdrains) We recommend that a subsurface drainage system be provided below the new field due to the low permeability of the underlying existing fill and lodgement till sediments. We defer to the Sierra Heights Elementary School Subsurface Exploration and Playfield Upgrade Preliminary Geotechnical Engineering Report Renton, Washington Preliminary Design Recommendations August 21, 2020 ASSOCIATED EARTH SCIENCES, INC. PEL/ld - 20200141E001-2 Page 14 field designer for specific underdrain requirements and are available to provide geotechnical recommendations related to underdrain design on request. 11.3 Subsurface Drain Trenching Construction of the subsurface drains will require trenching into the underlying sediments and existing fill. As part of this study, borings were advanced to provide preliminary information on sediment density and ease of trenching. The existing fill soils are typically loose to medium dense. Lodgement till sediments will also be encountered and are typically dense to very dense and may contain gravel, cobbles, and occasional boulders. Therefore, the contractor should be prepared to excavate dense soils and to encounter gravel, cobbles, and occasional boulders during trenching. 11.4 Subfield Drainage Aggregate We anticipate that two layers of drainage aggregate will be placed and compacted over the prepared field subgrade and below the turf. The drainage aggregate is a very specialized manufactured product that provides a compactable, stable working surface while maintaining a high minimum infiltration rate. The drainage aggregate should be tested for gradation and approved by the field designer prior to delivery onsite. Daily sampling and gradation testing during placement is recommended to verify continued compliance with project specifications and approved submittals. The material should be kept moist during transport, placement, and compaction to reduce the potential for fines segregation. Once placed and compacted, the material should be field-tested for density and permeability. If field permeability test results are below the minimum project requirements, the material may need to be loosened and recompacted or removed and replaced with materials that meet the minimum permeability requirements. 12.0 PROJECT DESIGN AND CONSTRUCTION MONITORING We are available to provide additional geotechnical consultation as the project design develops and possibly changes from that upon which this report is based. We recommend that AESI perform a geotechnical review of the plans prior to final design completion. In this way, our earthwork and foundation recommendations may be properly interpreted and implemented in the design. We are also available to provide geotechnical engineering and monitoring services during construction. The integrity of the athletic fields and light poles 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. Sierra Heights Elementary School Subsurface Exploration and Playfield Upgrade Preliminary Geotechnical Engineering Report Renton, Washington Preliminary Design Recommendations August 21, 2020 ASSOCIATED EARTH SCIENCES, INC. PEL/ld - 20200141E001-2 Page 15 Construction monitoring services are not part of this current scope of work. If these services are desired, please let us know, and we will prepare a cost proposal. We have enjoyed working with you on this study and are confident that 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 ________________________________ Peter E. Linton, G.I.T. Staff Geologist ________________________________ Bruce W. Guenzler, L.E.G. Kurt D. Merriman, P.E. Associate Geologist Senior Principal Engineer Attachments: Figure 1: Vicinity Map Figure 2: Existing Site and Exploration Plan Appendix: Exploration Logs (including 2019 wetland mitigation study) Laboratory Results DATA 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 VICINITY MAP SIERRA HEIGHTS ES PLAYFIELD UPGRADE RENTON, WASHINGTON 2020141E001 7/20 1 KING COUNTY NEWCASTLE RENTON ± 0 2000 Feet PROJ NO. NOTE: BLACK AND WHITE REPRODUCTION OF THIS COLORORIGINAL MAY REDUCE ITSEFFECTIVENESS AND LEAD TOINCORRECT INTERPRETATION DATE:FIGURE:\\kirkfile2\gis\GIS_Projects\aaY2020\200141 Sierra Heights\aprx\20200141E001 F1 VM_Sierra.aprx | 20200141E001 F1 VM_Sierra | 7/9/2020 8:21 PM¥ ¥ ¥405 ¬« ¬«900 !( King County SITE King County !( ± BLACK AND WHITE REPRODUCTION OF THIS COLOR ORIGINAL MAY REDUCE ITSEFFECTIVENESS AND LEAD TO INCORRECT INTERPRETATION \\kirkfile2\gis\GIS_Projects\aaY2020\200141 Sierra Heights\aprx\20200141E001 F2 ES_Sierra.aprx | 20200141E001 F2 ES_Sierra | 7/13/2020 2:19 PMPROJ NO.DATE:FIGURE: 0 120 FEET 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 20200141E001 7/20 2 EXISTING SITE AND EXPLORATION PLAN SIERRA HEIGHTS ES PLAYFIELD UPGRADE RENTON, WASHINGTON EB-1, 6 EB-2, 19 EB-3, 3.5 EB-4, 5King CountyRentonUnion Ave NEA ccessRdNE24thCt420410 43 0 40 0 380 370 440 390 450 450 450 390 450 390 HA-1HA-2 HA-3 HA-4 EagleView Technologies, Inc. SITE EXPLORATION BORING, FILL DEPTH (FT) - 2020 HAND BORING - 2019 PARCEL CONTOUR 10 FT CONTOUR 2 FT APPENDIX Exploration Logs (including 2019 wetland mitigation study) Laboratory Results 476 222 333250/5" 50/6" 50/5" S-1 S-2 S-3 S-4 S-5 Bottom of exploration boring at 17 feetNo groundwater encountered. Topsoil - 6 inchesMoist, dark brown, silty, fine SAND, trace gravel (SM). Fill Moist, gray, silty, fine SAND, trace gravel, some organics (roots);nonstratified (SM). Moist, gray becoming brown at tip, silty, fine SAND, trace gravel (SM). Vashon Lodgement Till Hard drilling at 6 feet. Gravelly drill action at 7.5 feet. Becomes gray; poor recovery due to gravel in tip (SM). Grinding on rock at ~11 feet. No recovery, gravel in tip; blowcounts are overstated. Moist, gray, silty, fine SAND, trace gravel; unsorted (SM). 1 of 1 NAVD 88 PL2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name JHSWater Level ()Approved by: 30 Blows/Foot Samples Ground Surface Elevation (ft) Grab SampleSymbol 6 40 Datum Hammer Weight/Drop Sampler Type (ST): 446 5 10 15 20 EB-1 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"Exploration Boring Water Level at time of drilling (ATD) Sierra Heights Elementary School Upgrade M - Moisture Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet Depth (ft)S T Exploration Number20200141E001 7/9/20,7/9/20 Logged by: Shelby Tube Sample 140# / 30Boretec 1, Inc. / EC 95 Track Drill WellAESIBOR 200141E001.GPJ August 20, 20201313 44 5050/5" 5050/6" 5050/5" 655 6118 4618 50/4" 202015 50/5" S-1 S-2 S-3 S-4 S-5 S-6 Bottom of exploration boring at 20.5 feetPerched seepage zone at 19 feet. Topsoil - 8 inches Moist, dark brown, silty, fine SAND, trace gravel (SM). Fill Moist, brown with some mottled grayish brown oxidation near tip, silty, fineSAND, some gravel (SM). Moist, grayish brown, silty, fine SAND, some fractured gravel, someorganics (roots), trace gravel (SM). Gravelly drilling at ~8 feet (grinding on rock). Upper 12 inches: moist, brownish gray, fine silty, SAND, trace gravel (SM).Lower 6 inches: becomes gray. Gravelly drilling at 12 feet. Poor recovery; broken gravel in tip; blowcounts may be overstated. Moist to very moist, gray, silty, fine SAND, trace to some gravel (SM). Vashon Lodgement TillGravelly drilling.Broken gravel in tip; blowcounts are overstated. Becomes wet, gray, silty,fine SAND, trace gravel; over recovery from wet sluff(?) (SM). 1 of 1 NAVD 88 PL2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name JHSWater Level ()Approved by: 30 Blows/Foot Samples Ground Surface Elevation (ft) Grab SampleSymbol 6 40 Datum Hammer Weight/Drop Sampler Type (ST): 448 5 10 15 20 EB-2 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"Exploration Boring Water Level at time of drilling (ATD) Sierra Heights Elementary School Upgrade M - Moisture Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet Depth (ft)S T Exploration Number20200141E001 7/9/20,7/9/20 Logged by: Shelby Tube Sample 140# / 30Boretec 1, Inc. / EC 95 Track Drill WellAESIBOR 200141E001.GPJ August 20, 20201010 1919 2424 5050/4" 3535 5050/5" 111615 132732 273750/6" S-1 S-2 S-3 Bottom of exploration boring at 11.5 feetNo groundwater encountered. Topsoil - ~1 inchMoist, dark brown, silty, fine SAND, trace gravel (SM). Fill Moist, gray, very silty, fine SAND, trace gravel (SM). Vashon Lodgement Till Gravelly drilling at 4 feet. Moist, gray, silty, fine SAND, trace gravel; broken gravel in tip; nonstratified(SM). Gravelly drilling, grinding. Moist, gray, silty, fine SAND, trace gravel; unsorted (SM). 1 of 1 NAVD 88 PL2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name JHSWater Level ()Approved by: 30 Blows/Foot Samples Ground Surface Elevation (ft) Grab SampleSymbol 6 40 Datum Hammer Weight/Drop Sampler Type (ST): 446 5 10 15 20 EB-3 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"Exploration Boring Water Level at time of drilling (ATD) Sierra Heights Elementary School Upgrade M - Moisture Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet Depth (ft)S T Exploration Number20200141E001 7/9/20,7/9/20 Logged by: Shelby Tube Sample 140# / 30Boretec 1, Inc. / EC 95 Track Drill WellAESIBOR 200141E001.GPJ August 20, 20203131 59 5050/6" 101615 323350/4" 3550/6" 50/5" S-1 S-2 S-3 S-4 Bottom of exploration boring at 15.5 feetNo groundwater encountered. Topsoil - 6 inchesMoist, dark brown, silty, fine SAND, trace gravel (SM). Fill Moist, brownish gray with bands of oxidation near tip and layer (6 inchesthick) of oxidized tan near top, silty, fine SAND, trace to some gravel;nonstratified (SM). Hard drilling at 5 feet. Vashon Lodgement TillNo recovery, gravel in tip. Grab sample becomes gray with no oxidation. Gravelly drilling at 7.5 feet. Moist, gray, silty, fine SAND, trace gravel; unsorted (SM). Grinding drill action. Moist, gray, silty, fine SAND, trace gravel; poor recovery, broken gravelnear tip; unsorted (SM). 1 of 1 NAVD 88 PL2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name JHSWater Level ()Approved by: 30 Blows/Foot Samples Ground Surface Elevation (ft) Grab SampleSymbol 6 40 Datum Hammer Weight/Drop Sampler Type (ST): 444 5 10 15 20 EB-4 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"Exploration Boring Water Level at time of drilling (ATD) Sierra Heights Elementary School Upgrade M - Moisture Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet Depth (ft)S T Exploration Number20200141E001 7/9/20,7/9/20 Logged by: Shelby Tube Sample 140# / 30Boretec 1, Inc. / EC 95 Track Drill WellAESIBOR 200141E001.GPJ August 20, 20203131 5050/4" 5050/6" 5050/5" S-1 S-2 S-3 Topsoil - 3 inches Dark brown, organic rich (roots) (SM). Fill Loose, moist, brown, silty, fine to medium SAND, some gravel; feworganics (root structures) (SM). Becomes very moist. Medium dense, moist to very moist, reddish brown to gray, silty, fine tomedium SAND, some gravel; occasional organics; occasional gray clastsobserved (SM). Vashon Lodgment Till Dense, moist, light brown to gray, very silty, fine to medium SAND, somegravel; predominantly fine sand (SM). Bottom of exploration boring at 2.66 feetNo groundwater encountered. 1 of 1 N/A Sheet Depth (ft)Exploration Number180619E001 M - Moisture Water LevelProject Name HA-1 SymbolAG2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)JHSCompletionSamples Ground Surface Elevation (ft) Grab Sample 1/31/19,1/31/19 Logged by: Shelby Tube Sample N/A Ring Sample No Recovery Water Level at time of drilling (ATD) Sierra Heights ES Wetland Mitigation Study 430 Project Number 20 Renton, WA Date Start/Finish Hammer Weight/Drop Sampler Type (ST): Exploration Log 4 inches 40 Datum S T Graphic10 Other TestsHole Diameter (in) DESCRIPTION Location Water Level ()Approved by: 30 Blows/Foot Driller/Equipment Blows/6"Hand Auger Well5 AESIBOR 180619.GPJ February 14, 2019 S-1 S-2 S-3 Topsoil - 4 inches Dark brown, abundant organics (roots) (SM). Fill Loose, moist, dark brown, very silty, fine to coarse SAND, some gravel,trace cobbles; few organics (roots) (SM). Medium dense, moist, reddish brown, very silty, fine to coarse SAND,some gravel (SM). Vashon Lodgment Till Medium dense to dense, very moist to wet, light brown to gray withoxidation, gravelly, silty, fine SAND, trace cobbles; unsorted (SM). Bottom of exploration boring at 4.2 feetNo groundwater encountered. 1 of 1 N/A Sheet Depth (ft)Exploration Number180619E001 M - Moisture Water LevelProject Name HA-2 SymbolAG2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)JHSCompletionSamples Ground Surface Elevation (ft) Grab Sample 1/31/19,1/31/19 Logged by: Shelby Tube Sample N/A Ring Sample No Recovery Water Level at time of drilling (ATD) Sierra Heights ES Wetland Mitigation Study 430 Project Number 20 Renton, WA Date Start/Finish Hammer Weight/Drop Sampler Type (ST): Exploration Log 4 inches 40 Datum S T Graphic10 Other TestsHole Diameter (in) DESCRIPTION Location Water Level ()Approved by: 30 Blows/Foot Driller/Equipment Blows/6"Hand Auger Well5 AESIBOR 180619.GPJ February 14, 2019 S-1 S-2 S-3 S-4 Playfield Sand Loose, moist, brown, fine SAND, trace silt; occasional organics (roots); wellsorted (SP). Fill Loose, moist, dark brown to brown, sandy, SILT to silty, fine SAND, somegravel; occasional organics (roots) (ML/SM). Medium dense, reddish brown to light brown, silty, gravelly, fine to mediumSAND (SM). Vashon Lodgment Till ? - Dense, gray with surface oxidation, silty, fineSAND; cemented clasts (SM).Bottom of exploration boring at 1.7 feetNo groundwater encountered. 1 of 1 N/A Sheet Depth (ft)Exploration Number180619E001 M - Moisture Water LevelProject Name HA-3 SymbolAG2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)JHSCompletionSamples Ground Surface Elevation (ft) Grab Sample 1/31/19,1/31/19 Logged by: Shelby Tube Sample N/A Ring Sample No Recovery Water Level at time of drilling (ATD) Sierra Heights ES Wetland Mitigation Study 430 Project Number 20 Renton, WA Date Start/Finish Hammer Weight/Drop Sampler Type (ST): Exploration Log 4 inches 40 Datum S T Graphic10 Other TestsHole Diameter (in) DESCRIPTION Location Water Level ()Approved by: 30 Blows/Foot Driller/Equipment Blows/6"Hand Auger Well5 AESIBOR 180619.GPJ February 14, 2019 S-1 S-2 S-3 S-4 Topsoil - 6 inches Dark brown, moist, abundant organics (roots) (SM). Fill Loose, moist, reddish brown to light brown, silty, fine to coarse SAND,some gravel; few organics (stick fragments, roots) (SM). Loose to medium dense, light brown to gray, fine to coarse SAND, somesilt, some gravel; occasional organics (stick fragments) (SM). Medium dense, moist, gray to greenish gray, very silty, gravelly, fine tomedium SAND, trace cobbles; occasional organics (stick fragments) (SM). Bottom of exploration boring at 3.5 feetNo groundwater encountered. 1 of 1 N/A Sheet Depth (ft)Exploration Number180619E001 M - Moisture Water LevelProject Name HA-4 SymbolAG2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)JHSCompletionSamples Ground Surface Elevation (ft) Grab Sample 1/31/19,1/31/19 Logged by: Shelby Tube Sample N/A Ring Sample No Recovery Water Level at time of drilling (ATD) Sierra Heights ES Wetland Mitigation Study 430 Project Number 20 Renton, WA Date Start/Finish Hammer Weight/Drop Sampler Type (ST): Exploration Log 4 inches 40 Datum S T Graphic10 Other TestsHole Diameter (in) DESCRIPTION Location Water Level ()Approved by: 30 Blows/Foot Driller/Equipment Blows/6"Hand Auger Well5 AESIBOR 180619.GPJ February 14, 2019 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 2.5 7.2 4.0 11.6 37.0 37.76 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 fill Sample Number: EB3 Depth: 2.5' Client: Project: Project No:Figure silty sand 1" 3/4" 3/8" #4 #8 #10 #20 #40 #60 #100 #200 #270 100.0 97.5 93.8 90.3 87.0 86.3 82.3 74.7 61.9 47.4 37.7 35.8 NP NV SM A-4(0) 4.4550 1.4478 0.2346 0.1664 07/17/2020 07/23/2020 NAS BG 07/09/2020 DA Hogan Sierra Heights Elementary Playfield Upgrade 20200141 E001 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 4.1 10.3 5.7 14.6 30.4 34.96 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 - native Sample Number: EB3 Depth: 10' Client: Project: Project No:Figure silty sand 1-1/2" 1" 3/8" #4 #8 #10 #20 #40 #60 #100 #200 #270 100.0 97.8 90.8 85.6 81.1 79.9 74.5 65.3 54.0 44.7 34.9 31.8 NP NV SM A-2-4(0) 8.6173 4.3518 0.3293 0.2037 07/17/2020 07/23/2020 NAS BG 07/09/2020 DA Hogan Sierra Heights Elementary Playfield Upgrade 20200141 E001 PL=LL=PI= USCS (D 2487)=AASHTO (M 145)= D90=D85=D60= D50=D30=D15= D10=Cu=Cc= Remarks *(no specification provided)