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Ex_10_90%_Design_Report
SE 172ND STREET AND 125TH AVENUE SE GREEN STORMWATER INFRASTRUCTURE | 90% DESIGN REPORT 1 TABLE OF CONTENTS 1.0 Introduction ........................................................................................................................................ 1 2.0 Basin Description .............................................................................................................................. 2 3.0 Site Description ................................................................................................................................. 2 4.0 Minimum Requirements .................................................................................................................... 5 5.0 Alternatives Considered And Preferred Alternative .......................................................................... 9 6.0 Design Analysis ............................................................................................................................... 10 7.0 Quantify the Water Quality Benefit .................................................................................................. 15 8.0 Engineer’s Opinion of Probable Cost .............................................................................................. 17 9.0 Proposed Schedule ......................................................................................................................... 17 10.0 Preliminary Plans and other Attachments ....................................................................................... 18 1.0 INTRODUCTION This project will plan and design stormwater system modifications and green stormwater infrastructure (GSI) to improve water quality and drainage capacity for approximately half a block (600 ft) of 122nd Ave SE, 123rd Ave SE, 124th Ave SE and 125th Ave SE, north of SE 172nd St, and approximately two blocks (1,400 ft) of SE 172nd Street. The project consists of installing new conveyance system and green infrastructure, such as pervious sidewalks and Washington State Department of Ecology (Ecology) approved general-use-level designation (GULD) facilities to collect and treat stormwater runoff from approximately 2 acres of pollution-generating hard surface (PGHS). This is a stormwater retrofit project with the design partly funded by Ecology Design Grant WWQSWPC-2016-Renton-00058. Other improvements include increasing the capacity of existing stormwater conveyance systems to mitigate for flooding and nuisance ponding and decrease ice accumulation in poor drainage areas during winter months. This project will help restore water quality within the City of Renton and downstream to Soos Creek, the Green River, and Puget Sound. This Design Report presents the design updates per the project 90% Submittal for Ecology’s review. DATE JULY 21, 2021 TO KEVIN EVANS, PE, SURFACE WATER UTILITY ENGINEER, CITY OF RENTON FROM OSBORN CONSULTING, INC. | CHEYENNE COVINGTON, PE & SWAPNA SRIDHARAN, PE SUBJECT SE 172ND STREET AND 125TH AVENUE SE GSI PROJECT | 90% DESIGN REPORT RECEIVED Clark Close 02/05/2024 PLANNING DIVISION DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 SE 172ND STREET AND 125TH AVENUE SE GREEN STORMWATER INFRASTRUCTURE | 90% DESIGN REPORT 2 1.1 PROJECT LOCATION The City of Renton (COR) GSI retrofit project is within the Soos Creek main sub-basin, in the Benson Hill neighborhood. See Figure 1 for project location. Figure 1 | Vicinity Map and Project Location 2.0 BASIN DESCRIPTION Based on COR GIS information, the project is within the Soos Creek Drainage Basin. The runoff from the project site discharges into a series of wetlands that discharge to Big Soos Creek, which eventually discharges to the Green River near Highway 18, east of Auburn. Surface flows enter the wetland located approximately 150 ft south of the intersection of 127th Ave SE and SE 172nd Street through piped conveyance systems, collecting runoff from residential streets and areas east of the project limits on SE 172nd Street. Big Soos Creek is 303(d)-listed waterbody by Ecology. See Appendix B-2 for drainage basins, general topography, and existing stormwater infrastructure. 3.0 SITE DESCRIPTION The project limits are approximately half a block (600 ft) north of SE 172nd St, on 122nd Ave SE, 123rd Ave SE, 124th Ave SE, and 125th Ave SE (hereby referred to in this report as the north-south streets) and approximately two blocks (1,400 ft) along SE 172nd St between 122nd Ave SE and 127th Ave SE. Project limits are shown in Appendix B-1. The neighborhoods within the project limits are residential with R-6 zoning and will remain residential post-project improvements. The roadways and parcel areas within the site are overall flat with less than 1% longitudinal slopes along the roadways. 122nd Ave SE, 123rd Ave SE, and 124th Ave SE each have a 50-foot right-of-way (ROW), and 125th Ave SE and SE 172nd Street have 60-foot ROWs. The project site has 6–15% slopes and a water table depth varies per the project Geotechnical Report in Appendix A. DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 SE 172ND STREET AND 125TH AVENUE SE GREEN STORMWATER INFRASTRUCTURE | 90% DESIGN REPORT 3 3.1 PROPOSED SITE IMPROVEMENTS The project proposes to provide 20-foot driving lanes (10-foot on either side) of the existing roadway. The project will provide 6 feet of parking on at least one side of all streets. A 6-foot landscape buffer is proposed between the roadway and the proposed 5-foot sidewalk on one side of the street of each of the streets within the project limits. Typical sections for each street are provided on the contract plans, Appendix F. 3.2 EXISTING STORMWATER FEATURES Currently, stormwater is collected and conveyed from parcels and ROW along SE 172nd St and west of 122nd Ave SE into the existing storm system south of SE 172nd St via 12-inch concrete pipes up to the intersection at 125th Ave SE. Stormwater from the north-south streets and offsite parcel areas is collected and conveyed east through private parcels to 125th Ave SE through existing 18-inch concrete pipes, and then south to connect to an existing catch basin at the intersection of 125th Ave SE and SE 172nd St that is approximately 9 ft deep. Stormwater is then conveyed east in 24-inch concrete pipes along SE 172nd St to the intersection on 127th Ave SE, where a 42-inch concrete pipe conveys runoff from east of SE 172nd St and north of 127th Ave SE south to an existing wetland. The existing wetland is located south of the intersection of 127th Ave SE and SE 172nd St. There are known locations of flooding at the intersection of 127th Ave SE and SE 172nd St, and improvements to existing conveyance system capacities is proposed in addition to providing water quality retrofit benefits within the project limits. The project discharges to “Wetland A”, which is a Category II depressional wetland with a habitat score of 6, buffer width of 100-feet and setback of 15-feet. There is also a “Wetland B” near the project area, which is a Category III wetland with a habitat score of 4, buffer width of 50-feet and setback of 15-feet, which is not impacted by the project. See Appendix G for the entire wetland delineation report. 3.3 SOILS The project Geotechnical Report (Appendix A) dated March 23, 2020, documents borings at each of the streets within the project limits. In general, based on boring information, the soils have higher permeability in the near the surface with lower permeability till start at a depth of 1 to 5 feet below the surface. This is consistent with the United State Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) soils data, showing soils in hydrologic soil group B/D (Appendix A). The depth to groundwater was observed at a depth of 4 to 6 feet below the surface, except at Boring EB- 2 along 125th Street SE where groundwater was not observed to a depth of 11.5 feet. The groundwater was interpreted as perched on the underlying till soils with interflow anticipated when the vertical infiltration is impeded due to the less permeable till soils. Per Section 12, Pervious Concrete Sidewalks, of the Geotechnical Report, stormwater infiltration through the proposed pervious sidewalks will “migrate horizontally as vertical infiltration will be impeded by the underlying Vashon lodgement till.” Per the Geotechnical Report recommendations, Section 14 Infiltration Feasibility Recommendations, due to the variable depth of Vashon till, infiltration from concentrated flows is not recommended; “however, dispersed through pervious sidewalks should mimic that resulting from the to-be-converted pervious DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 SE 172ND STREET AND 125TH AVENUE SE GREEN STORMWATER INFRASTRUCTURE | 90% DESIGN REPORT 4 landscaped areas.” Infiltration at the water quality facility collection locations are not proposed with this project. Due to the proximity of underground utilities, a vacuum truck pothole was used to remove the uppermost 4 feet of soil at each boring location prior to Geotechnical investigations. Soil sample analysis was not completed within the shallow soils within this disturbance depth. For modeling purposes, forested A/B soils are used to simulate predeveloped conditions for surface conditions since the upper soils have higher infiltration rates. 3.4 PROPOSED STORMWATER FEATURES Several alternatives for design were considered (see Section 5.0). The summary below is based on the 90% project design for this report: Proposed stormwater facilities along the north-south streets and SE 172nd Ave have been designed to collect runoff from a minimum of 2 acres of PGHS within the project ROW via connections to proposed water quality treatment systems before discharging to the wetland, south of SE 172nd St. To improve existing conveyance capacities, allow for City maintenance access, and mitigate for flooding concerns due to large drainage areas flowing through aging stormwater pipes crossing through the private parcels, the existing stormwater systems in the north-south streets that flow easterly toward 125th Ave SE are disconnected and plugged at the upstream end. The existing upstream flows from outside the project limits are rerouted and conveyed southerly along the north-south streets through proposed 18- inch bypass systems, that connect to a new proposed bypass system, which flows easterly, along SE 172nd St. These flows from the large upstream areas bypass the proposed water quality treatment systems. Collected stormwater within the project limits along the north-south streets is treated in GULD treatment systems with the treated stormwater discharged back into the adjacent bypass systems. The conveyance system layout is based water quality treatment using precast Filterra Bioretention Systems (Filterras) with an internal piped inlet. Similarly, runoff from SE 172nd St is collected and treated in a Filterra southwest of the intersection of SE 172nd St and 124th Ave SE. East of this intersection, the north side (half the road from the crown) of SE 172nd street is captured for approximately 600 feet in a new conveyance system and directed to a proposed Filterra east of 125th Ave SE. See Appendix B-1 and B-2 for the onsite and offsite contributing areas to the proposed water quality treatment systems. The conveyance connections and Filterra treatment systems are shown in the 90% design plans in Appendix F. The precast Filterras with a piped inlet are used to provide water quality along the north-south streets and part of SE 172nd St. These Filterra boxes have an inlet chamber with an internal weir overflow leading into the media to provide water quality treatment. The proposed water quality treatment facilities using Filterras are designed to provide enhanced treatment to reduce concentrations of total suspended solids (TSS), total phosphorus, dissolved copper, dissolved zinc, and oil, before discharging to Soos Creek. The Filterra units are sized at the GULD infiltration rate of 175 in/hr that is above the approved hydraulic loading rates for Phosphorus and Oil treatment, but removal of these elements at a lower concentration is anticipated. Big Soos Creek is a Category 5, 303(d) listed waterbody as described in Section 7.0. The proposed stormwater treatment systems help improve water quality in the watershed and provide improved conveyance capacities to mitigate for existing flooding. Area summaries and facility sizing for each water quality facility are discussed in Section 6.0. Permeable pavement is used throughout the project for the proposed sidewalks. These stormwater BMPs provide infiltration of rainfall onto the permeable surfaces. DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 SE 172ND STREET AND 125TH AVENUE SE GREEN STORMWATER INFRASTRUCTURE | 90% DESIGN REPORT 5 Potholing has been completed with the 90% design phase to confirm depths of critical existing utility crossings. The anticipated utility crossings are identified on the plans in Appendix F. The bypass storm system and the storm conveyance to the Filterras are designed to be on the same side of the road to limit excavation impacts. Existing active ductile iron and abandoned asbestos concrete waterlines are generally located on the opposite side of the road. The proposed improvements are designed to provide a minimum horizontal separation (10 ft) and vertical separation (1.5 ft) between stormwater systems and waterlines. 4.0 MINIMUM REQUIREMENTS The project design meets the requirements of the 2017 COR Surface Water Design Manual (SWDM) and the 2019 Stormwater Management Manual for Western Washington (2019 SWMMWW). See Table 1 for a breakdown of project existing hard surface, new hard surface, replaced hard surface, new pollution-generating hard surface (PGHS), new non-pollution-generating hard surface (NPGHS) and effective impervious surfaces. The runoff from the project is conveyed in existing and proposed conditions via a series of conveyance pipe systems, that discharge to the wetland. The entire project is within a single TDA. The project level and TDA level analysis of minimum requirements are summarized below. DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 SE 172ND STREET AND 125TH AVENUE SE GREEN STORMWATER INFRASTRUCTURE | 90% DESIGN REPORT 6 TABLE 1 | PROJECT/TDA AREA BREAKDOWN WITHIN ROW Condition Area (sq.ft) Area (ac) Total Project Area 211,545 4.86 Existing Conditions Hard surface (roadway + driveway) 152,420 3.50 Pervious Area 59,125 1.36 Proposed/Developed Conditions Pervious sidewalk (NPGHS) 11,872 0.27 New PGHS (roadway + driveway) 2,039 0.05 Other NPGHS (Ramps) 3,622 0.08 Total New Hard Surface (Roadway, Pervious Sidewalk, and Newly paved gravel areas) 17,533 0.40 Total Replaced Hard Surface (Roadway)1 48,724 1.12 Existing to Remain Hard Surface 91,331 2.10 Total Proposed Hard Surface Area 157,588 3.62 Total New Effective Impervious Surface (excluding pervious sidewalk) 5,661 0.13 Pervious Area 53,957 1.24 Ratio of New plus Replaced Hard Surface/Existing Hard Surface x 100 (%) 43% (<50% threshold to trigger treatment of replaced impervious surfaces) 1Replaced hard surface areas include driveway and utility trench resurfacing See Appendix C (Figure I-3.2, 2019 SWMMWW) for the minimum requirement flow chart, which lists the minimum requirements that trigger project/TDA thresholds for a redevelopment project. The project adds more than 5,000 sf of new hard surfaces; therefore, all minimum requirements #1 through #9 apply for a new hard surfaces. The new plus replaced hard surface adds is less than 50% of existing impervious surface, which classifies this as a retrofit project. With the new PGHS less than 5,000 sf, all of the water quality treatment provided is for stormwater retrofit purposes. Summary of Minimum Requirements (Project and TDA Level) 1. Minimum Requirement #1 | Preparation of Stormwater Site Plans: Stormwater site plans are provided in Appendix F. 2. Minimum Requirement #2 | Construction Stormwater Pollution Prevention Plan (SWPPP): A SWPPP report will be provided prior to project construction. DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 SE 172ND STREET AND 125TH AVENUE SE GREEN STORMWATER INFRASTRUCTURE | 90% DESIGN REPORT 7 3. Minimum Requirement #3 | Source Control of Pollution: The project is a retrofit project in a residential neighborhood, and there are no known industrial sites or source control pollutions of concern within the project limits or proposed construction activities. 4. Minimum Requirement #4 | Preservation of Natural Drainage Systems and Outfalls: As summarized in Section 3, the project discharges to a wetland located at the southeast end of the project, south of the intersection of 127th Ave SE and SE 172nd St. Stormwater runoff to this discharge location is maintained with the proposed improvements to match the existing flows to the downstream wetlands. 5. Minimum Requirement #5 | On-Site Stormwater Management: Per Ecology’s 2019 SWMMWW Section I-3.4.5, projects that are not categorized as Flow Control Exempt and trigger Minimum Requirements #1 through #9 (Appendix C - per Figure I-3.3 Applicability of the Minimum Requirements) shall: · Use the BMPs for each type of surface in List #2; use the first BMP that is feasible See Figure I-3.3 in Appendix C for a flow chart to determine the requirements of Minimum Requirement #5. Table I-3.2 in Appendix C provides the BMPs in List #2 that are considered in order, as follows: o BMP T5.13: Post-Construction Soil Quality and Depth Establishing a minimum soil quality and depth will provide improved on-site management of stormwater flow and water quality. Soil retention and soil quality, including depth of soils, shall be established, per Section V-11 of Ecology’s 2019 SWMMWW, for all disturbed areas that do not have impervious surfaces, such as landscaped areas within the project limits. o BMP T5.30: Full Dispersion: Full Dispersion is not a feasible BMP since there is not sufficient area to provide dispersion within the project ROW limits. o BMP T5.15: Permeable Pavements Permeable pavement is provided for all 5-ft wide sidewalks within the project limits. See Appendix F for plans showing location of permeable pavements. This BMP is also discussed further in in Section 6.2. o BMP T7.30: Bioretention Bioretention is not feasible due to grading constraints within the project limits. 6. Minimum Requirement #6 | Runoff Treatment: Since the project adds more than 10,000 SF of total new hard surfaces (Table 1), runoff treatment must be evaluated for this redevelopment project at the project level (Appendix C – Figure I-3.2, 2019 SWMMWW). However, at the TDA level, the project adds less than 5,000 SF new pollution-generating hard surface (PGHS), runoff treatment is not required to be provided for the project at the TDA level (Section I-3.4.6, 2019 SWMMWW). To meet Ecology’s grant application goals, the project must provide a design for green infrastructure that will collect, treat, and infiltrate stormwater runoff from approximately 2 acres of PGHS within the ROW before it reaches Big Soos Creek. Table 2 summarizes treatment for pollution generating surfaces for each roadway within the ROW. The total PGHS area treated within the ROW is 2.41 ac. The offsite impervious areas are not included in the PGHS totals but DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 SE 172ND STREET AND 125TH AVENUE SE GREEN STORMWATER INFRASTRUCTURE | 90% DESIGN REPORT 8 are included in the sizing calculations for water quality, summarized in Table 4 and shown in Appendix B-1. TABLE 2 | CONTRIBUTING PGHS AREA TO BMPS WITHIN THE ROW Street Name PGHS Area (ac) 122nd Ave SE 0.42 123rd Ave SE 0.42 124th Ave SE 0.44 125th Ave SE 0.51 SE 172nd St* 0.62 Total Treatment Area (ac) 2.41 *Includes area treated in Filterras 7. Minimum Requirement 7 | Flow Control: Per Appendix C – Figure I-3.2, 2019 SWMWW, flow control applies to the redevelopment project at the project level analysis. At the TDA level, the total effective impervious surface (total hard surface, excluding pervious sidewalks) is less than 10,000 SF (Table 1), flow control requirement is not triggered at the TDA level for this project. Section I-3.4.7, 2019 SWMMWW). 8. Minimum Requirement 8 | Wetlands Protection: The project/TDA discharges stormwater runoff via conveyance pipe systems to a wetland. Per Appendix C – Figure I-3.5 and Section I-3.4.8 of 2019 SWMWW, since flow control is not triggered at the TDA level analysis, wetlands hydroperiod analysis is not required for the redevelopment project. The project discharges to Wetland A, which is a Category II depressional wetland (Section 3.2). Figure I-3.5 in Appendix C is used to determine the level of wetland protection requirements. Even though the wetland is a depressional wetland, the project proponent does not have legal access to the wetland. The following wetland protection levels apply: o General Protection: General protection measures as outlined in 2019 SWMMWW Section I-C.2 must be employed for the wetland o Protection from Pollutants: All protection measures from pollutants outlined in the 2019 SWMWW Section I-C.3 are provided by the project, including a SWPPP (MR #2), Source Control of Pollution (MR #3), On-site stormwater management (MR #5) and runoff treatment BMPs (MR #6) prior to discharge into the wetland. 9. Minimum Requirement 9 | Operation and Maintenance: All proposed stormwater BMPs shall be operated and maintained per guidance provided in the 2019 SWMMWW. The following Tables from the manual shall be used for each BMP proposed: o Permeable Pavement: Table V-A.22 o Filterras: Follow manufacturer’s Operations and Maintenance manual guidelines DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 SE 172ND STREET AND 125TH AVENUE SE GREEN STORMWATER INFRASTRUCTURE | 90% DESIGN REPORT 9 In Summary: At the Project Level: • Minimum Requirements 1-5 apply for the new and replaced hard surfaces and the land disturbed areas, and • Minimum Requirements 1-9 apply for the new hard surfaces and the converted vegetation areas. At the TDA Level: • Minimum Requirements 1-5 apply for the new and replaced hard surfaces, converted vegetation areas and the land disturbed areas, and • Minimum Requirements 6, 7 and 8 are not triggered and the Runoff Treatment provided for the project are for Retrofit purposes only. 5.0 ALTERNATIVES CONSIDERED AND PREFERRED ALTERNATIVE Alternatives analysis was performed during the 30% design phase of the project. Three (3) options were considered: · Option 1 proposed using Filterras and bioretention for treatment purposes. · Option 2 proposed using only Filterras for treatment. · Option 3 proposed using Filterras to treat additional areas (more than the minimum 2 acres) outside the project limits to improve water quality within the Soos Creek watershed at a potentially lower cost/benefit ratio. Each alternative compared the treatment sizes using the cost per square foot ($/SF) of right-of-way PGHS areas treated. The alternatives also considered long-term maintenance costs versus up-front costs for each of the alternatives. Option 2 was chosen as the preferred alternative. COR preferred installation of Filterras along the north- south streets (in a 50-ft ROW) and along SE 172nd St (in a 60-ft ROW) to meet the minimum treatment goal of 2 acres. Bioretention was found to be infeasible due to grading constraints within the project limits. Option 3 was not selected because the Options 1 and 2 both exceed the treatment goals for this project with available funding and additional offsite treatment areas did not lower the cost/benefit ratio significantly. On streets with minimal ROW limits, the less trafficked and residential north-south streets, Filterras were preferred to maximize the available space for street parking. Filterras are smaller units that provide equivalent treatment performance to bioretention systems in meeting water quality requirements. The units are also simpler to install, and vendors may provide installation as part of their overall cost. COR currently maintains several Filterras and finds them to be more cost-efficient in terms of annual maintenance costs compared to the bioretention systems. The bypass system also allows for a fewer number of treatment systems. The roadway conveyance system directs captured flow from multiple catch basins to a single treatment facility. The treated flow from the water quality systems are then connected to the bypass conveyance system to keep the targeted untreated flows directed to the water quality systems. Without the roadway collection and bypass systems approximately 39 Filterra Units, rather than the 9 proposed units, would be required to treat the same area with a single unit upstream of each catch basin. The unit price for a 4’x4’ Filterra unit (minimum size) is approx. $15,000 and unit price for a 4’x6’ Filterra Unit, which is used in current design is approx. $18,000. With the bypass system, approximately 39 4’x4’ units would be required to treat the DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 SE 172ND STREET AND 125TH AVENUE SE GREEN STORMWATER INFRASTRUCTURE | 90% DESIGN REPORT 10 same contributing areas and would increase the treatment cost by over $400,000. Even though the bypass system does not directly convey water to the treatments systems, it significantly reduces the cost of the water quality systems to be installed for the project, as well as future maintenance costs for these systems. 6.0 DESIGN ANALYSIS 6.1 DESIGN CRITERIA The proposed stormwater systems are described in Section 3.0. Design criteria for the proposed stormwater features are as described below: · Pipe material is provided in the project specifications with typically a minimum 2-ft cover over top of pipe, per Table 4.2.1.A2 of the COR 2017 SWDM. For shallow cover installations, ductile iron (DI) pipe with a minimum 1-foot cover over top of pipe is used. · Minimum pipe slopes of 0.5% are provided to maintain minimum velocities of 3 fps (Section 4.2.1.1, COR SWDM, 2017). Pipe slopes are designed to be less than 10% on stormwater mainlines to avoid using pipe anchors (Table 4.2.1.A3, COR SWDM, 2017). · For dissimilar pipe sizes connecting to the same structure, the crown of pipes are required to match, per Section 4.2.1.1 of the COR 2017 SWDM. · The maximum pipe size for a Catch Basin Type 1 is 12-inches for PP and 18-inches for DI (at allowed pipe deflection angles). · For Catch Basin Type 2, 48-inch diameter, the maximum pipe size is 24-inches for PP and 30- inches for ductile iron per Table 4.2.1.B of COR SWDM, 2017 (at allowed pipe deflection angles). · Backwater analysis is performed using PCSWMM modeling. The 25-year design storm is used for pipe sizing and backwater analysis and the 100-year design storm is used to confirm that overtopping is not anticipated. Additional ditch flows from SE 170th Pl is added to the model to determine if proposed pipes have sufficient capacity. No capacity concerns were found with the added flows. See Appendix D-1 to D-3 for modeling results of the existing and proposed stormwater systems along SE 172nd St. · See Appendix D-4 for the modeling results for Filterras. · Filterras are sized for enhanced treatment using a Ksat value of 175 in/hr, per Ecology GULD approval recommendations. · Filterras are sized to meet the 91% flow-through treatment requirement per Ecology standards. 6.2 BEST MANAGEMENT PRACTICES (BMPS) Based on the Ecology 2019 SWMMWW, the following BMPs were chosen for this project. Locations of BMPs are shown on the contract plans, and sizes are shown in Table 4. 1. BMP T5.15 | Permeable Pavements Proposed 5-ft wide sidewalks within the ROW are Portland cement concrete permeable pavement, per Figure 5.3.4 of the Ecology 2019 SWMMWW. Per Americans with Disabilities Act (ADA) requirement, the sidewalks slope toward the roadway at a 1.5% slope, 2.0% maximum. Per 2019 SWMMWW, a minimum of 1-foot separation is required below the permeable pavement, to high seasonal groundwater. Per Appendix F, the depth of the proposed permeable pavement is 10 inches. From Appendix A, the highest groundwater was observed at 4-feet. This provides adequate separation to groundwater. DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 SE 172ND STREET AND 125TH AVENUE SE GREEN STORMWATER INFRASTRUCTURE | 90% DESIGN REPORT 11 2. BMP T7.30 | Bioretention Cells, Swales and Planter Boxes Per discussion in Section 4.0, due to inadequate separation from groundwater for contributing areas of greater than 5,000 SF, bioretention is an infeasible BMP to meet MR 5 requirements. Also, due to grading constraints within the project limits, bioretention is considered to be infeasible. 3. Emerging Technologies Per Chapter 12 of the Ecology 2019 SWMMWW, emerging technologies that are GULD-approved can be used. Filterras are GULD-approved products that are used in the project for water quality treatment. Per Ecology approval, 175 in/hr is used as the infiltration rate for both basic and enhanced treatment. Enhanced treatment is provided within the project limits where Filterras are used for treatment. The peak 15-minute offline flow rate is used to calculate the Filterra sizes using WWHM. Filterra configuration is shown in Appendix F. 6.3 HYDROLOGIC AND HYDRAULIC ANALYSIS 6.3.1 C ONVEYANCE C APACITIES The existing system is shallow and does not have adequate cover along SE 172nd St. Per feedback from communities, additional flooding at the intersection of 127th Ave SE and SE 172nd St is due to inlets becoming clogged during snowfall. The existing stormwater system along SE 172nd St was modeled in the Personal Computer Stormwater Management Model (PCSWMM) to determine locations of flooding. Per City of Renton’s Stormwater Design Manual (SWDM) 2017, new pipe systems shall be designed with sufficient capacity to convey and contain (at minimum) the 25-year flow, assuming developed conditions for onsite tributary areas and existing conditions for offsite tributary areas. Also, pipe systems may overtop for runoff events that exceed 25-year design capacity, provided the overflow from the 100-year runoff does not create or aggravate a severe flooding problem or severe erosion problem, as described in Section 1.2.2 of SWDM, 2017. WWHM version 4.2.16 was used to determine offsite peak flow rates from the north-south streets, which contribute to the existing and proposed systems on SE 172nd Street. The offsite areas are shown in Appendix B-2 and Table 3. The 25-year and 100-year peak flow rates were input into PCSWMM at upstream structures on each roadway, as shown in Table 3 and Appendix D. DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 SE 172ND STREET AND 125TH AVENUE SE GREEN STORMWATER INFRASTRUCTURE | 90% DESIGN REPORT 12 TABLE 3 | BACKWATER MODELING - PEAK FLOW RATES FOR NORTH-SOUTH STREETS Street Name Effective Offsite Impervious Area (ac) Effective Offsite Pervious Area (ac) WWHM 25-Year Peak Flow (cfs) WWHM 100-Year Peak Flow (cfs) Cascade Shopping Center Offsite 25.65 11.36 10.87 - 122nd Ave SE 2.50 1.60 10.74 13.48 123rd Ave SE 2.34 1.59 1.66 2.04 124th Ave SE 2.38 1.61 1.68 2.08 125th Ave SE 2.09 1.17 1.47 1.82 127th Ave SE (North) 16.59 16.59 12.55 15.77 127th Ave SE (South) 6.02 6.02 4.43 5.54 Totals 57.57 39.94 Effective Offsite Impervious area = 50% of Offsite Parcel Area + 100% Offsite Roadways. See Appendix B for figure. Under existing conditions, the existing structures and 12-inch pipes, upstream of the intersection of 125th Ave SE and SE 172nd St, indicated locations of flooding during the 25-year storm event, as shown in Appendix D. Using the design criteria in Section 6.1, the proposed bypass system was also modeled in PCSWMM to verify adequate cover over the pipe and to confirm the pipe sizes at 18-inches for the bypass systems until the intersection at SE 125th Ave and SE172nd Street. The existing system east of this intersection consists of 24-inch pipes. 18-inch pipes are used for the bypass system, since the upstream existing pipes running east-west are 18-inch pipes. The model results indicate that this provides adequate capacities for pipes and mitigates for flooding concerns along SE 172nd St when the tailwater was set to the top of the highest water elevation in the wetland at 385-ft, based on survey flags. There are no additional flooding concerns at the intersection of 127th Ave SE and SE 172nd St (Appendix D). Maximum internal bypass flows that can be handled by Filterras is 1.4 cfs (Appendix F). This is approximately twice the 100-year flows directed to the Filterra units, shown in the WWHM2012 result of Appendix D-1, with the roadway conveyance and separate drainage bypass conveyance systems. From Table 3, offsite flow rates that are conveyed through the parallel drainage bypass system are much higher than the Filterra internal bypass system could handle. Based on CCTV inspections by COR, no additional pipe replacements are required at the intersection of 127th Ave SE and SE 172nd St. The addition of replacing two structures at this intersection is included on the plans Appendix F. DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 SE 172ND STREET AND 125TH AVENUE SE GREEN STORMWATER INFRASTRUCTURE | 90% DESIGN REPORT 13 6.3.2 W ATER Q UALITY T REATMENT M ODELING WWHM was used to size the Filterras facilities. Calculations per the WWHM output files are provided in Appendix D and summarized in Table 4 . The PGHS treated area is 2.41 acres, as discussed in Section 4.0 and shown on Table 2. Filterras are sized to meet the 91% flow-through treatment requirement per Ecology standards. Maximum bypass flows that can be handled by Filterras is 1.4 cfs (Appendix F), which is above the 100- year flows directed to any of the proposed systems per the WWHM Output Files, Appendix D. DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 SE 172ND STREET AND 125TH AVENUE SE GREEN STORMWATER INFRASTRUCTURE | 90% DESIGN REPORT 14 TABLE 4 | WATER QUALITY SIZING - FILTERRAS Street Name Filterra No. Proposed Improvements within the ROW Existing Parcel Areas WWHM Inputs WWHM Modeling Results2 Roadway Impervious Area (ac) Sidewalk NPGHS (ac) Other NPGHS (ac) Pervious Landscape (ac) Pervious within ROW (ac) Offsite Area (ac) Offsite Impervious (ac)1 Offsite Pervious (ac) Total Impervious (ac) Total Pervious (ac) Total Area (ac) Offline Flowrates (cfs) Peak 100-yr flow rate (cfs) Filterra Media Size (ftxft) 122nd Ave SE F-1 0.22 0.03 0.00 0.04 0.07 1.38 0.69 0.69 0.93 0.80 1.73 0.083 0.949 4x6 F-2 0.20 0.04 0.00 0.04 0.08 1.24 0.62 0.62 0.86 0.74 1.60 0.077 0.878 4x6 123rd Ave SE F-3 0.21 0.03 0.00 0.04 0.08 1.40 0.70 0.70 0.94 0.82 1.76 0.084 0.963 4x6 F-4 0.21 0.03 0.00 0.04 0.07 1.32 0.66 0.66 0.90 0.77 1.67 0.080 0.917 4x6 OK 124th Ave SE F-5 0.21 0.03 0.00 0.04 0.07 1.40 0.70 0.70 0.94 0.81 1.75 0.084 0.960 4x6 F-6 0.23 0.03 0.00 0.04 0.08 1.36 0.68 0.68 0.93 0.80 1.73 0.083 0.949 4x6 125th Ave SE F-7 0.26 0.03 0.01 0.08 0.06 1.00 0.50 0.50 0.79 0.64 1.43 0.071 0.793 4x6 F-8 0.25 0.02 0.02 0.08 0.06 1.17 0.67 0.50 0.96 0.64 1.60 0.086 0.919 4x6 SE 172nd St F-9 0.43 0.03 0.05 0.06 0.14 0.70 0.35 0.35 0.85 0.55 1.40 0.076 0.808 4x6 F-10 0.19 0.03 0.05 0.08 0.06 0.16 0.08 0.08 0.27 0.22 0.49 0.025 0.209 4x4 Total Sidewalk (NPGHS) Treated (ac) 0.27 Total PGHS Treated (ac) 2.41 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 SE 172ND STREET AND 125TH AVENUE SE GREEN STORMWATER INFRASTRUCTURE | 90% DESIGN REPORT 15 7.0 QUANTIFY THE WATER QUALITY BENEFIT Based on the summaries in Table 4, 2.41 acres of pollution-generating impervious surface area from within the City’s ROW will be treated with this project. This exceeds Ecology’s Design Grant goal of 2 acres for this project. Retrofit projects are not required to meet the new and redevelopment criteria established in the Municipal Stormwater General Permits. Filterras provide enhanced treatment for stormwater runoff, which reduces concentrations of TSS, total phosphorus, dissolved heavy metals, and oil. The Filterra units are sized at the GULD infiltration rate of 175 in/hr, which is above the approved hydraulic loading rates for Phosphorus and oil treatment, but removal of these elements at a lower concentration is anticipated. Phosphorous and oil treatment are not required for the project runoff. Runoff from the project discharges into a wetland, which discharges to Big Soos Creek. Big Soos Creek is a 303(d) impaired waterbody by the Department of Ecology with Category 5 impairments for dissolved oxygen, temperature and bacteria. Enhanced treatment through the proposed facilities will contribute to improved water quality in the watershed. The removal of heavy metals and phosphorus through the proposed treatment facilities can limit the growth of algae and aquatic plants that degrade dissolved oxygen levels and increase temperatures. Removal of dissolved heavy metals can also improve the health of aquatic species. For retrofit projects, comparing the size of the proposed retrofit BMP to the size of a BMP design to meet new or redevelopment criteria determines the level of water quality benefit provided by the project. Ecology requires that the recipients of Ecology funds calculate both the “Flow Control Ratio” and the “Runoff Treatment Ratio” to demonstrate the retrofit water quality benefit. This project provides treatment for the full design flow rates of contributing areas. Tables 5 quantifies the redevelopment area for Filterras per guidelines in Section D of the “Design Deliverables for Stormwater Project with Ecology Funding” document. A total of 2.41 acres of PGHS within the City ROW is treated by the proposed water quality facilities. A Total of 15.18 acres are treated by the water quality facilities, including adjacent residential parcels that could not be separated from the contributing flows. In existing conditions, the roadway has thickened edges that do not isolate the landscaped areas and the landscaped areas are regularly used as an extended parking area. The landscaping soils are therefore compacted and susceptible to direct pollutants from vehicles. In proposed conditions, a 6-inch curb will be added to one side of the roads, isolating the roadway from the landscaped areas and proposed pervious sidewalk. The proposed bypass conveyance system is used to divert large offsite flows around the proposed water quality facilities. The water quality systems are targeting roadway surfaces within the project limits. Without the bypass systems, the water quality flows would exceed the manufactures peak flow rates for the largest precast systems. As shown in Table 3, and Figure B-2 of Appendix B, there are over 43 acres of offsite area draining through the project limits due to existing conveyance systems. The onsite water quality facilities provide treatment for approximately 2.41 acres of PGHS from within the City ROW and total of 15.18 acres contributing areas. DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 SE 172ND STREET AND 125TH AVENUE SE GREEN STORMWATER INFRASTRUCTURE | 90% DESIGN REPORT 16 Per Tables 5, the total equivalent new/redeveloped area that is retrofitted is 15.18 Ac. TABLE 5 | QUANTIFYING NEW/DEVELOPMENT AREA FOR THE RETROFIT PROJECT - FILTERRAS Street Name BMP # Design flow rate for proposed retrofit BMP (cfs) Design flow rate to meet new/redevelopment criteria (cfs) Ratio=Flow rate for proposed retrofit BMP/flow rate for new or redevelopment BMP (1 max) Total Contributing Area to BMP (ac) Equivalent New/Development Area = Ratio x contributing area to BMP (ac) 122nd Ave SE F-1 0.097 0.083 1 1.73 1.73 F-2 0.097 0.077 1 1.60 1.60 123rd Ave SE F-3 0.097 0.084 1 1.76 1.76 F-4 0.097 0.080 1 1.67 1.67 124th Ave SE F-5 0.097 0.084 1 1.75 1.75 F-6 0.097 0.083 1 1.73 1.73 125th Ave SE F-7 0.097 0.071 1 1.43 1.43 F-8 0.097 0.086 1 1.60 1.60 SE 172nd St F-9 0.097 0.076 1 1.40 1.40 F-10 0.065 0.025 1 0.49 0.49 Total New/Development Area with Filterras (ac) 15.18 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 SE 172ND STREET AND 125TH AVENUE SE GREEN STORMWATER INFRASTRUCTURE | 90% DESIGN REPORT 17 8.0 ENGINEER’S OPINION OF PROBABLE COST An opinion of project costs at the 90% design level is $3,290,300, as summarized in Appendix E. These include the BMPs discussed in Section 6.2 and the proposed stormwater conveyance systems to treat proposed improvements while mitigating for nuisance flooding within the project limits. This includes a 10% contingency at the 90% design level. Of the project costs, the Ecology eligible costs are estimated to be $2,904,600. The bid items related to the proposed sidewalk improvements have been removed for the eligible costs per feedback from Ecology after the 60% Design submittal. The list of excluded bid items is included in Appendix E. Additional ROW improvements include reducing the existing roadway impervious areas to provide 20-ft wide driving widths to calm traffic and providing 6-ft parking along at least one side of each roadway. Landscape buffers (6 ft wide) and pervious concrete sidewalks (5 ft wide) are provided per the COR planning and roadway improvement requirements for redevelopment areas (Renton Municipal Code 4-4- 060). The proposed sidewalks meet the requirements of Permeable Pavements (BMP T5.15) as required, where feasible, per Minimum Requirement 5. Curb ramps were added at intersections of north-south streets to SE 172nd St to provide ADA access within the project limits. The proposed landscape areas are meeting the Post-Construction Soil Quality and Depth (BMP T5.13) BMP requirements. The proposed landscape areas and permeable sidewalk provides water quality benefit to the project as described in Section 7. Concrete curb ramps are proposed at all intersections to meet the ADA guidelines. The bypass system allows for a fewer number of treatment systems to treat the targeted PGHS within the project limits, as described in Section 7. The roadway conveyance system directs captured flow from multiple catch basins to a single treatment facility, then connects to the bypass conveyance system to keep targeted untreated flows directed to the water quality systems. Without the roadway collection and bypass systems approximately 39 Filterra Units, rather than the 9 proposed units, would be required to treat the same area with a single unit upstream of each catch basin. The bypass system also diverts the over 43 acres draining through the project limits around the water quality systems. 9.0 PROPOSED SCHEDULE The revised Design Report along with 90% plans and estimate will be submitted to Ecology for review in July 2021. The 100% submittal is planned for Fall 2021, with revisions starting after Ecology review and acceptance letter, up to 45 days. The bid construction documents planned to be completed by Fall 2022 with construction to beginning of the Spring of 2023. Construction grant funding will be applied for through the Ecology Fiscal Year 2023 Funding Cycle in the Fall of 2021. DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 SE 172ND STREET AND 125TH AVENUE SE GREEN STORMWATER INFRASTRUCTURE | 90% DESIGN REPORT 18 PRELIMINARY PLANS AND OTHER ATTACHMENTS Appendix A – Geotechnical – Soils Appendix B – Drainage Area Breakdown · Appendix B-1 – Contributing Areas to Water Quality Systems · Appendix B-2 – Offsite Area Maps Appendix C – Minimum Requirements Appendix D – Modeling Results · Appendix D-1 – BMP Sizing – Filterras · Appendix D-2 – PCSWMM – Backwater Analysis Appendix E – Preliminary Opinion of Probable Cost Appendix F – 90% Plans and BMP Details Appendix G –Wetland Delineation Report Appendix H – Email Communications DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Appendix A Geotechnical - Soils DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 associated earth sciences incorporated Associated Earth Sciences, Inc. 911 5th Avenue Kirkland, WA 98033 P (425) 827 7701 Subsurface Exploration, Geologic Hazard, and Geotechnical Engineering Report SE 172ND ST. AND 125TH AVE. SE GSI Prepared For: OSBORN CONSULTING, INC. Project No. 20190100H001 March 23, 2020 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Kirkland | Tacoma | Mount Vernon 425-827-7701 | www.aesgeo.com March 23, 2020 Project No. 20190100H001 Osborn Consulting, Inc. 1800 112th Avenue NE, Suite 220-E Bellevue, Washington 98004 Attention: Mr. Cheyenne Covington, P.E. Subject: Subsurface Exploration, Geologic Hazard, and Geotechnical Engineering Report SE 172nd St. and 125th Ave. SE GSI Renton, Washington Dear Mr. Covington: We are pleased to present the enclosed copies of the above-referenced report. This report summarizes the results of our subsurface exploration, geologic hazard, and geotechnical engineering studies and offers recommendations for the design and development of the proposed project, as currently envisioned. Our recommendations are preliminary in that construction details have not been finalized at the time this report was prepared. We have enjoyed working with you on this study and are confident that the recommendations presented in this report will aid in the successful completion of your project. If you should have any questions, or if we can be of additional help to you, please do not hesitate to call. Sincerely, ASSOCIATED EARTH SCIENCES, INC. Kirkland, Washington ______________________________ Jennifer H. Saltonstall, L.G., L.Hg. Principal Geologist/Hydrogeologist JHS/ld - 20190100H001-2 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 SUBSURFACE EXPLORATION, GEOLOGIC HAZARD, AND GEOTECHNICAL ENGINEERING REPORT SE 172ND ST. AND 125TH AVE. SE GSI Renton, Washington Prepared for: Osborn Consulting, Inc. 1800 112th Avenue NE, Suite 220-E Bellevue, Washington 98004 Prepared by: Associated Earth Sciences, Inc. 911 5th Avenue Kirkland, Washington 98033 425-827-7701 March 23, 2020 Project No. 20190100H001 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Subsurface Exploration, Geologic Hazard, and SE 172nd St. & 125th Ave. SE GSI Geotechnical Engineering Report Renton, Washington Project and Site Conditions March 23, 2020 ASSOCIATED EARTH SCIENCES, INC. JG/ld - 20190100H001-2 Page 1 I. PROJECT AND SITE CONDITIONS 1.0 INTRODUCTION This report presents the results of Associated Earth Sciences, Inc.’s (AESI’s) subsurface exploration, geologic hazard, and geotechnical engineering study for the proposed SE 172nd Street and 125th Avenue SE Green Stormwater Infrastructure (GSI) project located in Renton, Washington. (See the “Vicinity Map,” Figure 1.) The approximate locations of the explorations accomplished for this study are presented on Figure 2. An aerial image and LIDAR-based topography for the near-project area are presented on Figure 3. In the event that any changes in the nature, design, or location of the stormwater improvements are planned, the conclusions and recommendations contained in this report should be reviewed and modified, or verified, as necessary. 1.1 Purpose and Scope The purpose of this study was to provide subsurface data to be utilized in the design and construction of the above-referenced project. Our study included reviewing available geologic literature, drilling five exploration borings, and performing geologic studies to assess the type, thickness, distribution, and physical properties of the subsurface sediments and groundwater conditions. Geologic hazard evaluations and geotechnical engineering studies were also conducted to determine suitable geologic hazard mitigation techniques, temporary shoring/excavation, backfill recommendations, dewatering recommendations, and infiltration feasibility recommendations. This report summarizes our current geotechnical fieldwork and offers geotechnical hazard mitigation and development recommendations based on our present understanding of the project. 1.2 Authorization Written authorization to proceed with this study was granted by Osborn Consulting, Inc. by means of our signed “Agreement for Professional Services - Subconsultant,” dated April 24, 2019. This report has been prepared for the exclusive use of Osborn Consulting, Inc., the City of Renton, and their agents, for specific application to this project. Within the limitations of scope, schedule, and budget, our services have been performed in accordance with generally accepted geotechnical engineering and engineering geology practices in effect in this area at the time our report was prepared. No other warranty, express or implied, is made. DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Subsurface Exploration, Geologic Hazard, and SE 172nd St. & 125th Ave. SE GSI Geotechnical Engineering Report Renton, Washington Project and Site Conditions March 23, 2020 ASSOCIATED EARTH SCIENCES, INC. JG/ld - 20190100H001-2 Page 2 2.0 PROJECT AND SITE DESCRIPTION The City of Renton SE 172nd St. and 125th Ave. SE GSI project area consists of approximately 4,500 lineal feet of full street right-of-way within the City of Renton extending approximately half a block north of SE 172nd Street along 122nd Avenue SE, 123rd Avenue SE, 124th Avenue SE, 125th Avenue SE, and approximately two blocks along SE 172nd Street. Stormwater runoff from these streets is currently collected and conveyed east through private parcels and south within a street right-of-way into a storm system on SE 172nd Street where it discharges into a wetland located approximately 150 feet south of the intersection of SE 172nd Street and 127th Avenue SE. This runoff eventually flows into Big Soos Creek. The topography in the site area is generally flat lying to gently sloping, with asphalt-surfaced roadways and gravel or grass-covered shoulders. The existing paved surfaces include patching related to the installation of a waterline. Based on our review of project plans provided by Osborn Consulting, Inc., we understand that the current water system is a replacement of an abandoned water system which included lines under the eastern shoulders of 122nd through 125th Avenues. The proposed improvements include a new stormwater conveyance system, with 12- and 18-inch-diameter stormlines, and various green infrastructure improvements, such as bioretention facilities and pervious concrete sidewalks supplemented with General Use Level Designation (GULD) facilities to collect and treat stormwater runoff from approximately 2 acres of impervious surfaces. Based on our review of “60% submittal” plan set by Osborn Consulting, Inc., dated September 27, 2019, we anticipate site grading to include limited cuts and fills, and stormline installation to include trench depths ranging from approximately 3 to 10 feet. Much of the alignment of the proposed sidewalks will be at or near to the alignment of the above-mentioned abandoned water system. 3.0 SUBSURFACE EXPLORATION AESI completed a subsurface exploration program consisting of five exploration borings on February 4, 2020, to gain subsurface information about the site. The various types of soils, as well as the depths where characteristics of the soils changed, are indicated on the exploration logs presented in Appendix A. The depths indicated on the logs where conditions changed may represent gradational variations between soil types. Our explorations were approximately located in the field by measuring from known site features and are shown on Figure 2 and Figure 3. The conclusions and recommendations presented in this report are based, in part, on the exploration borings completed for this study. The number, locations, and depths of the explorations were completed within site/access constraints including those posed by existing DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Subsurface Exploration, Geologic Hazard, and SE 172nd St. & 125th Ave. SE GSI Geotechnical Engineering Report Renton, Washington Project and Site Conditions March 23, 2020 ASSOCIATED EARTH SCIENCES, INC. JG/ld - 20190100H001-2 Page 3 buried utilities, overhead lines, and driveways. The boring locations were selected to provide both general site information and area-specific information based on the proposed site layout. Changes to the site layout may require the completion of additional subsurface explorations. Because of the nature of exploratory work below ground, interpolation of subsurface conditions between field explorations is necessary. It should be noted that differing subsurface conditions may be present due to the random nature of deposition and the alteration of topography by past grading and/or filling. The nature and extent of any variations between the field explorations may not become fully evident until construction. If variations are observed at that time, it may be necessary to re-evaluate specific recommendations in this report and make appropriate changes. 3.1 Exploration Borings To avoid damaging existing utilities, a vacuum truck was used to remove the uppermost 4 feet of soil from each boring. The exploration borings were then completed by a track-mounted drill rig advancing a hollow-stem auger. During the drilling process, samples were obtained at generally 2.5- or 5-foot-depth intervals. The exploration borings were continuously observed and logged by a geologist from our firm. The exploration logs presented in Appendix A are based on the field logs, drilling action, and inspection of the samples secured. Disturbed but representative samples were obtained by using the Standard Penetration Test (SPT) procedure in accordance with ASTM International (ASTM) D-1586. This test and sampling method consists of driving a standard 2-inch, outside-diameter, split-barrel sampler a distance of 18 inches into the soil with a 140-pound hammer free-falling a distance of 30 inches. The number of blows for each 6-inch interval is recorded, and the number of blows required to drive the sampler the final 12 inches is known as the Standard Penetration Resistance (“N”) or blow count. If a total of 50 blows are recorded at or before the end of one 6-inch interval, the blow count is recorded as the number of blows for the corresponding number of inches of penetration. The resistance, or N-value, provides a measure of the relative density of granular soils or the relative consistency of cohesive soils. These values are plotted on the attached boring logs. The samples obtained from the split-barrel sampler were classified in the field, and representative portions placed in watertight containers. The samples were then transported to our laboratory for further visual classification and geotechnical laboratory testing, as necessary. The various types of soil and groundwater elevations, as well as the depths where soil and groundwater characteristics changed, are indicated on the exploration boring logs presented in Appendix A of this report. DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Subsurface Exploration, Geologic Hazard, and SE 172nd St. & 125th Ave. SE GSI Geotechnical Engineering Report Renton, Washington Project and Site Conditions March 23, 2020 ASSOCIATED EARTH SCIENCES, INC. JG/ld - 20190100H001-2 Page 4 4.0 SUBSURFACE CONDITIONS Subsurface conditions at the project site were inferred from the field explorations completed for this study, visual reconnaissance of the site, and review of applicable geologic literature. As shown on the boring logs, the exploration borings generally encountered a variable thickness of fill over glacial sediments. The following section presents more detailed subsurface information organized from the youngest (shallowest) to the oldest (deepest) soil types. 4.1 Stratigraphy Asphalt/Crushed Rock A surficial layer of asphalt pavement underlain by crushed rock road base was encountered at all exploration locations. Asphalt pavement thickness was generally 4 to 6 inches thick, with approximately 4 inches of crushed rock road base underneath. Fill Fill soils (soils not naturally placed) were encountered at the locations of exploration borings EB-2 through EB-4 to approximate depths of 3 feet to 5 feet below the ground surface. This fill generally consisted of medium dense, dark brown, sandy gravel with some silt. We interpret the encountered fill as likely resulting from past grading activities associated with roadway and/or plat construction. Fill thicknesses can vary over short distances and may be deeper than observed in our explorations. We are not aware of available documentation for placement of the existing fill or trench backfill. As our explorations were located to avoid existing buried utilities, we did not encounter trench backfill. From the plans provided by Osborn Consulting, it is likely that the proposed improvements will encounter existing fill and trench backfill associated with the existing buried utilities. Although our explorations did not encounter large debris, cobbles, or boulders within the fill, these materials may be present at random locations and depths. Due to their variable density and content, the existing fill soils are not suitable for direct support of grade-sensitive pipelines. Depending on site conditions at the time of construction, remediation of the fill may be feasible with recompaction or removal and replacement with structural fill. Vashon Ice Contact Deposits At exploration boring EB-2, beneath the fill, our exploration encountered medium dense, silty, fine sand ranging to stiff, sandy silt with trace coarse sand dropstones, interpreted as ice contact deposits. Ice contact deposits can consist of a wide variety of sediment types initially deposited above, adjacent to, or within a glacial ice mass and later re-deposited when the ice melts. Ice contact sediments can be normally consolidated or glacially overridden. Ice contact deposits at this site primarily consist of fine sand and silt and are considered moisture sensitive. At the DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Subsurface Exploration, Geologic Hazard, and SE 172nd St. & 125th Ave. SE GSI Geotechnical Engineering Report Renton, Washington Project and Site Conditions March 23, 2020 ASSOCIATED EARTH SCIENCES, INC. JG/ld - 20190100H001-2 Page 5 location of EB-2, the ice contact sediments extended below the maximum depth explored of 11.5 feet below the ground surface. Vashon Lodgement Till Sediments encountered below the fill at exploration borings EB-1, EB-3, EB-4, and EB-5 generally consisted of dense to very dense, silty sand with some gravel. We interpret these sediments to be representative of Vashon lodgement till. The Vashon lodgement till was deposited directly from basal, debris-laden glacial ice during the Vashon Stade of the Fraser Glaciation approximately 12,500 to 15,000 years ago. The high relative density of the unweathered till is due to its consolidation by the massive weight of the glacial ice from which it was deposited. This unit is generally suitable for support of pipelines. All sediments of glacial origin may contain large cobbles or boulders at random locations. At the locations of EB-1, EB-3, EB-4, and EB-5, the lodgement till extended below the maximum depths explored of 10.3 feet below the ground surface. 4.2 Regional Mapping Geologic Mapping Review of the regional geologic map titled Geologic Map of the Renton Quadrangle, King County, Washington, U.S. Geological Survey (USGS) Publication GQ-405, by D.R. Mullineaux (1965) indicates that the site is underlain by Vashon lodgement till (Qvt). Our interpretation of the sediments encountered at the subject site is in general agreement with the regional geology map. Soil Mapping Review of the US Department of Agriculture Natural Resources Conservation Service (NRCS) Web Soil Survey indicates that the soil in the vicinity of the site consists of Arents-Alderwood and Alderwood soils series. Arents-Alderwood soils are Alderwoods soils that have been disturbed by urbanization. Alderwood soils generally form from the weathering of glacial till. An area of as Seattle muck (Sk) soils is present in a low area extending south from 127th Avenue. Seattle muck soils are generally associated with wetland areas. Our interpretation of the sediments encountered at the subject site is in general agreement with the regional soils map. 4.3 Hydrology At the time of our explorations, we encountered groundwater seepage in exploration borings EB-1, EB-3, EB-4, and EB-5 at depths of approximately 4 feet to 6 feet. These depths generally corresponded with the slightly oxidized, moist soils that were observed within the upper portion of the Vashon lodgement till sediments indicating that perched groundwater likely occurs DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Subsurface Exploration, Geologic Hazard, and SE 172nd St. & 125th Ave. SE GSI Geotechnical Engineering Report Renton, Washington Project and Site Conditions March 23, 2020 ASSOCIATED EARTH SCIENCES, INC. JG/ld - 20190100H001-2 Page 6 seasonally. Perched groundwater, also known as “interflow,” occurs when vertical infiltration is impeded by less-permeable soils and horizontal migration occurs. It should be noted that groundwater levels below the site fluctuate in response to such factors as changes in season, precipitation, and on- and off-site land use. Our field explorations were conducted in early February when groundwater levels are typically elevated. 4.4 Laboratory Testing We completed laboratory testing of selected soil samples collected from our exploratory borings. A total of four grain-size analyses were performed. Copies of the laboratory test results are included in Appendix B. DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Subsurface Exploration, Geologic Hazard, and SE 172nd St. & 125th Ave. SE GSI Geotechnical Engineering Report Renton, Washington Geologic Hazards and Mitigations March 23, 2020 ASSOCIATED EARTH SCIENCES, INC. JG/ld - 20190100H001-2 Page 7 II. GEOLOGIC HAZARDS AND MITIGATIONS The following discussion of potential geologic hazards is based on the geologic conditions as observed and discussed herein. 5.0 LANDSLIDE HAZARDS AND MITIGATION Due to the relatively flat site topography and distance to significant slopes, it is our opinion that the risk of damage to the proposed project by landsliding is low. Provided that the recommendations presented in this report are properly followed, no additional landslide hazard mitigation is recommended for this project. 6.0 SEISMIC HAZARDS AND MITIGATION Earthquakes occur in the Puget Lowland with great regularity. The vast majority of these events are small and are usually not felt by people. However, large earthquakes do occur, as evidenced by the 1949, 7.2-magnitude event; the 1965, 6.5-magnitude event; and the 2001, 6.8-magnitude event. The 1949 earthquake appears to have been the largest in this area during recorded history. Evaluation of return rates indicates that an earthquake of a magnitude between 6.0 and 7.0 is likely within a given 25- to 40-year period. Generally, there are four types of potential geologic hazards associated with large seismic events: 1) surficial ground rupture, 2) seismically induced landslides, 3) liquefaction, and 4) ground motion. The potential for each of these hazards to adversely impact the proposed project is discussed below. 6.1 Surficial Ground Rupture The nearest known fault trace to the project site is the Seattle Fault Zone, which lies approximately 4 miles to the northeast. Recent studies by the USGS (e.g., Johnson et al., 1994, Origin and Evolution of the Seattle Fault and Seattle Basin, Washington, Geology, v. 22, p.71-74; and Johnson et al., 1999, Active Tectonics of the Seattle Fault and Central Puget Sound Washington - Implications for Earthquake Hazard, geological Society of America Bulletin, July 1999, v. 111, n. 7, p. 1042-1053) have provided evidence of surficial ground rupture along a northern splay of the Seattle Fault. The recognition of this fault is relatively new, and data pertaining to it are limited, with the studies still ongoing. According to the USGS studies, the latest movement of this fault was about 1,100 years ago when about 20 feet of surficial displacement took place. This displacement can presently be seen in the form of raised, wave-cut beach DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Subsurface Exploration, Geologic Hazard, and SE 172nd St. & 125th Ave. SE GSI Geotechnical Engineering Report Renton, Washington Geologic Hazards and Mitigations March 23, 2020 ASSOCIATED EARTH SCIENCES, INC. JG/ld - 20190100H001-2 Page 8 terraces along Alki Point in West Seattle and Restoration Point at the south end of Bainbridge Island. The recurrence interval of movement along this fault system is still unknown, although it is hypothesized to be in excess of several thousand years. Due to the suspected long recurrence interval, the potential for surficial ground rupture is considered to be low during the expected life of the project, and no mitigation efforts beyond complying with the current 2015 International Building Code (IBC) are recommended. 6.2 Seismically Induced Landslides Due to the relatively flat site topography and distance to significant slopes, it is our opinion that the risk of damage to the proposed project by seismically induced landsliding is low. Provided that the recommendations presented in this report are properly followed, no additional landslide hazard mitigation is recommended for this project. 6.3 Liquefaction Liquefaction is a process through which unconsolidated soil loses strength as a result of vibrations, such as those which occur during a seismic event. During normal conditions, the weight of the soil is supported by both grain-to-grain contacts and by the fluid pressure within the pore spaces of the soil below the water table. Extreme vibratory shaking can disrupt the grain-to-grain contact, increase the pore pressure, and result in a temporary decrease in soil shear strength. The soil is said to be liquefied when nearly all of the weight of the soil is supported by pore pressure alone. Liquefaction can result in deformation of the sediment and settlement of overlying structures. Areas most susceptible to liquefaction include those areas underlain by non-cohesive silt and sand with low relative densities, accompanied by a shallow water table. The subsurface conditions encountered at the site pose a low risk of liquefaction due to their relatively high density from glacial consolidation. No detailed liquefaction analysis was completed as part of this study, and none is warranted, in our opinion. 6.4 Ground Motion Design of structural elements should follow 2015 IBC standards using Site Class “D” as defined in Table 20.3-1 of American Society of Civil Engineers (ASCE) 7 – Minimum Design Loads for Buildings and Other Structures. DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Subsurface Exploration, Geologic Hazard, and SE 172nd St. & 125th Ave. SE GSI Geotechnical Engineering Report Renton, Washington Geologic Hazards and Mitigations March 23, 2020 ASSOCIATED EARTH SCIENCES, INC. JG/ld - 20190100H001-2 Page 9 7.0 EROSION HAZARDS AND MITIGATION The Renton Municipal Code defines Low Erosion Hazard Areas as soils characterized by the Natural Resource Conservation Service (NRCS) as having slight or moderate erosion potential, and a slope less than fifteen percent (15%). The U.S. Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) Web Soil Survey maps the soil in the vicinity of the site as Arents-Alderwood materials, 6 to 15 percent slopes (AmC), and Alderwood gravelly sandy loam, 0 to 15 percent slopes (AgB, AgC). These soils have a slight erosion potential and are situated on slopes ranging from 0 to 15 percent. Therefore, the project site is classified as a Low Erosion Hazard Area under the Renton Municipal Code. Based on the relatively flat site topography and presence of fine-grained soils, the erosion hazard at the site is considered low to moderate, and a properly developed, constructed, and maintained erosion control plan consistent with local standards and best management practices is recommended for this project. Maintaining cover measures atop disturbed ground provides significant reduction to the potential generation of turbid runoff and sediment transport. During the local wet season (October 1st through March 31st), exposed soil should not remain uncovered for more than 2 days, unless it is actively being worked. Ground-cover measures can include erosion control matting, plastic sheeting, straw mulch, crushed rock, recycled concrete, or mature hydroseed. To reduce the potential for off-site sediment transport during construction, we recommend the following: 1. If possible, construction should proceed during the drier periods of the year, and disturbed areas should be revegetated, paved, or otherwise protected as soon as possible. 2. All stormwater from impermeable surfaces should be directed to a stormwater drainage system or temporary storage facilities and kept away from the proposed work areas. 3. Ground disturbance beyond the project alignment should be kept to a minimum. 4. Temporary sediment catchment facilities adjacent to the proposed stormwater alignment should be cleaned out and maintained periodically, as necessary, to maintain their capacity and function. Provide and maintain inlet protection of catch basins and drain systems that receive runoff from planned work areas. DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Subsurface Exploration, Geologic Hazard, and SE 172nd St. & 125th Ave. SE GSI Geotechnical Engineering Report Renton, Washington Geologic Hazards and Mitigations March 23, 2020 ASSOCIATED EARTH SCIENCES, INC. JG/ld - 20190100H001-2 Page 10 5. Soils that will be stockpiled at the site should be stored in such a manner as to reduce erosion. Protective measures may include, but are not necessarily limited to, covering with plastic sheeting or the use of straw bales/silt fences. 6. Where needed, construction access should be constructed with quarry spall surfacing or equivalent according to City of Renton regulations. Maintain existing paved surfaces, where practical, and sweep as needed. It is our opinion that with the proper implementation of the Temporary Erosion and Sedimentation Control (TESC) plans and by field-adjusting appropriate erosion mitigation (BMPs) throughout construction, the potential adverse impacts from erosion hazards on the project may be mitigated. 8.0 COAL MINE HAZARDS AND MITIGATION According to the City of Renton GIS Services COR Maps, the nearest mapped coal mine hazard lies approximately 0.25 miles to the west. No coal mine hazard analysis was completed for this study, and none is warranted in our opinion. DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Subsurface Exploration, Geologic Hazard, and SE 172nd St. & 125th Ave. SE GSI Geotechnical Engineering Report Renton, Washington Design Recommendations March 23, 2020 ASSOCIATED EARTH SCIENCES, INC. JG/ld - 20190100H001-2 Page 11 III. DESIGN RECOMMENDATIONS 9.0 INTRODUCTION Our explorations indicate that, from a geotechnical standpoint, the planned stormwater improvements are feasible provided that the recommendations in this report are followed. The sediment types excavated during trenching will likely be Vashon lodgement till, Vashon ice contact deposits, or previously placed fill. These materials will largely consist of sand with variable but significant quantities of gravel and silt, and possibly random cobbles and/or boulders. As stated above, we encountered groundwater seepage in exploration borings EB 1, EB-3, EB-4, and EB-5 at depths of approximately 4 feet to 6 feet below the ground surface, and interpreted that seepage as perched groundwater, also known as “interflow,” that likely occurs seasonally. For portions of the planned stormwater alignment extending below the interflow zone, suitable temporary shoring and trench sidewall slopes will be required to mitigate seepage and potential caving conditions. For these reasons, we recommend that construction occur during the dry season, typically between June and September, and that the contractor be prepared for saturated soils that are prone to caving and groundwater flow along the pipe alignment. New infrastructure for the project includes excavations for the drainage facilities and associated underdrains, and other piping along with street restoration. The following recommendations pertain to the site and infrastructure improvements for work occurring within the City’s public right-of-way. In general, all work shall be done in accordance with current City of Renton specifications. Based on our subsurface exploration, the material exposed at the base of the stormwater trenches is anticipated to consist of native glacial till in most areas. Ice-contact deposits (silt) were encountered in exploration boring EB-2 and may be exposed at the base of trench excavation in this area. Existing fill was encountered in most of the explorations, ranging in thickness from 3 to 5 feet. Both the glacial till and ice-contact deposits contain a significant amount of fine-grained sediments and are, therefore, not considered suitable receptor sediments for infiltrating large volumes of stormwater. 10.0 SITE PREPARATION Site preparation should include removal of all trees, brush, debris, and any other deleterious material within the proposed work area. Additionally, organic soil, if encountered, should be segregated from mineral soils in the trench excavation. Since the density and composition of the soil can vary in existing utility trenches, random soft/organic pockets may exist, and the depth DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Subsurface Exploration, Geologic Hazard, and SE 172nd St. & 125th Ave. SE GSI Geotechnical Engineering Report Renton, Washington Design Recommendations March 23, 2020 ASSOCIATED EARTH SCIENCES, INC. JG/ld - 20190100H001-2 Page 12 and extent of organics/stripping depths can best be determined in the field by the geotechnical engineer or engineering geologist. 10.1 Temporary Cut Slopes In our opinion, stable construction slopes should be the responsibility of the contractor and should be determined during construction based on the local soil and groundwater conditions encountered at the particular location at that time. We anticipate that trenched excavations for the planned stormwater improvements will likely be vertical, with trench boxes used where warranted, as described in the “Trenching Considerations” section of this report. For estimating purposes, however, we anticipate that temporary, unsupported cut slopes in fill soils or in Vashon ice contact sediments can be planned at a maximum slope of 1.5H:1V (Horizontal:Vertical), and that cut slopes in dense to very dense Vashon lodgement till sediments can be made at a maximum slope of about 1H:1V. As is typical with earthwork operations, some sloughing and raveling may occur, and cut slopes may have to be adjusted in the field. If groundwater seepage is encountered in cut slopes, or if surface water is not routed away from temporary cut slope faces, flatter slopes will be required. In addition, WISHA/OSHA regulations should be followed at all times. 10.2 Site Disturbance The contractor must use care during site preparation and excavation operations so that the underlying soils are not softened, particularly during wet weather conditions. If disturbance occurs, the softened soils should be removed and the area brought to grade with structural fill. Softened soils are defined as any soil not in a firm and unyielding condition. We anticipate that wet weather construction would increase the earthwork costs over dry weather construction. 11.0 TRENCHING CONSIDERATIONS 11.1 Excavation Much of the planned stormwater improvements will likely run below paved areas. Therefore, it will be necessary to sawcut the existing pavement prior to trenching operations. There will also likely be existing buried utilities that will complicate the excavation process. Overhead power lines are not expected to interfere with the planned construction, but nearby tree limbs may limit the pick-and-swing radius of the trenching equipment. We anticipate that the installation of new stormwater conveyance system, where needed, will require vertically sided trench excavations. For trenches less than 4 feet in depth, where caving DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Subsurface Exploration, Geologic Hazard, and SE 172nd St. & 125th Ave. SE GSI Geotechnical Engineering Report Renton, Washington Design Recommendations March 23, 2020 ASSOCIATED EARTH SCIENCES, INC. JG/ld - 20190100H001-2 Page 13 or groundwater seepage is not encountered, the trenches may be open-cut for access. For trenches 4 feet or deeper, or where caving, sloughing, or groundwater seepage is encountered, we recommend the use of suitable trench boxes or the temporary cut slopes described above. We anticipate that soils to be encountered during the excavation process will provide moderate resistance to digging. Cobbles and boulders should be expected during excavation. Groundwater seepage into the trench, if present, can cause some caving/sloughing to occur. The contractor should be experienced with excavating in moist to wet subgrade conditions. 11.2 Pipe Subgrade The undisturbed native soils are suitable for support of the pipe. In the event that soft, organic, or disturbed soils are encountered at the bottom of the trench, these soils should be overexcavated, up to 1 foot where needed, and replaced with structural backfill where it is encountered. An AESI representative should be onsite to observe subgrade conditions and document backfill operations. 11.3 Pipe Bedding Pipe zone bedding material should be specified by the civil engineer following the pipe manufacturer’s requirements. We recommend that pipe bedding placement should conform to Washington State Department of Transportation (WSDOT) Standard Specification 7-08.3(1)C. 11.4 Backfill The majority of the near-surface soils excavated for the proposed improvements will likely be moist, silty, fine to medium sand with gravel. These soils are suitable for use as backfill material provided they are placed at or near (within 2 percent) optimum moisture contents. The backfill soils should be substantially free of organic materials and rocks larger than about 6 inches in nominal dimension. We anticipate that during the wet season the on-site soils will not likely be suitable for backfill due to moisture contents being elevated above optimum moisture for the soil to achieve suitable compaction. Above the pipe zone bedding material, on-site sediments may be used for backfill provided that they can be compacted to at least 95 percent of the modified Proctor maximum dry density, as defined by ASTM D-1557. If the material excavated from the trench is not suitable for backfill due to high moisture or a high degree of deleterious material, then imported backfill soil consisting of material conforming to WSDOT Standard Specification 9-03.10 “Bank Run Gravel for Trench Backfill” may be used and compacted to the required density. If select import material is not available, or if there is a need for a higher strength material or in areas congested by other utilities making compaction difficult, a controlled density fill (CDF) may be used. We recommend the use DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Subsurface Exploration, Geologic Hazard, and SE 172nd St. & 125th Ave. SE GSI Geotechnical Engineering Report Renton, Washington Design Recommendations March 23, 2020 ASSOCIATED EARTH SCIENCES, INC. JG/ld - 20190100H001-2 Page 14 of 50 to 100 pounds per square inch (psi) compressive strength CDF mix to facilitate future excavation and provide performance equivalent to well compacted soil backfill. Trench backfill should be placed in uniform, horizontal lifts and compacted to the above standard. Thickness of structural backfill layers before compaction should not exceed 1.5 feet for a large, excavator-mounted, vibratory plate-type compactor. Smaller compaction equipment will require use of thinner lifts; hand-operated mechanical compactors should be used to compact lifts no thicker than 6 inches. Final lift thickness should be based on field performance testing using actual materials under field conditions and uniform compactive effort. In some cases, additional pipe zone bedding material above the pipe may be advisable to minimize required compactive effort needed to achieve the specified density in this area. 12.0 PERVIOUS CONCRETE SIDEWALKS From “60% submittal” plans provided to AESI by Osborn Consulting, we understand that pervious concrete sidewalks are proposed along the east shoulders of 122nd Avenue SE, 123rd Avenue SE, 124th Avenue SE, 125th Avenue SE, and along the north shoulder of SE 172nd Street. The pervious concrete detail specifies 4 inches of pervious cement concrete placed over a minimum 6 inches of aggregate base surrounded by a geotextile fabric layer. An underdrain is not included. We anticipate that stormwater that passes through the pervious concrete sidewalk section will encounter existing fill, existing utility trench backfill, or the natural, glacially derived sediments. It is likely that this stormwater will enter the fill soils and migrate horizontally as vertical infiltration will be impeded by the underlying Vashon lodgement till and ice contact deposits, both of which contain large quantities of silt and fine sand. Horizontal migration of perched groundwater, known as “interflow”, occurs naturally within the subsurface, causing groundwater to infiltrate into and along the fill soils. If the current interflow within the existing fill and utility trench backfill has not caused adverse impacts to nearby utilities or roadways, it is our opinion that the relatively small amount of additional groundwater from the proposed pervious concrete sidewalks should not result in a significant increase in the risk of adverse impacts to nearby infrastructure, relative to the existing condition. The pervious sidewalk areas will generally mimic the interflow of the converted landscaped areas. 13.0 DRAINAGE AND DEWATERING CONSIDERATIONS Groundwater seepage was encountered in exploration borings EB-1, EB-3, EB-4, and EB-5 at the time of drilling, February 4, 2020. The depth of groundwater observed ranged from 4 feet to 6 feet and was interpreted as perched on the underlying Vashon lodgement till. It should be DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Subsurface Exploration, Geologic Hazard, and SE 172nd St. & 125th Ave. SE GSI Geotechnical Engineering Report Renton, Washington Design Recommendations March 23, 2020 ASSOCIATED EARTH SCIENCES, INC. JG/ld - 20190100H001-2 Page 15 noted that the depth or occurrence of groundwater seepage may vary in response to such factors as changes in season, precipitation, and site use. The quantity and duration of flow from an excavation that encounters groundwater depends on a number of factors including topography, size and depth of the excavation, proximity to surface water features, soil grain size, lateral extent of the water-bearing zone or aquifer, and season. We expect that the majority of groundwater seepage can be managed by the installation of temporary trench sump systems during trench excavation, and we recommend work proceed during the drier summer months. 14.0 INFILTRATION FEASIBILITY RECOMMENDATIONS The feasibility of stormwater infiltration depends upon the presence of a suitable receptor native soil of sufficient thickness, extent, permeability, and vertical separation from groundwater. Our explorations completed for this study encountered medium dense fill underlain by very dense, silty, Vashon lodgement till sediments or stiff Vashon ice contact deposits. Laboratory sieve analyses of samples of the Vashon lodgement till collected from borings EB-1, EB-3, EB-4, and EB-5 indicate that the lodgement till contains between 23.7 percent and 34.9 percent silt and clay-sized particles. A copy of the laboratory results is included in Appendix B. The existing fill is not a suitable infiltration receptor due to its variable texture, silt, and organic content. Because of their elevated silt content, the Vashon lodgement till and Vashon ice contact sediments underlying the site exhibit a low permeability and are not considered to be suitable receptor soils for stormwater infiltration. Therefore, infiltration is not recommended for concentrated flows; however, dispersed flow through pervious sidewalks should mimic that resulting from the to-be-converted pervious landscaped areas. 15.0 PROJECT DESIGN AND CONSTRUCTION MONITORING We are available to provide additional geotechnical consultation as the project design develops and possibly changes from that upon which this report is based. We recommend that AESI perform a geotechnical review of the plans prior to final design completion. In this way, our earthwork and foundation recommendations may be properly interpreted and implemented in the design. This review is not included in the current scope of work and budget. We are also available to provide geotechnical engineering and monitoring services during construction. The integrity of the new system depends on proper site preparation and construction procedures. In addition, engineering decisions may have to be made in the field in the event that variations in subsurface conditions become apparent. Construction monitoring DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Subsurface Exploration, Geologic Hazard, and SE 172nd 5• & 125th Ave. SE GSI Geotechnical Engineering Report Renton, Washington Design Recommendations services are not part of this current scope of work. If these services are desired, please let us know, and we will prepare a proposal. We have enjoyed working with you on this study and are confident that these recommendations will aid in the successful completion of your project. If you should have any questions, or require further assistance, please do not hesitate to call. Sincerely, ASSOCIATED EARTH SCIENCES, INC. Kirkland, Washington Joshua S. P. Greer, G.I.T. Staff Geologist Jeffrey P. Laub, L.G., L.E.G. Bruce L. Blyton, P.E. Senior Engineering Geologist Senior Principal Engineer Attachments:Figure 1:Vicinity Map Figure 2:Site and Exploration Plan Figure 3:Site Aerial and Topography Appendix A: Exploration Logs Appendix B: Laboratory Testing Results March 23, 2020 ASSOCIATED EARTH SCIENCES, INC. JG/Id - 20190100H001-2 Page 16 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 KING COUNTY KENT RENTON Copyright:© 2013 National Geographic Society, i-cubed King County 125th Ave SESE 168th St SE 172nd St121st Ave SESE170t h Pl122nd Ave SE124th Ave SE123rd Ave SE± NOTE: BLACK AND WHITE REPRODUCTION OF THIS COLOR ORIGINAL MAY REDUCE ITS EFFECTIVENESS AND LEAD TO INCORRECT INTERPRETATION VICINITY MAP PROJ NO. DATE: FIGURE:\\kirkfile2\GIS\GIS_Projects\aaY2019\VM\190100H001 F1 VM_SE172nd.aprx!( ¬«515 SITE 120190100H0012/20 0 20001000 FEET DATA SOURCES / REFERENCES: USGS: 7.5' SERIES TOPOGRAPHIC MAPS, ESRI/I-CUBED/NGS 2013 KING CO: STREETS, CITY LIMITS 1/19, PARCELS 4/19 LOCATIONS AND DISTANCES SHOWN ARE APPROXIMATE SE 172ND ST AND 125TH AVE SE GSI RENTON, WASHINGTON DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 NOTES: 1. BASE MAP REFERENCE: DUANE HARTMAN AND ASSOCIATES, INC., CITY OF RENTON - SE 172ND ST STORM WATER IMPROVEMENTS TOPOGRAPHIC SURVEY, DHA 19-2901, SURVEYED 6/19 190100 SE 172nd \ 20190100H001 F2 S-E.cdr SE 172ND ST AND 125TH AVE SE GSI RENTON, WASHINGTON SITE AND EXPLORATION PLAN PROJ NO.DATE:FIGURE: 20190100H001 2/20 2 BLACK AND WHITE REPRODUCTION OF THIS COLOR ORIGINAL MAY REDUCE ITS EFFECTIVENESS AND LEAD TO INCORRECT INTERPRETATION. a s s o c i a t e d e a r t h s c i e n c e s i n c o r p o r a t e d FEET 50 1000 N CONTOUR INTERVAL = 1’ LEGEND: EXPLORATION BORINGEB NOTE: LOCATION AND DISTANCES SHOWN ARE APPROXIMATE. EB-5 EB-3 EB-4 EB-2 EB-1 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 .LQJ&RXQW\± %/$&.$1':+,7(5(352'8&7,212)7+,6&2/2525,*,1$/0$<5('8&(,76 ())(&7,9(1(66$1'/($'72,1&255(&7,17(535(7$7,21 *˛?*,6B3URMHFWV?DD<˝?˝6(ˆQG6W?DSU[BP[G?˝+)B(6BˆQG6WDSU[352-12 '$7(˛),*85(˛ )((7 '$7$6285&(65()(5(1&(6˛ 36/&˛.,1*&2817<ˇ*5,'&(//6,=(,6 '(/,9(5<)/2:1ˇ˙ˇ &2172856)520/,'$5 26%251&2168/7,1*,1&352-(&7%281'$5<ˆ1'67 $1'˘7+$9(*5((167250:$7(5,1)5$6758&785(*6, 352-(&7ˇ68%0,77$/˝ˆ˝ .,1*&2˛675((763$5&(/6 $(5,$/3,&720(75<,17˘ /2&$7,216$1'',67$1&(66+2:1$5($3352;,0$7( ˝+ 6,7($(5,$/$1' 7232*5$3+< 6(ˆ1'67$1'˘7+$9(6(*6, 5(1721:$6+,1*721 <]vP } µ v ı Ç Z˚vı} vZ˚vı}vˇ˙ˇ˙ˇ˙ˇ˙˙˙˙ˇ˙ˇ˙ˇ˝˝˝˙˝ˇ˝ ˇ˙˙ˇ˝˙ ˙ ˝˙ 6(ˆQG/Q 6(ˆ˘WK 6W ˙WK$YH6(6(ˇˆWK6W ˆWK$YH6(VW$YH6(6(ˆWK /Q˝WK3O6(VW/Q6 ( 6(ˇ˙WK6W 6(ˆ WK3O 6(ˆWK6W 6(ˆQG6W 6 (3 H WUR Y LWV N \5 G˝WK/Q6(6 (ˆWK 3 O ˇWK3O6(ˇWK$YH6(6(ˇ ˝WK3O 6(ˇˆWK 3 O WK$YH6(WK/Q6(˝WK $YH 6 (QG/Q6(WK7HU6(6(ˇ˝WK3O 6(ˇ˝WK6W QG$YH6(WK$YH6(UG$YH6((% (% (% (% (%˘ 3LFWRPHWU\,QWHUQDWLRQDO&RUS 6,7( (;3/25$7,21%25,1* 3$5&(/ &217285)7 &217285)7 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 APPENDIX A Exploration Logs DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 13 22 32 16 18 22 33 50/5" 50/5" 50/4" Bottom of exploration boring at 20.3 feet Perched groundwater encountered at ~6 feet. Asphalt - 6 inches Crushed Rock - 4 inches Vashon Lodgement Till Dense, moist, light brownish gray, silty, fine SAND, trace to some gravel, trace cobbles; unsorted; limited recovery due to APS (SP). Vacuum truck excavated 0 to 4 feet. Drilled 4 to 21.5 feet. Very moist, gray, silty, fine SAND, trace gravel; unsorted; poor recovery (SM). Driller notes rock in the way. Very moist to wet, gray, silty, fine SAND, some gravel; unsorted (SM). Driller notes difficult drilling 10 to 20 feet. S-1 S-2 S-3 S-4 S-5 S-6 1 of 1 NAVD 88 JG2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name JHSWater Level ()Approved by: 30 Blows/Foot Samples Ground Surface Elevation (ft) Grab SampleSymbol 6.25 40 Datum Hammer Weight/Drop Sampler Type (ST): S T Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet Depth (ft)Exploration Number 20190100H001 2/4/20,2/4/20 Logged by: Shelby Tube Sample 140# / 30 Boretec / Track Rig Well~387 5 10 15 20 EB-1 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"Exploration Boring Water Level at time of drilling (ATD) SE 172nd St and 125th Ave SE GSI M - Moisture AESIBOR 20190100H001.GPJ February 25, 202054 4040 5050/5" 5050/5" 5050/4" DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 6 7 9 6 4 5 2 3 5 Bottom of exploration boring at 11.5 feet No groundwater encountered. Asphalt - 6 inches Crushed Rock - 4 inches Fill Medium dense, moist, dark brown, sandy, GRAVEL, some silt, trace organics; unsorted (GP-GM). Vacuum truck excavated 0 to 4 feet. Drilled 4 to 11.5 feet. Upper 4 inches: brown, fine to medium, SAND, some silt (SP-SM). Vashon Ice Contact Deposits Lower 8 inches: moist, gray with mottled orange oxidation, silty, fine SAND, trace gravel; massive (SM). Very moist, gray, fine sandy, SILT, trace gravel, trace coarse sand dropstones; massive (ML). S-1 S-2 S-3 S-4 1 of 1 NAVD 88 JG2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name JHSWater Level ()Approved by: 30 Blows/Foot Samples Ground Surface Elevation (ft) Grab SampleSymbol 6.25 40 Datum Hammer Weight/Drop Sampler Type (ST): S T Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet Depth (ft)Exploration Number 20190100H001 2/4/20,2/4/20 Logged by: Shelby Tube Sample 140# / 30 Boretec / Track Rig Well~389 5 10 15 20 EB-2 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"Exploration Boring Water Level at time of drilling (ATD) SE 172nd St and 125th Ave SE GSI M - Moisture AESIBOR 20190100H001.GPJ February 25, 20201616 99 1818 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 8 10 12 44 5/4" 50/5" Bottom of exploration boring at 10.4 feet Perched groundwater encountered at ~5 feet. Asphalt - 4 inches Crushed Rock - 4 inches Fill Medium dense, moist, dark brown, sandy, GRAVEL, some silt, trace fine organics; unsorted (GP-GM). Vashon Lodgement Till Vacuum truck excavated 0 to 4 feet. Drilled 4 to 10.4 feet. Very moist, light brownish gray, silty, fine SAND, trace gravel; unsorted (SM). S-1 S-2 S-3 S-4 1 of 1 NAVD 88 JG2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name JHSWater Level ()Approved by: 30 Blows/Foot Samples Ground Surface Elevation (ft) Grab SampleSymbol 6.25 40 Datum Hammer Weight/Drop Sampler Type (ST): S T Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet Depth (ft)Exploration Number 20190100H001 2/4/20,2/4/20 Logged by: Shelby Tube Sample 140# / 30 Boretec / Track Rig Well~395 5 10 15 20 EB-3 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"Exploration Boring Water Level at time of drilling (ATD) SE 172nd St and 125th Ave SE GSI M - Moisture AESIBOR 20190100H001.GPJ February 25, 20202222 505/4" 5050/5" DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 13 19 18 9 17 20 14 21 33 Bottom of exploration boring at 11.5 feet Perched groundwater encountered at ~5 to 6 feet. Asphalt - 4 inches Crushed Rock - 4 inches Fill Medium dense, moist dark brown, sandy, GRAVEL, some silt, trace fine organics; unsorted (GP-GM). Vashon Lodgement Till Vacuum truck excavated 0 to 4 feet. Drilled 4 to 11.5 feet. Poor recovery due to rock, interpreted as Lodgement Till due to blowcounts and consistent drill action with deeper samples. Moist to very moist, light brownish gray, silty, fine SAND, some gravel; unsorted (SM). S-1 S-2 S-3 S-4 1 of 1 NAVD 88 JG2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name JHSWater Level ()Approved by: 30 Blows/Foot Samples Ground Surface Elevation (ft) Grab SampleSymbol 6.25 40 Datum Hammer Weight/Drop Sampler Type (ST): S T Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet Depth (ft)Exploration Number 20190100H001 2/4/20,2/4/20 Logged by: Shelby Tube Sample 140# / 30 Boretec / Track Rig Well~402 5 10 15 20 EB-4 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"Exploration Boring Water Level at time of drilling (ATD) SE 172nd St and 125th Ave SE GSI M - Moisture AESIBOR 20190100H001.GPJ February 25, 20203737 3737 54 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 10 16 16 50/6" 50/4" Bottom of exploration boring at 10.3 feet Groundwater encountered at 4 feet. Asphalt - 4 inches Crushed Rock - 4 inches Vashon Lodgement Till Dense, moist, light brownish gray, silty, fine SAND, some gravel; unsorted (SM). Water present post Vacuum truck excavation at 4 feet. Vacuum truck excavated 0 to 4 feet. Drilled 4 to 10.3 feet. Moist to very moist, light brownish gray, silty, fine SAND, trace gravel; unsorted (SM). Poor recovery due to frequent gravel. S-1 S-2 S-3 S-4 1 of 1 NAVD 88 JG2" OD Split Spoon Sampler (SPT) 3" OD Split Spoon Sampler (D & M)Water LevelProject Name JHSWater Level ()Approved by: 30 Blows/Foot Samples Ground Surface Elevation (ft) Grab SampleSymbol 6.25 40 Datum Hammer Weight/Drop Sampler Type (ST): S T Project Number 20 Renton, WA Date Start/Finish CompletionLocation Sheet Depth (ft)Exploration Number 20190100H001 2/4/20,2/4/20 Logged by: Shelby Tube Sample 140# / 30 Boretec / Track Rig Well~403 5 10 15 20 EB-5 Ring Sample No RecoveryGraphic 10 Other TestsHole Diameter (in) DESCRIPTION Driller/Equipment Blows/6"Exploration Boring Water Level at time of drilling (ATD) SE 172nd St and 125th Ave SE GSI M - Moisture AESIBOR 20190100H001.GPJ February 25, 20203232 5050/6" 5050/4" DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 APPENDIX B Laboratory Testing Results DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Particle Size Distribution Report PERCENT FINER0 10 20 30 40 50 60 70 80 90 100 GRAIN SIZE - mm. 0.0010.010.1110100 % +3"Coarse % Gravel Fine Coarse Medium % Sand Fine Silt % Fines Clay 0.0 0.0 6.3 3.8 14.2 40.8 34.96 in.3 in.2 in.1½ in.1 in.¾ in.½ in.3/8 in.#4#10#20#30#40#60#100#140#200TEST RESULTS Opening Percent Spec.*Pass? Size Finer (Percent)(X=Fail) Material Description Atterberg Limits (ASTM D 4318) Classification Coefficients Date Received:Date Tested: Tested By: Checked By: Title: Date Sampled:Location: Onsite Sample Number: EB-1 Depth: -7.5' Client: Project: Project No:Figure Very Silty SAND Some Gravel 3/4" 3/8" #4 #8 #10 #20 #40 #60 #100 #200 #270 100.0 97.3 93.7 90.6 89.9 86.0 75.7 55.7 44.7 34.9 32.0 np nv SM A-2-4(0) 2.0444 0.7312 0.2823 0.2016 2-14-20 2-14-20 MS JL 2-4-20 Osborn Consulting Inc 125Ave SE & 172nd St. Se. GSI 190100 H001 PL=LL=PI= USCS (D 2487)=AASHTO (M 145)= D90=D85=D60= D50=D30=D15= D10=Cu=Cc= Remarks *(no specification provided) DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Particle Size Distribution Report PERCENT FINER0 10 20 30 40 50 60 70 80 90 100 GRAIN SIZE - mm. 0.0010.010.1110100 % +3"Coarse % Gravel Fine Coarse Medium % Sand Fine Silt % Fines Clay 0.0 0.0 7.5 4.8 16.7 47.3 23.76 in.3 in.2 in.1½ in.1 in.¾ in.½ in.3/8 in.#4#10#20#30#40#60#100#140#200TEST RESULTS Opening Percent Spec.*Pass? Size Finer (Percent)(X=Fail) Material Description Atterberg Limits (ASTM D 4318) Classification Coefficients Date Received:Date Tested: Tested By: Checked By: Title: Date Sampled:Location: Onsite Sample Number: EB-3 Depth: -5' Client: Project: Project No:Figure Silty SAND Some Gravel 3/4" 3/8" #4 #8 #10 #20 #40 #60 #100 #200 #270 100.0 95.9 92.5 88.8 87.7 81.1 71.0 52.4 37.8 23.7 20.1 np nv SM A-2-4(0) 2.9024 1.3856 0.3080 0.2330 0.1074 2-14-20 2-14-20 MS JL 2-4-20 Osborn Consulting Inc 125Ave SE & 172nd St. Se. GSI 190100 H001 PL=LL=PI= USCS (D 2487)=AASHTO (M 145)= D90=D85=D60= D50=D30=D15= D10=Cu=Cc= Remarks *(no specification provided) DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Particle Size Distribution Report PERCENT FINER0 10 20 30 40 50 60 70 80 90 100 GRAIN SIZE - mm. 0.0010.010.1110100 % +3"Coarse % Gravel Fine Coarse Medium % Sand Fine Silt % Fines Clay 0.0 3.3 8.7 5.3 15.7 38.5 28.56 in.3 in.2 in.1½ in.1 in.¾ in.½ in.3/8 in.#4#10#20#30#40#60#100#140#200TEST RESULTS Opening Percent Spec.*Pass? Size Finer (Percent)(X=Fail) Material Description Atterberg Limits (ASTM D 4318) Classification Coefficients Date Received:Date Tested: Tested By: Checked By: Title: Date Sampled:Location: Onsite Sample Number: EB-4 Depth: -7.5' Client: Project: Project No:Figure Silty SAND Some Gravel 1" 3/4" 3/8" #4 #8 #10 #20 #40 #60 #100 #200 #270 100.0 96.7 94.4 88.0 83.7 82.7 77.4 67.0 48.7 38.0 28.5 25.6 np nv SM A-2-4(0) 5.8272 2.9680 0.3448 0.2609 0.0862 2-14-20 2-14-20 MS JL 2-4-20 Osborn Consulting Inc 125Ave SE & 172nd St. Se. GSI 190100 H001 PL=LL=PI= USCS (D 2487)=AASHTO (M 145)= D90=D85=D60= D50=D30=D15= D10=Cu=Cc= Remarks *(no specification provided) DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Particle Size Distribution Report PERCENT FINER0 10 20 30 40 50 60 70 80 90 100 GRAIN SIZE - mm. 0.0010.010.1110100 % +3"Coarse % Gravel Fine Coarse Medium % Sand Fine Silt % Fines Clay 0.0 4.2 13.9 8.0 14.6 28.0 31.36 in.3 in.2 in.1½ in.1 in.¾ in.½ in.3/8 in.#4#10#20#30#40#60#100#140#200TEST RESULTS Opening Percent Spec.*Pass? Size Finer (Percent)(X=Fail) Material Description Atterberg Limits (ASTM D 4318) Classification Coefficients Date Received:Date Tested: Tested By: Checked By: Title: Date Sampled:Location: Onsite Sample Number: EB-5 Depth: -2' Client: Project: Project No:Figure Very Silty Gravelly SAND 1" 3/4" 3/8" #4 #8 #10 #20 #40 #60 #100 #200 #270 100.0 95.8 89.9 81.9 75.2 73.9 68.2 59.3 48.5 39.0 31.3 29.7 np nv SM A-2-4(0) 9.5979 6.1422 0.4425 0.2680 0.0577 2-14-20 2-14-20 MS JL 2-4-20 Osborn Consulting Inc 125Ave SE & 172nd St. Se. GSI 190100 H001 PL=LL=PI= USCS (D 2487)=AASHTO (M 145)= D90=D85=D60= D50=D30=D15= D10=Cu=Cc= Remarks *(no specification provided) DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Appendix B Drainage Area Breakdown DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Appendix B-1 Contributing Areas to Water Quality Systems DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 LEGEND172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTPRE-DEVELOPMENT CONDITIONSCONTRIBUTING AREASDocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 LEGENDND67$ND7+$9EG5EEN67250:$7E5,N)5$6758&785E G6, 352-E&73267DE9EL230EN7&2ND,7,2N6CONTRIBUTING AREAS(EXCLUDING OFFSITE DRAINAGE AREAS)F-10F9F8F6F7F5F4F2F1F3DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 LEGENDND67$ND7+$9EG5EEN67250:$7E5,N)5$6758&785E G6, 352-E&73267DE9EL230EN7&2ND,7,2N6ND$9E6ECONTRIBUTING HARD SURFACES WITHIN CITY ROW0$7&+L,NE6EE$%29E 0$7&+L,NE6EE%EL2: 0$7&+L,NE6EE6+EE7.E<0$3N76DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 LEGENDND67$ND7+$9EG5EEN67250:$7E5,N)5$6758&785E G6, 352-E&73267DE9EL230EN7&2ND,7,2N65D$9E6ECONTRIBUTING HARD SURFACES WITHIN CITY ROW0$7&+L,NE6EE$%29E 0$7&+L,NE6EE%EL2: 0$7&+L,NE6EE6+EE7.E<0$3N76DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 LEGENDND67$ND7+$9EG5EEN67250:$7E5,N)5$6758&785E G6, 352-E&73267DE9EL230EN7&2ND,7,2N67+$9E6ECONTRIBUTING HARD SURFACES WITHIN CITY ROW0$7&+L,NE6EE$%29E 0$7&+L,NE6EE%EL2: 0$7&+L,NE6EE6+EE7.E<0$3N76DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 LEGENDND67$ND7+$9EG5EEN67250:$7E5,N)5$6758&785E G6, 352-E&73267DE9EL230EN7&2ND,7,2N67+$9E6ECONTRIBUTING HARD SURFACES WITHIN CITY ROW0$7&+L,NE6EE$%29E 0$7&+L,NE6EE%EL2: 0$7&+L,NE6EE6+EE7.E<0$3N76DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 LEGENDND67$ND7+$9EG5EEN67250:$7E5,N)5$6758&785E G6, 352-E&73267DE9EL230EN7&2ND,7,2N66END67CONTRIBUTING HARD SURFACES WITHIN CITY ROW0$7&+L,NE6EE$%29E 0$7&+L,NE6EE%EL2:0$7&+L,NE6EE6+EE7.E<0$3N760$7&+L,NE6EE6+EE70$7&+L,NE6EE6+EE70$7&+L,NE6EE6+EE7)257+E&2N75,%87,NG$5E$62))6EE6+EE73$572)7+E)&2N75,%87,NG$5E$6$33E$56$%29E67$57,NG,00ED,$7ELL<D2:N675E$02))$ND) DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 LEGENDND67$ND7+$9EG5EEN67250:$7E5,N)5$6758&785E G6, 352-E&73267DE9EL230EN7&2ND,7,2N66END67CONTRIBUTING HARD SURFACES WITHIN CITY ROW0$7&+L,NE6EE$%29E 0$7&+L,NE6EE%EL2:.E<0$3N760$7&+L,NE6EE6+EE7N27E 2NL<7+EN257+L$NE2)ND,6D,5E&7ED72)0$7&+L,NE6EE6+EE7DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Appendix B-2 Offsite Area Maps DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 23.65ac 4.07ac 3.93ac 3.99ac 3.27ac 12.03ac 33.18ac SE 172ND ST AND 125 AVE SE GSIOFFSITE DRAINAGE BASINS DRAFT - 09/25/2019¯0 300 600 900Feet Existing Structures Existing Conveyance Wetlands Project Limits Off-Site Area A Off-Site Area B Off-Site Area D Off-Site Area E Off-Site Area C Off-Site Area G Off-Site Area F FIGURE B-2 03/05/2020 SE 172nd St122nd Ave SE123rd Ave SE124th Ave SE125th Ave SESE 170th Pl127th Ave SESE 171st St SE 168th St 128th Ave SESE 169th St SE 169th Pl SE 170th St DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Appendix C Minimum Requirements DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Figure I-3.2: Flow Chart for Determining Requirements for Redevelopment 2019 Stormwater Management Manual for Western Washington Volume I -Chapter 3 -Page 90 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Figure I-3.3: Flow Chart for Determining MR #5 Requirements 2019 Stormwater Management Manual for Western Washington Volume I -Chapter 3 -Page 118 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 List #1 (For MR #1 - #5 Projects That Are Not Flow Control Exempt) List #2 (For MR #1 - #9 Projects That Are Not Flow Control Exempt) List #3 (For Flow Control Exempt Pro- jects) Surface Type: Lawn and Landscaped Areas BMP T5.13: Post-Construction Soil Quality and Depth BMP T5.13: Post-Construction Soil Quality and Depth BMP T5.13: Post-Construction Soil Quality and Depth Surface Type: Roofs 1. BMP T5.30: Full Dis- persion or BMP T5.10A: Downspout Full Infiltration 1. BMP T5.30: Full Dis- persion or BMP T5.10A: Downspout Full Infiltration 1. BMP T5.10A: Downspout Full Infiltration 2. BMP T5.14: Rain Gardens or BMP T7.30: Bioretention 2. BMP T7.30: Bioretention 2. BMP T5.10B: Downspout Dispersion Systems 3. BMP T5.10B: Downspout Dispersion Systems 3. BMP T5.10B: Downspout Dispersion Systems 3. BMP T5.10C: Perforated Stub-out Connections 4. BMP T5.10C: Perforated Stub-out Connections 4. BMP T5.10C: Perforated Stub-out Connections Surface Type: Other Hard Surfaces 1. BMP T5.30: Full Dis- persion 1. BMP T5.30: Full Dis- persion BMP T5.12: Sheet Flow Dis- persion or BMP T5.11: Concentrated Flow Dispersion 2. BMP T5.15: Permeable Pavements or BMP T5.14: Rain Gardens or BMP T7.30: Bioretention 2. BMP T5.15: Permeable Pavements 3. BMP T5.12: Sheet Flow Dispersion or BMP T5.11: Concentrated Flow Dispersion 3. BMP T7.30: Bioretention 4. BMP T5.12: Sheet Flow Dispersion or BMP T5.11: Concentrated Flow Dispersion Notes for using the List Approach: 1. Size BMP T5.14: Rain Gardens and BMP T7.30: Bioretention used in the List Approach to have a minimum horizontal projected surface area below the overflow which is at least 5% of the area drain- Table I-3.2: The List Approach for MR5 Compliance 2019 Stormwater Management Manual for Western Washington Volume I -Chapter 3 -Page 120 Due to lack of separation from Groundwater and site grading constraints, bioretention is infeasible to meet MR 5 requirements. DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Figure I-3.5: Flow Chart for Determining Wetland Protection Level Requirements 2019 Stormwater Management Manual for Western Washington Volume I -Chapter 3 -Page 135 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Appendix D Modeling Results DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Appendix D-1 BMP Sizing – Filterras and Bioretention DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 WWHM2012 PROJECT REPORT FILTERRA F1 and F6 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:35:49 PM Page 2 General Model Information Project Name: Site Name: SE 172nd St and 125th Ave SE GSI Project Site Address: SE 172nd St and 125th Ave SE City: Renton Report Date: 5/17/2021 Gage: Seatac Data Start: 1948/10/01 Data End: 2009/09/30 Timestep: 15 Minute Precip Scale: 1.000 Version Date: 2019/09/13 Version: 4.2.17 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:35:49 PM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Mod 1.73 Pervious Total 1.73 Impervious Land Use acre Impervious Total 0 Basin Total 1.73 Element Flows To: Surface Interflow Groundwater DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:35:49 PM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.8 Pervious Total 0.8 Impervious Land Use acre PARKING FLAT 0.93 Impervious Total 0.93 Basin Total 1.73 Element Flows To: Surface Interflow Groundwater DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:35:49 PM Page 7 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:1.73 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.8 Total Impervious Area:0.93 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.051511 5 year 0.084405 10 year 0.105556 25 year 0.130715 50 year 0.148142 100 year 0.16442 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.40762 5 year 0.5384 10 year 0.630362 25 year 0.752916 50 year 0.848964 100 year 0.949189 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.059 0.575 1950 0.070 0.529 1951 0.113 0.357 1952 0.035 0.264 1953 0.029 0.286 1954 0.044 0.331 1955 0.070 0.364 1956 0.056 0.361 1957 0.046 0.441 1958 0.051 0.323 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:36:26 PM Page 8 1959 0.043 0.301 1960 0.078 0.372 1961 0.043 0.368 1962 0.027 0.289 1963 0.036 0.356 1964 0.052 0.328 1965 0.034 0.463 1966 0.033 0.280 1967 0.079 0.533 1968 0.045 0.562 1969 0.043 0.420 1970 0.035 0.380 1971 0.039 0.454 1972 0.085 0.535 1973 0.038 0.247 1974 0.042 0.431 1975 0.058 0.448 1976 0.042 0.333 1977 0.006 0.316 1978 0.035 0.393 1979 0.021 0.520 1980 0.101 0.613 1981 0.032 0.417 1982 0.065 0.639 1983 0.056 0.454 1984 0.034 0.306 1985 0.020 0.420 1986 0.088 0.360 1987 0.078 0.520 1988 0.031 0.300 1989 0.020 0.375 1990 0.187 0.933 1991 0.099 0.693 1992 0.040 0.303 1993 0.039 0.247 1994 0.013 0.250 1995 0.057 0.365 1996 0.131 0.446 1997 0.101 0.417 1998 0.025 0.370 1999 0.111 0.863 2000 0.039 0.409 2001 0.007 0.400 2002 0.046 0.570 2003 0.068 0.443 2004 0.073 0.796 2005 0.054 0.367 2006 0.061 0.335 2007 0.141 0.838 2008 0.172 0.680 2009 0.080 0.460 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.1865 0.9326 2 0.1719 0.8633 3 0.1410 0.8380 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:36:26 PM Page 9 4 0.1306 0.7956 5 0.1125 0.6926 6 0.1105 0.6796 7 0.1008 0.6388 8 0.1006 0.6131 9 0.0989 0.5753 10 0.0883 0.5696 11 0.0854 0.5619 12 0.0801 0.5347 13 0.0791 0.5334 14 0.0779 0.5288 15 0.0777 0.5200 16 0.0726 0.5196 17 0.0704 0.4629 18 0.0700 0.4605 19 0.0680 0.4541 20 0.0652 0.4541 21 0.0606 0.4479 22 0.0593 0.4461 23 0.0584 0.4428 24 0.0565 0.4414 25 0.0564 0.4307 26 0.0558 0.4198 27 0.0539 0.4195 28 0.0518 0.4172 29 0.0505 0.4166 30 0.0455 0.4089 31 0.0455 0.4004 32 0.0445 0.3932 33 0.0438 0.3801 34 0.0434 0.3753 35 0.0433 0.3723 36 0.0427 0.3702 37 0.0420 0.3677 38 0.0418 0.3667 39 0.0404 0.3645 40 0.0394 0.3635 41 0.0393 0.3611 42 0.0393 0.3605 43 0.0379 0.3569 44 0.0365 0.3561 45 0.0353 0.3348 46 0.0353 0.3326 47 0.0348 0.3314 48 0.0344 0.3278 49 0.0336 0.3228 50 0.0331 0.3157 51 0.0316 0.3058 52 0.0308 0.3032 53 0.0285 0.3009 54 0.0266 0.3001 55 0.0247 0.2886 56 0.0214 0.2856 57 0.0204 0.2797 58 0.0199 0.2641 59 0.0132 0.2504 60 0.0071 0.2475 61 0.0061 0.2466 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:36:26 PM Page 13 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0.1381 acre-feet On-line facility target flow:0.1492 cfs. Adjusted for 15 min:0.1492 cfs. Off-line facility target flow:0.0831 cfs. Adjusted for 15 min:0.0831 cfs. DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:36:51 PM Page 16 Appendix Predeveloped Schematic DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:36:52 PM Page 17 Mitigated Schematic DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 WWHM2012 PROJECT REPORT FILTERRA F2 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:45:42 PM Page 2 General Model Information Project Name: Site Name: SE 172nd St and 125th Ave SE GSI Project Site Address: SE 172nd St and 125th Ave SE City: Renton Report Date: 5/17/2021 Gage: Seatac Data Start: 1948/10/01 Data End: 2009/09/30 Timestep: 15 Minute Precip Scale: 1.000 Version Date: 2019/09/13 Version: 4.2.17 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:45:42 PM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Mod 1.6 Pervious Total 1.6 Impervious Land Use acre Impervious Total 0 Basin Total 1.6 Element Flows To: Surface Interflow Groundwater DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:45:42 PM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.74 Pervious Total 0.74 Impervious Land Use acre PARKING FLAT 0.86 Impervious Total 0.86 Basin Total 1.6 Element Flows To: Surface Interflow Groundwater DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:45:42 PM Page 7 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:1.6 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.74 Total Impervious Area:0.86 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.04764 5 year 0.078063 10 year 0.097624 25 year 0.120893 50 year 0.13701 100 year 0.152065 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.376954 5 year 0.497902 10 year 0.582952 25 year 0.696294 50 year 0.785124 100 year 0.877818 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.055 0.532 1950 0.065 0.489 1951 0.104 0.330 1952 0.033 0.244 1953 0.026 0.264 1954 0.041 0.306 1955 0.065 0.336 1956 0.052 0.334 1957 0.042 0.408 1958 0.047 0.299 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:46:19 PM Page 8 1959 0.040 0.278 1960 0.072 0.344 1961 0.039 0.340 1962 0.025 0.267 1963 0.034 0.329 1964 0.048 0.303 1965 0.032 0.428 1966 0.031 0.259 1967 0.073 0.493 1968 0.041 0.520 1969 0.040 0.388 1970 0.032 0.352 1971 0.036 0.420 1972 0.079 0.495 1973 0.035 0.228 1974 0.039 0.398 1975 0.054 0.414 1976 0.039 0.308 1977 0.006 0.292 1978 0.033 0.364 1979 0.020 0.481 1980 0.093 0.567 1981 0.029 0.385 1982 0.060 0.591 1983 0.052 0.420 1984 0.031 0.283 1985 0.018 0.388 1986 0.082 0.333 1987 0.072 0.481 1988 0.028 0.277 1989 0.019 0.347 1990 0.173 0.863 1991 0.092 0.641 1992 0.037 0.280 1993 0.036 0.229 1994 0.012 0.232 1995 0.052 0.337 1996 0.121 0.413 1997 0.093 0.386 1998 0.023 0.342 1999 0.102 0.798 2000 0.036 0.378 2001 0.007 0.370 2002 0.042 0.527 2003 0.063 0.410 2004 0.067 0.736 2005 0.050 0.339 2006 0.056 0.310 2007 0.130 0.775 2008 0.159 0.628 2009 0.074 0.426 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.1725 0.8625 2 0.1589 0.7984 3 0.1304 0.7750 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:46:19 PM Page 9 4 0.1208 0.7358 5 0.1041 0.6406 6 0.1022 0.6285 7 0.0932 0.5908 8 0.0930 0.5670 9 0.0915 0.5320 10 0.0816 0.5267 11 0.0790 0.5196 12 0.0741 0.4945 13 0.0732 0.4933 14 0.0721 0.4891 15 0.0718 0.4809 16 0.0672 0.4805 17 0.0651 0.4281 18 0.0647 0.4258 19 0.0629 0.4199 20 0.0603 0.4199 21 0.0561 0.4142 22 0.0548 0.4125 23 0.0540 0.4095 24 0.0523 0.4082 25 0.0522 0.3983 26 0.0516 0.3883 27 0.0498 0.3880 28 0.0479 0.3858 29 0.0467 0.3853 30 0.0421 0.3781 31 0.0421 0.3703 32 0.0412 0.3636 33 0.0405 0.3515 34 0.0401 0.3470 35 0.0401 0.3443 36 0.0395 0.3424 37 0.0388 0.3400 38 0.0386 0.3392 39 0.0374 0.3371 40 0.0365 0.3362 41 0.0363 0.3339 42 0.0363 0.3334 43 0.0350 0.3301 44 0.0337 0.3293 45 0.0327 0.3096 46 0.0326 0.3076 47 0.0322 0.3065 48 0.0318 0.3031 49 0.0311 0.2985 50 0.0306 0.2920 51 0.0292 0.2828 52 0.0285 0.2804 53 0.0264 0.2782 54 0.0246 0.2775 55 0.0228 0.2669 56 0.0197 0.2641 57 0.0188 0.2586 58 0.0185 0.2442 59 0.0122 0.2315 60 0.0065 0.2288 61 0.0057 0.2281 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:46:19 PM Page 13 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0.1277 acre-feet On-line facility target flow:0.1379 cfs. Adjusted for 15 min:0.1379 cfs. Off-line facility target flow:0.0769 cfs. Adjusted for 15 min:0.0769 cfs. DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:46:45 PM Page 16 Appendix Predeveloped Schematic DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:46:46 PM Page 17 Mitigated Schematic DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 WWHM2012 PROJECT REPORT FILTERRA F3 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:51:17 PM Page 2 General Model Information Project Name: Site Name: SE 172nd St and 125th Ave SE GSI Project Site Address: SE 172nd St and 125th Ave SE City: Renton Report Date: 5/17/2021 Gage: Seatac Data Start: 1948/10/01 Data End: 2009/09/30 Timestep: 15 Minute Precip Scale: 1.000 Version Date: 2019/09/13 Version: 4.2.17 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:51:17 PM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Mod 1.76 Pervious Total 1.76 Impervious Land Use acre Impervious Total 0 Basin Total 1.76 Element Flows To: Surface Interflow Groundwater DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:51:17 PM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.82 Pervious Total 0.82 Impervious Land Use acre PARKING FLAT 0.94 Impervious Total 0.94 Basin Total 1.76 Element Flows To: Surface Interflow Groundwater DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:51:17 PM Page 7 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:1.76 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.82 Total Impervious Area:0.94 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.052404 5 year 0.085869 10 year 0.107386 25 year 0.132982 50 year 0.150711 100 year 0.167271 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.412804 5 year 0.545628 10 year 0.639077 25 year 0.763665 50 year 0.861344 100 year 0.9633 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.060 0.583 1950 0.072 0.537 1951 0.114 0.362 1952 0.036 0.267 1953 0.029 0.289 1954 0.045 0.336 1955 0.071 0.368 1956 0.057 0.366 1957 0.046 0.447 1958 0.051 0.327 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:51:54 PM Page 8 1959 0.044 0.304 1960 0.079 0.377 1961 0.043 0.372 1962 0.027 0.292 1963 0.037 0.361 1964 0.053 0.332 1965 0.035 0.469 1966 0.034 0.283 1967 0.080 0.541 1968 0.045 0.569 1969 0.044 0.425 1970 0.035 0.385 1971 0.040 0.460 1972 0.087 0.542 1973 0.039 0.249 1974 0.043 0.436 1975 0.059 0.454 1976 0.042 0.337 1977 0.006 0.320 1978 0.036 0.398 1979 0.022 0.525 1980 0.102 0.622 1981 0.032 0.422 1982 0.066 0.648 1983 0.057 0.459 1984 0.034 0.310 1985 0.020 0.425 1986 0.090 0.365 1987 0.079 0.526 1988 0.031 0.303 1989 0.021 0.379 1990 0.190 0.947 1991 0.101 0.703 1992 0.041 0.307 1993 0.040 0.250 1994 0.013 0.253 1995 0.057 0.369 1996 0.133 0.452 1997 0.103 0.423 1998 0.025 0.375 1999 0.112 0.875 2000 0.040 0.414 2001 0.007 0.405 2002 0.046 0.577 2003 0.069 0.449 2004 0.074 0.806 2005 0.055 0.372 2006 0.062 0.339 2007 0.143 0.851 2008 0.175 0.689 2009 0.082 0.465 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.1898 0.9469 2 0.1748 0.8748 3 0.1434 0.8510 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:51:54 PM Page 9 4 0.1329 0.8061 5 0.1145 0.7028 6 0.1125 0.6895 7 0.1026 0.6477 8 0.1023 0.6220 9 0.1007 0.5832 10 0.0898 0.5774 11 0.0869 0.5689 12 0.0815 0.5423 13 0.0805 0.5412 14 0.0793 0.5366 15 0.0790 0.5260 16 0.0739 0.5254 17 0.0716 0.4691 18 0.0712 0.4655 19 0.0692 0.4598 20 0.0664 0.4594 21 0.0617 0.4539 22 0.0603 0.4523 23 0.0594 0.4489 24 0.0575 0.4472 25 0.0574 0.4364 26 0.0568 0.4255 27 0.0548 0.4247 28 0.0526 0.4228 29 0.0514 0.4218 30 0.0463 0.4141 31 0.0463 0.4049 32 0.0453 0.3979 33 0.0446 0.3849 34 0.0441 0.3793 35 0.0441 0.3774 36 0.0434 0.3746 37 0.0427 0.3724 38 0.0425 0.3716 39 0.0411 0.3689 40 0.0401 0.3680 41 0.0399 0.3655 42 0.0399 0.3653 43 0.0385 0.3618 44 0.0371 0.3607 45 0.0359 0.3394 46 0.0359 0.3369 47 0.0354 0.3356 48 0.0350 0.3319 49 0.0342 0.3267 50 0.0336 0.3198 51 0.0321 0.3097 52 0.0313 0.3070 53 0.0290 0.3041 54 0.0270 0.3033 55 0.0251 0.2920 56 0.0217 0.2888 57 0.0207 0.2831 58 0.0203 0.2670 59 0.0135 0.2531 60 0.0072 0.2504 61 0.0062 0.2493 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:51:54 PM Page 13 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0.1401 acre-feet On-line facility target flow:0.1508 cfs. Adjusted for 15 min:0.1508 cfs. Off-line facility target flow:0.084 cfs. Adjusted for 15 min:0.084 cfs. DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:52:21 PM Page 16 Appendix Predeveloped Schematic DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:52:22 PM Page 17 Mitigated Schematic DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 WWHM2012 PROJECT REPORT FILTERRA F4 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:58:44 PM Page 2 General Model Information Project Name: Site Name: SE 172nd St and 125th Ave SE GSI Project Site Address: SE 172nd St and 125th Ave SE City: Renton Report Date: 5/17/2021 Gage: Seatac Data Start: 1948/10/01 Data End: 2009/09/30 Timestep: 15 Minute Precip Scale: 1.000 Version Date: 2019/09/13 Version: 4.2.17 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:58:44 PM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Mod 1.67 Pervious Total 1.67 Impervious Land Use acre Impervious Total 0 Basin Total 1.67 Element Flows To: Surface Interflow Groundwater DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:58:44 PM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.77 Pervious Total 0.77 Impervious Land Use acre PARKING FLAT 0.9 Impervious Total 0.9 Basin Total 1.67 Element Flows To: Surface Interflow Groundwater DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:58:44 PM Page 7 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:1.67 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.77 Total Impervious Area:0.9 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.049725 5 year 0.081478 10 year 0.101895 25 year 0.126182 50 year 0.143004 100 year 0.158718 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.394176 5 year 0.520503 10 year 0.609315 25 year 0.727652 50 year 0.820383 100 year 0.917135 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.057 0.556 1950 0.068 0.511 1951 0.109 0.345 1952 0.034 0.255 1953 0.028 0.276 1954 0.042 0.321 1955 0.068 0.352 1956 0.054 0.349 1957 0.044 0.427 1958 0.049 0.312 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:59:21 PM Page 8 1959 0.042 0.291 1960 0.075 0.360 1961 0.041 0.356 1962 0.026 0.279 1963 0.035 0.344 1964 0.050 0.317 1965 0.033 0.448 1966 0.032 0.271 1967 0.076 0.515 1968 0.043 0.543 1969 0.042 0.406 1970 0.034 0.368 1971 0.038 0.439 1972 0.082 0.517 1973 0.037 0.239 1974 0.041 0.416 1975 0.056 0.433 1976 0.040 0.322 1977 0.006 0.305 1978 0.034 0.380 1979 0.021 0.503 1980 0.097 0.593 1981 0.030 0.403 1982 0.063 0.617 1983 0.054 0.439 1984 0.032 0.296 1985 0.019 0.406 1986 0.085 0.349 1987 0.075 0.503 1988 0.030 0.290 1989 0.020 0.363 1990 0.180 0.901 1991 0.096 0.669 1992 0.039 0.293 1993 0.038 0.239 1994 0.013 0.242 1995 0.055 0.353 1996 0.126 0.431 1997 0.097 0.403 1998 0.024 0.358 1999 0.107 0.835 2000 0.038 0.395 2001 0.007 0.387 2002 0.044 0.551 2003 0.066 0.428 2004 0.070 0.769 2005 0.052 0.355 2006 0.059 0.324 2007 0.136 0.809 2008 0.166 0.657 2009 0.077 0.446 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.1801 0.9010 2 0.1659 0.8346 3 0.1361 0.8095 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:59:21 PM Page 9 4 0.1261 0.7692 5 0.1086 0.6693 6 0.1067 0.6567 7 0.0973 0.6174 8 0.0971 0.5925 9 0.0955 0.5561 10 0.0852 0.5506 11 0.0825 0.5434 12 0.0773 0.5168 13 0.0764 0.5154 14 0.0752 0.5110 15 0.0750 0.5031 16 0.0701 0.5028 17 0.0679 0.4475 18 0.0676 0.4456 19 0.0656 0.4393 20 0.0630 0.4391 21 0.0585 0.4330 22 0.0572 0.4312 23 0.0564 0.4281 24 0.0545 0.4267 25 0.0544 0.4165 26 0.0539 0.4059 27 0.0520 0.4057 28 0.0500 0.4033 29 0.0488 0.4030 30 0.0439 0.3954 31 0.0439 0.3874 32 0.0430 0.3803 33 0.0423 0.3676 34 0.0419 0.3632 35 0.0418 0.3599 36 0.0412 0.3581 37 0.0405 0.3555 38 0.0403 0.3546 39 0.0390 0.3526 40 0.0381 0.3516 41 0.0379 0.3492 42 0.0379 0.3485 43 0.0366 0.3451 44 0.0352 0.3443 45 0.0341 0.3236 46 0.0341 0.3216 47 0.0336 0.3205 48 0.0332 0.3170 49 0.0324 0.3123 50 0.0319 0.3053 51 0.0305 0.2958 52 0.0297 0.2932 53 0.0275 0.2912 54 0.0257 0.2904 55 0.0238 0.2792 56 0.0206 0.2764 57 0.0197 0.2705 58 0.0193 0.2555 59 0.0128 0.2423 60 0.0068 0.2394 61 0.0059 0.2387 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:59:21 PM Page 13 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0.1335 acre-feet On-line facility target flow:0.1444 cfs. Adjusted for 15 min:0.1444 cfs. Off-line facility target flow:0.0804 cfs. Adjusted for 15 min:0.0804 cfs. DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:59:47 PM Page 16 Appendix Predeveloped Schematic DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 1:59:48 PM Page 17 Mitigated Schematic DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 WWHM2012 PROJECT REPORT FILTERRA F5 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:05:41 PM Page 2 General Model Information Project Name: Site Name: SE 172nd St and 125th Ave SE GSI Project Site Address: SE 172nd St and 125th Ave SE City: Renton Report Date: 5/17/2021 Gage: Seatac Data Start: 1948/10/01 Data End: 2009/09/30 Timestep: 15 Minute Precip Scale: 1.000 Version Date: 2019/09/13 Version: 4.2.17 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:05:41 PM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Mod 1.75 Pervious Total 1.75 Impervious Land Use acre Impervious Total 0 Basin Total 1.75 Element Flows To: Surface Interflow Groundwater DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:05:41 PM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.81 Pervious Total 0.81 Impervious Land Use acre PARKING FLAT 0.94 Impervious Total 0.94 Basin Total 1.75 Element Flows To: Surface Interflow Groundwater DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:05:41 PM Page 7 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:1.75 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.81 Total Impervious Area:0.94 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.052107 5 year 0.085381 10 year 0.106776 25 year 0.132226 50 year 0.149855 100 year 0.166321 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.412101 5 year 0.544366 10 year 0.637378 25 year 0.761337 50 year 0.858491 100 year 0.959874 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.060 0.582 1950 0.071 0.535 1951 0.114 0.361 1952 0.036 0.267 1953 0.029 0.289 1954 0.044 0.335 1955 0.071 0.367 1956 0.057 0.365 1957 0.046 0.446 1958 0.051 0.326 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:06:19 PM Page 8 1959 0.044 0.304 1960 0.079 0.376 1961 0.043 0.372 1962 0.027 0.292 1963 0.037 0.360 1964 0.052 0.331 1965 0.035 0.468 1966 0.033 0.283 1967 0.080 0.539 1968 0.045 0.568 1969 0.044 0.424 1970 0.035 0.384 1971 0.040 0.459 1972 0.086 0.541 1973 0.038 0.249 1974 0.042 0.435 1975 0.059 0.453 1976 0.042 0.336 1977 0.006 0.319 1978 0.036 0.397 1979 0.022 0.525 1980 0.102 0.620 1981 0.032 0.421 1982 0.066 0.646 1983 0.056 0.459 1984 0.034 0.309 1985 0.020 0.424 1986 0.089 0.364 1987 0.079 0.526 1988 0.031 0.303 1989 0.021 0.379 1990 0.189 0.943 1991 0.100 0.700 1992 0.041 0.306 1993 0.040 0.250 1994 0.013 0.253 1995 0.057 0.368 1996 0.132 0.451 1997 0.102 0.422 1998 0.025 0.374 1999 0.112 0.873 2000 0.040 0.413 2001 0.007 0.405 2002 0.046 0.576 2003 0.069 0.448 2004 0.073 0.804 2005 0.055 0.371 2006 0.061 0.339 2007 0.143 0.847 2008 0.174 0.687 2009 0.081 0.465 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.1887 0.9432 2 0.1738 0.8729 3 0.1426 0.8475 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:06:19 PM Page 9 4 0.1321 0.8044 5 0.1138 0.7004 6 0.1118 0.6872 7 0.1020 0.6459 8 0.1017 0.6200 9 0.1001 0.5817 10 0.0893 0.5759 11 0.0864 0.5681 12 0.0810 0.5407 13 0.0800 0.5394 14 0.0788 0.5348 15 0.0785 0.5257 16 0.0735 0.5253 17 0.0712 0.4680 18 0.0708 0.4655 19 0.0688 0.4591 20 0.0660 0.4590 21 0.0613 0.4529 22 0.0600 0.4510 23 0.0591 0.4478 24 0.0572 0.4462 25 0.0571 0.4355 26 0.0564 0.4245 27 0.0545 0.4241 28 0.0523 0.4218 29 0.0511 0.4212 30 0.0460 0.4134 31 0.0460 0.4047 32 0.0450 0.3974 33 0.0443 0.3843 34 0.0439 0.3793 35 0.0438 0.3765 36 0.0432 0.3742 37 0.0425 0.3717 38 0.0422 0.3708 39 0.0409 0.3685 40 0.0399 0.3675 41 0.0397 0.3650 42 0.0397 0.3645 43 0.0383 0.3609 44 0.0369 0.3600 45 0.0357 0.3385 46 0.0357 0.3363 47 0.0352 0.3351 48 0.0348 0.3314 49 0.0340 0.3263 50 0.0334 0.3192 51 0.0319 0.3092 52 0.0311 0.3065 53 0.0289 0.3041 54 0.0269 0.3033 55 0.0250 0.2918 56 0.0216 0.2887 57 0.0206 0.2827 58 0.0202 0.2669 59 0.0134 0.2531 60 0.0071 0.2501 61 0.0062 0.2493 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:06:19 PM Page 13 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0.1397 acre-feet On-line facility target flow:0.1507 cfs. Adjusted for 15 min:0.1507 cfs. Off-line facility target flow:0.084 cfs. Adjusted for 15 min:0.084 cfs. DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:06:45 PM Page 16 Appendix Predeveloped Schematic DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:06:46 PM Page 17 Mitigated Schematic DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 WWHM2012 PROJECT REPORT FILTERRA F7 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:11:53 PM Page 2 General Model Information Project Name: Site Name: SE 172nd St and 125th Ave SE GSI Project Site Address: SE 172nd St and 125th Ave SE City: Renton Report Date: 5/17/2021 Gage: Seatac Data Start: 1948/10/01 Data End: 2009/09/30 Timestep: 15 Minute Precip Scale: 1.000 Version Date: 2019/09/13 Version: 4.2.17 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:11:53 PM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Mod 1.43 Pervious Total 1.43 Impervious Land Use acre Impervious Total 0 Basin Total 1.43 Element Flows To: Surface Interflow Groundwater DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:11:53 PM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.64 Pervious Total 0.64 Impervious Land Use acre PARKING FLAT 0.79 Impervious Total 0.79 Basin Total 1.43 Element Flows To: Surface Interflow Groundwater DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:11:53 PM Page 7 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:1.43 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.64 Total Impervious Area:0.79 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.042578 5 year 0.069769 10 year 0.087251 25 year 0.108048 50 year 0.122453 100 year 0.135908 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.343471 5 year 0.452359 10 year 0.528758 25 year 0.630392 50 year 0.709924 100 year 0.792815 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.049 0.483 1950 0.058 0.442 1951 0.093 0.300 1952 0.029 0.224 1953 0.024 0.242 1954 0.036 0.279 1955 0.058 0.307 1956 0.047 0.305 1957 0.038 0.371 1958 0.042 0.273 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:12:30 PM Page 8 1959 0.036 0.256 1960 0.064 0.312 1961 0.035 0.310 1962 0.022 0.244 1963 0.030 0.300 1964 0.043 0.276 1965 0.028 0.389 1966 0.027 0.236 1967 0.065 0.446 1968 0.037 0.474 1969 0.036 0.353 1970 0.029 0.320 1971 0.032 0.383 1972 0.071 0.448 1973 0.031 0.209 1974 0.035 0.362 1975 0.048 0.376 1976 0.035 0.280 1977 0.005 0.266 1978 0.029 0.332 1979 0.018 0.441 1980 0.083 0.513 1981 0.026 0.352 1982 0.054 0.536 1983 0.046 0.384 1984 0.028 0.258 1985 0.016 0.354 1986 0.073 0.303 1987 0.064 0.440 1988 0.025 0.255 1989 0.017 0.319 1990 0.154 0.777 1991 0.082 0.579 1992 0.033 0.256 1993 0.033 0.209 1994 0.011 0.213 1995 0.047 0.308 1996 0.108 0.374 1997 0.083 0.351 1998 0.020 0.313 1999 0.091 0.725 2000 0.032 0.344 2001 0.006 0.339 2002 0.038 0.478 2003 0.056 0.372 2004 0.060 0.669 2005 0.045 0.308 2006 0.050 0.281 2007 0.117 0.698 2008 0.142 0.568 2009 0.066 0.391 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.1542 0.7773 2 0.1421 0.7255 3 0.1165 0.6980 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:12:30 PM Page 9 4 0.1080 0.6691 5 0.0930 0.5791 6 0.0914 0.5682 7 0.0833 0.5356 8 0.0831 0.5129 9 0.0818 0.4830 10 0.0730 0.4779 11 0.0706 0.4739 12 0.0662 0.4479 13 0.0654 0.4457 14 0.0644 0.4419 15 0.0642 0.4407 16 0.0600 0.4405 17 0.0582 0.3911 18 0.0579 0.3889 19 0.0562 0.3843 20 0.0539 0.3828 21 0.0501 0.3764 22 0.0490 0.3742 23 0.0483 0.3715 24 0.0467 0.3711 25 0.0466 0.3624 26 0.0461 0.3539 27 0.0445 0.3528 28 0.0428 0.3516 29 0.0418 0.3505 30 0.0376 0.3445 31 0.0376 0.3394 32 0.0368 0.3323 33 0.0362 0.3204 34 0.0358 0.3188 35 0.0358 0.3132 36 0.0353 0.3125 37 0.0347 0.3095 38 0.0345 0.3083 39 0.0334 0.3079 40 0.0326 0.3070 41 0.0325 0.3048 42 0.0325 0.3029 43 0.0313 0.2998 44 0.0302 0.2997 45 0.0292 0.2810 46 0.0292 0.2798 47 0.0288 0.2794 48 0.0284 0.2764 49 0.0278 0.2728 50 0.0273 0.2659 51 0.0261 0.2579 52 0.0254 0.2557 53 0.0236 0.2556 54 0.0220 0.2549 55 0.0204 0.2443 56 0.0177 0.2421 57 0.0168 0.2362 58 0.0165 0.2239 59 0.0109 0.2127 60 0.0058 0.2095 61 0.0051 0.2093 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:12:30 PM Page 13 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0.1162 acre-feet On-line facility target flow:0.1265 cfs. Adjusted for 15 min:0.1265 cfs. Off-line facility target flow:0.0706 cfs. Adjusted for 15 min:0.0706 cfs. DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:12:56 PM Page 16 Appendix Predeveloped Schematic DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:12:57 PM Page 17 Mitigated Schematic DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 WWHM2012 PROJECT REPORT FILTERRA F8 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:18:29 PM Page 2 General Model Information Project Name: Site Name: SE 172nd St and 125th Ave SE GSI Project Site Address: SE 172nd St and 125th Ave SE City: Renton Report Date: 5/17/2021 Gage: Seatac Data Start: 1948/10/01 Data End: 2009/09/30 Timestep: 15 Minute Precip Scale: 1.000 Version Date: 2019/09/13 Version: 4.2.17 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:18:29 PM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Mod 1.6 Pervious Total 1.6 Impervious Land Use acre Impervious Total 0 Basin Total 1.6 Element Flows To: Surface Interflow Groundwater DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:18:29 PM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.64 Pervious Total 0.64 Impervious Land Use acre PARKING FLAT 0.96 Impervious Total 0.96 Basin Total 1.6 Element Flows To: Surface Interflow Groundwater DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:18:29 PM Page 7 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:1.6 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.64 Total Impervious Area:0.96 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.04764 5 year 0.078063 10 year 0.097624 25 year 0.120893 50 year 0.13701 100 year 0.152065 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.407806 5 year 0.532787 10 year 0.619936 25 year 0.735309 50 year 0.825208 100 year 0.918591 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.055 0.567 1950 0.065 0.527 1951 0.104 0.352 1952 0.033 0.271 1953 0.026 0.293 1954 0.041 0.332 1955 0.065 0.367 1956 0.052 0.364 1957 0.042 0.438 1958 0.047 0.327 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:19:07 PM Page 8 1959 0.040 0.310 1960 0.072 0.366 1961 0.039 0.367 1962 0.025 0.294 1963 0.034 0.355 1964 0.048 0.329 1965 0.032 0.458 1966 0.031 0.282 1967 0.073 0.516 1968 0.041 0.564 1969 0.040 0.415 1970 0.032 0.381 1971 0.036 0.455 1972 0.079 0.522 1973 0.035 0.254 1974 0.039 0.428 1975 0.054 0.443 1976 0.039 0.331 1977 0.006 0.315 1978 0.033 0.398 1979 0.020 0.533 1980 0.093 0.596 1981 0.029 0.419 1982 0.060 0.627 1983 0.052 0.462 1984 0.031 0.307 1985 0.018 0.421 1986 0.082 0.357 1987 0.072 0.531 1988 0.028 0.310 1989 0.019 0.387 1990 0.173 0.893 1991 0.092 0.671 1992 0.037 0.304 1993 0.036 0.251 1994 0.012 0.258 1995 0.052 0.368 1996 0.121 0.438 1997 0.093 0.413 1998 0.023 0.376 1999 0.102 0.854 2000 0.036 0.409 2001 0.007 0.410 2002 0.042 0.560 2003 0.063 0.435 2004 0.067 0.790 2005 0.050 0.363 2006 0.056 0.330 2007 0.130 0.800 2008 0.159 0.659 2009 0.074 0.475 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.1725 0.8929 2 0.1589 0.8542 3 0.1304 0.8000 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:19:07 PM Page 9 4 0.1208 0.7895 5 0.1041 0.6713 6 0.1022 0.6588 7 0.0932 0.6266 8 0.0930 0.5957 9 0.0915 0.5669 10 0.0816 0.5639 11 0.0790 0.5600 12 0.0741 0.5330 13 0.0732 0.5308 14 0.0721 0.5271 15 0.0718 0.5222 16 0.0672 0.5158 17 0.0651 0.4748 18 0.0647 0.4620 19 0.0629 0.4576 20 0.0603 0.4548 21 0.0561 0.4431 22 0.0548 0.4381 23 0.0540 0.4378 24 0.0523 0.4353 25 0.0522 0.4281 26 0.0516 0.4215 27 0.0498 0.4194 28 0.0479 0.4154 29 0.0467 0.4126 30 0.0421 0.4098 31 0.0421 0.4085 32 0.0412 0.3982 33 0.0405 0.3874 34 0.0401 0.3808 35 0.0401 0.3761 36 0.0395 0.3679 37 0.0388 0.3668 38 0.0386 0.3665 39 0.0374 0.3663 40 0.0365 0.3636 41 0.0363 0.3633 42 0.0363 0.3566 43 0.0350 0.3549 44 0.0337 0.3522 45 0.0327 0.3321 46 0.0326 0.3307 47 0.0322 0.3296 48 0.0318 0.3290 49 0.0311 0.3267 50 0.0306 0.3151 51 0.0292 0.3105 52 0.0285 0.3097 53 0.0264 0.3070 54 0.0246 0.3042 55 0.0228 0.2940 56 0.0197 0.2925 57 0.0188 0.2821 58 0.0185 0.2705 59 0.0122 0.2584 60 0.0065 0.2545 61 0.0057 0.2514 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:19:07 PM Page 13 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0.1368 acre-feet On-line facility target flow:0.1533 cfs. Adjusted for 15 min:0.1533 cfs. Off-line facility target flow:0.0858 cfs. Adjusted for 15 min:0.0858 cfs. DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:19:33 PM Page 16 Appendix Predeveloped Schematic DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:19:34 PM Page 17 Mitigated Schematic DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 WWHM2012 PROJECT REPORT FILTERRA F9 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:24:41 PM Page 2 General Model Information Project Name: Site Name: SE 172nd St and 125th Ave SE GSI Project Site Address: SE 172nd St and 125th Ave SE City: Renton Report Date: 5/17/2021 Gage: Seatac Data Start: 1948/10/01 Data End: 2009/09/30 Timestep: 15 Minute Precip Scale: 1.000 Version Date: 2019/09/13 Version: 4.2.17 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:24:41 PM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Mod 1.4 Pervious Total 1.4 Impervious Land Use acre Impervious Total 0 Basin Total 1.4 Element Flows To: Surface Interflow Groundwater DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:24:41 PM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.55 Pervious Total 0.55 Impervious Land Use acre PARKING FLAT 0.85 Impervious Total 0.85 Basin Total 1.4 Element Flows To: Surface Interflow Groundwater DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:24:41 PM Page 7 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:1.4 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.55 Total Impervious Area:0.85 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.041685 5 year 0.068305 10 year 0.085421 25 year 0.105781 50 year 0.119884 100 year 0.133057 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.359923 5 year 0.469718 10 year 0.546215 25 year 0.647419 50 year 0.726232 100 year 0.808063 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.048 0.500 1950 0.057 0.466 1951 0.091 0.310 1952 0.029 0.239 1953 0.023 0.259 1954 0.035 0.293 1955 0.057 0.324 1956 0.046 0.321 1957 0.037 0.386 1958 0.041 0.289 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:25:18 PM Page 8 1959 0.035 0.275 1960 0.063 0.323 1961 0.035 0.323 1962 0.022 0.260 1963 0.030 0.313 1964 0.042 0.290 1965 0.028 0.403 1966 0.027 0.249 1967 0.064 0.454 1968 0.036 0.498 1969 0.035 0.366 1970 0.028 0.336 1971 0.032 0.401 1972 0.069 0.460 1973 0.031 0.225 1974 0.034 0.378 1975 0.047 0.391 1976 0.034 0.292 1977 0.005 0.278 1978 0.029 0.352 1979 0.017 0.472 1980 0.081 0.524 1981 0.026 0.370 1982 0.053 0.552 1983 0.045 0.408 1984 0.027 0.271 1985 0.016 0.372 1986 0.071 0.314 1987 0.063 0.469 1988 0.025 0.274 1989 0.016 0.343 1990 0.151 0.784 1991 0.080 0.591 1992 0.033 0.269 1993 0.032 0.222 1994 0.011 0.229 1995 0.046 0.325 1996 0.106 0.386 1997 0.082 0.364 1998 0.020 0.332 1999 0.089 0.753 2000 0.032 0.360 2001 0.006 0.362 2002 0.037 0.493 2003 0.055 0.384 2004 0.059 0.696 2005 0.044 0.320 2006 0.049 0.290 2007 0.114 0.703 2008 0.139 0.580 2009 0.065 0.420 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.1509 0.7843 2 0.1391 0.7530 3 0.1141 0.7025 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:25:18 PM Page 9 4 0.1057 0.6962 5 0.0911 0.5905 6 0.0895 0.5795 7 0.0816 0.5518 8 0.0814 0.5241 9 0.0801 0.4995 10 0.0714 0.4978 11 0.0691 0.4933 12 0.0648 0.4716 13 0.0640 0.4695 14 0.0631 0.4663 15 0.0628 0.4597 16 0.0588 0.4536 17 0.0569 0.4204 18 0.0567 0.4085 19 0.0550 0.4034 20 0.0528 0.4014 21 0.0491 0.3906 22 0.0480 0.3861 23 0.0473 0.3859 24 0.0457 0.3835 25 0.0456 0.3775 26 0.0452 0.3722 27 0.0436 0.3704 28 0.0419 0.3662 29 0.0409 0.3637 30 0.0368 0.3625 31 0.0368 0.3605 32 0.0360 0.3518 33 0.0355 0.3430 34 0.0351 0.3361 35 0.0351 0.3325 36 0.0346 0.3250 37 0.0340 0.3240 38 0.0338 0.3234 39 0.0327 0.3227 40 0.0319 0.3211 41 0.0318 0.3203 42 0.0318 0.3144 43 0.0306 0.3131 44 0.0295 0.3104 45 0.0286 0.2932 46 0.0285 0.2917 47 0.0281 0.2905 48 0.0278 0.2904 49 0.0272 0.2886 50 0.0267 0.2781 51 0.0256 0.2749 52 0.0249 0.2742 53 0.0231 0.2710 54 0.0215 0.2686 55 0.0200 0.2600 56 0.0173 0.2588 57 0.0165 0.2492 58 0.0161 0.2393 59 0.0107 0.2288 60 0.0057 0.2253 61 0.0050 0.2222 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:25:19 PM Page 13 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0.1209 acre-feet On-line facility target flow:0.1357 cfs. Adjusted for 15 min:0.1357 cfs. Off-line facility target flow:0.076 cfs. Adjusted for 15 min:0.076 cfs. DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:25:45 PM Page 16 Appendix Predeveloped Schematic DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/17/2021 2:25:46 PM Page 17 Mitigated Schematic DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 WWHM2012 PROJECT REPORT FILTERRA F10 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/18/2021 2:54:24 PM Page 2 General Model Information Project Name: Site Name: SE 172nd St and 125th Ave SE GSI Project Site Address: SE 172nd St and 125th Ave SE City: Renton Report Date: 5/18/2021 Gage: Seatac Data Start: 1948/10/01 Data End: 2009/09/30 Timestep: 15 Minute Precip Scale: 1.000 Version Date: 2019/09/13 Version: 4.2.17 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/18/2021 2:54:24 PM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Mod 0.49 Pervious Total 0.49 Impervious Land Use acre Impervious Total 0 Basin Total 0.49 Element Flows To: Surface Interflow Groundwater DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/18/2021 2:54:24 PM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre A B, Pasture, Flat 0.22 Pervious Total 0.22 Impervious Land Use acre ROADS FLAT 0.27 Impervious Total 0.27 Basin Total 0.49 Element Flows To: Surface Interflow Groundwater DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/18/2021 2:54:24 PM Page 7 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.49 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.22 Total Impervious Area:0.27 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.01459 5 year 0.023907 10 year 0.029897 25 year 0.037023 50 year 0.041959 100 year 0.04657 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.103007 5 year 0.13008 10 year 0.148471 25 year 0.172323 50 year 0.190576 100 year 0.209271 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.017 0.133 1950 0.020 0.144 1951 0.032 0.084 1952 0.010 0.074 1953 0.008 0.080 1954 0.012 0.084 1955 0.020 0.095 1956 0.016 0.093 1957 0.013 0.106 1958 0.014 0.085 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/18/2021 2:55:00 PM Page 8 1959 0.012 0.087 1960 0.022 0.086 1961 0.012 0.091 1962 0.008 0.079 1963 0.010 0.088 1964 0.015 0.086 1965 0.010 0.109 1966 0.009 0.073 1967 0.022 0.126 1968 0.013 0.143 1969 0.012 0.099 1970 0.010 0.096 1971 0.011 0.114 1972 0.024 0.118 1973 0.011 0.072 1974 0.012 0.104 1975 0.017 0.120 1976 0.012 0.081 1977 0.002 0.088 1978 0.010 0.107 1979 0.006 0.147 1980 0.028 0.132 1981 0.009 0.108 1982 0.018 0.152 1983 0.016 0.123 1984 0.010 0.078 1985 0.006 0.107 1986 0.025 0.093 1987 0.022 0.144 1988 0.009 0.087 1989 0.006 0.109 1990 0.053 0.184 1991 0.028 0.147 1992 0.011 0.077 1993 0.011 0.067 1994 0.004 0.073 1995 0.016 0.095 1996 0.037 0.102 1997 0.029 0.099 1998 0.007 0.100 1999 0.031 0.204 2000 0.011 0.102 2001 0.002 0.112 2002 0.013 0.130 2003 0.019 0.101 2004 0.021 0.191 2005 0.015 0.088 2006 0.017 0.077 2007 0.040 0.179 2008 0.049 0.144 2009 0.023 0.133 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.0528 0.2044 2 0.0487 0.1913 3 0.0399 0.1837 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/18/2021 2:55:00 PM Page 9 4 0.0370 0.1788 5 0.0319 0.1517 6 0.0313 0.1467 7 0.0286 0.1466 8 0.0285 0.1441 9 0.0280 0.1440 10 0.0250 0.1436 11 0.0242 0.1430 12 0.0227 0.1333 13 0.0224 0.1331 14 0.0221 0.1316 15 0.0220 0.1304 16 0.0206 0.1258 17 0.0199 0.1235 18 0.0198 0.1202 19 0.0193 0.1183 20 0.0185 0.1144 21 0.0172 0.1120 22 0.0168 0.1091 23 0.0165 0.1090 24 0.0160 0.1076 25 0.0160 0.1075 26 0.0158 0.1071 27 0.0153 0.1060 28 0.0147 0.1043 29 0.0143 0.1017 30 0.0129 0.1017 31 0.0129 0.1013 32 0.0126 0.0999 33 0.0124 0.0994 34 0.0123 0.0987 35 0.0123 0.0959 36 0.0121 0.0954 37 0.0119 0.0949 38 0.0118 0.0934 39 0.0114 0.0932 40 0.0112 0.0907 41 0.0111 0.0876 42 0.0111 0.0876 43 0.0107 0.0876 44 0.0103 0.0872 45 0.0100 0.0871 46 0.0100 0.0860 47 0.0099 0.0856 48 0.0097 0.0855 49 0.0095 0.0840 50 0.0094 0.0837 51 0.0089 0.0808 52 0.0087 0.0801 53 0.0081 0.0790 54 0.0075 0.0779 55 0.0070 0.0773 56 0.0060 0.0771 57 0.0058 0.0741 58 0.0057 0.0730 59 0.0037 0.0727 60 0.0020 0.0717 61 0.0017 0.0669 DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/18/2021 2:55:00 PM Page 13 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0.0332 acre-feet On-line facility target flow:0.0439 cfs. Adjusted for 15 min:0.0439 cfs. Off-line facility target flow:0.0248 cfs. Adjusted for 15 min:0.0248 cfs. DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/18/2021 2:55:26 PM Page 16 Appendix Predeveloped Schematic DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 default[9]5/18/2021 2:55:27 PM Page 17 Mitigated Schematic DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Appendix D-2 PCSWMM – Backwater Analysis DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Inflow from 122nd Ave SE 1.70 cfs Inflow from 123rd Ave SE 1.66 cfs Inflow from 124th Ave SE 1.68 cfs Inflow from 125th Ave 1.47 cfs Inflow from Cascade Shopping Center offsite area 10.87 cfs Inflow from 126th PL SE offsite area 12.55 cfs Inflow from east portion of SE 172nd St 4.43 cfs DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 SE 172nd STProposed 25yr - SE 172nd STDocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 122nd AVE SEProposed 25yr - 122nd AVE SEDocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 123rd AVE SEProposed 25yr - 123rd AVE SEDocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 124th AVE SEProposed 25yr - 124th AVE SEDocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 125th AVE SEProposed 25yr - 125th AVE SEDocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 172nd North172nd South EXISTING CONDITIONS - BACKWATER ANALYSISFloodingLocation (Typ.)SE 172nd SE SE 172nd SE (at wetland outfall) DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 WWHM 25-yr Event Peak Flow Analysis 122nd AVE SE 123rd AVE SE 124th AVE SE 125th AVE SE 127th AVE SE West Part of SE 172nd St DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Location for inflow Offsite Area(Parcel) (ac)Offsite Area (Roadway) (ac)Effective Offsite Contributing IMP Area1(ac)Effective Offsite Contributing Pervious Area(ac)WWHM 25yr Peak Flow (cfs)WWHM 100yr Peak Flow (cfs)Cascade Shopping Center Offsite 31.73 3.338 25.6511.36 10.87 -122nd Ave SE 3.25 0.781 2.501.60 1.7013.48123rd Ave SE 3.17 0.759 2.341.59 1.662.04124th Ave SE 3.22 0.768 2.381.61 1.682.08125th Ave SE 2.35 0.921 2.091.17 1.471.82127th Ave SE North 33.18 - 16.5916.59 12.5515.77127th Ave SE South 12.03 - 6.026.02 4.435.54Notes:1. Assume 50% impervious and 50% pervious for offsite parcel areas. Effective Offsite Contributingt IMP area = 50% of Offsite Parcel Area + 100% Offiste Roadways2. Due to distance and area size, offsite area A, F, and G assume 50% impervious and 50% pervious3. Offsite Roadway areas estiamted using GIS, Area = length * width of Roadway4. Assume Predeveloped Land Use = Forest A/B, Mitigated Pervious Land Use = A/B, Pasture, Flat. Mitigated Impervious Land Use = Road/Flat. Soil type based on Web Soil Survey 1/24/20195. Manning's n used in SWMM model for concrete pipes is 0.012 (Backwater Flow - Capacity verification) per 2017 Renton SWDM Table 4.2.1.D7. Per SWMM model, CB invert elevation is eqaul the the outfall pipe invert. If inflow pipe invert elevation is different from the outfall pipe invert, an offset value is applied to the pipe inlet. City of Renton 172nd St and 125th Ave GSI 90% Proposed Backwater Analysis6. Per City of Renton Surface Water Design Manual (2017),i. New pipe systems shall be designed with sufficient capacity to convey and contain (at minimum) the 25-year peak flow, assuming developed conditions for onsite tributary areas and existing conditions for any offsite tributary areas.ii. Pipe system structures may overtop for runoff events that exceed the 25-year design capacity, provided the overflow from a 100-year runoff event does not create or aggravate a severe flooding problem or severe erosion problem as described in Core Requirement #2, Section 1.2.2. Any overflow occurring onsite for runoff events up to and including the 100-year event must discharge at the natural location for the project site. In residential subdivisions, this overflow must be contained within an onsite drainage easement, tract, covenant, or public right-of-way.iii. The upstream end of a pipe system that receives runoff from an open drainage feature (pond, ditch, etc.) shall be analyzed and sized as a culvert as described belowDocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Appendix E Preliminary Opinion of Probable Cost DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 OPINION OF PROBABLE COSTProject Name:City of Renton 172nd St and 125th Ave GSIProject ID:10-190002Project Phase:90% DesignDate: Jun-2021ITEM DIV ITEM DESCRIPTION UNIT QTY UNIT PRICE COSTA1 1-04 MINOR CHANGEEST 1 50,000$ $50,000A2 1-04 REMOVAL AND REPLACEMENT OF UNSUITABLE FOUNDATION EXCAVATION TN 170 30$ $5,100A3 1-04 SIDE SEWER REPLACEMENT LF 50 85$ $4,250A4 1-07 RESOLUTION OF UTILITY CONFLICT EST 1 25,000$ $25,000A5 1-07 UTILITY POTHOLINGEA 15 2,000$ $30,000A6 1-07 SPCC PLANLS 1 250$ $250A7 1-09 MOBILIZATION AND DEMOBILIZATION (MAX. BID 10% OF SCHEDULE TOTAL) LS 1 253,200$ $253,200A8 1-09 CONSTRUCTION SURVEYING, STAKING AND AS-BUILT DRAWINGS LS 1 32,000$ $32,000A9 1-09 TRENCH SAFETY SYSTEMSLS 1 82,000$ $82,000A10 1-10 TEMPORARY TRAFFIC CONTROL LS 1 126,600$ $126,600A11 2-01 CLEARING, GRUBBING AND ROADSIDE CLEANUP LS 1 5,300$ $5,300A12 2-01 TREE REMOVAL EA 1 8,000$ $8,000A13 2-02 REMOVAL OF STRUCTURES AND OBSTRUCTIONS LS 1 20,000$ $20,000A14 6-08 SAWCUTTINGLF 12100 2$ $24,200A15 2-09 STRUCTURE EXCAVATION CLASS B INCL. HAUL CY5900 30$ $177,000A16 2-09 CONTROLLED DENSITY FILL CY 175 145$ $25,423A17 4-04CRUSHED SURFACING TOP COURSETN 1780 45$ $80,100A18 5-04 HMA CL 1/2 IN PG 64-22TN 1770 110$ $194,700A19 5-04 PLANING BITUMINOUS PAVEMENT SY2183 12$ $26,611A20 5-04THICKENED EDGELF 1000 15$ $15,000A21 7-04 SCHEDULE A STORM SEWER PIPE 12 IN. DIAM. LF 1531 65$ $99,515A22 7-04 SCHEDULE A STORM SEWER PIPE 18 IN. DIAM. LF 3520 85$ $299,200A23 7-04 D.I. STORM SEWER PIPE 12 IN. DIAM. LF 1273 95$ $120,935A24 7-04 D.I. STORM SEWER PIPE 18 IN. DIAM. LF 18 130$ $2,340A25 7-04 D.I. STORM SEWER PIPE 24 IN. DIAM. LF 177 145$ $25,665A26 7-04GRAVEL BORROW FOR TRENCH BACKFILL - STORMTN 3400 30$ $102,000A27 7-05 CATCH BASIN TYPE 1EA 25 1,800$ $45,000A28 7-05 CATCH BASIN TYPE 2 - 48 IN. DIAM. EA 68 3,500$ $238,000A29 7-05 FILTERRA (4 X 4 UNIT)EA 1 23,000$ $23,000A30 7-05 FILTERRA (4 X 6 UNIT)EA 9 29,500$ $265,500A31 7-04 PLUG EXISTING PIPEEA 11 300$ $3,300A32 7-14 MOVING EXISTING HYDRANTS EA 7 8,000$ $56,000A33 8-01 SWPPP AND TESC PLAN AND IMPLEMENTATION LS 1 79,800$ $79,800A34 8-02 PROPERTY RESTORATIONEST 1 10,000$ $10,000A35 8-02 ROADSIDE RESTORATIONLS 1 23,000$ $23,000A36 8-02 PSIPE, CERCIDIPHYLLUM JAPONICUM (KATSURA), 2" CAL EA 4 1,000$ $4,000A37 8-02 PSIPE, STYRAX JAPONICUS (JAPANESE SNOWBELL), 2" CAL EA 3 1,000$ $3,000A38 8-02 PSIPE, CARPINUS BETULUS 'FASTIGATA' (EUROPEAN HORNBEAM), 2" CAL EA 2 1,000$ $2,000A39 8-06 CEMENT CONC. DRIVEWAY ENTRANCE SY 1000 60$ $60,000A40 8-04CEMENT CONC. TRAFFIC CURB AND GUTTERLF 4400 30$ $132,000A41 8-04CEMENT CONC. TRAFFIC CURBLF 50 70$ $3,500A42 8-12 CHAIN LINK FENCE TYPE 3LF 171 50$ $8,550A43 8-12 CHAIN LINK FENCE TYPE 4LF 269 40$ $10,760A44 8-12CHAIN LINK GATEEA 1 1,200$ $1,200A45 8-12WOOD FENCELF 53 100$ $5,300A46 8-14 PERVIOUS CEMENT CONC. SIDEWALK SY 1490 85$ $126,650A47 8-14 CEMENT CONC. CURB RAMP TYPE PERPENDICULAR A EA 7 2,400$ $16,800A48 8-14 CEMENT CONC. CURB RAMP TYPE PERPENDICULAR B EA 3 2,400$ $7,200A49 8-18 RELOCATE MAILBOXEA 26 50$ $1,300A50 8-19 ADJUST FRANCHISE UTILITY APPURTENANCES EA 31 800$ $24,800A51 8-21 PERMANENT SIGNINGLS 1 3,000$ $3,000A52 8-22 PLASTIC CROSSWALK LINESF 400 7$ $2,800A53 8-22PAINT LINELF 60 5$ $300Total Line Item Cost $2,991,149TAX 0.0% -$ Total Construction Cost 2,991,149$ Contingency 10% 299,115$ TOTAL COST WITH CONTINGENCY 3,290,300$ City of Renton 172nd St and 125th Ave GSISUMMARYPrinted: 6/10/2021Page 1/1DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 OPINION OF PROBABLE COST - ECOLOGY ELIGIBLE ITEMSProject Name:City of Renton 172nd St and 125th Ave GSIProject ID:10-190002Project Phase:90% DesignDate: Jun-2021ITEM DIV ITEM DESCRIPTION UNIT QTY UNIT PRICE COST COMMENTSA1 1-04 MINOR CHANGEEST 1 50,000$ $50,000 Required by water quality and pipe improvementsA2 1-04 REMOVAL AND REPLACEMENT OF UNSUITABLE FOUNDATION EXCAVATION TN 170 30$ $5,100 Required by water quality and pipe improvementsA3 1-04 SIDE SEWER REPLACEMENTLF 50 85$ $4,250 Required by water quality and pipe improvementsA4 1-07 RESOLUTION OF UTILITY CONFLICT EST 1 25,000$ $25,000 Required by water quality and pipe improvementsA5 1-07 UTILITY POTHOLINGEA 15 2,000$ $30,000 Required by water quality and pipe improvementsA6 1-07 SPCC PLANLS 1 250$ $250 Required by water quality and pipe improvementsA7 1-09 MOBILIZATION AND DEMOBILIZATION (MAX. BID 10% OF SCHEDULE TOTAL) LS 1 240,100$ $240,100 Adjusted to only Ecology eligible costsA8 1-09 CONSTRUCTION SURVEYING, STAKING AND AS-BUILT DRAWINGS LS 1 32,000$ $32,000 Required by water quality and pipe improvementsA9 1-09 TRENCH SAFETY SYSTEMSLS 1 82,000$ $82,000 Required by water quality and pipe improvementsA10 1-10 TEMPORARY TRAFFIC CONTROL LS 1 126,600$ $126,600 Required by water quality and pipe improvementsA11 2-01 CLEARING, GRUBBING AND ROADSIDE CLEANUP LS 0 -$ $0 Impacts related to new sidewalksA12 2-01 TREE REMOVAL EA 0 -$ $0 Impacts related to new sidewalksA13 2-02 REMOVAL OF STRUCTURES AND OBSTRUCTIONS LS 1 20,000$ $20,000 Required by water quality and pipe improvementsA14 6-08 SAWCUTTINGLF 12100 2$ $24,200 Required by water quality and pipe improvementsA15 2-09 STRUCTURE EXCAVATION CLASS B INCL. HAUL CY5900 30$ $177,000 Required by water quality and pipe improvementsA16 2-09 CONTROLLED DENSITY FILLCY 175 145$ $25,423 Required by water quality and pipe improvementsA17 4-04CRUSHED SURFACING TOP COURSETN 1780 45$ $80,100 Required by water quality and pipe improvementsA18 5-04 HMA CL 1/2 IN PG 64-22TN 1770 110$ $194,700 Required by water quality and pipe improvementsA19 5-04 PLANING BITUMINOUS PAVEMENT SY2183 12$ $26,611 Required by water quality and pipe improvementsA20 5-04THICKENED EDGELF 1000 15$ $15,000 Required by water quality and pipe improvementsA21 7-04 SCHEDULE A STORM SEWER PIPE 12 IN. DIAM. LF 1531 65$ $99,515 Required by water quality and pipe improvementsA22 7-04 SCHEDULE A STORM SEWER PIPE 18 IN. DIAM. LF 3520 85$ $299,200 Required by water quality and pipe improvementsA23 7-04 D.I. STORM SEWER PIPE 12 IN. DIAM. LF1273 95$ $120,935 Required by water quality and pipe improvementsA24 7-04 D.I. STORM SEWER PIPE 18 IN. DIAM. LF 18 130$ $2,340 Required by water quality and pipe improvementsA25 7-04 D.I. STORM SEWER PIPE 24 IN. DIAM. LF 177 145$ $25,665 Required by water quality and pipe improvementsA26 7-04GRAVEL BORROW FOR TRENCH BACKFILL - STORMTN 3400 30$ $102,000 Required by water quality and pipe improvementsA27 7-05 CATCH BASIN TYPE 1EA 25 1,800$ $45,000 Required by water quality and pipe improvementsA28 7-05 CATCH BASIN TYPE 2 - 48 IN. DIAM. EA 68 3,500$ $238,000 Required by water quality and pipe improvementsA29 7-05 FILTERRA (4 X 4 UNIT)EA 1 23,000$ $23,000 Required by water quality and pipe improvementsA30 7-05 FILTERRA (4 X 6 UNIT)EA 9 29,500$ $265,500 Required by water quality and pipe improvementsA31 7-04 PLUG EXISTING PIPEEA 11 300$ $3,300 Required by water quality and pipe improvementsA32 7-14 MOVING EXISTING HYDRANTS EA 0 -$ $0 Impacts related to new sidewalksA33 8-01SWPPP AND TESC PLAN AND IMPLEMENTATIONLS 1 79,800$ $79,800 Required by water quality and pipe improvementsA34 8-02PROPERTY RESTORATIONEST 1 10,000$ $10,000 Required by water quality and pipe improvementsA35 8-02 ROADSIDE RESTORATIONLS 1 2,300$ $2,300 Adjusted to curb impacts on 125th Ave onlyA36 8-02 PSIPE, CERCIDIPHYLLUM JAPONICUM (KATSURA), 2" CAL EA 0 -$ $0 New tree plantingsA37 8-02 PSIPE, STYRAX JAPONICUS (JAPANESE SNOWBELL), 2" CAL EA 0 -$ $0 New tree plantingsA38 8-02 PSIPE, CARPINUS BETULUS 'FASTIGATA' (EUROPEAN HORNBEAM), 2" CAL EA 0 -$ $0 New tree plantingsA39 8-06CEMENT CONC. DRIVEWAY ENTRANCESY 0 -$ $0 Impacts related to new sidewalksA40 8-04CEMENT CONC. TRAFFIC CURB AND GUTTERLF 4400 30$ $132,000 Required by water quality and pipe improvementsA41 8-04CEMENT CONC. TRAFFIC CURBLF 50 70$ $3,500 Required by water quality and pipe improvementsA42 8-12 CHAIN LINK FENCE TYPE 3LF 0 -$ $0 Impacts related to new sidewalksA43 8-12 CHAIN LINK FENCE TYPE 4LF 0 -$ $0 Impacts related to new sidewalksA44 8-12CHAIN LINK GATEEA 0 -$ $0 Impacts related to new sidewalksA45 8-12WOOD FENCELF 0 -$ $0 Impacts related to new sidewalksA46 8-14PERVIOUS CEMENT CONC. SIDEWALKSY 0 -$ $0 New pervious sidewalksA47 8-14 CEMENT CONC. CURB RAMP TYPE PERPENDICULAR A EA 7 2,400$ $16,800 Required by water quality and pipe improvementsA48 8-14 CEMENT CONC. CURB RAMP TYPE PERPENDICULAR B EA 3 2,400$ $7,200 Required by water quality and pipe improvementsA49 8-18 RELOCATE MAILBOXEA 0 -$ $0 Impacts related to new sidewalksA50 8-19 ADJUST FRANCHISE UTILITY APPURTENANCES EA 0 -$ $0 Impacts related to new sidewalksA51 8-21 PERMANENT SIGNINGLS 1 3,000$ $3,000 Required by water quality and pipe improvementsA52 8-22 PLASTIC CROSSWALK LINESF 400 7$ $2,800 Required by water quality and pipe improvementsA53 8-22PAINT LINELF 60 5$ $300 Required by water quality and pipe improvementsTotal Line Item Cost $2,640,489TAX 0.0% -$ Total Construction Cost 2,640,489$ Contingency 10% 264,049$ TOTAL COST WITH CONTINGENCY 2,904,600$ City of Renton 172nd St and 125th Ave GSIEcology EligiblePrinted: 6/10/2021Page 1/1DocuSign Envelope ID: 01C814B1-0BBA-4C1D-A80D-C3E897DA2B57 Appendix F 60% Plans and BMP Details CITY OF RENTON172ND ST AND 125TH AVE GREENSTORMWATER INFRASTRUCTURE (GSI)PROJECT90% SUBMITTALOsborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDPROJECTLOCATIONVICINITY MAP N.T.SLOCATION MAP N.T.SPROJECTLOCATION172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTCOVER SHEET AND VICINITY MAPSHEET INDEXSHEET #DRAWING #SHEET TITLE(FUNDED IN PART BY THE WASHINGTONSTATE DEPARTMENT OF ECOLOGY) GENERAL NOTES:······TEMPORARY EROSION AND SEDIMENT CONTROL (TESC)STANDARD PLAN NOTES:SURVEY NOTESSEQUENCE OF CONTRUCTIONOsborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITED172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTNOTES LEGENDOsborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDABBREVIATIONS172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTLEGEND AND ABBREVIATIONSSE 172ND ST ALIGNMENT CONTROL122ND AVE SE ALIGNMENT CONTROL123RD AVE SE ALIGNMENT CONTROL124TH AVE SE ALIGNMENT CONTROL125TH AVE SE ALIGNMENT CONTROL 12204170461704017034170261705317045170391703317025121371214512201170261701817012170041686416858170251701717011170031686316855KEY MAP N.T.SGENERAL NOTES:MATCHLINE SEE BELOW MATCHLINE SEE SHEET 08MATCHLINE SEE ABOVE 172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTEXISTING CONDITIONS - 122ND AVE SE 1230612210170451703917033122151230112307170461704017034170251701717011170031686316855170261701817012170041686416856KEY MAP N.T.SMATCHLINE SEE BELOW MATCHLINE SEE ABOVE MATCHLINE SEE SHEET 08 172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTEXISTING CONDITIONS - 123RD AVE SEGENERAL NOTES: 12314170541704617040170341232312401170451703917033170261701817012170041686416856170251701717011170031686318655KEY MAP N.T.SMATCHLINE SEE BELOW MATCHLINE SEE SHEET 08MATCHLINE SEE ABOVE 172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTEXISTING CONDITIONS - 124TH AVE SEGENERAL NOTES: 171211711517109171031712017112171041241512505170251701717011170031686316855168901688216876168681686016854KEY MAP N.T.SMATCHLINE SEE BELOW MATCHLINE SEE SHEET 09MATCHLINE SEE ABOVE 172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTEXISTING CONDITIONS - 125TH AVE SEGENERAL NOTES: 12210122041705312137121451220112207122151230112314123061712117054123071231512323124011240712415KEY MAP N.T.SMATCHLINE SEE BELOWMATCHLINE SEE SHEET 04MATCHLINE SEE SHEET 06MATCHLINE SEE SHEET 09 MATCHLINE SEE ABOVE MATCHLINE SEE SHEET 05172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTEXISTING CONDITIONS - SE 172ND ST - 1GENERAL NOTES: 17121125141712012520124151250512513125211252712535125261253512541125491255517208127131271617130126041260412721KEY MAP N.T.SMATCHLINE SEE SHEET 07MATCHLINE SEE SHEET 08MATCHLINE SEE ABOVE MATCHLINE SEE BELOW172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTEXISTING CONDITIONS - SE 172ND ST - 2GENERAL NOTES: 12204170461704017034170531704517039170331213712145122011702617018170121700416864168581702517017170111700316863168551702617025GENERAL NOTES:SITE PREPARATION AND TESC NOTES:172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTTESC AND DEMOLITION PLAN - 122ND AVE SEOsborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDKEY MAP N.T.SMATCHLINE SEE ABOVE MATCHLINE SEE BELOW MATCHLINE SEE SHEET 14 1221512301123071230612210170451703917033170461704017034170251701717011170031686316855170261701817012170041686416856GENERAL NOTES:SITE PREPARATION AND TESC NOTES:Osborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDKEY MAP N.T.SMATCHLINE SEE ABOVE MATCHLINE SEE BELOW 172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTTESC AND DEMOLITION PLAN - 123RD AVE SEMATCHLINE SEE SHEET 14 12314170541704617040170341704517039170331702617018170121700416864168561702517017170111700316863186551232312401GENERAL NOTES:SITE PREPARATION AND TESC NOTES:Osborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDKEY MAP N.T.SMATCHLINE SEE ABOVE MATCHLINE SEE BELOW 172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTTESC AND DEMOLITION PLAN - 124TH AVE SEMATCHLINE SEE SHEET 14 171211711517109171031712017112171041702517017170111700316863168551689016882168761686816860168541241512505GENERAL NOTES:SITE PREPARATION AND TESC NOTES:Osborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDKEY MAP N.T.SMATCHLINE SEE ABOVE MATCHLINE SEE BELOW 172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTTESC AND DEMOLITION PLAN - 125TH AVE SEMATCHLINE SEE SHEET 15 12210122041705312137121451220112207122151230112314123061712117054123071231512323124011240712415GENERAL NOTES:SITE PREPARATION AND TESC NOTES:Osborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDKEY MAP N.T.SMATCHLINE SEE ABOVE MATCHLINE SEE BELOWMATCHLINE SEE SHEET 15 172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTTESC AND DEMOLITION PLAN - SE 172ND ST - 1MATCHLINE SEE SHEET 10MATCHLINE SEE SHEET 11MATCHLINE SEE SHEET 12 17121125141712012520124151250512513125211252712535125261254112549125551720812713127161713012604126041272112535GENERAL NOTES:SITE PREPARATION AND TESC NOTES:Osborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDKEY MAP N.T.SMATCHLINE SEE ABOVE MATCHLINE SEE BELOW MATCHLINE SEE SHEET 14 172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTTESC AND DEMOLITION PLAN - SE 172ND ST - 2MATCHLINE SEE SHEET 13 1705312204170461704017034170261705317045170391703317025121371214512201GENERAL NOTES:····KEY NOTES:GENERAL NOTES:····KEY NOTES:Osborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDKEY MAP N.T.SMATCHLINE SEE SHEET 17 MATCHLINE SEE SHEET 24 172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTPLAN AND PROFILE - 122ND AVE SE - 1 122ND AVE BYPASS2CB-10 TO CB-131CB-12 TO CB-134CB-14 TO CB-153 170261701817012170041686416858170251701717011170031686316855GENERAL NOTES:····KEY NOTES:Osborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDKEY MAP N.T.SMATCHLINE SEE SHEET 16 172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTPLAN AND PROFILE - 122ND AVE SE - 2CB-4 TO CB-7CB-2 TO CB-94CB-6 TO CB-7CB-1 TO CB-2 12306122101704517039170331221512301170461704017034GENERAL NOTES:····KEY NOTES:Osborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDKEY MAP N.T.SMATCHLINE SEE SHEET 19 MATCHLINE SEE SHEET 24 172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTPLAN AND PROFILE - 123RD AVE SE - 1CB-25 TO CB-26CB-24 TO CB-29CB-27 TO CB-28 170251701717011170031686316855170261701817012170041686416856GENERAL NOTES:····KEY NOTES:Osborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDKEY MAP N.T.SMATCHLINE SEE SHEET 18 172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTPLAN AND PROFILE - 123RD AVE SE - 2CB-19 TO CB-22CB-17 TO CB-23CB-16 TO CB-17CB-21 TO CB-22 12314170541704617040170341232312401170451703917033GENERAL NOTES:····KEY NOTES:Osborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDKEY MAP N.T.SMATCHLINE SEE SHEET 21 MATCHLINE SEE SHEET 25 172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTPLAN AND PROFILE - 124TH AVE SE - 1CB-41 TO CB-44CB-40 TO CB-45CB-43 TO CB-44 170261701817012170041686416856170251701717011170031686318655GENERAL NOTES:····KEY NOTES:Osborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDKEY MAP N.T.SMATCHLINE SEE SHEET 20 172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTPLAN AND PROFILE - 124TH AVE SE - 2CB-33 TO CB-38 124TH AVE BYPASSCB-30 TO CB-31CB-37 TO CB-38 171211711517109171031712017112171041241512505GENERAL NOTES:····KEY NOTES:Osborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDKEY MAP N.T.SMATCHLINE SEE SHEET 23 MATCHLINE SEE SHEET 25 172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTPLAN AND PROFILE - 125TH AVE SE - 1CB-56 TO CB-59CB-55 TO CB-60CB-58 TO CB-59CB-55 TO CB-90CB-88 TO CB-89 170251701717011170031686316855168901688216876168681686016854GENERAL NOTES:····KEY NOTES:Osborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDKEY MAP N.T.SMATCHLINE SEE SHEET 22 172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTPLAN AND PROFILE - 125TH AVE SE - 2CB-50 TO CB-54CB-48 TO CB-95CB-53 TO CB-54CB-46 TO CB-48 122101220417053121371214512201122071221512301GENERAL NOTES:····KEY NOTES:Osborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDKEY MAP N.T.SMATCHLINE SEE SHEET 25MATCHLINE SEE SHEET 16MATCHLINE SEE SHEET 18CB-63 TO CB-68 172ND AVE BYPASS172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTPLAN AND PROFILE - SE 172ND ST - 1CB-63 TO CB-87CB-66 TO CB-68 12314123061712117054123071231512323124011240712415GENERAL NOTES:····KEY NOTES:Osborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDKEY MAP N.T.SMATCHLINE SEE SHEET 20MATCHLINE SEE SHEET 26 MATCHLINE SEE SHEET 24 172ND AVE BYPASS-2 172ND AVE BYPASS172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTPLAN AND PROFILE - SE 172ND ST - 2 CB-72 TO CB-75 CB-69 TO CB-70 1712112514171201252012415125051251312521125271253512526GENERAL NOTES:····KEY NOTES:Osborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDMATCHLINE SEE SHEET 22MATCHLINE SEE SHEET 25 172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTPLAN AND PROFILE - SE 172ND ST - 3CB-80 TO CB-91CB-77 TO CB-96KEY MAP N.T.SCB-78 TO CB-97 12716171301260412604GENERAL NOTES:····KEY NOTES:Osborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDKEY MAP N.T.SMATCHLINE SEE SHEET 26 172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTPLAN AND PROFILE - SE 172ND ST - 4CB-74 TO CB-76CB-98 TO CB-90 ROADWAY SECTION - SE 172ND AVE (WITH BIORETENTION)ROADWAY SECTION - 123RD AVE SEOsborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITED172ND ST AND 125TH AVE GREENSTORMWATER INFRASTRUCTURE (GSI)PROJECTROADWAY SECTIONSRROADWAY SECTION - SE 172ND AVE(STA 51+48 TO 59+36 AND STA 59+66 TO 62+17)ROADWAY SECTION - SE 172ND AVE(STA 59+36 TO 59+66)ROADWAY SECTION - 125TH AVE SEROADWAY SECTION - 124TH AVE SEROADWAY SECTION - 123RD AVE SEROADWAY SECTION - 122ND AVE SE AAPLAN VIEWSECTION A-A(STANDARD DEPTH SHOWN)NOTES172ND ST AND 125TH AVE GREENSTORMWATER INFRASTRUCTURE (GSI)PROJECTDETAILS - 1Osborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDFILTERRA CONFIGURATION1FTPD CONFIGURATION DETAILSSTREET NAMEMEDIA BAY SIZEVAULT SIZE (W x L)WEIR LENGTH*MAX BYPASSFLOW (CFS)INLET/OUTLETACCESS DIAGRATE QTY& SIZE NOTESNOTESOsborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDPERVIOUS CONCRETE SIDEWALK DETAIL1172ND ST AND 125TH AVE GREENSTORMWATER INFRASTRUCTURE (GSI)PROJECTDETAILS - 2TRENCH AND BACKFILL FOR TWOPIPES WITHIN THE SAME TRENCH2ASPHALT THICKENED EDGE3 12204170461704017034170261705317045170391703317025121371214512201170261701817012170041686416858170251701717011170031686316855LEGENDCONSTRUCTION NOTES:GENERAL NOTES:172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECT122ND AVE SE LANDSCAPE AND RESTORATIONPLANOsborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDKEY MAP N.T.SMATCHLINE SEE ABOVE MATCHLINE SEE BELOW MATCHLINE SEE SHEET 35 1230612210170451703917033122151230112307170461704017034170251701717011170031686316855170261701817012170041686416856LEGENDCONSTRUCTION NOTES:GENERAL NOTES:Osborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDKEY MAP N.T.SMATCHLINE SEE ABOVE MATCHLINE SEE BELOW 172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECT123RD AVE SE LANDSCAPE AND RESTORATIONPLANMATCHLINE SEE SHEET 35 12314170541704617040170341232312401170451703917033170261701817012170041686416856170251701717011170031686318655LEGENDCONSTRUCTION NOTES:GENERAL NOTES:Osborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDKEY MAP N.T.SMATCHLINE SEE ABOVE MATCHLINE SEE BELOW 172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECT124TH AVE SE LANDSCAPE AND RESTORATIONPLANMATCHLINE SEE SHEET 35 171211711517109171031712017112171041241512505170251701717011170031686316855168901688216876168681686016854LEGENDCONSTRUCTION NOTES:GENERAL NOTES:Osborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDKEY MAP N.T.SMATCHLINE SEE ABOVE MATCHLINE SEE BELOW 172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECT125TH AVE SE LANDSCAPE AND RESTORATIONPLANMATCHLINE SEE SHEET 36 12210122041705312137121451220112207122151230112314123061712117054123071231512323124011240712415LEGENDCONSTRUCTION NOTES:GENERAL NOTES:Osborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDKEY MAP N.T.SMATCHLINE SEE ABOVE MATCHLINE SEE BELOWMATCHLINE SEE SHEET 36 172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTSE 172ND ST LANDSCAPE AND RESTORATIONPLANMATCHLINE SEE SHEET 31MATCHLINE SEE SHEET 32MATCHLINE SEE SHEET 33MATCHLINE SEE SHEET ### 17121125141712012520124151250512513125211252712535125261253512541125491255517208127131271617130126041260412721LEGENDGENERAL NOTES:CONSTRUCTION NOTES:Osborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITEDKEY MAP N.T.SMATCHLINE SEE ABOVE MATCHLINE SEE BELOW MATCHLINE SEE SHEET 37 MATCHLINE SEE SHEET 35 172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTSE 172ND ST LANDSCAPE AND RESTORATIONPLANMATCHLINE SEE SHEET 34 SE 172ND STREET123ND AVENUE SE CURB RETURN TABLECURB RETURN TABLECURB RETURN TABLESE 172ND STREET123ND AVENUE SEOsborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITED172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTINTERSECTION PLAN 1INTERSECTION DETAIL - SE 172ND STREET AND 123RD AVENUE SEINTERSECTION DETAIL - SE 172ND STREET AND 122ND AVENUE SE SE 172ND STREET124TH AVENUE SE CURB RETURN TABLECURB RETURN TABLECURB RETURN TABLECURB RETURN TABLE125TH AVENUE SESE 172ND STREETOsborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITED172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTINTERSECTION PLAN 2INTERSECTION DETAIL - SE 172ND STREET AND 125TH AVENUE SEINTERSECTION DETAIL - SE 172ND STREET AND 124TH AVENUE SEMATCHLINE SEE SHEET 39 SE 172ND STREETCURB RETURN TABLECURB RETURN TABLECURB RETURN TABLECURB RETURN TABLECURB RETURN TABLE125TH AVENUE SESE 171ST STREET SE 172ND STREET125TH PLACE SEOsborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITED172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTINTERSECTION PLAN 3INTERSECTION DETAIL - 125TH AVENUE SE AND SE 170TH STREETINTERSECTION DETAIL - SE 172ND STREET AND 125TH AVENUE SEMATCHLINE SEE SHEET 38 INTERSECTION DETAIL - SE 172ND STREET AND 125TH PLACE SE DRIVEWAY TABLEOsborn Consulting, Inc.Bellevue | Seattle | Spokanewww.osbornconsulting.comOSBORNCONSULTINGINCORPORATEDRERSGEITED172ND ST AND 125TH AVE GREEN STORMWATERINFRASTRUCTURE (GSI) PROJECTHORIZONTAL CONTROLDRIVEWAY TABLE LEGEND Appendix G Wetland Delineation Report 750 Sixth Street South | Kirkland, WA 98033 P 425.822.5242 | f 425.827.8136 | watershedco.com May 29, 2019 Osborn Consulting, Inc. Attn: Cheyenne Covington 1800 112th Ave. NE, Suite 220-E Bellevue, WA 98004 (425) 451-4009 Re: Renton 172nd St GSI Project, Wetland Delineation Report The Watershed Company Reference Number: 190229 Dear Cheyenne: On May 14, 2019, ecologists Logan Dougherty and Grace Brennan visited the 172nd Street GSI project in Renton, Washington (parcel #3956200000) to confirm prior delineation results done for the La Fortuna Townhomes project and extend the delineation line farther west in support of this project. This letter summarizes the findings of the study and details applicable federal, state, and local regulations. The following documents are enclosed: Delineation Sketch Wetland Determination Data Forms Wetland Rating Forms Findings Summary Two wetlands (Wetlands A and B) are located near the project area. Wetland A lies on the western side of the La Fortuna property, and extends west past the parcel boundary. Wetland B is on the north east portion of the undeveloped area of the La Fortuna property. Wetland A is a Category II wetland with six habitat points, and Wetland B is a Category III wetland with four habitat points. The City of Renton requires a 100-foot standard buffer for Wetland A and a 50- foot standard buffer for Wetland B. Wetland Delineation Report Osborn Consulting, Inc. May 29, 2019 Page 2 Study Area The study area for this project is defined as areas on parcel 3956200000 within 200 feet of the stormwater outfalls located at the southern street end of 127th Ave SE, immediately south the SE 172nd Street in the City of Renton, WA. Methods Public‐domain information on the subject properties was reviewed for this delineation study. Resources and review findings are presented in Table 1 of the “Findings” section of this letter. The study area was evaluated for wetlands using methodology from the Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Western Mountains, Valleys, and Coast Region Version 2.0 (U.S. Army Corps of Engineers 2010). Presence or absence of wetlands was determined on the basis of an examination of vegetation, soils and hydrology. These parameters were sampled at several locations along the wetland boundary to determine the approximate wetland edge. Wetlands were classified using the Department of Ecology’s 2014 rating system (Hruby 2014). Characterization of climatic conditions for precipitation in the Wetland Determination Data Forms were determined using the WETS table methodology (USDA, NRCS 2015). The “Seattle Tacoma Intl AP” station from 1981‐2010 was used as a source for precipitation data (http://agacis.rcc‐acis.org/). The WETS table methodology uses climate data from the three months prior to the site visit month to determine if normal conditions are present in the study area region. The study area was also evaluated for streams based on the presence or absence of an ordinary high water mark (OHWM) as defined by Section 404 of the Clean Water Act, the Washington Administrative Code (WAC) 220‐660‐030, and the Revised Code of Washington (RCW) 90.58.030. Findings The study area is within in the Soos Creek sub-basin of the Duwamish – Green watershed (WRIA 9); Section 28 of Township 23 North, Range 05 East of the Public Land Survey System. It is located in the Spring Glen neighborhood of Renton, north of SE Petrovitsky Road. The property is along a moderate gradient, sloping downhill to the southwest. Areas east of the stormwater outfalls includes numerous attached townhome units, a private access road, lawns, and community gardens. The area south and west of the outfalls is undeveloped and forested. Wetland Delineation Report Osborn Consulting, Inc. May 29, 2019 Page 3 Reviewed public-domain information for the site is summarized below (Table 1). Table 1. Summary of online mapping and inventory resources. Wetlands One wetland (Wetland A) was delineated and flagged in the project area. Another wetland just outside of the study area (Wetland B) was delineated and flagged on the north east portion of the undeveloped area of the La Fortuna property. Wetland A is summarized in Table 2. Resource Summary USDA NRCS: Web Soil Survey Alderwood gravelly sandy loam, 8 to 15 percent slopes; Arents, Alderwood material, 6 to 15 percent slopes; Seattle Muck. USFWS: NWI Wetland Mapper Numerous wetlands identified on and adjacent to the project area. WDFW: PHS on the Web No priority habitat or species. WDFW: SalmonScape No salmonids mapped within project site. Documented presence of salmonids, approx. 1,000 feet south of project area. WA-DNR: Forest Practices Activity Mapping Tool No mapped streams. Nearest stream approximately 1,000 south. King County iMap Mapped wetlands in the project area. City of Renton maps Mapped wetlands in the project area. WETS Climatic Condition Normal Wetland Delineation Report Osborn Consulting, Inc. May 29, 2019 Page 4 Table 2. Wetland A assessment summary. WETLAND A – Assessment Summary Location: City of Renton Parcel #3956210000 WRIA / Sub-basin: Duwamish – Green (WIRA 9) / Soos Creek Photo 1. Wetland A. 2014 Western WA Ecology Rating: Category II Buffer Width and Buffer Setback: 100-ft buffer, 15-foot setback Wetland Size: Approximately 5 acres Cowardin Classification(s): Palustrine Forested HGM Classification(s): Depressional Wetland Data Sheet(s): DP – 1 Upland Data Sheet (s): DP – 2 Flag Color: Pink and black striped Flag Numbers: A-1 to A-45 Vegetation Tree stratum: Western red cedar, red alder, black cottonwood, Oregon ash, Pacific willow, Sitka willow Shrub stratum: Black twinberry, red-osier dogwood, Douglas spirea, vine maple, highbush cranberry, salmonberry Herb stratum: Skunk cabbage, slough sedge, small-fruited bulrush, lady fern, creeping buttercup Soils Soil survey: Alderwood gravelly sandy loam; Arents, Alderwood material; Seattle Muck Field data: Hydrogen sulfide (A4) Hydrology Source: Groundwater, piped and ditched runoff, precipitation Field data: High Water Table (A2), Saturation (A3), Hydrogen Sulfide Odor (C1) Wetland Functions Improving Water Quality Hydrologic Habitat Site Potential H M L H M L H M L Landscape Potential H M L H M L H M L Value H M L H M L H M L TOTAL Score Based on Ratings 9 7 6 22 Description and Comments Wetland A is a large forested wetland that drains to the south to an even larger wetland complex associated with Soos creek that is located south of SE Petrovitsky Road. Numerous stormwater pipes, culverts, and ditches flow into the wetland, likely providing much of the wetland hydrology. Wetland Delineation Report Osborn Consulting, Inc. May 29, 2019 Page 5 Streams The property lacked stream indicators including watermarks, channel definition, or hydraulically sorted sediments. Based on these findings, there are no jurisdictional streams present in the project area. Non -wetlands Areas outside of identified wetlands did not meet criteria for hydrophytic vegetation, hydric soils, and wetland hydrology. These areas are primarily forested. One area between the La Fortuna Townhomes stormwater outfall and Wetland A exhibits the three-parameter test for wetland. However, this area is not jurisdictional because it is an intentionally constructed stormwater feature created from a non-wetland site. A ditch running east-west is located just off site to the north. The ditch is four to six feet wide and approximately 150 feet long. The feature is linear with minimal variation in width and course. The eastern 75 feet of ditch is unvegetated. The western portion has been lined with landscape rocks. No standing water was present at the time of the site visit, but informal bridges and the presence of algae in the ditch suggest that water regularly inundates the feature. Local Regulations Wetland buffers in the City of Renton are determined by a combination of the wetland category and habitat score, as determined by the wetland rating system. Wetland A is a Category II Photo 3. Ditch feature, looking west. Wetland Delineation Report Osborn Consulting, Inc. May 29, 2019 Page 6 wetland with a habitat score of 6 and therefore requires a standard buffer of 100 feet. Wetland B rated as Category III with a habitat score of 4 and therefore requires a standard buffer of 50 feet. An additional 15-foot structure setback is required beyond the limit of each buffer. The area between the La Fortuna Townhomes stormwater outfall and Wetland A is a recently excavated feature identified as a “filter / spreader” on site mitigation plans and meets wetland criteria for hydrophytic plants, hydric soils, and wetland hydrology. However, it is clearly man-made stormwater feature and does not meet the Renton definition of a regulated wetland. According to RMC 4-3-050(B)(1), regulated wetlands do not include those artificial wetlands intentionally created from non-wetland sites. The ditch running east-west just off-site to the north is presumably an artificial, constructed feature due to the linear position and shape, lack of vegetation, and partial armoring. Therefore, it will likely not be regulated as a jurisdictional critical area. Stormwater Facilities According to RMC 4-3-050C(3), modifications to surface water discharge pipes and stormwater regional facilities are allowed in wetland buffers provided that they are designed to meet Washington State Department of Ecology’s Wetlands and Stormwater Management Guidelines or equivalent objectives. State and Federal Regulations Federal Agencies Most wetlands and streams are regulated by the Corps under section 404 of the Clean Water Act. Any proposed filling or other direct impacts to Waters of the U.S., including wetlands (except isolated wetlands), would require notification and permits from the Corps. Wetland A is not isolated. Wetland A appears to be isolated; a Jurisdictional Determination from the Corps would be required to confirm the wetland’s jurisdictional status. Unavoidable impacts to jurisdictional wetlands are typically required to be compensated through implementation of an approved mitigation plan. Federally permitted actions that could affect endangered species may also require a biological assessment study and consultation with the U.S. Fish and Wildlife Service and/or the National Marine Fisheries Service. Compliance with the Endangered Species Act must be demonstrated for activities within jurisdictional wetlands and the 100‐year floodplain. Application for Corps permits may also require an individual 401 Water Quality Certification and Coastal Zone Wetland Delineation Report Osborn Consulting, Inc. May 29, 2019 Page 7 Management Consistency determination from Ecology and a cultural resource study in accordance with Section 106 of the National Historic Preservation Act. Washington De partment of Ecology (Ecology) Similar to the Corps, Ecology, under Section 401 of the Clean Water Act, is charged with reviewing, conditioning, and approving or denying certain federally permitted actions that result in discharges to state waters. However, Ecology review would only become necessary if a Section 404 permit from the Corps was issued. Therefore, if filling activities are avoided, authorization from Ecology would not be needed. If filling is proposed, a JARPA could be submitted to Ecology in order to obtain a Section 401 Water Quality Certification and Coastal Zone Management Consistency Determination. Ecology permits are either issued concurrently with the Corps permit or within 90 days following the Corps permit. In general, neither the Corps, nor Ecology nor regulates wetland buffers, unless direct impacts are proposed. When direct impacts are proposed, mitigated wetlands and streams may be required to employ buffers based on Corps and Ecology joint regulatory guidance. Washington Department o f Fish and Wildlife (WDFW) Chapter 77.55 of the RCW (the Hydraulic Code) gives WDFW the authority to review, condition, and approve or deny “any construction activity that will use, divert, obstruct, or change the bed or flow of state waters.” This provision includes any in‐water work, the crossing or bridging of any state waters and can sometimes include stormwater discharge to state waters. If a project meets regulatory requirements, WDFW will issue a Hydraulic Project Approval (HPA). Since there are no streams in proximity to the project outfalls, an HPA would not be needed on this project. Disclaimer The information contained in this letter is based on the application of technical guidelines currently accepted as the best available science and in conjunction with the manuals and criteria referenced above. All discussions, conclusions and recommendations reflect the best professional judgment of the author(s) and are based upon information available at the time the study was conducted. All work was completed within the constraints of budget, scope, and timing. The findings of this report are subject to verification and agreement by the appropriate local, state and federal regulatory authorities. No other warranty, expressed or implied, is made. Wetland Delineation Report Osborn Consulting, Inc. May 29, 2019 Page 8 Please call if you have any questions or if we can provide you with any additional information. Sincerely, Grace Brennan Ecologist Logan Dougherty Ecologist Enclosures Wetland Delineation Report Osborn Consulting, Inc. May 29, 2019 Page 9 References Anderson, P.S. et al. 2016. Determining the Ordinary High Water Mark for Shoreline Management Act Compliance in Washington State. (Publication #16-06-029). Olympia, WA: Shorelands and Environmental Assistance Program, Washington Department of Ecology. Hruby, T. 2014. Washington State Wetland Rating System for Western Washington: 2014 Update. (Publication #14-06-029). Olympia, WA: Washington Department of Ecology. Lichvar, R.W. and S. M. McColley. 2008. A Guide to Ordinary High Water Mark (OHWM) Delineation for Non-Perennial Streams in the Western Mountains, Valleys, and Coast Region of the United States. ERDC/CRREL TR-14-13. Hanover, NH: U.S. Army Engineer Research and Development Center. U.S. Army Corps of Engineers. 2010. Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Western Mountains, Valleys, and Coast Region (Version 2.0). ed. J. S. Wakely, R. W. Lichvar, and C. V. Noble. ERDC/EL TR-10-3. Vicksburg, MS: U.S. Army Engineer Research and Development Center. U.S. Department of Agriculture (USDA), Natural Resources Conservation Service (NRCS). 2015. National Engineering Handbook, Part 650 Engineering Field Handbook, Chapter 19 Hydrology Tools for Wetland Identification and Analysis. ed. R. A. Weber. 210-VI-NEH, Amend. 75. Washington, DC. Page 1 of 1 Wetland Delineation Sketch – City of Renton SE 172nd St Storm Water Improvements Parcel Number: 3956200000 Prepared for: Cheyenne Covington, Osborn Consulting Inc. Site Visit Date: 5/14/19 TWC Ref. No.: 190229 Wetland B Flags B-1 to B-10 Connect B-1 to B-10 DP-1 LEGEND Wetland Wetland Boundary – delineated 5/14/19 (Flags A-42 to A-45) Wetland Boundary – delineated 8/21/18, verified 5/14/19 (Flags A-1 to A-41) Non-delineated/non-verified Wetland Boundary Delineated Ditch boundary Non-delineated Ditch boundary La Fortuna stormwater outfall area Culvert Data Point (DP) Note: Field sketch only. Features depicted are approximate and not to scale. Wetland boundary is marked with pink- and black-striped flags. Data points are marked with yellow- and black-striped flags. Ditch Flags D-1 to D-8 Connect D-1 to D-8 Do not connect D-4 to D-5 DP-2 DP-3 DP-4 DP-5 DP-6 Wetland A Flags A-1 to A-45 US Army Corps of Engineers Western Mountains, Valleys, and Coast – Version 2.0 750 Sixth Street South Kirkland, Washington 98033 (425) 822-5242 watershedco.com WETLAND DETERMINATION DATA FORM Western Mountains, Valleys, and Coast Supplement to the 1987 COE Wetlands Delineation Manual Project Site: Renton 172nd Storm Water Improvements Sampling date: August 21, 2018 Applicant/Owner: Osborn Consulting Sampling Point: DP-1 Investigator: Logan Dougherty, Sam Payne City/County: Renton / King Sect., Township, Range: S 28 T 23N R 05E State: Washington Landform (hillslope, terrace, etc): Depression Slope (%): 0 Local relief (concave, convex, none): None Subregion (LRR): A Lat: Long: Datum: Soil Map Unit Name: Seattle Muck NWI classification: PFOC (Freshwater Forested/Shrub) Are climatic/hydrologic conditions on the site typical for this time of year? ☐ Yes ☒ No (If no, explain in remarks.) Are “Normal Circumstances” present on the site? ☒ Yes ☐ No (If needed, explain any answers in Remarks.) Are Vegetation☐, Soil ☐, or Hydrology ☐ significantly disturbed? Are Vegetation☐, Soil ☐, or Hydrology ☐ naturally problematic SUMMARY OF FINDINGS – Attach site map showing sampling point locations, transects, important features, etc. Hydrophytic Vegetation Present? Yes ☒ No ☐ Is the Sampling Point within a Wetland? Yes ☒ No ☐ Hydric Soils Present? Yes ☒ No ☐ Wetland Hydrology Present? Yes ☒ No ☐ Remarks: Drier than normal per WETS (Seattle-Tacoma International Airport) VEGETATION – Use scientific names of plants. Tree Stratum (Plot size: 5m diam.) Absolute % Cover Dominant Species? Indicator Status Dominance Test Worksheet 1. Alnus rubra 90 Y FAC Number of Dominant Species that are OBL, FACW, or FAC: 5 (A) 2. Populus balsamifera 30 Y FAC 3. Total Number of Dominant Species Across All Strata: 5 (B) 4. 120 = Total Cover Percent of Dominant Species that are OBL, FACW, or FAC: 100 (A/B) Sapling/Shrub Stratum (Plot size: 3m diam.) 1. Cornus sericea 70 Y FACW Prevalence Index Worksheet 2. Lonicera involucrata 60 Y FAC Total % Cover of Multiply by 3. OBL species x 1 = 4. FACW species x 2 = 5. FAC species x 3 = 130 = Total Cover FACU species x 4 = UPL species x 5 = Herb Stratum (Plot size: 1m diam.) Column totals (A) (B) 1. Carex obnupta 70 Y OBL 2. Prevalence Index = B / A = 3. 4. Hydrophytic Vegetation Indicators 5. ☒ Dominance test is > 50% 6. ☐ Prevalence test is ≤ 3.0 * 7. Morphological Adaptations * (provide supporting 8. ☐ data in remarks or on a separate sheet) 9. ☐ Wetland Non-Vascular Plants * 10. ☐ Problematic Hydrophytic Vegetation * (explain) 11. 70 = Total Cover * Indicators of hydric soil and wetland hydrology must be present, unless disturbed or problematic Woody Vine Stratum (Plot size: ) Hydrophytic Vegetation Present? Yes ☒ No ☐ 1. 2. 0 = Total Cover % Bare Ground in Herb Stratum: 30 Remarks : DP- 1 US Army Corps of Engineers Western Mountains, Valleys, and Coast – Version 2.0 750 Sixth Street South Kirkland, Washington 98033 (425) 822-5242 watershedco.com SOIL Sampling Point – DP- 1 HYDROLOGY WETLAND DETERMINATION DATA FORM Profile Description: (Describe to the depth needed to document the indicator or confirm the absence of indicators.) Depth Matrix Redox Features (inches) Color (moist) % Color (moist) % Type1 Loc2 Texture Remarks 0-1 10YR 2/1 100 Muck High organic matter content 1-16 10YR 2/2 100 Silt loam Abundant non- decomposed organic matter 1Type: C=Concentration, D=Depletion, RM=Reduced Matrix, CS=Covered or Coated Sand Grains 2Loc: PL=Pore Lining, M=Matrix Hydric Soil Indicators: (Applicable to all LRRs, unless otherwise noted.) Indicators for Problematic Hydric Soils3 ☐ Histosol (A1) ☐ Sandy Redox (S5) ☐ 2cm Muck (A10) ☐ Histic Epipedon (A2) ☐ Stripped Matrix (S6) ☐ Red Parent Material (TF2) ☐ Black Histic (A3) ☐ Loamy Mucky Mineral (F1) (except MLRA 1) ☐ Other (explain in remarks) ☒ Hydrogen Sulfide (A4) ☐ Loamy Gleyed Matrix (F2) ☐ ☐ Depleted Below Dark Surface (A11) ☐ Depleted Matrix (F3) ☐ Thick Dark Surface (A12) ☐ Redox Dark Surface (F6) 3 Indicators of hydrophytic vegetation and wetland hydrology must be present, unless disturbed or problematic ☐ Sandy Mucky Mineral (S1) ☐ Depleted Dark Surface (F7) ☐ Sandy Gleyed Matrix (S4) ☐ Redox Depressions (F8) Restrictive Layer (if present): Hydric soil present? Yes ☒ No ☐ Type: Depth (inches): Remarks: Wetland Hydrology Indicators: Primary Indicators (minimum of one required: check all that apply): Secondary Indicators (2 or more required): ☐ Surface water (A1) ☐ Sparsely Vegetated Concave Surface (B8) ☒ Water-Stained Leaves (B9) (MLRA 1, 2, 4A & 4B) ☒ High Water Table (A2) ☐ Water-Stained Leaves (except MLRA 1, 2, 4A & 4B) (B9) ☐ Drainage Patterns (B10) ☒ Saturation (A3) ☐ Salt Crust (B11) ☐ Dry-Season Water Table (C2) ☐ Water Marks (B1) ☐ Aquatic Invertebrates (B13) ☐ Saturation Visible on Aerial Imagery (C9) ☐ Sediment Deposits (B2) ☒ Hydrogen Sulfide Odor (C1) ☒ Geomorphic Position (D2) ☐ Drift Deposits (B3) ☐ Oxidized Rhizospheres along Living Roots (C3) ☐ Shallow Aquitard (D3) ☐ Algal Mat or Crust (B4) ☐ Presence of Reduced Iron (C4) ☒ FAC-Neutral Test (D5) ☐ Iron Deposits (B5) ☐ Recent Iron Reduction in Tilled Soils (C6) ☐ Raised Ant Mounds (D6) (LRR A) ☐ Surface Soil Cracks (B6) ☐ Stunted or Stressed Plants (D1) (LRR A) ☐ Frost-Heave Hummocks ☐ Inundation Visible on Aerial Imagery (B7) ☐ Other (explain in remarks) Field Observations Wetland Hydrology Present? Yes ☒ No ☐ Surface Water Present? Yes ☐ No ☒ Depth (in): Water Table Present? Yes ☒ No ☐ Depth (in): 0 Saturation Present? (includes capillary fringe) Yes ☒ No ☐ Depth (in): 0 Describe Recorded Data (stream gauge, monitoring well, aerial photos, previous inspections), if available: Remarks: US Army Corps of Engineers Western Mountains, Valleys, and Coast – Version 2.0 Western Mountains, Valleys, and Coast Supplement to the 1987 COE Wetlands Delineation Manual Project Site: Renton 172nd Storm Water Improvements Sampling date: August 21, 2018 Applicant/Owner: Osborn Consulting Sampling Point: DP-2 Investigator: Logan Dougherty, Sam Payne City/County: Renton / King Sect., Township, Range: S 28 T 23N R 05E State: Washington Landform (hillslope, terrace, etc): Hillslope Slope (%): 5-10 Local relief (concave, convex, none): None Subregion (LRR): A Lat: Long: Datum: Soil Map Unit Name: Seattle Muck NWI classification: PFOC (Freshwater Forested/Shrub) Are climatic/hydrologic conditions on the site typical for this time of year? ☐ Yes ☒ No (If no, explain in remarks.) Are “Normal Circumstances” present on the site? ☒ Yes ☐ No (If needed, explain any answers in Remarks.) Are Vegetation☐, Soil ☐, or Hydrology ☐ significantly disturbed? Are Vegetation☐, Soil ☐, or Hydrology ☐ naturally problematic SUMMARY OF FINDINGS – Attach site map showing sampling point locations, transects, important features, etc. Hydrophytic Vegetation Present? Yes ☒ No ☐ Is the Sampling Point within a Wetland? Yes ☐ No ☒ Hydric Soils Present? Yes ☐ No ☒ Wetland Hydrology Present? Yes ☐ No ☒ Remarks: Drier than normal per WETS (Seattle-Tacoma International Airport) VEGETATION – Use scientific names of plants. Tree Stratum (Plot size: 5m diam.) Absolute % Cover Dominant Species? Indicator Status Dominance Test Worksheet 1. Betula nigra 80 Y FACW Number of Dominant Species that are OBL, FACW, or FAC: 5 (A) 2. 3. Total Number of Dominant Species Across All Strata: 6 (B) 4. 80 = Total Cover Percent of Dominant Species that are OBL, FACW, or FAC: 83 (A/B) Sapling/Shrub Stratum (Plot size: 3m diam.) 1. Fraxinus latifolia 15 Y FACW Prevalence Index Worksheet 2. Thuja plicata 5 N FAC Total % Cover of Multiply by 3. Corylus cornuta 20 Y FACU OBL species x 1 = 4. Rubus armeniacus 15 Y FAC FACW species x 2 = 5. FAC species x 3 = 55 = Total Cover FACU species x 4 = UPL species x 5 = Herb Stratum (Plot size: 1m diam.) Column totals (A) (B) 1. Ranunculus repens 50 Y FAC 2. Poaceae sp. 40 Y FAC* Prevalence Index = B / A = 3. 4. Hydrophytic Vegetation Indicators 5. ☒ Dominance test is > 50% 6. ☐ Prevalence test is ≤ 3.0 * 7. Morphological Adaptations * (provide supporting 8. ☐ data in remarks or on a separate sheet) 9. ☐ Wetland Non-Vascular Plants * 10. ☐ Problematic Hydrophytic Vegetation * (explain) 11. 90 = Total Cover * Indicators of hydric soil and wetland hydrology must be present, unless disturbed or problematic Woody Vine Stratum (Plot size: ) Hydrophytic Vegetation Present? Yes ☒ No ☐ 1. 2. 0 = Total Cover % Bare Ground in Herb Stratum: 10 Remarks : *Presumed indicator status DP- 2 US Army Corps of Engineers Western Mountains, Valleys, and Coast – Version 2.0 750 Sixth Street South Kirkland, Washington 98033 (425) 822-5242 watershedco.com SOIL Sampling Point – DP- 2 HYDROLOGY WETLAND DETERMINATION DATA FORM Profile Description: (Describe to the depth needed to document the indicator or confirm the absence of indicators.) Depth Matrix Redox Features (inches) Color (moist) % Color (moist) % Type1 Loc2 Texture Remarks 0-12 10YR 2/2 100 Sandy loam 1Type: C=Concentration, D=Depletion, RM=Reduced Matrix, CS=Covered or Coated Sand Grains 2Loc: PL=Pore Lining, M=Matrix Hydric Soil Indicators: (Applicable to all LRRs, unless otherwise noted.) Indicators for Problematic Hydric Soils3 ☐ Histosol (A1) ☐ Sandy Redox (S5) ☐ 2cm Muck (A10) ☐ Histic Epipedon (A2) ☐ Stripped Matrix (S6) ☐ Red Parent Material (TF2) ☐ Black Histic (A3) ☐ Loamy Mucky Mineral (F1) (except MLRA 1) ☐ Other (explain in remarks) ☐ Hydrogen Sulfide (A4) ☐ Loamy Gleyed Matrix (F2) ☐ ☐ Depleted Below Dark Surface (A11) ☐ Depleted Matrix (F3) ☐ Thick Dark Surface (A12) ☐ Redox Dark Surface (F6) 3 Indicators of hydrophytic vegetation and wetland hydrology must be present, unless disturbed or problematic ☐ Sandy Mucky Mineral (S1) ☐ Depleted Dark Surface (F7) ☐ Sandy Gleyed Matrix (S4) ☐ Redox Depressions (F8) Restrictive Layer (if present): Hydric soil present? Yes ☐ No ☒ Type: Depth (inches): Remarks: Very hard to dig soils. Wetland Hydrology Indicators: Primary Indicators (minimum of one required: check all that apply): Secondary Indicators (2 or more required): ☐ Surface water (A1) ☐ Sparsely Vegetated Concave Surface (B8) ☐ Water-Stained Leaves (B9) (MLRA 1, 2, 4A & 4B) ☐ High Water Table (A2) ☐ Water-Stained Leaves (except MLRA 1, 2, 4A & 4B) (B9) ☐ Drainage Patterns (B10) ☐ Saturation (A3) ☐ Salt Crust (B11) ☐ Dry-Season Water Table (C2) ☐ Water Marks (B1) ☐ Aquatic Invertebrates (B13) ☐ Saturation Visible on Aerial Imagery (C9) ☐ Sediment Deposits (B2) ☐ Hydrogen Sulfide Odor (C1) ☐ Geomorphic Position (D2) ☐ Drift Deposits (B3) ☐ Oxidized Rhizospheres along Living Roots (C3) ☐ Shallow Aquitard (D3) ☐ Algal Mat or Crust (B4) ☐ Presence of Reduced Iron (C4) ☐ FAC-Neutral Test (D5) ☐ Iron Deposits (B5) ☐ Recent Iron Reduction in Tilled Soils (C6) ☐ Raised Ant Mounds (D6) (LRR A) ☐ Surface Soil Cracks (B6) ☐ Stunted or Stressed Plants (D1) (LRR A) ☐ Frost-Heave Hummocks ☐ Inundation Visible on Aerial Imagery (B7) ☐ Other (explain in remarks) Field Observations Wetland Hydrology Present? Yes ☐ No ☒ Surface Water Present? Yes ☐ No ☒ Depth (in): Water Table Present? Yes ☐ No ☒ Depth (in): Saturation Present? (includes capillary fringe) Yes ☐ No ☒ Depth (in): Describe Recorded Data (stream gauge, monitoring well, aerial photos, previous inspections), if available: Remarks: Completely dry US Army Corps of Engineers Western Mountains, Valleys, and Coast – Version 2.0 Western Mountains, Valleys, and Coast Supplement to the 1987 COE Wetlands Delineation Manual Project Site: Renton 172nd Storm Water Improvements Sampling date: August 21, 2018 Applicant/Owner: Osborn Consulting Sampling Point: DP-3 Investigator: Logan Dougherty, Sam Payne City/County: Renton / King Sect., Township, Range: S 28 T 23N R 05E State: Washington Landform (hillslope, terrace, etc): Depression Slope (%): 0 Local relief (concave, convex, none): None Subregion (LRR): A Lat: Long: Datum: Soil Map Unit Name: Seattle Muck NWI classification: PFOC (Freshwater Forested/Shrub) Are climatic/hydrologic conditions on the site typical for this time of year? ☐ Yes ☒ No (If no, explain in remarks.) Are “Normal Circumstances” present on the site? ☒ Yes ☐ No (If needed, explain any answers in Remarks.) Are Vegetation☐, Soil ☐, or Hydrology ☐ significantly disturbed? Are Vegetation☐, Soil ☐, or Hydrology ☐ naturally problematic SUMMARY OF FINDINGS – Attach site map showing sampling point locations, transects, important features, etc. Hydrophytic Vegetation Present? Yes ☒ No ☐ Is the Sampling Point within a Wetland? Yes ☒ No ☐ Hydric Soils Present? Yes ☒ No ☐ Wetland Hydrology Present? Yes ☒ No ☐ Remarks: Drier than normal per WETS (Seattle-Tacoma International Airport) VEGETATION – Use scientific names of plants. Tree Stratum (Plot size: 5m diam.) Absolute % Cover Dominant Species? Indicator Status Dominance Test Worksheet 1. Alnus rubra 95 Y FAC Number of Dominant Species that are OBL, FACW, or FAC: 5 (A) 2. 3. Total Number of Dominant Species Across All Strata: 5 (B) 4. 95 = Total Cover Percent of Dominant Species that are OBL, FACW, or FAC: 100 (A/B) Sapling/Shrub Stratum (Plot size: 3m diam.) 1. Cornus sericea 40 Y FACW Prevalence Index Worksheet 2. Lonicera involucrata 20 Y FAC Total % Cover of Multiply by 3. OBL species x 1 = 4. FACW species x 2 = 5. FAC species x 3 = 60 = Total Cover FACU species x 4 = UPL species x 5 = Herb Stratum (Plot size: 1m diam.) Column totals (A) (B) 1. Phalaris arundinacea 50 Y FACW 2. Ranunculus repens 30 Y FAC Prevalence Index = B / A = 3. Equisetum telmateia 5 N FACW 4. Hydrophytic Vegetation Indicators 5. ☒ Dominance test is > 50% 6. ☐ Prevalence test is ≤ 3.0 * 7. Morphological Adaptations * (provide supporting 8. ☐ data in remarks or on a separate sheet) 9. ☐ Wetland Non-Vascular Plants * 10. ☐ Problematic Hydrophytic Vegetation * (explain) 11. 85 = Total Cover * Indicators of hydric soil and wetland hydrology must be present, unless disturbed or problematic Woody Vine Stratum (Plot size: ) Hydrophytic Vegetation Present? Yes ☒ No ☐ 1. 2. 0 = Total Cover % Bare Ground in Herb Stratum: 15 Remarks : DP- 3 US Army Corps of Engineers Western Mountains, Valleys, and Coast – Version 2.0 750 Sixth Street South Kirkland, Washington 98033 (425) 822-5242 watershedco.com SOIL Sampling Point – DP- 3 HYDROLOGY WETLAND DETERMINATION DATA FORM Profile Description: (Describe to the depth needed to document the indicator or confirm the absence of indicators.) Depth Matrix Redox Features (inches) Color (moist) % Color (moist) % Type1 Loc2 Texture Remarks 0-6 10YR 2/2 100 Sandy loam 6-16 10YR 2/2 90 10YR 4/6 5Y 5/1 5 5 C D M Sandy loam 1Type: C=Concentration, D=Depletion, RM=Reduced Matrix, CS=Covered or Coated Sand Grains 2Loc: PL=Pore Lining, M=Matrix Hydric Soil Indicators: (Applicable to all LRRs, unless otherwise noted.) Indicators for Problematic Hydric Soils3 ☐ Histosol (A1) ☐ Sandy Redox (S5) ☐ 2cm Muck (A10) ☐ Histic Epipedon (A2) ☐ Stripped Matrix (S6) ☐ Red Parent Material (TF2) ☐ Black Histic (A3) ☐ Loamy Mucky Mineral (F1) (except MLRA 1) ☐ Other (explain in remarks) ☐ Hydrogen Sulfide (A4) ☐ Loamy Gleyed Matrix (F2) ☐ ☐ Depleted Below Dark Surface (A11) ☐ Depleted Matrix (F3) ☐ Thick Dark Surface (A12) ☒ Redox Dark Surface (F6) 3 Indicators of hydrophytic vegetation and wetland hydrology must be present, unless disturbed or problematic ☐ Sandy Mucky Mineral (S1) ☐ Depleted Dark Surface (F7) ☐ Sandy Gleyed Matrix (S4) ☐ Redox Depressions (F8) Restrictive Layer (if present): Hydric soil present? Yes ☒ No ☐ Type: Depth (inches): Remarks: Wetland Hydrology Indicators: Primary Indicators (minimum of one required: check all that apply): Secondary Indicators (2 or more required): ☐ Surface water (A1) ☐ Sparsely Vegetated Concave Surface (B8) ☐ Water-Stained Leaves (B9) (MLRA 1, 2, 4A & 4B) ☐ High Water Table (A2) ☐ Water-Stained Leaves (except MLRA 1, 2, 4A & 4B) (B9) ☐ Drainage Patterns (B10) ☐ Saturation (A3) ☐ Salt Crust (B11) ☐ Dry-Season Water Table (C2) ☐ Water Marks (B1) ☐ Aquatic Invertebrates (B13) ☐ Saturation Visible on Aerial Imagery (C9) ☐ Sediment Deposits (B2) ☐ Hydrogen Sulfide Odor (C1) ☒ Geomorphic Position (D2) ☐ Drift Deposits (B3) ☐ Oxidized Rhizospheres along Living Roots (C3) ☐ Shallow Aquitard (D3) ☐ Algal Mat or Crust (B4) ☐ Presence of Reduced Iron (C4) ☒ FAC-Neutral Test (D5) ☐ Iron Deposits (B5) ☐ Recent Iron Reduction in Tilled Soils (C6) ☐ Raised Ant Mounds (D6) (LRR A) ☐ Surface Soil Cracks (B6) ☐ Stunted or Stressed Plants (D1) (LRR A) ☐ Frost-Heave Hummocks ☐ Inundation Visible on Aerial Imagery (B7) ☐ Other (explain in remarks) Field Observations Wetland Hydrology Present? Yes ☒ No ☐ Surface Water Present? Yes ☐ No ☒ Depth (in): Water Table Present? Yes ☐ No ☒ Depth (in): Saturation Present? (includes capillary fringe) Yes ☐ No ☒ Depth (in): Describe Recorded Data (stream gauge, monitoring well, aerial photos, previous inspections), if available: Remarks: US Army Corps of Engineers Western Mountains, Valleys, and Coast – Version 2.0 Western Mountains, Valleys, and Coast Supplement to the 1987 COE Wetlands Delineation Manual Project Site: Renton 172nd Storm Water Improvements Sampling date: August 21, 2018 Applicant/Owner: Osborn Consulting Sampling Point: DP -4 Investigator: Logan Dougherty, Sam Payne City/County: Renton / King Sect., Township, Range: S 28 T 23N R 05E State: Washington Landform (hillslope, terrace, etc): Hillslope Slope (%): 2 Local relief (concave, convex, none): None Subregion (LRR): A Lat: Long: Datum: Soil Map Unit Name: Seattle Muck NWI classification: PFOC (Freshwater Forested/Shrub) Are climatic/hydrologic conditions on the site typical for this time of year? ☐ Yes ☒ No (If no, explain in remarks.) Are “Normal Circumstances” present on the site? ☒ Yes ☐ No (If needed, explain any answers in Remarks.) Are Vegetation☐, Soil ☐, or Hydrology ☐ significantly disturbed? Are Vegetation☐, Soil ☐, or Hydrology ☐ naturally problematic SUMMARY OF FINDINGS – Attach site map showing sampling point locations, transects, important features, etc. Hydrophytic Vegetation Present? Yes ☒ No ☐ Is the Sampling Point within a Wetland? Yes ☐ No ☒ Hydric Soils Present? Yes ☐ No ☒ Wetland Hydrology Present? Yes ☐ No ☒ Remarks: Drier than normal per WETS (Seattle-Tacoma International Airport) VEGETATION – Use scientific names of plants. Tree Stratum (Plot size: 5m diam.) Absolute % Cover Dominant Species? Indicator Status Dominance Test Worksheet 1. Betula nigra 40 Y FACW Number of Dominant Species that are OBL, FACW, or FAC: 3 (A) 2. 3. Total Number of Dominant Species Across All Strata: 3 (B) 4. 40 = Total Cover Percent of Dominant Species that are OBL, FACW, or FAC: 100 (A/B) Sapling/Shrub Stratum (Plot size: 3m diam.) 1. Cornus sericea 40 Y FACW Prevalence Index Worksheet 2. Populus balsamifera 5 N FAC Total % Cover of Multiply by 3. OBL species x 1 = 4. FACW species x 2 = 5. FAC species x 3 = 45 = Total Cover FACU species x 4 = UPL species x 5 = Herb Stratum (Plot size: 1m diam.) Column totals (A) (B) 1. Poaceae sp. 60 Y FAC* 2. Ranunculus repens 20 N FAC Prevalence Index = B / A = 3. Phalaris arundinacea 20 N FACW 4. Geranium robertianum 5 N FACU Hydrophytic Vegetation Indicators 5. ☒ Dominance test is > 50% 6. ☐ Prevalence test is ≤ 3.0 * 7. Morphological Adaptations * (provide supporting 8. ☐ data in remarks or on a separate sheet) 9. ☐ Wetland Non-Vascular Plants * 10. ☐ Problematic Hydrophytic Vegetation * (explain) 11. 105 = Total Cover * Indicators of hydric soil and wetland hydrology must be present, unless disturbed or problematic Woody Vine Stratum (Plot size: ) Hydrophytic Vegetation Present? Yes ☒ No ☐ 1. 2. 0 = Total Cover % Bare Ground in Herb Stratum: 0 Remarks : *Presumed indicator status DP- 4 US Army Corps of Engineers Western Mountains, Valleys, and Coast – Version 2.0 SOIL Sampling Point – DP- 4 HYDROLOGY Profile Description: (Describe to the depth needed to document the indicator or confirm the absence of indicators.) Depth Matrix Redox Features (inches) Color (moist) % Color (moist) % Type1 Loc2 Texture Remarks 0-10 10YR 2/2 Sandy loam 10-14 10YR 2/2 Gravelly sandy loam 1Type: C=Concentration, D=Depletion, RM=Reduced Matrix, CS=Covered or Coated Sand Grains 2Loc: PL=Pore Lining, M=Matrix Hydric Soil Indicators: (Applicable to all LRRs, unless otherwise noted.) Indicators for Problematic Hydric Soils3 ☐ Histosol (A1) ☐ Sandy Redox (S5) ☐ 2cm Muck (A10) ☐ Histic Epipedon (A2) ☐ Stripped Matrix (S6) ☐ Red Parent Material (TF2) ☐ Black Histic (A3) ☐ Loamy Mucky Mineral (F1) (except MLRA 1) ☐ Other (explain in remarks) ☐ Hydrogen Sulfide (A4) ☐ Loamy Gleyed Matrix (F2) ☐ ☐ Depleted Below Dark Surface (A11) ☐ Depleted Matrix (F3) ☐ Thick Dark Surface (A12) ☐ Redox Dark Surface (F6) 3 Indicators of hydrophytic vegetation and wetland hydrology must be present, unless disturbed or problematic ☐ Sandy Mucky Mineral (S1) ☐ Depleted Dark Surface (F7) ☐ Sandy Gleyed Matrix (S4) ☐ Redox Depressions (F8) Restrictive Layer (if present): Hydric soil present? Yes ☐ No ☒ Type: Depth (inches): Remarks: Wetland Hydrology Indicators: Primary Indicators (minimum of one required: check all that apply): Secondary Indicators (2 or more required): ☐ Surface water (A1) ☐ Sparsely Vegetated Concave Surface (B8) ☐ Water-Stained Leaves (B9) (MLRA 1, 2, 4A & 4B) ☐ High Water Table (A2) ☐ Water-Stained Leaves (except MLRA 1, 2, 4A & 4B) (B9) ☐ Drainage Patterns (B10) ☐ Saturation (A3) ☐ Salt Crust (B11) ☐ Dry-Season Water Table (C2) ☐ Water Marks (B1) ☐ Aquatic Invertebrates (B13) ☐ Saturation Visible on Aerial Imagery (C9) ☐ Sediment Deposits (B2) ☐ Hydrogen Sulfide Odor (C1) ☐ Geomorphic Position (D2) ☐ Drift Deposits (B3) ☐ Oxidized Rhizospheres along Living Roots (C3) ☐ Shallow Aquitard (D3) ☐ Algal Mat or Crust (B4) ☐ Presence of Reduced Iron (C4) ☐ FAC-Neutral Test (D5) ☐ Iron Deposits (B5) ☐ Recent Iron Reduction in Tilled Soils (C6) ☐ Raised Ant Mounds (D6) (LRR A) ☐ Surface Soil Cracks (B6) ☐ Stunted or Stressed Plants (D1) (LRR A) ☐ Frost-Heave Hummocks ☐ Inundation Visible on Aerial Imagery (B7) ☐ Other (explain in remarks) Field Observations Wetland Hydrology Present? Yes ☐ No ☒ Surface Water Present? Yes ☐ No ☐ Depth (in): Water Table Present? Yes ☐ No ☐ Depth (in): Saturation Present? (includes capillary fringe) Yes ☐ No ☐ Depth (in): Describe Recorded Data (stream gauge, monitoring well, aerial photos, previous inspections), if available: Remarks: US Army Corps of Engineers Western Mountains, Valleys, and Coast – Version 2.0 DP-5 Project/Site: Renton 172nd Storm Water Improvements City/County: Renton Sampling date: 5/14/19 Applicant/Owner: Osborn Consulting State: WA Sampling Point: 5 Investigator(s): L. Dougherty, G. Brennan Section, Township, Range: S28 T23N R05E Landform (hillslope, terrace, etc): Swale Local relief (concave, convex, none): Concave Slope (%): <5% Subregion (LRR): A Lat: - Long: - Datum: - Soil Map Unit Name: Alderwood gravelly loam NWI classification: None Are climatic / hydrologic conditions on the site typical for this time of year? ☒ Yes ☐ No (If no, explain in remarks.) Are Vegetation ☒, Soil ☐, or Hydrology ☐ significantly disturbed? Are “Normal Circumstances” present on the site? ☒ Yes ☐ No Are Vegetation ☐, Soil ☐, or Hydrology ☐ naturally problematic? (If needed, explain any answers in Remarks.) SUMMARY OF FINDINGS – Attach site map showing sampling point locations, transects, important features, etc. Hydrophytic Vegetation Present? Yes ☐ No ☒ Is the Sampled Area within a Wetland? Yes ☐ No ☒ Hydric Soils Present? Yes ☒ No ☐ Wetland Hydrology Present? Yes ☐ No ☒ Remarks: Ditch in-pit VEGETATION – Use scientific names of plants. Tree Stratum (Plot size: 5-m diameter) Absolute % Cover Dominant Species? Indicator Status Dominance Test worksheet: Number of Dominant Species that are OBL, FACW, or FAC: Click here to enter text. (A) 1. Populus balsamifera (rooted out) 25 N FAC 2. Alnus rubra (rooted out) 20 N FAC Total Number of Dominant Species Across all Strata: Click here to enter text. (B) 3. 4. Percent of Dominant Species that are OBL, FACW, or FAC: Click here to enter text. (A/B) 45 = Total Cover Sapling/Shrub Stratum (Plot size: 3-m diameter) Prevalence Index worksheet: 1. N/A Total % Cover of: Multiply by: 2. OBL species x 1 = 3. FACW species x 2 = 4. FAC species x 3 = 5. FACU species x 4 = 0 = Total Cover UPL species x 5 = Herb Stratum (Plot size: 1-m diameter) Column Totals: (A) (B) 1. Phalaris arudinacea <1 N FACW Prevalence Index = B/A = 2. 3. Hydrophytic Vegetation Indicators: 4. ☐ 1 – Rapid Test for Hydrophytic Vegetation 5. ☐ 2 – Dominance Test is > 50% 6. ☐ 3 – Prevalence Index is ≤ 3.01 7. ☐ 4 – Morphological Adaptations1 (Provide supporting data in Remarks or on a separate sheet) 8. 9. ☐ 5 – Wetland Non-Vascular Plants1 10. ☐ Problematic Hydrophytic Vegetation1 (Explain) 11. 1Indicators of hydric soil and wetland hydrology must be present, unless disturbed or problematic. <1 = Total Cover Woody Vine Stratum (Plot size: 3-m diameter) Hydrophytic Vegetation Present? Yes ☐ No ☒ 1. 2. 0 = Total Cover % Bare Ground in Herb Stratum: 99%* Remarks: Unvegetated swale WETLAND DETERMINATION DATA FORM – Western Mountains, Valleys, and Coast Region US Army Corps of Engineers Western Mountains, Valleys, and Coast – Version 2.0 SOIL Sampling Point: DP-5 HYDROLOGY Profile Description: (Describe to the depth needed to document the indicator or confirm the absence of indicators.) Depth Matrix Redox Features (inches) Color (moist) % Color (moist) % Type1 Loc2 Texture Remarks 0-7 10YR 2/2 100 Clay loam 7-11 2.5Y 4/1 93 10Y 3/4 7 C M Clay loam 11-16 2.5Y 6/1 95 10Y 5/4 5 C M Loamy clay 1Type: C=Concentration, D=Depletion, RM=Reduced Matrix, CS=Covered or Coated Sand Grains. 2Loc: PL=Pore Lining, M=Matrix. Hydric Soil Indicators: (Applicable to all LRRs, unless otherwise noted.) Indicators for Problematic Hydric Soils3: ☐ Histosol (A1) ☐ Sandy Redox (S5) ☐ 2cm Muck (A10) ☐ Histic Epipedon (A2) ☐ Stripped Matrix (S6) ☐ Red Parent Material (TF2) ☐ Black Histic (A3) ☐ Loamy Mucky Mineral (F1) (except MLRA 1) ☐ Very Shallow Dark Surface (TF12) ☐ Hydrogen Sulfide (A4) ☐ Loamy Gleyed Matrix (F2) ☐ Other (Explain in Remarks) ☐ Depleted Below Dark Surface (A11) ☒ Depleted Matrix (F3) ☐ Thick Dark Surface (A12) ☐ Redox Dark Surface (F6) 3 Indicators of hydrophytic vegetation and wetland hydrology must be present, unless disturbed or problematic. ☐ Sandy Mucky Mineral (S1) ☐ Depleted Dark Surface (F7) ☐ Sandy Gleyed Matrix (S4) ☐ Redox Depressions (F8) Restrictive Layer (if present): Hydric soil present? Yes ☒ No ☐ Type: Depth (inches): Remarks: Wetland Hydrology Indicators: Primary Indicators (minimum of one required: check all that apply) Secondary Indicators (2 or more required) ☐ Surface water (A1) ☐ Water-Stained Leaves (except MLRA 1, 2, 4A & 4B) (B9) ☐ Water-Stained Leaves (B9) (MLRA 1, 2, 4A & 4B) ☐ High Water Table (A2) ☐ Saturation (A3) ☐ Salt Crust (B11) ☒ Drainage Patterns (B10) ☐ Water Marks (B1) ☐ Aquatic Invertebrates (B13) ☐ Dry-Season Water Table (C2) ☐ Sediment Deposits (B2) ☐ Hydrogen Sulfide Odor (C1) ☐ Saturation Visible on Aerial Imagery (C9) ☐ Drift Deposits (B3) ☐ Oxidized Rhizospheres along Living Roots (C3) ☐ Geomorphic Position (D2) ☐ Algal Mat or Crust (B4) ☐ Presence of Reduced Iron (C4) ☐ Shallow Aquitard (D3) ☐ Iron Deposits (B5) ☐ Recent Iron Reduction in Tilled Soils (C6) ☐ FAC-Neutral Test (D5) ☐ Surface Soil Cracks (B6) ☐ Stunted or Stressed Plants (D1) (LRR A) ☐ Raised Ant Mounds (D6) (LRR A) ☐ Inundation Visible on Aerial Imagery (B7) ☐ Other (explain in remarks) ☐ Frost-Heave Hummocks ☐ Sparsely Vegetated Concave Surface (B8) Field Observations: Wetland Hydrology Present? Yes ☐ No ☒ Surface Water Present? Yes ☐ No ☒ Depth (in): Water Table Present? Yes ☐ No ☒ Depth (in): Saturation Present? Yes ☐ No ☒ Depth (in): (includes capillary fringe) Describe Recorded Data (stream gauge, monitoring well, aerial photos, previous inspections), if available: Remarks: Soil damp but not saturated to 16 inches. Some algae present, not enough to be described as an algal mat. US Army Corps of Engineers Western Mountains, Valleys, and Coast – Version 2.0 DP-6 Project/Site: Renton 172nd City/County: Renton Sampling date: 5/14/19 Applicant/Owner: Osborn Consulting State: WA Sampling Point: 6 Investigator(s): L. Dougherty, G. Brennan Section, Township, Range: S28 T23N R05E Landform (hillslope, terrace, etc): Berm Local relief (concave, convex, none): Convex Slope (%): <1% Subregion (LRR): A Lat: - Long: - Datum: - Soil Map Unit Name: Alderwood gravelly loam NWI classification: None Are climatic / hydrologic conditions on the site typical for this time of year? ☒ Yes ☐ No (If no, explain in remarks.) Are Vegetation ☐, Soil ☐, or Hydrology ☐ significantly disturbed? Are “Normal Circumstances” present on the site? ☒ Yes ☐ No Are Vegetation ☐, Soil ☐, or Hydrology ☐ naturally problematic? (If needed, explain any answers in Remarks.) SUMMARY OF FINDINGS – Attach site map showing sampling point locations, transects, important features, etc. Hydrophytic Vegetation Present? Yes ☒ No ☐ Is the Sampled Area within a Wetland? Yes ☐ No ☒ Hydric Soils Present? Yes ☐ No ☒ Wetland Hydrology Present? Yes ☐ No ☒ Remarks: Click here to enter text. VEGETATION – Use scientific names of plants. Tree Stratum (Plot size: 5-m diameter) Absolute % Cover Dominant Species? Indicator Status Dominance Test worksheet: Number of Dominant Species that are OBL, FACW, or FAC: 3 (A) 1. Thuja plicata 45 N FAC 2. Populus balsamifera 80 Y FAC Total Number of Dominant Species Across all Strata: 3 (B) 3. Alnus rubra 80 Y FAC 4. Percent of Dominant Species that are OBL, FACW, or FAC: 100 (A/B) = Total Cover Sapling/Shrub Stratum (Plot size: 3-m diameter) Prevalence Index worksheet: 1. Rubus armeniacus 45 Y FAC Total % Cover of: Multiply by: 2. Cornus sericea 40 Y FACW OBL species x 1 = 3. FACW species x 2 = 4. FAC species x 3 = 5. FACU species x 4 = 85 = Total Cover UPL species x 5 = Herb Stratum (Plot size: 1-m diameter) Column Totals: (A) (B) 1. Ranunculus repens 5 N FAC Prevalence Index = B/A = 2. Equisetum telmateia 1 N FACW 3. Hydrophytic Vegetation Indicators: 4. ☐ 1 – Rapid Test for Hydrophytic Vegetation 5. ☒ 2 – Dominance Test is > 50% 6. ☐ 3 – Prevalence Index is ≤ 3.01 7. ☐ 4 – Morphological Adaptations1 (Provide supporting data in Remarks or on a separate sheet) 8. 9. ☐ 5 – Wetland Non-Vascular Plants1 10. ☐ Problematic Hydrophytic Vegetation1 (Explain) 11. 1Indicators of hydric soil and wetland hydrology must be present, unless disturbed or problematic. 6 = Total Cover Woody Vine Stratum (Plot size: 3-m diameter) Hydrophytic Vegetation Present? Yes ☒ No ☐ 1. 2. 0 = Total Cover % Bare Ground in Herb Stratum: 94 Remarks: Bare ground is mostly covered in leaves and duff WETLAND DETERMINATION DATA FORM – Western Mountains, Valleys, and Coast Region US Army Corps of Engineers Western Mountains, Valleys, and Coast – Version 2.0 SOIL Sampling Point: DP-6 HYDROLOGY Profile Description: (Describe to the depth needed to document the indicator or confirm the absence of indicators.) Depth Matrix Redox Features (inches) Color (moist) % Color (moist) % Type1 Loc2 Texture Remarks 0-16 10YR 2/2 100 Gravelly loam 1Type: C=Concentration, D=Depletion, RM=Reduced Matrix, CS=Covered or Coated Sand Grains . 2Loc: PL=Pore Lining, M=Matrix. Hydric Soil Indicators: (Applicable to all LRRs, unless otherwise noted.) Indicators for Problematic Hydric Soils3: ☐ Histosol (A1) ☐ Sandy Redox (S5) ☐ 2cm Muck (A10) ☐ Histic Epipedon (A2) ☐ Stripped Matrix (S6) ☐ Red Parent Material (TF2) ☐ Black Histic (A3) ☐ Loamy Mucky Mineral (F1) (except MLRA 1) ☐ Very Shallow Dark Surface (TF12) ☐ Hydrogen Sulfide (A4) ☐ Loamy Gleyed Matrix (F2) ☐ Other (Explain in Remarks) ☐ Depleted Below Dark Surface (A11) ☐ Depleted Matrix (F3) ☐ Thick Dark Surface (A12) ☐ Redox Dark Surface (F6) 3 Indicators of hydrophytic vegetation and wetland hydrology must be present, unless disturbed or problematic. ☐ Sandy Mucky Mineral (S1) ☐ Depleted Dark Surface (F7) ☐ Sandy Gleyed Matrix (S4) ☐ Redox Depressions (F8) Restrictive Layer (if present): Hydric soil present? Yes ☐ No ☒ Type: Depth (inches): Remarks: Wetland Hydrology Indicators: Primary Indicators (minimum of one required: check all that apply) Secondary Indicators (2 or more required) ☐ Surface water (A1) ☐ Water-Stained Leaves (except MLRA 1, 2, 4A & 4B) (B9) ☐ Water-Stained Leaves (B9) (MLRA 1, 2, 4A & 4B) ☐ High Water Table (A2) ☐ Saturation (A3) ☐ Salt Crust (B11) ☐ Drainage Patterns (B10) ☐ Water Marks (B1) ☐ Aquatic Invertebrates (B13) ☐ Dry-Season Water Table (C2) ☐ Sediment Deposits (B2) ☐ Hydrogen Sulfide Odor (C1) ☐ Saturation Visible on Aerial Imagery (C9) ☐ Drift Deposits (B3) ☐ Oxidized Rhizospheres along Living Roots (C3) ☐ Geomorphic Position (D2) ☐ Algal Mat or Crust (B4) ☐ Presence of Reduced Iron (C4) ☐ Shallow Aquitard (D3) ☐ Iron Deposits (B5) ☐ Recent Iron Reduction in Tilled Soils (C6) ☐ FAC-Neutral Test (D5) ☐ Surface Soil Cracks (B6) ☐ Stunted or Stressed Plants (D1) (LRR A) ☐ Raised Ant Mounds (D6) (LRR A) ☐ Inundation Visible on Aerial Imagery (B7) ☐ Other (explain in remarks) ☐ Frost-Heave Hummocks ☐ Sparsely Vegetated Concave Surface (B8) Field Observations: Wetland Hydrology Present? Yes ☐ No ☒ Surface Water Present? Yes ☐ No ☒ Depth (in): Water Table Present? Yes ☐ No ☒ Depth (in): Saturation Present? Yes ☐ No ☒ Depth (in): (includes capillary fringe) Describe Recorded Data (stream gauge, monitoring well, aerial photos, previous inspections), if available: Remarks: Moist but not saturated to 16 inches. Wetland Rating System for Western WA: 2014 Update Rating Form – Effective January 1, 2015 1 Wetland name or number: Wetland A RATING SUMMARY – Western Washington Name of wetland (or ID #): Wetland A Date of site visit: August 21, 2018 Rated by: Sam Payne, Logan Dougherty Trained by Ecology? ☒Y ☐N Date of training: June 2017 HGM Class used for rating: Depressional Wetland has multiple HGM classes? ☐Y ☒N NOTE: Form is not complete without the figures requested (figures can be combined). Source of base aerial photo/map: King County iMap, Bing Maps OVERALL WETLAND CATEGORY (based on functions ☒ or special characteristics ☐) 1. Category of wetland based on FUNCTIONS ☐ Category I – Total score = 23 - 27 ☒ Category II – Total score = 20 - 22 ☐ Category III – Total score = 16 - 19 ☐ Category IV – Total score = 9 - 15 FUNCTION Improving Water Quality Hydrologic Habitat Circle the appropriate ratings Site Potential H M L H M L H M L Landscape Potential H M L H M L H M L Value H M L H M L H M L TOTAL Score Based on Ratings 9 7 6 22 2. Category based on SPECIAL CHARACTERISTICS of wetland CHARACTERISTIC CATEGORY Estuarine I II Wetland of High Conservation Value I Bog I Mature Forest I Old Growth Forest I Coastal Lagoon I II Interdunal I II III IV None of the above ☒ Score for each function based on three ratings (order of ratings is not important) 9 = H,H,H 8 = H,H,M 7 = H,H,L 7 = H,M,M 6 = H,M,L 6 = M,M,M 5 = H,L,L 5 = M,M,L 4 = M,L,L 3 = L,L,L Wetland Rating System for Western WA: 2014 Update Rating Form – Effective January 1, 2015 2 Wetland name or number: Wetland A Maps and figures required to answer questions correctly for Western Washington Depressional Wetlands Map of: To answer questions: Figure # Cowardin plant classes D 1.3, H 1.1, H 1.4 1 Hydroperiods D 1.4, H 1.2 2 Location of outlet (can be added to map of hydroperiods) D 1.1, D 4.1 2 Boundary of area within 150 ft of the wetland (can be added to another figure) D 2.2, D 5.2 2 Map of the contributing basin D 4.3, D 5.3 3 1 km Polygon: Area that extends 1 km from entire wetland edge - including polygons for accessible habitat and undisturbed habitat H 2.1, H 2.2, H 2.3 6 Screen capture of map of 303(d) listed waters in basin (from Ecology website) D 3.1, D 3.2 7 Screen capture of list of TMDLs for WRIA in which unit is found (from web) D 3.3 8 Wetland Rating System for Western WA: 2014 Update Rating Form – Effective January 1, 2015 3 Wetland name or number: Wetland A HGM Classification of Wetlands in Western Washington 1. Are the water levels in the entire unit usually controlled by tides except during floods? ☒NO – go to 2 ☐YES – the wetland class is Tidal Fringe – go to 1.1 1.1 Is the salinity of the water during periods of annual low flow below 0.5 ppt (parts per thousand)? NO – Saltwater Tidal Fringe (Estuarine) YES – Freshwater Tidal Fringe If your wetland can be classified as a Freshwater Tidal Fringe use the forms for Riverine wetlands. If it is Saltwater Tidal Fringe it is an Estuarine wetland and is not scored. This method cannot be used to score functions for estuarine wetlands. 2. The entire wetland unit is flat and precipitation is the only source (>90%) of water to it. Groundwater and surface water runoff are NOT sources of water to the unit. ☒NO – go to 3 ☐YES – The wetland class is Flats If your wetland can be classified as a Flats wetland, use the form for Depressional wetlands. 3. Does the entire wetland unit meet all of the following criteria? ☐The vegetated part of the wetland is on the shores of a body of permanent open water (without any plants on the surface at any time of the year) at least 20 ac (8 ha) in size; ☐At least 30% of the open water area is deeper than 6.6 ft (2 m). ☒NO – go to 4 ☐YES – The wetland class is Lake Fringe (Lacustrine Fringe) 4. Does the entire wetland unit meet all of the following criteria? ☐The wetland is on a slope (slope can be very gradual), ☐The water flows through the wetland in one direction (unidirectional) and usually comes from seeps. It may flow subsurface, as sheetflow, or in a swale without distinct banks, ☐The water leaves the wetland without being impounded. ☒NO – go to 5 ☐YES – The wetland class is Slope NOTE: Surface water does not pond in these type of wetlands except occasionally in very small and shallow depressions or behind hummocks (depressions are usually <3 ft diameter and less than 1 ft deep). 5. Does the entire wetland unit meet all of the following criteria? ☐The unit is in a valley, or stream channel, where it gets inundated by overbank flooding from that stream or river, ☐The overbank flooding occurs at least once every 2 years. For questions 1-7, the criteria described must apply to the entire unit being rated. If the hydrologic criteria listed in each question do not apply to the entire unit being rated, you probably have a unit with multiple HGM classes. In this case, identify which hydrologic criteria in questions 1-7 apply, and go to Question 8. Wetland Rating System for Western WA: 2014 Update Rating Form – Effective January 1, 2015 4 Wetland name or number: Wetland A ☒NO – go to 6 ☐YES – The wetland class is Riverine NOTE: The Riverine unit can contain depressions that are filled with water when the river is not flooding 6. Is the entire wetland unit in a topographic depression in which water ponds, or is saturated to the surface, at some time during the year? This means that any outlet, if present, is higher than the interior of the wetland. ☐NO – go to 7 ☒YES – The wetland class is Depressional 7. Is the entire wetland unit located in a very flat area with no obvious depression and no overbank flooding? The unit does not pond surface water more than a few inches. The unit seems to be maintained by high groundwater in the area. The wetland may be ditched, but has no obvious natural outlet. ☐NO – go to 8 ☐YES – The wetland class is Depressional 8. Your wetland unit seems to be difficult to classify and probably contains several different HGM classes. For example, seeps at the base of a slope may grade into a riverine floodplain, or a small stream within a Depressional wetland has a zone of flooding along its sides. GO BACK AND IDENTIFY WHICH OF THE HYDROLOGIC REGIMES DESCRIBED IN QUESTIONS 1-7 APPLY TO DIFFERENT AREAS IN THE UNIT (make a rough sketch to help you decide). Use the following table to identify the appropriate class to use for the rating system if you have several HGM classes present within the wetland unit being scored. NOTE: Use this table only if the class that is recommended in the second column represents 10% or more of the total area of the wetland unit being rated. If the area of the HGM class listed in column 2 is less than 10% of the unit; classify the wetland using the class that represents more than 90% of the total area. HGM classes within the wetland unit being rated HGM class to use in rating Slope + Riverine Riverine Slope + Depressional Depressional Slope + Lake Fringe Lake Fringe Depressional + Riverine along stream within boundary of depression Depressional Depressional + Lake Fringe Depressional Riverine + Lake Fringe Riverine Salt Water Tidal Fringe and any other class of freshwater wetland Treat as ESTUARINE If you are still unable to determine which of the above criteria apply to your wetland, or if you have more than 2 HGM classes within a wetland boundary, classify the wetland as Depressional for the rating. Wetland Rating System for Western WA: 2014 Update Rating Form – Effective January 1, 2015 5 Wetland name or number: Wetland A DEPRESSIONAL AND FLATS WETLANDS Water Quality Functions - Indicators that the site functions to improve water quality D 1.0. Does the site have the potential to improve water quality? D 1.1. Characteristics of surface water outflows from the wetland: ☐ Wetland is a depression or flat depression (QUESTION 7 on key) with no surface water leaving it (no outlet). points = 3 ☐ Wetland has an intermittently flowing stream or ditch, OR highly constricted permanently flowing outlet. points = 2 ☒ Wetland has an unconstricted, or slightly constricted, surface outlet that is permanently flowing. points = 1 ☐ Wetland is a flat depression (QUESTION 7 on key), whose outlet is a permanently flowing ditch. points = 1 1 D 1.2. The soil 2 in below the surface (or duff layer) is true clay or true organic (use NRCS definitions).☒Yes = 4 ☐No = 0 4 D 1.3. Characteristics and distribution of persistent plants (Emergent, Scrub-shrub, and/or Forested Cowardin classes): ☒ Wetland has persistent, ungrazed, plants > 95% of area points = 5 ☐ Wetland has persistent, ungrazed, plants > 1/2 of area points = 3 ☐ Wetland has persistent, ungrazed plants > 1/10 of area points = 1 ☐ Wetland has persistent, ungrazed plants < 1/10 of area points = 0 5 D 1.4. Characteristics of seasonal ponding or inundation: This is the area that is ponded for at least 2 months. See description in manual. ☒ Area seasonally ponded is > ½ total area of wetland points = 4 ☐ Area seasonally ponded is > ¼ total area of wetland points = 2 ☐ Area seasonally ponded is < ¼ total area of wetland points = 0 4 Total for D 1 Add the points in the boxes above 14 Rating of Site Potential If score is: ☒12-16 = H ☐6-11 = M ☐0-5 = L Record the rating on the first page D 2.0. Does the landscape have the potential to support the water quality function of the site? D 2.1. Does the wetland unit receive stormwater discharges? ☒Yes = 1 ☐No = 0 1 D 2.2. Is > 10% of the area within 150 ft of the wetland in land uses that generate pollutants? ☒Yes = 1 ☐No = 0 1 D 2.3. Are there septic systems within 250 ft of the wetland? ☒Yes = 1 ☐No = 0 1 D 2.4. Are there other sources of pollutants coming into the wetland that are not listed in questions D 2.1-D 2.3? Source: Click here to enter text. ☐Yes = 1 ☒No = 0 0 Total for D 2 Add the points in the boxes above 3 Rating of Landscape Potential If score is: ☒3 or 4 = H ☐1 or 2 = M ☐0 = L Record the rating on the first page D 3.0. Is the water quality improvement provided by the site valuable to society? D 3.1. Does the wetland discharge directly (i.e., within 1 mi) to a stream, river, lake, or marine water that is on the 303(d) list? ☐Yes = 1 ☒No = 0 0 D 3.2. Is the wetland in a basin or sub-basin where an aquatic resource is on the 303(d) list? ☒Yes = 1 ☐No = 0 1 D 3.3. Has the site been identified in a watershed or local plan as important for maintaining water quality (answer YES if there is a TMDL for the basin in which the unit is found)? ☒Yes = 2 ☐No = 0 2 Total for D 3 Add the points in the boxes above 3 Rating of Value If score is: ☒2-4 = H ☐1 = M ☐0 = L Record the rating on the first page Wetland Rating System for Western WA: 2014 Update Rating Form – Effective January 1, 2015 6 Wetland name or number: Wetland A DEPRESSIONAL AND FLATS WETLANDS Hydrologic Functions - Indicators that the site functions to reduce flooding and stream degradation D 4.0. Does the site have the potential to reduce flooding and erosion? D 4.1. Characteristics of surface water outflows from the wetland: ☐ Wetland is a depression or flat depression with no surface water leaving it (no outlet). points = 4 ☐ Wetland has an intermittently flowing stream or ditch, OR highly constricted permanently flowing outlet. points = 2 ☐ Wetland is a flat depression (QUESTION 7 on key), whose outlet is a permanently flowing ditch. points = 1 ☒ Wetland has an unconstricted, or slightly constricted, surface outlet that is permanently flowing. points = 0 0 D 4.2. Depth of storage during wet periods: Estimate the height of ponding above the bottom of the outlet. For wetlands with no outlet, measure from the surface of permanent water or if dry, the deepest part. ☐ Marks of ponding are 3 ft or more above the surface or bottom of outlet. points = 7 ☐ Marks of ponding between 2 ft to < 3 ft from surface or bottom of outlet. points = 5 ☒ Marks are at least 0.5 ft to < 2 ft from surface or bottom of outlet. points = 3 ☐ The wetland is a “headwater” wetland. points = 3 ☐ Wetland is flat but has small depressions on the surface that trap water. points = 1 ☐ Marks of ponding less than 0.5 ft (6 in). points = 0 3 D 4.3. Contribution of the wetland to storage in the watershed: Estimate the ratio of the area of upstream basin contributing surface water to the wetland to the area of the wetland unit itself. ☐ The area of the basin is less than 10 times the area of the unit. points = 5 ☒ The area of the basin is 10 to 100 times the area of the unit. points = 3 ☐ The area of the basin is more than 100 times the area of the unit. points = 0 ☐ Entire wetland is in the Flats class. points = 5 3 Total for D 4 Add the points in the boxes above 6 Rating of Site Potential If score is: ☐12-16 = H ☒6-11 = M ☐0-5 = L Record the rating on the first page D 5.0. Does the landscape have the potential to support hydrologic functions of the site? D 5.1. Does the wetland receive stormwater discharges? ☒Yes = 1 ☐No = 0 1 D 5.2. Is >10% of the area within 150 ft of the wetland in land uses that generate excess runoff? ☒Yes = 1 ☐No = 0 1 D 5.3. Is more than 25% of the contributing basin of the wetland covered with intensive human land uses (residential at >1 residence/ac, urban, commercial, agriculture, etc.)? ☒Yes = 1 ☐No = 0 1 Total for D 5 Add the points in the boxes above 3 Rating of Landscape Potential If score is: ☒3 = H ☐1 or 2 = M ☐0 = L Record the rating on the first page D 6.0. Are the hydrologic functions provided by the site valuable to society? D 6.1. The unit is in a landscape that has flooding problems. Choose the description that best matches conditions around the wetland unit being rated. Do not add points. Choose the highest score if more than one condition is met. The wetland captures surface water that would otherwise flow down-gradient into areas where flooding has damaged human or natural resources (e.g., houses or salmon redds): ☐ Flooding occurs in a sub-basin that is immediately down-gradient of unit. points = 2 ☒ Surface flooding problems are in a sub-basin farther down-gradient. points = 1 ☐ Flooding from groundwater is an issue in the sub-basin. points = 1 ☐ The existing or potential outflow from the wetland is so constrained by human or natural conditions that the water stored by the wetland cannot reach areas that flood. Explain why: …. points = 0 ☐There are no problems with flooding downstream of the wetland. points = 0 1 D 6.2. Has the site been identified as important for flood storage or flood conveyance in a regional flood control plan? ☐Yes = 2 ☒No = 0 0 Total for D 6 Add the points in the boxes above 1 Rating of Value If score is: ☐2-4 = H ☒1 = M ☐0 = L Record the rating on the first page Wetland name or number: Wetland A Wetland Rating System for Western WA: 2014 Update Rating Form – Effective January 1, 2015 7 These questions apply to wetlands of all HGM classes. HABITAT FUNCTIONS - Indicators that site functions to provide important habitat H 1.0. Does the site have the potential to provide habitat? H 1.1. Structure of plant community: Indicators are Cowardin classes and strata within the Forested class. Check the Cowardin plant classes in the wetland. Up to 10 patches may be combined for each class to meet the threshold of ¼ ac or more than 10% of the unit if it is smaller than 2.5 ac. Add the number of structures checked. ☐ Aquatic bed 4 structures or more: points = 4 ☐ Emergent 3 structures: points = 2 ☐ Scrub-shrub (areas where shrubs have > 30% cover) 2 structures: points = 1 ☒ Forested (areas where trees have > 30% cover) 1 structure: points = 0 If the unit has a Forested class, check if: ☒ The Forested class has 3 out of 5 strata (canopy, sub-canopy, shrubs, herbaceous, moss/ground-cover) that each cover 20% within the Forested polygon 1 H 1.2. Hydroperiods Check the types of water regimes (hydroperiods) present within the wetland. The water regime has to cover more than 10% of the wetland or ¼ ac to count (see text for descriptions of hydroperiods). ☒ Permanently flooded or inundated 4 or more types present: points = 3 ☒ Seasonally flooded or inundated 3 types present: points = 2 ☐ Occasionally flooded or inundated 2 types present: points = 1 ☒ Saturated only 1 type present: points = 0 ☐ Permanently flowing stream or river in, or adjacent to, the wetland ☐ Seasonally flowing stream in, or adjacent to, the wetland ☐ Lake Fringe wetland 2 points ☐ Freshwater tidal wetland 2 points 2 H 1.3. Richness of plant species Count the number of plant species in the wetland that cover at least 10 ft2. Different patches of the same species can be combined to meet the size threshold and you do not have to name the species. Do not include Eurasian milfoil, reed canarygrass, purple loosestrife, Canadian thistle If you counted: ☒ > 19 species points = 2 ☐ 5 - 19 species points = 1 ☐ < 5 species points = 0 2 H 1.4. Interspersion of habitats Decide from the diagrams below whether interspersion among Cowardin plants classes (described in H 1.1), or the classes and unvegetated areas (can include open water or mudflats) is high, moderate, low, or none. If you have four or more plant classes or three classes and open water, the rating is always high. ☒ None = 0 points ☐ Low = 1 point ☐ Moderate = 2 points All three diagrams in this row are ☐ HIGH = 3points 0 Wetland name or number: Wetland A Wetland Rating System for Western WA: 2014 Update Rating Form – Effective January 1, 2015 8 H 1.5. Special habitat features: Check the habitat features that are present in the wetland. The number of checks is the number of points. ☒ Large, downed, woody debris within the wetland (> 4 in diameter and 6 ft long). ☒ Standing snags (dbh > 4 in) within the wetland. ☒ Undercut banks are present for at least 6.6 ft (2 m) AND/OR overhanging plants extends at least 3.3 ft (1 m) over a stream (or ditch) in, or contiguous with the wetland, for at least 33 ft (10 m). ☐ Stable steep banks of fine material that might be used by beaver or muskrat for denning (> 30 degree slope) OR signs of recent beaver activity are present (cut shrubs or trees that have not yet weathered where wood is exposed). ☒ At least ¼ ac of thin-stemmed persistent plants or woody branches are present in areas that are permanently or seasonally inundated (structures for egg-laying by amphibians). ☒ Invasive plants cover less than 25% of the wetland area in every stratum of plants (see H 1.1 for list of strata). 5 Total for H 1 Add the points in the boxes above 10 Rating of Site Potential If score is: ☐15-18 = H ☒7-14 = M ☐0-6 = L Record the rating on the first page H 2.0. Does the landscape have the potential to support the habitat functions of the site? H 2.1. Accessible habitat (include only habitat that directly abuts wetland unit). Calculate: % undisturbed habitat + [(%moderate and low intensity land uses)/2] = 1% + (0%/2) = 0.5% If total accessible habitat is: ☐ > 1/3 (33.3%) of 1 km Polygon points = 3 ☐ 20-33% of 1 km Polygon points = 2 ☐ 10-19% of 1 km Polygon points = 1 ☐ < 10% of 1 km Polygon points = 0 0 H 2.2. Undisturbed habitat in 1 km Polygon around the wetland. Calculate: % undisturbed habitat + [(%moderate and low intensity land uses)/2 = 35% + (4%/2) = 37% ☐ Undisturbed habitat > 50% of Polygon points = 3 ☐ Undisturbed habitat 10-50% and in 1-3 patches points = 2 ☐ Undisturbed habitat 10-50% and > 3 patches points = 1 ☐ Undisturbed habitat < 10% of 1 km Polygon points = 0 2 H 2.3. Land use intensity in 1 km Polygon: If ☒ > 50% of 1 km Polygon is high intensity land use points = (- 2) ☐ ≤ 50% of 1 km Polygon is high intensity points = 0 -2 Total for H 2 Add the points in the boxes above 0 Rating of Landscape Potential If score is: ☐4-6 = H ☐1-3 = M ☒< 1 = L Record the rating on the first page H 3.0. Is the habitat provided by the site valuable to society? H 3.1. Does the site provide habitat for species valued in laws, regulations, or policies? Choose only the highest score that applies to the wetland being rated. Site meets ANY of the following criteria: points = 2 ☒ It has 3 or more priority habitats within 100 m (see next page) ☐ It provides habitat for Threatened or Endangered species (any plant or animal on the state or federal lists) ☐ It is mapped as a location for an individual WDFW priority species ☐ It is a Wetland of High Conservation Value as determined by the Department of Natural Resources ☐ It has been categorized as an important habitat site in a local or regional comprehensive plan, in a Shoreline Master Plan, or in a watershed plan ☐ Site has 1 or 2 priority habitats (listed on next page) within 100 m points = 1 ☐ Site does not meet any of the criteria above points = 0 2 Rating of Value If score is: ☒2 = H ☐1 = M ☐0 = L Record the rating on the first page Wetland name or number: Wetland A Wetland Rating System for Western WA: 2014 Update Rating Form – Effective January 1, 2015 9 WDFW Priority Habitats Priority habitats listed by WDFW (see complete descriptions of WDFW priority habitats, and the counties in which they can be found, in: Washington Department of Fish and Wildlife. 2008. Priority Habitat and Species List. Olympia, Washington. 177 pp. http://wdfw.wa.gov/publications/00165/wdfw00165.pdf or access the list from here: http://wdfw.wa.gov/conservation/phs/list/) Count how many of the following priority habitats are within 330 ft (100 m) of the wetland unit: NOTE: This question is independent of the land use between the wetland unit and the priority habitat. ☐ Aspen Stands: Pure or mixed stands of aspen greater than 1 ac (0.4 ha). ☐ Biodiversity Areas and Corridors: Areas of habitat that are relatively important to various species of native fish and wildlife (full descriptions in WDFW PHS report). ☐ Herbaceous Balds: Variable size patches of grass and forbs on shallow soils over bedrock. ☐ Old-growth/Mature forests: Old-growth west of Cascade crest – Stands of at least 2 tree species, forming a multi- layered canopy with occasional small openings; with at least 8 trees/ac (20 trees/ha ) > 32 in (81 cm) dbh or > 200 years of age. Mature forests – Stands with average diameters exceeding 21 in (53 cm) dbh; crown cover may be less than 100%; decay, decadence, numbers of snags, and quantity of large downed material is generally less than that found in old-growth; 80-200 years old west of the Cascade crest. ☐ Oregon White Oak: Woodland stands of pure oak or oak/conifer associations where canopy coverage of the oak component is important (full descriptions in WDFW PHS report p. 158 – see web link above). ☒ Riparian: The area adjacent to aquatic systems with flowing water that contains elements of both aquatic and terrestrial ecosystems which mutually influence each other. ☐ Westside Prairies: Herbaceous, non-forested plant communities that can either take the form of a dry prairie or a wet prairie (full descriptions in WDFW PHS report p. 161 – see web link above). ☒ Instream: The combination of physical, biological, and chemical processes and conditions that interact to provide functional life history requirements for instream fish and wildlife resources. ☐ Nearshore: Relatively undisturbed nearshore habitats. These include Coastal Nearshore, Open Coast Nearshore, and Puget Sound Nearshore. (full descriptions of habitats and the definition of relatively undisturbed are in WDFW report – see web link on previous page). ☐ Caves: A naturally occurring cavity, recess, void, or system of interconnected passages under the earth in soils, rock, ice, or other geological formations and is large enough to contain a human. ☐ Cliffs: Greater than 25 ft (7.6 m) high and occurring below 5000 ft elevation. ☐ Talus: Homogenous areas of rock rubble ranging in average size 0.5 - 6.5 ft (0.15 - 2.0 m), composed of basalt, andesite, and/or sedimentary rock, including riprap slides and mine tailings. May be associated with cliffs. ☒ Snags and Logs: Trees are considered snags if they are dead or dying and exhibit sufficient decay characteristics to enable cavity excavation/use by wildlife. Priority snags have a diameter at breast height of > 20 in (51 cm) in western Washington and are > 6.5 ft (2 m) in height. Priority logs are > 12 in (30 cm) in diameter at the largest end, and > 20 ft (6 m) long. Note: All vegetated wetlands are by definition a priority habitat but are not included in this list because they are addressed elsewhere. Wetland name or number: Wetland A Wetland Rating System for Western WA: 2014 Update Rating Form – Effective January 1, 2015 10 CATEGORIZATION BASED ON SPECIAL CHARACTERISTICS Wetland Type Check off any criteria that apply to the wetland. Circle the category when the appropriate criteria are met. Category SC 1.0. Estuarine wetlands Does the wetland meet the following criteria for Estuarine wetlands? ☐ The dominant water regime is tidal, ☐ Vegetated, and ☐ With a salinity greater than 0.5 ppt ☐Yes –Go to SC 1.1 ☒No= Not an estuarine wetland SC 1.1. Is the wetland within a National Wildlife Refuge, National Park, National Estuary Reserve, Natural Area Preserve, State Park or Educational, Environmental, or Scientific Reserve designated under WAC 332-30-151? ☐Yes = Category I ☐No - Go to SC 1.2 Cat. I SC 1.2. Is the wetland unit at least 1 ac in size and meets at least two of the following three conditions? ☐ The wetland is relatively undisturbed (has no diking, ditching, filling, cultivation, grazing, and has less than 10% cover of non-native plant species. (If non-native species are Spartina, see page 25) ☐ At least ¾ of the landward edge of the wetland has a 100 ft buffer of shrub, forest, or un-grazed or un- mowed grassland. ☐ The wetland has at least two of the following features: tidal channels, depressions with open water, or contiguous freshwater wetlands. ☐Yes = Category I ☐No= Category II Cat. I Cat. II SC 2.0. Wetlands of High Conservation Value (WHCV) SC 2.1. Has the WA Department of Natural Resources updated their website to include the list of Wetlands of High Conservation Value? ☒Yes – Go to SC 2.2 ☐No – Go to SC 2.3 SC 2.2. Is the wetland listed on the WDNR database as a Wetland of High Conservation Value? http://www.dnr.wa.gov/NHPwetlandviewer ☐Yes = Category I ☒No = Not a WHCV SC 2.3. Is the wetland in a Section/Township/Range that contains a Natural Heritage wetland? http://file.dnr.wa.gov/publications/amp_nh_wetlands_trs.pdf ☐Yes – Contact WNHP/WDNR and go to SC 2.4 ☐No = Not a WHCV SC 2.4. Has WDNR identified the wetland within the S/T/R as a Wetland of High Conservation Value and listed it on their website? ☐Yes = Category I ☐No = Not a WHCV Cat. I SC 3.0. Bogs Does the wetland (or any part of the unit) meet both the criteria for soils and vegetation in bogs? Use the key below. If you answer YES you will still need to rate the wetland based on its functions. SC 3.1. Does an area within the wetland unit have organic soil horizons, either peats or mucks, that compose 16 in or more of the first 32 in of the soil profile? ☐Yes – Go to SC 3.3 ☒No – Go to SC 3.2 SC 3.2. Does an area within the wetland unit have organic soils, either peats or mucks, that are less than 16 in deep over bedrock, or an impermeable hardpan such as clay or volcanic ash, or that are floating on top of a lake or pond? ☐Yes – Go to SC 3.3 ☒No = Is not a bog SC 3.3. Does an area with peats or mucks have more than 70% cover of mosses at ground level, AND at least a 30% cover of plant species listed in Table 4? ☐Yes = Is a Category I bog ☐No – Go to SC 3.4 NOTE: If you are uncertain about the extent of mosses in the understory, you may substitute that criterion by measuring the pH of the water that seeps into a hole dug at least 16 in deep. If the pH is less than 5.0 and the plant species in Table 4 are present, the wetland is a bog. SC 3.4. Is an area with peats or mucks forested (> 30% cover) with Sitka spruce, subalpine fir, western red cedar, western hemlock, lodgepole pine, quaking aspen, Engelmann spruce, or western white pine, AND any of the species (or combination of species) listed in Table 4 provide more than 30% of the cover under the canopy? ☐Yes = Is a Category I bog ☐No = Is not a bog Cat. I Wetland name or number: Wetland A Wetland Rating System for Western WA: 2014 Update Rating Form – Effective January 1, 2015 11 SC 4.0. Forested Wetlands Does the wetland have at least 1 contiguous acre of forest that meets one of these criteria for the WA Department of Fish and Wildlife’s forests as priority habitats? If you answer YES you will still need to rate the wetland based on its functions. ☐ Old-growth forests (west of Cascade crest): Stands of at least two tree species, forming a multi-layered canopy with occasional small openings; with at least 8 trees/ac (20 trees/ha) that are at least 200 years of age OR have a diameter at breast height (dbh) of 32 in (81 cm) or more. ☐ Mature forests (west of the Cascade Crest): Stands where the largest trees are 80- 200 years old OR the species that make up the canopy have an average diameter (dbh) exceeding 21 in (53 cm). ☐Yes = Category I ☒No = Not a forested wetland for this section Cat. I SC 5.0. Wetlands in Coastal Lagoons Does the wetland meet all of the following criteria of a wetland in a coastal lagoon? ☐ The wetland lies in a depression adjacent to marine waters that is wholly or partially separated from marine waters by sandbanks, gravel banks, shingle, or, less frequently, rocks ☐ The lagoon in which the wetland is located contains ponded water that is saline or brackish (> 0.5 ppt) during most of the year in at least a portion of the lagoon (needs to be measured near the bottom) ☐Yes – Go to SC 5.1 ☒No = Not a wetland in a coastal lagoon SC 5.1. Does the wetland meet all of the following three conditions? ☐ The wetland is relatively undisturbed (has no diking, ditching, filling, cultivation, grazing), and has less than 20% cover of aggressive, opportunistic plant species (see list of species on p. 100). ☐ At least ¾ of the landward edge of the wetland has a 100 ft buffer of shrub, forest, or un-grazed or un- mowed grassland. ☐ The wetland is larger than 1/10 ac (4350 ft2) ☐Yes = Category I ☐No = Category II Cat. I Cat. II SC 6.0. Interdunal Wetlands Is the wetland west of the 1889 line (also called the Western Boundary of Upland Ownership or WBUO)? If you answer yes you will still need to rate the wetland based on its habitat functions. In practical terms that means the following geographic areas: ☐ Long Beach Peninsula: Lands west of SR 103 ☐ Grayland-Westport: Lands west of SR 105 ☐ Ocean Shores-Copalis: Lands west of SR 115 and SR 109 ☐Yes – Go to SC 6.1 ☒No = not an interdunal wetland for rating SC 6.1. Is the wetland 1 ac or larger and scores an 8 or 9 for the habitat functions on the form (rates H,H,H or H,H,M for the three aspects of function)? ☐Yes = Category I ☐No – Go to SC 6.2 SC 6.2. Is the wetland 1 ac or larger, or is it in a mosaic of wetlands that is 1 ac or larger? ☐Yes = Category II ☐No – Go to SC 6.3 SC 6.3. Is the unit between 0.1 and 1 ac, or is it in a mosaic of wetlands that is between 0.1 and 1 ac? ☐Yes = Category III ☐No = Category IV Cat I Cat. II Cat. III Cat. IV Category of wetland based on Special Characteristics If you answered No for all types, enter “Not Applicable” on Summary Form N/A Wetland Rating System for Western WA: 2014 Update Rating Form – Effective January 1, 2015 12 Wetland name or number: A This page left blank intentionally Features depicted are not to scale. Sketches are based on available data and best professional judgment. Wetland B not applicable to this project. Wetland Figures - 1 WETLAND A (DEPRESSIONAL) Figure 1. Cowardin plant classes – D1.3, H1.1, H1.4 I Features depicted are not to scale. Sketches are based on available data and best professional judgment. Wetland B not applicable to this project. Wetland Figures - 2 Figure 2. Hydroperiods, outlet(s), and 150-ft area – D1.1, D1.4, H1.2, D2.2, D5.2 I Outlet Outlet Features depicted are not to scale. Sketches are based on available data and best professional judgment. Wetland B not applicable to this project. Wetland Figures - 3 Figure 3. Map of the contributing basin for Wetland A – D4.3, D5.3 I Features depicted are not to scale. Sketches are based on available data and best professional judgment. Wetland B not applicable to this project. Wetland Figures - 4 Figure 6. Undisturbed habitat and moderate-low intensity land uses within 1 km from wetland edge including polygon for accessible habitat – H2.1, H2.2, H2.3 I Features depicted are not to scale. Sketches are based on available data and best professional judgment. Wetland B not applicable to this project. Wetland Figures - 5 Figure 7. Screen-capture of 303(d) listed waters in basin – D3.1, D3.2 Wetland Units, drain south Features depicted are not to scale. Sketches are based on available data and best professional judgment. Wetland B not applicable to this project. Wetland Figures - 6 Figure 8. Screen-capture of TMDL map – D3.3 Wetland Units Appendix H Email Communications From:Kevin Evans To:"Molstad, Neil (ECY)" Cc:Heye, Amanda (ECY); Burcar, Joe (ECY); Cheyenne Covington, PE, ENV SP, LEED AP Subject:RE: SE 172nd St & 125th Ave SE Ecology SEA Review Date:Monday, February 10, 2020 11:58:44 AM Attachments:image001.png Thank you for your review of this project, Neil. I am happy to see that you do not believe our project will require wetland mitigation or an SEA permit. Kevin Evans, P.E. Civil Engineer III - Stormwater Engineer / Project Manager Public Works Department – Surface Water Utility 1055 South Grady Way, 5th Floor Phone: (425) 430-7264 E-mail: krevans@rentonwa.gov From: Molstad, Neil (ECY) <NEMO461@ECY.WA.GOV> Sent: Monday, February 10, 2020 10:36 AM To: Kevin Evans <KREvans@Rentonwa.gov> Cc: Heye, Amanda (ECY) <ahey461@ECY.WA.GOV>; Burcar, Joe (ECY) <jobu461@ECY.WA.GOV> Subject: RE: SE 172nd St & 125th Ave SE Ecology SEA Review Good morning, I’ve had the chance to review the submittal materials and have discussed the proposed project with Amanda Heye. It does not appear likely that the project will have a significant or direct impact to the receiving water wetland. It is also not anticipated that any permits from Ecology’s SEA program or wetland mitigation will be required for this project. Please feel free to call or email me with any questions. Regards, Neil Molstad Neil Molstad Washington State Department of Ecology 425.649.7007 | nemo461@ECY.WA.GOV From: Kevin Evans <KREvans@Rentonwa.gov> Sent: Monday, February 3, 2020 10:47 AM To: Molstad, Neil (ECY) <NEMO461@ECY.WA.GOV> Cc: Heye, Amanda (ECY) <ahey461@ECY.WA.GOV>; Burcar, Joe (ECY) <jobu461@ECY.WA.GOV> Subject: RE: SE 172nd St & 125th Ave SE Ecology SEA Review THIS EMAIL ORIGINATED FROM OUTSIDE THE WASHINGTON STATE EMAIL SYSTEM - Take caution not to open attachments or links unless you know the sender AND were expecting the attachment or the link Neil, Is there any additional clarification that I, or my engineering design consultant, can provide to you to facilitate this review process? Thank you, Kevin Evans, P.E. Civil Engineer III - Stormwater Engineer / Project Manager Public Works Department – Surface Water Utility 1055 South Grady Way, 5th Floor Phone: (425) 430-7264 E-mail: krevans@rentonwa.gov From: Molstad, Neil (ECY) <NEMO461@ECY.WA.GOV> Sent: Tuesday, January 21, 2020 2:54 PM To: Burcar, Joe (ECY) <jobu461@ECY.WA.GOV> Cc: Kevin Evans <KREvans@Rentonwa.gov>; Heye, Amanda (ECY) <ahey461@ECY.WA.GOV> Subject: RE: SE 172nd St & 125th Ave SE Ecology SEA Review Joe, I should have the time to look through these materials. I’ll follow up with Kevin and/or Amanda with any specific questions. Neil Neil Molstad Washington State Department of Ecology 425.649.7007 | nemo461@ECY.WA.GOV From: Burcar, Joe (ECY) <jobu461@ECY.WA.GOV> Sent: Tuesday, January 21, 2020 2:39 PM To: Molstad, Neil (ECY) <NEMO461@ECY.WA.GOV> Cc: krevans@rentonwa.gov; Heye, Amanda (ECY) <ahey461@ECY.WA.GOV> Subject: FW: SE 172nd St & 125th Ave SE Ecology SEA Review Hi Neil, I just got off the phone with Kevin at the City of Renton and hopefully answered a few of his procedural questions. I would characterize the “ask” here as technical assistance to either Water Quality Program (grant admin role) or the City of Renton (grantee) regarding potential hydrologic impacts to a wetland connected to this Stormwater Infrastructure Project. From Kevin, I learned that there is an existing discharge into the wetland that is not proposed to change through the project, but questions were raised by WQP (Amanda Heye) regarding potential wetland impacts from the proposed drainage improvements. Amanda suggested that the City reach out to us for feedback on anticipated regulatory requirements or wetland mitigation that might be required of the project. Kevin stated that they did not intend to change the flow to the wetland, but do propose to install a number of water quality (green type) drainage improvements, which could change some of the system dynamics. It sounds like construction of the project is still 2-years out and I clarified to Kevin that SEPA would be handled by the local jurisdiction (i.e. City of Renton Planning Dept.), for which Kevin is trying to gain insight on the significance of the wetland question before committing to the full 90% design and submittal for regulatory review. Do you have time to take a look at the proposal and provide some general feedback to Kevin or Amanda? I told Kevin that I would need to check with you or Doug on your availability and that one of you would have to inform our response time. Also, you should consider Kevin a resource in helping explain the project or point you to specific materials that may inform the wetland impact question. Thanks -Joe Joe Burcar | SEA Section Manager | Department of Ecology Northwest Regional Office | o: 425-649-7096 | c: 425-681-1051 | e: joe.burcar@ecy.wa.gov This communication is a public record and may be subject to disclosure as per the Washington State Public Records Act (RCW 42.56) From: Kevin Evans <KREvans@Rentonwa.gov> Sent: Friday, January 10, 2020 1:50 PM To: Burcar, Joe (ECY) <jobu461@ECY.WA.GOV> Subject: SE 172nd St & 125th Ave SE Ecology SEA Review THIS EMAIL ORIGINATED FROM OUTSIDE THE WASHINGTON STATE EMAIL SYSTEM - Take caution not to open attachments or links unless you know the sender AND were expecting the attachment or the link Joe, I am the City of Renton project manager for the SE 172nd St & 125th Ave SE Green Stormwater Infrastructure Project, which is funded by an Ecology water quality grant (WQSWPC-2016-Renton- 00058). I have attached the project’s 60% design documents that I previously submitted to Ecology. In her comments to our 60% design report, Ecology’s Amanda Heye requested us to have the SEA program staff review the project submittals and provide comment. She said that this would help determine if additional permitting and/or wetland mitigation would be required due to the impacts of the project on the downstream wetland. I have a few questions about the SEA review process that I hope you can answer for me. Firstly, how does one begin the review process and how long does it typically take? Is this SEA review separate from the SEPA? We had initially planned to complete the SEPA once we had completed the full 90% design, since we are still about 2 years out from construction. However, do we need to work on SEPA and SEA review concurrently? Thank you, Kevin Evans, P.E. Civil Engineer III - Stormwater Engineer / Project Manager Public Works Department – Surface Water Utility 1055 South Grady Way, 5th Floor Phone: (425) 430-7264 E-mail: krevans@rentonwa.gov