No preview available
HomeMy WebLinkAboutEX_04_27-RS_ BW_Design_Report_220107_v1 City of Renton Burnett Ave S & Williams Ave S Water Quality Retrofit Project Design Report January 2022 BHC Consultants, LLC 1601 Fifth Avenue, Suite 500 Seattle, WA 98101 (206) 505-3400 www.bhcconsultants.com This report has been prepared for the use of the client for the specific purposes identified in the report. The conclusions, observations, and recommendations contained herein attributed to BHC Consultants constitute the opinions of BHC Consultants. To the extent that statements, information, and opinions provided by the client or others have been used in the preparation of this report, BHC Consultants has relied upon the same to be accurate, and for which no assurances are intended and no representations or warranties are made. BHC Consultants makes no certification and gives no assurances except as explicitly set forth in this report Copyright 2020, BHC Consultants, LLC All rights reserved. City of Renton Burnett Ave S & Williams Ave S Water Quality Retrofit Project Design Report i TABLE OF CONTENTS 1. Introduction .......................................................................................................................................... 1  2. Basin Description ................................................................................................................................. 1  2.1 Historic Conditions .................................................................................................................... 1  2.2 Existing Conditions .................................................................................................................... 2  2.3 Proposed Conditions ................................................................................................................. 2  3. Site Description .................................................................................................................................... 3  3.1 Project Limits ............................................................................................................................. 3  3.2 Threshold Discharge Areas ....................................................................................................... 3  3.3 Current and Proposed Uses ...................................................................................................... 4  3.4 Existing Stormwater Facilities ................................................................................................... 4  3.5 Total Area ................................................................................................................................. 5  3.6 Vegetation ................................................................................................................................. 5  3.7 Wetlands ................................................................................................................................... 5  3.8 Topography ............................................................................................................................... 5  3.9 Geology and Soils ..................................................................................................................... 6  3.10 Groundwater ............................................................................................................................. 6  3.11 Access ...................................................................................................................................... 7  4. Core and Special Requirement Analysis .............................................................................................. 7  5. Alternatives Modeled and Considered ............................................................................................... 10  5.1 DUIP Baseline Model Results ................................................................................................. 10  5.2 Current Project Model Results ................................................................................................ 12  6. Design Analysis ................................................................................................................................. 13  6.1 Conveyance ............................................................................................................................ 13  6.2 Water Quality .......................................................................................................................... 14  7. Quantify the Water Quality Benefit ..................................................................................................... 15  8. Engineers Opinion of Probable Cost .................................................................................................. 16  9. Proposed Schedule ............................................................................................................................ 16  10. Construction Stormwater Pollution Prevention Plan ........................................................................... 16  11. Special Reports and Studies .............................................................................................................. 20  12. Other Permits ..................................................................................................................................... 20  13. Operation and Maintenance Manual .................................................................................................. 20  14. References ........................................................................................................................................ 20  City of Renton Burnett Ave S & Williams Ave S Water Quality Retrofit Project Design Report ii TABLES Table 1 DUIP Study Area Basin Summary ................................................................................................... 4  Table 2 Threshold Discharge Areas ............................................................................................................. 8  Table 3 Cedar River– Outfall Boundary Conditions .................................................................................... 10  Table 4 DUIP Baseline Model Inputs .......................................................................................................... 11  Table 5 Current Project Model Inputs ......................................................................................................... 12  Table 6 Sub-basin Breakdown of Pervious and Impervious Areas ............................................................. 13  Table 7 Conveyance Modeling Summary ................................................................................................... 14  Table 8 Water Quality Treatment Design Flow Rates and BMPs ............................................................... 15  Table 9 Water Quality Benefit Calculation .................................................................................................. 16  FIGURES Figure 1 – Vicinity Map Figure 2 – Williams Drainage Basin Figure 3 – Water Quality Sub-Basin Areas Figure 4 – Reconnaissance and Delineation Sketch Figure 5 – SWDM Minimum Requirements Flow Chart Figure 6 – Existing System Deficiencies Figure 7 – Alternative 1 Proposed Improvements Figure 8 – Alternative 2 Proposed Improvements Figure 9 – Alternative 3 Proposed Improvements Figure 10 – Williams Ave S XP-SWMM Proposed Model Output for 100-year Figure 11 – Burnett Ave S XP-SWMM Proposed Model Output for 100-year SELECT DRAWINGS G-1 Cover Sheet, Vicinity Map, and Index of Drawings G-2 General and Surface Water Drainage Notes G-3 Legend and Abbreviations EC-1 Temporary Erosion and Sedimentation Control (ESC) Notes C-1 Key Plan and Survey Control C-2 Burnett Ave S – Plan and Profile STA 1+00 to 5+75 C-3 Burnett Ave S – Plan and Profile STA 5+75 to 11+00 C-4 Williams Ave S – Plan and Profile STA 20+00 to 24+50 C-5 Williams Ave S – Plan and Profile STA 24+50 to 29+50 C-6 Williams Ave S – Plan and Profile STA 29+50 to 31+00 C-7 S Tobin Street – Plan and Profile STA 40+00 to 43+50 C-8 Water Quality Treatment BMP Details – S Tobin Street C-9 Water Quality Treatment BMP Details – Williams Ave S City of Renton Burnett Ave S & Williams Ave S Water Quality Retrofit Project Design Report iii APPENDICES Appendix A Cultural Resources Report Appendix B Wetland Reconnaissance and Stream Delineation Report Appendix C Geotechnical Report Appendix D Water Quality Calculations Appendix E 30 Percent Design Cost Estimate Appendix F Operations and Maintenance Information City of Renton Burnett Ave S & Williams Ave S Water Quality Retrofit Project Design Report iv ABBREVIATIONS AND ACRONYMS LIST ac Acres ac-ft Acre-Feet bgs Below Ground Surface BMP Best Management Practice CD Center-Downtown CESCL Certified Erosion and Sediment Control Lead cfs Cubic Feet per Second City City of Renton DHA Duane Hartman & Associates DO Dissolved Oxygen DUIP Downtown Utility Improvements Project Ecology Department of Ecology ESC Erosion and Sediment Controls ft Feet g Grams GULD General Use Level Designation hr Hour lf Linear Feet ModWet Modular Wetland Water Quality Treatment Device NAD 83 North American Datum of 1983/91 NAVD 88 North American Vertical Datum of 1988 OHWM Ordinary High-Water Mark Project Burnett Ave S and Williams Ave S Water Quality Retrofit Project Report Stormwater Design Report ROW Right-of-Way SEPA State Environmental Policy Act SMMWW Stormwater Management Manual for Western Washington SWDM Renton Surface Water Design Manual SWPPP Stormwater Pollution Prevention Plan SWPPS Stormwater Pollution Prevention and Spill Control TDA Threshold Discharge Area TSS Total Suspended Solids WA Washington State WQ Water Quality City of Renton Burnett Ave S & Williams Ave S Water Quality Retrofit Project Design Report 1 1. Introduction This Design Report was prepared for the City of Renton (City) Burnett Ave S & Williams Ave S Water Quality Retrofit Project (project). This report was developed in accordance with the 2017 City of Renton Surface Water Design Manual (Renton, 2017), which incorporates the 2016 King County Surface Water Design Manual (King County, 2016) with Amendments. The King County manual has been approved by the Washington State (WA) Department of Ecology (Ecology) as an equivalent manual to Ecology’s 2012 Stormwater Management Manual for Western Washington (SMMWW) as amended in 2014 (Ecology, 2014). This report was also developed in accordance with the document entitled, Design Deliverables for Stormwater Projects with Ecology Funding, updated September 2019 (Ecology, 2019). The project is located in downtown Renton, south of the Cedar River and west of Interstate 405 (I-405) as presented on Figure 1 (located at the end of the report). The project area includes Burnett Ave S and Williams Ave S between 2nd Street S and the Cedar River; and also S Tobin Street between Burnett Ave S and Williams Ave S. The purpose of this project is to improve water quality in the Cedar River watershed by designing Runoff Treatment best management practices (BMPs) for future construction on Burnett Ave S and Williams Ave S. Once constructed, the BMPs designed by this project will provide water quality treatment for total suspended solids (TSS), dissolved copper, dissolved zinc, and total phosphorous. The water quality portion of the work is being funded through a Water Quality Combined Financial Assistance Agreement between Ecology and the City (Agreement No. WQC-2020-Renton-00214). The project also includes replacing existing undersized stormwater conveyance pipes with new, larger pipes to minimize flooding, and will include removal and in-kind restoration of asphalt surfacing, concrete sidewalks, grass, and other surface features as necessary to install the stormwater improvements. 2. Basin Description This section describes the historic, existing, and proposed conditions of the basin in which the project is located. 2.1 Historic Conditions The project area is located in downtown Renton, within the floodplain of the Black River, near the historic junction of the Cedar River and the Black River. The ground surface of the project area and surrounding vicinity is generally flat and at an elevation of less than 40 feet (ft). A Cultural Resources Report was prepared for this project by Cascadia Archaeology (Cascadia, 2020), included as Appendix A and briefly summarized here. Prior to the construction of the Lake Washington Ship Canal in 1917, Lake Washington drained from its south end into the Black River, which flowed into the Duwamish River and then into Elliott Bay. The Cedar River flowed into the Black River just under one-quarter mile west of the project area. When the Ship Canal lowered the level of Lake Washington, the Black River ceased to flow, and the Cedar River was diverted and channelized to flow into Lake Washington (Cascadia, 2020). The modern Cedar River channel forms the northern boundary of the project. City of Renton Burnett Ave S & Williams Ave S Water Quality Retrofit Project Design Report 2 Historically, the project area and surrounding floodplains had a high concentration of large villages and large encampments, regional trails, and Native American Indian landmarks and place names. Permanent Euro-American settlement of the project area began in 1865, including a dairy farm. The Northern Pacific Railway ran along the western edge of the project area and was constructed by 1907. Urban and residential development of the project area began around 1912. By 1936, all of the modern Renton downtown streets existed in the project area except S Tobin Street and S Tillicum Street. Early development of the project area was mostly residential. By 1968, about one-quarter to one-fifth of homes were replaced by large buildings, suggesting more commercial and industrial uses. Since that time, some redevelopment has occurred, and two large multi-residence buildings have been recently constructed (Cascadia, 2020). 2.2 Existing Conditions The project area is comprised of mixed urbanized land use consisting of commercial businesses, multi-family apartments, and high-density single-family housing and has an estimated 90 percent effective impervious area. Zoning within the project area is based on the Land Use Zoning map dated July 1, 2015 and includes center-downtown (CD) and right-of-way (ROW) zoning. Nearly three-quarters of the project area is zoned as CD, and the remaining nearly one-quarter is zoned as ROW. The existing roadways within the project area have concrete sidewalks, planters, and streets with curbs and gutters. The existing storm drainage system consists of catch basins, manholes, and mostly 8-inch diameter concrete conveyance pipes installed in the 1950s. A single 12-inch diameter concrete outfall conveys drainage freely from the project area to the Cedar River. There are no water quality or flow control facilities within the project area. At the location of discharge, the Cedar River is listed in the Department of Ecology (Ecology)s 303(d) impaired water bodies as a Category 5 for pH, temperature, and dissolved oxygen (DO) and a Category 2 for mercury. The project area lies within the City’s Aquifer Protection Area Zone 1 for one-year capture, prohibiting infiltration as a water quality treatment option. During large storms, there are known areas of flooding within the project area. A predecessor to this project was the Renton Downtown Utility Improvements Project (DUIP) in 2018. During the DUIP, the entire downtown Renton stormwater trunk line collection system was evaluated using XP-SWMM modeling software, deficiencies were identified, alternative preliminary designs were modeled, and the City of Renton Downtown Utility Improvements Conceptual Stormwater Design Report (BHC, 2018) was prepared. The DUIP model results identified undersized conveyance pipes and areas of flooding within the project area, called the Williams Basin in the DUIP. Additional information on the existing stormwater features is presented in Section 3.4. Select modeling information from the DUIP are presented in Section 5.1. 2.3 Proposed Conditions The project proposes to update the stormwater collection and conveyance system and install water quality treatment facilities within the project area. Additional information on the proposed stormwater features is provided in Section 3.5. Detailed design calculations are presented in Section 6.0. Proposed improvements relate only to the underground stormwater conveyance and water quality facilities. No changes are City of Renton Burnett Ave S & Williams Ave S Water Quality Retrofit Project Design Report 3 proposed to the basin characteristics. Surfaces disturbed during construction will be replaced to match existing conditions. The project proposes installing two MWS-Linear Modular Wetland (ModWet) water quality treatment facilities – one in S Tobin Street, one in Williams Ave S – to improve the quality of stormwater runoff from the basin. The preferred project alternative includes upsizing stormwater trunk lines within Burnett Ave S and Williams Ave S and adding a stormwater trunk line through S Tobin Street, to reduce stormwater overflows and flooding. The existing outfall to the Cedar River will remain intact. 3. Site Description 3.1 Project Limits Project improvements are proposed along Burnett Ave S, Williams Ave S, and S Tobin Street between the Cedar River to the north and S Second Street to the south as shown on Figure 2. Burnett Ave S, Williams Ave S, and S Tobin Street are all paved, two-lane streets with concrete sidewalks, curb, and gutter on both sides of the pavement. Improvements will be constructed within City-owned right-of-way. Replacement of the existing outfall to the Cedar River was considered during Alternatives Analysis (discussed further in Section 5.0) but it was determined that the outfall was in good condition and could remain, while still providing adequate conveyance capacity to contain the 100-year return storm. Therefore, all project work will occur above the Ordinary High-Water Mark (OHWM) of the Cedar River. Some of the properties within the project area include IML Security Supply (Parcel No. 723150-2085), Merrill Gardens at Renton Center (Parcel No. 723150-2030), Salvation Army Church (Parcel No. 000720- 0140), Parkside/95 Burnett Apartments (Parcel No. 000720-0073), Chateau De Ville Apartments (Parcel No. 152910-0000), U.S. Bank (Parcel No. 723150-1979), and several single-family homes. 3.2 Threshold Discharge Areas As part of the Renton DUIP project (BHC, 2018), all stormwater drainage basins within downtown Renton were modeled using XP-SWMM to identify deficiencies and areas of flooding that did not meet the City’s Surface Water Design Standards. Within downtown Renton, there are five drainage basins that outfall to the Cedar River. The current project area consists of the Williams Basin, which is 15.61 acres in size and combines into a single outfall to the Cedar River, as shown on Figure 2. The Williams Basin encompasses Burnett Avenue S, Williams Avenue S, S Tillicum Street, and S Tobin Street, and is synonymous with the Natural Discharge Area and the Threshold Discharge Area. Stormwater within the Williams Basin outfalls to the Cedar River approximately 50-ft downstream of the Williams Avenue S bridge where it crosses the Cedar River. As part of the DUIP, the Williams Basin was divided into sub-basins, Williams-1, Williams-2, and Williams-3, for hydrologic and hydraulic modeling purposes (BHC, 2018). Table 1 provides a summary of the Cedar River basins. City of Renton Burnett Ave S & Williams Ave S Water Quality Retrofit Project Design Report 4 Table 1 DUIP Study Area Basin Summary Receiving Water Basin Outfall Location Sub-basin Area (Ac) Cedar River 68.72 acres Logan 35.68 acres Logan Ave S and Cedar River Logan-1 5.55 Logan-2 15.88 Logan-3 14.25 Williams Williams Ave S and Cedar River Williams-1 2.02 15.61 acres Williams -2 8.56 Williams-3 5.03 Wells Wells Ave S and Cedar River Wells 5.66 5.66 acres Main Main Ave S and Cedar River Main 3.69 3.69 acres Old City Hall Bronson Way S/Mill Ave S and Cedar River Old City Hall-1 3.41 8.08 acres Old City Hall-2 4.67 3.3 Current and Proposed Uses Currently, the project drainage system within the ROW consists of constructed facilities, including curb and gutter, catch basins, manholes, and pipes that collect and convey stormwater runoff to a single outfall to the Cedar River. The project proposes to replace existing facilities without changing the current use of the project area. Larger stormwater trunks will be installed, aging stormwater catch basins and structures will be replaced, and new water quality treatment facilities will be added to provide improved stormwater management in accordance with current stormwater regulations. Land disturbed during construction will be returned to its existing surface condition. Approximately 18,000 square feet (sf) of ground disturbance is anticipated. 3.4 Existing Stormwater Facilities Existing stormwater collection and conveyance system in the project area consists of a series of catch basins, 8-inch diameter concrete pipes routing north along Burnett Ave S, east along S Tillicum Street, and north along Williams Ave S before connecting to a 12-inch concrete outfall to the Cedar River. There are currently no water quality treatment facilities within the project area. In 2017, the Parkside at 95 Burnett apartment building experienced damage due to flooding after a large storm. The DUIP project hydrologic and hydraulic analysis of the existing system also indicated insufficient City of Renton Burnett Ave S & Williams Ave S Water Quality Retrofit Project Design Report 5 capacity in the project area for the 10-year event, and flooding during the 25-year event. The existing stormwater system was determined to be inadequate based on the City’s current Surface Water Design Standards. Video survey investigations of the outfall conducted by APS Survey and Mapping, LLC in 2014 indicated that the outfall is in good condition. Video survey investigation of certain pipe sections along Burnett Avenue S were also performed and the results indicated that several pipe sections had cracks, separated joints, and roots growth in some joints. Certain pipe sections along Williams Avenue S were also inspected and the results indicated that there were pipe sags and blockage, and joint offsets in some pipe sections. Pipe collapse was observed at 72 Burnett Avenue. Duane Hartman & Associates (DHA) Surveyors completed a topographic survey for this project which is used as a base map for the design drawings (refer to Select Drawings included in this report). The survey base map shows the existing stormwater facilities in the project area. 3.5 Total Area The total project area is 15.61 acres. The breakdown of the of the sub-basins within the project area is presented in Table 21 and shown on Figure 3. 3.6 Vegetation The project area is located in the City of Renton’s downtown core which is fully developed with a mix of commercial businesses, multi-family residents, single-family housing, asphalt roadways, and concrete sidewalks. There are limited areas of lawn, ornamental trees, and vegetated planting strips adjacent to sidewalks. The City’s Parks Department owns a walking path adjacent to the Cedar River that contains additional grass and mature trees. The bank of the Cedar River is comprised of restoration plantings and non-native vegetation. 3.7 Wetlands The Watershed Company performed a wetland reconnaissance and OHWM delineation study of the Cedar River in the vicinity of the proposed project improvements, identifying any critical areas located either within the project area or within 200 ft of the project area. Two wetlands in or adjacent to the project area were identified during this investigation (see Figure 4) and classified as Category III wetlands with low habitat function. These wetlands and their associated buffers are not anticipated to impact the proposed project since the project construction will occur only within existing paved ROWs, which do not currently provide functional buffers. The findings and conclusions of this investigation are detailed in the Wetland Reconnaissance and Stream Delineation Report included as Appendix D. 3.8 Topography A topographic survey was prepared for the project site by DHA in 2020. The vertical datum for the project site is based on the North American Vertical Datum of 1988 (NAVD 88). The horizontal datum is based on the Washington State Plane Coordinate System, North Zone, North American Datum of 1983/91 (NAD 83). Site topography is shown on the Select Drawings provided with this report. City of Renton Burnett Ave S & Williams Ave S Water Quality Retrofit Project Design Report 6 The topography is relatively flat ranging from elevation 40 to 35, with the exception of the banks of the Cedar River, which slope down to an elevation of approximately 25 near the outfall to the Cedar River. 3.9 Geology and Soils The project site is located in the central portion of the Puget Lowlands, where a variety of soils are present. Fine-grained and coarse-grained alluvium and flood plain deposits, volcanic mudflows, and landslide materials are all present in the general project vicinity. Kleinfelder performed a geotechnical investigation (Kleinfelder, 2021) in the project area starting with a preliminary field investigation in September 2020. This included selecting and drilling three different borings in the project area. The drilling program was completed in February 2021. Boring KB-1, located in Williams Avenue S near the Cedar River outfall, was advanced to 30 ft below ground surface (bgs). Borings KB-2 and KB-3, located in S Tobin Street and Williams Avenue S, respectively, were both advanced to 20 ft bgs. A prior Kleinfelder boring for the DUIP project (KB-04) located in the southeast corner of the project area in the alley south of Williams Avenue S was also used in the geotechnical engineering analysis. Kleinfelder’s review of existing geotechnical data and data collected from the borings indicated that the soils in the project area are variable, and that historical events, such as the 1912 Cedar River diversion project, had a significant impact on the subsurface conditions observed during the geotechnical investigation. In 1911, a major flood along the lower Cedar River prompted the City to divert the river directly into Lake Washington, which created the channel location observed in the project area today. The former channel of the Cedar River underlies the northeast portion of the project area, where all three borings are located. Boring KB-1, located near the outfall, encountered buried timber or logs at approximately 25 to 30 ft bgs. The soils encountered in the borings are characterized as follows: loose to medium stiff silty fill, and loose to dense granular fill, was observed just below the pavement sections and generally ranged from about 7½ to 15 ft thick. Borings KB-1, KB-2, and KB-3, encountered a mix of silts and sands with varying amounts gravel, likely placed to fill the Cedar River channel during the diversion project. Boring KB-4 encountered gravel with varying amounts of silt and sand, likely placed more recently as backfill for the below grade portion of nearby apartment complexes. Medium dense to dense alluvium soils comprised of a mix of fine to coarse sands and gravels with varying silt contents were encountered below the fill layer in each of the four borings and extended to the boring termination depth. Additional information is provided in the Geotechnical Report included as Appendix C. 3.10 Groundwater During the geotechnical drilling process, groundwater levels were generally observed at approximately 15 ft bgs. As part of the DUIP project, groundwater monitoring well (MW-5) was installed in the southwestern corner of the project area on Burnett Avenue S. Sampling was conducted at this location once a month from April 2019 to January 2020, with groundwater levels ranging from 14.3 ft bgs in January 2020 to 17.8 ft bgs in August 2019. The groundwater conditions are anticipated to vary depending on the season, rate and duration of recent precipitation, local subsurface conditions, and the level of the Cedar River, amongst City of Renton Burnett Ave S & Williams Ave S Water Quality Retrofit Project Design Report 7 other factors. A review of available data for the downtown Renton area indicates that groundwater levels range from as shallow as 4 ft bgs to up to 20 ft bgs. More information regarding groundwater monitoring and observed conditions is provided in the Geotechnical Report included as Appendix C. 3.11 Access Construction will occur within existing asphalt paved ROWs. Maintenance access to the two proposed water quality treatment facilities will be from Williams Avenue S and S Tobin Street. 4. Core and Special Requirement Analysis The project has received Ecology funding and so must use the Ecology Stormwater Management Manual for Western Washington, or equivalent manual, to determine applicable stormwater requirements and size stormwater facilities. The King County Surface Water Design Manual has been acknowledged as an equivalent manual by Ecology, and the City of Renton Surface Water Design Manual is based upon the King County Manual with several additions. The following guidance documents are applicable to the project:  2017 City of Renton Surface Water Design Manual (SWDM)  Ecology Design Deliverables for Stormwater Projects with Ecology funding, Revised September 2019. Construction of the proposed water quality BMPs and associated conveyance piping will disturb approximately 18,000 sf of existing asphalt roadways, concrete curbs and gutters, and potentially some sidewalks and curb ramps. Approximately 3,000 linear feet (lf) of stormwater trunk lines will be replaced, with a minimum trench width of 4 ft; lateral and catch basin replacements will require an additional 6,000 sf of replaced surface, for a total of approximately 18,000 sf of disturbed area. The project will restore disturbed areas with in-kind material once work has been completed. No permanent changes to existing pervious or impervious surfaces are anticipated. The definition of Replaced Impervious Surface in Chapter 1 of the Renton SWDM states that: replaced impervious surface means any existing impervious surface on the project site that is proposed to be removed and re-established as impervious surface, excluding impervious surface removed for the sole purpose of installing utilities or performing maintenance on underground infrastructure. The project serves to install new stormwater utilities and improve upon the existing stormwater utilities, so is therefore a retrofit project negating the replaced impervious surface area. This allows the project to undergo a Category 1 and 2 Targeted Drainage Review. However, in cooperation with Ecology and the funding agreement, the City desires the project to exceed the minimum requirements and will evaluate Core Requirement #8 for water quality and #9 for On-Site BMPs for compliance with the Ecology 2019 SWWMM within reasonable means. The Flow Chart for Determining Requirements for Redevelopment is included as Figure 5. The impervious and pervious areas for the project are provided in the Table 2 below. City of Renton Burnett Ave S & Williams Ave S Water Quality Retrofit Project Design Report 8 Table 2 Threshold Discharge Areas Location Area of Proposed Work Limits (sf) Existing Pervious Area (sf) Existing Impervious Area (sf) Replaced Pervious Area (sf) New Impervious Area (sf) Replaced Impervious Area 1 (sf) Project Work Area 18,000 1,000 17,000 1,000 0 17,000 Notes: 1) Replaced impervious surfaces are part of an underground utility project Core Requirement #1: Discharge at the Natural Location. The project is exempt from Core Requirement #1 as the proposed improvements will not alter the existing drainage patterns in the project area, nor change the existing outfall discharge pipe or location to the Cedar River. Core Requirement #2: Offsite Analysis. A Level 1 downstream analysis was completed to meet Core Requirement #2. The project discharges directly to the Cedar River via manmade piped conveyance. No downstream flooding, erosion, ponding, or other stormwater problems have been observed or will be aggravated as it may relate to this project. The project will not modify the outfall or significantly change the outfall discharge. The Cedar River has existing levee protection along both banks between the project site and Lake Washington. At the location of discharge, the Cedar River is listed in the Department of Ecology (DOE)s 303(d) impaired water bodies as a Category 5 for pH, temperature, and dissolved oxygen (DO) and a Category 2 for mercury which qualifies as a downstream water quality problem requiring special attention according to Section 1.2.2.1.2 in the Renton SWDM. The water quality problem impact mitigation defined in Section 1.2.2.3 of the Renton SWDM do not apply or are met on this project, as the project is exempt from Core Requirement #8, does not include a wetvault or wetpond, open drainage features, use of leachable heavy metals, is not a subdivision, and does not include a concrete vault stormwater control structures that would not be treated to prevent alteration of pH. However, enhanced water quality treatment is proposed to treat the project drainage area and improve downstream water quality problems, as described in Core Requirement #8, exceeding the current minimum requirements. Core Requirement #4: Conveyance System. The existing conveyance system is known to have capacity deficiencies and a significant portion will be replaced. The proposed conveyance system improvements have been designed using an appropriately defined runoff computation as specified in Section 3.2 of the Renton SWDM and Section 5.0 of this report. The model shows the improvements create sufficient capacity to convey and contain the 25-year peak flow. Additionally, the proposed conveyance system improvements convey the 100-year peak flow within the roadway and not cause a severe flood or erosion problem. New sections of conveyance pipe in S Tobin Street and Williams Ave S were designed to accommodate the water quality facilities described in Core Requirement #8. City of Renton Burnett Ave S & Williams Ave S Water Quality Retrofit Project Design Report 9 Core Requirement #5: Construction Stormwater Pollution Prevention. A Construction Stormwater Pollution Prevention Plan (SWPPP) has been prepared for this project to address necessary Erosion and Sediment Controls (ESC) and identify BMPs to be used during construction. The Construction SWPPP is included in Section 10.0 of this report. Core Requirement #6: Maintenance and Operations. The City will assume maintenance and operations responsibility of the facilities constructed for this project. Maintenance requirements are included in Section 13.0 of this report. Core Requirement #7: Financial Guarantees and Liability. The contractor shall post with the City of Renton a bond, assignment of funds, or certified check. The contractor shall also maintain liability insurance as described in Section 1.2.7 of the Renton SWDM. Core Requirement #8: Water Quality. The project is exempt from providing water quality facilities under the surface area exemption under Section 1.2.8 of the Renton SWDM. However, this project will include the installation of two new water quality facilities – MWS-Linear Modular Wetlands (ModWet) in both S Tobin Street and Williams Ave S and designed based on the Ecology’s 2019 SMMWW. The proprietary ModWet units have been approved for General Use Level Designation (GULD) through Ecology’s TAPE program. They have been sized to provide enhanced treatment of the water quality flows from the contributing areas. ModWet units can also accommodate bypassing of runoff flows greater than the water quality flows. The ModWet units are designed to significantly improve water quality from existing conditions on the project site. Detailed design and treatment information is described in Section 6.2. Core Requirement #9: On-site BMPs. After construction, the project area will be restored to its existing condition. Within the vegetated areas, BMP T5.13: Post Construction Soil Quality and Depth will be required. BMP T5.13 defines minimum soil quality and depth requirements to support plant growth and improve on-site management of stormwater flow and water quality. Urban Road Improvement Project BMPs described in Section 1.2.9 of the Renton SWDM – full dispersion, full infiltration, limited infiltration, bioretention, permeable pavement, and basic dispersion – are not feasible due to the urban nature of the site, with limited pervious areas for dispersion. In addition, the project site falls within the City’s Zone 1 Aquifer Protection Area, which prohibits infiltration BMPs. Special Requirement #1: Other Adopted Area-Specific Requirements. This project aligns with the goals of the WRIA 8 Chinook Salmon Conservation Plan, the Lower Cedar River Basin Plan, and the City’s Hazard Mitigation Plan. Special Requirement #2: Flood Hazard Area Delineation. Most of the project area falls within a floodplain with an annual chance of flood of 0.2% (1 in 500) to 1% (1 in 100). The 100-year floodplain boundary is delineated on the site improvement plans. Special Requirement #3: Flood Protection Facilities. The project will rely on existing flood protection facilities, specifically the Lower Cedar River levee maintained by the King County Flood Control District. The existing levees meet the relevant standards as defined in the Lower Cedar River Maintenance Dredging Project – 2016. City of Renton Burnett Ave S & Williams Ave S Water Quality Retrofit Project Design Report 10 Special Requirement #4: Source Control. The project site will be restored to existing conditions following construction, and no new sources of pollution will be created. Special Requirement #6: Aquifer Protection Area. The project falls within the City’s Zone 1 Aquifer Protection Area; therefore, no open facilities, open conveyance systems, or infiltration BMPs shall be used as part of this project. 5. Alternatives Modeled and Considered During the DUIP project (BHC, 2018), a baseline model of the entire existing downtown conveyance system was created in XP-SWMM. The DUIP model identified areas of flooding and capacity constraints throughout downtown Renton. Three preliminary design alternatives were modeled for the DUIP to address flooding and capacity. Two of those alternatives for the Williams Basin were carried forward to this project; the model was further refined, and a final preferred alternative was selected, which has become the basis for the current project design. Table 3 presents the fixed backwater elevations of the Cedar River at the project outfall for the 10-year, 25-year, and 100-year storms. These elevations were used in both the DUIP baseline model, and the current project model. Table 3 Cedar River – Outfall Boundary Conditions Basin Location (XPSWMM Node) HEC-RAS Cross Section and Location Fixed Backwater Elevation at Outfall (feet) 1, 2 Tide gate? (yes/no) 10-year storm 25- year storm 100- year storm Williams Williams Ave S Outfall (Node O_1) CX 6502 downstream face of Williams Ave S Bridge 27.86 30.05 30.94 no Notes: 1) Fixed backwater elevations at Cedar River outfall boundary conditions for the 10-, 25-, and 100-year storms correlate to modeled river water surface elevations for the 2-, 10-, and 25- year flows, respectively. River water surface elevations are based on the City of Renton’s 2008 Cedar River HEC-RAS Sediment Model. 2) Elevations are based on the North American Vertical Datum of 1988 (NAVD 88). 5.1 DUIP Baseline Model Results Model geometry, presented in Figure 6, was set up using geospatial referencing and is based on the City’s GIS system inventory. Several data sources were reviewed to determine existing conveyance elements and confirm flow routes. Stormwater system information was downloaded from the City’s GIS database, reviewed, and compared to available City record drawings. Several historic drainage reports, hydrologic City of Renton Burnett Ave S & Williams Ave S Water Quality Retrofit Project Design Report 11 and hydraulic models, and design reports provided by the City were reviewed. Data gaps and inconsistencies were reconciled through review of record drawings, drainage studies, site visits, and limited field survey. Where record drawings and survey data were used to fill gaps in the GIS data, a note was made in the XP-SWMM file describing the change. A summary of model inputs is shown in Table 4. Complete model inputs, details, and results can be found in the Renton Downtown Utility Improvements Project Conceptual Stormwater Design Report (BHC, 2018). Table 4 Baseline Model Inputs Williams Basin Zoning Center Downtown and Right-of-Way Effective Impervious Area 90% SBUH Precipitation Data 2-year, 10-year, 25-year, 100-year 2.0, 2.9, 3.4, 3.9 inches Runoff Curve Number 98 Time of Concentration 6 minutes Number of Hydrologic Input Nodes 4 Pipe Roughness (Reinforced Concrete) 0.013 The baseline model showed several nodes in the Williams Basin overtopping the rim at the 10-year and 25- year storms, indicating capacity and flooding issues that do not meet the City’s Surface Water Design Standards. Specifically, there is a lack of capacity along Burnett Ave S and S Tillicum Street in an undersized 8-inch trunk and isolated flooding in low areas, and a lack of capacity along Willimas Ave S in an undersized 8-inch trunk. See Figure 6 for Existing System Deficiencies; green pipes do not have adequate capacity to convey the 10-year storm; orange pipes do not have adequate capacity to convey the 25-year storm; and purple pipes do not have adequate capacity to convey the 100-year storm. Black pipes have adequate capacity for the 100-year storm. Three Alternatives were modeled to address the deficiencies of the Williams Basin:  Alternative 1 (shown on Figure 7) proposed upsizing the stormwater trunk lines in the same locations, but not replacing the outfall to the Cedar River. Alternative 1 addressed much, but not all, of the flooding from the DUIP model. A 24-inch diameter trunk line was evaluated in S Tillicum Street but was found to be difficult to install due to the narrow roadway, existing utility conflicts, and that S Tillicum Street is the only access point to the underground garage of a multi-family residential building. These impacts were considered too great, and Alternative 1 was not selected.  Alternative 2 (shown on Figure 8) also proposed upsizing the stormwater trunk lines, and not replacing the outfall to the Cedar River. Instead of working within S Tillicum Street, Alternative 2 proposed installing a new 36-inch diameter trunk line along S Tobin Street, to act as an informal City of Renton Burnett Ave S & Williams Ave S Water Quality Retrofit Project Design Report 12 detention pipe that would attenuate flows prior to the outfall. This alternative reduced the impacts of Alternative 1 and addressed much, but not all, of the flooding reported in the model.  Alternative 3 (shown on Figure 9) proposed upsizing the stormwater trunk lines and upsizing and replacing the outfall to the Cedar River. Alternative 3 also included installing a new trunk line along S Tobin Street, but trunk lines could be smaller if a new, larger diameter outfall was installed. Replacing the outfall would have significant environmental, permitting, schedule, and cost impacts. 5.2 Current Project Model Results Alternative 1 was not pursued, due to the narrow ROW, existing utility conflicts, and limited access for residents. Both Alternative 2 and Alternative 3 were further evaluated. The environmental, permitting, schedule, and cost impacts of replacing the outfall in Alternative 3 could be eliminated if the outfall were in good condition, and if the conveyance system upstream could be enlarged to convey and contain both the 25-year and 100-year peak flows. Video survey investigations of the outfall conducted by APS Survey and Mapping, LLC in 2014 indicated that the outfall is in good condition and will not need to be replaced as part of this project. Model results shown in Figures 10 and 11 demonstrate the feasibility of Alternative 3. The XP-SWMM model was refined for this project in several ways: geometry was revised based on the project-specific topographic survey; sub-basin areas were delineated more precisely based on the project- specific topographic survey and actual location of catch basins; hydrology was refined based upon real- world historic storms rather than SBUH runoff files; and additional hydrologic input nodes were used to get more granular results. Table 5 presents the current project model inputs. Table 5 Current Project Model Inputs Williams Basin Zoning Center Downtown and Right-of-Way Effective Impervious Area 90% Continuous Runoff 25-year storm 03-03-1950 from MGSFlood Continuous Runoff 25-year long storm 10-06-1981 from MGSFlood Continuous Runoff 100-year storm 11-04-1998 from MGSFlood Number of Hydrologic Input Nodes 7 Pipe Roughness (PVC) 0.012 City of Renton Burnett Ave S & Williams Ave S Water Quality Retrofit Project Design Report 13 Table 6 presents the sub-basin land use breakdown input into MGSFlood to determine the hydrology for the three modeled storms. Select hydrology results are presented in Appendix D. Table 6 Sub-basin Breakdown of Pervious and Impervious Areas Sub-basin ID Area (Ac) Percent Impervious Impervious Pervious Total Williams-1 1.82 0.20 2.02 90% Williams-2 7.70 0.86 8.56 90% Williams-3 4.53 0.50 5.03 90% Total 14.05 1.56 15.61 90% The XP-SWMM model for the Williams Basin was iteratively updated to meet the City’s SWDM requirements until a preferred alternative was achieved. The preferred alternative is similar to Alternative 2 – it includes upsizing the stormwater trunk lines, including a new 36-inch diameter trunk line along S Tobin Street, and leaving the existing outfall to the Cedar River in place. Select model results for the preferred design, as refined during this project, are included in Figures 10 and 11. Results from the model show that both the 25-year storm, the 25-year long storm, and the 100-year storm peak flows can be conveyed and contained in the proposed conveyance design. 6. Design Analysis 6.1 Conveyance Existing storm drainage collection and conveyance network within the project area were modeled using the MGSFlood continuous simulation hydrologic model (MGSFlood) and XP-SWMM. Hydrology and XP- SWMM model results for each sub-basin is summarized in Table 7. Although the Renton SWDM does not require the 100-year storm to be contained within the conveyance system, it was a priority to improve public health by reducing the possibility of flooding in the project area. City of Renton Burnett Ave S & Williams Ave S Water Quality Retrofit Project Design Report 14 Table 7 Conveyance Modeling Summary Sub-basin Areas Design Storm Peak Flow Rates 100-year Flooding in XP-SWMM Sub-basin Total Area (ac) Pervious (ac) Impervious1 (ac) Treated Area2 (ac) 25-yr (cfs) 100-yr (cfs) Flood Volume (ac-ft) Flood Duration (min) Williams-1 2.02 0.20 1.82 - 1.15 1.83 0.0 0.0 Williams-2 8.56 0.86 7.70 8.56 4.87 7.77 0.0 0.0 Williams-3 5.03 0.50 4.53 4.15 2.86 4.57 0.0 0.0 Total 15.61 1.56 14.05 12.71 Notes: 1) Percent impervious = 90% 2) Existing geometry, utility conflicts, and access limitations along S Tillicum Street did not allow for the routing of runoff from Williams 1 and a portion of Williams 2 to the water quality facilities 6.2 Water Quality To meet the requirement in the Ecology funding agreement for water quality treatment, enhanced water quality treatment facilities are included in the proposed design. To provide enhanced water quality treatment, three different water quality treatment BMPs were considered, including Contech’s BioScape, Oldcastle’s BioPod, and Bio Clean’s MWS-Linear Modular Wetlands (ModWet). All options have Ecology’s GULD approval for enhanced treatment. After evaluating the three alternatives, the ModWet facilities were selected for the 30 percent design. The ModWet requires minimal hydraulic drop across each unit due to its horizontal flow treatment system, is the only facility that incorporates a pretreatment chamber, and can accommodate internal bypass flows in excess of 2 cfs. Additionally, the ModWet units do not require plantings. Instead, a traffic rated hatch can be placed over the biofiltration chamber, thus simplifying maintenance requirements. The MGS Flood continuous simulation hydrologic model was used to determine the flow rates for which the water quality treatment facilities should be sized for in each sub-basin. The 15-minute water quality flow rates for off- and on-line facilities, as well as the 25- and 100-year flow rates for each proposed water quality treatment facility are summarized in Table 8 City of Renton Burnett Ave S & Williams Ave S Water Quality Retrofit Project Design Report 15 Table 8 Water Quality Treatment Design Flow Rates and BMPs Facility Treated Area (ac) Off-line Water Quality Flow Rate of Treated Area (cfs) On-line Water Quality Flow Rate of Treated Area (cfs) 25-Year Flow Rate (cfs) 100-Year Flow Rate (cfs) Water Quality Treatment Facility (ModWet) Allowable Treatment Flow Rate (cfs) Williams-1 - - - 1.15 1.83 - - Williams-2 8.56 0.52 0.95 4.87 7.77 8-ft x 20-ft 0.577 Williams-3 4.15 0.25 0.46 2.86 4.57 8-ft x 12-ft 0.346 For the proposed design, two ModWet facilities will treat the runoff generated within the Williams-2 and Williams-3 subbasins. The 8-ft x 12-ft ModWet facility has an allowable design treatment flow rate of 0.346 cfs, and the 8-ft x 20-ft ModWet facility has an allowable design treatment flow rate of 0.577 cfs, so they can provide adequate treatment for the contributing areas. Each facility also has a maximum internal bypass flowrate of 10 cfs, so can provide adequate bypass for each sub-basin. The Williams-2 ModWet facility will treat runoff that enters the conveyance system along Tobin Street, Burnett Ave S, and a small portion of the Williams Ave S and S Tobin Street intersection. The Williams-3 ModWet facility will treat runoff that enters the conveyance system along Williams Ave upstream of the ModWet facility. Due to space limitations and utility conflicts, the Williams-1 sub-basin along S Tillicum Street, and the northern-most portion of the Williams-3 sub-basin, will not be treated before it discharges to the Cedar River. The design layouts for these proposed facilities are shown on the drawings. 7. Quantify the Water Quality Benefit The project is exempt from flow control under the Direct Discharge exemption, as it discharges directly to the major receiving water of the Cedar River downstream of the Taylor Creek confluence. The water quality benefit is shown in Table 9. For each sub-basin, Table 9 details the total basin area and the off-line water quality design flow rate if the entire sub-basin were a new/redevelopment project. Each ModWet facility’s water quality treatment flow rate capacity is also shown. Ratios of retrofit to new/redeveloped are calculated, and the resulting equivalent new/redeveloped area is 15.30ac. City of Renton Burnett Ave S & Williams Ave S Water Quality Retrofit Project Design Report 16 Table 9 Water Quality Benefit Calculation Sub-basin Total Basin Area (ac) Off-line Water Quality Design Flow Rate (cfs) to Meet New/ Redeveloped Criteria Water Quality BMP Capable Flow Rate (cfs) for Proposed Retrofit Ratio of Retrofit to New Flow Rate Equivalent New/ Redeveloped Area (ac) Williams-1 2.02 0.12 - 0% 0.0 Williams-2 8.56 0.52 0.577 111% 9.50 Williams-3 5.03 0.30 0.346 115% 5.80 Total 15.61 0.94 0.923 98% 15.30 8. Engineers Opinion of Probable Cost The 30 Percent Design Opinion of Probable Construction Cost for the entire project is $3.244 Million. The 30 Percent Design Opinion of Probably Construction Cost for the water quality elements only is $1,118,000. The water quality cost includes the ModWet facilities (bid items B06 and B07); 18 percent of the applicable bid items relevant to installing the ModWet facilities, i.e. bid items A01-A10, and B01-B05; and the bid items related to the installation of the conveyance system downstream of SDMH #B9 and SDMH #W10 to the outfall (bid items B08-B17), since this section of the conveyance system was added or relocated to accommodate the ModWet facilities. A detailed cost estimate is attached as Appendix E. 9. Proposed Schedule The City plans to advertise for construction in the spring of 2022 and complete the construction of the stormwater improvements during the summer and early fall of 2022. The City is also planning to apply for an Ecology grant in October 2021 to fund the water quality treatment portion of the construction project. 10. Construction Stormwater Pollution Prevention Plan Per Appendix D of the SWDM, a project-specific Construction Stormwater Pollution Prevention Plan (CSWPPP) is required to minimize the potential for construction activities from polluting stormwater via sediment erosion and onsite construction-related activities and materials storage. The CSWPPP is comprised of two main components: the Erosion and Sediment Control (ESC) Plan that targets erosion and sediment control requirements; and the Stormwater Pollution Prevention and Spill (SWPPS) Measures to address the best practices for management of onsite activities and materials to mitigate pollution risk. Upon award of construction and prior to earthwork activities, the Contractor will be required to prepare an update to this CSWPPP under a separate cover. The City’s SWDM outlines ESC measures required to both minimize erosion and sediment transport from an active construction site as well as protect areas with existing and proposed stormwater facilities. These measures are considered Best Management Practices (BMPs) for erosion and sediment control related to construction activities. Appendix D of the SWDM organizes these ESC measures into 13 categories, one of City of Renton Burnett Ave S & Williams Ave S Water Quality Retrofit Project Design Report 17 which includes requirements related to SWPPS measures to prevent the discharge of pollutants to onsite or adjacent stormwater systems and waterbodies. The CSWPPP must satisfy the requirements included in each category unless site conditions render the category unnecessary and the exemption from that category is clearly justified in the narrative of the CSWPPP. The 13 categories and the selected BMPs are described below. The ESC and SWPPS requirements are described on Drawing EC-1 and will be included on the plan view drawings at 60 percent.  Category 1: Clearing Limits o Clearing limits will be marked/flagged or delineated with a high-visibility fence prior to any site clearing or grading as indicated on Drawing EC-1.  Category 2: Cover Measures o Temporary and permanent cover measures will be provided to protect all disturbed areas during construction. o All exposed and unworked soils will be stabilized by suitable application of appropriate BMPs. From October 1 through April 30, in areas where construction has been completed or will not undergo additional disturbance for a period of 30 days or greater, no soils will remain unstabilized for more than 2 days. From May 1 through September 30, in areas where construction has been completed or will not undergo additional disturbance for a period of 30 days or greater, no soils will remain unstabilized for more than 7 days. Soils will be stabilized using temporary and permanent seeding and mulching. o Sloped areas will be covered with biodegradable erosion control blanket per Figure D.2.1.2.C of the SWDM, and straw wattles will be placed perpendicular to flow at regular intervals to control erosion per Figure D.2.1.2.E of the SWDM. o Stockpiles will be covered with plastic covering when they are not in use per Figure D.2.1.2.D of the SWDM.  Category 3: Perimeter Protection o Silt fencing will be installed downslope of all disturbed areas to prevent transport of sediment generated on-site to adjacent properties and reduce velocity of runoff generated on-site per Figure D.2.1.3.A of the SWDM and Drawing EC-1.  Category 4: Traffic Area Stabilization o A stabilized construction entrance is not required because the project site is paved and is located within the City’s ROW. Impacted roads and parking areas will be immediately stabilized after initial grading. All damaged pavement will be restored to match existing conditions in accordance with the Contract Documents. If necessary, a wheel wash facility will be utilized to prevent sediment from being tracked onto pavement by construction vehicles.  Category 5: Sediment Retention o Sediment retention facilities will include silt fencing and storm drain inlet protection to remove sediment from the runoff generated from areas disturbed during construction. The design of storm drain inlet protection facilities shall comply with Section D.2.1.5.3 of the SWDM. City of Renton Burnett Ave S & Williams Ave S Water Quality Retrofit Project Design Report 18 o The Contractor will be required to monitor the implemented sediment retention BMPs on a regular basis and immediately following a storm event. If BMPs are found to require maintenance or replacement, these activities will be scheduled immediately after the issues are observed.  Category 6: Surface Water Collection o Implementation of a temporary surface water collection system by the Contractor will be required to bypass the existing surface water collection system during construction. The temporary system will consist of interceptor dikes, pipe slope drains, and outlet protection.  Category 7: Dewatering Control o While project construction will occur during the dry season, it is possible that dewatering may be required if groundwater is encountered during project construction. A review of available data for the downtown Renton area indicates that groundwater levels range from as shallow as 4 ft bgs to up to 20 ft bgs. The dewatering water will be conveyed to a sediment trap located onsite to collect and treat the water as necessary prior to discharging at an approved location. Temporary stormwater tanks will be installed to control stormwater within the construction areas.  Category 8: Dust Control o Dust control will be implemented as needed during project construction. All landscaped and vegetated areas that are disturbed during construction will be vegetated or mulch will be installed for permanent stabilization. Water will be sprayed daily to limit blowing dust from leaving the site or creating a nuisance to adjacent properties. Tracked vehicle use on paved surfaces will be limited, wheel washing construction vehicles will be employed as needed, and vacuum street sweepers will be used to sweep the paved areas when necessary. Mud and other dirt will be promptly removed so it does not dry and then turn into dust. Dust-causing work will be limited to the extent practicable on windy days.  Category 9: Flow Control o Flow control facilities are not required since no changes to the speed, volume, or quantity of stormwater discharges are anticipated. In addition, the Cedar River is a flow-control exempt receiving water.  Category 10: Control Pollutants o Stormwater pollution prevention (SWPP) measures will be implemented to minimize the discharge of pollutants generated from on-site construction activities. o All pollutants will be handled in a manner that does not cause stormwater contamination. o The Contractor will provide cover, containment, and protection from vandalism for all chemicals, liquid products, petroleum products, and other materials that have the potential to pose a threat to human health or the environment. On-site fueling tanks will include secondary containment. Secondary containment means placing tanks or containers within an impervious structure capable of containing 110% of the volume contained in the largest tank within the containment structure. Double walled tanks do not require additional secondary containment. City of Renton Burnett Ave S & Williams Ave S Water Quality Retrofit Project Design Report 19 o Spill prevention and control measures will be used while conducting maintenance, fueling, and repair of heavy equipment and vehicles. Contaminated surfaces will be cleaned immediately following any spill incident. o Fertilizers and pesticides will be applied in a manner and at application rates that will not result in loss of chemical to stormwater runoff. Manufacturers’ label requirements will be followed for application rates and procedures. o BMPs will be used to prevent contamination of stormwater runoff by pH-modifying sources. The sources for this contamination include, but are not limited to: bulk cement, cement kiln dust, fly ash, new concrete washing and curing waters, waste streams generated from concrete grinding and sawing, exposed aggregate processes, dewatering concrete vaults, concrete pumping and mixer washout waters. o The pH of stormwater will be adjusted if necessary, to control potential violations of the water quality standards. o Washout of concrete trucks will be performed offsite or in designated concrete washout areas only. Concrete trucks will not be washed out onto the ground, or into storm drains, open ditches, streets, or streams. Concrete spillage or concrete discharge to surface waters of the State is prohibited. o Written approval from Ecology is required before using chemical treatment other than CO2 or dry ice to adjust pH.  Category 11: Protect Existing and Proposed Stormwater Facilities and Onsite BMPs o Protection from sediment and compaction will be provided for all existing and proposed BMPs installed for the permanent control of stormwater. BMPs that are to remain in place following completion of construction shall be examined and restored to full operating condition. If sediment enters these BMPs during construction, the sediment shall be removed, and the facility shall be returned to conditions specified in the Contract Documents.  Category 12: Maintain Protective BMPs o BMPs will be maintained throughout construction and left in place until permanent seeding and final restoration is complete. The Contractor will be required to keep ESC materials on hand to be used, as necessary. The Contractor will also be required to appoint a Certified Erosion and Sediment Control Lead (CESCL).  Category 13: Manage the Project o All BMPs will be inspected, maintained, and repaired as needed to assure continued performance of their intended function. Site inspections and monitoring will be conducted in accordance with the Construction Stormwater General Permit or local plan approval authority. o The CSWPPP will be maintained, updated, and implemented by the Contractor and the Contractor’s CESCL. As the project progresses, the CSWPPP will be modified routinely to reflect changing site conditions. The CSWPPP will be reviewed routinely to ensure the content is current. City of Renton Burnett Ave S & Williams Ave S Water Quality Retrofit Project Design Report 20 11. Special Reports and Studies Multiple reports and studies were completed under the scope of this project to inform the design process and satisfy various state regulations. They are included in the appendix of this report as follows:  Cultural Resources Report is included as Appendix A.  Wetland Reconnaissance and Stream Delineation Report is included as Appendix B.  Geotechnical Report is included as Appendix C. 12. Other Permits The following additional documents have been prepared to satisfy the permit requirements for the project:  State Environmental Policy Act (SEPA) Permit Checklist. A project specific SEPA has been prepared under a separate cover.  City of Renton Permits – A Right-of-Way (ROW) Permit will be required due to work occurring in the right-of-way and will be administered by the City. An Environmental Review, Shoreline Exemption Permit, and Land Use Permit will also be required for this project, both of which will be administered by the City’s Planning Department. 13. Operation and Maintenance Manual Properly maintained stormwater systems are important to prolong the life and effectiveness of the facilities. Site stormwater facilities will be maintained by the City. Operation and maintenance requirements and maintenance observation instructions for the stormwater conveyance system and water quality treatment facilities within the project area are presented in Appendix F. This appendix is comprised of operation and maintenance material obtained from both the SWDM and the ModWet manufacturer. 14. References Cascadia. (2021). Cutural Resources Assessment for the Burnett Ave S and Williams Ave S Water Quality Retrofit Project. Seattle: Cascadia Archaeology. City of Renton. (2017). Surface Water Design Manual. Renton: City of Renton (City). Ecology. (2014). Stormwater Management Manual for Western Washington, Amended 2014. Olympia: Washington State Department of Ecology (Ecology). Kleinfelder. (2021). Geotechnical Engineering Report, Burnett Ave S and Williams Ave S Water Quality Retrofit Project. Redmond: Kleinfelder. Watershed. (2020). City of Renton - Burnet Ave S & Williams Ave S Water Quality Retrofit Project SWP-27- 4088, Wetland Reconnaissance and Stream Delineation Report. Kirkland: The Watershed Company (Watershed). FIGURES Figure 1 – Vicinity Map Figure 2 – Williams Drainage Basin Figure 3 – Water Quality Sub-Basin Areas Figure 4 – Reconnaissance and Delineation Sketch Figure 5 – SWDM Minimum Requirements Flow Chart Figure 6 – Existing System Deficiencies Figure 7 – Alternative 1 Proposed Improvements Figure 8 – Alternative 2 Proposed Improvements Figure 9 – Alternative 3 Proposed Improvements Figure 10 – Williams Ave S XP-SWMM Proposed Model Output for 100-year Figure 11 – Burnett Ave S XP-SWMM Proposed Model Output for 100-year THIS PAGE INTENTIONALLY BLANK. k k k k k k !( ") ") ") ") ") ") ") ") ") ") !( ") !( !( ") ") !( ") ")") ") ") !(") ") ") ") !( ") ") !( ") !(!(")") ")!( ") !( ")") ") !( ") !( ") ") !( !( !( ") !( ") ") ") !( !( ") !( !( !( ") ") ") ") !( ") !(") ") ") ") !( ") !( ") ") ") ") ") ") ") ") ") ") !( ") ") ") !( ") ") ") !( !( ") ") !( ") ") ") ") ") ") !( ") ") GF GF GF GF GF GF GF GF GF GF GF GF GF GF GF GF Burnett Ave SWilliams Ave SS 2nd StLogan Ave SBurnett Pl SWells Ave SS Tobin St S Ri ver side Dr N Ri ve rside Dr± §¨¦405 Lake Washington C e d a r R i v e r Legend Subbasin ")CB - Type 1 !(CB - Type 2 MH k Storm Outfall Storm Pipe GF Potential locations for Water Quality Treatment facility Flow Direction 0 1,250 2,500625 Feet 014028070 Feet Burnett Ave S and Williams Ave S Water Quality Retrofit Figure 6 Vicnity Map Project Area Figure 1 COPYRIGHT © 2021 BHC CONSULTANTS LLC. ALL RIGHTS RESERVED This map is a geographic representation based oninformation available. No warranty is made concerningthe accuracy, currency, or completeness of datadepicted on this map. 2 FigureWater Qu ality R etrofit ProjectCity of R enton, WashingtonNovember 2021 Williams Drainage Basin !; !; !; !; !; !; !;!; !; !; g?B g?B &S2 g?B g?B g?B g?B g?B g?B g?B g?B g?B g?B g?B g?B g?B g?B g?B "T g?B g?B "T g?B g?B &S2&S2g?Bg?B g?B g?B g?B g?B g?B g?B g?B g?B g?B g?Bg?Bg?B g?B g?B g?B g?B g?B g?B g?B g?B g?B g?B g?B g?B g?B g?B g?B &S2g?B g?B &S2 &S2g?B g?B g?B g?B g?B g?B&S2 &S2 g?B g?B g?B &S2 g?B &S2 &S2 &S2 g?B g?B g?B g?B g?B &S2 g?B g?B g?B g?B g?B &S2g?B g?Bg?B &S2 g?Bg?B g?B g?B g?B g?B g?B g?B g?B g?B g?B g?B &S2 g?B g?Bg?B &S2 g?B &S2 g?B g?B g?B g?B g?B &S2 g?B &S2 g?B g?B g?B g?B g?B g?B g?B &S2 &S2 g?B &S2 g?B g?B g?Bg?B g?B g?B &S2g?B g?B &S2 g?B g?B g?B g?B &S2 g?B g?B &S2 g?B g?B g?B &S2 g?B g?B &S2 &S2 &S2 g?B &S2 g?B &S2 g?B "T"T &S2 &S2 &S2 g?B &S2 &S2 g?B "T g?B &S2 g?B &S2 &S2 g?B &S2 &S2 "T &S2 &S2 g?B g?B &S2 g?B &S2 g?B &S2 g?B g?B &S2 &S2 g?B g?B g?Bg?B &S2 g?B &S2 g?B g?B g?B g?B g?B g?B g?B g?B g?B g?B g?B g?B &S2 g?B g?B g?B g?B g?B &S2 g?B g?B &S2 g?B g?B g?B g?B &S2 &S2 g?B g?B &S2 g?B g?B g?B &S2 g?B &S2 &S2 &S2 g?B g?Bg?B g?B g?B g?B g?B &S2 g?B g?B g?B g?B g?B g?B g?B g?B &S2 g?B g?B g?B Burnett Ave SAccess Rd S 2nd St Bronson Way SMain Ave SLoganAveSWells Aly NN 1st St Wells Ave NS Tobin St E PerimeterDr Main Aly SS Riverside Dr Wells Aly SWilliams Ave SN 2nd St Wells Ave SN Riverside DrWilliams Ave NRenton TC AcRd S Tillicum St Airport Way E Perimeter Rd Williams Aly SCedar River Trail Burnett Pl SPedestrian Walk #P:\Mapping\Maps_Generated\Renton\20-10723.00\400\1.10\maps\Fig 2 Williams Drainage Basin 8.5x11.mxd 11/29/2021 ctolentino0 200100Feet Legend City of R enton SurfaceWater System g?B Inlet &S2 Manhole "?Utility Vault "T Unknown Structure !;Discharge Point Pipe Private Surface WaterSystem g?B Inlet &S2 Manhole "?Utility Vault "T Unknown Structure Private Pipe Williams DrainageBasin Right-of-way (ROW) Cedar River Ex istingOutfallProject Ex tents/Drainage Basin Right-of-way wherewater quality andconveyanceimprovements ma ybe installe d COPYRIGHT © 2021 BHC CONSULTANTS LLC. ALL RIGHTS RESERVED This map is a geographic representation based oninformation available. No warranty is made concerningthe accuracy, currency, or completeness of datadepicted on this map. 3 FigureWater Quality Retrofit ProjectCity of Renton, WashingtonDecember 2021 Water Quality Sub-Basin Areas Williams 2 Williams 3 Williams 1 Access Rd S 2nd St Bronson Way SEPerimeterRdMain Ave SWilliams Ave SLogan Ave SBurnett Ave SN 1st St S Tobin St S Riverside Dr N 2nd St Wells Ave NWells Ave SE P erim eterDr Logan Ave NN Riverside DrWilliams Ave NAirport Way S Tillicum St Wells Aly NWilliams Aly SCedar River Trail Burnett Pl SPedestrian Walk #S:\Projects\Renton\20-10723.00 Burnett and Williams\5_Design\Water Quality\Fig 3 Water Quality Sub-Basin Areas 8.5x11.mxd 12/14/2021 spalmerton0 200100Feet Legend Sub-Basins Treated Untreated Cedar River Total Area - 2.02 ac / 87,991 sfUntreated - 2.02 ac / 87,991 sf Total Area - 8.56 ac / 372,874 sfTreated - 8.56 ac / 372,874 sf Total Area - 5.03 ac / 219,107 sfUntreated - 0.88 ac / 38,368 sfTreated - 4.15 ac / 180,774 Williams 1 Williams 2 Williams 3 Page 1 of 1 RR e c o n n a i s s a n c e a n d DD e l i n e a t i o n S k e t c h –– BB u r n e t t & W i l l i a m s S t o r m w a t e r R e t r o f i t Project area: Renton, WA; City Center Prepared for: BHC Consultants Site Visit Date: November 13, 2020 TWC Ref. No.: 200903 Wetland A Note: Field sketch only. Features depicted are approximate and not to scale. OHWM is marked with blue- and white- striped flags. Data points are marked with yellow- and black-striped flags. LEGEND Wetland Area Non-delineated Wetland Boundary Delineated OHWM Non-delineated OHWM Project Extents Data Point (DP) Potential Wetland B (private property) DP-1 DP-2 Stream A OHWM (Cedar River) Flags WMA-1L to WMA-23L Figure 4 SECTION 1.1 DRAINAGE REVIEW 12/12/2016 2017 City of Renton Surface Water Design Manual 1-14 FIGURE 1.1.2.A FLOW CHART FOR DETERMINING TYPE OF DRAINAGE REVIEW REQUIRED Figure 5 Figure 5 Figure 5  &ŝŐƵƌĞϭϬʹtŝůůŝĂŵƐǀĞ^yWͲ^tDDWƌŽƉŽƐĞĚDŽĚĞůKƵƚƉƵƚĨŽƌϭϬϬͲLJĞĂƌ Ground Surface Hydraulic Grade Line  &ŝŐƵƌĞϭϭʹƵƌŶĞƚƚǀĞ^yWͲ^tDDWƌŽƉŽƐĞĚDŽĚĞůKƵƚƉƵƚĨŽƌϭϬϬͲLJĞĂƌ Ground Surface Hydraulic Grade Line SELECT DRAWINGS THIS PAGE INTENTIONALLY BLANK. APPENDIX A Cultural Resources Report THIS PAGE INTENTIONALLY BLANK. King CULTURAL RESOURCES REPORT COVER SHEET DAHP Project Number: 2019-10-07833-ECY (Please contact the lead agency for the project number. If associated to SEPA, please contact SEPA@dahp.wa.gov to obtain the project number before creating a new project.) Author: Teresa Trost and Jana Boersema Title of Report: Cultural Resources Assessment for the Burnett Ave S and Williams Ave S Water Quality Retrofit Project, City of Renton, Washington Date of Report: March 4, 2021 County(ies): King Section: 17, 18 Township: 23 Range: 5 E Quad: Renton, WA (1994) Acres: 17 PDF of report submitted (REQUIRED) Yes Historic Property Inventory Forms to be Approved Online? Yes No Archaeological Site(s)/Isolate(s) Found or Amended? Yes No TCP(s) found? Yes No Replace a draft? Yes No Satisfy a DAHP Archaeological Excavation Permit requirement? Yes # No Were Human Remains Found? Yes DAHP Case # No DAHP Archaeological Site #: • Submission of PDFs is required. • Please be sure that any PDF submitted to DAHP has its cover sheet, figures, graphics, appendices, attachments, correspondence, etc., compiled into one single PDF file. • Please check that the PDF displays correctly when opened. Cultural Resources Assessment for the Burnett Ave S and Williams Ave S Water Quality Retrofit Project, City of Renton, Washington Prepared by: Teresa Trost, Principal Investigator and Jana Boersema, M.A. Prepared for: BHC Consultants 1601 Fifth Avenue, Suite 500 Seattle, WA 98101 Lead Regulatory Agency: Washington State Department of Ecology DAHP Project No. 2020-12-07541 CONTAINS CONFIDENTIAL INFORMATION NOT FOR GENERAL DISTRIBUTION March 4, 2021 P.O. Box 51058 Seattle, WA 98115 Cascadia Archaeology, LLC i Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey MANAGEMENT SUMMARY The City of Renton (City) plans to install water quality facilities to improve the quality of stormwater runoff in the vicinity of Burnett Avenue South and Williams Avenue South between South 2nd Street and the Cedar River (the Project). The City has received a Stormwater Financial Assistance Program grant managed by the Washington State Department of Ecology (Ecology) – Agreement No. WQC-2020-Renton-00214. The Project is thus subject to the Governor’s Executive Order (GEO) 05-05 because of the use of capital funds, and Ecology is the lead regulatory agency. BHC Consultants, LLC (BHC), on behalf of the City, retained Cascadia Archaeology, LLC to conduct a cultural resources assessment prior to ground disturbing activities associated with the Project. The cultural resource assessment consisted of archival research of the Study Area, which encompasses the Project's Area of Potential Impacts (AI) and near vicinity, and archaeological field work that was the monitoring of four geotechnical borings and archaeological excavation of nine trenches and three shovel-and-auger probes. Field work occurred February 4, 8, 9, and 10, 2021. No archaeological material or historic buildings or structures were identified within the AI. Ten of the 16 borings, trenches, and probes contained manufactured objects from the modern or historic eras. Only two artifacts could be attributed a specific date or date range, which were less than 50 years old. In general the AI is underlain by a depositional sequence that consists of gravelly coarse sand found at variable depths; overlain by deposits of bedded sand; bedded silt and very fine sand; a layer of massive silt or silty sand that sometimes contained traces of organic material, rootlets, and charcoal; and a surface layer of gravelly fill. Several of the trenches and boreholes contained traces of roots and organic matter in the low energy alluvium, typically within the upper 4.9 ft (1.5 m) of the deposit. While the organic material suggests possible stable surfaces on which vegetation grew, no other evidence of soil development or any artifacts were observed. It is recommended that the Project be allowed to proceed with only the requirement that it be carried out subject to the Inadvertent Discovery Plan that has been approved for the Project. While no heritage register-eligible cultural resources were observed within the AI, it is possible that cultural materials not discovered during this investigation could be exposed during construction. In all likelihood, further historic/modern scattered debris will be exposed. Should pre-contact archaeological materials (e.g. bones, shell, stone tools, beads, ceramics, hearths, etc.) be observed during project activities, all work in the immediate vicinity should stop and a Professional Archaeologist should be contacted to verify the find and the protocols in the Inadvertent Discovery Plan followed. Compliance with all applicable laws pertaining to archaeological resources (RCW 27.53, 27.44 and WAC 25- 48) and human remains (RCW 68.50) is required. Cascadia Archaeology, LLC ii Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey TABLE OF CONTENTS MANAGEMENT SUMMARY ........................................................................................... i TABLE OF CONTENTS .................................................................................................... ii LIST OF FIGURES ........................................................................................................... iii LIST OF TABLES ............................................................................................................. iii 1.0 INTRODUCTION ....................................................................................................... 1 1.1 Project Description................................................................................................... 1 1.1 AI Location and Description .................................................................................... 4 1.3 Regulatory Context .................................................................................................. 4 2.0 CONSULTATION ....................................................................................................... 5 3.0 PHYSIOGRAPHIC CONTEXT AND SOILS ............................................................ 5 4.0 CULTURAL CONTEXT............................................................................................. 8 5.0 ARCHAEOLOGICAL CONTEXT ............................................................................. 9 5.1 Previous Investigations ............................................................................................ 9 5.2 Inventoried and Recorded Resources..................................................................... 11 6.0 INVENTORIED HISTORIC PROPERTIES, TCPS, AND CEMETERIES............. 13 7.0 RESEARCH DESIGN ............................................................................................... 13 7.1 Research Objectives ............................................................................................... 13 7.2 Archaeological Survey Expectations ..................................................................... 13 7.3 Survey Design ........................................................................................................ 14 7.3.1 Archival research ............................................................................................ 14 7.3.2 Field research ................................................................................................. 14 8.0 ARCHAEOLOGICAL SURVEY RESULTS ........................................................... 15 8.1 Field Methods ........................................................................................................ 15 8.2 Cultural Resources ................................................................................................. 18 8.3 Sediments ............................................................................................................... 19 9.0 DISCUSSION ............................................................................................................ 22 10.0 MANAGEMENT RECOMMENDATIONS ........................................................... 22 11.0 REFERENCES CITED ............................................................................................ 24 APPENDIX A – DESCRIPTION OF PROBES ................................................................. 1 Cascadia Archaeology, LLC iii Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey LIST OF FIGURES Figure 1. The Study Area shown on 7.5’ USGS quadrangle Renton, WA (1994), T. 23 N, R. 5 E., Sections 17 and 18 ............................................................................................ 2 Figure 2. Study Area and AI shown on aerial view of Renton street map ........................ 3 Figure 3. Study Area mapped on the 1983 USGS map showing location of the Cedar River in 1907....................................................................................................................... 6 Figure 4. Excerpt from a U.S. Army Corps of Engineers (USACE) 1907 map of the Black and Cedar rivers' confluence .................................................................................... 7 Figure 5. Survey map showing borings (KB-#), trenches (T#), and probes (SP#) ........... 17 Figure 6. Objects found in T9 ........................................................................................... 18 Figure 7. T2, with sand at bottom, underlying low energy alluvium................................ 20 Figure 8. T8 at 3 m ............................................................................................................ 21 Figure 9. T9 showing coal ash fill layer .......................................................................... 21 LIST OF TABLES Table 1. Archaeological Investigations Nearest or Within the Study Area ..................... 10 Table 2. Inventoried Archaeological Resources in or within One Mile of the Study Area ........................................................................................................................................... 12 Cascadia Archaeology, LLC 1 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey 1.0 INTRODUCTION The City of Renton (City) plans to install water quality facilities to improve the quality of stormwater runoff in the vicinity of Burnett Avenue South and Williams Avenue South between South 2nd Street and the Cedar River (the Project). The City has received a Stormwater Financial Assistance Program grant managed by the Washington State Department of Ecology (Ecology) – Agreement No. WQC-2020-Renton-00214. The Project is thus subject to the Governor’s Executive Order (GEO) 05-05 because of the use of capital funds, and Ecology is the lead regulatory agency. BHC Consultants, LLC (BHC), on behalf of the City, retained Cascadia Archaeology, LLC to conduct a cultural resources assessment prior to ground disturbing activities associated with the Project. A preliminary assessment (Trost 2020) that identified Historic Properties within the Study Area and developed a probability model for where unidentified Historic Properties and prehistoric archaeological material could be present within that area was completed prior to any ground disturbing work associated with the Project. Stemming from that assessment, the City funded archaeological monitoring of geotechnical borings and archaeological survey of the Project's Area of Potential Impacts (AI). The bulk of the 2020 report is copied in this report sections on context (Sections 3.0 Physiographic Context and Soils, 4.0 Cultural Context, and 5.0 Archaeological Context). This report includes the following sections: descriptions of the Project and AI; an overview of the regulatory context; a summary of consultation; the cultural context of the AI; the research objectives; the survey expectations, methods, and results; and conclusions and management recommendations. 1.1 Project Description The City desires to improve the storm water management system in the vicinity of Burnett Avenue South and Williams Avenue South between South 2nd Street and the Cedar River (Figures 1 and 2). The Project will install new water quality treatment facilities and improve the existing stormwater conveyance infrastructure. At the time of this report, the design of improvements was preliminary, but the following had been proposed: 1. Installation of a water quality facility within Tobin Street that would likely have a basal depth of 10 ft (3 m) below existing grade. 2. Replacement of main lines in the same location as the existing line, with depths of the existing line ranging from as shallow as approximately 4 ft (1.2 m) below grade at S. 2nd St. and as deep as 12 ft (3.7 m) below existing grade at the outfall at Williams Ave into the Cedar River. Cascadia Archaeology, LLC 2 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey Figure 1. The Study Area shown on 7.5’ USGS quadrangle Renton, WA (1994), T. 23 N, R. 5 E., Sections 17 and 18. Cascadia Archaeology, LLC 3 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey Figure 2. Study Area and AI shown on aerial view of Renton street map. Cascadia Archaeology, LLC 4 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey 1.2 AI Location and Description The AI is in the City of Renton, King County in Township 23 North, Range 5 East, Sections 17 and 18, Willamette Meridian (Figures 1 and 2). Project work will occur within City property or City easements. The AI is situated in downtown Renton near a channelized stretch of the Cedar River and encompasses approximately 17 acres. It is mostly covered with asphalt, aside from curbside planting strips. Approximately 14 percent of the AI was surveyed by archaeologists prior to construction of two residential facilities: 95 Burnett Apartment Homes, which is named for its street address, and Merrill Gardens Senior Living, 104 Burnett Ave S (Hodges and Piston 2004, 2005). 1.3 Regulatory Context For the purposes of this assessment, standards and guidelines for listing a cultural resource in the National Register of Historic Places (NRHP), the Washington Heritage Register (WHR), and Register of King County Landmarks were applied. A cultural resource is an object or construction (e.g., archaeological shell midden deposit, hearth, earth oven, dike, or building) that is the result of human agency and is 50 years of age or older. Cultural resources that are listed in or determined eligible for listing in a heritage register are referred to as Historic Properties. If a cultural resource is identified during an assessment, but more information is required prior to making a determination of eligibility, that potentially eligible resource is treated as if it is a Historic Property. The evaluation process for the NRHP and WHR are the same, with an emphasis placed on the significance within the context of Washington State's history for the WHR. A cultural resource may be eligible for listing in more than one register. To be determined eligible for listing in the NRHP or WHR, a cultural resource must 1) typically be at least 50 years of age; 2) meet at least one of four criteria of significance (see following paragraph); and 3) possess historic integrity. King County has a lower age requirement of 40 years and considers the importance of a cultural resource to a community as well as at the regional scale. The four criteria of significance, defined by the U.S. Secretary of the Interior in 36 CFR 60.4, are that a cultural resource is significant if it: (A) is associated with events that have made a significant contribution to the broad patterns of our history; or (B) is associated with the lives of persons significant in our past; or (C) embodies the distinctive characteristics of a type, period, or method of construction, or that represent the work of a master, or possesses high artistic values, or represents a significant and distinguishable entity whose components may lack individual distinction; or (D) has yielded or may be likely to yield, information important in prehistory or history. The association of a cultural resource to one of these criteria must be considered at the appropriate geographic scale (local, state, and/or federal) and in the context of its time period of significance. For buildings, structures, and above-ground objects (the built Cascadia Archaeology, LLC 5 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey environment), this information is presented as written documentation commonly referred to as a historic context. In the case of criterion D, the significance is generally assessed by the potential to address specific research questions. Archaeological cultural resources are usually significant under criterion D. A cultural resource possesses historic integrity if it is recognizable as the building, structure, object, site, or district as it appeared during the period of significance. Historic integrity is characterized by seven aspects (or qualities): location, design, setting, workmanship, materials, feeling, and association. A cultural resource does not need to retain all aspects of integrity to be listed in a heritage register. The last portion of criterion C often applies to districts where the buildings, structures, and objects that comprise the district are not found to be eligible for listing individually but, taken as a whole, possess historic integrity. 2.0 CONSULTATION Ecology carried out government-to-government consultation prior to any fieldwork carried out by Cascadia Archaeology. Cascadia Archaeology informed Interested Tribes as to when field surveys occurred. No tribal visits occurred during fieldwork. 3.0 PHYSIOGRAPHIC CONTEXT AND SOILS The following is copied from Trost (2020), with minor errata fixed. Geographically, the Study Area lies on the floodplain of the Black River, near the historic junction of the Cedar River with the Black River. The ground surface of the project area and surrounding vicinity is generally flat and at an elevation of less than 30 ft (9 m). Prominent hills at the valley margins, east and west of the Study Area, rise approximately 984 ft (300 m) and 3,280 ft (1000 m), respectively. The geography of the region has been significantly altered by humans during the past century. Prior to the construction of the Lake Washington Ship Canal in 1917, Lake Washington drained from its south end into the Black River, which flowed into the Duwamish River and then into Elliot Bay. The Cedar River flowed into the Black River just under one-quarter mile west of the Study Area. When the Ship Canal lowered the level of Lake Washington, the Black River ceased to flow, and the Cedar River was diverted and channelized to flow into Lake Washington (Dalan et al. 1981) (Figure 3). The modern Cedar River channel forms the northern boundary of the Study Area. Prior to these engineering changes to the Black River and Cedar River floodplains, natural events led to regular changes to the landscape. Since the end of the last ice age, the Green, White, Black, Cedar, and Duwamish rivers have frequently changed course as they flowed into Puget Sound. The level floodplain on which the Study Area now lies was built up by thick deposition at the mouth of the Cedar River Valley in an alluvial fan. In the north part of Renton these alluvial fan deposits are at least 130 ft (40 m) thick. The Cascadia Archaeology, LLC 6 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey fan deposition likely occurred right at the end of the Vashon glaciation. As the alluvial fan built up, it dammed the south end of the valley in which Lake Washington formed (Mullineaux 1970). Subsequently the Black and Cedar rivers carved channels and deposited sediment during regular flood events over the millennia: Early Renton residents described a "branch of the Cedar River" that in the winter months flowed west to the Black River...between present South 2nd Street and South 3rd Street (Hayes ca 1950 2[sic]) The seasonal stream hosted migrating salmon...[Kramer et al. 2001:15] (Figure 3). Figure 3. Study Area mapped on the 1983 USGS map showing location of the Cedar River in 1907. Base map Chrzastowski (1983). Cascadia Archaeology, LLC 7 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey The probable source map (Figure 4) for the channels of the Cedar and Black rivers shown in Figure 3 provides a few more details about the Study Area. The direction of floodwaters indicates low-lying areas which were likely former river channels (Lewarch 2006). Figure 4. Excerpt from a U.S. Army Corps of Engineers (USACE) 1907 map of the Black and Cedar rivers' confluence. Arrows indicate direction floodwaters flow. ). Two archaeological surveys (Hodges and Piston 2004, 2005) encompassing about 14 percent of the Study Area indicate that large channels of the Cedar River deposited a gravel surface representing the channel bed and in-channel gravel bars that were deposited on the post-glacial Cedar River alluvial fan. Subsequently, as the river channel Cascadia Archaeology, LLC 8 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey moved, the gravels were capped with braided stream and floodplain deposits comprised of sand and later lower-energy deposition of silt-sand couplets, which are representative of overbank deposits. Few, widely distributed core samples within the Study Area have been collected by Kleinfelder (2019) and Associated Earth Sciences, Inc. [AESI] (2001). One core was on the southern boundary of the Study Area and contained fill from 0-7 ft (0-1.8 m) below surface (Kleinfelder 2019). Five cores were completed north of Tobin St. and exposed alluvium. The core logs do not indicate the presence of a buried surface (AESI 2001), which is the stratigraphic context in which archaeological material would most likely be found. Shong and Rinck (2011) carried out a survey about 1,066 ft (325 m) to the west and generally encountered the same depositional environment as that reported by Hodges and Piston (2004, 2005) in the Study Area. Differences with the sediments observed within the Study Area were: • The depth of surface fill was very uneven; • A historic buried surface (soil A horizon) 5 cm to 40 cm thick was identified in 10 probes, underneath fill, at depths between 30 to 70 cm below surface. This stratum contained archaeological site 45-KI-1009; • Most of the high energy alluvium appears to be associated with a historic period flood channel of the Black River; • A buried alluvial terrace comprised of sandy high energy alluvium was identified. • A buried surface containing lithics, fire-modified rock, calcined animal bone, and organic-rich sediment was present in 18 probes between 140-220 cm below surface. It was typically on or in the sandy high energy alluvium; • Lithic artifacts were present between 20 and 60 cm below surface in five probes. Shong and Rinck's (2011) surveyed area appears to have remained undeveloped; it is shown as farmland and then as high school playing fields by 1936 (historicaerials.com). In contrast, within the Study Area, archaeologically surveyed areas contained demolition fill, the northern edge has been disturbed by channeling the Cedar River, buildings have been demolished throughout about three-quarters of the Study Area, roads have been constructed, and utilities installed. 4.0 CULTURAL CONTEXT The following is copied from Trost (2020), with minor errata fixed. Kramer et al. (2001) did an intensive reporting of the pre-Euro American Contact (pre- Contact) and post-Contact use of the Study Area's general locality – the area around the historic confluence of the Black and Cedar rivers – for a project within Renton High School's property. This locality had a high concentration of large villages and large encampments; regional trails to Snoqualmie Falls, Yakima Pass, Muckleshoot Prairie, and Elliot Bay; and Native American Indian landmarks/place names (Kramer et al. 2001). Cascadia Archaeology, LLC 9 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey Even after Euro-American settlers moved in, Native American use of the locality continued at least into the mid-twentieth century. The 1865 GLO survey map shows an "Indian Village" about 2 mi southwest of the Study Area. The Moses family, who were Duwamish, lived near the west side of the Renton High School property (see Figure 1) beginning in the 1850s and owned land there until 1956 (Kramer et al. 2001). Urban development along the Cedar River channel has likely greatly reduced use of the locality. Permanent Euro-American settlement of the Study Area began in 1865 when Henry H. Tobin purchased land that included the Moses family's home. Tobin eventually sold two acres to the Moses family. The Tobins, Henry and his wife Diana, built a cabin and established a farm within their 317-acre Donation Land Claim. In 1956, Henry died, and a year later his wife married Erasmus Smithers. They lived on the western side of the homestead, by the Black River, where they ran their dairy farm (Slauson 1976 in Kramer et al. 2001). By 1895, the Renton area, including the homestead was classified as having been logged (USGS 1895). However, the Tobin claim was described as "thickly forested with cedar and fir (Bagley 1929 1 746 [sic], Slauson 1967 1[sic])" (Kramer et al. 2001). Urban and residential development of the Study Area began ca. 1912. The Northern Pacific Railway ran north-south along the western edge of the Study Area and was constructed by 1907 (Anderson Map Co. 1907). The railroad grade was removed between 1976 and 1983 based on USGS topographic maps (historicaerials.com 2020). The 1912 Kroll's King County Atlas labeled an area that encompassed the Study Area "Small Tracts" (Kroll 1912). By 1936, all modern streets in the Study Area existed except for Tobin Street and those to its north. Those, Tobin and Tillicum streets, became formal roads by 1964. Early development of the Study Area was mostly in the southern three-quarters and appears to have been residential except between Burnett Ave S. and Burnett Pl S, which contained two large buildings and a few smaller homes or outbuildings. By 1968, about a quarter to one-fifth of homes were replaced by large buildings suggesting more commercial/industrial use of the Study Area. Since that time, some commercial/industrial redevelopment has occurred, and multi-residence buildings have replaced some homes. By 2009, the area appeared almost as it does today. Within the Study Area, two large apartment buildings at 95 and 104 S. Burnett Ave. were recently constructed (historicaerials.com 2020; Hodges and Piston 2004, 2005). 5.0 ARCHAEOLOGICAL CONTEXT The following is copied from Trost (2020), with minor errata fixed. 5.1 Previous Investigations A review of records in the Washington Department of Archaeology and Historic Preservation (DAHP) online database, WISAARD, indicates 65 cultural resource investigations have occurred within 1 mi of the Study Area since 1995. Those nearest to or within the Study Area were reviewed for this assessment (Table 1). Also reviewed were nearby investigations (Kramer et al. [2001], Kramer and Larson [2001], and Shong Cascadia Archaeology, LLC 10 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey Table 1. Archaeological Investigations Nearest or Within the Study Area Reference Description Results Distance and Direction from Study Area Baldwin and Chambers (2014) Road improvement; mechanical trench excavation; ~5.4 acres No CRs. Sand fill at depths 32-115 cmbs overlying mottled gray clay/silt and dark gray clay/fine sand. 469 ft (143 m) NW Baldwin et al. (2016) Trail project; 6 shovel probes w/max. depth 35 in. (90 cm); <1 acre, ~1.4 lineal mi. No CRs. Sediments variable but, generally, sandy or silty loam overlying sand often containing rounded gravels. 243 ft (74 m) NW of NW tip. Celmer (1995) Pedestrian surface survey of banks along the lower portion of the Cedar River; 1.25 lineal mi. No CRs. Includes riverbank within the Study Area. Hodges and Piston (2004) Apartment/urban redevelopment; 15 mechanically dug trenches and 16 shovel probes (overlying fill removed with excavator) at 66 ft (20 m) intervals; 0.75 acres Fill with debris from demolition of feed store. n=2 CCS flakes found in disturbed context. Recommended monitoring during construction. See Geology and Soils section of this report. Inside, middle of west side (95 Burnett Ave S). Hodges and Piston (2005) Apartment/urban redevelopment; 15 mechanically dug trenches (30 m intervals) and 7 auger probes; ~1.6 acres Fill with debris from demolition of a hardware store, a historic burn feature. Monitoring not recommended as project disturbance did not extend beyond depth of fill/past disturbance. See Geology and Soils section of this report. Inside, middle (104 Burnett Ave S). Kramer et al (2001), Kramer and Larson (2001) Boundary identification of 45-KI-501 with 46 mechanically excavated trenches 30-274 cm deep; variable intervals between trenches. Cultural sediments: Multiple occupations and flood event strata, which are not continuous throughout the property, and historic debris in fill. Non- cultural sediments: Variable, but generally loamy fill overlying sand and silty alluvium with basal deposit of clay or gravels. 591 ft (180 m) W Rooke (2010, 2012) Transit project; pedestrian survey Recommended four areas be monitored, including the area abutting the Study Area. NE corner touches/slightly overlaps SW corner of Study Area. Shong and Rinck (2011) Renton High School Field Improvements; 118 shovel and auger probes at 49 ft (15 m) intervals, averaged depth 225 cmbs; 6.27 acres Identified 45-KI-1009 and 45-KI- 1010. See Geology and Soils section of this report. 0.2 mi. (325 m) W CR=cultural resources (historic or prehistoric); cmbs = centimeters below surface Cascadia Archaeology, LLC 11 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey [2011]), that identified archaeological sites. The most relevant investigations were carried out by Hodges and Piston (2004, 2005) because those surveys were within the Study Area. Both those surveys were for construction of residential buildings. During the 2004 survey, two cryptocrystalline silicate (CCS) flakes were found in disturbed context/fill sediments. Archaeological monitoring during construction of that proposed apartment building was recommended (Hodges and Piston 2004); however, no archaeological monitoring report was located in WISAARD. Hodges' specialization is geoarchaeology/geology. His interpretation of the sediments and stratigraphy exposed by the surveys was presented in Section 3. Physiographic Context and Soils. 5.2 Inventoried and Recorded Resources Eighteen inventoried sites are mapped within approximately one mile of the Study Area (Table 2), and two un-inventoried pre-contact lithic flakes were found within the Study Area (Hodges and Piston 2004). Eight sites contain archaeology affiliated with Native American Indian culture, both pre- and post-Euro-American contact (Contact). The nearest is 0.1 mi from the Study Area. All these sites are located in alluvium near former river channels. Site types include villages, fishing camps, hearths, lithic scatters, and a historic debris scatter. The remainder of the sites date to the Contact period, which commenced circa 1850 in King County. Site 45-KI-211, which is structural remains of the Renton Coal Mine, is listed in the Washington Heritage Register. It is approximately 0.6 mi south of the Study Area. The two nearest historic archaeological sites are the Columbia & Puget Sound Railroad grade (0.14 mi south) and a historic domestic debris scatter (0.2 mi west) which is on the same bank of the modern Cedar River channel as the Study Area. Other sites are a railroad grade, industrial sites, domestic debris scatters/concentrations, and a dam with retaining walls. The closest pre-Contact site is 45-KI-501. The archeological deposits are on buried surfaces that developed within an abandoned channel of the Cedar River and date to the past 600 years (Lewarch 2006). The initial exposure of archaeological deposits was expressed in the side wall of a construction trench as follows: The archaeological strata were black to dark brown silt and sand that included charcoal fragments and flecks, fragments of calcined bone, burned soil, ash, isolated pebbles, and areas with gravel associated with burned earth. Some silt and sand had a greasy texture when rolled in the hand. A second archaeological stratum was approximately 10 centimeters below the uppermost occupation and was separated by light brown sand deposits. The lower archaeological stratum was a black organic sand layer approximately 10 centimeter thick [Lewarch 2001]. This exposure in a trench excavation during construction and subsequent archaeological survey in which mechanically excavated trenches were dug exposed archaeological deposits at depths ranging from 64 to 151 cm below surface (Kramer and Larson 2001). Data recovery excavations were reported in Lewarch (2006). Cascadia Archaeology, LLC 12 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey Table 2. Inventoried Archaeological Resources in or within One Mile of the Study Area Smithsonian Trinomial (45- ) Description Approximate location in reference to Study Area Inventory Status1 Native American Indian Affiliation KI-51 Pre-/Proto-Contact village site. 150 yr old burial. 0.75 mi SW; near former Black River channel S/I KI-59 Pre-/Proto- Contact village site 1.0 mi SW; near former Black River channel S/I KI-439 Pre-/Proto-Contact sheet midden with features. 0.6 m SW; near former Black River channel S/I KI-501 Pre-/Proto-Contact midden with features; multiple occupations; possible fishing or village site. 0.1 mi W; floodplain of the former Cedar, Black, and Duwamish rivers S/I KI-587 Pre-Contact 0.3 mi WSW; near former channel of the Black River S/I KI-686 Pre-Contact: two hearths and ca. 1940s structural remain 0.5 mi E; flood deposits in abandoned channel of the Cedar River S/I KI-1009 Historic debris scatter associated with a Duwamish family, Moses 0.3 mi W; near the former confluence of the Black and Cedar rivers on the Black River PE KI-1010 Pre-Contact midden and lithic scatter 0.2 mi W; near former Black River channel S/I Euro American or Unknown Affiliation KI-211 Renton Coal Mine 0.6 mi S WHR KI-285 Section of railroad grade 1.0 mi SW PE KI-439 Historic debris 0.6 m SW; near former Black River channel; 10 m from Pre- /Proto-contact component S/I KI-538 Columbia & Puget Sound Railroad 0.15 mi S Various sections considered PE, NE, S/I KI-542 Historic debris scatter (structural, industrial) and structural remains 0.5 mi ESE; partially on artificial bench S/I KI-686 Pre-Contact: two hearths and ca. 1940s structural remain 0.5 mi E; flood strata in abandoned channel of the Cedar River S/I KI-767 Talbot Road dam and retaining walls; fence and historic debris 0.7 mi S PE KI-848 Renton Glass Company ruins 0.5 mi S DNE KI-1218 Historic (domestic) debris scatter (ca. 1930s-40s) 0.3 mi NW DNE KI-1344 Historic (domestic) debris scatter 0.2 mi NW; near left bank of modern Cedar River channel S/I 1Inventory Status is a field in WISAARD that indicates the statu s of an archaeological resource as pertains to its listing or potential listing in a heritage register: PE=Potentially eligible for listing in a heritage register; DNE=determined not eligible for listing; S/I=Surveyed/Inventoried, not evaluated for eligibi lity; WHR=listed in the Washington Heritage Register. Note: Native American Indian affiliated sites are for this project presumed to be potentially eligible for listing in a heritage register. Cascadia Archaeology, LLC 13 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey Two lithic flakes were found in shovel probes approximately 6.6 ft (2 m) apart by Hodges and Piston (2004) during the archaeological survey for redevelopment at 95 Burnett Avenue, which lies within the Study Area. A black CCS flake was found at the contact between fill and native sediments, and a red CCS flake was found in the overlying fill sediments. Both were considered to be out of context (not in intact sediments). The surveyed area was covered by "demolition fill" averaging 60 cm thick, but was up to 120 cm thick, and contained milled wood, brick, concrete, feedbags, and other material. Structural remains were also present (Hodges and Piston 2004). More of Hodges and Piston's findings as they relate to this project are discussed in Section 3. Physiographic Context and Soils. 6.0 INVENTORIED HISTORIC PROPERTIES, TCPS, AND CEMETERIES In the context of this section, Historic Property simply refers to a cultural resource of the built environment for which a Washington State Historic Property Inventory Form is in WISAARD. They are mostly buildings but can also include parks, dikes, dams, or other elements of the “built environment”, and are usually over 50 years old. The historic homes in the Study Area were all or mostly constructed prior to 1936 (historicaerials.com 2020). Only one of those buildings (124 Williams Ave. S) has an associated Historic Property Inventory Form. Its eligibility for listing in a heritage register has not been determined. No buildings will be impacted by this Project. No Traditional Cultural Properties (TCPs) are recorded in or adjacent to the Study Area in WISAARD or cultural resource reports reviewed for this assessment. No cemeteries or burials are recorded in or adjacent to the Study Area in WISAARD or in cultural resource reports reviewed for this assessment. 7.0 RESEARCH DESIGN 7.1 Research Objectives The objective of this cultural resources investigation was to inventory Historic Properties present within the APE and assess the likelihood for buried archaeological resources to be present that may not have been identified by the archaeological survey. 7.2 Archaeological Survey Expectations Background research suggested there was a low probability of finding a historic archaeological resource that would be eligible for listing in a heritage register. Historic archaeological material found by previous archaeological survey within the Study Area was deposited by modern-day demolition of historic buildings and, as such, was managed as culturally non-significant. Most of the Study Area has the potential for containing similar demolition fill, except in the northeast quarter which has not had as much, or any, redevelopment. If archaeological material dating pre-1912 were to be found, it would most likely be associated with occupation by the Tobin family. Post 1912, the Study Cascadia Archaeology, LLC 14 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey Area was platted into small tracts and became a mixed-use area, and no significant persons or events were identified as being associated with this time period. The background research indicated a moderate potential for pre-Contact archaeological material to be present within the portions of the Study Area not previously surveyed by an archaeologist. The Statewide Archaeological Predictive Model maps the Study Area as High Risk/Very High Risk of an archaeological resource to be present. However, only two flakes in a fill deposit have been found by survey of approximately 14 percent of the Study Area, and the Study Area has been logged and cleared, developed, much of it redeveloped, and the Cedar River along its northern boundary channelized. All these events likely significantly damaged or removed archaeology dating to the pre-Contact era, if any had ever been present, and probably also would have removed post-Contact archaeological resources. Although no pre-Contact material has been found in native soils in the Study Area, the possibility remains that buried stable surfaces identified by Hodges and Piston (2004) could have been occupied. The evidence of that use could have been preserved by subsequent overbank or flood deposits. 7.3 Survey Design 7.3.1 Archival research Prior to the field survey, background research was conducted to determine the likelihood for archaeological resources to be present within the Study Area. The assessment consisted of archival research including a records search in WISAARD for previously recorded sites, historic buildings, ethnographically known sites, and traditional cultural properties. Local histories and ethnographies were consulted to understand how people formerly utilized the area. Additionally, aerial images and geologic and historic maps were used to research the natural and cultural history. 7.3.2 Field research No built structures will be affected by the Project, so the field methods were developed to sample for archaeological resources and buried surfaces that could potentially contain archaeological resources. A geotechnical survey, which was to consist of borings, was to be monitored by a geoarchaeologist. The monitor would record the sediment profile, take photographs, and potentially screen sediment samples over ¼-inch mesh screen. An archaeological survey would be carried out to provide more expansive exposures of stratigraphy and increase the volume of screened sediment. The City was to provide a mini-excavator and associated crew to dig small trenches. Because trenches provide more visibility, being larger than a shovel-and-auger probe, and because the results of Hodges and Piston's (2004, 2005) surveys were negative for archaeological resources, spacing of sub-surface probes was planned to be every 131 ft (40 m) along the route of the stormwater system infrastructure. If needed, in a few places where trenches could not be dug, a probe started with a shovel and completed with a 10-cm (5-in.) bucket hand auger would be dug. The existing infrastructure is almost entirely under asphalt, so trenches and probes were planned to be in the planting strip between the curb and the sidewalk. Pedestrian survey would be carried out when moving between probe locations. Cascadia Archaeology, LLC 15 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey The archaeological survey would be carried out by the geoarchaeologist and one other archaeologist. The geoarchaeologist would be responsible for documenting the stratigraphy and the other archaeologist would screen a sample of material from each level of excavation. Sediments would be screened over ¼-inch mesh. The volume screened per level would be measured in liters using graduated 5-gallon buckets. Contents of each level, along with a description of the stratigraphy and sediments, were recorded on a standard probe form. Photographs of the sediment profiles and overview photographs were taken. If an artifact were found, it would be placed in an archival quality bag at a depth at which it could be recovered and then spoils backfilled over it. All spoils would be backfilled into the trench they came from. 8.0 ARCHAEOLOGICAL SURVEY RESULTS 8.1 Field Methods Geoarchaeologist|Professional archaeologist Jana Boersema monitored excavation of four boreholes on February 4, 2021. Boring was directed by Will Rosso of Kleinfelder. Holocene Drilling operated the Diedrich drill rig with an 8-inch diameter auger and 2 in. diameter split spoon sampler. Geotechnical samples were taken at 2.5 ft (0.8 m) intervals in the upper 10 ft (3.0 m) and at 5 ft (1.3 m) intervals thereafter. Borehole KB-1 terminated at 30 ft (9.2 m). Boreholes KB-2, KB-3 and KB-4 terminated at 20 ft (6.1 m) (Figure 5). The archaeologist visually examined the cuttings as they came up around the auger and as they were shoveled into a barrel. The archaeologist screened samples of the cuttings from KB-2, KB-3, and KB-4, totaling approximately 30-45 L from each borehole and typically representing the upper 7.5 ft (2.3 m) of deposits. KB-1 was not sampled because the upper 7.5 ft of the hole were removed with a vactor truck to protect nearby utilities from potential damage. The hole was visually examined during and after the vactor operation, but no cuttings or spoils were available for screening. The split spoon samples for all of the boreholes were visually examined by the archaeologist. Professional archaeologist Teresa Trost met with the crew provided by the City of Renton February 8, 2021 and walked over the AI selecting locations where trenches would be placed and identifying where shovel/auger probes would need to be dug due to the presence of utilities or other physical constraints on using a mini-excavator. Trost and Boersema carried out the survey on February 9 and 10, 2021 with the assistance of the City of Renton. The City provided a CAT 305.5E2 CR trackhoe with smooth blade bucket. T1 was the only trench dug with a toothed bucket. Spoils were either placed on a flatbed truck or screened over ¼-inch mesh onto a tarp. Placement of trench spoils on the flatbed truck provided additional visibility of the sediments and any inclusions. Upon completion, all spoils and material from a trench or probe were backfilled into the hole they came from. The flatbed lifted, acting like a chute, and sediment was funneled back into the trench. As the sediment came down and out the flatbed it is was again visually inspected for artifacts and anthropogenic soils. Cascadia Archaeology, LLC 16 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey Nine trenches (T#) and three shovel probes (SP#) were dug (Figure 5). Placement of probes was strongly influenced by the presence of existing utilities. Trenches were numbered 1-10, but on the day of survey, it was decided that T4 would not be excavated after having fine-tuned the locations of T2 and T4. T1 through T7 were excavated from north to south along Williams Ave. T8 and T9 were excavated at the south end of Burnett Ave., and T10 was on the northeast corner at the intersection of Burnett Ave. and Tobin Street. The trenches were terminated between depths of 4.9 and 6.1 ft (1.5 and 1.85 m). SPs were numbered 1-3. SPs 1 and 2 were located in a cobble covered strip at the south end of Williams Ave. The excavator could not be used because of irrigation lines and sprinkler heads. SP3 was dug within the park green strip along the Cedar River because of the Cedar River Trail Extension Park's restrictions. Trenches measured approximately 1.6 ft wide and were 4.8 to 5.6 ft long (0.5 and 1.45- 1.7 m, respectively) at the top. The bottom dimensions were typically a bit smaller, except when basal gravels sloughed into the trench bottom. Shovel probes were approximately 45 cm diameter and the lower portions of SP2 and SP3 were completed with a 10-cm diameter bucket auger. The description of each geotechnical boring, trench, and shovel probe, including depth, are in Appendix A. T9 was terminated prior to achieving the desired depth because the base of the sidewalls sloughed into the trench. Each boring, trench, and probe had the stratigraphy, sediments, and contents, if any, described on standard field forms and were photo-documented. The upper stratum, which was comprised of recent fill, was not typically sampled for screening sediments until towards the base of the stratum. The average thickness of a sampled layer was 17 cm (7 in.). The average volume of sediment sampled per layer was 12.7 L. Cascadia Archaeology, LLC 17 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey Figure 5. Survey map showing borings (KB-#), trenches (T#), and shovel probes (SP#). Cascadia Archaeology, LLC 18 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey 8.2 Cultural Resources Ten of the 16 borings, trenches, and probes contained manufactured objects from the modern or historic eras, with only two attributed a specific date or date range. A Stay-tab soda can, which has been a common can style since the 1980s, was found 0-12 cm below surface in SP3. In T5, a Coca-Cola© bottle was recovered from 0-30 cm below surface and had a date mark of "72". A jumble of more than 20 bricks was exposed in the south end of T5 from 70-100 cm below surface. The bricks continued into three of the sidewalls. A "tube" of white plastic stamped with a blue line running under the words "BLUE NUN BLUE NUN" was recovered from T10 at 0-30 cm below surface. Blue Nun is a winery. T5 and T9 contained the most objects. Both trenches had a lens or layer of gray ashy sand with coal fragments. In T5, the ashy sand was a thin lens lying near the top of the jumble of bricks, which began at 70 cm below surface. In T9, the ashy sand was present from 45 to 100 cm below surface and contained two bricks; two ceramic fragments, one with a printed on floral pattern; and three varied glass fragments (Figure 6). In the overlying layer in T9, a portion of a square, white glass jar and two wire nails were recovered (Figure 6). T6 and SP2 also contained a lens of ashy sand but no associated objects. Figure 6. Objects found in T9. Cascadia Archaeology, LLC 19 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey 8.3 Sediments The four boreholes provided the deepest exposures of sediments. Generally, they contained an upper layer of gravelly fill, usually less than 2.5 ft (0.8 m) thick. In three of the boreholes (KB-1, -2, and -3) the fill was underlain by massive silty sand or sandy silt, then beds of silt and sand at greater depths. Gravelly coarse sand was found below the bedded sand and silt at 30 ft (9.2 m) in KB-1, 15 ft (4.6 m) in KB-2, and 7.5 ft (2.3 m) in KB-3. KB-4, excavated in an alley between a very large apartment building and smaller office buildings, had a layer of crushed recycled concrete fill at the surface, and then contained gravelly coarse sand to a depth of 15 ft (4.6 m) and clast-supported gravel with very little sand matrix below that depth. The coarse sand and gravel exposed in the boreholes was generally found at greater depths in the north part of the AI and shallower depths in the south. The bedded fine- grained alluvium that overlies the gravel has some potential for buried temporarily stable pre-Contact or historic surfaces, and such things as organic material and developed soil horizons could be evidence of buried surfaces. KB-1 had charcoal and black organic staining at 9.8 ft (3.0 m) and KB-2 had a few bits of woody debris and a fine root at 7.5 ft (2.3 m). Notably KB-1 also contained large chunks of wood in the coarser sand deposits at depths of 20 ft and 25 ft (6.1 m and 7.6 m). However, these roots and staining appeared to be traces of organic material and did not have associated evidence of developed soil horizons or any cultural material, so they probably do not represent significant stable surfaces. The trench excavations exposed similar stratigraphy, but most trenches were not deep enough to encounter the coarse sand and gravel that was observed in the boreholes. The trenches were terminated between depths of 4.9 6. (1.5 m) and 6.1 ft (1.85 m). Only T2 reached a deposit of gravelly sand, just exposed at the bottom of the trench at 4.6-4.9 ft (1.4-1.5 m) (Figure 7). All of the trenches had fill and disturbed local sediments in the upper 1.3-3.9 ft (0.4-1.2 m). Under the fill, fine-grained alluvium consisting of silty sand or sandy silt was present. Rootlets and occasional organic staining were observed at depths ranging from 3.3 ft (1 m) to about 4.9 ft (1.5 m). In several of the trenches bedded silt and sand were present below about 4.9 ft. The beds of silt and fine sand indicate low energy alluvial deposition such as in a floodplain environment. SP3 was excavated north of the trenches and boreholes along Williams Ave. in the AI and was near to the bank of the channelized Cedar River. It consisted of gravelly sand fill throughout its depth ( 0-3.4 ft [0-1.05 m]). SP1 and SP2 were excavated south of the trenches along Williams Ave. in locations where backhoe trenches were not feasible. SP1 encountered very gravelly fill throughout its depth and was terminated by compact gravel deposits at 3.8 ft (1.15 m). SP2 contained gravelly and sandy fill, including a lens of gray ash with coal fragments, in the upper meter. The fill was atop beds of fine to coarse sand and silty sand. Gravelly sand was found at 6.1 ft (1.85 m). Cascadia Archaeology, LLC 20 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey Figure 7. T2, with sand at bottom, underlying low energy alluvium. T8, T9, and T10 were excavated along Burnett Ave. T8 was at the north end of the AI and was the deepest trench, excavated to a depth of 9.8 ft (3 m). It had a layer of gravelly fill at the surface (0-2.0 ft [60 cm]); massive sandy silt (2.0-3.0 ft [60-90 cm]); olive brown to gray silt (3-6.2 ft [90-190 cm]) with a few roots, charcoal, and organic stains (4.6-5.2 ft [140-160 cm]); silty fine sand (6.2-7.9 ft [190-240 cm]); and then alternating beds of silt and silty fine sand (7.9-9.8 ft [240-300 cm]) (Figure 8). T9 and T10 were excavated near the south end of the project area. T9 had recent fill at the surface consisting of brown gravelly silty sand and sand (0-1.5 ft [0-45 cm]); a second fill layer was present that consisted of gravelly gray ashy sand in which coal chunks and fragments were common (1.5-3.38 ft [45-100 cm]) (Figure 9). Both layers of fill contained historic or temporally non-diagnostic objects. Underlying the fill was very gravelly sand (3.28- 4.1 ft [100-125 cm]). The trench was terminated at 4.1 ft (125 cm) because the unconsolidated deposits were collapsing into the hole. T10, excavated only 66 ft (20 m) south of T9, did not contain unconsolidated gravel. It exposed fill (0-2.0 ft [0-60 cm]); silt and silty fine sand (2.0-2.8 ft [60-85 cm]); and then alternating beds of silt and sand (2.8-6.2 ft [85-190 cm]). Cascadia Archaeology, LLC 21 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey Figure 8. T8 at 9.8 ft (3 m). Figure 9. T9 showing coal ash fill layer (light gray layer with white flecks) and gravelly sand at base. Cascadia Archaeology, LLC 22 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey 9.0 DISCUSSION The absence of archaeological material, aside from the recent/historic ashy sandy fill, was not entirely unexpected. The location has undergone residential development and urban redevelopment, which likely removed any archaeological material that may have been at or near the surface. Prior to this survey, the only archaeological material identified by previous surveys encompassing 14 percent of the Study Area was two lithic flakes found in fill. In general the AI is underlain by a depositional sequence that consists of gravelly coarse sand found at variable depths; overlain by deposits of bedded sand; bedded silt and very fine sand; a layer of massive silt or silty sand that sometimes contained traces of organic material, rootlets, and charcoal; and a surface layer of gravelly fill. In the project area the gravelly coarse sand was typically found below depths of 6.6 ft (2 m) (KB-1, KB-2, and KB-3). Work by Hodges and Piston (2004, 2005) on property adjacent to the AI resulted in similar observations, with the top of the gravelly deposits ranging from 2.5 ft (75 cm) to greater than 11.8 ft (360 cm). In the AI, the very gravelly sand was found at shallow depths without an overlying deposit of silt or silty fine sand in T9 (3.28 ft [100 cm]), KB- 4 (2.5 ft [75 cm]) and SP1 (3.0 ft [90 cm]). This gravel may represent shallowly buried river channel or bar deposits, or it may represent gravelly fluvial material used as fill; however, it did not contain any historic or recent objects that would clearly indicate its origin as fill. In T2 and SP2 gravelly sand was found below low-energy alluvial deposits, at depths of 4.6 ft (140 cm) and 6.1 ft (185 cm), respectively. This gravelly sand likely represents the top of high energy alluvial deposits, or possibly just a lens of higher- energy deposits such as was present in KB-1 at about 7.5 ft (230 cm). Several of the trenches and boreholes contained traces of roots and organic matter in the low energy alluvium, typically within the upper 1.5 m of the deposit. While the organic material suggests possible stable surfaces on which vegetation grew, no other evidence of soil development or any artifacts were observed. Large pieces of wood were found in coarse sand in KB-1 at depths of 20 ft and 25 ft (6.1 and 7.6 m). This deeply buried wood likely represents logs that were deposited as flotsam in older fluvial deposits. 10.0 MANAGEMENT RECOMMENDATIONS It is recommended that the Project be allowed to proceed with only the requirement that it be carried out subject to the Inadvertent Discovery Plan that was approved for this Project. While no heritage register-eligible cultural resources were observed within the AI, it is possible that cultural materials not discovered during this investigation could be exposed during construction. In all likelihood, further historic/modern scattered debris will be exposed. Should pre-contact archaeological materials (e.g. bones, shell, stone tools, beads, ceramics, hearths, etc.) be observed during project activities, all work in the immediate vicinity should stop and a Professional Archaeologist should be contacted to verify the find and the protocols in the Inadvertent Discovery Plan followed. Compliance Cascadia Archaeology, LLC 23 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey with all applicable laws pertaining to archaeological resources (RCW 27.53, 27.44 and WAC 25- 48) and human remains (RCW 68.50) is required. Cascadia Archaeology, LLC 24 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey 11.0 REFERENCES CITED Anderson Map Company 1907 Atlas of King County Washington. Electronic resource, http://www.historicmapworks.com/Map/US/1250017/Page+17+++Township+ 23+North++Range+5+East/King+County+1907/Washington/, accessed November 13, 2020. Associated Earth Sciences, Inc. 2001 Subsurface Exploration, Geologic Hazard, and Preliminary Geotechnical Engineering Report: Williams Avenue Apartments. Report provided by BHC Consultants, Inc., Seattle. Bagley, Clarence B 1929 History of King County, Washington (4 Vols.) . S.J. Clarke Publishing, Chicago. Baldwin, Garth and Jennifer Chambers 2014 Cultural Resources Assessment for the Logan Avenue North Roadway Improvements Project, Renton, King County, Washington. Report prepared for Widener & Associates, Everett, Washington by Drayton Archaeology. Report NADB: 1686039, Project # 082614-01-FHWA, on file at DAHP, Olympia. Baldwin, Garth, Jennifer Chambers, and Martha Chambers 2016 Cultural Resources Assessment for the Lake Washington Loop Trail Project, Renton, King County, Washington. Report prepared for Widener & Associates, Everett, Washington by Drayton Archaeology. Report NADB: 1688490, Project # 2016-04-02602, on file at DAHP, Olympia. Celmer, Gail 1995 Cedar River Reconnaissance Survey. Report NADB: 1334586 Project # NA, on file at DAHP, Olympia. Chrazastowski, Michael 1983 Historical Changes to Lake Washington and Route of the Lake Washington Ship Canal, King County, Washington [Map]. United States Geological Survey, Department of the Interior. Electronic resource, https://pubs.usgs.gov/of/1981/1182/plate-1.pdf, accessed November 13, 2020. Dalan, Rinita, Sandra Hunt, and Steve Wilke 1981 Cultural Resource Overview and Reconnaissance: Green River Flood Damage Reduction Study. Geo-Recon International Report. Report NADB: 1331055, Project # NA, on file at DAHP, Olympia. Cascadia Archaeology, LLC 25 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey Hayes, Jack ca. 1950 I Came Here In 1880. Article on file at the Renton Public Library, Renton, Washington Hodges, Charles M. and Victoria Piston 2004 Cultural Resources Assessment for the Parkside at 95 Burnett Development, Renton, King County, Washington. Report prepared for TSA Architects, Inc., Bellevue, Washington by Northwest Archaeological Associates, Inc. Report NADB: 1343769, Project # NA, on file at DAHP, Olympia. 2005 Cultural Resources Assessment for the Merrill Gardens at Renton Centre, Renton, King County, Washington. Report prepared for Friedman Development, Mercer Island, Washington by Northwest Archaeological Associates, Inc. Report NADB: 1344552, Project # NA, on file at DAHP, Olympia. historicaerials.com (NETROnline) 2020 Burnett Ave S & Tobin St, Renton, WA. Aerial imagery 1936, 1940, 1964, 1968, 1980, 1990, 2002, 2006, 2009. Electronic resource www.historicaerials.com, accessed November 11, 2020. *Only years in which change was observed are noted. Kleinfelder 2019 Geotech Logs from DUIP (PDF). Prepared by Kleinfelder, Redmond, WA. Provided by BHC Consultants, Inc., Seattle. Kramer, Stephenie, Leonard A. Forsman, Dennis E. Lewarch, and Lynn L. Larson 2001 Renton High School Archaeological Resources and Traditional Cultural Places Assessment, King County, Washington. Report prepared for Renton School District No. 403 by Larson Anthropological Archaeological Services Limited. Report NADB: 1340709, Project # NA, on file at DAHP, Olympia. Kramer, Stephenie and Lynn L. Larson 2001 Archaeological Monitoring of Backhoe Sample Points at the Renton High School Indian Site (4SKI501). Report prepared for Renton School District No. 403 by Larson Anthropological Archaeological Services Limited. Letter report NADB: 1339905, Project # NA, on file at DAHP, Olympia. Kroll Map Company 1912 Atlas of King County Washington. Electronic resource, http://www.historicmapworks.com/Map/US/503561/Township+23+N+Range +5+E/King+County+1912/Washington/, accessed November 13, 2020. Lewarch, Dennis 2001 Washington Archaeological Site Inventory Form, 45-KI-501. On file at DAHP, Olympia. Cascadia Archaeology, LLC 26 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey 2006 Renton High School Indian Site (45KI501) Archaeological Data Recovery, King County, Washington. Report prepared for Renton School District No. 403 by Larson Anthropological Archaeological Services Limited. Report NADB: 1347769, Project # NA, on file at DAHP, Olympia. Mullineaux, Donal R. 1970 Geology of the Renton, Auburn, and Black Diamond Quadrangles, King County, Washington. Geological Survey Professional Paper 672, pp.1-92. Rooke, Lara C. 2010 Cultural Resources Discipline Report for the Burien to Renton RapidRide—F Line Project, NEPA Documented Categorical Exclusion, Final Historical, Archaeological, and Cultural Resources Discipline Report. Report prepared for King County Metro Transit by AMEC. Report NADB: 1354596, Project # NA, on file at DAHP, Olympia. 2012 Cultural Resources Discipline Report for the Burien to Renton RapidRide—F Line Project, NEPA Documented Categorical Exclusion Project – Addendum, Historical, Archaeological, and Cultural Resources Report – Addendum. Report prepared for King County Metro Transit by AMEC. Report NADB: 1683232, Project # NA, on file at DAHP, Olympia. Shong, Michael and Brandy Rinck 2011 Archaeological Assessment for Phase I of the Renton High School Field Improvement Project, King County, Washington. Report prepared for Renton School District No. 403 and D.A. Hogan & Associates, Inc. by Northwest Archaeological Associates, Inc. Report NADB: 1681688, Project # 010411- 06-KI, on file at DAHP, Olympia. Slauson, Morda C. 1967 Where was Black River? Article on file at the Renton Public LIbrary, Renton, Washington. Trost, Teresa 2020 Class I Cultural Resources Assessment for the City of Renton - Burnett Ave S and Williams Ave S Water Quality Retrofit Project SWP-27-4088. Letter report prepared for BHC Consultants, LLC, Seattle by Cascadia Archaeology, Seattle. USACE 1907 Map. Repository unknown. [This map has been used as a figure in cultural resource reports, but the source was not referenced.] USGS [U.S. Geological Survey] 1891 Land Classification Sheet, Tacoma Quadrangle. Early Washington Maps: A Digital Collection – WSU Libraries. Electronic resource, Cascadia Archaeology, LLC 27 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey https://cdm16866.contentdm.oclc.org/digital/collection/maps/id/534, accessed November 13, 2020. Cascadia Archaeology, LLC A1 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey APPENDIX A DESCRIPTIONS OF PROBES Cascadia Archaeology, LLC A2 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey Description of Boreholes (KB) and Shovel/Auger Probes (SP) Probe Depth below surface (cm[ft]) Description Contents Notes KB-1 0-76 (0-2.5) Coarse sand; many rounded small to large gravel and cobbles Excavated with vac truck 76-230 (2.5-7.5.) Silty sand or sandy silt; rootlets (90-150 cm); brown and gray mottles Excavated with vac truck 230-245 (7.5-8. Mottled brown, gray and reddish brown silty sand; common gravel, subrounded to rounded, few angular Borehole sample 305 (10) Olive brown silt to silty clay Charcoal and black organic stain; rootlet Possible thin peat lens 460 (15) Upper: Olive and reddish brown fine to medium bedded sand. Lower: coarse gray sand; few gravels; charcoal fleck Charcoal fleck 610 (20) Gray silty medium sand; large chunk of wood Wood water table 760 (25) Large chunk of wood Wood 915 (30) Coarse gray sand; common rounded gravel at bottom; few pieces of wood; evergreen needle Wood; plant material KB-2 75 (2.5) Dark brown silty sand; common small rounded to subrounded gravel; asphalt chunks fill 150 (5) Fine sandy silt 230 (7.5) Brown fine sandy silt; beds of reddish-brown coarse sand; thin laminae of sandy silt Few bits of woody debris or bark and fine roots Screened 3 screens of cuttings 305 (10) Mottled brown and olive brown silty fine sand Few flecks of organic material 460 (15) Bedded gravelly coarse sand and silty medium sand; many small rounded to subrounded gravels 610 (20) Bedded dark gray coarse sand and brown silty coarse sand; rounded to subrounded gravel common KB-3 0-45 0-1.5 Dark brown gravelly silty sand Fill; Screened 3 screens of cuttings to 7.5 ft 75 (2.5) Brown and olive mottled slightly sandy silt 150 (5) Brown fine sand; bed of silty fine sand 230 (7.5) Gravelly coarse sand; many rounded and subrounded gravel and cobbles 305 (10) Gravelly fine to coarse sand; rounded to subrounded gravel and cobbles 460 (15) Grayish brown gravelly fine to very coarse sand; subrounded to rounded gravel 610 (20) Grayish brown gravelly coarse sand and grayish brown silty coarse sand with many rounded to subrounded gravel Cascadia Archaeology, LLC A3 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey Probe Depth below surface (cm[ft]) Description Contents Notes KB-4 0-75 (2.5) Gray sand and recycled crushed concrete base (0-5 ft) 1 flat, glazed, cream ceramic tile fragment Screened 3 screen loads of cuttings 0-10 ft. 150 (5) Dark yellowish-brown fine to coarse sand; many subrounded to rounded gravel 230 (7.5) Dark grayish brown fine to coarse sand; many subrounded to subangular gravel 305 (10) Yellowish brown fine to coarse sand; many subrounded to subangular gravel 460 (15) Small to large gravel; very little medium sand matrix; rounded and subrounded gravel 610 (20) Small to medium gravel; very little silty sand matrix SP1 0-30 Grayish brown coarse sand; 15% subangular to rounded gravel; Lens of light brown clayey silt Red ceramic utility pipe fragment; n=2 wire nails; n=1 nail; n=1 blue plastic; n=1 asphalt chunk Fill 30-90 Brown medium and coarse sand; <5% gravel Fill 90-115 Gray medium and coarse sand; 30% rounded and subrounded gravel Fill; terminated by gravel SP2 0-35 Dark grayish brown sandy loam; rounded and subrounded gravel to cobbles common; lens of yellowish brown sand; lens of very dark brown gravelly silty sand (0-20 cm) n=2 asphalt chunks; n=1 foil wrapper; (32-45 cm) red ceramic utility pipe fragment in wall Fill 35-60 Brown slightly silty fine sand; few granules; few coal flecks (40-60 cm) n=1 aluminum fragment; n=1 piece of coal Fill 60-100 Brown silty sand; lens of gray ash and coal fragments at about 70 cm; few rounded and angular gravel; few roots Coal ash debris Fill. Auger below 60 cm 100-120 Brown medium sand; few small rounded and subrounded gravel Alluvium 120-130 Dark grayish brown medium to coarse sand Few rootlets; piece of charcoal Alluvium 130-135 Yellowish-brown silty fine sand Alluvium 135-170 Dark grayish brown medium sand Alluvium 170-185 Olive brown very silty very fine sand 1 rootlet Alluvium 185-190 Olive brown silty medium sand; small rounded and subrounded gravel common Alluvium SP3 0-12 Very dark brown sandy loam; few subrounded gravel; many roots (0-20 cm) n=1 brown glass fragment, n=1 concrete, n=1 Stay-tab soda can Fill 12-45 Brown slightly silty sand; many subrounded and rounded gravels and cobbles; rootlets common; lens of medium sand (20-40 cm) wire (25 cmbs), n=1 large nail, n=1 asphalt Fill 54-105 Dark grayish brown gravelly sand; common rounded to subrounded small gravel to large cobbles; few small roots (60-80 cm) n=1 brick, n=2 colorless glass fragments, foil fragment, plastic fragment Fill; attempted auger at 100 cm; terminated by gravel Cascadia Archaeology, LLC A4 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey Trench (T) Descriptions Screened Sample Trench Depth Below Surface (cm) Description Basal Depth (cm) Volume (L) Contents Notes T1 0-20 Dark grayish brown coarse loamy sand; large roots (0-60 cm) - Fill 20-180 Brown to yellowish brown slightly loamy medium sand; few rounded gravels; mixed with tan sand (50- 70 cm); few roots (100-130 cm); - Historic fill and mixed alluvium. 50 11 70 12 n=1 milk glass fragment 80 20 120 20 130 13 140 14 bit of coal 160 20 180-200 Discontinuous lenses of very dark brown fine sandy loam in same matrix as above; few small to large, rounded gravel and cobbles 200 15 Alluvium T2 0-40 Dark grayish brown silty sand; rounded to angular gravel common; small to large roots present 40 11 Fill 40-90 Grayish brown slightly silty medium sand; very few gravel; lens of grayish brown sand with common rounded to subrounded gravel (70-75 cm) 50 14 mixed alluvium 70 11 90 10 90-100 Grayish brown slightly silty medium sand; small lenses of dark brown silty sand; few medium rounded gravel 100 13 Alluvium 100-140 Grayish brown silty fine sand; few rounded gravel 120 11 Charcoal fleck and some charcoal stain Alluvium 140 7 140-150 Gravelly medium and coarse sand; many rounded and subrounded gravel; few cobbles 150 15 High energy alluvium T4 0-37 Dark grayish brown coarse sandy loam; common gravel; thin organic/charcoal lens (36-37 cm) - Recent fill 37-60 Dark grayish brown coarse sandy loam; common gravel; medium to small roots common - Fill 60-105 Grayish brown to yellowish brown silty fine to medium sand; few pea gravel; medium to small roots 80 20 Fill 105 13 105-120 Yellowish brown fine sandy silt; decayed organics present; rootlets; at 120 cm lens of charcoal and 120 14 Lens of charcoal and burnt wood at Alluvium Cascadia Archaeology, LLC A5 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey burnt wood 118-120 cm 120-185 Olive gray silt; strong reddish brown mottles 150 14 Low energy alluvium 160 13 185 14 T5 0-90 Brown fine to coarse sandy loam; common gravels and cobbles, rounded and subrounded; thin lenses of ashy gray sand with coal flecks; roots common 30 - Coca cola bottle Fill 60 13 Brick 70-100 (south) Pit in south end of trench filled with bricks and cobbles in brown sandy loam matrix 95 14 20+ bricks Fill pit at south end of trench 90-150 Olive brown to gray fine sandy silt; olive gray and reddish brown mottles; lens of decayed organics and charcoal, few rootlets (140 cm) 110 13 Low energy alluvium 140 14 150 12 150-160 Mottled reddish brown and olive brown fine sand; small lens of organics and charcoal 160 14 Alluvium 160-185 Bedded gray silt and gray fine sand; orange-brown mottles 170 7 Alluvium 185 12 T6 0-40 Dark brown sandy loam; rounded gravel common; large roots; Fill; topsoil 40-120 Brown silty fine sand; few rootlets; very few gravel; Lenses of gray ashy, gravelly coarse sand (50-70 cm and 95-100 cm) 50 10 Fill 70 18 95 10 120 13 120-135 Brown silty fine sand 130 11 Alluvium 135 14 135-150 Olive brown very fine sandy silt; few rootlets 140 7 Low energy alluvium 150-160 Olive brown very fine sandy silt; few very small, rounded gravel; discontinuous lenses with few charcoal flecks and dark brown organic stains 160 11 Low energy alluvium T7 0-70 Brown silty fine sand; few rounded gravel and cobbles; roots 50 14 Blue glazed ceramic fragment Fill 70 13 Brick, cement, pipe 70-90 Brown medium sand; very few rounded gravel and cobbles; gray sandy, ashy lens Fill 90-120 Grayish brown silty fine sand; few roots 100 12 Alluvium 120 13 120-135 Olive brown silty fine sand to fine sandy silt; small roots common; lens of reddish-brown medium sand 135 13 Low energy alluvium 135-180 Beds of olive brown fine sandy silt and medium to fine sand 160 11 Alluvium 170 5 T8 0-20 Dark brown sandy loam; few - Topsoil fill Cascadia Archaeology, LLC A6 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey rounded to subrounded gravel; lenses of yellowish brown sandy loam 20-60 Very gravelly coarse sand; rounded to subrounded gravel and cobbles common; few silt lenses 30 12 wire nail, wire tree root ball basket, yellow flagging tape Fill 50 14 60 14 60-90 Olive brown fine sandy silt 70 14 Alluvium 80 12 90 10 90-140 Brown silt; few rootlets; very few small, rounded gravel 100 8 Low energy alluvium 115 12 140 24 140-160 Gray silt; few roots; organic stains; charcoal flecks 160 16 Low energy alluvium 160-190 Light olive gray silt 180 12 Low energy alluvium 190 12 190-240 Yellowish brown silty very fine sand 220 12 Alluvium 240 10 240-300 Alternating beds of gray silt and silty fine sand 260 10 Alluvium 270 16 275 6 300 12 T9 0-30 Brown silty sand; common angular crushed gravel; few roots - Recent fill 30-45 Brown fine to coarse sand; many rounded and subrounded gravels and cobbles 40 12 White glass jar; 2 wire nails Fill 45-100 Gray ashy sand; small to large angular gravel common; coal common 50 14 Brick Coal ash fill 70 10 White glass; ceramic 90 12 Brick; bottle base fragment; glass; ceramic with printed floral pattern 100-125 Dark grayish brown very gravelly fine to coarse sand; many rounded to subrounded gravel and cobbles 105 14 Channel alluvium or channel gravel used as fill 110 10 125 10 T10 0-30 Dark brown silty sand; rounded gravel common 30 10 BLUE NUN plastic wrapping Topsoil fill 30-60 Dark grayish brown gravelly coarse sand; pockets of brown sand; many gravel and cobbles 50 10 Fill 60 12 60-85 Brown silty fine sand to fine sand 75 14 Alluvium 85-130 Grayish brown beds of fine sand and medium sand 90 14 Alluvium 95 14 115 14 130 14 130-180 Grayish brown very fine sandy silt; 150 14 Alluvium Cascadia Archaeology, LLC A7 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey thin beds of reddish-brown medium sand; few rootlets 180 12 180-190 Olive gray silt; iron oxide concretions around old root casts Low energy allvuivum Cascadia Archaeology, LLC A8 Burnett Ave S and Williams Ave S Water Quality Retrofit Cultural Resources Survey APPENDIX B Wetland Reconnaissance and Stream Delineation Report THIS PAGE INTENTIONALLY BLANK. 750 Sixth Street South | Kirkland, WA 98033 P 425.822.5242 | f 425.827.8136 | watershedco.com December 1, 2020 Becca Ochiltree BHC Consultants 1601 Fifth Avenue, Suite 500 Seattle, WA 98101 Via email: becca.ochiltree@bhcconsultants.com (206) 355-8953 Re: City of Renton – Burnett Ave S & Williams Ave S Water Quality Retrofit Project SWP-27-4088, Wetland Reconnaissance and Stream Delineation Report The Watershed Company Reference Number: 200903 Summary This report has been prepared to present the findings of a wetland reconnaissance and stream delineation study located in the City Center of Renton. The study was conducted as a preliminary step to inform permitting of the Burnett Avenue S and Williams Avenue S Water Quality Retrofit Project. The project will upgrade water quality treatment facilities within the urbanized Burnett Avenue South and Williams Avenue South drainage area and upgrade the existing stormwater conveyance infrastructure. This study screened for and evaluated critical areas within the project area and within approximately 200 feet of the project area. In addition to the information and findings presented in this report, the following attachments are enclosed: • Reconniassance and Delineation Sketch • Wetland Determination Data Forms The Ordinary High Water Mark (OHWM) of the Cedar River was delineated and flagged within the project area. Additionally, two wetlands were identified within, or adjacent to, the project area. A summary of identified wetlands and streams are described in Table 1 below. Wetland Reconnaissance and Stream Delineation Report Water Quality Retrofit Project Page 2 750 Sixth Street South | Kirkland, WA 98033 P 425.822.5242 | f 425.827.8136 | watershedco.com Table 1. Summary of wetlands, streams, and required buffers. *Wetland features have not been delineated; category, habitat score, and standard buffer width are approximate. Study Area The project is located in the City of Renton, in the City Center. The northern extents of the study area are defined by the Cedar River, with the southern extents defined by South 2nd Street. The study area’s western boundary extends approximately 120 feet west of Burnett Avenue S and eastern boundary extends approximately 170 feet east of Williams Avenue S (Figure 1). It is located within Sections 17 and 18 of Township 23 North, Range 05 East of the Public Land Survey System. Figure 1. Vicinity and study area map; study area outlined in red. Feature Name Category/Type Habitat Score Standard Buffer Wetland A* Category III* 3* 60 ft. Potential Wetland B* Category III* 3* 75 ft. Cedar River Type S n/a 200’ Wetland Reconnaissance and Stream Delineation Report Water Quality Retrofit Project Page 3 750 Sixth Street South | Kirkland, WA 98033 P 425.822.5242 | f 425.827.8136 | watershedco.com Methods Field investigations for the delineation study were conducted on November 13, 2020 by The Watershed Company fisheries biologist Peter Heltzel and ecologist Roen Hohlfeld. The study area was evaluated for wetlands using methodology from the Corps of Engineers Wetland Delineation Manual (Environmental Laboratory 1987) and 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 boundaries to determine the wetland edge. Wetland A and Wetland B 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 evaluated for streams based on the presence or absence of an 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 and guidance documents including Determining the Ordinary High Water Mark for Shoreline Management Act Compliance in Washington State (Anderson 2016) and A Guide to Ordinate High Water Mark (OHWM) Delineation for Non-Perennial Streams in the Western Mountains, Valleys, and Coast Region of the United States (Mersel 2016). Public‐domain information on the subject properties was reviewed for this delineation study. Resources and review findings are presented in Table 2 of the “Environmental Setting” section of this letter. Environmental Setting The study area is located in Water Resource Inventory Area (WRIA) 8, the Cedar-Sammamish Watershed, within the Cedar River Drainage basin. The northern extents of the study area are defined by the Cedar River. The study area totals approximately 14-acres in size and encompasses the William’s sub-basin which discharges into the Cedar River. Wetland Reconnaissance and Stream Delineation Report Water Quality Retrofit Project Page 4 750 Sixth Street South | Kirkland, WA 98033 P 425.822.5242 | f 425.827.8136 | watershedco.com Land use within the study area is highly urbanized with a mix of commercial businesses, multi- family apartments, and high-density single-family housing. Approximately 90 percent of the study area consists of impervious surfaces. Vegetation is limited throughout and generally consists of small lawn areas, planters and ornamental trees. Along the Cedar River, restoration plantings as well as non-native vegetation are present. Immediately west and east of the project area Burnett Linear Park and Jones Park are dominated by maintained lawn areas with small clusters of mature trees. Topography is relatively flat throughout the study area, with the exception of steeply sloped stream banks along the Cedar River. Reviewed public-domain information for the site is summarized below (Table 2). Table 2. Summary of online mapping and inventory resources. Findings One stream (Cedar River) was delineated and flagged within the study area. Additionally, two wetlands (Wetland A and B) were identified within or adjacent to the study area; wetland features were not delineated in the study. Resource Summary USDA NRCS: Web Soil Survey Urban land USFWS: NWI Wetland Mapper One riverine system (Cedar River) located within study area; no wetlands mapped with 300 feet of study area. WDFW: PHS on the Web Sockeye, bull trout, kokanee, steelhead, coho, chinook, and cutthroat mapped in study area. WDFW: SalmonScape Documented chinook, coho, and sockeye spawning; documented steelhead rearing; documented bull trout and kokanee presence. WA-DNR: Forest Practices Activity Mapping Tool One Type S water body (Cedar River) mapped along northern extent of study area; one Type F stream mapped approximately 530 feet south of study area. King County iMap One stream (Cedar River) mapped at northern boundary of study area; no wetlands mapped within 300 feet of study area. FEMA floodway and 100-year floodplain extend approximately 75 feet into study area. City of Renton Maps One stream (Cedar River) mapped at northern boundary of study area; 100-year floodplain extend approximately 75 feet into study area; no wetlands mapped within 300 feet of study area. WETS Climatic Condition Normal Wetland Reconnaissance and Stream Delineation Report Water Quality Retrofit Project Page 5 750 Sixth Street South | Kirkland, WA 98033 P 425.822.5242 | f 425.827.8136 | watershedco.com C edar River The Cedar River, a Shoreline of the State, is located at the northern extent of the study area. The left bank OHWM was flagged between Wells Avenue S and Logan Avenue S bridges. The Cedar River flows northwest though the study area and discharges into Lake Washington approximately 1 mile north of the study area. The Cedar River is approximately 100 feet in width within the study area, with a gradient of less than 1% slope based on King County topography data. At the time of the site visit on November 13th, the USGS stream gage located at Renton, WA (USGS 12119000) measured approximately 9.8 feet, with a 1,300 cubic feet per second flow rate. Streambed substrate is composed of cobble, gravel, and fine sediments (sand and silt). Some bank armoring is present within the study area. The stream channel is fairly straight and confined in the study area reach and includes areas of glides and riffles; gravel bars are present with lower flows. Riparian vegetation is limited to a narrow corridor dominated by a mixture of native and invasive plants as well as a row of mature deciduous trees. The Cedar River is a fish-bearing stream that supports multiple fish species including salmonids such as sockeye, bull trout, kokanee, steelhead, coho, chinook, and cutthroat. Wetland Reconnaissance and Stream Delineation Report Water Quality Retrofit Project Page 6 750 Sixth Street South | Kirkland, WA 98033 P 425.822.5242 | f 425.827.8136 | watershedco.com Figure 2. Cedar River facing northwest (downstream), taken from Williams Ave S bridge. Figure 3. Left bank of Cedar River showing approximate location of existing outfall. Wetland Reconnaissance and Stream Delineation Report Water Quality Retrofit Project Page 7 750 Sixth Street South | Kirkland, WA 98033 P 425.822.5242 | f 425.827.8136 | watershedco.com Wetland A Wetland A is a depressional wetland located in Burnett Linear Park, immediately west of the study area. One data point (DP-1) was taken within Wetland A, with hydrophytic vegetation, hydric soils, and wetland hydrology present. Soils sampled within the wetland meet requirements for Redox Dark Surface (F6) and saturation was present at 4-inches below surface grade at the time of sampling. The primary source of hydrology appears to be a high groundwater table. Wetland A consists of emergent vegetation dominated by maintained lawn and creeping buttercup. Figure 4. Wetland A, facing north; puddles present due to recent precipitation. Potential Wetland B Potential Wetland B is a small depressional wetland located on private property at the western boundary of the study area near S Tobin Street. Observations were made from the city right-of- way and a soil sample could not be examined. Wetland B is located in a narrow swale and there appeared to be surface water shallowly ponded at the time of the study. Dominant vegetation in the wetland area includes Sitka willow, black cottonwood, Himalayan blackberry, reed canary grass, and giant horsetail. Wetland Reconnaissance and Stream Delineation Report Water Quality Retrofit Project Page 8 750 Sixth Street South | Kirkland, WA 98033 P 425.822.5242 | f 425.827.8136 | watershedco.com Figure 5. Potential wetland area, Wetland B, facing west; puddles present due to recent precipitation. Local Regulations The Cedar River is listed as a Shoreline of the State per Renton Municipal Code (RMC) 4-3-090B (Regulated Shorelines). Therefore, Stream A (Cedar River) is classified as a Type S water body and is regulated under RMC 4-3-090 (Shoreline Master Program Regulations). The jurisdictional area of regulated shorelines includes “lands within two hundred feet (200'), as measured on a horizontal plane, from the OHWM, or lands within two hundred feet (200') from floodways, whichever is greater;” as well as “all marshes, bogs, swamps, and river deltas associated with streams, lakes, and tidal waters that are subject to the provisions of the State Shoreline Management Act.” (RMC 4-3-090B.3.a -b) Critical areas in the City of Renton are regulated by RMC 4-3-050 (Critical Areas Regulations). Wetlands within the City of Renton are rated as one of four categories based on the Washington State Wetland Rating System for Western Washington, 2014 Update (Ecology Publication No. 14-06-029). Accordingly, Wetland A and Wetland B are both estimated to be classified as Category III wetlands with low habitat functions (3-4 points). Wetland A is an associated wetland located within shoreline jurisdiction of the Cedar River and is thus regulated under 4-3-090B (Regulated Shorelines). Accordingly, the minimum buffer Wetland Reconnaissance and Stream Delineation Report Water Quality Retrofit Project Page 9 750 Sixth Street South | Kirkland, WA 98033 P 425.822.5242 | f 425.827.8136 | watershedco.com width for Wetland A is 60 feet (RMC 4-3-090D2.d.iii.c). However, the buffer of Wetland A is disconnected to the project area due to the presence of a multistory building, approximately 50 feet wide, that spans the length of the wetland. According to RMC 4-3-090D2.d.iii.a, “buffers shall not include areas that are functionally and effectively disconnected from the wetland by a permanent road or other substantially developed surface of sufficient width and with use characteristics such that buffer functions are not provided and that cannot be feasibly removed, relocated or restored to provide buffer functions.” Therefore, an argument can likely be made that the buffer would not extend into the project area. Wetland B appears to be located entirely outside of the Shoreline Jurisdiction and, if confirmed as a jurisdictional wetland, its buffer width would be determined by RMC 4-3-050G.2. As an estimated Category III wetland with low habitat functions located outside of areas with low impact land uses, the buffer width for Wetland B would be 75 feet. While there is a similar provision to exclude buffer areas that are disconnected from the wetland in RMC 4-3-050, this likely does not apply to Wetland B since the gravel lot comprising its encumbering buffer could be feasibly removed to restore buffer functions. However, in the case of both Wetland A and Wetland B, no buffer impacts are anticipated in association with the proposed water quality retrofit project because all construction activities, with the exception of replacing the existing stormwater outfall, are to take place within the existing right-of-way, disturbing only existing paved street areas. Permitted Alterations Utility improvements in existing improved rights-of-way within wetland buffers are an allowed use pursuant to RMC 4-3-050C.3. Additionally, according to RMC 4-3-090D7.d.ii., underground utilities, including stormwater outfalls and conveyance pipes are exempt from buffers and setbacks “provided, they are constructed and maintained in a manner that minimizes adverse impacts on shoreline ecological functions; and provided further, that they comply with all the applicable regulations in RMC Title IV.” All work within shoreline jurisdiction must follow the utility guidelines found in RMC 4-3-090E.11, as well as the no net loss and mitigation sequencing standards in RMC 4-3-090D.2.a. 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 Wetland Reconnaissance and Stream Delineation Report Water Quality Retrofit Project Page 10 750 Sixth Street South | Kirkland, WA 98033 P 425.822.5242 | f 425.827.8136 | watershedco.com (except isolated wetlands), would require notification and permits from the Corps. Unavoidable impacts to jurisdictional wetlands are typically required to be compensated through implementation of an approved mitigation plan. If activities requiring a Corps permits are proposed, a Joint Aquatic Resource Permit Application (JARPA) could be submitted to obtain authorization. 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 Management Consistency determination from Ecology and a cultural resource study in accordance with Section 106 of the National Historic Preservation Act. Washington Department 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. Ecology review under the Clean Water Act would only become necessary if a Section 404 permit from the Corps was issued. However, Ecology also regulates wetlands, including isolated wetlands, under the Washington Pollution Prevention and Control Act, but only if direct wetland impacts are proposed. Therefore, if filling activities are avoided, authorization from Ecology would not be needed. If filling is proposed, a JARPA may be also 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 regulates wetland and stream 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 of 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). Wetland Reconnaissance and Stream Delineation Report Water Quality Retrofit Project Page 11 750 Sixth Street South | Kirkland, WA 98033 P 425.822.5242 | f 425.827.8136 | watershedco.com Through issuance of an HPA, WDFW can also restrict activities to a particular timeframe. Work is typically restricted to late summer and early fall. However, WDFW has in the past allowed crossings or outfalls that do not involve in‐stream work to occur at any time during the year. 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. Please call if you have any questions or if we can provide you with any additional information. Sincerely, Roen Hohlfeld Ecologist Wetland Reconnaissance and Stream Delineation Report Water Quality Retrofit Project Page 12 750 Sixth Street South | Kirkland, WA 98033 P 425.822.5242 | f 425.827.8136 | watershedco.com 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. Environmental Laboratory. 1987. “Corps of Engineers Wetlands Delineation Manual,” Technical Report Y-87-1, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS. Hruby, T. 2014. Washington State Wetland Rating System for Western Washington: 2014 Update. (Publication #14-06-029). Olympia, WA: Washington Department of Ecology. Mersel, M.K. and Lichvar, R.W. 2014. 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. 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 Reconnaissance and Delineation Sketch – Burnett & Williams Stormwater Retrofit Project area: Renton, WA; City Center Prepared for: BHC Consultants Site Visit Date: November 13, 2020 TWC Ref. No.: 200903 Wetland A Note: Field sketch only. Features depicted are approximate and not to scale. OHWM is marked with blue- and white- striped flags. Data points are marked with yellow- and black-striped flags. LEGEND Wetland Area Non-delineated Wetland Boundary Delineated OHWM Non-delineated OHWM Project Extents Data Point (DP) Potential Wetland B (private property) DP-1 DP-2 Stream A OHWM (Cedar River) Flags WMA-1L to WMA-23L US Army Corps of Engineers Western Mountains, Valleys, and Coast – Version 2.0 DP - 1 Project/Site: Burnett & Williams City/County: Renton Sampling date: 11/13/2020 Applicant/Owner: City of Renton State: WA Sampling Point: 1 Investigator(s): Hohlfeld, R. and Heltzel, P. Section, Township, Range: T23N, R05E, S17/18 Landform (hillslope, terrace, etc): Slight depression Local relief (concave, convex, none): concave Slope (%): <2 Subregion (LRR): A Lat: - Long: - Datum: - Soil Map Unit Name: Urban land 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. 0Hydrophytic Vegetation Present? 1Yes ☒ 3No ☐ 5Is the Sampled Area 6within a Wetland? 7Yes ☒ No ☐ 8Hydric Soils Present? 9Yes ☒ 11No ☐ 13Wetland Hydrology Present? 14Yes ☒ 16No ☐ 18Remarks: 19Wetland A – 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: 2 (A) 1. 2. Total Number of Dominant Species Across all Strata: 2 (B) 3. 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. 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 = - = Total Cover UPL species x 5 = Herb Stratum (Plot size: 1-m diameter) Column Totals: (A) (B) 1. Poa sp. 85 Y FAC* Prevalence Index = B/A = 2. Ranunculus repens 25 Y FAC 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. 110 = Total Cover Woody Vine Stratum (Plot size: 3-m diameter) Hydrophytic Vegetation Present? Yes ☒ No ☐ 1. 2. - = Total Cover % Bare Ground in Herb Stratum: Remarks: * Poa species (mowed lawn) assumed to be FAC. 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-1 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 0-6 10YR 2/2 100 - Silt loam 6-18 2.5Y 3/1 80 7.5Y 4/4 20 C M Silt 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): 4” BSG (includes capillary fringe) Describe Recorded Data (stream gauge, monitoring well, aerial photos, previous inspections), if available: Remarks: WETLAND DETERMINATION DATA FORM – Western Mountains, Valleys, and Coast Region US Army Corps of Engineers Western Mountains, Valleys, and Coast – Version 2.0 DP - 2 Project/Site: Burnett & Williams City/County: Renton Sampling date: 11/13/2020 Applicant/Owner: City of Renton State: WA Sampling Point: 2 Investigator(s): Hohlfeld, R. and Heltzel, P. Section, Township, Range: T23N, R05E, S17/18 Landform (hillslope, terrace, etc): Terrace Local relief (concave, convex, none): convex Slope (%): <2 Subregion (LRR): A Lat: - Long: - Datum: - Soil Map Unit Name: Urban land 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. 20Hydrophytic Vegetation Present? 21Yes ☒ 23No ☐ 25Is the Sampled Area 26within a Wetland? 27Yes ☐ No ☒ 28Hydric Soils Present? 29Yes ☐ 31No ☒ 33Wetland Hydrology Present? 34Yes ☐ 36No ☒ 38Remarks: 39Wetland A – out 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: 1 (A) 1. 2. Total Number of Dominant Species Across all Strata: 1 (B) 3. 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. 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 = - = Total Cover UPL species x 5 = Herb Stratum (Plot size: 1-m diameter) Column Totals: (A) (B) 1. Poa sp. 100 Y FAC* 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. 100 = Total Cover Woody Vine Stratum (Plot size: 3-m diameter) Hydrophytic Vegetation Present? Yes ☒ No ☐ 1. 2. - = Total Cover % Bare Ground in Herb Stratum: Remarks: * Poa species (mowed lawn) assumed to be FAC. US Army Corps of Engineers Western Mountains, Valleys, and Coast – Version 2.0 SOIL Sampling Point: DP-2 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 0-9 10YR 3/2 100 - Silt loam 9-16 2.5Y 4/3 100 - 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) ☐ 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 moist at 16” BSG. APPENDIX C Geotechnical Report THIS PAGE INTENTIONALLY BLANK. APPENDIX D Water Quality Calculations THIS PAGE INTENTIONALLY BLANK.  ²²²²²²²²²²²²²²²²²²²²²²²²²²²²²²²²² 0*6)/22' 352-(&75(3257  3URJUDP9HUVLRQ0*6)ORRG 3URJUDP/LFHQVH1XPEHU 3URMHFW6LPXODWLRQ3HUIRUPHGRQ$0 5HSRUW*HQHUDWLRQ'DWH$0  ²²²²²²²²²²²²²²²²²²²²²²²²²²²²²²²²²  ,QSXW)LOH1DPH 7UHDWPHQW$UHDVB3UHGHYHORSHG(QWLUH%DVLQIOG 3URMHFW1DPH 5HQWRQ:45HWURILW $QDO\VLV7LWOH  &RPPHQWV (QWLUH%DVLQ3UHGHYHORSHG ²²²²²²²²²²²²²²²²35(&,3,7$7,21,1387²²²²²²²²²²²²²²²²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ntire Basin - Predeveloped Water Quality Flow Rates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ntire Basin - Postdeveloped Water Quality Flow Rates        !"#$%&'('&&&% )!*#* +&(,%-,%&%''%'   .** *&(,%-,%&%''%'/                           !    "   0 00 "0" 1 "     # $%  & ' ()         #  #   "    *  +  ,      +   *      #   -.//,0/'* ( ,0 ' /1/1-,-2/1/10/-3 (   #    -./,0* ( ,0 % (   #    /3'/ 4#     *  +   4#     *     5#6#7     88888888887   4#    5 $ %  +!5 &888888888888888 22222222222222222222223 4  0"00 "22222222222222222222222  5.*, * 5.*$#*6#6      7      #++   $  &  0/0/  0/0/   9 :;     1( $  &  ////  ////   $  &  0/0/  0/0/ 7777777777777777777777" 0     83' + #++     2222222222#++  2222222222  2222222 $ &22222222 <= ;  0/0/ 2222222222222222222222222222222222222222222222 #++   0/0/ 7777777777777777777777" 0     83' + #++     2222222222#++  2222222222  2222222 $ &22222222 <= ;6  /0/0    >> 2222222222222222222222222222222222222222222222 #++   0/0/ 22222222222222222222222220"9 2222222222222222222222222222222 2222222222222222222222#"( <(7(?(9<(7 + 9 :  777777777777777777777777777777777777777777 :"";.6:' 9 :!  "! 7= 9 :  22222222222222222222222220"9 2222222222222222222222222222222 2222222222222222222222#"( <<#7(?(9<(7 + 9 :  777777777777777777777777777777777777777777 :"";.6:% 9 :!  "! 7= 9 :  2222222222222222222222  <1"="  1 0 "002222222222222222222 7777777777777777777777" 0     83' + #++    + 9 :  7777777777777777777777" 0     83' + #++    + 9 :   22222222222#;* !>#62222222222222  ; *       6=       #         ; * 7 *#    % (    ; * $ 2& 22222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222 #++   ,'. 9 : ="!9: ////    ,'.   7    ; * 7 *#    % (    ; * $ 2& 22222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222 #++   @3@, 9 : ="!9:0 ////    @3@, * 5.* !>**> * 5. 5 !> =?@"#$+=A' /B 5. %%%C!7+*,6? * 5. &C&&!7+*,6  222222222223*<#*6!*6 *2222222222222 7777777777777777777777" 0     83' + 9 :  88888888889 : ="!9:8888888888  02A 7 ; *   ///  '2%     B    !  7  *7 ; *  <2  7  *7 ; *   $-C()   & ///  <2  7  *7 ; *   $-C()   & ///     1   #   22222222222222222222   =?  $ 2& /0,   =?    *2( $ 2& /0,      $ 2& ///B ///C      $ 2& ///B ///C    !< =7= #! $ 2& /0,  #  !< =7= #! $ 2& ///  ?  9($ 2& ///      $   D   D(&1 ?  ///C 7777777777777777777777" 0     83' + 9 :  88888888889 : ="!9:0 8888888888  02A 7 ; *   /'>>  '2%     B    !  7  *7 ; *  <2  7  *7 ; *   $-C()   & /00  <2  7  *7 ; *   $-C()   & /0 Williams 1 - Predeveloped Water Quality Flow Rates Williams 1 - Postdeveloped Water Quality Flow Rates     1   #   22222222222222222222   =?  $ 2& .-''   =?    *2( $ 2& .-''      $ 2& ///B ///C      $ 2& ///B ///C    !< =7= #! $ 2& .-''  #  !< =7= #! $ 2& ///  ?  9($ 2& ///      $   D   D(&1 ?  ///C  22222222222.! * #*2222222222222 #       "  9 : ="!9: #      "  9 : ="!9:0  222 *+.!;D#!6 *222       " 5 *6 *   *            $A & 7 ; * $& $A & 7 ; * $& 2222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222  02A  @'(2/, 02A   /'>>  '2A  '>0(2/, '2A   /3-,  /2A  .0(2/, /2A   /-0'  0'2A  .0@(2/, 0'2A   '/  '/2A  .0.(2/, '/2A   @.  //2A  .0>(2/, //2A   >,@  0//2A  .0>(2/, 0//2A   >-3  '//2A  .0>(2/, '//2A   -3>  88 #;"  :7 ; * ;        2222; #* +!2222 ()      '/C 0$%+ 9 ; (E /C&  -.'',C 9 % ) () '/C 0 0$%+ 9 ; (E /C& 3@00//>C 9 % ) ()  0 '/$%+  ; /C&  -----/C 9   ()  0 '/$%+  ; '/C&  ///C 9 2222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222 9<75< 7(#6 "( 9 2222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222 ————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.55 Program License Number: 201910002 Project Simulation Performed on: 11/19/2021 2:53 PM Report Generation Date: 11/19/2021 2:55 PM ————————————————————————————————— Input File Name: Treatment Areas_W2_pre&post development.fld Project Name: Renton WQ Retrofit Analysis Title: Comments: Predeveloped (forested) and postdeveloped for W2 ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Climatic Region Number: 13 Full Period of Record Available used for Routing Precipitation Station : 96003205 Puget East 32 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961032 Puget East 32 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 8.560 8.560 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 8.560 8.560 ----------------------SCENARIO: PREDEVELOPED_W2 Number of Subbasins: 1 ---------- Subbasin : W2 ---------- -------Area (Acres) -------- Outwash Forest 8.560 ---------------------------------------------- Subbasin Total 8.560 ----------------------SCENARIO: POSTDEVELOPED_W2 Number of Subbasins: 1 ---------- Subbasin : W2 ---------- -------Area (Acres) -------- Outwash Grass 0.856 Impervious 7.704 ---------------------------------------------- Subbasin Total 8.560 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED_W2 Number of Links: 1 ------------------------------------------ Link Name: New Copy Lnk1 Link Type: Copy Downstream Link: None ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED_W2 Number of Links: 1 ------------------------------------------ Link Name: New Copy Lnk2 Link Type: Copy Downstream Link: None **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED_W2 Number of Subbasins: 1 Number of Links: 1 ----------------------SCENARIO: POSTDEVELOPED_W2 Number of Subbasins: 1 Number of Links: 1 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: W2 1488.088 Link: New Copy Lnk1 0.000 _____________________________________ Total: 1488.088 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: W2 200.918 Link: New Copy Lnk2 0.000 _____________________________________ Total: 200.918 Total Predevelopment Recharge is Greater than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 9.418 ac-ft/year, Post Developed: 1.272 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED_W2 Number of Links: 1 ********** Link: New Copy Lnk1 ********** 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 0.00 cfs Off-line Design Discharge Rate (91% Exceedance): 0.00 cfs Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 0.99 Inflow Volume Including PPT-Evap (ac-ft): 0.99 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 0.99 Secondary Outflow To Downstream System (ac-ft): 0.00 Volume Lost to ET (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 0.00% ----------------------SCENARIO: POSTDEVELOPED_W2 Number of Links: 1 ********** Link: New Copy Lnk2 ********** 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 0.95 cfs Off-line Design Discharge Rate (91% Exceedance): 0.52 cfs Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 2625.41 Inflow Volume Including PPT-Evap (ac-ft): 2625.41 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 2625.41 Secondary Outflow To Downstream System (ac-ft): 0.00 Volume Lost to ET (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 0.00% ***********Compliance Point Results ************* Scenario Predeveloped_W2 Compliance Link: New Copy Lnk1 Scenario Postdeveloped_W2 Compliance Link: New Copy Lnk2 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 6.148E-03 2-Year 2.493 5-Year 6.704E-03 5-Year 3.359 10-Year 6.832E-03 10-Year 3.918 25-Year 6.880E-03 25-Year 4.874 50-Year 6.890E-03 50-Year 6.190 100-Year 6.897E-03 100-Year 7.772 200-Year 6.898E-03 200-Year 8.038 500-Year 6.898E-03 500-Year 8.383 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance **** Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): 91655.3% FAIL Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): 742199.6% FAIL Maximum Excursion from Q2 to Q50 (Must be less than 10%): 99999.0% FAIL Percent Excursion from Q2 to Q50 (Must be less than 50%): 100.0% FAIL ------------------------------------------------------------------------------------------------- FLOW DURATION DESIGN CRITERIA: FAIL ------------------------------------------------------------------------------------------------- ————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.55 Program License Number: 201910002 Project Simulation Performed on: 12/14/2021 11:32 AM Report Generation Date: 12/14/2021 11:33 AM ————————————————————————————————— Input File Name: Treatment Areas_W3_entirebasin.fld Project Name: Renton WQ Retrofit Analysis Title: Comments: Updated treated area to 4.15 ac for W3 ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Climatic Region Number: 13 Full Period of Record Available used for Routing Precipitation Station : 96003205 Puget East 32 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961032 Puget East 32 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 5.030 5.030 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 5.030 5.030 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : W3 ---------- -------Area (Acres) -------- Outwash Forest 5.030 ---------------------------------------------- Subbasin Total 5.030 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 ---------- Subbasin : W3 ---------- -------Area (Acres) -------- Outwash Grass 0.500 Impervious 4.530 ---------------------------------------------- Subbasin Total 5.030 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 ------------------------------------------ Link Name: New Copy Lnk1 Link Type: Copy Downstream Link: None ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED Number of Links: 1 ------------------------------------------ Link Name: New Copy Lnk2 Link Type: Copy Downstream Link: None **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 1 ----------------------SCENARIO: POSTDEVELOPED Number of Subbasins: 1 Number of Links: 1 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: W3 874.425 Link: New Copy Lnk1 0.000 _____________________________________ Total: 874.425 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: W3 117.359 Link: New Copy Lnk2 0.000 _____________________________________ Total: 117.359 Total Predevelopment Recharge is Greater than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 5.534 ac-ft/year, Post Developed: 0.743 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 ********** Link: New Copy Lnk1 ********** 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 0.00 cfs Off-line Design Discharge Rate (91% Exceedance): 0.00 cfs Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 0.58 Inflow Volume Including PPT-Evap (ac-ft): 0.58 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 0.58 Secondary Outflow To Downstream System (ac-ft): 0.00 Volume Lost to ET (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 0.00% ----------------------SCENARIO: POSTDEVELOPED Number of Links: 1 ********** Link: New Copy Lnk2 ********** 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 0.56 cfs Off-line Design Discharge Rate (91% Exceedance): 0.30 cfs Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 1543.76 Inflow Volume Including PPT-Evap (ac-ft): 1543.76 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 1543.76 Secondary Outflow To Downstream System (ac-ft): 0.00 Volume Lost to ET (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 0.00% ***********Compliance Point Results ************* Scenario Predeveloped Compliance Link: New Copy Lnk1 Scenario Postdeveloped Compliance Link: New Copy Lnk2 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 3.613E-03 2-Year 1.466 5-Year 3.939E-03 5-Year 1.975 10-Year 4.015E-03 10-Year 2.304 25-Year 4.043E-03 25-Year 2.866 50-Year 4.049E-03 50-Year 3.640 100-Year 4.053E-03 100-Year 4.570 200-Year 4.053E-03 200-Year 4.726 500-Year 4.053E-03 500-Year 4.929 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance **** Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): 91667.8% FAIL Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): 742329.2% FAIL Maximum Excursion from Q2 to Q50 (Must be less than 10%): 99999.0% FAIL Percent Excursion from Q2 to Q50 (Must be less than 50%): 100.0% FAIL ------------------------------------------------------------------------------------------------- FLOW DURATION DESIGN CRITERIA: FAIL ------------------------------------------------------------------------------------------------- ————————————————————————————————— MGS FLOOD PROJECT REPORT Program Version: MGSFlood 4.55 Program License Number: 201910002 Project Simulation Performed on: 12/14/2021 11:03 AM Report Generation Date: 12/14/2021 11:05 AM ————————————————————————————————— Input File Name: Treatment Areas_W3_4.15ac.fld Project Name: Renton WQ Retrofit Analysis Title: Comments: Updated treated area to 4.15 ac for W3 ———————————————— PRECIPITATION INPUT ———————————————— Computational Time Step (Minutes): 15 Extended Precipitation Time Series Selected Climatic Region Number: 13 Full Period of Record Available used for Routing Precipitation Station : 96003205 Puget East 32 in_5min 10/01/1939-10/01/2097 Evaporation Station : 961032 Puget East 32 in MAP Evaporation Scale Factor : 0.750 HSPF Parameter Region Number: 1 HSPF Parameter Region Name : USGS Default ********** Default HSPF Parameters Used (Not Modified by User) *************** ********************** WATERSHED DEFINITION *********************** Predevelopment/Post Development Tributary Area Summary Predeveloped Post Developed Total Subbasin Area (acres) 4.150 4.150 Area of Links that Include Precip/Evap (acres) 0.000 0.000 Total (acres) 4.150 4.150 ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 ---------- Subbasin : W3 ---------- -------Area (Acres) -------- Outwash Forest 4.150 ---------------------------------------------- Subbasin Total 4.150 ----------------------SCENARIO: POSTDEVELOPED - TREATED Number of Subbasins: 1 ---------- Subbasin : W3 ---------- -------Area (Acres) -------- Outwash Grass 0.415 Impervious 3.735 ---------------------------------------------- Subbasin Total 4.150 ************************* LINK DATA ******************************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 ------------------------------------------ Link Name: New Copy Lnk1 Link Type: Copy Downstream Link: None ************************* LINK DATA ******************************* ----------------------SCENARIO: POSTDEVELOPED - TREATED Number of Links: 1 ------------------------------------------ Link Name: New Copy Lnk2 Link Type: Copy Downstream Link: None **********************FLOOD FREQUENCY AND DURATION STATISTICS******************* ----------------------SCENARIO: PREDEVELOPED Number of Subbasins: 1 Number of Links: 1 ----------------------SCENARIO: POSTDEVELOPED - TREATED Number of Subbasins: 1 Number of Links: 1 ***********Groundwater Recharge Summary ************* Recharge is computed as input to Perlnd Groundwater Plus Infiltration in Structures Total Predeveloped Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: W3 721.444 Link: New Copy Lnk1 0.000 _____________________________________ Total: 721.444 Total Post Developed Recharge During Simulation Model Element Recharge Amount (ac-ft) ----------------------------------------------------------------------------------------------- Subbasin: W3 97.408 Link: New Copy Lnk2 0.000 _____________________________________ Total: 97.408 Total Predevelopment Recharge is Greater than Post Developed Average Recharge Per Year, (Number of Years= 158) Predeveloped: 4.566 ac-ft/year, Post Developed: 0.617 ac-ft/year ***********Water Quality Facility Data ************* ----------------------SCENARIO: PREDEVELOPED Number of Links: 1 ********** Link: New Copy Lnk1 ********** 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 0.00 cfs Off-line Design Discharge Rate (91% Exceedance): 0.00 cfs Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 0.48 Inflow Volume Including PPT-Evap (ac-ft): 0.48 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 0.48 Secondary Outflow To Downstream System (ac-ft): 0.00 Volume Lost to ET (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 0.00% ----------------------SCENARIO: POSTDEVELOPED - TREATED Number of Links: 1 ********** Link: New Copy Lnk2 ********** 15-Minute Timestep, Water Quality Treatment Design Discharge On-line Design Discharge Rate (91% Exceedance): 0.46 cfs Off-line Design Discharge Rate (91% Exceedance): 0.25 cfs Infiltration/Filtration Statistics-------------------- Inflow Volume (ac-ft): 1272.83 Inflow Volume Including PPT-Evap (ac-ft): 1272.83 Total Runoff Infiltrated (ac-ft): 0.00, 0.00% Total Runoff Filtered (ac-ft): 0.00, 0.00% Primary Outflow To Downstream System (ac-ft): 1272.83 Secondary Outflow To Downstream System (ac-ft): 0.00 Volume Lost to ET (ac-ft): 0.00 Percent Treated (Infiltrated+Filtered+ET)/Total Volume: 0.00% ***********Compliance Point Results ************* Scenario Predeveloped Compliance Link: New Copy Lnk1 Scenario Postdeveloped - Treated Compliance Link: New Copy Lnk2 *** Point of Compliance Flow Frequency Data *** Recurrence Interval Computed Using Gringorten Plotting Position Predevelopment Runoff Postdevelopment Runoff Tr (Years) Discharge (cfs) Tr (Years) Discharge (cfs) ---------------------------------------------------------------------------------------------------------------------- 2-Year 2.981E-03 2-Year 1.209 5-Year 3.250E-03 5-Year 1.629 10-Year 3.312E-03 10-Year 1.899 25-Year 3.335E-03 25-Year 2.363 50-Year 3.340E-03 50-Year 3.001 100-Year 3.344E-03 100-Year 3.768 200-Year 3.344E-03 200-Year 3.897 500-Year 3.344E-03 500-Year 4.064 ** Record too Short to Compute Peak Discharge for These Recurrence Intervals **** Flow Duration Performance **** Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): 91655.3% FAIL Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): 742198.8% FAIL Maximum Excursion from Q2 to Q50 (Must be less than 10%): 99999.0% FAIL Percent Excursion from Q2 to Q50 (Must be less than 50%): 100.0% FAIL ------------------------------------------------------------------------------------------------- FLOW DURATION DESIGN CRITERIA: FAIL ------------------------------------------------------------------------------------------------- Sub-basin Total Area (ac) Pervious Area (ac)Impervious Area1 (ac)Treated Area (ac) Untreated Area (ac) 25-yr (cfs) 100-yr (cfs) On-line (cfs) Off-line (cfs) On-line (cfs) Off-line (cfs)Williams-12.020.201.82-2.021.151.830.220.12--Williams-28.560.867.708.56-4.877.770.950.520.950.52Williams-35.03 0.50 4.53 4.15 0.88 2.86 4.57 0.56 0.30 0.46 0.25TOTAL15.61 1.56 14.05 1. Percent impervious = 90%Sub-basin AreasDesign Storm Flow RatesEntire Sub-BasinWater Quality Flow RatesTreated AreaNotes:Water Quality Flow RatesEntire Sub-Basin APPENDIX E 30 Percent Design Cost Estimate THIS PAGE INTENTIONALLY BLANK. APPENDIX F Operations and Maintenance Information THIS PAGE INTENTIONALLY BLANK.