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HomeMy WebLinkAboutP_Drainage_Report_250108_v1Civil Engineers & Land Use Planning Technical Information Report For Patty Thumann and Jamie Williams ADU Original Date Prepared:December 19, 2024 Site Address: 13411 SE 151st St, Renton WA 98058 Parcel Number: 2223059112 Prepared By: Lindsey Ballas Reviewed By Donna L. Breske, P.E. Donna Breske & Associates 6621 Foster Slough Rd Snohomish, WA 98290 Phone: 206-715-9582 Email: donnab@donnabreske.com 12- 1 9 - 2 4 Table of Contents Narrative: Vicinity Map……………………………………………………..1 Project Narrative…………………………………………………2 Impervious Area Exhibit…………………………………………3 Determination of Review Type………………………………….4 TIR Worksheet…………………………………………………..12 Core and Special Requirements…………………………………18 Appendix: A: Geotech Report B: Septic Design C: WWHM Water Quality Flow Rate and Contech Stormfilter Specifications D: Maintenance Thumann-Wiliams ADU December 19, 2024 Project Overview The address for this site is 13411 SE 151st St, Renton WA 98058 and the parcel number is: 2223059112.The site lot is approximately 37,774+-/ sf (0.86 Acre) and is zoned as R-4. The existing condition of the site is developed with a single family home, driveway, patios, decks etc…The site borders the edge of Cedar River and thus, a 200’ Shoreline Regulatory zone extends onto the site. Additionally, Channel Migrations are shown as well as the 100 year FEMA flood plain. There are existing trees on site of which the majority will remain except for two. Topography slopes from north to south. This permit application is for the development of a Detached Accessory Dwelling Unit and associated driveway. All existing impervious surface on site is proposed to remain. The new proposed driveway will take access from SE 151st St on the western portion of the site frontage. There is a proposed septic system that will serve the existing house and the proposed ADU. The proposed ADU and Driveway are outside of the 100 year FEMA Floodplain. However, the proposed development is partially within the 200’ Shoreline Regulatory zone and the Channel Migration zones. Impact is minimized to the greatest extent feasible while still allowing development of an ADU (accessory dwelling unit). Frontage improvements are not proposed as a “Fee In Lieu” will be paid by the property owners. A Geotechnical study was prepared by Pacific Geo Engineering. The development of the site appears feasible in regards to erosion and seismic hazards per the professional opinion of the geotech engineer. Soils on site are consistent with the soil profile for Medium Sands. Test holes on site were dug to a depth of 8 ft. below the surface grade. No groundwater or restrictive layer was observed. The long-term infiltration rate on site is 3.6 inches per hour. As such, infiltration for stormwater management on site is feasible. This project must meet the requirements of Simplified and Targeted Drainage Review per the 2022 City of Renton Stormwater Management Manual. As such, all core and special requirements are required to be evaluated. The first feasible BMP to mitigate runoff from the proposed impervious areas if Full Infiltration via an infiltration drywell. This drywell will catch flows from the proposed rooftop as well as the proposed driveway. Per the requirement for Full Infiltration, pollution generating impervious surfaces may be part of the contributing surface runoff to the infiltration facility as long as said runoff is treated for water quality. There are no other feasible BMPs to mitigate runoff from the proposed driveway due to site constraints(buffers, geometry etc…). Thus, although water quality treatment is not required per the core requirements criteria, it is required since we are routing pollution generating runoff to an infiltration facility. As such, a contech stormfilter catch basin is proposed to be placed in the proposed driveway to collect runoff, treat it, and then release it into the proposed drywell for Full Infiltration. SECTION 1.1 DRAINAGE REVIEW 6/22/2022 2022 City of Renton Surface Water Design Manual 1-14 FIGURE 1.1.2.A FLOW CHART FOR DETERMINING TYPE OF DRAINAGE REVIEW REQUIRED 1.1.2 DRAINAGE REVIEW TYPES AND REQUIREMENTS 2022 City of Renton Surface Water Design Manual 6/22/2022 1-15 TABLE 1.1.2.A REQUIREMENTS APPLIED UNDER EACH DRAINAGE REVIEW TYPE Simplified Single family residential projects that result in 2,000 sf of new plus replaced impervious surface or 7,000 sf of land disturbing activity but do not exceed the new plus replaced PGIS, new PGPS, and new pervious surface thresholds specified in Sec. 1.1.2.1. Note: The project may also be subject to Targeted Drainage Review. Directed Single family residential projects that result in 2,000 sf of new plus replaced impervious surface or 7,000 sf of land disturbing activity that are not subject to Simplified Drainage Review or Large Project Drainage Review. The project may also be subject to Targeted Drainage Review. Targeted New and redevelopment projects that are not subject to Directed, Full or Large Project Drainage Review, AND have characteristics of one or more of the following categories of projects: 1.Projects containing or adjacent to a flood, erosion, or steep slope hazard area; or projects within a Landslide Hazard Drainage Area or Aquifer Protection Area. 2.Projects that construct or modify a drainage pipe/ditch that is 12″ or larger or receive runoff from a 12″ or larger drainage pipe/ditch. 3.Redevelopment projects with $100,000 in improvements to a high-use site.(1) Full All projects that result in 2,000 sf of new plus replaced impervious surface or 7,000 sf of land disturbing activity but are not subject to Simplified Drainage Review, Directed Drainage Review, OR Large Project Drainage Review. Large Project Projects that result in 50 acres of new impervious surface within a subbasin or multiple subbasins that are hydraulically connected. DRAINAGE REVIEW TYPE Simplified Directed Targeted Full Large Project Categ 1 Categ 2 Categ 3 SIMPLIFIED DRAINAGE REQUIREMENTS SEE NOTE 4 CORE REQUIREMENT #1 Discharge at Natural Location (4)(2,3)*(2)   CORE REQUIREMENT #2 Offsite Analysis (4)(2,3)*(2) (3)(3)(3) CORE REQUIREMENT #3 Flow Control Facilities (4)(2,3)*(2)(3)(3) CORE REQUIREMENT #4 Conveyance System (4)(2,3)*(2)   CORE REQUIREMENT #5 Construction Stormwater Pollution Prevention (4)(2,3)     CORE REQUIREMENT #6 Maintenance & Operations (4)(2,3)*(2) CORE REQUIREMENT #7 Financial Guarantees & Liability (4)(2,3)*(2) (3) (3)(3)(3) CORE REQUIREMENT #8 Water Quality Facilities (4)(2,3)*(2)(3)(3) CORE REQUIREMENT #9 On-site BMPs (4)  SECTION 1.1 DRAINAGE REVIEW 6/22/2022 2022 City of Renton Surface Water Design Manual 1-16 TABLE 1.1.2.A REQUIREMENTS APPLIED UNDER EACH DRAINAGE REVIEW TYPE DRAINAGE REVIEW TYPE Simplified Directed Targeted Full Large Project Categ 1 Categ 2 Categ 3 SPECIAL REQUIREMENT #1 Other Adopted Area-Specific Requirements (4)(2,3)(3)(3)(3) SPECIAL REQUIREMENT #2 Flood Hazard Area Delineation (4)(2,3)(3)(3)(3) SPECIAL REQUIREMENT #3 Flood Protection Facilities (4)(2,3)(3)(3)(3) SPECIAL REQUIREMENT #4 Source Control (4)(2,3)(3)(3)(3)(3)(3) SPECIAL REQUIREMENT #5 Oil Control (4)(2,3)(3)(3)(3) SPECIAL REQUIREMENT #6 Aquifer Protection Areas (2,3)(3)(3)(3)(3)(3) (1) Category 3 projects installing oil controls that construct or modify a 12-inch pipe/ditch are also Category 2 projects. (2) May be applied by CED based on project or site-specific conditions. Documentation of compliance required. (3) These requirements have exemptions or thresholds that may preclude or limit their application to a specific project. (4) A proposed project subject to Simplified Drainage Review that complies with the Simplified drainage requirements detailed in Appendix C is presumed to comply with all the core and special requirements in Sections 1.2 and 1.3 except those requirements that would apply to the project if it is subject to Targeted Drainage Review as specified in Section 1.1.2.2. 1.1.2.1 SIMPLIFIED DRAINAGE REVIEW Simplified Drainage Review is for small residential building projects or clearing projects that meet the threshold requirements below. The core and special requirements applied under Full Drainage Review are replaced with simplified drainage requirements that can be applied by a non-engineer. These requirements include simple stormwater dispersion, infiltration, and site design techniques called flow control Best Management Practices (BMPs), which provide the necessary mitigation of flow and water quality impacts for small projects. Also included are simple measures for erosion and sediment control (ESC). This simplified form of drainage review acknowledges that drainage impacts for many small project proposals can be effectively mitigated without construction of costly flow control and water quality facilities. The Simplified Drainage Review process minimizes the time and effort required to design, submit, review, and approve drainage facilities for these proposals. In most cases, the requirements can be met with submittals prepared by contractors, architects, or homeowners without the involvement of a civil engineer. Note: some projects subject to Simplified Drainage Review may also require Targeted Drainage Review if they meet any of the threshold criteria in Section 1.1.2.2. Threshold Simplified Drainage Review is required for any single family residential project that will result in 2,000 square feet8 or more of new impervious surface, replaced impervious surface, or new plus replaced 8 The thresholds of 2,000 and 7,000 square feet shall be applied by project site. All other thresholds specified in terms of square feet of impervious or pervious surface shall be applied by threshold discharge area and in accordance with the definitions of these surfaces in Section 1.1. Note: the calculation of total impervious surface may exclude any such added impervious surface that is confirmed by CED staff to be already mitigated by a City approved and inspected flow control facility or on-site BMP. 1.1.2 DRAINAGE REVIEW TYPES AND REQUIREMENTS 2022 City of Renton Surface Water Design Manual 6/22/2022 1-17 impervious surface, or 7,000 square feet8 or more of land disturbing activity, AND that meets the following criteria: The project will result in less than 5,000 square feet of new plus replaced pollution generating impervious surface, will result in less than ¾ acre of new pollution generating pervious surfaces, AND meets one of the following three additional criteria: 1. The project meets the Basic Exemption from flow control in Core Requirement #3 : a) the project results in less than 5,000 square feet of new plus replaced impervious surface, AND b) less than ¾ acres of new pervious surface will be added. Note the Basic Exemption thresholds are applied by project site. 2. For projects on predominately till soils: The project results in no more than 7,947 square feet of target impervious surfaces as defined below AND proposed pervious area is equal to or less than 14,941 – 1.88 x (total target impervious surfaces). 3. For projects on predominately outwash soils: The project results in no more than 6,872 square feet of target impervious surfaces as defined below AND proposed pervious area is equal to or less than 20,343 – 2.96 x (total target impervious surfaces). Determination of Target Impervious Surface  If the project is a New Development project, then target impervious surfaces include new plus proposed replaced impervious surface.  If the project is a Redevelopment project where o New impervious surface is less than 5,000 square feet or o Valuation of improvements is less than 50% of the assessed value of the existing site improvements, then target impervious surfaces include new impervious surface.  If the project is a Redevelopment project where o New impervious surface is greater than or equal to 5,000 square feet and o Valuation of improvements is greater than or equal to 50% of the assessed value of the existing site improvements, then target impervious surfaces include new plus proposed replaced impervious surface. Note: for the purposes applying this threshold to a proposed single family residential subdivision (i.e., plat or short plat project), the impervious surface coverage assumed on each created lot shall be 4,000 square feet or the maximum allowed per RMC 4-2-110A, whichever is less. A lower impervious surface coverage may be assumed for any lot in which the lower impervious surface coverage is set as the maximum through a declaration of covenant recorded for the lot. Also, the new pervious surface assumed on each created lot shall be the entire lot area, except the assumed impervious portion and any portion in which native conditions are preserved by a clearing limit per RMC IV, a covenant or easement recorded for the lot, or a tract dedicated by the proposed subdivision. Scope of Requirements IF Simplified Drainage Review is required, THEN the proposed project must comply with the simplified project submittal and drainage design requirements detailed in Simplified Drainage Requirements adopted as Appendix C to this manual. These requirements include simplified BMPs/measures for flow control and erosion and sediment control. Presumption of Compliance with Core and Special Requirements The simplified drainage requirements applied under Simplified Drainage Review are considered sufficient to meet the overall intent of the core and special requirements in Sections 1.2 and 1.3, except under certain SECTION 1.1 DRAINAGE REVIEW 6/22/2022 2022 City of Renton Surface Water Design Manual 1-18 conditions when a proposed project has characteristics that trigger Targeted Drainage Review (see the threshold for Targeted Drainage Review in Section 1.1.2.2) and may require the involvement of a civil engineer. Therefore, any proposed project that is subject to Simplified Drainage Review as determined above and complies with the Simplified drainage requirements detailed in Appendix C is presumed to comply with all the core and special requirements in Sections 1.2 and 1.3 except those requirements that would apply to the project if it is subject to Targeted Drainage Review as specified in Section 1.1.2.2. 1.1.2.2 TARGETED DRAINAGE REVIEW Targeted Drainage Review (TDR) is an abbreviated evaluation by CED permit review staff of a proposed project’s compliance with selected core and special requirements. Projects subject to this type of drainage review are typically Simplified Drainage Review proposals or other small projects that have site-specific or project-specific drainage concerns that must be addressed by a civil engineer or CED engineering review staff. Under Targeted Drainage Review, engineering costs associated with drainage design and review are kept to a minimum because the review includes only those requirements that would apply to the particular project. Threshold Targeted Drainage Review is required for any proposed project that is subject to drainage review as determined in Section 1.1.1, but is not subject to Directed, Full or Large Project Drainage Review as determined in Sections 1.1.2.3, 1.1.2.4 and 1.1.2.5, AND that has the characteristics of one or more of the following project categories:  TDR Project Category #1: Projects that contain or are adjacent to a flood hazard, erosion hazard area, or steep slope hazard area as defined in RMC 4-3-050; OR projects located within a Landslide Hazard Drainage Area or Aquifer Protection Area. Note: at the discretion of CED, this category may also include any project in Simplified Drainage Review that has a design or site-specific issue that must be addressed by a civil engineer. A project is considered adjacent to a flood, erosion, or steep slope hazard area if any portion of the project site is within 50 feet.  TDR Project Category #2: Projects that propose to construct or modify a drainage pipe/ditch that is 12 inches or more in size/depth or receives surface and storm water runoff from a drainage pipe/ditch that is 12 inches or more in size/depth.  TDR Project Category #3: Redevelopment projects that propose $100,000 or more of improvements to an existing high-use site. Scope of Requirements IF Targeted Drainage Review is required, THEN the applicant must demonstrate that the proposed project complies with the selected core and special requirements corresponding to the project category or categories that best match the proposed project. The project categories and applicable requirements for each are described below and summarized in Table 1.1.2.A. Note: If the proposed project has the characteristics of more than one project category, the requirements of each applicable category shall apply. Compliance with these requirements requires the submittal of engineering plans and calculations stamped by a civil engineer, unless deemed unnecessary by CED and the City of Renton. The engineer need only demonstrate compliance with those core and special requirements that have been predetermined to be applicable based on specific project characteristics as detailed below. The procedures and requirements for submitting engineering plans and calculations can be found in Section 2.3. TDR Project Category #1 This category includes projects that are too small to trigger application of most core requirements, but may be subject to site-specific floodplain or drainage requirements related to certain critical areas, or other area-specific drainage requirements adopted by the City. Such projects primarily include single family residential projects in Simplified Drainage Review. 1.1.2 DRAINAGE REVIEW TYPES AND REQUIREMENTS 2022 City of Renton Surface Water Design Manual 6/22/2022 1-19 IF the proposed project meets the characteristics of TDR Project Category #1, THEN the applicant must demonstrate that the project complies with the following requirements:  “Core Requirement #5: Construction Stormwater Pollution Prevention,” Section 1.2.5  “Special Requirement #1: Other Adopted Area-Specific Requirements,” Section 1.3.1  “Special Requirement #2: Floodplain/Floodway Analysis,” Section 1.3.2  “Special Requirement #3: Flood Protection Facilities,” Section 1.3.3  “Special Requirement #4: Source Control,” Section 1.3.4  “Special Requirement #6: Aquifer Protection Area,” Section 1.3.6. In addition, CED may require the applicant to demonstrate compliance with any one or more of the remaining seven core requirements in Section 1.2 based on project or site-specific conditions. For example, if the proposed project discharges to an erosion or steep slope hazard area as defined in RMC 4-3-050, CED may require compliance with “Core Requirement #1: Discharge at the Natural Location” (Section 1.2.1). This may in turn require compliance with “Core Requirement #2: Offsite Analysis” (Section 1.2.2) if a tightline is required by Core Requirement #1. If a tightline is found to be infeasible, CED may instead require a flow control facility per “Core Requirement #3: Flow Control” (Section 1.2.3). If a tightline is feasible, “Core Requirement #4: Conveyance System” (Section 1.2.4) would be required to ensure proper size and design. Any required flow control facility or tightline system may also trigger compliance with “Core Requirement #6: Maintenance and Operations” (Section 1.2.6), “Core Requirement #7: Financial Guarantees and Liability” (Section 1.2.7), and possibly “Core Requirement #8, Water Quality” (Section 1.2.8) if runoff from pollution-generating impervious surfaces is collected. The applicant may also need to address compliance with any applicable critical areas requirements in RMC 4-3-050 as determined by CED. TDR Project Category #2 This category is intended to apply selected core and special requirements to those projects that propose to construct or modify a drainage system of specified size, but are not adding sufficient impervious surface to trigger Full Drainage Review or Large Project Drainage Review. IF the proposed project meets the characteristics of TDR Project Category #2, THEN the applicant must demonstrate that the proposed project complies with the following requirements:  “Core Requirement #1: Discharge at the Natural Location,” Section 1.2.1  “Core Requirement #2: Offsite Analysis,” Section 1.2.2  “Core Requirement #4: Conveyance System,” Section 1.2.4  “Core Requirement #5: Construction Stormwater Pollution Prevention,” Section 1.2.5  “Core Requirement #6: Maintenance and Operations,” Section 1.2.6  “Core Requirement #7: Financial Guarantees and Liability,” Section 1.2.7  “Special Requirement #4: Source Control,” Section 1.3.4. TDR Project Category #3 This category is intended to improve water quality by applying source control and oil control requirements to redevelopment projects located on the most intensively used sites developed prior to current water quality requirements. These are referred to as high-use sites. IF the proposed project meets the characteristics of TDR Project Category #3, THEN the applicant must demonstrate that the proposed project complies with the following requirements:  “Core Requirement #5: Construction Stormwater Pollution Prevention,” Section 1.2.5  “Core Requirement #6: Maintenance and Operations,” Section 1.2.6  “Core Requirement #7: Financial Guarantees and Liability,” Section 1.2.7  “Special Requirement #4: Source Control,” Section 1.3.4 SECTION 1.1 DRAINAGE REVIEW 6/22/2022 2022 City of Renton Surface Water Design Manual 1-20  “Special Requirement #5: Oil Control,” Section 1.3.5. Note: In some cases, CED may determine that application of these requirements does not require submittal of engineering plans and calculations stamped by a civil engineer. 1.1.2.3 DIRECTED DRAINAGE REVIEW Directed Drainage Review (DDR) is an evaluation of a proposed single family residential project by CED permit review staff to determine a specialized list of submittal (plans, technical reports, etc.) and engineering requirements that ensures compliance with all core and special requirements in this chapter. Projects subject to this type of drainage review are single family residential projects that do not qualify for Simplified Drainage Review. CED staff will review proposals and determine the following: whether the project is exempt from a given core or special requirement based on exemptions and exceptions listed in this Manual; whether a pre- engineered solution is available and feasible for meeting a given core or special requirement; whether a licensed civil engineer is required to comply with a given core or special requirement; and the type of technical report and plan submittal required to document compliance with the core and special requirements. Depending upon a project’s site specific conditions, DDR may result in requirements for engineering or documentation that range from following the requirements of Appendix C to those required for full drainage review. CED will provide and/or require documentation of the DDR process and decision making to be included in the project file that demonstrates how compliance with all core and special requirements in this Manual are achieved. Under Directed Drainage Review, engineering costs associated with drainage design and review are minimized because the review is tailored to the particular project. Threshold Directed Drainage Review is required for any single family residential project that results in 2,000 square feet or more of new plus replaced impervious surface or 7,000 square feet or more of land disturbing activity (refer to Section 1.1.1) but is not subject to Simplified Drainage Review or Large Project Drainage Review as determined in Sections 1.1.2.1 and Section 1.1.2.5. Scope of Requirements IF Directed Review is required, THEN the proposed project must comply with the following requirements:  All nine core requirements in Section 1.2  All six special requirements in Section 1.3 CED may require submission of engineering plans and calculations stamped by a civil engineer to demonstrate compliance with these requirements. The procedures and requirements for submittal of engineering plans and calculations are as directed by CED in the DDR process. 1.1.2.4 FULL DRAINAGE REVIEW Full Drainage Review is the evaluation by City staff (CED unless otherwise specified in RMC 4-6-060) of a proposed project’s compliance with the full range of core and special requirements in this chapter. This review addresses the impacts associated with changing land cover on typical sites. Threshold Full Drainage Review is required for any proposed project, including a redevelopment project, that is subject to drainage review as determined in Section 1.1.1, OR that meets one or more of the following criteria: CITY OF RENTON SURFACE WATER DESIGN MANUAL 2022 City of Renton Surface Water Design Manual 6/22/2022 8-A-1 REFERENCE 8-A 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 __________________________ CED Permit # ________________________ Location Township ________________ Range __________________ Section _________________ Site Address __________________________ _____________________________________ Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS Land Use (e.g., Subdivision / Short Subd.) Building (e.g., M/F / Commercial / SFR) 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 __________________ __________________ __________________ Patty Thuman & Jamie Williams 206-819-6588 13411 SE 151st St, Renton WA 98058 Donna L. Breske, P.E. Donna Breske & Associates 206-715-9582 Thuman-Williams ADU SW - 22 23 5 13411 SE 151st St, Renton WA 98058 x x x x x x x REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 6/22/2022 2022 City of Renton Surface Water Design Manual 8-A-2 Part 6 SWDM ADJUSTMENT APPROVALS Type (circle one): Standard / Blanket Description: (include conditions in TIR Section 2) ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ Approved Adjustment No. ______________________ Date of Approval: _______________________ Part 7 MONITORING REQUIREMENTS Monitoring Required: Yes / No Start Date: _______________________ Completion Date: _______________________ Describe: _________________________________ _________________________________________ _________________________________________ Re: SWDM 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 ______________________ _____________________________________ Cedar River NA NA Core Requirements 1-9 and Special Req. 1-5 x x x REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2022 City of Renton Surface Water Design Manual 6/22/2022 Ref 8-A-3 Part 10 SOILS Soil Type ______________________ ______________________ ______________________ ______________________ Slopes ________________________ ________________________ ________________________ ________________________ Erosion Potential _________________________ _________________________ _________________________ _________________________ High Groundwater Table (within 5 feet) Other ________________________________ Sole Source Aquifer Seeps/Springs Additional Sheets Attached 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 9 apply): Discharge at Natural Location Number of Natural Discharge Locations: Offsite Analysis Level: 1 / 2 / 3 dated:__________________ Flow Control (include facility summary sheet) Standard: _______________________________ or Exemption Number: ____________ 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 Medium Sands Moderate NA-as long as stormwater sheet flow does not ocurr x x x 100 yr FEMA Floodplain, 200' shoreline reg. no dispersion allowed, minimal space available for BMPs outside sensitive areas & buffers Flow Control Exempt, Water Quality Exempt none-full infiltration NA 1 none proposed REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 6/22/2022 2022 City of Renton Surface Water Design Manual 8-A-4 Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Water Quality (include facility summary sheet) Type (circle one): Basic / Sens. Lake / Enhanced Basic / Bog or Exemption No. _______________________ On-site BMPs Describe: Special Requirements (as applicable): Area Specific Drainage Requirements Type: SDO / MDP / BP / 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: 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: 1a Full Infiltration Drywell 100 year FEMA NA NA REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2022 City of Renton Surface Water Design Manual 6/22/2022 Ref 8-A-5 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 Control Pollutants Protect Existing and Proposed BMPs/Facilities Maintain Protective 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 BMPs/Facilities, restore operation of BMPs/Facilities as necessary Flag limits of sensitive areas and open space preservation areas Other _______________________ Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and Sketch) Flow Control Description Water Quality Description On-site BMPs Description Detention Infiltration Regional Facility Shared Facility Other _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ Vegetated Flowpath Wetpool Filtration Oil Control Spill Control Other _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ Full Dispersion Full Infiltration Limited Infiltration Rain Gardens Bioretention Permeable Pavement Basic Dispersion Soil Amendment Perforated Pipe Connection Other _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ x x x x x x x x x x x Contech Strmfilter x Infiltration Drywell REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 6/22/2022 2022 City of Renton Surface Water Design Manual 8-A-6 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 Core Requirement #1: Discharge to the Natural Location Stormwater runoff is proposed to be collected and infiltrated into a drywell. Infiltrated runoff will recharge subsurface flows ultimately recharging the Cedar River at the base of the site. Core Requirement #2: Offsite Analysis This project proposes to convey runoff from the proposed impervious areas into a full infiltration drywell. The runoff from this proposed development is not anticipated to have any negative impact on downstream properties as it is not anticipated to leave the site since the soils have a fast infiltration rate of 3.6 inches per hour. Thus, any sort of failure or overflow is highly unlikely. However, infiltrated flows may contribute to recharging the subsurface hydrology on the site. The topography of the site has the low point of the site on the southern portion bordering Cedar River. Any runoff that would leave the site would enter Cedar River and continue to flow within said river within the ¼ mile downstream flow threshold for Downstream Analysis. See Below: Core Requirement #3: Flow Control This project meets the requirements for the basic exemption 1 per Section 1.2.3 of the 2022 Renton Stormwater Design Manual because the project proposes less than 5,000 square feet of new impervious surface. Core Requirement #4: Conveyance System This project proposes a 6” pvc conveyance system from the proposed house and driveway to the proposed drywell. Core Requirement #5: Construction Stormwater Pollution Prevention A construction stormwater pollution prevention plan has been included in this report, with applicable elements shown on this projects TESC plan. Core Requirement #6: Maintenance and Operations A maintenance section has been included in the last Appendix of this report. Core Requirement #7: Financial Guarantees and Liability This project will pay a fee in lieu of installing frontage improvements. Core Requirement #8: Water Quality This project does not require water quality treatment per the criteria of Core requirement #8. However, this project is proposing a water quality treatment element since runoff from the proposed pollution generating impervious surface is proposed to be infiltrated. Thus, a contech stormfilter catch basin is proposed to remove pollutants before routing runoff into the proposed infiltration drywell. Core Requirement #9: Flow Control BMP’s Full Infiltration is proposed as Full Dispersion (the first BMP in the hierarchal order of Large Lot BMPs is infeasible due to the Geotechnical Engineer’s recommendation that sheet flow runoff (dispersion)not be employed to avoid erosion concerns) The total proposed impervious area is 3,359 sf {1,288 sf of proposed ADU rooftop+ 1,595 sf on site proposed driveway + 476 sf ROW driveway approach} A drywell is proposed to infiltrate all runoff from proposed impervious areas. The geotech engineer found that no groundwater or restrictive layer was present at all in depth of 8 feet below the surface. The soil type is medium sands. The drywell sizing criteria states that 90 cubic feet of drain rock (drywell area) shall be present for every 1,000 sf of contributing surface runoff. Thus, 3,359/1000=3.35 3.35x90=302.2 cubic feet required. The drywell dimensions have been sized per the following formula: V=h •𝜋𝜋•r² Thus, the drywell is proposed to have the following cylindrical dimensions: Height:6 ft. Diameter:8.25’ (Radius: 4.125’) The design requires a minimum 1 ft. of soil cover and then 1 ft. minimum separation to groundwater or restrictive layer. Since the actual groundwater table/restrictive layer was not encountered in 8 feet and we don’t know where it occurs thereafter, we have assumed that the minimum 1 ft. separation should be from 8 feet below the surface. As such, the ground elevation in the proposed location of the drywell is 78. The top of the drywell infiltration rock shall occur at 77 ft. and the bottom of the facility shall occur at 71 with one foot of separation to elevation 70 (8 feet below the surface grade). OK. Special Requirement #I: Other Adopted Area-Specific Requirements NA-This requirement does not apply to this project. Special Requirement #2: Flood Hazard Area Delineation The 100 year FEMA Flood Plain is shown on the provided Civil Plans. Special Requirement #3: Flood Protection Facilities NA- This project does not propose development within the floodplain. Special Requirement #4: Source Control NA- This project does not propose commercial building, or a commercial site development permit. Special Requirement #5: Oil Control NA- This project does not meet the threshold criteria for this requirement. Construction Stormwater Pollution Prevention 1.Clearing Limits: Prior to any site clearing or grading, areas to remain undisturbed during project construction shall be delineated on the project's TESC plan and physically marked on the project site. Clearing limits are to be marked by brightly colored tape or orange fencing and are shown on the plans. 2. Cover Measures: Temporary and permanent cover measures shall be provided when necessary to protect disturbed areas. The intent of these measures is to prevent erosion by having as much area as possible covered during any period of precipitation. Disturbed areas not covered in impervious surface shall be landscaped or re-seeded with grass. 3.Perimeter Protection: Perimeter protection to filter sediment from sheet flow shall be provided downstream of all disturbed areas prior to upslope grading. Straw Wattles and Silt Fence are proposed. 4.Traffic Area Stabilization: Unsurfaced entrances, roads, and parking areas used by construction traffic shall be stabilized to minimize erosion and tracking of sediment offsite. Temporary Construction Access proposed. 5.Sediment Retention: Areas at the perimeter of the site shall be treated solely with perimeter protection. Sediment retention facilities shall be installed prior to grading any contributing area. Straw Wattles and Silt Fence. 6.Surface Water Collection: Areas at the perimeter of the site, shall be treated solely with perimeter protection and do not require surface water collection. Measures shall be installed concurrently with or immediately following rough grading and shall be designed, constructed, and stabilized as needed to minimize erosion. Straw Wattles and Silt Fence. 7.Dewatering Control: The water resulting from construction site de-watering activities must be treated prior to discharge or disposed of as specified. NA- Dewatering is not anticipated to take place during this project. 8. Dust Control: Preventative measures to minimize wind transport of soil shall be implemented when a traffic hazard may be created or when sediment transported by wind is likely to be deposited in water resources. NA 9. Flow Control: Surface water from disturbed areas must be routed through the project's onsite flow control facility or other provisions must be made to prevent increases in the existing site conditions 2-year and 10-year runoff peaks discharging from the project site during construction NA. Flow Control Exempt project. 10. Control Pollutants: Stormwater pollution prevention (SWPPS) measures are required to prevent, reduce, or eliminate the discharge of pollutants to onsite or adjacent stormwater systems or watercourses from construction-related activities such as materials delivery and storage, onsite equipment fueling and maintenance, demolition of existing buildings and disposition of demolition materials and other waste, and concrete handling, washout and disposal. NA 11. Protect Existing and Proposed Flow Control BMPs: Sedimentation and soil compaction reduce the infiltration capacity of native and engineered soils. Protection measures shall be applied/installed and maintained so as to prevent adverse impacts to existing flow control BMPs and areas of proposed flow control BMPs for the project. Adverse impacts can prompt the requirement to restore or replace affected BMPs. NA 12. Maintain BMPs: Protection measures shall be maintained to assure continued performance of their intended function, to prevent adverse impacts to existing flow control BMPs and areas of proposed flow control BMPs, and protect other disturbed areas of the project. All BMP’s are to be maintained, and soils stabilized upon removal of BMP’s. 13. Manage the Project: Coordination and timing of site development activities relative to TESC concerns, and timely inspection, maintenance and update of protective measures are necessary to effectively manage the project and assure the success of protective TESC and SWPPS design and implementation. Appendix A: Geotech Report GEOTECHNICAL ENGINEERING STUDY For WILLIAMS PROPERTY - NEW ADDITION 13411, SE 151ST STREET RENTON, WA 98058 Prepared For JAMES WILLIAMS & PATTY THUMANN 13411, SE 151ST STREET RENTON, WA 98058 Prepared By P.O. BOX 1419, ISSAQUAH, WASHINGTON 98027 PGE PROJECT NUMBER 24-754 June 28, 2024 June 28, 2024 Client: Jamie Williams & Patty Thumann 13411, SE 151st St. Renton, WA 98058 Re: Williams Property Geotechnical Engineering Study 13411, SE 151st St. Renton, WA 98058 PGE Project No. 24-754 Mrs. Patty: As per the request, Pacific Geo Engineering, LLC (PGE) has completed the geotechnical engineering study for the subject property in Renton, Washington, which is shown on Vicinity Map, Figure 1. The study includes soil investigation and development of geotechnical engineering recommendations pertinent to the geotechnical aspect of the proposed new building addition. This geotechnical engineering study report summarizes the results of our evaluations and the recommendations. This study is completed in accordance with the mutually agreed upon scope of services described in our proposal no. 24-04-818, dated April 24th, 2024, which was authorized on May 16, 2024. The scope of services was developed based on the preliminary understanding of the proposed new addition obtained from Mrs. Patty Thumann. Our scope of services is planned to obtain as much subsurface information as possible within the time and budgetary constraints of the project. The primary purposes of our limited geotechnical study were to perform site reconnaissance, explore and characterize subsurface soil and groundwater conditions in the site, perform laboratory testing of native soil, and review of available local geologic maps and geotechnical literatures, and to use the data and the information obtained from the above as a basis for formation of our geotechnical recommendations for the proposed new addition. Our recommendations are provided for the design and construction of the proposed new building addition, allowable bearing capacity value, slab-on-grade floor, site preparation, grading and earthwork operations, overexcavations, and fill placement and compaction. Also, recommendations are developed for site drainage and erosion control measures. We have also evaluated the site’s susceptibility to liquefaction under seismic conditions and the infiltration feasibility of the native soil for considering a below grade infiltration system in the site. The feasibility study was performed following the guidelines provided in the 2021 King County King County Surface Water Design Manual (KCSWDM). ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 2 of 41 1.0 Scope of Services Based on the scope of this geotechnical study delineated in the contract agreement, the following items are accomplished - field exploration, laboratory soil testing, engineering evaluation of the field and laboratory data, grading recommendations, infiltration feasibility, and foundation recommendations. The scope of our work did not include any wetland study, or any environmental analysis or evaluation to find the presence of any hazardous or toxic materials in the soil, surface water, groundwater, or air in or around this site. 1.1 Engineering Evaluation The results from the field and laboratory tests were evaluated and engineering analyses were performed to develop the design information and the engineering recommendations for the geotechnical aspect of the proposed development, which are provided in this report. Subsurface Conditions  Descriptions of the soil and the groundwater conditions;  Soil Test Pit Log;  Depth to water table and any sign of high water table, if encountered;  Laboratory soil index property test results.  Native soil Classification as per USCS system; General Site Development & Earthwork & Grading  Grading and earthwork including site preparation, and fill placement and compaction;  Use of on-site soils as structural fills;  Imported structural fill requirements;  Underground utility structure trench backfilling and pipe bedding;  Temporary and permanent excavation slopes;  Site drainage including permanent subsurface drainage systems and temporary groundwater control measures, if necessary:  Dry and wet weather construction:  Erosion control measurements. ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 3 of 41 Structure  Foundation type recommendation - conventional shallow spread footings;  Allowable bearing capacity value for supporting the proposed footings and the residence;  Estimated total and differential settlements of the footings;  Frictional and passive values for the resistance of lateral forces;  Subgrade preparation for spread footings;  Slab-on-grade for the proposed building, and the subgrade preparation for slab-on-grade;  Modulus of subgrade reaction for the design of the slab-on-grade floor;  Seismic design recommendations, including the site co-efficient as per ASCE7-16 Standard & 2018 IBC. Geologic Hazard Mitigations  Geologic hazards evaluation: erosion, seismic, and landslide;  Liquefaction potential evaluation of native soil;  Erosion control measures. 2.0 Proposed Development The existing residence and the proposed new building addition to be built in the backyard are shown on Aerial Site View, Figure 2. The new addition is marked as ‘B’ in the figure. Based on our on-site conversation with the owner the proposed addition will have a two-story building with a garage floor level and a floor above the garage. There are now two large trees located at the proposed addition area, which will be cut to build the new addition. The part of the southern portion of subject property is located within FEMA designated 100 year floodplain adjacent to the northern bank of the Cedar River. The northerly extent of FEMA 100 year floodplain line as per the King County iMap is shown on Site & Exploration Plan, Figure 3. The proposed new addition will be built beyond the northerly floodplain line near the existing residence. Based on our current understanding of the grading plan, we assume that the new building addition will be built almost at the current grades of the property without any significant grade changes within the proposed new development area. We assume that there will be some amount of cut depths will be required to remove the topsoils, heavy root zone, and the tree root bulbs, to achieve the final native subgrades described later on in this report as ‘competent’ native subgrades, and to achieve the footing embedment depth of minimum 18 inches below the current grades. Some fills may need to be placed to backfill the void areas to be created due to the overexcavation of the topsoils, heavy root zone, and the root bulbs. Based on the ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 4 of 41 findings from our site exploration, approximately, 6 inches of overexcavation depth may be required below the current grades to remove the topsoils. The overexcavation depths to be required to remove the heavy root zone and the tree root bulbs should be decided on-site during the grading operation in the site. The void areas to be created due to the overexcavation will be backfilled either with the native granular soils or new imported structural fills. The final footing subgrades , and the new fills if needed, must bear directly over the final ‘competent’ native subgrades. The slab-on-grade floor will be placed on new fill pad to be placed to backfill the void areas. The new fills must also bear over the final ‘competent’ native subgrades. Based on our experience with similar type of residence, we anticipate that wall loads will be in the range of 2 to 3 kips per lineal foot, isolated column loads in the range of 40 to 60 kips, and slab -on-grade floor loads of 150 pounds per square foot (psf). The conclusions and recommendations contained in this report are based upon our current understanding of the proposed development. We recommend that PGE should be allowed to review the final design grades and the actual features of the proposed development, and the final construction plan to verify that the geotechnical recommendations provided in this report are incorporated into the final construction documents. PGE’s review of the final plan would also allow re-evaluating the recommendations, and if necessary, to modify the recommendations before the construction begins. We believe this would be helpful for the project’s speedy completion and success. 3.0 Surface and Subsurface Features 3.1 Site Location The subject property is located at 13411, SE 151st Street, Renton, as shown in Figure 1. The site has a single parcel number assigned as 222305-9112. The property is almost a rectangular shape land, which is bounded by single family residences on the east and west, by SE 151st St on the north, and by Cedar River on the south. The site has an access via a concrete driveway from the SE 151st Street. 3.2 Site Descriptions The subject property is located within a region dominated by densely populated single family residences. An existing single-story, single family residence is located at the front area of the property close to the SE 151st Street. The property has vegetations comprised of mostly landscape grasses, and scattered small to large trees. The existing site features with contours and the northerly extent of FEMA 100 year floodplain line as per King County iMap are shown on Figure 2 and 3. The property is almost a level ground with minor downgrade slope towards the Cedar River. Based on Figure 3, approximate site elevation is 78 feet near the SE 151st Street which, gradually slopes down to ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 5 of 41 76 feet and then to 74 feet near the northern bank of the Cedar River. The part of the southern portion of subject property is located within a FEMA designated 100 year floodplain as shown in Figure 3. The floodplain area within the property is covered with landscape grasses. The existing residence is located near the SE 151st Street, which is beyond the FEMA 100 year floodplain line. The proposed new addition will also be built beyond the line. 4.0 Field Investigation Soil investigation was performed at one location in the proposed new building area at the backyard of the property as shown on Figure 3. The test pit location was selected by PGE’s engineer. The test pit location plotted on Figure 3 should be considered accurate only to the degree implied by the measuring methods. The test pit was advanced at the site on May 21, 2024, using an excavating machine hired by PGE. The test pit was excavated up to approximately 8 feet depth below the grades. The specific number and location of the test pit was selected in relation to the existing and proposed site features, accessibility, underground utility conflicts, purpose of evaluation, budget considerations, and after the consultation and approval of the owner. An experienced geotechnical engineer from PGE logged the subsurface conditions in the test borings and visually-manually classified the soil samples in the field according to the methods presented in ASTM D-2488-93 (based on the soil samples' density/consistency, moisture condition, grain size, and plasticity estimations) and the 'Key to Exploration Logs' figure in Appendix A, and observed pertinent site features. The final exploration log was prepared with our observation and interpretation of the test boring drilling, and visual examination of the samples in the field. The soils were classified according to the methods presented on the Figure 'Key to Exploration Logs' in Appendix A. This figure also provides a legend explaining the symbols and abbreviations used in the soil exploration logs. The soil logs indicate the depth where the soils change. It should be noted that the indicated stratification lines on the logs represent the approximate boundaries between soil types. The actual transitions of varying soil strata may be more gradual in the field. 5.0 Laboratory Testing Laboratory tests were conducted on several selected representative soil samples to evaluate the general physical properties and the engineering characteristics of the soils encountered. The bulk samples were visually-manually classified in the laboratory following the procedure described in ASTM D-2488-17 (based on the soil samples' density/consistency, moisture condition, grain size, and plasticity estimations), ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 6 of 41 and later on the soil samples' classifications were supplemented by laboratory tests data in ac cordance with the procedure described in ASTM D-2487-17. Moisture content tests were conducted on the samples in accordance with ASTM D-2216-10 procedures. One (1) Sieve Analysis test (Grain size distributions) was performed on one selected sample in accordance with ASTM D-6913 procedure. The results of the moisture content tests and the amount of percentages of minus #200 sieve passed are provided in the test pit logs, Appendix A. The grain-size distributions of the soil obtained from the Sieve Analysis tests are shown in the laboratory test report B-1 in Appendix B. 6.0 Site Soil and Groundwater Conditions Topsoils The explored area was covered with landscape grass, which is underlain by top soils for approximately 6 inches thickness below the current grades. Native Soils Native soils were observed below the topsoils, which were granular in nature consisted of sand with gravel, cobble, and boulder, designated as SP as per USCS soil classification. Hydrogeologic Condition During the month of May, when our soil investigation was done, no groundwater or perched water seepage was observed within the exploration depth. No sign of mottling (oxidized soils) was either noticed in the soil. Typically, mottling signs are indicative of accumulation of seasonal perched groundwater above the underlying denser deposit. Perched water is defined when stormwater permeates through the upper, less denser soils, and accumulates on top of the underlying denser, less permeable soils, like glacial till, which is very typical in the Puget Sound area. Typically, perched water presents in a spatial manner above the glacial till. It is to be noted that fluctuations in the perched water amount and level, and groundwater level may be expected due to the seasonal variations in the amount of rainfall, surface runoff, and other factors not apparent at the time of our explorations. Typically, the perched water and groundwater level rise higher and the flow rate increases during the wet winter months. The possibility of the fluctuations and the presence of perched water and the ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 7 of 41 ground water should be considered when considering any underground infiltration system in this site for managing the stormwater runoff of the proposed development. The preceding discussion on the subsurface conditions of the site is intended as a general review to highlight the major subsurface stratification features and material characteristics. For more complete and specific information at individual test pit location, please review the Soil Test Pit Log (Figure A-1) in Appendix A. The log includes soil descriptions, stratification, and location of the samples, and the laboratory test results. It should be noted that the stratification lines shown on the logs represent the approximate boundaries between various soil strata; actual transitions may be more gradual or more severe. The subsurface explorations made as part of the site evaluation indicate the subsurface conditions at test pit location only and as such the actual subsurface conditions may vary in other areas of the site. The actual nature and extent of such variation would not become evident until additional explorations are performed in the site or until construction activities have begun. 7.0 Regional Geology The site is in the Puget Sound Lowland, a north-south trending structural and topographic depression lying between Olympic Mountains on the west and Cascade Mountains on the east. The lowland depression experienced successive glaciation and nonglaciation activities over the time of Pleistocene period. During the most recent Fraser glaciation, which advanced from and retreated to British Columbia between 13,000 and 20,000 years ago, the lowland depression was buried under about 3,000 feet of continental glacial ice. During the successive glacial and nonglacial intervals, the lowland depression, which is underlain by Tertiary volcanic and sedimentary bedrock, was filled up above the bedrocks to the present-day land surface with Quaternary sediments, which consisted of Pleistocene glacial and nonglacial sediments. The glacial deposits include concrete-like lodgement till, lacustrine silt, fine sand and clay, advance and recessional outwash composed of sand or sand and gravel, and some glaciomarine materials. The nonglacial deposits include largely fluvial sand and gravel, overback silt and clay deposits, and peat attesting to the sluggish stream environments that were apparently widespread during nonglacial times. 7.1 NRCS Map - USDA Soil Unit As per The site is underlain by Pilchuck Loamy Fine Sand (Pc), which is made up of gravelly and sandy alluvium soils with excessively drained characteristic. This soil unit is described as Hydrologic Soil Group ‘A’. The soil observed in the test pit is consistent with this mapped soil unit. ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 8 of 41 8.0 Geologic Hazards As per the City of Renton Municipal Code, the potential geologic hazards i.e., the landslide, seismic, flood, and erosion in the subject property are evaluated, which are discussed in the following subsections. 8.1 Landslide Hazard Based on the topography of the site, the site is almost a level flat ground hence the potential of landslide hazard in this site is considered nil. 8.2 Seismic Hazard Liquefaction Potential Earthquake-induced geologic hazards may include liquefaction, lateral spreading, slope instability, and ground surface fault rupture. Liquefaction is a phenomenon, which takes place due to the reduction or complete loss of soil strength due to an increase in pore water pressure in soils during the seismic vibrations induced by a major earthquake event. Liquefaction primarily affects geologically recent deposits of loose, fine-grained sands and granular silts that are below the groundwater table. Based on our review of the soil and groundwater conditions in the test pit, it is our opinion that the on-site soils are not prone to liquefaction because of the absence of any groundwater table in the test pit and the presence of denser native granular soil containing gravel, cobble, and boulder at shallower depth in the explored area of the site. Therefore, potential for widespread liquefaction and its associated hazards over the site during a seismic event is none. Therefore, subsurface conditions do not warrant additional mitigation techniques relating to liquefaction hazards. While the site is relatively near the Seattle Fault zone, no evidence of ground fault rupture was observed in the subsurface explorations or our site reconnaissance. Therefore, the potential for ground surface is also low. Regional Seismicity The site is located in the Puget Sound region of western Washington, which is seismically active. Seismicity in this region is attributed primarily to the interaction between the Pacific, Juan de Fuca and North American plates. The Juan de Fuca plate is subducting beneath the North American plate at the Cascadia Subduction Zone (CSZ). This produces both intercrustal (between plates) and intracrustal (within a plate) earthquakes. In the following sections we discuss the design criteria and potential hazards associated with the regional seismicity. Provided the design criteria listed below are followed, the proposed structure should have no greater seismic risk damage than other appropriately designed structures in the Puget Sound area. ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 9 of 41 Seismic Design Parameters As per the WA State Interactive Geologic Information Portal, Seismic Map, the NEHRP Seismic Site Class is mapped as Site Class ‘C’, which is described as very dense deposit. According to the SEA OSHPD Seismic Design Maps, and as per the 2016 ASCE 7-16 code standards, Table 20.3-1, for the seismic Site Class ‘C’, the following seismic design parameters should be used for the structural design of the building. Table 1 - Seismic Design Parameters Spectral Response Acceleration (SRA) and Site Coefficients Short Period (0.2 sec) Maximum Considered Earthquake (MCE) Ss = 1.387g Site Response Coefficient (Site Class D) Fa = 1.2 Adjusted Spectral Response Acceleration (SRA) of MCE SMS = Ss x Fa = 1.664g Design SRA SDS = 2/3 x SMS = 1.109g Spectral Response Acceleration (SRA) and Site Coefficients One Second Period (1 sec) Maximum Considered Earthquake (MCE) S1 = 0.473g Site Response Coefficient (Site Class D) Fv = 1.5 Adjusted Spectral Response Acceleration (SRA) of MCE SM1 = S1 x FV = 0.71g Design SRA SD1 = 2/3 x SM1 = 0.473g Peak Ground Acceleration The mapped peak ground acceleration (PGA) for this site is 0.59g. To account for site class, the PGA is multiplied by a site amplification factor (FPGA) of 1.2. The resulting site modified peak ground acceleration (PGAM) is 0.708g. 8.3 Flood Hazard The part of the southern portion of subject property is located within FEMA designated 100 year floodplain adjacent to the northern bank of the Cedar River, which is shown on Flood Hazard Map, Figure 4. The northerly extent of FEMA 100 year floodplain line as per the King County iMap is shown on Figure 3, which shows that the proposed new addition will be built beyond the northerly floodplain line near the existing residence, which is not a floodplain area as per Figure 4. ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 10 of 41 8.4 Erosion Hazard Typically, uncontrolled surface water with runoff over unprotected site surfaces during construction activities is considered the single most important factor that impacts the erosion potential of a site. The erosion process may be accelerated significantly when factors such as soils with high fines, sloped surface, and wet weather combines together. Taking into consideration the factors such as the presence of near-surface native soil with fines less than 5 percent, level grades of the subject property, and assuming that the proposed construction will take place during dry summer period it is our opinion that the potential for erosion hazard of the site soils is not a limiting factor for the proposed development. This possibility will be further reduced if appropriate erosion control measures are installed and maintained as recommended below. These measurements must be kept in place and to be maintained throughout the earthwork and the grading activities. Though special mitigations are not necessary, a temporary erosion and sediment control (TESC) plan should be created and implemented during site construction. It is our opinion that implementation of a relatively basic erosion control plan will prevent off site sediment transport. The proper use of “best management practices” (BMPs) should be utilized during development of the building to minimize the potential for erosion and sediment off of the property due to clearing, grading and construction traffic. Implementation of a TESC plan will likely be a requirement of the clearing and grading or building permit. City of Renton will perform TESC inspections during construction to verify compliance with the TESC plan and permit conditions. Erosion Control Measures & Mitigations All erosion sediment control measures must conform to the City of Renton or King County requirements. As a minimum, we recommend implementing the following erosion and sediment control Department of Ecology (DOE) best Management Practices (BMPs) prior to, during, and immediately after clearing and grading activities at the site. Mass grading activities and the earthwork should be completed within the dry summer period since the near surface site soils containing some silts may pose some erosion related problems. Limit disturbance to areas where construction is imminent. If possible, site clearing and grading should be performed in stages, with successive stages not being cleared until erosion control measures for the previous stages are in place. Determine staging areas for temporary stockpiles of excavated soils as part of the excavation planning. ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 11 of 41 Provide temporary cover for denuded areas including cut slopes and soil stockpiles during periods of inactivity. From October 1 to April 30, no soil shall remain un-stabilized for more than 48 hours. From May 1 to September 13, no soil shall remain un-stabilized for more than seven days. Temporary cover may consist of straw mulch or plastic sheeting that is securely anchored to the ground surface. Plastic covering should be placed and anchored, as specified in BMP C123 provided in Chapter 4.1 of the Stormwater Management Manual for Western Washington. Mulching should be conform to the guide lines outlined in the BMP C121 provided in Chapter 4.1 of the Stormwater Management Manual for Western Washington Establish permanent covers for exposed areas that will not be worked for period of 30 days or more by seeding in conjunction with a mulch cover or appropriate hydroseeding. Seeding should conform to the specifications outlined in BMP C120 provided in Chapter 4.1 of the Stormwater Management Manual for Western Washington. Measurements such as the control of surface water must be maintained during construction. Vegetation clearing must be kept very limited in this site to reduce the exposed surface areas. It is recommended that following the clearing of the vegetations, grading the open exposed areas should be covered with mulch or hydroseed. No disturbance or removal of the existing vegetations, tress, and undergrowths should be made beyond the proposed construction area. Temporary erosion and sedimentary control (TESC) plan, as a part of the Best Management Practices (BMP) must be developed and implemented as well. The TESC plan should include the use of geotextile barriers (silt fences) along any down-slope, straw bales to de-energize downward flow, controlled surface grading, limited work areas, equipment washing, storm drain inlet protection, and sediment traps. The TESC plan may need to be reviewed and modified periodically to address the changing site conditions during ongoing progress of the construction and the weather. A permanent erosion control plan is to be implemented following the completion of the construction. Permanent erosion control measurements such as establishment of landscaping, replantation of trees and groundcover vegetations as soon as feasible in areas that are necessarily disturbed by earthwork activities, control of downspouts and surface drains, control of sheet flow over the excavation slope, prevention of discharging water over the excavation slope and at the toe of the slope are to be implemented following the completion of the construction. Install temporary or permanent tightline pipes, where necessary and practical, to convey stormwater from above slope to appropriate downslope facilities on flatter terrain. Install permanent stormwater runoff diversion systems, such as swales, curbs, berms, or pipes, to prevent flow directly over any final slope grades. We recommend that completed graded-areas be restricted from traffic or protected prior to wet weather conditions. The graded areas may be protected by paving, placing asphalt-treated base, a layer of free-graining material such as pit run sand and gravel or clean crushed rock material containing less than 5 percent fines, or some combination of the above. ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 12 of 41 Containment Install a silt fence along the downhill side of the construction area that will be disturbed. The silt fence should be placed before cleaning and grading is initiated and should conform to the specifications outlined in BMP C233 provided in Chapter 4.2 of the Stormwater Management Manual for Western Washington. Construct interceptor dikes and shallow drainage swales to intercept surface water flow and route the flow away from the construction tare to be stabilized and approved point of controlled discharge. Some small detention ponds with pipe slope drains may be incorporated with the swales in order to collect and transport the runoff to the discharge point. Provide on-site sediment retention for collected runoff. Runoff should not flow freely over the top of the slope or off the site. The on-site contractor should perform daily review and maintenance of all erosion and sedimentation control measures at the site to ensure their proper working order. Provided the recommended erosion and sedimentation control BMP’s are properly implemented and maintained, it is our opinion that the planned development will not increase the potential for erosion at the site or on adjacent properties. 9.0 Executive Summary Based on this study, the subject site is considered suitable for the proposed development, if the geotechnical recommendations provided in this report are properly understood and interpreted, and strictly implemented during the design and construction phases of the proposed development. It should be noted that if the subsurface conditions are found to be different in the unexplored areas of the site than what it is found in the explored areas then the recommendations provided in this report may need to be revisited and altered, to incorporate the changes if to be found on the subsurface conditions. This may calls for possible changes in the final design of the project as well. A contingency plan should be in place by the owner considering the above scenario. Based on the soil conditions encountered in the test pit, the footings of the new building addition should be installed on the ‘competent’ native subgrades to be consisted of native soil deposit. A ‘competent’ native subgrade is described when the final native subgrade is ‘redensified’, and ‘compacted and proofrolled’ adequately in a thorough manner to firm, unyielding, and stable conditions following the procedures described later on in Section 10.1.3, 'Subgrade Preparation' of this report. We recommend that the topsoils, root zone, and root bulbs from the new building footprint area must be completely removed to achieve the final ‘competent, native subgrades. During the removals, the overexcavation depths below the current grades may vary, which should be determined by PGE’s geotechnical engineer. The final ‘competent’ native subgrades must be verified ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 13 of 41 by PGE’s on-site geotechnical engineer prior to placing the forms and rebars of the footings and placing new structural fills. The footings for the new building addition can be comprised of perimeter wall strip footings with interior isolated column spread footings. The final ‘competent’ native subgrades will be able to support the footings and to provide an allowable bearing capacity value of 2000 psf for supporting the footings, and keeping the total settlement and differential settlement of the footings within the allowable limits of 1 inch or less and ½ inch or less, respectively We recommend that the slab-on-grade floor is to be bearing on the new fill pad to be placed in the void areas to be created after the removals of the topsoil, root zone, and root bulbs. The fills must be backfilled with either on-site, native granular soils, or new, imported structural fills, which must be adequately compacted prior to placing the floor slab on top of the fill pad. The new fill thickness may vary based on the final floor elevation and the thickness of the existing fills. The final fill thickness requirement should be decided by the PGE’s on- site geotechnical engineer. The new structural fills must be placed after the final native subgrades should be ‘redensified’ and ‘proofrolled’ adequately to prepare the final native subgrades as ‘competent’ native subgrades, and to be accepted by the PGE’s on-site geotechnical engineer. The other hard surfaces such as paved driveway, patios, or walkways should be placed over the final native ‘competent’ subgrades similar to the footings and the new fills. The structural fills to be used for filling up the void areas may be new, imported, structural fill materials or the native granular material. The structural fills must be consisted of clean, crushed rock or crushed gravel, and sand that is fairly well graded between coarse and fine as described later on in Section 10.1.6, ‘Structural Fills’ of this report. The native soils are consisted of granular soils having very low fines content hence considered as suitable for reuse as structural fills. However, the soils contain larger-size particles such as large gravel, cobble, and boulder, which will pose problem during the compaction of the soils. The native soils can be used as structural fills if the larger size particles, larger gravel, cobble and boulder, are removed from the native soils. The new fills must be placed and compacted as per the recommendations provided later on in Section 10.1.7, 'Fill Placement and Compaction Requirements' of this report. The new structural fills must be compacted adequately to firm and unyielding condition to achieve 95% or more of fills’ dry density value to be determined from the ASTM Test Designation D-1557 (Laboratory Modified Proctor) method. A single or double-drum heavy duty vibratory roller should be used to perform the redensification, proofrolling, final native subgrade preparation, and fill compaction. Alternatively, a walk-behind, heavy-duty, vibratory plate compactor (similar to TMG-PC330K Reversible Plate Compactor with 14HP Kohler Engine) can also be used to perform the above activities. The vibratory plate compactor produces much less vibrations ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 14 of 41 than the big drum roller. Therefore, if vibration is an issue for the neighbors and their residences’ stability then we recommend that the vibratory plate compactor will be suitable for this site. The horizontal limits of the fill placement under any load-bearing structure should extend laterally beyond the each side of the fill pad for a horizontal distance equal to the depth of the fill pad. This is to avoid the loading from the structure (which is assumed exerts pressure through an imaginary line at 1H:1V inclination or at 450 angle from below the footings) to pass through the fill thickness instead the loading line to pass below the fill thickness. The depths and the degree of the competence of the final native subgrades may vary across the site, which must be verified and approved on-site by the PGE’s on-site geotechnical engineer. The redensification of the final native subgrades, proofrolling and preparation of the final native subgrades as ‘competent’ native subgrades, and the fill placement and compaction must be monitored and approved by the on-site geotechnical engineer prior to placing the new fills, and the footings, slab-on-grade floor, concrete paved driveway, side-walk, and concrete patio directly above new fills. The heavy-root, organic reach topsoil of approximately 6 inches thickness must be removed completely from the proposed development area prior to start the cut and fill operations in this site. The topsoils cannot be used structural fills and be stockpiled for later use in the landscaping areas. In our opinion, the combination of geological factors such as the presence of native sand with gravel, cobble, and boulder with its measured infiltration rate obtained from our infiltration test , and the absence of perched water seepage within the test pit depth explored, are considered to be feasible for a below grade ‘full-infiltration’ system like a drywell in this site. A detail of the infiltration feasibility study in this site and the recommendation for final design infiltration rate are provided later on in Section 11.0 of this report. 10.0 Conclusion & Recommendations 10.1 Site Preparation Preparation of the site should involve clearing, stripping, subgrade preparation and proofrolling, cutting, filling, excavations, and drainage installations. The following paragraphs provide specific recommendations on these issues. 10.1.1 Clearing and Grubbing Initial site preparation for construction of the proposed new addition building, driveway, parking area, any other load-bearing structure, and placing new fills on the final native subgrades should include ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 15 of 41 stripping of vegetation and topsoil from the construction area. Based on the topsoil thickness encountered at our test pit location, we anticipate topsoil stripping depths of about 6 inches, however, thicker layers of topsoil may be present in unexplored portions of the site. It should be realized that if the stripping operation takes place during wet winter months, it is typical a greater stripping depth might be necessary to remove the near-surface moisture-sensitive silty soils disturbed during the stripping; therefore, stripping is best performed during dry weather period. Stripped vegetation debris should be removed from the site. Stripped organic topsoil will not be suitable for use as structural fill but may be used for future landscaping purposes. 10.1.2 Overexcavation Once the clearing of the vegetations and the topsoils from the proposed development area will be completed, the overexcavation of the heavy root zone, tree root bulbs, unsuitable native soils if there will be any underneath the proposed construction area can be initiated to establish the desired final ‘competent’ native subgrades for bearing the proposed new building addition and the new structural fills. The overexcavation depth must be a minimum of 18 inches below the current or the final site grade to achieve the footing embedment depth requirement below the above grades. The overexcavation in the proposed new construction area must be verified by PGE’s on-site geotechnical engineer. The overexcavation should be performed using smooth-edged bucket to limit the disturbances of the potential final native subgrades. 10.1.3 Subgrade Preparation Redensification After the clearing of the vegetations and topsoils, and following the completion of the overerxcavation upto the final ‘competent’ native subgrades, we recommend that all final native subgrades that are supposed to be supporting the load-bearing structure should be redensified to enhance the in-situ density of the final native subgrades, improving their bearing capacity hence reducing their potentials of undergoing excessive settlement. Typically, the redensification is effective for the upper one to two feet of soil below the final native subgrades. The depth of the in-situ density increase depends on the compaction equipment to be used. Typically, the redensification of the final native subgrades is done using a big, heavy- weight, double-drum, vibratory roller. The redensification is achieved by having the compaction equipment make several passes as to be found necessary by the on-site geotechnical engineer. One pass is considered to consist of a passage of the compactor in each direction, forwards and backwards, over the same strip of subgrade. The redensification process should be carried out over the whole of the excavated “at grade” footing subgrade and slab-on-grade areas, and any other load-bearing structures such as the new fill pad and sidewalk. ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 16 of 41 Proofroling Any exposed subgrades that are intended to provide direct support for new construction and/or require new fills should be adequately proofrolled to evaluate their conditions and to identify the presence of any isolated soft and yielding areas and to verify that stable subgrades are achieved to support the proposed structures, and any new fills. Proofrolling should be done with a loaded dump truck or a front -end loader or a big vibratory double-drum roller under the supervision of the PGE’s on-site geotechnical engineer. If it is found by the on-site geotechnical engineer that the soil is too wet near the subgrade to be proofrolled or it not feasible to proofroll the subgrade, then an alternative method (i.e., visual evaluation and probing with a 1/2- inch diameter steel T-probe) can be used by the geotechnical engineer to identify the presence of any isolated soft and yielding areas and to verify that stable subgrades are achieved to support the proposed structures and any new fills. If any subgrade area is found in soft and moist conditions, ruts and pumps excessively, and cannot be stabilized in place by compaction the affected soils should be over -excavated completely to firm and unyielding suitable bearing materials, and to be replaced with ne w structural fills to desired final native subgrade levels. If the depth of overexcavation to remove unstable soils becomes excessive, a geotextile fabric, such as Mirafi 500X or equivalent in conjunction with structural fills may be considered to achieve a firm bearing final subgrades to support the proposed structures and any new fills. Any final native subgrades and foundation bearing surfaces should not be exposed to standing water. If water is present in the final native subgrades or in the base of the footing excavation, it must be removed completely to bring the subgrades into dry condition before placing any new fills and formwork and rebars. Protection of exposed soil, such as placing a 6-inch thick layer of crushed rock or a 3- to 4-inch layer of lean- mix concrete, could be used to limit disturbance to bearing surfaces. If the base of an overerxcavated area is excessively soft and wet and needs stabilization then we recommend considering a 6 to 12-inch layer of ballast rock or quarry spalls should be placed to form a base on which the structural fill needs to be placed and compacted to achieve the final grade. Ballast rock should meet the requirements for Class B Foundation Material in Section 9-03.17 and quarry spalls should meet the requirements in Section 9-13.1(5) of the 2024 WSDOT Standard Specifications. The ballast rock or quarry spalls should be pushed into the subgrade with the back of a backhoe bucket or with the use of a large - vibratory steel drummed roller without the use of vibration. Such decision should be made the on-site geotechnical engineer during the actual construction of the project. ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 17 of 41 10.1.4 Backfilling of Test Pit and Tree Root Bulb Holes The loosely backfilled soils in the area of exploratory test pit should be overexcavated completely to the firm native soils and backfilled with adequately compacted new, imported structural fills to the final grades, following the procedures described later on in Section 10.1.7, 'Fill Placement and Compaction Requirements' of this report. The new, imported structural fills should be granular materials like sand and gravel meeting the requirements provided later on in Section 10.1.6, ‘Structural Fills’ of this report. Prior to placing the new fills the final native subgrades at the bottom of the overexcavated areas must be proofrolled adequately to firm and unyielding conditions as recommended earlier in Section 10.1.3, ‘Subgrade Preparation’ of this report and accepted by PGE’s on-site geotechnical engineer prior to placing new fills. Similar procedures described above should be followed after the holes to be created due to the removals of the tree root bulbs. 10.1.5 Reuse of Native Soils as Structural Fills The ability to use native soils as structural fills, to be obtained during the mass grading activities, will depend on the factors such as the quality of the native soils, i.e., the presence of excessive roots and organics, fines content, larger-size particles, moisture content, soil types and their gradation, and the prevailing weather conditions during the time of the construction i.e., dry or wet weather. The weather plays a significant role in determining if the native soils can be compacted adequately during the wet weather period, especially when the native soils content higher percentages of fines. Typically, native soils containing unsuitable materials such as the excessive roots and organics are not considered suitable for use as structural fills. If the native soil below the topsoils contains percentages of fines greater than the typical ‘imported structural fills’ that contains 5% or lesser fines, then the native soil is to be considered as moisture insensitive soils. The percentage of fines content in the native soil can be determined from running a sieve analysis test on the native soil sample. Typically, when the fines content (that portion passing the U.S. No. 200 sieve) of soil increases, the soil becomes increasingly sensitive to small changes in moisture content, which makes the soils’ compaction more difficult or impossible. Soils containing more than about 5 percent fines by weight cannot be consistently compacted to the recommend degree when the moisture content is more than about 2 percent above or below the optimum. Especially, if the soils with higher fines content are used during the wet weather period, typically between October and May, significant reduction in the soils strength and support capabilities occur. Also, when these soils become wet they may be slow to dry and thus significantly retard the progress of grading and compaction activities. Therefore, the native soil can be used as structural fills during the wet weather period based on the percentage of fines present in the native soil. However, irrespective of the ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 18 of 41 percentage of fines content the native soil can be used as borrow materials for general filling purposes during the dry season, provided the optimum moisture content of the soils can be maintained during the compaction. In addition to the higher percentage of fines, if the native soils are found in excessively over the optimum moisture content, then the soils would pose problems during their compaction. This may require moisture conditioning of the native soils prior to their placement and compaction. Other criteria that is to be considered critical prior to use native soils as structural fills is the presence of significant amount of larger-size particles such as larger size gravels, and cobbles and boulders. Typically, this type of soil is not considered suitable to use as structural fills, since the larger-size gravels, and cobbles and the boulders pose problems during the compaction of the fills. Therefore, the native soils if considered to be used as structural fills or borrow materials then the larger-size gravels, and cobbles and boulders must be removed from the native soils. This can be accomplished either by screening the native soils on-site using a screener machine or by selectively handpicking the larger-size particles, whichever methodology is feasible and economical. The PGE’s on-site geotechnical engineer should inspect the final product to verify that the final structural fills do not contain larger size particles. The final fills should contain a maximum of 2 to 3-inch particle diameter for being able to be adequately compacted. Based on the above criteria, the native soil is considered acceptable as ‘structural fills’ because of its low fines content, however it contains significant amount of larger size particles hence will pose problem during its compaction. As it is recommended, the native soils can be used if the larger size particles are removed. The suitability of using the native soils should be verified and approved by the on-site geotechnical engineer prior to their use. If the native soils cannot be used after the inspection and asked by PGE’s on-site geotechnical engineer to discard then imported new structural fills are to be brought in to the site for backfilling purposes. We recommend that a contingency plan should be in place in the project budget if the native soils are to be exported out, or new structural fills are to be imported into the site, or on-site screening of the native soils is to be required. 10.1.6 Structural Fill General Requirements Typically, excavated native soils containing topsoil, unsuitable materials such as excessive roots and organics, wood debris and pieces, trash, left over construction debris are not considered suitable for use as structural fills, and should be properly disposed offsite. ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 19 of 41 If the native soils are found unsuitable for using as structural fills then we recommend that imported structural fill should be used for backfilling purposes. The workability of material for use a s structural fill will depend on the gradation and moisture content of the soil. Structural fill is defined as non-organic soil, free of any debris and deleterious materials, and well-graded and free-draining granular material, such as sand and gravel or crushed rock with a maximum particle size of 3 inches for any individual particle and less that 5 percent fines by weight based on the minus ¾-inch fraction. We recommend that washed crushed rock or select granular fill, as described below, be used for structural fill during wet weather. If prolonged dry weather prevails during the earthwork phase of construction, materials with somewhat higher fines content may be acceptable. Weather and site conditions should be considered when determining the type of impo rt fill materials purchased and brought to the site for use as structural fill. Frozen material should not be used as structural fills. All materials should be approved by the project geotechnical engineer prior to use. A sample of each fill material type should be submitted to the project geotechnical engineer for evaluation and approval prior to use. A typical gradation for structural fill is presented in the following table. Table 2 - Structural Fill U.S. Standard Sieve Size Percent Passing by Dry Weight 3 inch 100 ¾ inch 50 –100 No. 4 25 – 65 No. 10 10 – 50 No. 40 0 – 20 No. 200 5 Maximum* * Based on the ¾ inch fraction. ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 20 of 41 WSDOT Structural Fills For reference purpose, the following table provides the specifications for various types of structural fills that can be considered in this site for use as new, imported structural fills. Table 3 - WSDOT 2024 Structural Fills Specifications Fill Type Recommended Materials Structural Fill 9-03.9(1) Ballast 9-03.9(3) Crushed Surfacing Base Course 9-03-12(1)A Gravel Back fill for Foundation Class A 9-03.14(1) Gravel Borrow Common Fill Section 9-03.14(3) Common Borrow Free-draining Granular Fill 9-03.9(2) Permeable Ballast 9-03.12(2) Gravel Backfill for Walls 9-03.12(4) Gravel Backfill for Drains For most applications, we recommend that structural fill consist of material similar to ‘Gravel Borrow’ or ‘Select Borrow’ as described in Section 9-03.14(1) or Section 9-03.14(2), respectively, of the WSDOT 2024 Standard Specifications. Select Granular Fill Imported materials with gradation characteristics similar to WSDOT 2024 Standard Specification 9- 03.9 (Aggregates for Ballast and Crushed Surfacing), or 9-03.14 (Gravel Borrow) is suitable for use as select granular fill, provided that the fines content is less than 5 percent (based on the minus ¾-inch fraction) and the maximum particle size is 6 inches. Other Fill Materials Other materials may also be considered suitable for use as structural fill provided they are approved by the project geotechnical engineer. Such materials typically used include clean, well -graded sand and gravel (pit-run); clean sand; various mixtures of gravel; crushed rock; controlled-density-fill (CDF, it should meet the requirements in Section 2-09.3(1)E of the WSDOT 2024 Standard Specifications); and lean-mix concrete (LMC). Recycled asphalt, concrete, and glass, which are derived from pulverizing the parent materials also potentially useful as structural fill in certain applications. These materials must be thoroughly ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 21 of 41 crushed to a size deemed appropriate by the geotechnical engineer (usually less than 2 inches). The structural fills should have a maximum 2 to 3-inch particle diameter. Pipe Bedding Trench backfill to be placed beneath, adjacent to, and for at least 2 feet above utilities line should consist of well-graded granular material with a maximum particle size of 1 inch and less than 10 percent by dry weight passing the US Standard No. 200 Sieve, and should meet the standards of ‘Gravel Backfill for Pipe Zone Bedding’ described in Section 9-03.12(3) of the 2024 WSDOT Standard Specifications. Trench backfill must be free of debris, organic material and rock fragments larger than 1 inch. Trench backfills We recommend that the trench backfills to be placed 2 feet above the pipe and upto the final pavement subgrade level should be consisted of materials similar to ‘Gravel Borrow’ described in Section 9- 03.14(1) or ‘Select Borrow’ as described in Section 9-03.14(2), of the 2024 WSDOT Standard Specifications. Trench backfill must be free of debris, organic material and rock fragments larger than 3 inch. Stabilization Material Stabilization rock should consist of pit or quarry run rock that is well -graded, angular, crushed rock consisting of 4- or 6-inch-minus material with less than 5 percent passing the US Standard No. 4 Sieve. The material should be free of organic matter and other deleterious material. WSDOT SS 9-13.(15) - Quarry Spalls can be used as a general specification for this material with the stipulation of limiting the maximum size to 6 inches. 10.1.7 Fill Placement and Compaction Requirements Generally, quarry spalls, controlled density fills (CDF), lean mix concrete (LMC) do not require special placement and compaction procedures. In contrast, clean sand, crushed rock, soil mixtures and recycled concrete should be placed under special placement and compaction procedures and specifications described here. The structural fills under structural elements should be placed in uniform loose lifts not exceeding 12 inches in thickness for a big, heavy-weight, double-drum, vibratory roller or a big, heavy-duty, hand-guided, walk-behind, vibratory plate compactor (similar to TMG-PC330K Reversible Plate Compactor with 14HP Kohler Engine). A regular, walk-behind vibratory plate compactor can be used when the loose fill thickness will be kept within 4 to 6 inches. No heavy compaction equipment such as hoe pack or big vibratory roller should be used to compact the backfills to be placed behind the footing stem walls, within the horizontal distance equal to the heights of ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 22 of 41 the walls. Use of the heavy compaction equipment will impose excess surcharge load on the walls, which may cause permanent lateral instability to the walls. We recommend that the fills behind the footing stem walls should be placed in 4 inches lifts and to be compacted with a hand held smaller and lighter compaction equipment. Each lift of fills whether 12 inches or 4 inches or 6 inches should be compacted to a minimum of 95 percent of the fill’s maximum dry density as to be determined in the laboratory by ASTM Test Designation D-1557 (Modified Proctor) method, or to the applicable minimum City or County standard, whichever is the more conservative. The fill should be moisture conditioned such that its final moisture content at the time of compaction should be at or near (typically within about 2 percent) of its optimum moisture content, as determined by the ASTM Test Designation D-1557 (Modified Proctor) method. This should help enhance the compatibility of the materials and avoid the risks involved with wet, moisture sensitive soils. Fills should not be placed on frozen subgrades. If the fill materials are on the wet side of optimum, they can be dried by relatively inexpensively periodic windrowing and aeration or by intermixing lime or cement powder to absorb excess moisture. An ordinary Portland cement powder can be used in this regard. In using concrete we have found that the hydration of the cement not only results in water absorption, but also develops some “concrete-like” strength within the soil and cement matrix. In our experience the soil cement matrix can sometimes generates a compressive strength in excess of two thousand (2,000) psi. If this option is selected, we recommend that for a preliminary estimation purpose, the cement powder may be intermixed at a rate of about 3% by weight of the soil. The actual cement content should be decided during the mass grading activity de pending on the wet weather, soils’ natural moisture content, and the soil types. This form of soil treatment is not suitable for any type soils that are considered as free-daring backfills. The compacted structural fill pad should extend outside all foundations and other load bearing structures elements for a minimum distance equal to the thickness of the fill pad. Because of the sensitivity of this project we recommend that any and all structural fills and /or load bearing backfills be tested for determining the in-place density and the water content of the fills as per the Nuclear Density Gauge method (ASTM D6938). This test results will help to verify that the backfills have the achieved the appropriate degree of compaction and the moisture content. We recommend that compaction of the fills be tested periodically throughout the fill placement. A field compaction testing program should be prepared by the contractor with the assistance from the project geotechnical engineer. If field density tests indicate that the last lift of compacted fills has not been achieved the required percent of compaction or the surface is pumping and weaving under loading, then the fill should be scarified, moisture-conditioned to near optimum moisture content, re-compacted, and re-tested prior to placing additional lifts. ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 23 of 41 We recommend that a minimum of one test be performed for one hundred (100) square feet of compacted or backfill surface area or for every one hundred (100) cubic feet of fill or backfill, whichever generates the greater number of compaction tests. We also recommend that to verify the compaction of the fill pad in both horizontal and vertical directions, when the fill thickness will be more than one foot, the compaction test locations and the elevations should be spaced in both directions. In this manner it should be possible to show with a reasonable degree of accuracy the “density profile” through the backfill. This is an important element of the QA/QC program of the project in the event there is a problem with the fill or backfill performance and subsequent litigation. 10.1.8 Dry Weather Construction Since the near surface native soils have some fines content, we prefer the proposed construction should be completed during the dry season to mitigate any erosion related issues that may otherwise arise during the construction activities in the wet season. Erosion particularly happens, when uncontrolled surface runoff is allowed to flow over unprotected excavation areas of the site during the wet winter months. 10.1.9 Wet Weather Construction If the construction takes place during the wet weather, the near surface soils, which is anticipated as to be moisture sensitive, will be found susceptible to degradation and disturbed when get wet. Therefore, it may be necessary to adopt some remedial measures to enhance the subgrade conditions in this site if the construction takes place in the winter. The contractor should include a contingency in the earthwork budget for this possibility. The appropriate remedial measure is best determined by the geotechnical engineer during the actual construction of the project. The following remedial measures may be considered in this regard:  The earth contractor must use reasonable care during site preparation and excavation so that the subgrade soils are remained firm, unyielding, and stable.  Removal of the affected soil that is already wet exposing suitable bearing subgrades and replacing with imported free-draining materials as structural fills that can be compacted.  Aeration of the surficial materials during favorable dry weather by methods such as scarifying or windrowing repeatedly and expose to sunlight to dry near optimum moisture content prior to placement and compaction  Chemical modification of the subgrades with admixtures like hydrated lime or Portland cement, depending on the soil type.  Limiting the size of areas that are stripped of topsoil and left exposed.  Limiting construction traffic over unprotected soils. ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 24 of 41  Sloping excavated surfaces to promote runoff.  Limiting the size and type of construction equipment used.  Providing gravel or quarry spalls “working mat” over areas of protected subgrade.  Removing wet surficial soil prior to commencing fill placement each day.  Sealing the exposed ground surface by rolling with a smooth drum compactor or rubber-tired roller at the end of each day.  Providing upgradient perimeter ditches or low earthen berms and using temporary sumps to collect runoff and prevent water from ponding and damaging exposed subgrades.  Mechanical stabilization with a coarse crushed aggregate (such as sand and gravel, crushed rock, or quarry spalls) compacted into the subgrade, possibly in conjunction with a geotextile fabric, such as Mirafi 500X.  In the event earthwork takes place during the wet season, we recommend that special precautionary measurements should be adopted to minimize the impact of water and construction activities on the moisture sensitive soils.  It is recommended that earthwork be progressed part by part in small sections to minimize the soil’s exposure to wet weather. Traversing of construction equipment can cause considerable disturbance to the exposed subgrades, therefore, should be restricted within the specific drive areas. This will also prevent excessive widespread disturbance of the subgrades. Construction of a new working surface from an advancing working surface could be used to avoid trafficking the exposed subgrade soils.  Any excavations or removal of unsuitable soils should be immediately followed by the placement of backfill or concrete in footings.  At the end of each day, no loose on-site soils and exposed subgrades be left uncompacted or properly tamped, which will help seal the subgrade and thereby to minimize the potential for moisture infiltration into the underlying layers of fills or subgrades.  In case site filling must proceed during wet weather the contractor should include a contingency in the earthwork budget for the possibility of using imported clean, granular fill. For general structural fill purposes, we recommend that using well-graded sand and gravel, such as ‘Ballast’ or ‘Gravel Borrow’ per 2024 WSDOT Standard Specifications 9-03.9(1) and 9-03.14(1), respectively. Alternatively, ‘free- draining’ soil similar to the one described earlier in the Structure Fill Table may also be considered suitable as filling material for the wet weather construction. This type of fill refers to soils that have a fines content of 5 percent or less (by weight) based on the minus ¾-inch soil fraction. 10.1.10 Subgrade Degradation Prevention The near surface alluvium deposit (silt) containing high percentage of fines when will be used as subgrades will be susceptible to degradation during the wet weather conditions. To protect against subgrade degradation due to construction traffic we recommend a ‘working mat’ be placed over final prepared ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 25 of 41 subgrades. We recommend this ‘working mat’ consists of 12 inches thick free draining materials consist of crushed rocks or quarry spalls, possibly in conjunction with a geotextile fabric, such as Mirafi 500X placed underneath the crushed rocks or quarry spalls layer. Construction traffic should be limited to these ‘working mat’ areas. The stabilization materials can be as per the requirements recommended later on in Section 10.1.7, ‘Stabilization Materials’. 10.1.11 Site Drainage Surface Drainage The final site grades of the finished development must be such that surface runoff will flow by gravity away from the building and other structure, such as the pavement and sidewalks, using sloped and drainage gradients towards the local stormwater collection system. We recommend providing a minimum drainage gradient of about 2% for a minimum distance of about 10 feet from the building perimeter. Surface water should not be allowed to pond and soak into the ground surface near buildings or paved areas during or after constructions. A combination of using controlled surface drainage and capping of the building surroundings by concrete, asphalt, or low permeability silty soils will help minimize or preclude surfac e water infiltration around the perimeter of the building and beneath the garage basement floor slab. Paved areas should be graded to direct runoff to catch basins and or other collection facilities. Collected water should be directed to the on-site drainage facilities by means of properly sized smooth walled PVC pipe. Interceptor ditches or trenches or low earthen berms should be installed along the upgrade perimeters of the site to prevent surface water runoff from precipitation or other sources entering in to the lower area of the lot. It should be noted that surface water runoff from precipitation flows as a sheet flow over slope is considered to be the primary cause of surficial sloughing and triggering slope failure. Therefore, the surface drainage system should be designed in such a way that stormwater runoff over the finished lot must not create any sheet flow over the sloped areas of the site, instead, the stormwater runoff must be collected in drain pipes to discharge in approved discharge points at the toe of the slope. Surface drainage system and the water collection facilities should be designed by a professional civil engineer. Footing Excavation Drain Water must not be allowed to pond in the foundation excavations or on prepared subgrades either during or after construction. If due to the rainfall, runoff, seasonal fluctuations, groundwater seepage is encountered within footing depths, we recommend that the bottom of excavation should be sloped toward one corner to facilitate removal of any collected rainwater, groundwater, or surface runoff, and then direct the water to ditches, and to collect it in prepared sump pits from which the water can be pumped and discharged into an approved storm drainage system. Water handling needs will typically be lower during the summer and early fall months. ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 26 of 41 Footing Drain Footing drains should be used where (1) crawl spaces or basements will be below a structure, (2) a slab below the outside grade, and (3) the outside grade does not slope downward from a building. To reduce the potential for groundwater and surface water to seep into the interior spaces of the building we recommend that an exterior footing drain system be constructed around the perimeter of the building footings as shown in Figure 5, ‘Floor Slab, Footing, & Footing Drain’ of this report. The drains must be laid with a gradient sufficient to promote positive flow by gravity to a controlled point of approved discharge. The foundation drains should be tightlined separately from the roof drains to this discharge point. Footing drains should consist of at least 6-inch diameter, heavy-walled, perforated PVC pipe or equivalent. The pipe should be surrounded by at least 6 inches of free-draining gravel over the pipe and 3 inches of free-draining gravel below the pipe. The free-draining material may consist of open-graded drain rocks consisted of ¾” minus washed gravels should be wrapped up by a non-woven geotextile filter fabric (Mirafi 140N) to limit the ingress of fines into the gravel and the pipe. The free-draining material should contain less than 2 percent by weight passing the U.S. Standard No. 200 sieve (based on a wet sieve analysis of that portion p assing the U.S. Standard No. 4 sieve). The drains should be located along the outside perimeter of the spread footings or the footing stem walls. Also, the invert of the footing pipe should be placed at approximately the same elevation as the bottom of the footing or 12 inches below the adjacent floor slab grade, whichever is deeper, so that water will not seep through walls or floor slabs. The footing drains should discharge to an approved drain system and include cleanouts to allow periodic maintenance and inspection. Downspout or Roof Drain These should be installed once the building roof in place. They should discharge directly in tightlines to a positive, permanent stormwater collection system. Under no circumstances connect these tightlines to the perimeter footing drains. The drain is shown in Figure 5 of this report. 10.1.12 Temporary Excavations As we understand from the project plan that the proposed site development is likely to involve some overexcavation of approximately 8 feet depth below the current grades if a drywell infiltration system is to be planned in this site for managing the stormwater runoff from the proposed development. The inclination of the overexcavation embankment should be made as per the recommendations provided below. As a general rule, all temporary soil excavations in excess of 4 feet in height and less than 20 feet in depth, the side slopes should be adequately sloped back or properly shored in accordance with Safety Standards for Construction Work Part N, WAS 296-155-657 to prevent sloughing and collapse. As for the current ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 27 of 41 estimation purposes, in our opinion, the side slopes in the native soils (OSHA soil Type C - Sand) should be laid back at a minimum slope inclination of 1.5:1 (Horizontal:Vertical). However, estimation of the proper inclination of excavation side slopes should be made on-site after inspecting the soil and groundwater conditions, which will be revealed during the actual construction in the site. It should be recognized that slopes of the above gradients do ravel and require occasional maintenance. All temporary exposed slopes and excavations should be protected as soon as possible using appropriate methods to prevent erosion to occur during periods of wet weather. This can be achieved by installing a durable reinforced plastic membrane, jute matting, or other erosion control mats with proper anchorage to the ground. In addition, we recommend that experienced personnel of the contractor should regularly check the slope condition to notice if any signs of raveling or sloughing off is underway to prevent any catastrophic slope failure. All temporary soil cuts greater than 4 feet in height, if cannot be sloped back because of the limited horizontal distance to be available between the top of the excavation line and the property line, a properly shoring system is to be considered to prevent sloughing and collapse of the slope. Any excavation side inclinations will assume that the ground surface behind the cut slopes is level, that surface loads from equipment and materials are kept a sufficient distance away from the top of the slope. If these assumptions are not valid, we should be contacted for additional recommendations. Flatter slopes may be required if soils are loose or caving and/or water, are encountered along the slope faces. If such conditions occur and the excavation cannot stand by itself, or the excavation slope cannot be flattened because of the space limitations between the excavation line and the boundary of the property, temporary shoring may be considered. The shoring will assist in preventing slopes from failure and provide protection to field personnel during excavation. Because of the diversity available of shoring stems and construction techniques, the design of temporary shoring is most appropriately left up to the contractor engaged to complete the installation. We can assist in designing the shoring system by providing with detailed shoring design parameters including earth-retaining parameters, if required. Where sloped embankments are used, the top of the slopes should be barricaded to prevent vehicles and storage loads within 10 feet of the top of the slopes. Greater setbacks may be necessary when considering heavy vehicles, such as concrete trucks and cranes. If the temporary construction embankments are to be maintained during the rainy season, berms are suggested along the top of the slopes to prevent runoff water from entering the excavation and eroding the slope faces. All temporary slopes should be protected from surface water runoff. The owner and the contractor should be aware that in no case should the excavation slopes be greater than the limits specified in local, state, and federal safety regulations, particularly, the Occupational Safety ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 28 of 41 and Health Administration (OSHA) regulations in the “Construction Standards for Excavations, 29 CFR, part 1926, Subpart P, dated October 31, 1989” of the Federal Register, Volume 54, the United States Department of Labor. As mentioned above, we also recommend that the owner and the contractor should follow the local and state regulations such as WSDOT Section 2-09.3(3) B, Washington Industrial Safety and Health Act (WISHA), Chapter 49.17RCW, and Washington Administrative Code (WAC) Chapter 296-115, Part N. These documents are to better insure the safety of construction worker entering trenches or excavation. It is mandated by these regulations that excavations, whether they are for utility trenches or footings, be constructed in accordance with the guidelines provided in the above documents. We understand that these regulations are being strictly enforced and, if they are not closely followed, both the owner and the contractor could be liable for substantial penalties. Stability of temporary excavations is a function of many factors including the presence of, and abundance of groundwater and seepage, the type and density of the various soil strata, the depth of excavation, surcharge loadings adjacent to the excavation, and the length of time and weather conditions while the excavation remains open. It is exceedingly difficult under these unknown and variable circumstances to pre- establish a safe and maintenance-free temporary excavation slope angle at this time of the study. We therefore, strongly recommend that all temporary, as well as permanent, cuts and excavations in excess of 4 feet be examined by a representative of PGE during the actual construction to verify that the recommended slope inclinations are appropriate for the actual soil and groundwater seepage conditions exposed in the cuts. If the conditions observed during the actual construction are different than anticipated during this study then, the proper inclination of the excavation and cut slopes or requirements of temporary shoring should be determined depending on the condition of the excavations and the slopes. The above information is provided solely for the benefit of the owner and other design consultants, and under no circumstances should be construed to imply that PGE assumes responsibility for construction site safety or the contractor’s activities; such responsibility is not being implied and should not be inferred. Therefore, the contractor is solely responsible for designing and constructing stable, temporary excavations and should shore, slope, or bench the sides of the excavations as required to maintain stability of both the excavation sides and bottom. The contractor’s “responsible person”, as defined in 29 CFR Part 1926, should evaluate the soil exposed in the excavations as part of the contractor’s safety procedures. We expect that the excavation can be completed using conventional equipments such as bulldozers or backhoes. 10.1.13 Utility Support and Backfill Based on the soils encountered at the site within the exploration depths, the majority of the soils appear to be adequate for supporting utility lines; however, softer soils may be encountered at isolated locations, where, ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 29 of 41 it should be removed to a depth that will provide adequate support for the utility. A major concern with utility lines is generally related to the settlement of the trench backfill along utility alignments and pavements. The trench backfill settlement causes misalignment of the utility lines and breaking apart of the joints. Therefore, it is important that each section of utility be adequately supported on proper bedding material and properly backfilled. We recommend that the on-site geotechnical engineer should evaluate the final subgrades of the bottom of the utility trench to verify if the subgrade is competent to support the utility lines and the backfills, or the subgrades need some proofrolling and recompaction, or require overexcavation of unsuitable loose fills and replacement with suitable structural fills. We recommend that if needed the bottom grades of the utility trench must be adequately proofrolled and compacted to firm and unyielding conditions. A layer of geo-grid such as Mirafi 500X or equivalent should be placed on the proofrolled subgrades prior to placing the bedding materials and laying the utility lines. This should be decided on-site by the geotechnical engineer on-site based on the observed subgrade conditions at the bottom of the trench. It is recommend that utility trenching, installation, and backfilling conform to all applicable Federal, State, and local regulations such as WISHA and OSHA for open excavations. Pipe Bedding & Pipe Zone Trench backfill to be placed beneath, adjacent to, and for at least 2 feet above utilities line should consist of well-graded granular material with a maximum particle size of 1 inch and less than 10 percent by dry weight passing the US Standard No. 200 Sieve, and should meet the standards of ‘Gravel Backfill for Pipe Zone Bedding’ described in Section 9-03.12(3) of the 2024 WSDOT Standard Specifications. Trench backfill must be free of debris, organic material and rock fragments larger than 1 inch. The bedding materials should be hand tamped to ensure support is provided around the pipe haunches. Trench backfill should be carefully placed and hand tamped to about 12 inches above the crown of the pipe before any heavy compaction equipment is brought into use. In order to reduce the potential for damaging the utilities, heavy compaction equipment should not be permitted to operate directly over utilities until a minimum of two (2) feet of backfill will be placed. In general, pipe bedding should be placed in loose lifts not exceeding 6 inches in thickness and compacted to at least 90 percent of the fills’ maximum dry density value as to be determined by the laboratory Modified Proctor (ASTM D1557) test method. The fill materials within the pipe bedding and pipe zone, their thicknesses and compactions should be suitable for the utility system and materials installed, and in accordance with any applicable manufacturers' recommendations or local building department. Pipe bedding materials should be placed on relatively undisturbed native soil. Based on our field explorations, we anticipate relatively coarse-grained soils comprised of poorly graded gravel with cobbles. Some overexcavation and removal of cobbles should be anticipated at the pipe invert elevation to maintain a uniform grade for the utility installation. Where overexcavation is needed, additional pipe bedding materials should be placed to restore the grade. ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 30 of 41 Trench Backfills We recommend that the backfills to be placed 2 feet above the pipe and upto the final pavement subgrade level should be consisted of materials similar to ‘Gravel Borrow’ described in Section 9-03.14(1) or ‘Select Borrow’ as described in Section 9-03.14(2), of the 2024 WSDOT Standard Specifications. Where excavations occur in the wet, alternative such as ‘Select Granular Fill’ described earlier in Section 10.1.7, Structural Fills’ should be considered. Trench backfill must be free of roots, debris, organic matter and rock fragments larger than 3 inches. Other materials may be appropriate depending on manufacturer specifications and/or local jurisdiction requirements. For site utilities located within the City of Renton, bedding and backfill should be completed in accordance with the city specifications. As a minimum, 5/8 inch pea gravel or clean sand may be used for bedding and backfill materials. The trench backfills to be placed 2 feet above the pipe and upto the final pavement subgrade level should be compacted to 95 percent of the fills’ maximum dry density value as to be determined by the laboratory Modified Proctor (ASTM D-1557) test method. The backfill should be placed in lifts not exceeding 4 inches if compacted with hand-operated equipment or 8 inches if compacted with heavy equipment. Catch basins, utility vaults, and other structures installed flush with the pavement should be designed and constructed to transfer wheel loads to the base of the structure. The utility trenches should not be left open for extended periods to prevent water entry, accumulation, and softening of the subgrade. Should soft soils be encountered at the bottom of the trench, it should be overexcavated and replaced with select fills. As an alternative to undercutting, a Geotextile fabric or crushed rock may be used to stabilize the trench subgrade. Where water is encountered in the trench excavations, it should be removed prior to fill placement. Alternatively, quarry spalls or pea gravel could be used below the water level if allowed by the local authority or the project specifications. 10.2 Construction Monitoring Since this project involves so many aspects of geotechnical engineering related construction activities such as the identification of the existing fills, removals of the existing fills, overexcavations, excavation inclination, final native subgrades preparation and proofrolling, fill placement and compaction of fills, slab-on- grade-floor installation, footing embedment depth, and verification of the allowable bearing capacity value, we recommend that PGE’s on-site geotechnical engineer should inspect all the above activities. A list of inspection items are provided later on in Section 13.0, ‘Geotechnical Special Inspection’ of this report. It is recommended that the above construction activities be monitored by a representative from our firm since we have the prior knowledge, familiarity, and better understanding with our recommendations. ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 31 of 41 10.3 Foundation Recommendations As mentioned earlier, the footings of the proposed new building addition can be supported on conventional shallow spread footings and continuous strip footings to be placed directly over the final native subgrades consisted of denser native soil deposit encountered at approximately 2 feet depth below the existing grades. As recommended earlier in 9.0, ‘Executive Summary’ of this report, the final native subgrades must be prepared as ‘competent’ native subgrades by thoroughly and adequately ‘redensification’ and ‘proofrolling’ of the native subgrades to firm and unyielding conditions, prior to placing the footings. Allowable Bearing Capacity The footings placed directly above the final ‘competent’ native subgrades may be designed for an allowable net bearing capacity value of 2000 psf. The “net allowable bearing pressure” refers to the pressure that can be imposed on the soil at foundation level resulting from the total of all dead loads plus the long - term live loads, exclusive of the weight of the footing or any backfill placed above the footing, i.e., these loadings can be ignored in calculating footing sizes. For short-term loads, such as wind and seismic (earthquake), a 1/3 increase in the above net allowable capacity can be used. We recommend that continuous footings have a minimum width of 18 inches and individual column footings a minimum width of 24 inches. All exterior footings should bear at least 18 inches below the final adjacent finish grade to provide adequate confinement of the bearing materials and frost protection. Settlement Based on our settlement potential evaluation of the shallow foundation options, we anticipate that properly designed and constructed foundations supported on the recommended bearing materials should experience total settlement of less than 1 inch for the allowable bearing pressures presented above. Differential settlement could be on the order of ¼ to ½ inch between similarly loaded foundations over a distance of 50 feet of continuous footings. This estimation was done without the aid of any laboratory consolidation test data, but on the basis of our experience with similar types of structures and subsoil conditions. The soil response to applied stresses caused by building and other loads is expected to be predominantly elastic in nature with most of the settlements occurring during construction as loads are applied; however, due the fines content of the site soils, the estimated settlements could occur over a longer time, and disturbance of the foundation subgrades during construction could result in larger settlements than predicted. ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 32 of 41 Lateral Load Resistance Lateral foundation loads can be resisted by friction between the foundation base and the underlying supporting soil, and by passive earth pressure acting on the face of the embedded portion of the fo undation below the grades. For frictional resistance, a coefficient of 0.35 can be used. For passive earth pressure, the available resistance can be computed using an equivalent fluid pressure of 300 pcf, which includes a factor of safety of 1.5. This value assumes the foundation must be poured "neat" against the undisturbed native soils or structural fill placed and compacted as described earlier in Section 10.1.8, 'Fill Placement and Compaction Requirements' of this report. The passive earth pressure and friction components may be combined provided that the passive component does not exceed two-thirds of the total resistance. Footing Subgrade Inspection We recommend that PGE representative examine the bearing materials prior to placing forms or rebar. Variations in the quality and strength of the potential bearing soils can occur with depth and distance away from the test pits. Therefore, a careful evaluation of the bearing material and the design bearing capacity value as recommended in this report must be verified at the proposed footing locations at the time of footing construction. 10.4 Slab-on-grade Floor Slab-on-grade floor for the new building addition should not be placed over topsoils, uncontrolled existing fills, loose and yielding native soils, or any soils containing heavy roots. The slab-on-grade floor should bear directly on structural fill pad of a minimum of 12 inches of compacted thickness, which must be adequately compacted and to be placed on ‘redensified’ and adequately ‘proofrolled’ final native subgrades, considered to be as ‘competent’ native subgrades as described earlier in Section 9.0, ‘Executive Summary’ of this report. The ‘competent’ native subgrade is described as the subgrade that is compacted to firm and unyielding conditions, which will be evidenced during the proofrolling. The fills thickness may vary based on the final floor elevation and the depth of the acceptable final native subgrades to be determined by the PGE’s geotechnical engineer. After the final slab subgrade preparation is completed, the slab should be provided with a capillary break to retard the upward wicking of ground moisture beneath the flo or slab. The capillary break would consist of a minimum of 6-inch thick clean, free-draining sand or pea gravel. The structural fill requirements specified in Section 10.1.7, Structural Fill, could be used as capillary break materials except that there sho uld be no more than 2 percent of fines passing the no. 200 sieve. Alternatively, ‘Gravel Backfill for Drains’ per 2023 WSDOT Standard Specifications 9-03.12(4) can be used as capillary break materials. This layer should ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 33 of 41 be placed and compacted to an unyielding condition. Where moisture by vapor transmission is undesirable, we recommend the use of a vapor barrier such as a layer of durable plastic sheeting (such as Crossstuff, Moistop, or Visqueen) between the capillary break and the floor slab to prevent th e upward migration of ground moisture vapors through the slab. This is particularly importance where moisture migration through the slab is an issue, such as where adhesives are used to anchor carpet or tile to the slab. During the casting of the slab, care should be taken to avoid puncturing the vapor barrier. At owner’s or architecture’s discretion, the membrane may be covered with 2 inches of clean, moist sand as a ‘curing course’ to guard against damage during construction and to facilitate uniform curing of the overlying concrete slab. The addition of 2 inches of sand over the vapor barrier is a non -structural recommendation. A cross-sectional view of the slab-on-grade floor showing the above features is provided in Figure 5, Footing, Slab-on-grade, Footing Drain of this report. The final slab subgrade consisted of adequately compacted, new imported structural fills, a modulus of subgrade reaction value of about 150 pounds per cubic inch (pci) can be used to estimate slab deflections, which could arise due to elastic compression of the subgrades 11.0 Infiltration Potential Evaluation As a part of the scope of this geotechnical study the permeability characteristic of the native soil was evaluated to assess the feasibility of using a below grade infiltration system in this site for managing the stormwater runoff from the proposed new building addition. To achieve this, the surface and subsurface conditions in the proposed new infiltration system area was observed as a basis for determining a site-specific measured infiltration rate and assessing the feasibility of the subsurface soil to support the infiltration system. Specifically the scope of services includes the following:  Reviewing the available geologic, hydrogeologic, and geotechnical data for the site area;  Exploring surface and subsurface conditions by reconnoitering the site and monitoring the excavation of two test pits at the site;  Performing one small-scale pilot infiltration test (PIT) in one of the test pits in accordance with the 2021 King County Surface Water Design Manual (KCSWDM);  Performing laboratory sieve analysis test per ASTM method to determine the grain-size distribution of the native soil;  Describing surface and subsurface conditions, including soil type and depth to groundwater if encountered;  Providing our opinion about the feasibility of on-site infiltration in accordance with the 2021 KCSWDM, including a design infiltration rate based on the measured infiltration rate from our in- situ infiltration testing; ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 34 of 41  Preparing this written Soils Report in accordance with the section C.2.3.1 of 2021 KCSWDM, summarizing our site observations and conclusions and our recommendations and design criteria - along with the supporting data. King County has adopted per the King County Code Chapter 2.98 the 2021 KCSWDM for design of stormwater management system. We evaluate the feasibility of stormwater infiltration at the site using the procedure for a soil report, investigation, and infiltration rates testing in the 2021 KCSWDM. We have assumed that, if infiltration facilities are planned in this site, they will serve less than about 1 acre of tributary area. The 2021 KCSWDM states that groundwater mounding analysis is not required for infiltration facilities serving less than 1 acre of tributary area provided that a minimum 3-foot separation is maintained between the bottom of the facility and restrictive layer such as seasonal high groundwater level or any low permeability stratum (i.e., recessional lacustrine deposits and glacial till). Infiltration Test The infiltration test was conducted using the procedure outlined for small-scale Pilot Infiltration Test (PIT) in Reference 6-A of 2021 KCSWDM manual. The test was conducted in the test pit TP-1 at approximately 4 feet (48 inches) depth below the current grades in the native, light gray, gravelly sand deposit. The test pit was measured approximately 4 feet (length) by 3 feet (width) with an area encompassing about 12 square feet. As per the manual guideline, the test includes three phases: a pre-soaking period of 6 hours, a constant or steady-head phase, and a falling-head phase. Following the test depth reached at 4 feet, a measuring staff gauge with 1/8-inch divisions was placed at the base of the test pit to monitor the water level drop during the testing. Then water was poured into the test pit using a garden hose which was sourced from an outlet of the exiting residence. The water was poured via a rigid plastic pipe of 6-inch diameter, on a splash board placed at the base of the test pit, to minimize the side-wall erosion or excessive disturbance, turbulence, and scouring at the test pit bottom. Excessive erosion and bottom disturbance will result in clogging of the infiltration receptor and yield lower than actual infiltration rates. Following the completion of the test pit preparation, an attempt was made to fill up the test pit with pouring water for an almost hour and half to build up a 12 inches head of water above the bottom of the test pit. However, it was never achieved hence the test had to terminate. We believe that the native soil consisted of gravely sand caused the water to drain fast and as a result the head was never built up. During the test, instantaneous flow rate readings were taken and based on that the actual infiltration rate was determined as 8 inches per hour. After the test was abandoned, the bottom of the test pit was advanced further below to almost 8 feet depth below the grade to determine the type of sediment that accumulated at the bottom of the test depth, and to observe if there is any presence of geological features like restrictive layer (silt, clay deposit or glacial till), heavy mottling signs, groundwater, and mounding within the ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 35 of 41 maximum exploration depth. None of these features were noticed and the gravelly sand deposit was observed continued upto the bottom of the test pit. Final Design Infiltration Rate The actual infiltration rate obtained from our field PIT test is representative of the measured (unfactored) infiltration rate of the soil test at the test depth at the test pit location, TP-1. The section 5.2.1 of 2021 KCSWDM recommends that correction factors be applied to the measured infiltration rates to estimate the long-term deign infiltration rate. Different correction factors are applied depending on the facility type. The correction factors account for the number of infiltration tests done in relation to the size of the infiltration area, site soil variability, test method, and other factors. The foll owing equations are used to determine the final design infiltration rate. Ksat Design = Ksat Initial x CFT, where, Ksat initial and Ksat design are the field measured and the final design infiltration rates respectively, and Total Correction Factor, CFT = CFg x CFt x CFm The table below summarizes the correction factors and the total correction factors that, in our opinion, are suitable for the design of the system. Correction factors were selected based on our project understanding, observed soil conditions, criteria provided in the manual, and our local experience assisting in the design of stormwater infiltration facilities. Table 5 - Infiltration Rate Test Pit No. Test Depth, Inches Soil Description @ Test Depth Field Measured Uncorrected Infiltration Rate (in/hr) Correction Factors Applied Corrected Infiltration Rate (in/hr) Ksat - Initial (Field) Rate CFg CFt CFm CFT Ksat - (Design Rate) TP-1 48 Lt. Gray, Sand w/Gravel 8 1.0 0.5 0.9 0.45 3.6 In/hr – inches/hour CFg – Correction factor for geometry - 1.0* CFt – Correction factor for test method uncertainty - for small scale PIT 0.5 CFm – Correction factor for long-term conductivity loss due to plugging - for medium sand 0.9 CFT – Total correction factor ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 36 of 41 *Based on the final geometry of the infiltration facility, the CFg correction factor need to be adjusted by the project civil engineer. The above final design infiltration rate is applicable to facility that will be located in proximity to the infiltration test location, at or near the test depth, in the same soil tested, and in no groundwater condition within the test pit depth. Should any of the above criteria is found to be different then PGE should be contacted to perform additional in-situ PIT at the proposed location of the infiltration facility. A contingency plan is to be kept in place if such situation occurs. Performance/Verification Testing – Field percolation performance verification testing shall be conducted as per section 5.2.1 ‘Performance Testing’ of 2021 KCSWDM to demonstrate that the final design infiltration rate recommended above is valid, which is critical to ascertain the infiltration facility would perform as designed. In addition to the verification testing, we recommend that the soil and groundwater conditions should be verified at the proposed infiltration system location prior to installing the system. The verification is critical to find out if groundwater, perched water seepage, signs of mottling, and restrictive layer (like till) are present at the infiltration facility. Also, the verification should be made to ascertain if the vertical separation requirement below the bottom of the facility is available. PGE should observe construction of the infiltration system. Due to the possibility of the variability of the native soils across the depth and the horizontal extent of the site, the soils may change, hence their infiltration rates. In the event, the soil condition and the infiltration rate are found to be different during the performance testing than the soil conditions and the final design infiltration rate obtained during this study, the infiltration system may need to be relocated and redesigned from the original plan to reflect the actual soil condition and the infiltration rate to be encountered during the performance testing. A contingency plan is to be kept in place if such situation occurs. Infiltration Feasibility It is our opinion that the native, gravelly sand (USCS Soil Classification: SP) encountered below the topsoils is considered suitable as a ‘full-infiltration’ receptor as defined in the 2021 KCSWDM section C.2.3 for stormwater to be generated by the new impervious surfacing for the proposed new addition. Our PIT test was performed on this soil at 4 feet depth below the grade. A sieve analysis test was performed on this material and the result is shown in Figure B-1 of this report. The gravelly sand is described as ‘Sand’ (USCS Soil Class: SP) report. There was no groundwater, perched water seepage, signs of mottling, restrictive layer (like till), and mounding was noticed within the maximum exploration depth of 8 feet. Based on these geological factors, in our opinion, the sand deposit can support a ‘full-infiltration’ system such as a drywell according to sections C.2.3 and C.2.3.2 of the 2021 KCSWDM. For designing the ‘limited-infiltration’ ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 37 of 41 drywell system within the King County Urban Growth Area, section C.2.3.4 specifies for each 1,000 square feet of new impervious area surface area, the gravel filled drywell should have a minimum volume of 360 cubic feet in soils classified as sand. We recommend that any proposed infiltration system be placed as to not negatively impact any proposed or existing nearby structure and also meet all required setbacks from the existing property lines, structures, and sensitive areas as discussed in the drainage manual. The various aspects of the design requirements described in the 2021 KCSWDM should be incorporated into the system design. The 2021 KCSWDM requires a minimum 3 feet or more of permeable soil beneath below grade infiltration trench or drywell bottom for their proper functioning. In the test pit location we observed that the permeable soil extends upto the maximum exploration depth of approximately 8 feet depth below the existing grade. We believe that the observed permeable soil is likely to e xtend further below the test pit depth, which must be verified during the actual installation of the infiltration system. W e expect that if the proposed drywell is designed properly will be able to maintain the minimum 3 feet of permeable soil requirement below the system. Based on the minimum depth requirement the final size and the bottom elevation of the drywell or the infiltration trench should be determined. The vertical separation depth is required for providing space for the stormwater in the drywell to infiltrate within the soil in the minimum depth requirement. Additional Study We recommend that an additional study is to be performed by a hydro -geologist to determine if there will be any impact of the highest water level in Cedar River (typically occurs in the wet winter months) on the proposed infiltration system. The result of the study will provide if the groundwater condition observed in our test pit in the month of May would remain same due to the impact of the highest water level in the river. 12.0 Additional Services Additional services described below can be performed by PGE in the event the project requires such services. These services will be performed upon written authorization of the client or the civil engineer, and with additional cost to perform such services, under a separate contract between PGE and the client. 12.1 Design Phase Engineering Services As the geotechnical engineer of record for the proposed development, at owner’s option, PGE can perform a review of the final project plans and specifications to verify that the geotechnical recommendations of this report have been properly interpreted and incorporated into the project final design and specifications, and that the impact of the final site grades, the proposed building and its footing, and any other structure. ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 38 of 41 12.2 Construction-time Testing and Inspection As the geotechnical engineer of record for the proposed development, at owner’s option, PGE can provide geotechnical consultation, material testing, and construction monitoring servi ces during the construction of the project recommended earlier in Section 10.2, ‘Construction Monitoring’ of this report. These services are important for the project to confirm that the earthwork and the general site development are in compliance with the general intent of design concepts, specifications, and the geotechnical recommendations presented in this report. Also, participation of PGE during the construction will help PGE engineers to make on-site engineering decisions in the event that any variations in subsurface conditions are encountered or any revisions in design and plan are made. PGE can assist the owner before construction begins to develop an appropriate monitoring and testing plan to aid in accomplishing a fast and cost-effective construction process. 13.0 Geotechnical Special Inspection The construction of the proposed development in this site involves several aspects of the geotechnical engineering that are considered to be critical for the successful completion of the project and continue that throughout the project life. Therefore, PGE recommends that the following geotechnical special inspection services to be performed during the construction of the proposed development. According to PGE, the following items should be considered as a minimum but not limited to.  A professional geotechnical engineer should be retained to provide geotechnical consultation, material testing, and construction monitoring services during the construction of the project.  A pre-construction meeting should be held on-site to discuss the geotechnical aspects of the development and the special inspection services to be performed during the construction.  The site preparation activities including but not limited to stripping, cut and filling, final subgrade preparation for foundation, floor slab, paved driveway, and retaining wall be monitored by a geotechnical engineer or his representative under the engineer’s supervision.  A list of the possible items that require special geotechnical inspection and approval by the geotechnical engineer is as follows:  Stripping of topsoils.  Removal of loose, native soils, and the uncontrolled, existing fills.  Compaction and proofrolling of any exposed native subgrades that are intended to provide direct support for any load bearing structure such as new fill pad, slab-on-grade floor, footing, retaining wall, and paved driveway.  Any structural fills to be used in this site, and structural fills placement and its compaction. ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 39 of 41  Temporary or permanent excavation inclinations, and excavation stability.  Backfilling and its compaction, and drainage behind retaining walls.  The footing bearing materials, bearing capacity value, and the embedment depth of the footings prior to placing forms and rebars.  Subgrade preparation for soil supported slab-on-grade floors.  Subgrade preparation for paved driveways.  Compaction of CSBC, CSTC, and laying of concrete pavement in driveway.  Site drainage.  Installation of drainage system such as footing excavation drain and footing drain, and daylighting of such drains and downspout or roof drains.  Bedding and the backfilling materials, and backfilling of utility lines.  Performing field verification percolation test at the proposed drywell location.  Observing the construction of drywell system.  Any other items specified in the approved project plans to be prepared by other consultants relevant to the geotechnical aspect of the project. 14.0 Report Limitations The conclusions and recommendations presented in this report are based on our soil investigation, the laboratory test results, geological literature review, and our engineering evaluation. The study was performed using a mutually agreed-upon scope of work between PGE and the client. It should be noted that PGE cannot take the responsibility regarding the accuracy of the information provided in the project plan prepared by other consultants. If any of the information considered during this study is not correct or if there are any revisions to the plans for this project, PGE should be notified immediately of such information and the revisions so that necessary amendment of our geotechnical recommendations can be made. If such information and revisions are not notified to PGE, no responsibility should be implied on PGE for the impact of such information and the revisions on the project. Variations in subsurface (soil and groundwater) conditions may reveal during the construction of the proposed below grade infiltration system. The nature and the extent of the subsurface variations may not be evident until construction occurs. If any subsurface conditions are encountered at the site that are different from those described in this report, we should be notified immediately to review the applicability of our recommendations if there are any changes in the project scope. This report may be used only by the client and for the purposes stated, within a reasonable time from its issuance. Land use, site conditions (both off and on-site), or others factors including advances in our understanding of applied science, may change over time and could materially affect our findings. Therefore, ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 40 of 41 this report should not be relied upon after 24 months from its issuance. PGE should be notified if the project is delayed by more than 24 months from the date of this report so that we may review to determine that the conclusions and recommendations of this report remain applicable to the changed conditions. The scope of our work does not include services related to construction safety precautions. Our recommendations are not intended to direct the contractors' method, techniques, sequences or procedures, except as specifically described in our report for consideration in design. Additionally, the scope of our work specifically excludes the assessment of environmental characteristics, particularly those involving hazardous substances. This report including its evaluation, conclusions, specifications, recommendations, or professional advice has been prepared for planning and design purposes for specific application to the proposed project in accordance with the generally accepted standards of local practice at the time this report was written. No warranty, express or implied, is made. This report is the property of our client Patty Thumann, and has been prepared for the exclusive use of our client and its authorized representatives for the specific application to the proposed development at the subject site in Renton, Washington. It is the client's responsibility to see that all parties to this project, including the civil engineer, designer, contractor, subcontractor, future homeowner, etc., are made aware of this report in its entirety. The use of information contained in this report for bidding purposes should be done at the contractor's option and risk. Any party other than the client who wishes to use this report shall notify PGE of such intended use and for permission to copy this report. Based on the intended use of the report, PGE may require that additional work be performed and that and updated report be reissued. Noncompliance with any of these requirements will release PGE from any liability resulting from the use this report. ___________________________________________________________________________________________________________________________ Proposed New Addition Geotechnical Engineering Study 13411, SE 151st St Renton, WA 98058 PGE Project No. 24-754 June 28, 2024 Page 41 of 41 Closure We trust the information presented in this report is sufficient for your current needs. We appreciate the opportunity to provide the geotechnical services at this phase of the project and look forward to continued participation during the design and construction phase of this project. Should you have any questions or concerns, which have not been addressed, or if we may be of additional assistance, please do not hesitate to call us at 425-218-9316. Respectfully submitted, Santanu Mowar, P.E. D:\Geotechnical\2024-proj\24-754 Attachments: Figure 1 Vicinity Map Figure 2 Aerial Site View Figure 3 Site & Exploration Plan Figure 4 Flood Hazard Map Figure 5 Footing, Slab-on-grade, Footing Drain Details Figure 6 Notes Appendix A Soil Test Pit Log Appendix B Laboratory Test Report N Site Figure 1 – Vicinity Map N Figure 2 – Aerial Site View Proposed Addition Area Figure 3 – Site & Exploration Plan TP-1 N Figure 4 – Flood Hazard Map FOOTING, SLAB-ON-GRADE, & FOOTING DRAIN Conceptual only (not a construction drawing) Footing Wall Slope backfill w/ minor slope C J D K A Floor Level F Concrete slab-on-grade B 6" min. gravel on top 3" min. gravel at bottom H G E L Vapor Barrier Capillary Break Layer Gravel Base Footing must be placed on native subgrade, to be prepared as ‘competent’ subgrade, which must be verified on-site by PGE’s geotechnical engineer. Footings must not be placed over topsoils, and underlying native soil containing root zone Drain Rocks Drain Pipe Mirafi 140N Footing Excavation Slope Compacted Backfills Roof Drain New fill pad under the slab must be placed over ‘competent’ native subgrade G C New imported structural fill pad below slab IActual fill thk. below the slab-on-grade floor should be decided based on final floor elev., removal depths of topsoil, root zone, and tree rootball, and depth of final native ‘competent’ subgrade to be encountered, which must be verified on-site by PGE’s geotechnical engineer. Fills must be placed & compacted as per Curing Sand Layer A Figure 5 Not to Scale Project No. –24-754 Project – Patty Thumann Site – New Addition 13411, SE 151st St., Renton, WA 98058 FOOTING, SLAB-ON-GRADE, & FOOTING DRAIN Final native subgrades supporting the footings, the slab-on-grade floor, or the new structural fill pad directly, must be thoroughly ‘redensified’ and then adequately ‘proofrolled’ to firm & unyielding conditions to prepare the final native subgrades as ‘competent’ native subgrades, prior to placing the footings, slab-on-grade floor, and new fill pad. The allowable bearing capacity value of 2000 psf to be verified on-site by PGE’s geotechnical engineer @ the final footing subgrades or at the top of the newly placed compacted fill pad, prior to placing rebars and forms. Topsoils and tree rootbulbs, and any unsuitable native soil containing heavy root zone must be removed completely prior to the preparation of the final ‘competent’ native subgrades. Excavation face slope should be determined based on the actual soil and groundwater conditions to be exposed during the construction. Non-woven Geotextile Filter Fabric -Mirafi 140 N must wrap around the drain rocks to be placed around the footing drain pipe and the vertical drainage layer to be installed against the wall, to prevent migration of fines into the drain rocks. A B C D K Capillary Break layer – min. 6" thk, of free-draining 5/8-inch crushed rocks containing no more than 2% fines or pea-gravel. Slab-on-grade floor should be placed directly on a capillary break layer in unheated areas e.g., garage, storage rooms. E H L NOTES:- F G Drain rocks -the drain pipe must be enveloped by drain rocks consisted of ¾” minus washed gravel (free draining). Stormwater roof drain,must be tightlined and must not be connected to footing drain. Pipe should be sloped towards approved discharge point so that no backflow should occur into the pipe. J Curing Sand Layer -as an additional layer can be placed above the vapor barrier or plastic membrane to guard the membrane against damage during construction and to facilitate uniform curing of the overlying concrete slab. Vapor Barrier – a durable 10 to 15-mil. plastic membrane be placed over capillary break layer as a vapor retarder. Backfill compaction -void areas to be created by overexcavation of topsoils, rootzone, and tree rootbulbs, for achieving footing embedment depth of minimum 18 inches below the current grades, and below the slab-on-grade floor must be backfilled with approved new structural fills. The fills must be compacted to 95% of fills’ max. dry density value (to be determined as per the laboratory Mod. Proctor Test ASTM D1557). The fills to be placed should be compacted with care within the horizontal distance equal to the height of the footing wall to avoid over compaction and overstressing the footing wall & the footing. No heavy compaction equipment such as vibratory roller or hoe-pac be used to compact the fills because of these equipment will impose excess surcharge loading on the wall, causing a lateral instability to the footing wall & the footing. Fills must be placed in 12 inch thick loose lifts and to be compacted with a walk-behind, hand-held, big, heavy-duty vibratory plate compactor (similar to TMG-PC33OK Reversible Plate Compactor with 14 HP Kohler Engine) close to the footing wall. The new imported structural fills should be used as per the recommendations provided in PGE’s geotechnical report 24-754. Gravel base -Min. 6" thk compacted (95% or more), which must be extended 6" beyond both sides of the footing. Wall Footing Drain - 6" minimum diameter, perforated or slotted rigid concrete, metal, or plastic pipe with tight plastic joints, with a positive gradient (~2%) towards thee discharge ends sufficient to generate gravity flow w/out backflow to occur into the pipe, and provided with accessible cleanouts at regular intervals. The pipe must be taken to final discharge point (approved). The pipe must be placed as low as possible, at least 6 inches below footing or crawl space. Perforations (¼” max. diameter) to be in lower half of pipe, with lower quadrant segment un-perforated to facilitate water flow. Slotted pipe to have 1/8" maximum width slots. Must NOT be tied to roof downspout or perimeter footing grain lines. The drain pipe must be enveloped w¾” minus washed gravels (free draining), which then be wrapped around with Mirafi 140N to prevent migration of fines into the din rocks and clog the pipe. Fill Thickness Under Slab -Actual fill thk. should be decided by the on-site geotechnical engineer based on the final floor elev. and the depth of the final native ‘competent’ subgrade to be encountered, which must be verified on-site by PGE’s geotechnical engineer. Fills must be placed & compacted as per the recommendations provided in I A M PGE’s Geotechnical Report -In addition to the above recommendations the designer and the contractor of the project must read PGE’s geotechnical report no. 24-754, for additional recommendations and better understanding of the above recommendations. Figure 6 Not to Scale Project No. –24-754 Project – Patty Thumann Site – New Addition 13411, SE 151st St., Renton, WA 98058 Appendix A Soil Test Pit Log Figure A-1 Not to Scale TEST PIT –1 0 ft 1 ft 2 ft 3 ft 4 ft 5 ft 6 ft 0 ft Soil Layer Descriptions Laboratory Test ResultsSample Depth Sample Nos.Moist. Content - #200 Sieve Soil Layer Depth USCS Soil Class Test Pit Depth4 ft4 ft Test Pit Width Surface Elev. Ft.Date of Excavation Test Pit Depth Water/Seepage Depth Mottling Depth Ground Cover Cave in Depth Notes - Landscape grass 8 ft None Top Soils – Brn., Sandy Silt w/ organics & root V. Moist, Soft 0 – 0.5 ft 2 1 None 05/21/2024 Test Pit Location See site plan Permeability None 2 Project No. –24-754 1 0.5 ft –8 ft 7 ft 8 ft Field Logging by ASTM D5434-12 Soil Sampling by ASTM D-75-19 Visual-Manual Soil Identification by ASTM D2488-17 9 ft 10 ft Lt. Gray, Sand w/ small to large size Gravel, Cobble, Boulder Moist, Loose upto 2 ft & Med. dense below this depth SP S-1 @ 5 ft 14.8 %4.9 % (Sieve Test Graph B-1) Infiltration test performed @ 4 ft below grade; Final design infiltration rate K ~ 3.6 in/hr Project – Patty Thumann Site – New Addition 13411, SE 151st St., Renton, WA 98058 KEY TO EXPLORATION LOG Sample Descriptions: Classification of soils in this report is based on visual field and laboratory observations, which include density/consistency, moisture condition, grain size, and plasticity estimates, and should not be construed to imply field or laboratory testing unless presented herein. Visual-manual classification methods in accordance with ASTM D-2488-17 were used as an identification guide. Where laboratory data available, soil classifications are in general accordance with ASTM D2487-17. Soil density/consistency in borings is related primarily to the Standard Penetration Resistance values. Soil density/consistency in test pits is estimated based on visual observations of excavations. Undrained shear strength = ½ unconfined compression strength. RELATIVE DENSITY OR CONSITENCY VS. SPT N-VALUE COARSE GRAINED SOILS: SAND OR GRAVEL FINE GRAINED SOILS: SILT OR CLAY Density N (Blows/ft.) Approx. Relative Density (%) Consistency N (Blows/ft.) Approx. Undrained Shear Strength (psf) Very Loose 0 – 4 0- 15 Very Soft 0 – 2 <250 Loose 4 – 10 15 – 35 Soft 2 – 4 250 –500 Medium Dense 10 – 30 35 – 65 Medium Stiff 4 – 8 500 – 1000 Dense 30 – 50 65 – 85 Stiff 8 – 15 1000 – 2000 Very Dense >50 85 – 100 Very Stiff Hard 15 – 30 > 50 2000 – 4000 > 4000 MOISTURE CONTENT DEFINITIONS Dry Absence of moisture, dusty, dry to the touch Moist Damp but no visible water Wet Visible free water, from below water table DESCRIPTIONS FOR SOIL STRATA AND STRUCTURE General Thickness or Spacing Structure General Attitude Parting < 1/16 in Pocket Erratic, discontinuous deposit of limited extent Near Horizontal 0 - 10 deg Seam 1/16 - 1/2 in Lens Lenticular deposit Low Angle 10 - 45 deg Layer ½ - 12 in Varved Alternating seams of silt and clay High Angle 45 - 80 deg Stratum > 12 in Laminated Alternating seams Near Vertical 80 - 90 deg Scattered < 1 per ft Interbedded Alternating Layers Numerous > 1 per ft Fractured Breaks easily along definite fractured planes Slickensided Polished, glossy, fractured planes Blocky, Diced Breaks easily into small angular lumps Sheared Disturbed texture, mix of strengths Homogeneous Same color and appearance throughout Appendix B Laboratory Test Reports Particle Size Distribution Report PE R C E N T F I N E R 0 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 24.8 19.7 11.5 23.8 15.3 4.9 6 i n . 3 i n . 2 i n . 1½ i n . 1 i n . ¾ i n . ½ i n . 3/ 8 i n . #4 #1 0 #2 0 #3 0 #4 0 #6 0 #1 0 0 #1 4 0 #2 0 0 TEST 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: TP-1Sample Number: S-1 Depth: @ 5 ft below grade Client: Project: Project No:Figure Lt. Gray, Poorly graded Sand w/ Gravel 3 inch 1.5 inch 1 inch 3/4 inch 1/2 inch 3/8 in #4 #10 #20 #40 #60 #80 #100 #140 #200 100.0 89.0 82.5 75.2 69.2 65.2 55.5 44.0 28.8 20.2 15.8 12.1 9.9 6.8 4.9 NP NV NP SP A-1-a 40.9296 28.8254 6.6044 3.0512 0.9170 0.2320 0.1513 43.65 0.84 05-21-24 05-23-24 Sraboni Santanu Mowar, PE Principal 05-21-24 Patty Thuman New Building Addition @ 13411, SE 151st St, Renton, 98058 24-754 PL=LL=PI= USCS (D 2487)=AASHTO (M 145)= D90=D85=D60= D50=D30=D15= D10=Cu=Cc= Remarks *(no specification provided) B-1 Appendix B: Septic Design 7 2 74 7 0 6 8 7 6 78 200 ' SL1 R E S E R V E B E D 14' 7 9 ' 14' 7 9 ' 100 ' M I N SL4 SL3 5' MI N TA N K NEW ADU (2 BEDROOM MAX) EXISTING 3 BEDROOM HOUSE 5' MI N TA N K 5' MIN TANK SL2 418' MIN. D . F . 5 ' M I N . 10 ' MI N . 1 2 3 CONTROL POINT PROP CORNER ELEV=78' 78 CONTROL PANEL IN LINE OF SIGHT OF PPUMP CHAMBER 1,500 GALLON SEPTIC TANK1 3"Ø TRANSPORT LINE 2 3 4 LEGEND 1,500 PUMP CHAMBER SL#SOIL LOG W WATER LINE 4004 NE 4TH ST., #107-508 RENTON, WA 98056 425.457.6029 425.432.4461 FAX WI L L I A M S R E S I D E N C E ON - S I T E S E W A G E D I S P O S A L D E S I G N 13 4 1 1 S E 1 5 1 S T S T R E E T R E N T O N KI N G C O U N T Y 4" MAX NTSINSTALL CLEANOUTS ON ALL LATERALS LATERAL CLEANOUT/ MONITORING PORT 6" PERF. PVC PIPE WITH 1/2"∅ HOLES DRILLED 3" O.C. FOR BOTTOM 12" OF PORT. ORIGINAL GROUND SURFACE CUT SLOT IN 6" PVC FOR UPTURN LATERAL INSTALL 1/2" REBAR THROUGH PVC PIPE TO EXTEND TWO FEET ON EACH SIDE BOTTOM OF TRENCH (INFILTRATIVE SURFACE) SET CAP FLUSH WITH FINISHED GRADE FPT CAP MPT X SOC DRILL ONE HOLE UPWARD AT END OF LATERAL FOR TEST. 45° ELBOW LATERAL END FINISHED GRADE SECTION VIEW 1.THE APPROVAL OF THE ON-SITE SEWAGE DISPOSAL DESIGN IS NOT A PERMIT TO CLEAR THE PARCEL. A SEPARATE PERMIT MAY BE REQUIRED FROM THE COUNTY TO CLEAR ANY PORTION OF THE PARCEL. 2.SENSITIVE AREAS MAY BE PRESENT NEAR THE DRAIN FIELD AREA THAT MAY EFFECT THE INSTALLATION OF THE DRAIN FIELD. SEPARATE PERMITS MAY BE REQUIRED FROM THE COUNTY FOR SENSITIVE AREA ISSUES. 3.EXISTING UTILITY LOCATIONS SHOWN HEREON ARE APPROXIMATE ONLY. IT SHALL BE THE CONTRACTOR'S RESPONSIBILITY TO DETERMINE THE EXACT VERTICAL AND HORIZONTAL LOCATION OF ALL EXISTING UNDERGROUND UTILITIES PRIOR TO COMMENCING CONSTRUCTION. NO REPRESENTATION IS MADE THAT ALL EXISTING UTILITIES ARE SHOWN HEREON. THE DESIGNER ASSUMES NO RESPONSIBILITY FOR UTILITIES SHOWN, OR NOT SHOWN IN THEIR PROPER LOCATION. 4.THE USE OF GARBAGE GRINDERS IS NOT RECOMMENDED. ELIMINATING THE USE OF GARBAGE DISPOSAL WILL IMPROVE WASTEWATER SYSTEM PERFORMANCE. THIS DESIGN IS BASED ON A SYSTEM WITHOUT A GARBAGE GRINDER. INSTALLATION OF A GARBAGE GRINDER WILL NECESSITATE INCREASING SEPTIC TANK SIZE AND MORE FREQUENT MONITORING OF THE SOLIDS LEVELS IN THE SEPTIC TANK. 5.CONTOURS, BUILDINGS, SOIL LOGS, AND OTHER SITE FEATURES ARE SHOWN FOR REFERENCE AND ARE NOT SURVEYED. ALL ELEVATIONS ARE BASED ON FIELD MEASUREMENTS AND CONDITIONS MAY CHANGE BASED ON CONSTRUCTION ACTIVITY. THIS PLAN DOES NOT REPRESENT AN ACTUAL FIELD SURVEY AND IS FOR SEPTIC DESIGN PURPOSES ONLY. 6.CALL 811 TWO WORKING DAYS BEFORE YOU DIG OR VISIT HTTP://WWW.CALLBEFOREYOUDIG.ORG/ GENERAL NOTES: PLAN NOTES: 1.A COUNTY PERMIT IS REQUIRED FOR THE CONSTRUCTION OF THIS DESIGN. THIS DESIGN MAY ONLY BE INSTALLED IF STAMPED APPROVED BY THE COUNTY AND MAY ONLY BE INSTALLED BY A COUNTY CERTIFIED INSTALLER. 2.ALL WORK SHALL CONFORM TO COUNTY STANDARDS AND GUIDELINES. STANDARDS AND GUIDELINES NOT SPECIFIED BY THE COUNTY SHALL CONFORM TO THE WASHINGTON ADMINISTRATIVE CODE (WAC) CONCERNING ON-SITE SEPTIC SYSTEMS (WAC 246-272A) AND THE LATEST EDITION OF THE WASHINGTON STATE DEPARTMENT OF HEALTH (WSDOH) RECOMMENDED STANDARDS AND GUIDELINES FOR PRESSURE DISTRIBUTION SYSTEMS AND SUBSURFACE DRIP SYSTEMS. 3.A COPY OF THE APPROVED PLAN SET SHALL BE KEPT AT THE JOB SITE AT ALL TIMES. 4.THE BEDS SHALL FOLLOW THE ORIGINAL GROUND SURFACE CONTOURS AND BE LEVEL. INSTALL THE BEDS AS SHOWN ON THE PLAN VIEW LAYOUT 5.STOCKPILE THE BACKFILL AND CONSTRUCTION MATERIALS ADJACENT TO THE PROPOSED DRAIN FIELD BUT NOT IN THE RESERVE DRAIN FIELD AREA. 6.AN INSPECTION OF THE SYSTEM BY THE DESIGNER IS REQUIRED PRIOR TO BACKFILLING OVER THE SEPTIC TANKS, TRANSPORT LINE TRENCHES AND THE DRAIN FIELD. 7.INSTALL CLEANOUTS EVERY 50' ALONG GRAVITY PIPE RUNS AND AT ANGLE POINTS. 8.ALL VALVES AND FILTERS SHALL BE READILY ACCESSIBLE FOR INSPECTION AND SERVICING. 9.CHANGES IN TANK CONFIGURATION OR LOCATION MUST BE APPROVED BY THE DESIGNER OR DESIGN MAY BE INVALID. 10.IF THE DRAIN FIELD SOIL IS DISTURBED PRIOR TO INSTALLATION, THE DESIGN MAY BE VOID. 11.ANY CUTS INTRODUCED WITHIN 50' OF THE DRAIN FIELD AREA MAY VOID THE DESIGN. 12.TREES AND/OR STUMPS GREATER THAN 18" IN DIAMETER, WHEN MEASURED 2 FEET ABOVE GRADE, MAY BE CUT AT GROUND LEVEL OR BURNED IN PLACE TO AVOID DISTURBING THE SOIL. IF TREES ARE TO BE REMOVED, LEAVE STUMPS AND ROOTS IN THE GROUND. MOW OTHER VEGETATION TO GROUND SURFACE. 13.MAINTAIN 10FT SETBACK FROM ALL WATER/IRRIGATION LINES AND ANY SEPTIC COMPONENTS. EXISTING IRRIGATION AND WATER LINES SHALL BE REMOVED OR RELOCATED AS NECESSARY. PERPENDICULAR CROSSINGS ARE ALLOWED. SEE SEWER/WATER CROSSING DETAIL FOR PROPER METHOD OF CROSSING. 14.FLOOR DRAINS SHALL NOT BE CONNECTED TO THE SEPTIC SYSTEM. DRAINS FROM ANY COMMERCIALLY MADE TUB, SHOWER, BASIN, SINK, OR TOILET ARE NOT CONSIDERED FLOOR DRAINS. 15.NO ROOF, FOOTING, OR SURFACE DRAINS SHALL BE CONNECTED TO THE SEPTIC SYSTEM. 16.FOOTING DRAINS WILL NOT BE ALLOWED WITHIN 30' DOWN SLOPE OF THE DRAIN FIELD. STORM WATER DISPERSION OR INFILTRATION TRENCHES ARE NOT ALLOWED WITHIN 100' UPHILL OF DRAIN FIELD OR 30' DOWN SLOPE OF THE DRAIN FIELD. DIRECT ALL STORM WATER RUNOFF (ROOF, FOOTING, ETC.) AWAY FROM THE DRAIN FIELD AND TANKS. 17.DETAILS SHOWN ARE SCHEMATIC. SEE PLAN VIEW FOR ACTUAL CONFIGURATION. MATERIALS: 1.ALL PLUMBING MUST BE OF PVC MATERIAL. 2.THE SIDE-SEWER CONNECTION PIPE AND ALL PIPING BETWEEN SEPTIC TANKS SHALL BE MIN. 4-INCH DIAMETER ASTM D3034 SDR-35 PVC. 3.CLASS 200 PVC SHALL MEET THE REQUIREMENTS OF ASTM D2241 SDR-21 PVC. 4.SCHEDULE 40 & SCHEDULE 80 PVC SHALL MEET THE REQUIREMENTS OF ASTM D1785. 5.TANKS SHALL BE CONCRETE AND BE INCLUDED ON THE WASHINGTON STATE HEALTH DEPARTMENT LIST OF REGISTERED SEWAGE TANKS (WAC 246-272C). SUBSTITUTION OF MATERIAL MAY BE ALLOWED WITH DESIGNER REVIEW AND APPROVAL. 6.ALL TANK INLET/OUTLET GASKETS SHALL CONSIST OF A RUBBERIZED MATERIAL THAT IS CAST INTO THE TANK WALL, MUST BE ABLE TO WITHSTAND VIBRATION AND/OR SETTLING, RESISTANT TO SEWER GASSES, AND CAPABLE OF ACCEPTING A NON-CORROSIVE CLAMP AND SCREW TO SECURE THE CONNECTING PIPE. 7.THE SEALANT BETWEEN TANK RIM AND LID, AND BETWEEN THE TANK LID AND RISER MUST BE ABLE TO PROVIDE A WATERTIGHT SEAL REGARDLESS OF WEATHER CONDITIONS OR TEMPERATURE DURING SEALANT APPLICATION. 8.TANK RISERS SHALL BE PVC, WATERTIGHT, AND HAVE A SOLID LOCKING LID. ELECTRICAL AND EFFLUENT PIPES THAT EXIT THE RISER MUST USE A RUBBERIZED GASKET WITH A WATERTIGHT SEAL THAT MUST BE ABLE TO WITHSTAND VIBRATION AND/OR SETTLING AND RESISTANT TO SEWER GASSES. 9.ALL VALVE BOXES SHALL BE NON-CONCRETE (POLYPROPELENE, HDPE, ETC) AND HAVE RISERS TO FINISHED GRADE. VALVE BOXES SHALL BE SET AND LEVELED ON A PEA GRAVEL BASE UNLESS OTHERWISE NOTED. 10.ALL MATERIALS AND MECHANICAL/ELECTRICAL COMPONENTS SHALL BE RATED FOR USE IN WASTEWATER APPLICATIONS. 11.SUBSTITUTION OF ANY PARTS LISTED MUST HAVE THE APPROVAL OF THE DESIGNER. 12.SEE INDIVIDUAL DETAILS FOR MATERIALS NOT LISTED HERE. 13.THE GEOTEXTILE (FILTER FABRIC) SHALL BE NON-WOVEN, FREE OF ANY CHEMICAL TREATMENT OR COATING WHICH REDUCES PERMEABILITY, INERT TO CHEMICALS COMMONLY FOUND IN SOIL, AND MEET OR EXCEED THE "MINIMUM AVERAGE ROLL VALUES" LISTED IN TABLE 3, "GEOTEXTILE SPECIFICATIONS" OF THE LATEST EDITION OF THE WSDOH RECOMMENDED STANDARDS AND GUIDELINES FOR DOSING GRAVITY SYSTEMS. 14.DRAIN ROCK SHALL BE WASHED GRAVEL OR CRUSHED ROCK RANGING IN SIZE FROM THREE-QUARTERS INCH TO TWO AND ONE-HALF INCHES, AND CONTAINING NO MORE THAN TWO PERCENT BY WEIGHT PASSING A US NO. 8 SIEVE AND NO MORE THAN ONE PERCENT BY WEIGHT PASSING A US NO. 200 SIEVE. 4004 NE 4TH ST., #107-508 RENTON, WA 98056 425.457.6029 425.432.4461 FAX WI L L I A M S R E S I D E N C E ON - S I T E S E W A G E D I S P O S A L D E S I G N 13 4 1 1 S E 1 5 1 S T S T R E E T R E N T O N KI N G C O U N T Y NTS SLOPE TO DRAIN DOSING CHAMBER PROFILE VIEW 1,500 GALLONS SINGLE COMPARTMENT SEPTIC TANK PROFILE VIEW 1,500 GALLONS DOUBLE COMPARTMENT 2/3 TOTAL VOLUME APPROXIMATE WATER TABLE ELEVATION ± 70' 4"∅ PVC @ 2.00% MIN. I.E.= ± 75.0' 24" LOCKING GAS TIGHT MANHOLE COVER. FASTEN WITH FOUR SCREWS PER LID. USE #3 SQUARE DRIVE OR LARGER. COVER MAY VARY 12"-36" SEPTIC TANK AND DOSING CHAMBER COVER MAY VARY 12"-36" 24" LOCKING GAS TIGHT MANHOLE COVER. FASTEN WITH FOUR SCREWS PER LID. USE #3 SQUARE DRIVE OR LARGER. PVC RISER TO BRING ELEVATION TO THE SURFACE. ALL JOINTS TO BE SEALED WITH MASTIC (TYP.)SLOPE TO DRAIN PVC RISER TO BRING ELEVATION TO THE SURFACE. ALL JOINTS TO BE SEALED WITH MASTIC (TYP.) BALL CHECK VALVE UNION DISCHARGE FLOAT TREE ON/OFF FLOAT HIGH LEVEL ALARM FLOAT REDUNDANT OFF FLOAT 4"∅ PVC @ 2.00% MIN. I.E.= ± 74.75' COMMERCIAL GRADE FILTER ACCESSIBLE THROUGH MANHOLE. I.E.= ± 74.50' CORROSION AND EXPLOSION PROOF NEMA 4X AND 7 NON-METALLIC JUNCTION BOX INLET TEE LIQUID LEVEL CONTROLS GASKETED CHAMBER LID WITH HOLD DOWN BOLTS OR SCREWS DISCHARGE GAS SEAL END OF CONDUIT TO CONTROL PANEL SEE DOSING CHAMBER SECTION VIEW PLAN VIEW 1/3 TOTAL VOLUME LIFT CHAIN SCHEMATIC NATIVE SOIL BACKFILL FREE OF ROCKS >3" (TYP.). SEE NOTES ABOVE FOR COMPACTION 4"-6" MIN. MEDIUM SAND (TYP.) SEE NOTES ABOVE FOR COMPACTION 6" MIN.18"18" 6" MIN. TANK NOTES: 1.CONTROL POINT: NW PROP CORNER ELEVATION= ± 78' 2.STUB OUT I.E.= ± 76' 3.DRAIN FIELD MANIFOLD INLET ELEVATION= ± 76' 4.PROVIDE AT LEAST ONE CLEAN OUT BETWEEN THE STUB OUT AND THE SEPTIC TANK INLET. 5.FOLLOW TANK MANUFACTURERS INSTALLATION INSTRUCTIONS. 6.TANK EXCAVATION SHALL BE LEVEL AND COMPACTED PRIOR TO PLACING BEDDING. 7.PROVIDE 4"-6" OF LEVEL MEDIUM SAND BEDDING BENEATH TANKS. COMPACT TO 95%. 8.PROVIDE NATIVE SOIL BACKFILL FREE OF ROCKS >3" AS BACKFILL AROUND TANKS. MAXIMUM 10" LIFTS AND COMPACT TO 95%. 9.LOWER 18" OF COVER OVER TOP OF TANKS SHALL BE NATIVE SOIL BACKFILL FREE OF ROCKS >3". MAXIMUM 10" LIFTS. COMPACT TO 95%. 10.ALL TANKS SHALL BE ADEQUATELY VENTED. VENTING MAY BE ACCOMPLISHED BY CONNECTION TO BUILDING SEWER VENTS OR BY A DIRECT TWO-INCH MINIMUM VERTICAL VENT TO THE ATMOSPHERE. 13.ALL JOINTS TO BE SEALED WATER TIGHT WITH MASTIC. 14.ALL TANKS SHALL BE TESTED & CONFIRMED WATERTIGHT. 4004 NE 4TH ST., #107-508 RENTON, WA 98056 425.457.6029 425.432.4461 FAX WI L L I A M S R E S I D E N C E ON - S I T E S E W A G E D I S P O S A L D E S I G N 13 4 1 1 S E 1 5 1 S T S T R E E T R E N T O N KI N G C O U N T Y 2" MIN. ABOVE PUMP SLOPE TO DRAIN 750 GALLONS (ONE DAY RESERVE) OUTLET PUMP OFF LEVEL 31.25 GALLON DOSE VOLUME PUMP ON LEVEL SURGE VOLUME 300 GALLONS ALARM LEVEL PUMP 5 MIN. FLOAT TREE REDUNDANT OFF FLOAT ON/OFF FLOAT HIGH LEVEL ALARM FLOAT INLET TEE ACCESSIBLE CONTROL PANEL WITH VISUAL/AUDIBLE ALARM ON SEPARATE CIRCUITS. PANEL TO BE INSTALLED IN DIRECT LINE OF SIGHT OF THE DOSING CHAMBER. 36" MAX. ORENCO PVC MANHOLE RISERS OR EQUIVALENT 24"∅ RISERS 3" BRICKS GAS SEALED CONTROL CIRCUIT CONDUIT TO CONTROL PANEL. INTRINSICALLY SAFE WIRING ONLY. NTSSCHEMATIC DOSING CHAMBER 2' M I N . DOSING CHAMBER SECTION VIEW DOSING CHAMBER NOTES: 1.ALL INTERNAL TANK PIPING SHALL BE SCHEDULE 40 PVC OR BETTER. FITTINGS SHALL BE SCHEDULE 80 OR BETTER. 2.CONTROL-ALARM PANEL SHALL BE OUTDOOR APPROVED OR WEATHER PROTECTED, READILY ACCESSIBLE, TAMPER RESISTANT, AND IN DIRECT LINE OF SIGHT OF THE DOSING CHAMBER. 3.ALL ELECTRICAL WORK TO THE CONTROL PANEL MUST BE COMPLETED PRIOR TO FINAL INSPECTION. THE SYSTEM SHALL BE TESTED USING PERMANENT POWER. 4.USE GEOFLOW 1-ZONE SIMPLEX AUTOMATIC CONTROL PANEL WITH TIMER AND AUTOMATIC FLUSHING WITH SJE RHOMBUS SENSOR FLOAT MERCURY FLOATS OR EQUAL. 5.PANEL SHALL HAVE AN EVENT COUNTER, HOUR RUN METER, AND VISUAL/AUDIBLE ALARM. THE ALARM CIRCUIT SHALL BE INDEPENDENT OF THE PUMP CIRCUIT. 6.MOUNT THE CONTROL PANEL ON A NON-BEDROOM EXTERIOR WALL OR ON ITS OWN PEDESTAL APPROXIMATELY FIVE FEET HIGH ABOVE FINAL GRADE. 7.A TIMER SHALL BE USED IN CONJUNCTION WITH THE ON/OFF FLOAT TO TURN THE PUMP ON EVERY 1 HOUR FOR 0.4 MINUTES. ACTUAL RUN TIME SHALL BE SET BY TESTING AS PER NOTE 8. 8.AT THE PRESSURE TEST THE INSTALLER SHALL VERIFY THE PUMP RUN TIME. THE PUMP RUN TIME SHALL PROVIDE A DOSE OF 31.25 GALLONS. THE TIMER SHALL THEN BE SET FOR THIS PUMP RUN TIME. 9.THE FOLLOWING CONDITIONS SHALL BE MET IN ORDER FOR THE PUMP TO TURN ON: A. THE ON/OFF FLOAT IS IN THE ON POSITION. B. THE TIMER IS IN THE ON CYCLE. 10.PUMP IS AN GOULDS MODEL WE20H OR EQUIVALENT SUBMERSIBLE EFFLUENT PUMP THAT PROVIDES 75 GPM AT 55 FEET OF HEAD. 11.THIS DESIGN INCLUDES 10 FEET OF ELEVATION HEAD FROM THE PUMP TO THE DRAIN FIELD AND 30 LINEAL FEET OF TRANSPORT PIPE. EXCEEDING THESE NUMBERS WILL REQUIRE RESIZING THE PUMP. 12.THE PUMP IS INSIDE AN ORENCO BIOTUBE PUMP VAULT OR EQUIVALENT. 13.FLOATS/ PUMP CONTROL SWITCHES SHALL BE MOUNTED INDEPENDENT OF THE PUMP AND TRANSPORT LINE. 14.ALL PUMP CONTROL STRAPS SHALL BE MADE OF POLYPROPYLENE OR OTHER MATERIAL APPROVED FOR USE IN SEPTIC SYSTEMS. 15.THE SYSTEM SHALL BE EQUIPPED WITH AN AIR VACUUM RELEASE VALVE OR OTHER SUITABLE DEVICE TO AVOID SIPHONING. 4004 NE 4TH ST., #107-508 RENTON, WA 98056 425.457.6029 425.432.4461 FAX WI L L I A M S R E S I D E N C E ON - S I T E S E W A G E D I S P O S A L D E S I G N 13 4 1 1 S E 1 5 1 S T S T R E E T R E N T O N KI N G C O U N T Y 24" SAND SHOULDER 6" SAND SHOULDER 2.0 3' TYPICAL 10' 2.0 37.5' 3 LATERALS TOTAL 3"∅ CLASS 200 PVC TRANSPORT PIPE FROM DOSING CHAMBER 1-1/4"∅ PERFORATED CLASS 200 PVC LATERAL DRILL 3/16"∅ HOLES UPWARD AT END CAP OF EACH LATERAL NTS MANIFOLD/LATERAL LAYOUT SCHEMATIC 3/16"∅ HOLE S P L A C E D O N T O P O F LATER A L 2 1 " O N C E N T E R 3 ' M I N . 9" 24" VOID SPACE INSTALL CLEANOUTS ON ALL LATERALS NTS SAND BED 3 LATERALS TOTAL NTS SAND BED CROSS SECTION WITH INFILTRATORS 1.MINIMUM DEPTH OF SAND UNDER BED SHALL BE TWO FEET. 2.SAND BED AND PRESSURE LATERALS SHALL BE LEVEL AND FOLLOW ORIGINAL GROUND CONTOURS. 3.PROVIDE ADEQUATE DRAINAGE AROUND SAND BED. 4.EXCAVATED LOAMY SAND MATERIAL FROM SAND BED AREA MAY BE STOCKPILED FOR SUBSOIL CAP. 5.SAND BED SHALL BE INSTALLED PER THE LATEST EDITION OF THE WASHINGTON STATE DEPARTMENT OF HEALTH SAND LINED TRENCH SYSTEM GUIDELINES. 6.OPERATION AND MAINTENANCE MONITORING SHALL BE IN ACCORDANCE WITH THE LATEST EDITION OF THE WASHINGTON STATE DEPARTMENT OF HEALTH SAND LINED TRENCH SYSTEM GUIDELINES. SAND BED NOTES 3"∅ TRANSPORT PIPE CLEANOUT TYP. MONITORING PORT COVER AS MANUFACTURED BY CARSON INDUSTRIES MODEL 910-12B OR EQUAL INSTALL TWO 4"∅ PVC AERATION PORTS 4"∅ PVC MONITORING PORTS WITH SOLID CAPS, BOTTOM 9" PERFORATED WITH 1/2" HOLES 3' O.C. (TYP.) FILTER FABRIC FINISHED GRADE ORIGINAL GRADE SLOPE TO DRAIN 3/8" - 1 1/2" CLEAN WASHED COARSE AGGREGATE NO FINES OR SILT ALLOWED CLEAN SANDY LOAM FILL COARSE SAND 3" OF PEA GRAVEL 1-1/4" LATERAL VOID SPACE VOID SPACE MANIFOLD 36" MIN 51" MAX INFILTRATOR QUICK4 STANDARD CHAMBER 21" 21" 75' 4004 NE 4TH ST., #107-508 RENTON, WA 98056 425.457.6029 425.432.4461 FAX WI L L I A M S R E S I D E N C E ON - S I T E S E W A G E D I S P O S A L D E S I G N 13 4 1 1 S E 1 5 1 S T S T R E E T R E N T O N KI N G C O U N T Y Appendix C:WWHM Water Quality Flow Rate for Contech Stormfilter Sizing and Contech Specifications WWHM2012 PROJECT REPORT default[88]12/19/2024 5:52:56 AM Page 2 General Model Information Project Name:default[88] Site Name: Site Address: City: Report Date:12/19/2024 Gage:Seatac Data Start:1948/10/01 Data End:2009/09/30 Timestep:15 Minute Precip Scale:1.000 Version Date:2018/10/10 Version:4.2.16 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year default[88]12/19/2024 5:52:56 AM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre A B, Forest, Mod 0.86 Pervious Total 0.86 Impervious Land Use acre Impervious Total 0 Basin Total 0.86 Element Flows To: Surface Interflow Groundwater default[88]12/19/2024 5:52:56 AM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre A B, Lawn, Mod 0.7957 Pervious Total 0.7957 Impervious Land Use acre ROOF TOPS FLAT 0.0295 DRIVEWAYS MOD 0.0348 Impervious Total 0.0643 Basin Total 0.86 Element Flows To: Surface Interflow Groundwater default[88]12/19/2024 5:52:57 AM Page 5 Routing Elements Predeveloped Routing default[88]12/19/2024 5:52:57 AM Page 6 Mitigated Routing default[88]12/19/2024 5:52:57 AM Page 7 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.86 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.7957 Total Impervious Area:0.0643 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.000746 5 year 0.001231 10 year 0.001662 25 year 0.00236 50 year 0.00301 100 year 0.003791 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.035304 5 year 0.061614 10 year 0.086029 25 year 0.127009 50 year 0.166472 100 year 0.215106 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.001 0.039 1950 0.002 0.117 1951 0.002 0.053 1952 0.001 0.018 1953 0.001 0.021 1954 0.001 0.042 1955 0.001 0.029 1956 0.001 0.061 1957 0.001 0.026 1958 0.001 0.022 default[88]12/19/2024 5:54:52 AM Page 8 1959 0.001 0.023 1960 0.001 0.047 1961 0.001 0.037 1962 0.001 0.020 1963 0.001 0.030 1964 0.001 0.043 1965 0.001 0.039 1966 0.001 0.020 1967 0.001 0.104 1968 0.001 0.040 1969 0.001 0.025 1970 0.001 0.025 1971 0.001 0.030 1972 0.005 0.090 1973 0.001 0.019 1974 0.001 0.029 1975 0.001 0.031 1976 0.001 0.038 1977 0.001 0.022 1978 0.001 0.031 1979 0.001 0.039 1980 0.001 0.039 1981 0.001 0.027 1982 0.001 0.038 1983 0.001 0.031 1984 0.001 0.023 1985 0.001 0.026 1986 0.001 0.027 1987 0.001 0.041 1988 0.001 0.022 1989 0.001 0.033 1990 0.001 0.229 1991 0.002 0.095 1992 0.001 0.020 1993 0.001 0.021 1994 0.001 0.020 1995 0.001 0.030 1996 0.007 0.118 1997 0.001 0.051 1998 0.001 0.025 1999 0.002 0.146 2000 0.001 0.027 2001 0.001 0.030 2002 0.001 0.032 2003 0.001 0.036 2004 0.001 0.051 2005 0.001 0.022 2006 0.001 0.042 2007 0.010 0.261 2008 0.001 0.121 2009 0.001 0.052 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.0100 0.2609 2 0.0067 0.2292 3 0.0050 0.1459 default[88]12/19/2024 5:54:52 AM Page 9 4 0.0018 0.1206 5 0.0018 0.1179 6 0.0016 0.1169 7 0.0016 0.1041 8 0.0008 0.0946 9 0.0007 0.0896 10 0.0007 0.0609 11 0.0007 0.0526 12 0.0007 0.0525 13 0.0007 0.0512 14 0.0007 0.0510 15 0.0007 0.0474 16 0.0007 0.0432 17 0.0007 0.0422 18 0.0007 0.0419 19 0.0007 0.0405 20 0.0007 0.0395 21 0.0007 0.0395 22 0.0007 0.0395 23 0.0007 0.0389 24 0.0007 0.0386 25 0.0007 0.0383 26 0.0007 0.0376 27 0.0007 0.0371 28 0.0007 0.0361 29 0.0007 0.0328 30 0.0007 0.0322 31 0.0007 0.0314 32 0.0007 0.0311 33 0.0007 0.0307 34 0.0007 0.0301 35 0.0007 0.0298 36 0.0007 0.0297 37 0.0007 0.0296 38 0.0007 0.0295 39 0.0007 0.0289 40 0.0007 0.0270 41 0.0007 0.0268 42 0.0007 0.0266 43 0.0007 0.0264 44 0.0007 0.0258 45 0.0007 0.0254 46 0.0007 0.0250 47 0.0007 0.0248 48 0.0007 0.0235 49 0.0007 0.0226 50 0.0007 0.0224 51 0.0007 0.0224 52 0.0007 0.0219 53 0.0007 0.0218 54 0.0007 0.0215 55 0.0006 0.0208 56 0.0006 0.0202 57 0.0006 0.0202 58 0.0006 0.0197 59 0.0006 0.0196 60 0.0005 0.0190 61 0.0005 0.0182 default[88]12/19/2024 5:54:52 AM Page 10 default[88]12/19/2024 5:54:52 AM Page 11 Duration Flows Flow(cfs)Predev Mit Percentage Pass/Fail 0.0004 2915 202766 6955 Fail 0.0004 2492 197761 7935 Fail 0.0004 2124 192991 9086 Fail 0.0005 1805 188649 10451 Fail 0.0005 1511 184414 12204 Fail 0.0005 1295 180393 13929 Fail 0.0005 1088 176714 16242 Fail 0.0006 851 173121 20343 Fail 0.0006 625 169506 27120 Fail 0.0006 478 166319 34794 Fail 0.0006 330 163111 49427 Fail 0.0007 188 160074 85145 Fail 0.0007 43 157293 365797 Fail 0.0007 35 154427 441220 Fail 0.0007 33 151818 460054 Fail 0.0008 31 149187 481248 Fail 0.0008 30 146642 488806 Fail 0.0008 29 144246 497400 Fail 0.0009 29 141851 489141 Fail 0.0009 29 139541 481175 Fail 0.0009 28 137316 490414 Fail 0.0009 28 135092 482471 Fail 0.0010 27 132953 492418 Fail 0.0010 27 131006 485207 Fail 0.0010 27 129060 478000 Fail 0.0010 27 127135 470870 Fail 0.0011 26 125210 481576 Fail 0.0011 25 123349 493396 Fail 0.0011 25 121595 486379 Fail 0.0011 24 119799 499162 Fail 0.0012 23 118023 513143 Fail 0.0012 23 116398 506078 Fail 0.0012 23 114730 498826 Fail 0.0013 22 113147 514304 Fail 0.0013 22 111650 507500 Fail 0.0013 21 110110 524333 Fail 0.0013 21 108655 517404 Fail 0.0014 21 107136 510171 Fail 0.0014 21 105682 503247 Fail 0.0014 21 104313 496728 Fail 0.0014 20 102880 514400 Fail 0.0015 19 101511 534268 Fail 0.0015 19 100185 527289 Fail 0.0015 18 98880 549333 Fail 0.0015 18 97554 541966 Fail 0.0016 16 96335 602093 Fail 0.0016 16 95073 594206 Fail 0.0016 16 93940 587125 Fail 0.0017 16 92763 579768 Fail 0.0017 15 91608 610720 Fail 0.0017 15 90475 603166 Fail 0.0017 15 89320 595466 Fail 0.0018 15 88186 587906 Fail 0.0018 15 87117 580780 Fail default[88]12/19/2024 5:54:52 AM Page 12 0.0018 14 85962 614014 Fail 0.0018 13 84849 652684 Fail 0.0019 13 83823 644792 Fail 0.0019 13 82689 636069 Fail 0.0019 13 81705 628500 Fail 0.0019 13 80721 620930 Fail 0.0020 13 79737 613361 Fail 0.0020 12 78839 656991 Fail 0.0020 11 77855 707772 Fail 0.0021 11 76893 699027 Fail 0.0021 11 76016 691054 Fail 0.0021 11 75075 682500 Fail 0.0021 11 74176 674327 Fail 0.0022 10 73299 732990 Fail 0.0022 10 72337 723370 Fail 0.0022 10 71503 715030 Fail 0.0022 9 70690 785444 Fail 0.0023 9 69770 775222 Fail 0.0023 9 68957 766188 Fail 0.0023 9 68102 756688 Fail 0.0023 9 67289 747655 Fail 0.0024 8 66498 831225 Fail 0.0024 8 65706 821325 Fail 0.0024 8 64958 811975 Fail 0.0025 8 64209 802612 Fail 0.0025 8 63439 792987 Fail 0.0025 8 62733 784162 Fail 0.0025 8 61963 774537 Fail 0.0026 8 61215 765187 Fail 0.0026 8 60509 756362 Fail 0.0026 8 59782 747275 Fail 0.0026 8 59054 738175 Fail 0.0027 8 58434 730425 Fail 0.0027 8 57686 721075 Fail 0.0027 8 57023 712787 Fail 0.0027 8 56402 705025 Fail 0.0028 8 55718 696475 Fail 0.0028 8 55076 688450 Fail 0.0028 8 54456 680700 Fail 0.0029 8 53793 672412 Fail 0.0029 8 53194 664925 Fail 0.0029 8 52531 656637 Fail 0.0029 8 51911 648887 Fail 0.0030 8 51333 641662 Fail 0.0030 8 50713 633912 Fail 0.0030 8 50135 626687 Fail The development has an increase in flow durations from 1/2 Predeveloped 2 year flow to the 2 year flow or more than a 10% increase from the 2 year to the 50 year flow. The development has an increase in flow durations for more than 50% of the flows for the range of the duration analysis. default[88]12/19/2024 5:54:52 AM Page 13 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0 acre-feet On-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. Off-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. default[88]12/19/2024 5:54:52 AM Page 14 LID Report default[88]12/19/2024 5:56:20 AM Page 15 Model Default Modifications Total of 0 changes have been made. PERLND Changes No PERLND changes have been made. IMPLND Changes No IMPLND changes have been made. default[88]12/19/2024 5:56:20 AM Page 16 Appendix Predeveloped Schematic default[88]12/19/2024 5:56:21 AM Page 17 Mitigated Schematic default[88]12/19/2024 5:56:23 AM Page 18 Predeveloped UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 default[88].wdm MESSU 25 Predefault[88].MES 27 Predefault[88].L61 28 Predefault[88].L62 30 POCdefault[88]1.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 2 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Basin 1 MAX 1 2 30 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 2 A/B, Forest, Mod 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 2 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 2 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO default[88]12/19/2024 5:56:23 AM Page 19 PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 2 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 2 0 5 2 400 0.1 0.3 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 2 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 2 0.2 0.5 0.35 0 0.7 0.7 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 2 0 0 0 0 3 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS END IWAT-STATE1 default[88]12/19/2024 5:56:23 AM Page 20 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Basin 1*** PERLND 2 0.86 COPY 501 12 PERLND 2 0.86 COPY 501 13 ******Routing****** END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* END PRINT-INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> END HYDR-INIT END RCHRES SPEC-ACTIONS END SPEC-ACTIONS FTABLES END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC default[88]12/19/2024 5:56:23 AM Page 21 WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** COPY 501 OUTPUT MEAN 1 1 48.4 WDM 501 FLOW ENGL REPL END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 12 PERLND PWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 12 MASS-LINK 13 PERLND PWATER IFWO 0.083333 COPY INPUT MEAN END MASS-LINK 13 END MASS-LINK END RUN default[88]12/19/2024 5:56:23 AM Page 22 Mitigated UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 default[88].wdm MESSU 25 Mitdefault[88].MES 27 Mitdefault[88].L61 28 Mitdefault[88].L62 30 POCdefault[88]1.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 8 IMPLND 4 IMPLND 6 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Basin 1 MAX 1 2 30 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 8 A/B, Lawn, Mod 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 8 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 8 0 0 4 0 0 0 0 0 0 0 0 0 1 9 default[88]12/19/2024 5:56:23 AM Page 23 END PRINT-INFO PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 8 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 8 0 5 0.8 400 0.1 0.3 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 8 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 8 0.1 0.5 0.25 0 0.7 0.25 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 8 0 0 0 0 3 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 4 ROOF TOPS/FLAT 1 1 1 27 0 6 DRIVEWAYS/MOD 1 1 1 27 0 END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 4 0 0 1 0 0 0 6 0 0 1 0 0 0 END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* 4 0 0 4 0 0 0 1 9 6 0 0 4 0 0 0 1 9 END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** 4 0 0 0 0 0 6 0 0 0 0 0 END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC 4 400 0.01 0.1 0.1 6 400 0.05 0.1 0.08 default[88]12/19/2024 5:56:23 AM Page 24 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN 4 0 0 6 0 0 END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS 4 0 0 6 0 0 END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Basin 1*** PERLND 8 0.7957 COPY 501 12 PERLND 8 0.7957 COPY 501 13 IMPLND 4 0.0295 COPY 501 15 IMPLND 6 0.0348 COPY 501 15 ******Routing****** END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* END PRINT-INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** END HYDR-PARM2 default[88]12/19/2024 5:56:23 AM Page 25 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> END HYDR-INIT END RCHRES SPEC-ACTIONS END SPEC-ACTIONS FTABLES END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** COPY 1 OUTPUT MEAN 1 1 48.4 WDM 701 FLOW ENGL REPL COPY 501 OUTPUT MEAN 1 1 48.4 WDM 801 FLOW ENGL REPL END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 12 PERLND PWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 12 MASS-LINK 13 PERLND PWATER IFWO 0.083333 COPY INPUT MEAN END MASS-LINK 13 MASS-LINK 15 IMPLND IWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 15 END MASS-LINK END RUN default[88]12/19/2024 5:56:23 AM Page 26 Predeveloped HSPF Message File default[88]12/19/2024 5:56:23 AM Page 27 Mitigated HSPF Message File default[88]12/19/2024 5:56:23 AM Page 28 Disclaimer Legal Notice This program and accompanying documentation is provided 'as-is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by the user. Clear Creek Solutions, Inc. disclaims all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions, Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions, Inc. has been advised of the possibility of such damages. Clear Creek Solutions, Inc. 6200 Capitol Blvd. Ste F Olympia, WA. 98501 Toll Free 1(866)943-0304 Local (360)943-0304 www.clearcreeksolutions.com 28" x 28" [711 x 711] VANED INLET GRATE (SOLID OPTIONAL WITH INLET PIPE) PLAN VIEW PLAN VIEW CASTINGS NOT SHOWN FLOW 28" x 28" [711 x 711] ACCESS COVER RIGHT SIDE VIEWELEVATION VIEW 2' - 4 " [ 7 1 1 ] IN S I D E R I M 2'-4" [711] INSIDE RIM 2'-4" [711] INSIDE RIM 2' - 8 " [ 8 1 3 ] 5'-1" [1549] OUTLET PIPE WITH BOOT (12" [300]Ø MAXIMUM) OPTIONAL INLET PIPES AND ALTERNATE OUTLET PIPE LOCATIONS 2' - 0 " [ 6 1 0 ] 4'-5" [1346] BYPASS WEIR ASSEMBLY STORMFILTER CARTRIDGE (OPTIONAL) ALTERNATE OUTLET PIPE LOCATIONS OUTLET PIPE WITH BOOT 2'-0" [610] 2'-8" [813] 2.35' [718] MIN. (18" [457]) 3.1' [946] MIN. (27" [686]) SEE LINKING OPTIONS ABOVE FOR MAXIMUM RIM TO INVERT BYPASS WEIR ASSEMBLYSTORMFILTER CARTRIDGE CARTRIDGE DECK BYPASS WEIR ASSEMBLY FINISHED GRADE STORMFILTER CARTRIDGE (STANDARD) OPTIONAL INLET PIPE INVERT 6" [152] MIN. ABOVE OUTLET PIPE INVERT SINGLE UNITDUAL UNIT (SHIPPED IN 1 PIECE) GRATESOLID GRATE SOLIDGRATESOLID FLOW TRIPLE UNIT (SHIPPED IN 2 PIECES) GRATESOLIDSOLID FLOWFLOWGRATESOLIDSOLID QUAD UNIT (SHIPPED IN 2 PIECES) GRATESOLIDSOLID FLOWSOLIDGRATEGRATEGRATESOLID CONCRETE CATCHBASIN STORMFILTER STANDARD DETAIL I: \ C O M M O N \ C A D \ T R E A T M E N T \ 1 0 S T O R M F I L T E R \ 4 0 S T A N D A R D D R A W I N G S \ S F C B \ S F C B - C \ D W G \ W E S T D W G - C O N T E C H F O R M A T C A S C A D E P R E C A S T \ S F C B - C - D T L . D W G 12 / 1 6 / 2 0 2 2 7 : 3 1 A M www.ContechES.com 11 8 1 5 N E G l e nn W i di n g D r i v e , P or t l a n d , O R 9 72 2 0 800-548-4667 503-240-3393 800-561-1271 FAX STORMFILTER DESIGN NOTES · CONCRETE CATCHBASIN STORMFILTER TREATMENT CAPACITY VARIES BY CARTRIDGE COUNT AND LOCAL APPROVALS · PEAK CONVEYANCE CAPACITY IS 1.3 CFS · CONCRETE CATCHBASIN STORMFILTER IS AVAILABLE WITH UP TO TWO (2), 18" [457] OR 27" [686] TALL CARTRIDGES · UP TO 4 INDIVIDUAL UNITS MAY BE LINKED FOR AN ULTIMATE CAPACITY OF EIGHT (8) CARTRIDGES CARTRIDGE SIZE (in. [mm])27 [686]18 [457] RECOMMENDED HYDRAULIC DROP (ft. [mm])3.05 [930]2.3 [701] SPECIFIC FLOW RATE (gpm/sf [L/s/m2])2 [1.36]1.67* [1.13]*1 [0.68]2 [1.36]1.67* [1.13]*1 [0.68] CARTRIDGE FLOW RATE (gpm [L/s])22.5 [1.4]18.79 [1.19]11.25 [0.71]15 [0.95]12.53 [0.79]7.5 [0.47] * 1.67 gpm/sf [1.13 L/s/m2] SPECIFIC FLOW RATE IS APPROVED WITH PHOSPHOSORB® (PSORB) MEDIA ONLY SITE SPECIFIC DATA REQUIREMENTS STRUCTURE ID WATER QUALITY FLOW RATE (cfs [L/s]) PEAK FLOW RATE (cfs [L/s]) RETURN PERIOD OF PEAK FLOW (yrs) CARTRIDGE SIZE (27, 18) CARTRIDGE FLOW RATE MEDIA TYPE (PERLITE, ZPG, PSORB) NUMBER OF CARTRIDGES REQUIRED RIM ELEVATION PIPE DATA:INVERT MATERIAL DIAMETER INLET PIPE 1 INLET PIPE 2 OUTLET PIPE NOTES/SPECIAL REQUIREMENTS: GENERAL NOTES 1.CONTECH TO PROVIDE ALL MATERIALS UNLESS NOTED OTHERWISE. 2.DIMENSIONS MARKED WITH ( ) ARE REFERENCE DIMENSIONS. ACTUAL DIMENSIONS MAY VARY. 3.ALTERNATE DIMENSIONS ARE MILLIMETERS [mm] UNLESS NOTED OTHERWISE. 4.FOR FABRICATION DRAWINGS WITH DETAILED STRUCTURE DIMENSIONS AND WEIGHTS, PLEASE CONTACT YOUR CONTECH ENGINEERED SOLUTIONS LLC REPRESENTATIVE. www.ContechES.com 5.STORMFILTER WATER QUALITY STRUCTURE SHALL BE IN ACCORDANCE WITH ALL DESIGN DATA AND INFORMATION CONTAINED IN THIS DRAWING. CONTRACTOR TO CONFIRM STRUCTURE MEETS REQUIREMENTS OF PROJECT. 6.FILTER CARTRIDGES SHALL BE MEDIA-FILLED, PASSIVE, SIPHON ACTUATED, RADIAL FLOW, AND SELF CLEANING. RADIAL MEDIA DEPTH SHALL BE 7-INCHES [178]. FILTER MEDIA CONTACT TIME SHALL BE AT LEAST 38 SECONDS. 7.SPECIFIC FLOW RATE IS THE MEASURE OF THE FLOW (GPM [L/S]) DIVIDED BY THE MEDIA SURFACE CONTACT AREA (SF [m2]). 8.STRUCTURE SHALL MEET AASHTO HS20 LOAD RATING, ASSUMING EARTH COVER OF 0' - 0'-2" [51] AND GROUNDWATER ELEVATION AT, OR BELOW, THE OUTLET PIPE INVERT ELEVATION. ENGINEER OF RECORD TO CONFIRM ACTUAL GROUNDWATER ELEVATION. CASTINGS SHALL MEET AASHTO M306 AND BE CAST WITH THE CONTECH LOGO. INSTALLATION NOTES 1.ANY SUB-BASE, BACKFILL DEPTH, AND/OR ANTI-FLOTATION PROVISIONS ARE SITE-SPECIFIC DESIGN CONSIDERATIONS AND SHALL BE SPECIFIED BY ENGINEER OF RECORD. 2.CONTRACTOR TO PROVIDE EQUIPMENT WITH SUFFICIENT LIFTING AND REACH CAPACITY TO LIFT AND SET THE STORMFILTER STRUCTURE. 3.CONTRACTOR TO PROVIDE AND INSTALL PIPES. MATCH PIPE INVERTS SHOWN ON PROJECT SPECIFIC DRAWINGS. 4.CONTRACTOR TO TAKE APPROPRIATE MEASURES TO PROTECT CARTRIDGES FROM CONSTRUCTION-RELATED EROSION RUNOFF. LINKING OPTIONS SHOWN BELOW. FLEXIBLE INLET PIPE, GRATED AND SOLID COVER PLACEMENT. CONTACT YOUR CONTECH REPRESENTATIVE FOR MORE INFORMATION THIS PRODUCT MAY BE PROTECTED BY ONE OR MORE OF THE FOLLOWING U.S. PATENTS: 5,322,629; 5,524,576; 5,707,527; 5,985,157; 6,027,639; 6,649,048; RELATED FOREIGN PATENTS, OR OTHER PATENTS PENDING. MAXIMUM RIM TO OUTLET PIPE INVERT HEIGHT IS 6.05' [1844]. REV 5/16 SECTION (_____) STORMFILTER® MEDIA CARTRIDGE FILTRATION SYSTEM STORMWATER QUALITY – MEDIA CARTRIDGE FILTRATION SYSTEM STANDARD SPECIFICATION 1.GENERAL 1.1.The Contractor shall furnish and install the StormFilter, complete and operable as shown and as specified herein, in accordance with the requirements of the plans and contract documents. The water quality treatment flow shall be as determined and approved by the Engineer of Record. 1.2.The StormFilter shall consist of an aboveground or underground precast concrete, steel or plastic structure that houses passive, radial flow, siphon-actuated, and rechargeable media filled filtration cartridge(s). The rechargeable media-filled filter cartridges shall incorporate a protective hood over the media cartridge and a siphon-actuated surface self-cleaning mechanism to increase the effective life of the filter media and to reduce the accumulation of material on the cartridge/media interface. Each radial-flow filter cartridge shall operate at a predetermined flow rate through the use of an integrated flow control orifice located within each filter cartridge outlet manifold. The media-filled cartridges shall trap particulates (TSS) and have the capability to adsorb pollutants such as dissolved metals, nutrients and hydrocarbons. The media cartridge filtration system shall consist of no less than 0.12 cubic feet of filter media for each 1-gallon per minute of water quality treatment flow. 1.3.The StormFilter shall be of a type that has been installed and in use for a minimum of five (5) consecutive years preceding the date of installation of the system. The manufacturer shall have been, during the same consecutive five (5) year period, engaged in the engineering design and production of systems deployed for the treatment of storm water runoff and which have a history of successful production, acceptable to the Engineer of Record and/or the approving Jurisdiction. The manufacturer of the StormFilter shall be, without exception: Contech Engineered Solutions 9100 Centre Pointe Drive West Chester, OH, 45069 Tel: 1 800 338 1122 1.4. Submittals: 1.4.1.Manufacturer or supplier shall submit to the Contractor shop drawings for the StormFilter structure, filter cartridges and accessory equipment. Drawings shall include principal dimensions, filter placement, location of piping and unit foundation. 1.4.2.Manufacturer or supplier shall submit Installation Instructions to the Contractor. 1.4.3.Manufacturer or supplier shall submit an Operation and Maintenance Manual to the Contractor. 1.5.Substitution: Any proposed equal alternative product substitution to this specification must be submitted for review and approved by the Engineer of Record 10 days prior to bid opening. Review package should include third party reviewed performance data for both flow rate and pollutant removal. Pollutant data should follow TAPE protocols. The system must have a GULD approval for Basic treatment through the department of Ecology. 1.6.American Society for Testing and Materials (ASTM) Reference Specifications: REV 5/16 1.6.1.ASTM C857: Standard Practice for Minimum Structural Design Loading for Underground Precast Concrete Utility Structures 1.6.2.ASTM C858: Standard Specification of Underground Precast Concrete Utility Structures 1.6.3.ASTM C478: Standard Specification for Circular Precast Reinforced Concrete Manhole Sections 1.6.4.ASTM C497: Standard Test Methods for Concrete Pipe, Manhole Sections or Tile 1.6.5.ASTM C109: Standard Test Method for Compressive Strength of Hydraulic Cement Mortars 1.6.6.ASTM A615/A615M: Standard Specification for Deformed and Plain Carbon-Steel Bars for Concrete Reinforcement 1.6.7.ASTM D698: Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Standard Effort 1.6.8.ASTM F628: Standard Specification for ABS Schedule 40 Plastic Drain, Waste and Vent Pipe with a Cellular Core 1.6.9.ASTM D1785: Standard Specification for PVC Plastic Pipe, Schedules 40, 80 & 120 1.6.10.ASTM D2466: Standard Specification for PVC Plastic Pipe Fittings, Schedule 40 1.6.11.ASTM A36: Standard Specification for Carbon Structural Steel 1.6.12.ASTM A48: Standard Specification for Gray Iron Castings 1.6.13.ASTM D4101: Standard Specification for Polypropylene Injection and Extrusion Materials 1.7.American Association of State Highway and Transportation Officials (AASHTO) Reference Specifications: 1.7.1.AASHTO M199: Standard Specification for Precast Reinforced Concrete Manhole Sections 2.MATERIALS 2.1.Internal Components: 2.1.1.All internal components including ABS and PVC manifold piping, filter cartridge(s), filter media (as specified on the plans in the StormFilter data block or by the Engineer of Record) shall be provided by Contech Engineered Solutions LLC. This includes sump covers, flow spreaders, energy dissipaters and outlet risers with scum baffles where appropriate. 2.1.2.ABS manifold pipe shall meet ASTM F628. PVC manifold pipe shall meet ASTM D1785 and PVC fittings shall meet ASTM D2466. 2.1.3.Filter cartridge bottom pan, inner ring, and hood shall be constructed from linear low-density polyethylene (LLDPE) or ABS. Filter cartridge screen shall consist of 1” x ½” welded wire fabric REV 5/16 (16 gauge minimum) with a bonded PVC coating. Internal parts shall consist of ABS or PVC material. Siphon-priming float shall be constructed from high-density polyethylene (HDPE). All miscellaneous nuts, bolts, screws, and other fasteners shall be stainless steel or aluminum. 2.1.4.An orifice plate shall be supplied with each cartridge to restrict flow rate to a maximum of 22.5 gpm at system design head or as specified on drawings. 2.1.5.If a sump cover/overflow, baffle/inlet, sump/outlet, sump/inlet, tower/outlet overflow is provided, they shall be constructed of ABS and sealed to the interior vault walls and floor with a polyurethane construction sealant rated for use below the waterline, SikaFlex 1a or equal. Contractor to provide sealant material and installation unless completed prior to shipment. 2.1.6.Where an Underdrain Design is provided, the size of the underdrain will provide a minimum of 0.067 in2 of underdrain cross sectional area per 1 gpm of design flow rate. (example: 105 gpm maximum design flow rate will require an underdrain with 7.035 in2 of cross sectional area, which is equal to one 3” diameter pipe). 2.1.7.Filter media shall be provided by Contech or an approved alternate source. Filter media shall consist of one or more of the following, as specified in the StormFilter data block, or by the Engineer: 2.1.7.1.Perlite Media: Perlite media shall be made of natural siliceous volcanic rock free of any debris or foreign matter. The perlite media shall have a bulk density ranging from 6.5 to 8.5 lb/ft3 and particle sizes ranging from that passing through a 0.50 inch screen and retained on a U.S. Standard #8 sieve. 2.1.7.2.CSF Media: CSF media shall be made exclusively of composted fallen deciduous leaves. Filter media shall be granular. Media shall be dry at the time of installation. The CSF leaf media shall have a bulk density ranging from 40 to 50 lb/ft3 and particle sizes ranging from that passing through a 0.50 inch screen to that retained on a U.S. Standard #8 sieve. 2.1.7.3.Metal Rx Media: Metal Rx media shall be made exclusively of composted fallen deciduous leaves. Filter media shall be granular. Media shall be dry at the time of installation. The Metal Rx media shall have a bulk density ranging from 40 to 50 lb/ft3 and particle sizes ranging from that passing through a U.S. Standard #8 sieve to that retained on a U.S. Standard #14 sieve. 2.1.7.4.Zeolite Media: Zeolite media shall be made of naturally occurring clinoptilolite, which has a geological structure of potassium-calcium-sodium aluminosilicate. The zeolite media shall have a bulk density ranging from 44 to 48 lb/ft3, particle sizes ranging from that passing through a U.S. Standard #4 sieve to that retained on a U.S. Standard #6 sieve, and a cation exchange capacity ranging from 1.0 to 2.2 meq/g. 2.1.7.5.Granular Activated Carbon: Granular activated carbon (GAC) shall be made of lignite coal that has been steam activated. The GAC media shall have a bulk density ranging from 28 to 31 lb/ft3 and particle sizes ranging from that passing through a U.S. Standard #4 sieve to that retained on a U.S. Standard #8 sieve. REV 5/16 2.1.7.6.Zeolite-Perlite-Granular Activated Carbon (ZPG): ZPG is a mixed media that shall be composed of a 1.3 ft3 outer layer of 100% Perlite (see above) and a 1.3 ft3 inner layer consisting of a mixture of 90% Zeolite (see above) and 10% Granular Activated Carbon (see above). 2.1.7.7.Zeolite-Perlite (Zeo/Perl): Zeo/Perl is a mixed media that shall be composed of a 1.3 ft3 outer layer of 100% Perlite (see above) and a 1.3 ft3 inner layer consisting of 100% Zeolite. 2.1.7.8.CSF Leaf Media – Granular Activated Carbon (CSF/GAC): CSF/GAC is a mixed media that shall be composed of a 1.3 ft3 outer layer of 100% CSF media (see above) and a 1.3 ft3 inner layer consisting of 100% Granular Activated Carbon (see above). 2.1.7.9.Perlite – Metal Rx : Perlite/Metal Rx is a mixed media that shall be composed of a 1.3 ft3 outer layer of 100% Perlite (see above) and a 1.3 ft3 inner layer consisting of 100% Metal Rx (see above). 2.1.7.10.PhosphoSorb: PhosphoSorb media shall be made from Perlite pellets with activated alumina bound to the surface. The PhosphoSorb media pellets shall be granular and have a bulk density from 18 to 25 lb/ft3. The pellet size should range from that passing through a U.S. Standard ¼ inch sieve and retained on a #8 sieve. 2.1.8.Overflow Assembly (Where Provided): 2.1.8.1.Flow spreader shall be constructed of Linear Low-Density Polyethylene (LLDPE). Contractor to provide sealant material and installation unless completed prior to shipment. 2.1.8.2.Energy dissipater shall be constructed of polyolefins. Contractor to provide sealant material and installation unless completed prior to shipment. 2.1.8.3.Outlet riser with scum baffle shall be constructed of HDPE. Outlet riser shall have an outlet stub outside dimension (O.D.) of 12-inch diameter PVC, SDR 26 and a secondary outlet stub O.D. of 8-inch diameter PVC, SDR 26. 2.2. Steel Catch Basin & Roof Drain Components: 2.2.1.Basin shall be all welded steel construction, fabricated from ASTM A36 ¼-inch steel and shall be designed to withstand AASHTO H-20 wheel loads when placed below ground in a location that could receive direct loading. 2.2.2.Basin Grate: Grating shall be ductile iron construction and shall meet AASHTO H-20 loading requirements, and shall be provided according to ASTM A48. 2.2.3.Basin Solid Lid (below ground system design): Solid lid shall be gray cast iron, treated with non- slip surfacing, and shall meet AASHTO H-20 loading requirements, and shall be provided according to ASTM A48. 2.2.4.Basin Solid Lid (above ground system design): Solid lids shall be PVC plate with pick holes. Covers to be cut as required for top inlet roof drain pipes. REV 5/16 2.3.Precast Concrete Structure Components: 2.3.1.Precast concrete vault shall be provided according to ASTM C857 and C858. Precast concrete manhole shall be provided according to ASTM C478. 2.3.2.Vault and manhole joint sealant shall be Conseal CS-101 or approved equal. 2.3.3.If interior concrete baffle walls are provided, baffle walls shall be sealed to the interior vault walls and floor with a polyurethane construction sealant rated for use below the waterline, SikaFlex 1a or equal. Contractor to provide sealant material and installation unless completed prior to shipment. 2.3.4.Frames and covers shall be gray cast iron and shall meet AASHTO H-20 loading requirements, and shall be provided according to ASTM A48. 2.3.5.Doors shall have hot-dipped galvanized frame and covers. Covers shall have diamond plate finish. Each door to be equipped with a recessed lift handle. Doors shall meet H-20 loading requirements for incidental traffic, at a minimum, or per project specific traffic loading requirements. 2.3.6.Steps shall be constructed of copolymer polypropylene conforming to ASTM D4101. Steps shall be driven into preformed or drilled holes once concrete is cured. Steps shall meet the requirements of ASTM C478 and AASHTO M199. The ½” Grade 60 deformed reinforcing bar shall meet ASTM A615, where required. 2.3.7.Ladders shall be constructed of aluminum and steel reinforced copolymer polypropylene conforming to ASTM D4101. Ladder shall bolt in place. Ladder shall meet all ASTM C497 load requirements. Ladders provided upon request or where required, and shall not conflict with the operation and accessibility to perform maintenance of the StormFilter. 2.4.Contractor Provided Components (below ground installation): 2.4.1.All contractor-provided components shall meet the requirements of this section, the plans specifications and contract documents. In the case of conflict, the more stringent specification shall apply. 2.4.2.Sub-base: Crushed rock base material shall be six-inch minimum layer of ¾-inch minus rock. Compact undisturbed sub-grade materials to 95% of maximum density at +/-2% of optimum moisture content. Unsuitable material below sub-grade shall be replaced to engineer’s approval. 2.4.3.In-situ concrete, if required, shall have an unconfined compressive strength at 28 days of at least 3000 psi, with ¾-inch round rock, a 4-inch slump maximum, and shall be placed within 90 minutes of initial mixing. 2.4.4.Silicone Sealant shall be pure RTV silicone conforming to Federal Specification Number TT S001543A or TT S00230C or Engineer approved. REV 5/16 2.4.5.Grout shall be non-shrink grout meeting the requirements of Corps of Engineers CRD-C588. Specimens molded, cured and tested in accordance with ASTM C109 shall have minimum compressive strength of 6,200 psi. Grout shall not exhibit visible bleeding. 2.4.6.For manhole systems, Contractor shall connect to 12-inch or 8-inch diameter outlet riser with Fernco flexible coupling, or approved equal. 2.4.7.Rebar used on applicable Catch Basin & Roof Drain systems shall meet ASTM A615M Grade 420 (60 ksi) or as otherwise specified in the general technical specifications. 2.4.8.Backfill material shall be ¾-inch minus crushed rock, or approved equal. 3.PERFORMANCE 3.1.Cartridge Operation: Each StormFilter shall contain one or more siphon actuated media filter cartridges that maintain a uniform pressure profile across the face of the filter during operation. At the design flow rate the maximum filter hydraulic loading rate is not to exceed 2.1 gallons per minute per square foot of filter surface area. Stormwater shall enter the filter cartridges through sides and shall flow through the filter media radially from the outer perimeter to the inner cartridge lumen and shall have an average contact time no less than 38 seconds. These media filter cartridges will incorporate a self-cleaning mechanism to remove accumulated material from the cartridge media surface that is activated when the siphon breaks. 3.2.Documentation of Sediment Removal: The StormFilter system shall have the State of Washington Department of Ecology, General Use Level Designation (GULD) Certification and current approval status from the New Jersey Department of Environmental Protection (NJDEP). 3.3.Cartridge Sediment Loading: Filter cartridges shall be of a design that has demonstrated a minimum sediment retention capacity of 22 pounds of silty loam per cartridge in laboratory tests without a reduction in hydraulic capacity. Laboratory data shall be corroborated with field observations/data demonstrating equivalent or improved longevity without impacting normal hydraulic performance of the StormFilter. All laboratory and field tests submitted in support of this specification must have undergone peer review by outside entity other than Contech. 3.4.Overflow: 3.4.1.Vault Configuration: StormFilter shall have a baffled, non-siphoning internal overflow with a minimum capacity of 1.8 cfs. 3.4.2.Manhole Configuration: The filter system will have a baffled, non-siphoning internal overflow with a minimum of 1.0 cfs capacity. 3.4.3.Peak Diversion Configuration: Each StormFilter shall include an internal, offline overflow bypass. Water first enters an inlet bay that is separate from the cartridge bay and separate from the outlet bay. Low flows travel from the inlet bay, through a transfer opening and into the cartridge bay. High flows enter the outlet bay by topping a weir separating the inlet and outlet bay. Flow rates beyond the treatment design flow shall bypass, and not enter the cartridge bay. 3.4.4.Catch Basin Configuration: Each StormFilter shall include an internal, offline overflow bypass. REV 5/16 Water enters through the grate into the inlet bay that is separate from the cartridge bay and separate from the outlet bay. Low flows travel from the inlet bay, through a transfer opening and into the cartridge bay. High flows enter the outlet bay by topping the baffled weir separating the inlet and outlet bay. Flow rates beyond the design flow (overflow) will not enter the cartridge bay. Minimum of 0.5 cfs overflow capacity. 3.4.5.Roof Drain Configuration: Minimum of 1 cfs overflow capacity. 3.4.6.Infiltration Manhole Configuration: The filter system will have a baffled, non-siphoning internal overflow with a minimum of 1.0 cfs capacity. 3.5.Linear Grate Configuration Vault Access: All portions of the vault, inlet bay, outlet bay and filtration bay shall be directly accessible from the surface through removable grated openings or solid covers. 4.EXECUTION 4.1.Precast Concrete Structure: 4.1.1.Set precast structure on crushed rock base material that has been placed in maximum 6-inch lifts, loose thickness, and compacted to at least 95-percent of the maximum dry density as determined by the standard Proctor compaction test, ASTM D698, at moisture content of +/-2% of optimum water content. 4.1.2.Structure floor shall slope 1/4 inch maximum across the width and slope downstream 1 inch per 12 foot of length. For manholes “Length” is defined by a line running from the invert of the outlet through the center of the manhole and “width” is the perpendicular to the “length”. Structure top finish grade shall be even with surrounding finish grade surface unless otherwise noted on plans. 4.1.3.Inlet and outlet pipes shall be stubbed in and connected to precast concrete structure according to Engineer’s requirements and specifications. All connections to be sealed to minimize water intrusion. If grout is used, Contractor to grout all inlet and outlet pipes flush with or protruding up to 2 inches into interior of structure. 4.1.4.When required, ballast shall be placed to the dimensions specified by the engineer and noted on the data block. Ballast shall not encase the inlet and/or outlet piping. Provide 12” clearance from outside diameter of pipes. 4.2.Steel Catch Basin: 4.2.1.Catch basin floor shall slope 1/4 inch maximum across the width and slope downstream 1 inch per 12 foot of length. Catch basin top finish grade shall be even with surrounding finish grade surface unless otherwise noted on plans. 4.2.2.Contractor shall prevent sediment and debris from entering the filter unit during construction. 4.2.3.If necessary, the inlet chamber may be filled with clean water to assist in preventing flotation during construction until the structure is backfilled and the concrete collar is poured. REV 5/16 4.2.4.Catch basin outlet shall be connected to downstream (and upstream, if applicable) piping using a flexible-type coupling. 4.2.5.Concrete perimeter slab shall be constructed 1 foot wide and 6 inches thick. Slab shall include two #4 rebar hoops with minimum 6-inch overlap at closure. Allow 2-inch vertical spacing between hoops and minimum 2-inch clearance from concrete surfaces, or as directed by the engineer. 4.3.Clean Up: 4.3.1.Remove all excess materials, rocks, roots, or foreign material, leaving the site in a clean, complete condition approved by the engineer. The project site shall be clean and free of dirt and debris and the inlet/outlet chamber(s) and filter chamber(s) shall be free of construction debris and sediment before the allowing runoff to enter and place the system in operation. All filter components shall be free of any foreign materials including concrete and excess sealant. 4.3.2.Where applicable, Contractor shall remove the temporary filter fabric around the inlet grate to place the system in operation. 4.3.3.Where required, the 4-inch cleanout plug in the overflow weir wall shall remain in place for proper operation of the system. 4.4.Filter Cartridges: 4.4.1.Filter cartridges shall be delivered installed in the structure, unless otherwise agreed upon with Contech. Contractor shall take appropriate action to protect the cartridges from sediment and other debris during construction. The method ultimately selected shall be at Contractor’s discretion and Contractor’s risk. Some methods for protecting the cartridges include, but are not limited to: 4.4.1.1.Remove cartridges from the structure and store appropriately. Cartridges shall be reinstalled to operate according to 4.4.2 (see below). 4.4.1.2.If structure is equipped with underdrain bypass piping, Contractor may leave cartridges in the vault and allow stormwater entering collection system to bypass filter bay through underdrain bypass piping. 4.4.1.3.Leave cartridges in the structure and plug inlet and outlet pipe to prevent stormwater from entering the vault, and provide means for stormwater to bypass the StormFilter. 4.4.2.Filter cartridges shall not be placed in operation until the structure is clean and the project site is clean and stabilized (construction erosion control measures no longer required). The project site includes any surface that contributes storm drainage to the StormFilter. All impermeable surfaces shall be clean and free of dirt and debris. All catch basins, manholes and pipes shall be free of dirt and sediments. Contact Contech to assist with system activation and/or inspect the system for proper installation once site is clean and stabilized. 4.5.Contractor to install filter cartridges. Specifications for alternate cartridge installation methods available by contacting Contech directly. REV 5/16 4.5.1.Filter Cartridges with ¼-Turn Connector Fittings:Tape shall be cleanly and completely removed from manifold fitting openings. ¼-turn connects shall be glued and inserted into all manifold fittings to be equipped with a filter cartridge. Filter cartridges shall be turned onto the connector until they reach the hard stop on the connector – approximately ¼ revolution, with care to not “over turn” the cartridge, or turn with such force to damage the hard stop mechanism. Plugs shall be inserted without glue in all manifold fittings not equipped with a filter cartridge. 5.INSPECTION AND MAINTENANCE 5.1.Maintenance and Inspection shall be in performed in accordance with Contech’s recommendations for maintenance and inspection. 5.2.Maintenance and inspection intervals shall be per Contech’s recommendations, or per the approving/local jurisdiction/agency requirements; whichever is more frequent. 5.3.Surface access for personnel and equipment for inspection and maintenance activities shall be provided. END OF SECTION Appendix D:Maintenance MAINTENANCE INSTRUCTIONS FOR FULL INFILTRATION Your property contains an on-site BMP (best management practice) called “full infiltration,” which was installed to mitigate the stormwater quantity and quality impacts of some or all of the impervious surfaces on your property. Full infiltration is a method of soaking runoff from impervious area (such as paved areas and roofs) into the ground. If properly installed and maintained per Appendix A of the City of Renton’s Surface Water Design Manual, full infiltration can manage runoff so that a majority of precipitation events are absorbed. Infiltration devices, such as gravel filled trenches, drywells, and ground surface depressions, facilitate this process by putting runoff in direct contact with the soil and holding the runoff long enough to soak most of it into the ground. To be successful, the soil condition around the infiltration device must be reliably able to soak water into the ground for a reasonable number of years. Infiltration Devices The infiltration devices used on your property include the following as indicated on the site plan (CHECK THE BOX(ES) THAT APPLY): gravel filled trenches, drywells, ground surface depressions. MAINTENANCE RESTRICTIONS The size, placement, and composition of these devices as depicted by the site plan and design details must be maintained and may not be changed without written approval from the City of Renton or through a future development permit from the City of Renton. INSPECTION FREQUENCY AND MAINTENANCE GUIDELINES • Infiltration devices must be inspected annually and after major storm events to identify and repair any physical defects. • Maintenance and operation of the system should focus on ensuring the system’s viability by preventing sediment-laden flows from entering the device. Excessive sedimentation will result in a plugged or non-functioning facility. • If the infiltration device has a catch basin, sediment accumulation must be removed on a yearly basis or more frequently if necessary. • Prolonged ponding around or atop a device may indicate a plugged facility. If the device becomes plugged, it must be replaced. • Keeping the areas that drain to infiltration devices well swept and clean will enhance the longevity of these devices. • For roofs, frequent cleaning of gutters will reduce sediment loads to these devices. RECORDING REQUIREMENT These full infiltration on-site BMP maintenance and operation instructions must be recorded as an attachment to the required declaration of covenant and grant of easement per Requirement 3 of Section C.1.3.4 of the City of Renton Surface Water Design Manual. The intent of these instructions is to explain to future property owners, the purpose of the BMP and how it must be maintained and operated. These instructions are intended to be a minimum; the City of Renton may require additional instructions based on site-specific conditions. See the City of Renton’s Surface Water Design Manual website for additional information and updates. TYPICAL FULL INFILTRATION APPLICATIONS FLOW HOUSE FLOW 48 INCH DIAMETER HOLE FILLED WITH 1 1 2" - 3" WASHED DRAIN ROCK PLAN VIEW NTS SECTION NTS MARK CENTER OF HOLE WITH 1" CAPPED PVC OR OTHER MEANS FLUSH WITH SURFACE ROOF DOWNSPOUT OVERFLOW SPLASH BLOCK TOPSOIL FINE MESH SCREEN MIN. 4" DIA. PVC PIPE SIDES OF HOLE LINED WITH FILTER FABRIC CATCH BASIN (YARD DRAIN) 15' MIN. AS REQUIRED, SEE SECTION C.2.2.3 VARIES 1' MIN. MIN. 1' ABOVE SEASONAL HIGH GROUNDWATER TABLE, SEE SECTION C.2.2.2 HOUSE ROOF DOWNSPOUT ROOF DOWNSPOUT CATCH BASIN (YARD DRAIN) 48 INCH DIAMETER HOLE FILLED WITH 1 1 2" - 3" WASHED DRAIN ROCK 5' MIN. SETBACK FROM BUILDING