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23-101488_Preliminary TIR_3-22-23 Western Washington Division Eastern Washington Division 165 NE Juniper St., Ste 201, Issaquah, WA 98027 108 East 2nd Street, Cle Elum, WA 98922 Phone: (425) 392-0250 Fax: (425) 391-3055 Phone: (509) 674-7433 Fax: (509) 674-7419 www.EncompassES.net PRELIMINARY TECHNICAL INFORMATION REPORT For APL Short Plat 2240 S 288th Street Federal Way, WA 98003 March 17, 2023 03/17/2023 Prepared by: Gabe Garner Encompass Engineering Job No. 21735 Prepared For: American Pride Lending, LLC PO Box 1226 Kent, WA 98035 American Pride Lending LLC Short Plat Preliminary Technical Information Report 03/17/2023 Page i Table of Contents List of Figures ................................................................................................................................. i I. PROJECT OVERVIEW .............................................................................................................. 1 II. CONDITIONS AND REQUIREMENTS SUMMARY ..................................................................... 6 III. OFF-SITE ANALYSIS ................................................................................................................. 1 IV. FLOW CONTROL, LOW IMPACT DEVELOPMENT (LID), AND WATER QUALITY FACILITY ANALYSIS AND DESIGN .................................................................................................................. 6 VI. SPECIAL REPORTS AND STUDIES ............................................................................................ 8 VII. OTHER PERMITS ..................................................................................................................... 8 VIII. CSWPPP ANALYSIS AND DESIGN ............................................................................................ 9 IX. BOND QUANTITIES and DECLARATION of COVENANT ........................................................... 9 X. OPERATION AND MAINTENANCE MANUAL ........................................................................... 9 List of Figures Figure 1 – TIR Worksheet Figure 2 – Vicinity Map Figure 3 – Soils Map and Legend Figure 4 – Existing Conditions Map Figure 5 – Developed Conditions Map Figure 6 – Drainage Review Flow Chart Figure 7 – Downstream Map Appendix A Geotechnical Evaluation by Earth Solutions NW, LLC dated June 3, 2022. Appendix B Limited Please II Environmental Site Assessment by Earth Solutions NW, LLC dated May 16, 2022 Appendix C No Action for Tacoma Smelter Plume Letter by Washington State Department of Ecology dates June 22, 2022. Appendix D WWHM Output Appendix E Approved Street Modification Request dated November 2, 2022. American Pride Lending LLC Short Plat Preliminary Technical Information Report 03/17/2023 Page 1 I. PROJECT OVERVIEW Project: APL Short Plat Site Address: 2240 S 288th Street, Federal Way, WA 98003 King County Tax Parcel: 332204-9023 Site Area: 39,006 SF (0.89 AC) – as surveyed Zoning District: RS7.2 Abbreviated Legal Description: PORTION OF S 30 ACRES OF SE QTR SW QTR STR 33-22-04 SLY & ELY OF LINE BEG 330 FT SOUTH OF NE CORNER OF SD SUBD TH WEST 130 FT TH SOUTH TO N LINE OF S 440 FT TH WEST 640 FT TH SOUTH 225 FT TH EAST 80 FT TH SOUTH TO S LINE OF SUBD EXC E 115 FT OF S 200 FT & EXC COUNTY ROAD (S 288TH ST) & EXC W 150 FT OF E 540 FT OF N 142 FT OF S 172 FT & LESS ANY PORTION PLATTED WITHIN ARMELL ADDITION (VOL 85, PG 29) & EXC PORTION WEST OF E 540 FT OF SD SE QTR SW QTR Figure 2: Vicinity Map Pre-developed Site Conditions: The project is located on tax parcel number 332204-9023 in the City of Federal Way. The 39,006 SF (0.89 AC) lot is zoned RS7.2. The property is currently undeveloped and can be accessed via South 288th Street to the south. Stormwater from the site generally sheet flows to the southwest across moderate slopes ranging from 2-15% with some localized steep slopes in excess of 15%. Existing vegetation on the site includes small trees, shrubs, and grasses. Please refer to Section III of this Technical Information Report (TIR) for a more detailed description of the downstream flowpath. An Existing Conditions Map is provided as Figure 4 at the end of this section. American Pride Lending LLC Short Plat Preliminary Technical Information Report 03/17/2023 Page 2 Critical Areas: There were no critical areas located on or near the subject site according to King County iMap or the City of Federal Way Critical Area Map. A Limited Phase II Environmental Site Assessment was conducted by Earth Solutions NW (Appendix B), and a No Action Needed Letter from Washington State Department of Ecology (DOE) has been issued for the project (Appendix C). Soils: The soils on site have been classified by the United States Department of Agriculture (USDA) National Resource Conservation Service (NRCS) Web Soils Survey as Arents, Alderwood material (AmC) – (see Figure 3 below). The Geotechnical Evaluation by Earth Solutions NW, LLC (Appendix A) classifies the soils as glacial till deposits. Based on the report, ESNW does not recommend incorporating infiltration into the overall stormwater design due to the low permeability of the underlying soils and evidence of seasonal groundwater seepage as shallow as 3 feet below grade. Figure 3: Soils Map and Legend American Pride Lending LLC Short Plat Preliminary Technical Information Report 03/17/2023 Page 3 Developed Site Conditions: This project proposes a new development with two (2) single-family lots, an Access/Utility Tract, a 20 FT ROW dedication, a 10 FT Landscape Tract adjacent to the ROW dedication, and a large Open Space/NGRA Tract. Lot 1 is a rectangular shaped lot located in the southwest corner of the site with an area of 7,200 SF (0.165 AC). Lot 2 is a rectangular shaped lot located in the northwest corner of the site with an area of 7,200 SF (0.165 AC). The 20 FT ROW dedication is 5,498 SF (0.126 AC) and stretches along the site’s frontage adjacent to South 288th Street. The 10 FT Landscape Tract is 2,498 SF (0.057 AC) and is located just north of the ROW dedication. Frontage improvements along South 288th Street have been waived by the City via the Street Modification Request that was approved on November 2, 2022 (Appendix E). Both Lots 1 and 2 are accessed from South 288th Street via a proposed 16 FT wide joint-use driveway that runs through a 25 FT wide Access/Utility Tract (1,375 SF). A residential driveway apron will be provided off South 288th Street near the southwest corner of the site. The proposed joint-use driveway and apron include 270 SF of new pollution generating impervious surface (PGIS) in the existing public ROW, 320 SF of new PGIS in the ROW dedication area, and 1,031 SF of new PGIS within the Access/Utility Tract. The total new PGIS associated with the joint-use driveway is 1,621 SF. Future private driveways for Lots 1 and 2 are estimated to include 400 SF and 1,000 SF of new PGIS, respectively. Reduced impervious surface covenants will be recorded on both Lots 1 and 2 in order to satisfy Flow Control BMP requirements for the future single-family building permits. These covenants will limit impervious surface coverage on Lot 1 to 2,500 SF and Lot 2 to 3,000 SF. All fire and emergency access will be provided from South 288th Street; therefore, the furthest corner of any proposed structure with an approved automatic sprinkler system must be within 180 FT walking distance of S 288th Street via the joint-use driveway. The maximum possible future building footprints have been shown on the plans based on these fire access requirements, required building setbacks, and the proposed reduced impervious surface covenants. The maximum future building footprint on Lot 1 was determined to be 1,800 SF with a maximum rooftop area of approximately 2,100 SF. The maximum future building footprint on Lot 2 was determined to be 1,700 SF with a maximum rooftop area of approximately 2,000 SF. The overall project will result in the addition of 4,100 SF of new non-pollution generating impervious surface (future rooftops) and 3,021 SF of new PGIS (joint-use driveway and future private driveways). The total proposed impervious surface associated with the short plat is 7,121 SF. New non-pollution generating pervious surface associated with the short plat and future lots includes 9,566 SF of new lawn. The Open Space/NGRA Tract and the Landscape Tract are proposed to reserve and/or be replanted with dense native vegetation as part of the short plat. The project is a New Development located in the Lower Green River Drainage Basin within the Urban Growth Area (UGA). The City of Federal Way Flow Control Applications Map classifies the site as a Conservation (Level 2) Flow Control Area, and the Water Quality Applications Map classifies the site an Enhanced Basic Water Quality Treatment Area. In addition, the construction of the plat infrastructure is subject to the Small Subdivision and Urban Subdivision Project BMP Requirements and the future lots are subject to Individual Small Lot BMP Requirements. Please refer to Section II and Section IV of this Technical Information Report (TIR) for additional discussion on the stormwater design. A Developed Conditions Map is provided as Figure 5 at this end of this Section. S 288TH ST23RD PLACE SNORTH AMERICAN PRIDE LENDING LLC 2240 S 288TH WAY FEDERAL WAY, WA 98003 REVISIONS JOB NO. DATE SCALE SHEET Encompass Eastern Washington Division 407 Swiftwater Blvd. ▪ Cle Elum, WA 98922 ▪ Phone: (509) 674-7433 Western Washington Division 165 NE Juniper Street, Suite 201 ▪ Issaquah, WA 98027 ▪ Phone: (425) 392-0250 ENGINEERING & SURVEYING 1 of 1EXISTING CONDITIONS S 288TH ST23RD PLACE SOPEN SPACE/NGRA TRACTLOT 2LANDSCAPE TRACT20' ROW DEDICATIONACCESS /UTILITY TRACTNORTH AMERICAN PRIDE LENDING LLC 2240 S 288TH WAY FEDERAL WAY, WA 98003 REVISIONS JOB NO. DATE SCALE SHEET Encompass Eastern Washington Division 407 Swiftwater Blvd. ▪ Cle Elum, WA 98922 ▪ Phone: (509) 674-7433 Western Washington Division 165 NE Juniper Street, Suite 201 ▪ Issaquah, WA 98027 ▪ Phone: (425) 392-0250 ENGINEERING & SURVEYING 1 of 1PROPOSED CONDITIONS PROPOSED IMPERVIOUS SURFACE SUMMARY: American Pride Lending LLC Short Plat Preliminary Technical Information Report 03/17/2023 Page 6 II. CONDITIONS AND REQUIREMENTS SUMMARY The 2021 King County Surface Water Design Manual (KCSWDM) and the City of Federal Way Addendum were used to determine the drainage review requirements for the project. This subdivision project is subject to a Full Drainage Review per Section 1.1.2.4 of the 2021 KCSWDM and must meet all Core and Special Requirements. See Figure 6 below for more information on how the type of drainage review required was determined. Figure 6: Drainage Review Flow Chart American Pride Lending LLC Short Plat Preliminary Technical Information Report 03/17/2023 Page 7 Core Requirements Core Requirement #1: Discharge at the Natural Location In the existing condition, stormwater runoff from the site sheet flows across the site toward South 288th Street. Runoff then flows west along the northern curb flowline for South 288th Street until entering the underground public storm system near the South 288th Street/22nd Avenue South intersection. In the developed condition, runoff from all proposed pervious and impervious surfaces will be discharged to the existing public storm system in S 288 th Street, which is the natural discharge location for the site. Please refer to the full Downstream Analysis provided in Section III of this TIR. Core Requirement #2: Offsite Analysis A Level 1 Downstream Analysis per section 1.2.2 of the KCSWDM was performed. See Section III of this TIR for results of Level 1 Downstream Analysis. Core Requirement #3: Flow Control Facilities The project site is located within the Lower Green River Drainage Basin which is classified as a Conservation (Level 2) Flow Control Area on the City of Federal Way Flow Control Applications Map. This requires the project to match the developed discharge durations to the predeveloped durations for the range of predeveloped discharge rates from 50% of the 2-year peak flow up to the full 50-year peak flow, match the developed peak discharge rates to predeveloped peak discharge rates for the 2- and 10-year return periods. Historic site conditions (forested) have been assumed for the predeveloped site conditions. The proposed development only results in a 0.0999 CFS increase in the 100-year flow using 1-hour time steps, which is below the exemption threshold of 0.10 CFS. No flow control facilities are proposed at this time; however, flow control BMPs will be implemented as described under Core Requirement #9. Please refer to Appendix D for a copy of the full WWHM data output. See Chapter IV of this TIR for additional discussion on the analysis. Core Requirement #4: Conveyance System Conveyance system analysis will be completed during final engineering if requested by the City. Core Requirement #5: Construction Stormwater Pollution Prevention (CSWPPP) A Construction Stormwater Pollution Prevention Plan (CSWPPP) and Temporary Erosion and Sediment Control (TESC) plan providing BMPs to be implemented during construction will be provided with final engineering. Please refer to Section VIII of this TIR for additional discussion on the CSWPPP. Core Requirement #6: Maintenance and Operations An Operation and Maintenance Manual will be provided with final engineering if requested by the City. Core Requirement #7: Financial Guarantees and Liability The owner will arrange for any financial guarantees and liabilities required by the permit. American Pride Lending LLC Short Plat Preliminary Technical Information Report 03/17/2023 Page 8 Core Requirement #8: Water Quality Facilities The project site is located within the “Enhanced Basic Water Quality Treatment Menu Required” area of the City of Federal Way Water Quality Applications Map. Per Section 1.2.8 of the City of Federal Way Addendum to the KCSWDM, New Developments are to refer directly to the 2021 KCSWDM for both impervious and pervious surface requirements that trigger Core Requirement #8 for water quality. Per Section 1.2.8 of the 2021 KCSWDM there are four (4) possible exemptions from Core Requirement #8. The first of which is the Surface Area Exemption that states a proposed project is exempt if it meets all of the following criteria: • Less than 5,000 square feet of new plus replaced Pollution Generating Impervious Surface (PGIS) will be created, AND • Less than ¾ acre of new Pollution Generating Pervious Surface (PGPS) will be added. As described in detail in Section I of this TIR, the overall project will result in the addition of only 3,021 SF of new PGIS (joint-use driveway and future private driveways), which is less than the 5,000 SF exemption threshold above. No new PGPS is proposed. Therefore, the Surface Area Exemption in Section 1.2.8 of the 2021 KCSWDM is achieved, and water quality treatment is not required for this project. Core Requirement #9: Flow Control BMPs This project is located within the Urban Growth Area (UGA) on a site less than 5 acres in size. The construction of the plat infrastructure is subject to the Small Subdivision and Urban Subdivision Projects BMP Requirements detailed in Section 1.2.9.3.2 of the 2021 KCSWDM. The proposed lots are less than 22,000 SF each; therefore, Individual Small Lot BMPs for the future single -family residences have been evaluated per Section 1.2.9.2.1 of the 2021 KSWDM. Plat Infrastructure BMPs Target impervious surfaces associated with the plat infrastructure include the 16 FT wide joint use driveway within the existing/future ROW and within the proposed Access/Utility Tract. Flow Control BMPs have been evaluated for the target impervious surfaces associated with the short plat and have been selected to the maximum extent feasible as described below: 1. Full Dispersion: Full dispersion is not feasible. The minimum required 100 FT native vegetated flowpath is not available on-site downslope of the joint-use driveway. 2. Full Infiltration: Full infiltration is not feasible. The Geotechnical Evaluation by Earth Solutions NW, LLC (Appendix A) classifies the soils as glacial till deposits. Based on the report, ESNW does not recommend incorporating infiltration into the overall stormwater design due to the low permeability of the underlying soils and evidence of seasonal groundwater seepage as shallow as 3 feet below grade. 3. Limited Infiltration/Bioretention/Permeable Pavement: Limited infiltration, bioretention, and permeable pavement are not feasible as they rely on the ability of the underlying soils to infiltrate stormwater. The Geotechnical Evaluation American Pride Lending LLC Short Plat Preliminary Technical Information Report 03/17/2023 Page 9 by Earth Solutions NW, LLC (Appendix A) classifies the soils as glacial till deposits. Based on the report, ESNW does not recommend incorporating infiltration into the overall stormwater design due to the low permeability of the underlying soils and evidence of seasonal groundwater seepage as shallow as 3 feet below grade. 4. Basic Dispersion: Basic dispersion is not feasible. The minimum required 25 FT vegetated flowpath is not available on-site downslope of the joint-use driveway. 5. Soil Moisture Holding Capacity: Feasible. The soil moisture holding capacity of all new pervious surfaces associated with the short plat will be protected in accordance with KCC 16.82.100 (F) and (G). KCC 16.82.100(F) requires that the duff layer or native topsoil be retained to the maximum extent practicable. KCC 16.82.100(G) requires soil amendment to mitigate for lost moisture holding capacity where compaction or removal of some or all of the duff layer or underlying topsoil has occurred. The amendment must be such that the replaced topsoil is a minimum of 8 inches thick, unless the applicant demonstrates that a different thickness will provide conditions equivalent to the soil moisture holding capacity native to the site. The replaced topsoil must have an organic content of 5-10% dry weight and a pH suitable for the proposed surface vegetation (for most soils in King Cou nty, 4 inches of well-rotted compost tilled into the top 8 inches of soil is sufficient to achieve the organic content standard.) The amendment must take place between May 1 and October 1. Individual Lot BMPs Target impervious surfaces associated with the individual lots include the future private driveways and rooftops on Lots 1 and 2. Flow Control BMPs have been evaluated for the target impervious surfaces associated with the short plat and have been selected to the maximum extent feasible as described below: 1. Full Dispersion: Full dispersion is not feasible. The minimum required 100 FT native vegetated flowpath is not available on-site downslope of the individual lots. 2. Full Infiltration: Full infiltration is not feasible. The Geotechnical Evaluation by Earth Solutions NW, LLC (Appendix A) classifies the soils as glacial till deposits. Based on the report, ESNW does not recommend incorporating infiltration into the overall stormwater design due to the low permeability of the underlying soils and evidence of seasonal groundwater seepage as shallow as 3 feet below grade. 3. Limited Infiltration/Bioretention/Permeable Pavement: Limited infiltration, bioretention, and permeable pavement are not feasible as they rely on the ability of the underlying soils to infiltrate stormwater. The Geotechnical Evaluation by Earth Solutions NW, LLC (Appendix A) classifies the soils as glacial till deposits. Based on the report, ESNW does not recommend incorporating infiltration into the overall American Pride Lending LLC Short Plat Preliminary Technical Information Report 03/17/2023 Page 10 stormwater design due to the low permeability of the underlying soils and evidence of seasonal groundwater seepage as shallow as 3 feet below grade. 4. Basic Dispersion: Basic dispersion is not feasible. The minimum required 25 FT vegetated flowpath is not available on-site downslope of the individual lots. 5. Reduced Impervious Surface Credit: Feasible. Lots zoned RS7.2 are allowed to include up to 60% impervious coverage; therefore, each of the proposed 7,200 SF lots is allowed to include 4,320 SF of impervious surface. Per Section C.2.9.2 of the 2021 KCSWDM, any recorded limit on total impervious surface on lots less than 22,000 SF that is less than the norm of 4,000 SF qualifies for a restricted footprint credit. For every square foot that the recorded limit is below the norm, an equal area of actual target impervious surface is credited as mitigated. Reduced impervious surface covenants will be recorded on both Lots 1 and 2. These covenants will limit impervious surface coverage on Lot 1 to 2,500 SF and Lot 2 to 3,000 SF. Therefore, Lot 1 will receive a 1,500 SF credit and Lot 2 will receive a 1,000 SF credit toward meeting the required flow control BMPs. Per Section 1.2.9.2.1.5, lots less than 11,000 SF are required to mitigate at least 10% of the lot area. Therefore, each 7,200 SF lot is required to mitigate at least 720 SF of the target impervious surfaces. The proposed reduced impervious surface covenants exceed this minimum requirement; therefore, Core Requirement #9 is met for the future building permits and no further BMPs are required to be evaluated. 6. Soil Moisture Holding Capacity: Feasible. The soil moisture holding capacity of all new pervious surfaces associated with the short plat will be protected in accordance with KCC 16.82.100 (F) and (G). KCC 16.82.100(F) requires that the duff layer or native topsoil be retained to the maximum extent practicable. KCC 16.82.100(G) requires soil amendment to mitigate for lost moisture holding capacity where compaction or removal of some or all of the duff layer or underlying topsoil has occurred. The amendment must be such that the replaced topsoil is a minimum of 8 inches thick, unless the applicant demonstrates that a different thickness will provide conditions equivalent to the soil moisture holding capacity native to the site. The replaced topsoil must have an organic content of 5-10% dry weight and a pH suitable for the proposed surface vegetation (for most soils in King County, 4 inches of well-rotted compost tilled into the top 8 inches of soil is sufficient to achieve the organic content standard.) The amendment must take place between May 1 and October 1. American Pride Lending LLC Short Plat Preliminary Technical Information Report 03/17/2023 Page 11 Special Requirements Special Requirement #1: Other Adopted Area-Specific Requirements Critical Drainage Areas – N/A Master Drainage Plan – N/A Basin Plan – N/A Salmon Conservation Plan – N/A Stormwater Compliance Plans – N/A Lake Management Plan – N/A Flood Hazard Mitigation Plan – N/A Shared Facility Drainage Plan – N/A Special Requirement #2: Flood Hazard Area Delineation The project is not located within a delineated FEMA flood zone. Special Requirement #3: Flood Protection Facilities This project does not rely on or propose to modify or construct a new flood protection facility. Special Requirement #4: Source controls Source control is not warranted for this residential short plat project. Special Requirement #5: Oil Control This residential short plat project is not considered high-use or in need of oil control. American Pride Lending LLC Short Plat Preliminary Technical Information Report 03/17/2023 Page 1 III. OFF-SITE ANALYSIS Task 1: Study Area Definition and Maps The project is located on tax parcel number 332204-9023 in the City of Federal Way. The site is contained within a single drainage basin, Lower Green River – West, in the Duwamish – Green River watershed. The site is located within a single Threshold Discharge Area (TDA). Per the Geotechnical Evaluation by Earth Solutions NW, LLC (Appendix A), the site is underlain by glacial till deposits. Therefore, stormwater from the site does not typically infiltrate into the on-site soils; stormwater generally sheet flows to the southwest across moderate slopes ranging from 2-15%. The site does include some localized steep slopes in excess of 15%. An Existing Conditions Map is included as Figure 4 in this TIR. The study area for this analysis extends downstream for approximately ¼ mile, where the stormwater is conveyed through the South 288th Street public stormwater system. A Downstream Map showing the study area is included in Figure 7 on the following page. Task 2: Resource Review A review of King County iMap and other resources revealed no sensitive areas located along the downstream drainage path. In addition, no relevant drainage complaints were identified within a quarter mile of the site discharge location. Task 3: Field Inspection The field inspection portion of the Off-Site Analysis was performed by Encompass Engineering & Surveying on Tuesday, February 28th, 2023. The analysis was performed at approximately 12:00 PM under cloudy conditions with a temperature of about 40°. Soil conditions were observed to be moderately wet. Details on the drainage system and photographs are provided in Task 4 below. Task 4: Drainage System Description and Problem Descriptions The site has only one natural discharge location (NDA) in the southwestern corner of the property, which results in one total TDA for the site. Stormwater runoff from the site generally sheet flows in the southwesterly direction towards the southwestern property corner (A). After flowing off the property, the runoff reaches S 288th Street and begins flowing west within the flowline on the northern side of the street. After about 100 FT, the runoff enters the public stormwater system via a type 1 catch basin (B). After about 650 FT, the stormwater system passes by the intersection of 20th Ave S & S 288th Street and continues to head west underneath S 288th Street (C). The stormwater continues being conveyed west under S 288th Street after the ¼ mile downstream limit was reached (D). No drainage related issues were observed downstream of the site, and no relevant drainage complaints were identified on the King County iMap system within a quarter mile of the site discharge location. Please refer to the Downstream Map (Figure 7), Drainage System Table (Table 1), and photographs on the following pages for additional details. American Pride Lending LLC Short Plat Preliminary Technical Information Report 03/17/2023 Page 2 Figure 7: Downstream Map Table 1: Off-Site Analysis Drainage System Symbol (see map) Drainage Component Drainage Component Description Slope % Distance from site discharge (¼ ml = 1,320 ft.) Existing Problems Potential Problems Observations of field inspector, resource reviewer, or resident A SHEET FLOW VEGETATION 2-15% 0’ NO NO NO IMMINENT PROBLEMS B CATCH BASIN TYPE 1 N/A 100’ NO NO NO IMMINENT PROBLEMS C CATCH BASIN TYPE 1 N/A 750’ NO NO NO IMMINENT PROBLEMS D CATCH BASIN TYPE 1 N/A 1,320’ NO NO NO IMMINENT PROBLEMS NORTH American Pride Lending LLC Short Plat Preliminary Technical Information Report 03/17/2023 Page 3 Element A: Runoff sheet flows towards southwestern property corner and onto S 288th Street Element B: Runoff enters stormwater system on S 288th Street and is conveyed west American Pride Lending LLC Short Plat Preliminary Technical Information Report 03/17/2023 Page 4 Element C: Stormwater system passes 20th Ave S & S 288th Street intersection Element D: Storm system continues west under S 288th Street – ¼ mile limit reached American Pride Lending LLC Short Plat Preliminary Technical Information Report 03/17/2023 Page 5 Task 5: Mitigation of Existing or Potential Problems No drainage related issues were observed downstream of the site, and no relevant drainage complaints were identified on the King County iMap system within a quarter mile of the site discharge location. Therefore, mitigation measures are not proposed. American Pride Lending LLC Short Plat Preliminary Technical Information Report 03/17/2023 Page 6 IV. FLOW CONTROL, LOW IMPACT DEVELOPMENT (LID), AND WATER QUALITY FACILITY ANALYSIS AND DESIGN Part A: Existing Site Hydrology The 39,006 SF (0.89 AC) lot is zoned RS7.2. The property is currently undeveloped and can be accessed via South 288th Street to the south. Stormwater from the site generally sheet flows to the southwest across moderate slopes ranging from 2-15% with some localized steep slopes in excess of 15%. Existing vegetation on the site includes small trees, shrubs, and grasses. Please refer to Section III of this TIR for a more detailed description of the downstream flowpath. An Existing Conditions Map is provided as Figure 4 at the end of Section I of this TIR. WWHM 2012 was used to model the existing condition within the 34,420 SF (0.790 AC) project limits using the historic forested condition. The modeled project limits include the clearing limits required to construct the short plat infrastructure, the individual lots, the Open Space/NGRA Tract, and the Landscape Tract. See the summary of existing and developed areas on the following pages, as well as the existing conditions map provided as Figure 4 for more details. Part B: Developed Site Hydrology This project proposes a new development with two (2) single-family lots, an Access/Utility Tract, a 20 FT ROW dedication, a 10 FT Landscape Tract adjacent to the ROW dedication, and a large Open Space/NGRA Tract. Lot 1 is a rectangular shaped lot located in the southwest corner of the site with an area of 7,200 SF (0.165 AC). Lot 2 is a rectangular shaped lot located in the northwest corner of the site with an area of 7,200 SF (0.165 AC). The 20 FT ROW dedication is 5,498 SF (0.126 AC) and stretches along the site’s frontage adjacent to South 288th Street. The 10 FT Landscape Tract is 2,498 SF (0.057 AC) and is located just north of the ROW dedication. Frontage improvements along South 288th Street have been waived by the City via the Street Modification Request that was approved on November 2, 2022 (Appendix E). Both Lots 1 and 2 are accessed from South 288th Street via a proposed 16 FT wide joint-use driveway that runs through a 25 FT wide Access/Utility Tract (1,375 SF). A residential driveway apron will be provided off South 288th Street near the southwest corner of the site. The proposed joint-use driveway and apron include 270 SF of new pollution generating impervious surface (PGIS) in the existing public ROW, 320 SF of new PGIS in the ROW dedication area, and 1,031 SF of new PGIS within the Access/Utility Tract. The total new PGIS associated with the joint-use driveway is 1,621 SF. The maximum future building footprint on Lot 1 was determined to be 1,800 SF with a maximum rooftop area of approximately 2,100 SF. The maximum future building footprint on Lot 2 was determined to be 1,700 SF with a maximum rooftop area of approximately 2,000 SF. Future private driveways for Lots 1 and 2 are estimated to include 400 SF and 1,000 SF of new PGIS, respectively. Reduced impervious surface covenants will be recorded on both Lots 1 and 2 in order to satisfy Flow Control BMP requirements for the future single-family building permits. These covenants will limit impervious surface coverage on Lot 1 to 2,500 SF and Lot 2 to 3,000 SF. The overall project will result in the addition of 4,100 SF of new non-pollution generating impervious surface (future rooftops) and 3,021 SF of new PGIS (joint-use driveway and future private driveways). The total proposed impervious surface associated with the short plat is 7,121 SF. New non-pollution generating pervious surface associated with the short plat and future lots includes 9,566 SF of new lawn. American Pride Lending LLC Short Plat Preliminary Technical Information Report 03/17/2023 Page 7 The 34,420 SF (0.790 AC) project limits have been modeled as shown in Table below. The modeled project limits include the on- and off-site clearing limits required to construct the short plat infrastructure, the individual lots, the Open Space/NGRA Tract, and the Landscape Tract. The Open Space/NGRA Tract and the Landscape Tract have been modeled as forest in the developed condition since it is proposed to reserve all native vegetation within the Open Space/NGRA Tract and replant the Landscape Tract with dense native vegetation as part of the short plat. The portion of the 20’ ROW dedication area where no work is proposed is excluded from the model. Table 2: WWHM Area Breakdown Existing Developed Condition Measured Modeled Measured Modeled C, Forest, Moderate: 30,056 SF (0.690 AC) 30,282 SF (0.695 AC) 16,513 SF (0.379 AC) 16,513 SF (0.379 AC) C, Forest, Steep: 4,138 SF (0.095 AC) 4,138 SF (0.095 AC) 1,220 SF (0.028 AC) 1,220 SF (0.028 AC) C, Lawn, Moderate: 5,994 SF (0.138 AC) 5,994 SF (0.138 AC) C, Lawn, Flat: 3,572 SF (0.082 AC) 3,572 SF (0.082 AC) Roof, Flat: 4,100 SF (0.094 AC) 4,100 SF (0.094 AC) Driveways, Moderate: 2,021 SF (0.046 AC) 2,021 SF (0.046 AC) Driveways, Flat: 1,000 SF (0.023 AC) 1,000 SF (0.023 AC) Sidewalks, Flat: 226 SF (0.005 AC) Total Area: 34,420 SF (0.790 AC) 34,420 SF (0.790 AC) 34,420 SF (0.790 AC) 34,420 SF (0.790 AC) Part C: Performance Standards The project is a New Development located in the Lower Green River Drainage Basin within the Urban Growth Area (UGA). The City of Federal Way Flow Control Applications Map classifies the site as a Conservation (Level 2) Flow Control Area, and the Water Quality Applications Map classifies the site an Enhanced Basic Water Quality Treatment Area. In addition, the construction of the plat infrastructure is subject to the Small Subdivision and Urban Subdivision Project BMP Requirements and the future lots are subject to Individual Small Lot BMP Requirements. Part D: Flow Control System The site meets flow control exemption 2. As shown in Figure 8 on the following page, the proposed development results in a 0.0999 CFS increase in the 100-year flow using 1-hour time steps, which is below the exemption threshold of 0.10 CFS. No flow control facilities are proposed at this time; however, flow control BMPs will be implemented as described in Section II of this TIR. Please refer to Appendix D for a copy of the full WWHM data output. American Pride Lending LLC Short Plat Preliminary Technical Information Report 03/17/2023 Page 8 Figure 8: WWHM Flow Frequency Data Output Part E: Water Quality System The project site is located within the “Enhanced Basic Water Quality Treatment Menu Required” area of the City of Federal Way Water Quality Applications Map. Per Section 1.2.8 of the City of Federal Way Addendum to the KCSWDM, New Developments are to refer directly to the 2021 KCSWDM for both impervious and pervious surface requirements that trigger Core Requirement #8 for water quality. Per Section 1.2.8 of the 2021 KCSWDM there are four (4) possible exemptions from Core Requirement #8. The first of which is the Surface Area Exemption that states a proposed project is exempt if it meets all of the following criteria: • Less than 5,000 square feet of new plus replaced Pollution Generating Impervious Surface (PGIS) will be created, AND • Less than ¾ acre of new Pollution Generating Pervious Surface (PGPS) will be added. As described in detail in Section I of this TIR, the overall project will result in the addition of only 3,021 SF of new PGIS (joint-use driveway and future private driveways), which is less than the 5,000 SF exemption threshold above. No new PGPS is proposed. Therefore, the Surface Area Exemption in Section 1.2.8 of the 2021 KCSWDM is achieved, and water quality treatment is not required for this project. V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN Conveyance analysis will be provided with final engineering if requested by the City. VI. SPECIAL REPORTS AND STUDIES • Geotechnical Evaluation by Earth Solutions NW, LLC dated June 3, 2022 (Appendix A). • Limited Please II Environmental Site Assessment by Earth Solutions NW, LLC dated May 16, 2022 (Appendix B). • No Action for Tacoma Smelter Plume Letter by Washington State Department of Ecology dates June 22, 2022 (Appendix C). • Approved Street Modification Request dated November 2, 2022 (Appendix E). VII. OTHER PERMITS • Building Permits • Clearing & Grading Permit • ROW Permit • Lakehaven Water & Sewer Service Connection Permits American Pride Lending LLC Short Plat Preliminary Technical Information Report 03/17/2023 Page 9 VIII. CSWPPP ANALYSIS AND DESIGN A CSWPPP will be provided with final engineering. IX. BOND QUANTITIES and DECLARATION of COVENANT Bond Quantities and a Declaration of Covenant to be provided with Final Engineering if requested by the City. X. OPERATION AND MAINTENANCE MANUAL An Operation and Maintenance Manual will be provided with Final Engineering. Appendix A Geotechnical Evaluation by Earth Solutions NW, dated June 3, 2022 15365 N.E. 90th Street, Suite 100 • Redmond, WA 98052 • (425) 449-4704 • FAX (425) 449-4711 Earth Solutions NW LLC Geotechnical Engineering, Construction Observation/Testing and Environmental Services June 3, 2022 ES-8485 American Pride Lending, LLC P.O. Box 1226 Kent, Washington 98035 Attention: Mr. Sikander Sekhon Subject: Geotechnical Evaluation Proposed Short Plat 2240 South 288th Street Federal Way, Washington Reference: H.H. Waldron Geologic Map of the Poverty Bay Quadrangle, 1961 United States Department of Agriculture (USDA) Natural Resources Conservation Service Online Web Soil Survey (WSS) Resource Federal Way Revised Code (FWRC) Chapter 19.145 – Environmentally Critical Areas King County Flood Control District Liquefaction Susceptibility (Map 11-5), dated May 2010 King County Department of Natural Resources and Parks 2021 Surface Water Design Manual, dated July 23, 2021 Dear Mr. Sekhon: As requested, Earth Solutions NW, LLC (ESNW) has prepared this geotechnical evaluation for the subject site. We performed our work in general accordance with the scope of services outlined in our proposal dated March 10, 2022, which was authorized by you on March 29, 2022. A summary of the field investigation and pertinent geotechnical design recommendations and conclusions are provided in this letter. American Pride Lending, LLC ES-8485 June 3, 2022 Page 2 Earth Solutions NW, LLC Project & Site Description The subject site is located directly northwest of the intersection between South 288th Street and 23rd Place South in Federal Way, Washington. The approximate site location is illustrated on the attached Vicinity Map (Plate 1). The site is comprised of one tax parcel (King County Parcel No. 332204-9023), totaling about 0.9 acres. The subject site is currently unoccupied. Based on review of historical aerial photographs available on the King County iMap, the site was previously developed with a single-family residence which appears to have been removed sometime between 2002 and 2005; subsequent to removal of the structure, the site appears to have been cleared and somewhat regraded sometime between 2007 and 2009. Site topography gently descends to the southwest. Total elevation change across the subject site is approximately 15 feet. Vegetation consists of field grass and a few mature trees. Based on conceptual plans communicated to us, we four new single-family homes will be constructed on the subject site. Grading plans were not available at the time of this evaluation; however, based on the existing site topography, we anticipate grading will consist of cuts and fills of less than about 5 to 10 feet. Subsurface An ESNW representative observed, logged, and sampled three test pits on April 14, 2022. The test pits were excavated within accessible areas of the site using a mini trackhoe and operator retained by ESNW. The test pits were completed to assess soil conditions, classify site soils, and characterize groundwater conditions within the proposed development area. The approximate locations of the test pits are depicted on the attached Plate 2 (Test Pit Location Plan). Please refer to the attached test pit logs for a more detailed description of subsurface conditions. Representative soil samples collected at the test pit locations were analyzed in general accordance with both Unified Soil Classification System (USCS) and USDA methods and procedures. Topsoil Topsoil, was generally encountered within the upper 6 to 12 inches below the existing ground surface (bgs). The topsoil was characterized by its dark brown color, the presence of fine organic material, and root intrusions extending up to three feet bgs. Fill Fill was encountered at all test pit locations during our subsurface exploration extending to a depth of approximately two feet bgs. The fill is characterized as silty sand with gravel in a loose and moist condition. Based on the existing site conditions and review of historical aerial photographs, we anticipate that fill will be encountered across the majority of the buildable site area. American Pride Lending, LLC ES-8485 June 3, 2022 Page 3 Earth Solutions NW, LLC Native Soil Underlying topsoil and fill, native soil was encountered as medium dense to very dense silty gravel with varying amounts of sand (USCS: GW-GM and GM). Native soil relative density generally increased with depth and becomes weakly cemented beginning at depths of roughly three to four feet bgs. Native soil was generally encountered in a moist to wet condition. Geologic Setting The referenced geologic map identifies ground moraine deposits (Qgt) across the subject property and surrounding area. As reported on the geologic map resource, ground moraine deposits are comprised of compact, unoxidized glacial till. The material is typically very dense and weakly cemented resulting from glacial overburden. Glacial till is commonly termed “hardpan” in western Washington. Distinct features of the material are compactness, ability to maintain near-vertical slopes, very low permeability, and a heterogenous internal structure resembling a low-strength concrete. Based on our field observations, native soil likely to be exposed during grading activities will be consistent with glacial till deposits. The referenced WSS resource identifies arents of Alderwood material (Map Unit: AmC) as the primary soil unit underlying the subject site. Soils of the arents of Alderwood series are associated with glacial till ridge and hill landforms, which were modified by human grading activity. The native soil observed is generally consistent with Alderwood series soil. Groundwater Groundwater was encountered at test pit locations TP-1 and TP-2 during the April 2022 subsurface exploration. The light groundwater seepage was observed at depths of about four and five bgs. Additionally, light iron oxide staining was observed at all test pit locations at a depth of about three feet bgs, which is indicative of seasonal groundwater seepage. Groundwater seepage rates and elevations fluctuate depending on many factors, including precipitation duration and intensity, the time of year, and soil conditions. In general, groundwater flow rates are higher during the winter, spring, and early summer months. Critical Areas Review ESNW reviewed FWRC Chapter 19.145 to determine if geologically relevant critical areas recognized by Federal Way (including erosion, landslide, and seismic hazard areas) exist on or near the subject site. Our review indicates that these critical areas have not been mapped on site or in proximity to the site. Based on our field observations, it is our opinion the site is correctly mapped outside of the geologically relevant critical areas listed herein. Discussion & Recommendations The following sections provide discussion and recommendations to aid with the design and construction of the proposed single-family residences and related improvements. American Pride Lending, LLC ES-8485 June 3, 2022 Page 4 Earth Solutions NW, LLC In-Situ and Imported Soil Most of the in-situ soils encountered at the subject site have a moderate to high sensitivity to moisture and were generally in a moist to wet condition at the time of exploration. Soils anticipated to be exposed on site will degrade if exposed to wet weather and construction traffic. Compaction of the soils to the levels necessary for use as structural fill may be difficult or impossible during wet weather conditions. Soils encountered during site excavations that are excessively over the optimum moisture content will likely require aeration or treatment prior to placement and compaction. Conversely, soils that are substantially below the optimum moisture content will require moisture conditioning through the addition of water prior to use as structural fill. An ESNW representative should determine the suitability of in-situ soils for use as structural fill at the time of construction. Imported soil intended for use as structural fill should consist of a well-graded, granular soil with a moisture content that is at (or slightly above) the optimum level. During wet weather conditions, imported soil intended for use as structural fill should consist of a well-graded, granular soil with a fines content of 5 percent or less (where the fines content is defined as the percent passing the Number 200 sieve, based on the minus three-quarter-inch fraction). Structural Fill Structural fill is defined as compacted soil in foundation, slab-on-grade, driveway, retaining wall, and utility trench areas. Soils placed in structural areas should be placed in maximum 12-inch loose lifts and compacted to a relative compaction of 95 percent, based on the laboratory maximum dry density as determined by the Modified Proctor Method (ASTM D1557). Fill should be placed on a firm and level surface. ESNW should be consulted during early grading activities to provide additional recommendations regarding structural fill placement, where necessary. Excavations and Slopes Based on the soil conditions observed at the test pit locations, the following allowable temporary slope inclinations, as a function of horizontal to vertical (H:V) inclination, are recommended. The applicable Federal Occupation Safety and Health Administration (OSHA) and Washington Industrial Safety and Health Act (WISHA) soil classifications are also provided: Loose soil 1.5H:1V (Type C) Areas exposing groundwater seepage 1.5H:1V (Type C)  Medium dense soil 1H:1V (Type B) Dense to very dense “hardpan” native soil 0.75H:1V (Type A) American Pride Lending, LLC ES-8485 June 3, 2022 Page 5 Earth Solutions NW, LLC ESNW can evaluate the feasibility of utilizing steeper temporary slopes at the time of construction. In any case, an ESNW representative should observe temporary slopes to confirm inclinations are suitable for the exposed soil conditions and to provide additional excavation and slope stability recommendations, as necessary. If the recommended temporary slope inclinations cannot be achieved, temporary shoring may be necessary to support excavations. Permanent slopes should be graded to 2H:1V (or flatter) and planted with vegetation to enhance stability and minimize erosion potential. Permanent slopes should be observed by ESNW prior to vegetation and landscaping. Foundations In our opinion, the proposed single-family residential structures can be constructed on a conventional continuous and spread footing foundation bearing on competent native soil, recompacted native soil, or new structural fill placed directly on competent native soil. Competent native soil suitable for support of foundations will likely be encountered beginning at depths of about two to three feet bgs. Where loose or unsuitable soil conditions are exposed at foundation subgrade elevations, compaction of the soil to the specifications of structural fill or overexcavation and replacement with suitable structural fill will be necessary. Provided the foundations will be supported as described above, the following parameters may be used for design: Allowable soil bearing capacity 2,500 psf  Passive earth pressure 300 pcf  Coefficient of friction 0.40 The passive earth pressure value provided above assumes the foundations will be backfilled with structural fill. A factor-of-safety of 1.5 has been applied to the passive earth pressure and coefficient of friction values provided in this section. For short-term wind and seismic loading, a one-third increase in the allowable soil bearing capacity may be assumed. With structural loading as expected, total settlement of about one inch and differential settlement of approximately one- half inch is anticipated. Most of the anticipated settlement should occur during construction, as dead loads are applied. Slab-on-Grade Floors Slab-on-grade floors should be supported on a suitable capillary break material underlain by a compacted and competent subgrade. Structural fill in slab-on-grade areas should be compacted to a minimum relative compaction of 95 percent. Unstable or yielding areas of the subgrade should be recompacted, or overexcavated and replaced with suitable structural fill, prior to slab construction. American Pride Lending, LLC ES-8485 June 3, 2022 Page 6 Earth Solutions NW, LLC Slab-on-grade areas should be provided with a minimum four-inch-thick capillary break. Capillary break soils should consist of a granular, free-draining coarse sand and gravel soil that contains less than 5 percent fines (percent passing the Number 200 sieve, based on the minus three- quarter-inch fraction). To facilitate grading of the slab subgrade, the maximum aggregate size of the capillary break material should generally be one-and-one-quarter inch. In areas where slab moisture is undesirable, installation of a vapor barrier placed below the slab should be considered. If a vapor barrier will be utilized, it should consist of a material specifically designed for that use and should be installed in accordance with the specifications of the manufacturer. Seismic Design The 2018 International Building Code (2018 IBC) recognizes the most recent edition of the Minimum Design Loads for Buildings and Other Structures manual (ASCE 7-16) for seismic design, specifically with respect to earthquake loads. Based on the soil conditions encountered at the test pit locations, the parameters and values provided below are recommended for seismic design per the 2018 IBC. Parameter Value Site Class C* Mapped short period spectral response acceleration, SS (g) 1.336 Mapped 1-second period spectral response acceleration, S1 (g) 0.458 Short period site coefficient, Fa 1.200 Long period site coefficient, Fv 1.500 Adjusted short period spectral response acceleration, SMS (g) 1.603 Adjusted 1-second period spectral response acceleration, SM1 (g) 0.687 Design short period spectral response acceleration, SDS (g) 1.069 Design 1-second period spectral response acceleration, SD1 (g) 0.458 *Assumes very dense soil conditions, encountered to a maximum depth of 10 feet bgs during the March 2022 field exploration, remain very dense to at least 100 feet bgs. Based on our experience with the project geologic setting (glacial till) across the Puget Sound region, soil conditions are likely consistent with this assumption. Liquefaction is a phenomenon where saturated and loose cohesionless soil suddenly loses internal strength and behaves as a fluid. This behavior is in response to increased pore water pressures resulting from an earthquake or another intense ground shaking. In our opinion, site susceptibility to liquefaction can be considered negligible. The composition and relatively dense characteristics of the native soil were the primary bases for this opinion. American Pride Lending, LLC ES-8485 June 3, 2022 Page 7 Earth Solutions NW, LLC Retaining Walls Retaining walls must be designed to resist earth pressures and applicable surcharge loads. The following parameters may be used for design: Active earth pressure (unrestrained condition) 35 pcf (equivalent fluid) At-rest earth pressure (restrained condition) 55 pcf Traffic surcharge* (passenger vehicles)70 psf (rectangular distribution) Passive earth pressure 300 pcf (equivalent fluid)  Coefficient of friction 0.40  Seismic surcharge 8H psf** * Where applicable. ** Where H equals the retained height (in feet). Retaining walls should be backfilled with free-draining material that extends along the height of the wall and a distance of at least 18 inches behind the wall; a typical retaining wall drainage detail (Plate 3) is attached to this letter. The upper 12 inches of the wall backfill may consist of a less permeable soil, if desired. A sheet drain may be considered in lieu of free-draining backfill. A perforated drainpipe should be placed along the base of the wall and connected to an approved discharge location. If drainage is not provided, hydrostatic pressures should be included in the wall design. Drainage Groundwater was encountered at test pit locations TP-1 and TP-2 at depths of about four feet and five feet, respectively. Based on the encountered soil types, we anticipate groundwater seepage to be common during subsurface excavations on the subject property, particularly during utility excavations. Temporary measures to control groundwater seepage and surface water runoff during construction will likely involve passive elements such as interceptor trenches and sumps, as necessary. Surface grades must be designed to direct water away from structures and slopes. The grade adjacent to the buildings should be sloped away from the buildings at a gradient of at least 2 percent for a minimum horizontal distance of either 10 feet or as setbacks allow. In our opinion, perimeter footing drains should be installed at or below the invert of the building footings. A typical footing drain detail is provided on Plate 4 of this report. If footing drains are not installed, we recommend backfilling footings with a relatively impermeable soil. American Pride Lending, LLC ES-8485 June 3, 2022 Page 8 Earth Solutions NW, LLC Preliminary Infiltration Evaluation We understand on-site stormwater infiltration is being considered for the proposed project. Based on existing grades, we would anticipate project grading to include cuts of about 5 to 10 feet, which would expose weakly cemented, low permeability soil. Based on our subsurface observations of glacial till deposits and indications of seasonal groundwater seepage (iron oxide staining) as shallow as about three feet bgs, we do not recommend incorporating infiltration into the overall stormwater design. However, ESNW can further evaluate the potential for limited infiltration BMPs based on proposed site design, if requested. Limitations This letter has been prepared for the exclusive use of American Pride Lending, LLC and their representatives. No warranty, express or implied, is made. The recommendations and conclusions provided in this letter are professional opinions consistent with the level of care and skill that is typical of other members in the profession currently practicing under similar conditions in this area. If the design assumptions outlined in this letter either change or are incorrect, or if construction conditions differ from those encountered during our fieldwork, ESNW should be contacted to review the recommendations and conclusions provided in this letter. Additional Services ESNW should have an opportunity to review the final design with respect to the geotechnical recommendations provided in this letter. ESNW should also be retained to provide testing and consultation services during construction. American Pride Lending, LLC ES-8485 June 3, 2022 Page 9 Earth Solutions NW, LLC We trust this letter meets your current needs. Should you have any questions regarding the content herein, or require additional information, please call. Sincerely, EARTH SOLUTIONS NW, LLC Samuel E. Suruda, L.G. Henry T. Wright, P.E. Senior Staff Geologist Associate Principal Engineer Attachments: Plate 1 – Vicinity Map Plate 2 – Test Pit Location Plan Plate 3 – Retaining Wall Drainage Detail Plate 4 – Footing Drain Detail Test Pit Logs Grain Size Distribution cc: Encompass Engineering & Surveying Attention: Ms. Heather Tatro (Email only) 06/03/2022 Drwn.CAM Checked SES Date May 2022 Date 05/31/2022 Proj.No.8485 Plate 1 Geotechnical Engineering,Construction Observation/Testing and Environmental Services Earth Solutions NWLLCEarthSolutionsNWLLC EarthSolutions NW LLC Vicinity Map S.288th Street Short Plat Federal Way,Washington Reference: King County,Washington OpenStreetMap.org NORTH NOTE:This plate may contain areas of color.ESNW cannot be responsible for any subsequent misinterpretation of the information resulting from black &white reproductions of this plate. Federal Way SITE Drwn.CAM Checked SES Date May 2022 Date 05/31/2022 Proj.No.8485 Plate 2 Geotechnical Engineering,Construction Observation/Testing and Environmental Services Earth Solutions NWLLCEarthSolutionsNWLLC EarthSolutions NW LLC TP-1TP-2 TP-3 s.288th street Test Pit Location Plan S.288th Street Short Plat Federal Way,Washington NOTE:This plate may contain areas of color.ESNW cannot be responsible for any subsequent misinterpretation of the information resulting from black &white reproductions of this plate. NOTE:The graphics shown on this plate are not intended for design purposes or precise scale measurements,but only to illustrate the approximate test locations relative to the approximate locations of existing and /or proposed site features.The information illustrated is largely based on data provided by the client at the time of our study.ESNW cannot be responsible for subsequent design changes or interpretation of the data by others. LEGEND Approximate Location of ESNW Test Pit,Proj.No. ES-8485,April 2022 Subject Site Existing Building TP-1 NOT -TO -SCALE NORTH Geotechnical Engineering,Construction Observation/Testing and Environmental Services Drwn.CAM Checked SES Date May 2022 Date 05/31/2022 Proj.No.8485 Plate 3 Earth Solutions NWLLCEarthSolutionsNWLLC EarthSolutions NW LLC NOTES: Free-draining Backfill should consist of soil having less than 5 percent fines. Percent passing No.4 sieve should be 25 to 75 percent. Sheet Drain may be feasible in lieu of Free-draining Backfill,per ESNW recommendations. Drain Pipe should consist of perforated, rigid PVC Pipe surrounded with 1-inch Drain Rock. LEGEND: Free-draining Structural Backfill 1-inch Drain Rock 18"Min. Structural Fill Perforated Rigid Drain Pipe (Surround in Drain Rock) SCHEMATIC ONLY -NOT TO SCALE NOT A CONSTRUCTION DRAW ING Retaining Wall Drainage Detail S.288th Street Short Plat Federal Way,Washington Geotechnical Engineering,Construction Observation/Testing and Environmental Services Drwn.CAM Checked SES Date May 2022 Date 05/31/2022 Proj.No.8485 Plate 4 Earth Solutions NWLLCEarthSolutionsNWLLC EarthSolutions NW LLC Slope Perforated Rigid Drain Pipe (Surround in Drain Rock) 18"Min. NOTES: Do NOT tie roof downspouts to Footing Drain. Surface Seal to consist of 12"of less permeable,suitable soil.Slope away from building. LEGEND: Surface Seal:native soil or other low-permeability material. 1-inch Drain Rock SCHEMATIC ONLY -NOT TO SCALE NOT A CONSTRUCTION DRAW ING Footing Drain Detail S.288th Street Short Plat Federal Way,Washington GRAVEL AND GRAVELLY SOILS CLAYEY GRAVELS, GRAVEL - SAND - CLAY MIXTURES WELL-GRADED SANDS, GRAVELLY SANDS, LITTLE OR NO FINES POORLY-GRADED SANDS, GRAVELLY SAND, LITTLE OR NO FINES SILTY SANDS, SAND - SILT MIXTURES CLAYEY SANDS, SAND - CLAY MIXTURES INORGANIC SILTS AND VERY FINE SANDS, ROCK FLOUR, SILTY OR CLAYEY FINE SANDS OR CLAYEY SILTS WITH SLIGHT PLASTICITY INORGANIC CLAYS OF LOW TO MEDIUM PLASTICITY, GRAVELLY CLAYS, SANDY CLAYS, SILTY CLAYS, LEAN CLAYS ORGANIC SILTS AND ORGANIC SILTY CLAYS OF LOW PLASTICITY INORGANIC SILTS, MICACEOUS OR DIATOMACEOUS FINE SAND OR SILTY SOILS INORGANIC CLAYS OF HIGH PLASTICITY SILTS AND CLAYS MORE THAN 50% OF MATERIAL IS LARGER THAN NO. 200 SIEVE SIZE MORE THAN 50% OF MATERIAL IS SMALLER THAN NO. 200 SIEVE SIZE MORE THAN 50% OF COARSE FRACTION PASSING ON NO. 4 SIEVE MORE THAN 50% OF COARSE FRACTION RETAINED ON NO. 4 SIEVE SOIL CLASSIFICATION CHART (APPRECIABLE AMOUNT OF FINES) (APPRECIABLE AMOUNT OF FINES) (LITTLE OR NO FINES) FINE GRAINED SOILS SAND AND SANDY SOILS SILTS AND CLAYS ORGANIC CLAYS OF MEDIUM TO HIGH PLASTICITY, ORGANIC SILTS PEAT, HUMUS, SWAMP SOILS WITH HIGH ORGANIC CONTENTS LETTERGRAPH SYMBOLSMAJOR DIVISIONS COARSE GRAINED SOILS TYPICAL DESCRIPTIONS WELL-GRADED GRAVELS, GRAVEL - SAND MIXTURES, LITTLE OR NO FINES POORLY-GRADED GRAVELS, GRAVEL - SAND MIXTURES, LITTLE OR NO FINES SILTY GRAVELS, GRAVEL - SAND - SILT MIXTURES CLEAN GRAVELS GRAVELS WITH FINES CLEAN SANDS (LITTLE OR NO FINES) SANDS WITH FINES LIQUID LIMIT LESS THAN 50 LIQUID LIMIT GREATER THAN 50 HIGHLY ORGANIC SOILS DUAL SYMBOLS are used to indicate borderline soil classifications. The discussion in the text of this report is necessary for a proper understanding of the nature of the material presented in the attached logs. GW GP GM GC SW SP SM SC ML CL OL MH CH OH PT Earth Solutions NW LLC MC = 20.2% MC = 9.4% Fines = 11.7% MC = 6.2% MC = 6.0% TPSL SM GW- GM Dark brown TOPSOIL, trace roots to 3' (Fill) Brown silty SAND with gravel, loose to medium dense, moist (Fill) Brown well-graded GRAVEL with silt and sand, medium dense, wet -becomes gray, dense, moist, weakly cemented [USDA Classification: extremely gravelly coarse sandy LOAM] -light iron oxide staining -light groundwater seepage -becomes dense to very dense Test pit terminated at 9.5 feet below existing grade. Groundwater seepage encountered at 4.0 feet during excavation. No caving observed. 1.0 2.0 9.5SAMPLE TYPENUMBERDEPTH(ft)0.0 2.5 5.0 7.5 PAGE 1 OF 1 TEST PIT NUMBER TP-1 NOTES Depth of Topsoil & Sod 8-12": brambles LOGGED BY KTK EXCAVATION METHOD EXCAVATION CONTRACTOR NW Excavating CHECKED BY HTW DATE STARTED 4/14/22 COMPLETED 4/14/22 GROUND WATER LEVEL: AT TIME OF EXCAVATION GROUND ELEVATION LATITUDE 47.34381 LONGITUDE -122.30325 PROJECT NUMBER ES-8485 PROJECT NAME S. 288th Street Short Plat GENERAL BH / TP / WELL - 8485.GPJ - GRAPHICS TEMPLATE WITH LAT AND LONG.GDT - 5/31/22Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 TESTS U.S.C.S.MATERIAL DESCRIPTION GRAPHICLOG MC = 13.0% MC = 19.7% MC = 9.3% MC = 8.5% Fines = 35.5% TPSL SM GM Dark brown TOPSOIL (Fill) Brown silty SAND with gravel, loose, moist (Fill) Brown silty GRAVEL with sand, medium dense, wet -becomes moist -becomes gray, dense, weakly cemented, light iron oxide staining -becomes dense to very dense -light groundwater seepage [USDA Classification: gravelly LOAM] Test pit terminated at 10.0 feet below existing grade. Groundwater seepage encountered at 5.0 feet during excavation. No caving observed. 1.0 2.0 10.0SAMPLE TYPENUMBERDEPTH(ft)0.0 2.5 5.0 7.5 10.0 PAGE 1 OF 1 TEST PIT NUMBER TP-2 NOTES Depth of Topsoil & Sod 8-12": grass LOGGED BY KTK EXCAVATION METHOD EXCAVATION CONTRACTOR NW Excavating CHECKED BY HTW DATE STARTED 4/14/22 COMPLETED 4/14/22 GROUND WATER LEVEL: AT TIME OF EXCAVATION GROUND ELEVATION LATITUDE 47.34381 LONGITUDE -122.30368 PROJECT NUMBER ES-8485 PROJECT NAME S. 288th Street Short Plat GENERAL BH / TP / WELL - 8485.GPJ - GRAPHICS TEMPLATE WITH LAT AND LONG.GDT - 5/31/22Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 TESTS U.S.C.S.MATERIAL DESCRIPTION GRAPHICLOG MC = 12.1% MC = 10.8% Fines = 22.9% MC = 9.2% MC = 8.2% TPSL SM GM Dark brown TOPSOIL (Fill) Brown silty SAND with gravel, loose, moist (Fill) Brown silty GRAVEL with sand, medium dense, moist -light iron oxide staining [USDA Classification: very gravelly sandy LOAM] -becomes gray, dense, weakly cemented -becomes dense to very dense Test pit terminated at 10.0 feet below existing grade. No groundwater encountered during excavation. No caving observed. 0.5 2.0 10.0SAMPLE TYPENUMBERDEPTH(ft)0.0 2.5 5.0 7.5 10.0 PAGE 1 OF 1 TEST PIT NUMBER TP-3 NOTES Depth of Topsoil & Sod 6": grass LOGGED BY KTK EXCAVATION METHOD EXCAVATION CONTRACTOR NW Excavating CHECKED BY HTW DATE STARTED 4/14/22 COMPLETED 4/14/22 GROUND WATER LEVEL: AT TIME OF EXCAVATION GROUND ELEVATION LATITUDE 47.34368 LONGITUDE -122.30407 PROJECT NUMBER ES-8485 PROJECT NAME S. 288th Street Short Plat GENERAL BH / TP / WELL - 8485.GPJ - GRAPHICS TEMPLATE WITH LAT AND LONG.GDT - 5/31/22Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 TESTS U.S.C.S.MATERIAL DESCRIPTION GRAPHICLOG 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 0.0010.010.1110100 3 D100 140 Specimen Identification 1 fine 6 HYDROMETER 304 11.7 35.5 22.9 101/2 COBBLES Specimen Identification 4 coarse 20 401.5 8 14 USDA: Brown Extremely Gravelly Coarse Sandy Loam. USCS: GW-GM with Sand. USDA: Gray Gravelly Loam. USCS: SM with Gravel. USDA: Brown Very Gravelly Sandy Loam. USCS: GM with Sand. 6 60 PERCENT FINER BY WEIGHTD10 1.032 0.171 17.862 0.551 3.915 GRAIN SIZE DISTRIBUTION 100 335.22 LL TP-01 TP-02 TP-03 3/4 U.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS GRAVEL SAND 75 37.5 37.5 %Silt 1.12 TP-01 TP-02 TP-03 2 2003 Cc CuClassification %Clay 16 PID60 D30 coarse SILT OR CLAYfinemedium GRAIN SIZE IN MILLIMETERS 3/8 50 3.0ft. 10.0ft. 3.5ft. 3.00ft. 10.00ft. 3.50ft. PL PROJECT NUMBER ES-8485 PROJECT NAME S. 288th Street Short Plat GRAIN SIZE USDA ES-8485 S. 288TH STREET SHORT PLAT.GPJ GINT US LAB.GDT 5/12/22Earth Solutions NW, LLC 15365 N.E. 90th Street, Suite 100 Redmond, Washington 98052 Telephone: 425-449-4704 Fax: 425-449-4711 Appendix B Limited Please II Environmental Site Assessment by Earth Solutions NW, LLC dated May 16, 2022 15365 N.E. 90th Street, Suite 100 • Redmond, WA 98052 • (425) 449-4704 • FAX (425) 449-4711 Earth Solutions NW LLC Geotechnical Engineering, Construction Observation/Testing and Environmental Services May 16, 2022 ES-8485.01 American Pride Lending, LLC P.O. Box 1226 Kent, Washington 98035 Attention: Mr. Sikander Sekhon Subject: Limited Phase II Environmental Site Assessment Tacoma Smelter Plume South 288th Street Short Plat 2240 South 288th Street Federal Way, Washington Reference: Washington State Department of Ecology Tacoma Smelter Plume Model Remedies Guidance, dated July 2019 Dear Mr. Sekhon: This letter presents the results of the Limited Phase II Environmental Site Assessment (ESA) performed by Earth Solutions NW, LLC (ESNW) at the above-referenced South 288th Street Short Plat property (subject site) at the request of American Pride Lending, LLC (Client). The Limited Phase II ESA soil sampling activities were performed at the subject site to assess potential shallow soil contamination associated with airborne arsenic and lead fallout from the historical Asarco Smelter, formerly located in Tacoma, Washington (area referred to as the Tacoma Smelter Plume). It should be noted that Tacoma Smelter Plume (TSP) characterization soil sampling completed during this investigation was completed in accordance with the referenced Washington State Department of Ecology (Ecology) TSP Model Remedies Guidance document for sampling and cleanup of arsenic and lead contaminated soils (dated July 2019). Based on the analytical laboratory results of this Limited Phase II ESA, no concentrations of lead in site soil exceed the Model Toxics Control Act (MTCA) Method A lead soil cleanup level for unrestricted land-use (CUL) of 250 milligrams per kilogram (mg/kg). Additionally, average concentrations of arsenic in site soil are below the MTCA Method A arsenic soil CUL of 20 mg/kg, with no single soil sample containing concentrations of arsenic at or greater than double the MTCA Method A arsenic soil CUL (40 mg/kg). American Pride Lending, LLC ES-8485.01 May 16, 2022 Page 2 Earth Solutions NW, LLC Therefore, according to Ecology’s TSP Model Remedies Guidance (July 2019), shallow soil at the subject site does not require remediation in connection with arsenic or lead impacts. Based on the findings of this Limited Phase II ESA, no further environmental investigation in connection with the TSP is considered warranted at this time. The body of this letter should be referenced for further details regarding the field activities and findings of this Limited Phase II ESA. Site Description The subject site is located at 2240 South 288th Street, in Federal Way, Washington (see Plate 1 – Vicinity Map). The site consists of one tax parcel (King County Parcel No. 332204-9023), comprising a total of approximately 0.9 acres of land area. The site is currently undeveloped and lightly to moderately overgrown with grass, brambles, and scattered trees. The subject site was determined to be located within an area designated by Ecology to have average concentrations of arsenic in soil ranging from 20 mg/kg to 40 mg/kg, exceeding the MTCA Method A arsenic CUL for soil (20 mg/kg). Decision Units A “Decision Unit” is an “Area of a property expected to have a different pattern of soil contamination than other areas. Some properties will only have one decision unit. Factors include current and past land uses and development history…[and]…Future use can also define decision units” (page 11 of Ecology’s TSP Model Remedies Guidance document). Based on the understanding that the subject site will be redeveloped for residential land-use, the entire subject site was treated as one Decision Unit for the purposes of this TSP characterization shallow soil sampling assessment. See Plate 2 to reference site dimensions and the existing site conditions. Based on Table 1 (page 13) and Table 1a (page 16) of the referenced TSP Model Remedies Guidance, ESNW calculated the minimum number of soil samples that would need to be collected in accordance with the TSP Model Remedies Guidance. See attached “Form 1 – Characterization Sampling” for reference, with calculations on page three of the form. At a minimum, the following number of soil samples needed to be collected across the subject site: 16 soil samples at a depth of zero to six inches into native soil, four soil samples at a depth of 6 to 12 inches into native soil, and four forest duff composite samples See below for discussion of on-site soil sampling activities. American Pride Lending, LLC ES-8485.01 May 16, 2022 Page 3 Earth Solutions NW, LLC Field Activities Field activities involved with completing this Limited Phase II ESA were performed on April 14, 2022. ESNW used site plans to identify evenly spaced and accurately plotted sampling locations in an approximate grid pattern throughout the property. As discussed in the previous section of this letter, 16 discrete soil samples were collected at a depth of zero to six inches bgs. Four soil samples were collected from depths of 6 to 12 inches bgs. Additionally, four forest duff composite samples (each consisting of six evenly spaced forest duff subsamples) were also collected across the subject site. A handheld post-hole digger was used to manually collect each soil and/or forest duff composite sample. See Plate 3 to review sampling locations. Soil conditions were observed to be dry during soil sampling. No wetland areas, standing bodies of water, or steep slopes were observed by ESNW during Limited Phase II ESA soil sampling activities. Soil Sampling Methods Each soil sample was carefully transferred from the post-hole digger into a stainless-steel bowl before being transferred to a pre-cleaned 8-oz glass sampling jar and sealed with a Teflon-lined plastic lid. All tools and equipment used during soil sampling activities were cleaned in separate wash and rinse buckets prior to and between the collection of each soil sample. Additionally, nitrile gloves were worn during sampling activities and replaced with a clean pair between collection of each soil sample. The jars containing the soil samples were labeled and stored on ice in a 5°C cooler, and delivered to On-Site Environmental Laboratories, Inc. (a Washington State-certified laboratory), located in Redmond, Washington, to be analyzed for the following constituents:  Total Arsenic by Environmental Protection Agency (EPA) Analytical Method 6020B.  Total Lead by EPA Analytical Method 6020B. Applicable Regulatory Standards – Soil The rules that guide the cleanup process at sites within Washington State are incorporated into MTCA, as administered by Ecology and defined in WAC 173-340. For this letter, average values for total arsenic and lead concentrations (reported in the On-Site Environmental Laboratories, Inc. analytical reports) were compared to MTCA Method A CULs for soil. The Method A CULs are conservative and are for sites with relatively few hazardous substances, which may not be appropriate for all sites. The regulations state that Method A should not be automatically used to define cleanup levels that must be met for financial, real estate, insurance coverage, or similar purposes. Additionally, test results above Method A cleanup levels do not necessarily mandate a cleanup action for a site. The referenced TSP Model Remedies Guidance document uses MTCA Method A CULs. American Pride Lending, LLC ES-8485.01 May 16, 2022 Page 4 Earth Solutions NW, LLC Copies of the laboratory analytical reports are attached to this letter. Applicable MTCA Method A CULs used during this Limited Phase II ESA include the following:  The MTCA Method A arsenic CUL for soil is 20 mg/kg.  The MTCA Method A lead CUL for soil is 250 mg/kg. It should be noted that, according to Ecology’s 2019 TSP Model Remedies Guidance, “elevated concentrations” of arsenic and lead are defined as follows: average concentrations of total arsenic in soil exceeding Ecology’s MTCA Method A arsenic CUL, 20 mg/kg; average concentrations of total lead in soil exceeding the lead MTCA Method A CUL, 250 mg/kg; or any concentrations of arsenic or lead exceeding double the above-identified MTCA Method A CULs. Analytical Results Arsenic Analytical results indicate that the average concentrations of arsenic in site soil are as follows:  Depth of zero to six inches bgs: 12.1 mg/kg (below the MTCA Method A arsenic CUL of 20 mg/kg); and,  Depth of 6 to 12 inches bgs: 11 mg/kg (below the MTCA Method A arsenic CUL). No single soil or composite duff sample contained concentrations at or exceeding double the MTCA Method A arsenic CUL. In conclusion, no elevated concentrations of arsenic were identified in site soil or forest duff. Lead Analytical results indicate that the average concentrations of lead in site soil are as follows:  Depth of zero to six inches bgs: 17 mg/kg (below the MTCA Method A lead CUL of 250 mg/kg); and,  Depth of 6 to 12 inches bgs: 5.7 mg/kg (below the MTCA Method A lead CUL); No single soil or composite duff sample contained concentrations at or exceeding double the MTCA Method A lead CUL. In conclusion, no elevated concentrations of lead were identified in site soil or forest duff. Laboratory analytical reports are attached to this letter for review. Also, see the attached “Form 2 – Characterization Sampling Results” document that separately summarizes the above- discussed results as required in Ecology’s TSP Model Remedies Guidance document. American Pride Lending, LLC ES-8485.01 May 16, 2022 Page 5 Earth Solutions NW, LLC Summary and Conclusions Consistent with the Client’s request, ESNW completed a Limited Phase II ESA at the subject site. This investigation included: (1) collecting 24 discrete soil samples across the subject site in accordance with the referenced TSP Model Remedies Guidance document (Ecology, July 2019); (2) submitting the soil samples to a Washington State-certified laboratory to be analyzed for the presence of total arsenic and lead; and (3) completion of this letter. In conclusion, laboratory analytical results identified no elevated concentrations (as defined in the “Applicable Regulatory Standards – Soil” section of this letter) of arsenic or lead in soil at the subject site. Soil samples collected at the site and the results discussed and recorded in this letter can be considered “compliance” samples. This letter presents evidence that the site has not been impacted by elevated concentrations of arsenic or lead from the historical Asarco Smelter. Recommendations Based on the findings of this assessment, no soil remediation is considered warranted at the subject site in connection with potential arsenic and/or lead impacts from the historical Asarco Smelter. Limitations The work described herein was performed upon request by the Client after discussions relating to the potential for TSP-related arsenic and lead soil impacts at the subject property. The findings and recommendations in this letter are made based upon the analytical results, field observations, and our best professional judgement. It is possible that unforeseen events could occur that may limit the effectiveness of the assessment. Although risk can never be eliminated, more detailed and extensive sampling and testing would yield better management of site risks. Since such extensive services involve greater expense, we ask our clients to participate in identifying the level of service that will provide them with an acceptable level of risk. Please contact the signatories of this letter if you would like to discuss this issue of risk further. The scope of work on this project was presented in our March 10, 2022 Phase II Environmental Site Assessment proposal (Proposal No. PES-8485.01) and subsequently approved by American Pride Lending, LLC as our Client. Please be aware our scope of work was limited to those items specifically identified in the proposal. Other activities not specifically included in the presented scope of work (in the proposal, correspondence, or this letter) are excluded and should not be considered part of our scope of services. Land use, site conditions (both on-site and off-site), and other factors will change over time. Since site activities and regulations beyond our control could change at any time after the completion of this letter, our observations, findings, and opinions can be considered valid only as of the date of the site visit (April 14, 2022). American Pride Lending, LLC ES-8485.01 May 16, 2022 Page 6 Earth Solutions NW, LLC This letter may be used by the Client and only for the purposes stated within a reasonable time from its issuance, but in no event later than one year from the date of this letter. Any party other than the Client who would like to use this letter shall notify ESNW of such intended use. Based on the intended use of this letter, ESNW may require that additional work be performed and that a revised letter be issued. Non-compliance with any of these requirements by the client or anyone else will release ESNW from any liability resulting from the use of this letter by any unauthorized party. No warranty, either expressed or implied, is made. Closing We trust this letter meets your current needs and appreciate the opportunity to provide our consulting services to American Pride Lending, LLC. Please contact the undersigned at (425) 449-4704 if you have any questions or require additional information. Sincerely, EARTH SOLUTIONS NW, LLC Kyler T. Kelly, L.G. Ted W. Sykes Project Geologist Environmental Senior Project Manager Kyle R. Campbell, P.E. Principal Engineer Attachments: Plate 1 – Vicinity Map Plate 2 – Decision Units Plate 3 – Soil Sampling Location Plan Form 1 – Characterization Sampling Form 2 – Characterization Sampling Results OnSite Environmental Analytical Laboratory Reports Drwn.CAM Checked KTK Date May 2022 Date 05/04/2022 Proj.No.8485.01 Plate 1 Geotechnical Engineering,Construction Observation/Testing and Environmental Services Earth Solutions NWLLCEarthSolutionsNWLLC EarthSolutions NW LLC Vicinity Map S.288th Street Short Plat Federal Way,Washington Reference: King County,Washington OpenStreetMap.org NORTH NOTE:This plate may contain areas of color.ESNW cannot be responsible for any subsequent misinterpretation of the information resulting from black &white reproductions of this plate. Federal Way SITE Kent Des Moines Drwn.CAM Checked KTK Date May 2022 Date 05/04/2022 Proj.No.8485.01 Plate 2 Geotechnical Engineering,Construction Observation/Testing and Environmental Services Earth Solutions NWLLCEarthSolutionsNWLLC EarthSolutions NW LLC s.288th street Undeveloped Land 275' 145' Decision Units S.288th Street Short Plat Federal Way,Washington NOTE:This plate may contain areas of color.ESNW cannot be responsible for any subsequent misinterpretation of the information resulting from black &white reproductions of this plate. NOTE:The graphics shown on this plate are not intended for design purposes or precise scale measurements,but only to illustrate the approximate test locations relative to the approximate locations of existing and /or proposed site features.The information illustrated is largely based on data provided by the client at the time of our study.ESNW cannot be responsible for subsequent design changes or interpretation of the data by others. LEGEND Subject Site Existing Building NOT -TO -SCALE NORTH Drwn.CAM Checked KTK Date May 2022 Date 05/04/2022 Proj.No.8485.01 Plate 3 Geotechnical Engineering,Construction Observation/Testing and Environmental Services Earth Solutions NWLLCEarthSolutionsNWLLC EarthSolutions NW LLC Duff 1 Duff 4 Duff 2 Duff 3 SS-1:6" SS-1:12" SS-2:6" SS-3:6" SS-3:12" SS-4:6"SS-5:6" SS-6:6" SS-7:6" SS-8:6" SS-9:6" SS-10:6" SS-10:12" SS-11:6" SS-12:6" SS-13:6" SS-14:6" SS-14:12" SS-15:6" SS-16:6" s.288th street Soil Sampling Location Plan S.288th Street Short Plat Federal Way,Washington NOTE:This plate may contain areas of color.ESNW cannot be responsible for any subsequent misinterpretation of the information resulting from black &white reproductions of this plate. NOTE:The graphics shown on this plate are not intended for design purposes or precise scale measurements,but only to illustrate the approximate test locations relative to the approximate locations of existing and /or proposed site features.The information illustrated is largely based on data provided by the client at the time of our study.ESNW cannot be responsible for subsequent design changes or interpretation of the data by others. LEGEND Approximate Location of ESNW Soil Sample Subject Site Existing Building NOT -TO -SCALE NORTH SS-5:6" Washington Department of Ecology Tacoma Smelter Plume Model Remedies Guidance 77 Characterization Sampling Reminder: Keep a copy of the filled out forms to pass on to future property owners. Part 1: Determine your decision units 1. Total property size: _________ acres 2. In an area of arsenic >100 ppm (see map on inside cover): yes no 3. Check all that apply and identify decision units in any of these cases: Property is larger than 0.25 acres Property currently or historically had a mix of forested and developed land. More than one type of land use is planned for the development Parts of the property will be play areas, gardens, or other high use areas Property has geographic features, such as steep slopes or wetlands Areas have forest duff that needs separate sampling 4. On the next page, list the decision units on your property and their size in Table 1. Use Table 2 to determine the number of samples needed for each decision unit. Part 2: Soil sample depth in upland areas 5. Fill in Table 1 on the following page with the sample depths. At every location:Take samples from the top 0-6 inches of soil, after clearing away grass, leaves, gravel, or debris on the surface (Figure 3) At every fourth location (25% of the samples):Also take a sample from the 6-12 inch depth If you are sampling in natural areas:Take soil samples from 0-6 inches below ground surface (bgs), 6-12 inches bgs, 12-24 inches bgs, 24-36 inches bgs from every location Areas where fill dirt or topsoil was added in the past:At every fourth location, take a sample from the top 0-6 inches of the original land surface, if it is deeper than 12 inches If using mixing as a remedy:At every fourth sample location, take a sample from the depth you to which you will mix For forest duff: Take six subsamples throughout the decision unit and combine into one sample. If your decision unit is larger than 0.25 acres, Form 1 Washington Department of Ecology Tacoma Smelter Plume Model Remedies Guidance 78 calculate how many composite duff samples to take using Table 1a in Chapter 1 of this guidance Part 2A: Soil sample depth in wetlands At every location:Take samples from the top 0-4 inches of sediment At every location:Take samples from the top 4-8 inches of sediment Part 3: Overlay a sampling grid for each decision unit 6. Attach a diagram showing property dimensions and locations of decision units. 7. Attach a separate diagram for each decision unit, including dimensions, existing structures, and which structures will remain after development. Table 1. Characterization sampling plan Decision unit description (past use, planned use) Acres/ft2 # of samples Sample depth/duff layer 1. 2. 3. 4. Washington Department of Ecology Tacoma Smelter Plume Model Remedies Guidance 79 Table 2. Number of sample locations per decision unit by planned use and estimated arsenic level. Sampling area Residential, parks, commercial (# samples needed) Forest and open land (# samples needed) Acres Arsenic >100 ppm Arsenic <100 ppm Arsenic >100 ppm Arsenic 20-100 ppm 0.25* 10 8 8 8 1 20 16 16 12 5 40 32 30 24 10 60 48 40 32 20 80 64 50 40 100 120 90 70 60 >100 120 +1 per 5 acres 90 + 1 per 5 acres 70 + 1 per 5 acres 60 + 1 per 5 acres *0.25 acres ~11,000 square feet This page intentionally left blank Washington Department of Ecology Tacoma Smelter Plume Model Remedies Guidance 80 Washington Department of Ecology Tacoma Smelter Plume Model Remedies Guidance 81 Characterization Sampling Results Reminder: Keep a copy of the filled out forms to pass on to future property owners. Filling in the sample inventory List the samples by decision unit in the inventory on the back of this page. Enter the depth of each sample. When sampling multiple depths at a single location, mark each depth as a separate sample number. Optional: If you have duff, remember to sample and analyze that separately from the soil. Next, fill in the date and time. Note any unusual observations (high soil disturbance, heavy rain, etc.) in the “Comments” column. Complete the rest of the columns when you get the sampling results. Determining if arsenic or lead is elevated 1. Calculate average arsenic and lead levels for each sampling depth and each decision unit and enter them on the inventory sheet. For each decision unit circle the arsenic average that exceeds 20 ppm, or average lead that exceeds 250 ppm. For decision units in natural areas, calculate average arsenic and lead for each sampling location in addition to calculating the averages for each sampling depth. 2. Circle every value where maximum arsenic exceeds 40 ppm and where maximum lead exceeds 500 ppm. 3. Attach a copy of your lab results and chain of custody. 4. For decision units with a circled value (maximum or average), note in the “Comment” column that cleanup is needed for that entire decision unit. Turn to Chapter 2 to review options for cleaning up those decision units. If no decision units have elevated arsenic or lead, no cleanup is necessary. Because no cleanup is being done, you do not need to take any compliance samples. The characterization samples demonstrate that your soils meet state standards. Treat these results as “compliance” sampling results and read Chapter 7 for next steps. Form 2 Washington Department of Ecology Tacoma Smelter Plume Model Remedies Guidance 82 Soil Characterization Sampling Inventory Sheet Property address: Phone: Sampled by: Testing Parameters (ppm) DU Sampl e no. Soil Depth /Duff Date Time Notes Arsenic Avg. arsenic Lead Avg lead OnSite Environmental, Inc. 14648 NE 95th Street, Redmond, WA 98052 (425) 883-3881 This report pertains to the samples analyzed in accordance with the chain of custody, and is intended only for the use of the individual or company to whom it is addressed. 14648 NE 95th Street, Redmond, WA 98052  (425) 883-3881 April 22, 2022 Ted Sykes Earth Solutions NW, LLC 15365 NE 90th Street, Suite 100 Redmond, WA 98052 Re: Analytical Data for Project ES-8485.01 Laboratory Reference No. 2204-174 Dear Ted: Enclosed are the analytical results and associated quality control data for samples submitted on April 14, 2022. The standard policy of OnSite Environmental, Inc. is to store your samples for 30 days from the date of receipt. If you require longer storage, please contact the laboratory. We appreciate the opportunity to be of service to you on this project. If you have any questions concerning the data, or need additional information, please feel free to call me. Sincerely, David Baumeister Project Manager Enclosures 2 OnSite Environmental, Inc. 14648 NE 95th Street, Redmond, WA 98052 (425) 883-3881 This report pertains to the samples analyzed in accordance with the chain of custody, and is intended only for the use of the individual or company to whom it is addressed. Date of Report: April 22, 2022 Samples Submitted: April 14, 2022 Laboratory Reference: 2204-174 Project: ES-8485.01 Case Narrative Samples were collected on April 14, 2022 and received by the laboratory on April 14, 2022. They were maintained at the laboratory at a temperature of 2oC to 6oC. Please note that any and all soil sample results are reported on a dry-weight basis, unless otherwise noted below. General QA/QC issues associated with the analytical data enclosed in this laboratory report will be indicated with a reference to a comment or explanation on the Data Qualifier page. More complex and involved QA/QC issues will be discussed in detail below. 3 OnSite Environmental, Inc. 14648 NE 95th Street, Redmond, WA 98052 (425) 883-3881 This report pertains to the samples analyzed in accordance with the chain of custody, and is intended only for the use of the individual or company to whom it is addressed. Date of Report: April 22, 2022 Samples Submitted: April 14, 2022 Laboratory Reference: 2204-174 Project: ES-8485.01 TOTAL METALS EPA 6010D Matrix: Soil Units: mg/Kg (ppm) Date Date Analyte Result PQL Method Prepared Analyzed Flags Client ID: SS-1:6" Laboratory ID: 04-174-01 Arsenic ND 12 EPA 6010D 4-18-22 4-18-22 Lead 7.4 5.8 EPA 6010D 4-18-22 4-18-22 Client ID: SS-2:12" Laboratory ID: 04-174-02 Arsenic ND 11 EPA 6010D 4-18-22 4-18-22 Lead ND 5.5 EPA 6010D 4-18-22 4-18-22 Client ID: SS-2:6" Laboratory ID: 04-174-03 Arsenic ND 12 EPA 6010D 4-18-22 4-18-22 Lead 22 5.9 EPA 6010D 4-18-22 4-18-22 Client ID: SS-3:6" Laboratory ID: 04-174-04 Arsenic ND 11 EPA 6010D 4-18-22 4-18-22 Lead 21 5.7 EPA 6010D 4-18-22 4-18-22 Client ID: SS-3:12" Laboratory ID: 04-174-05 Arsenic ND 11 EPA 6010D 4-18-22 4-18-22 Lead ND 5.7 EPA 6010D 4-18-22 4-18-22 Client ID: SS-4:6" Laboratory ID: 04-174-06 Arsenic ND 12 EPA 6010D 4-18-22 4-18-22 Lead 18 6.1 EPA 6010D 4-18-22 4-18-22 Client ID: SS-5:6" Laboratory ID: 04-174-07 Arsenic ND 12 EPA 6010D 4-18-22 4-18-22 Lead 16 5.9 EPA 6010D 4-18-22 4-18-22 4 OnSite Environmental, Inc. 14648 NE 95th Street, Redmond, WA 98052 (425) 883-3881 This report pertains to the samples analyzed in accordance with the chain of custody, and is intended only for the use of the individual or company to whom it is addressed. Date of Report: April 22, 2022 Samples Submitted: April 14, 2022 Laboratory Reference: 2204-174 Project: ES-8485.01 TOTAL METALS EPA 6010D Matrix: Soil Units: mg/Kg (ppm) Date Date Analyte Result PQL Method Prepared Analyzed Flags Client ID: SS-6:6" Laboratory ID: 04-174-08 Arsenic ND 12 EPA 6010D 4-18-22 4-18-22 Lead ND 5.8 EPA 6010D 4-18-22 4-18-22 Client ID: SS-7:6" Laboratory ID: 04-174-09 Arsenic ND 12 EPA 6010D 4-18-22 4-18-22 Lead 22 6.2 EPA 6010D 4-18-22 4-18-22 Client ID: SS-8:6" Laboratory ID: 04-174-10 Arsenic ND 12 EPA 6010D 4-18-22 4-18-22 Lead 26 6.2 EPA 6010D 4-18-22 4-18-22 Client ID: SS-9:6" Laboratory ID: 04-174-11 Arsenic ND 12 EPA 6010D 4-18-22 4-18-22 Lead 11 5.9 EPA 6010D 4-18-22 4-18-22 Client ID: SS-10:6" Laboratory ID: 04-174-12 Arsenic ND 15 EPA 6010D 4-18-22 4-18-22 Lead 36 7.5 EPA 6010D 4-18-22 4-18-22 Client ID: SS-10:12" Laboratory ID: 04-174-13 Arsenic ND 11 EPA 6010D 4-18-22 4-18-22 Lead ND 5.7 EPA 6010D 4-18-22 4-18-22 Client ID: SS-11:6" Laboratory ID: 04-174-14 Arsenic ND 13 EPA 6010D 4-18-22 4-18-22 Lead 19 6.5 EPA 6010D 4-18-22 4-18-22 5 OnSite Environmental, Inc. 14648 NE 95th Street, Redmond, WA 98052 (425) 883-3881 This report pertains to the samples analyzed in accordance with the chain of custody, and is intended only for the use of the individual or company to whom it is addressed. Date of Report: April 22, 2022 Samples Submitted: April 14, 2022 Laboratory Reference: 2204-174 Project: ES-8485.01 TOTAL METALS EPA 6010D Matrix: Soil Units: mg/Kg (ppm) Date Date Analyte Result PQL Method Prepared Analyzed Flags Client ID: SS-12:6" Laboratory ID: 04-174-15 Arsenic ND 13 EPA 6010D 4-18-22 4-18-22 Lead 36 6.6 EPA 6010D 4-18-22 4-18-22 Client ID: SS-13:6" Laboratory ID: 04-174-16 Arsenic ND 12 EPA 6010D 4-18-22 4-18-22 Lead ND 5.8 EPA 6010D 4-18-22 4-18-22 Client ID: SS-14:6" Laboratory ID: 04-174-17 Arsenic ND 11 EPA 6010D 4-18-22 4-18-22 Lead ND 5.6 EPA 6010D 4-18-22 4-18-22 Client ID: SS-14:12" Laboratory ID: 04-174-18 Arsenic ND 11 EPA 6010D 4-18-22 4-18-22 Lead ND 5.7 EPA 6010D 4-18-22 4-18-22 Client ID: SS-15:6" Laboratory ID: 04-174-19 Arsenic ND 11 EPA 6010D 4-18-22 4-18-22 Lead ND 5.7 EPA 6010D 4-18-22 4-18-22 Client ID: SS-16:6" Laboratory ID: 04-174-20 Arsenic ND 12 EPA 6010D 4-18-22 4-18-22 Lead 14 5.8 EPA 6010D 4-18-22 4-18-22 Client ID: Duff-1 Laboratory ID: 04-174-21 Arsenic ND 13 EPA 6010D 4-18-22 4-18-22 Lead ND 6.4 EPA 6010D 4-18-22 4-18-22 6 OnSite Environmental, Inc. 14648 NE 95th Street, Redmond, WA 98052 (425) 883-3881 This report pertains to the samples analyzed in accordance with the chain of custody, and is intended only for the use of the individual or company to whom it is addressed. Date of Report: April 22, 2022 Samples Submitted: April 14, 2022 Laboratory Reference: 2204-174 Project: ES-8485.01 TOTAL METALS EPA 6010D Matrix: Soil Units: mg/Kg (ppm) Date Date Analyte Result PQL Method Prepared Analyzed Flags Client ID: Duff-2 Laboratory ID: 04-174-22 Arsenic ND 13 EPA 6010D 4-18-22 4-18-22 Lead 27 6.5 EPA 6010D 4-18-22 4-18-22 Client ID: Duff-3 Laboratory ID: 04-174-23 Arsenic ND 15 EPA 6010D 4-18-22 4-18-22 Lead 32 7.6 EPA 6010D 4-18-22 4-18-22 Client ID: Duff-4 Laboratory ID: 04-174-24 Arsenic ND 12 EPA 6010D 4-18-22 4-18-22 Lead ND 6.2 EPA 6010D 4-18-22 4-18-22 7 OnSite Environmental, Inc. 14648 NE 95th Street, Redmond, WA 98052 (425) 883-3881 This report pertains to the samples analyzed in accordance with the chain of custody, and is intended only for the use of the individual or company to whom it is addressed. Date of Report: April 22, 2022 Samples Submitted: April 14, 2022 Laboratory Reference: 2204-174 Project: ES-8485.01 TOTAL METALS EPA 6010D QUALITY CONTROL Matrix: Soil Units: mg/Kg (ppm) Date Date Analyte Result PQL Method Prepared Analyzed Flags METHOD BLANK Laboratory ID: MB0418SM1 Arsenic ND 10 EPA 6010D 4-18-22 4-18-22 Lead ND 5.0 EPA 6010D 4-18-22 4-18-22 Laboratory ID: MB0418SM4 Arsenic ND 10 EPA 6010D 4-18-22 4-18-22 Lead ND 5.0 EPA 6010D 4-18-22 4-18-22 Source Percent Recovery RPD Analyte Result Spike Level Result Recovery Limits RPD Limit Flags DUPLICATE Laboratory ID: 04-190-01 ORIG DUP Arsenic ND ND NA NA NA NA NA 20 Lead ND ND NA NA NA NA NA 20 Laboratory ID: 04-174-20 ORIG DUP Arsenic ND ND NA NA NA NA NA 20 Lead 11.9 11.5 NA NA NA NA 4 20 MATRIX SPIKES Laboratory ID: 04-190-01 MS MSD MS MSD MS MSD Arsenic 98.5 96.7 100 100 ND 99 97 75-125 2 20 Lead 252 251 250 250 ND 101 101 75-125 0 20 Laboratory ID: 04-174-20 MS MSD MS MSD MS MSD Arsenic 98.6 98.6 100 100 ND 99 99 75-125 0 20 Lead 261 262 250 250 11.9 100 100 75-125 1 20 8 OnSite Environmental, Inc. 14648 NE 95th Street, Redmond, WA 98052 (425) 883-3881 This report pertains to the samples analyzed in accordance with the chain of custody, and is intended only for the use of the individual or company to whom it is addressed. Date of Report: April 22, 2022 Samples Submitted: April 14, 2022 Laboratory Reference: 2204-174 Project: ES-8485.01 % MOISTURE Date Client ID Lab ID % Moisture Analyzed SS-1:6" 04-174-01 13 4-18-22 SS-2:12" 04-174-02 9 4-18-22 SS-2:6" 04-174-03 15 4-18-22 SS-3:6" 04-174-04 12 4-18-22 SS-3:12" 04-174-05 12 4-18-22 SS-4:6" 04-174-06 17 4-18-22 SS-5:6" 04-174-07 15 4-18-22 SS-6:6" 04-174-08 14 4-18-22 SS-7:6" 04-174-09 19 4-18-22 SS-8:6" 04-174-10 19 4-18-22 SS-9:6" 04-174-11 16 4-18-22 SS-10:6" 04-174-12 34 4-18-22 SS-10:12" 04-174-13 12 4-18-22 SS-11:6" 04-174-14 23 4-18-22 SS-12:6" 04-174-15 24 4-18-22 SS-13:6" 04-174-16 14 4-18-22 SS-14:6" 04-174-17 11 4-18-22 SS-14:12" 04-174-18 12 4-18-22 SS-15:6" 04-174-19 13 4-18-22 SS-16:6" 04-174-20 14 4-18-22 Duff-1 04-174-21 21 4-18-22 Duff-2 04-174-22 23 4-18-22 Duff-3 04-174-23 34 4-18-22 Duff-4 04-174-24 20 4-18-22 9 OnSite Environmental, Inc. 14648 NE 95th Street, Redmond, WA 98052 (425) 883-3881 This report pertains to the samples analyzed in accordance with the chain of custody, and is intended only for the use of the individual or company to whom it is addressed. Data Qualifiers and Abbreviations A - Due to a high sample concentration, the amount spiked is insufficient for meaningful MS/MSD recovery data. B - The analyte indicated was also found in the blank sample. C - The duplicate RPD is outside control limits due to high result variability when analyte concentrations are within five times the quantitation limit. E - The value reported exceeds the quantitation range and is an estimate. F - Surrogate recovery data is not available due to the high concentration of coeluting target compounds. H - The analyte indicated is a common laboratory solvent and may have been introduced during sample preparation, and be impacting the sample result. I - Compound recovery is outside of the control limits. J - The value reported was below the practical quantitation limit. The value is an estimate. K - Sample duplicate RPD is outside control limits due to sample inhomogeneity. The sample was re-extracted and re-analyzed with similar results. L - The RPD is outside of the control limits. M - Hydrocarbons in the gasoline range are impacting the diesel range result. M1 - Hydrocarbons in the gasoline range (toluene-naphthalene) are present in the sample. N - Hydrocarbons in the lube oil range are impacting the diesel range result. N1 - Hydrocarbons in diesel range are impacting lube oil range results. O - Hydrocarbons indicative of heavier fuels are present in the sample and are impacting the gasoline result. P - The RPD of the detected concentrations between the two columns is greater than 40. Q - Surrogate recovery is outside of the control limits. S - Surrogate recovery data is not available due to the necessary dilution of the sample. T - The sample chromatogram is not similar to a typical ____________. U - The analyte was analyzed for, but was not detected above the reported sample quantitation limit. U1 - The practical quantitation limit is elevated due to interferences present in the sample. V - Matrix Spike/Matrix Spike Duplicate recoveries are outside control limits due to matrix effects. W - Matrix Spike/Matrix Spike Duplicate RPD are outside control limits due to matrix effects. X - Sample extract treated with a mercury cleanup procedure. X1 - Sample extract treated with a sulfuric acid/silica gel cleanup procedure. X2 - Sample extract treated with a silica gel cleanup procedure. Y - The calibration verification for this analyte exceeded the 20% drift specified in methods 8260 & 8270, and therefore the reported result should be considered an estimate. The overall performance of the calibration verification standard met the acceptance criteria of the method. Y1 - Negative effects of the matrix from this sample on the instrument caused values for this analyte in the bracketing continuing calibration verification standard (CCVs) to be outside of 20% acceptance criteria. Because of this, quantitation limits and sample concentrations should be considered estimates. Z - ND - Not Detected at PQL PQL - Practical Quantitation Limit RPD - Relative Percent Difference Appendix C No Action for Tacoma Smelter Plume Letter by Washington State Department of Ecology dates June 22, 2022. ` Heather Tatro, Associate Planner 6/22/2022 Encompass 165 NE Juniper St, Suite 201 Issaquah, WA 98027 Re: 2240 S 288th St Short Plat, Federal Way, Washington Dear Heather Tatro, Thank you for the opportunity to provide comments on the 2240 S 288th Street Short Plat project. The project property is located in Federal Way, Washington on one, 0.9-acre King County parcel (3322049023). The proposed project is located in an area affected by arsenic and lead in the soil resulting from the air emissions from the old Asarco Smelter in Ruston, Washington. American Price Lending LLC (American) proposed to develop this property into a residential development. Ecology recommended soil sampling to evaluate the levels of arsenic and lead in the soil prior to construction. Ecology also recommended enrollment in the Voluntary Cleanup Program (VCP) with Ecology if lead, arsenic, or other contaminants are found at concentrations above Model Toxics Control Act (MTCA) Method A cleanup levels. Earth Solutions NW LLC (ES), on behalf of American, conducted soil sampling on the project property on April 14, 2022. ES collected 20 soil samples from 16 sampling locations. ES collected 16 soil samples from 0 to 6 inches below ground surface (bgs) and four samples from 6 to 12 inches bgs. They also collected four; 6-point composite duff samples (Figure 2). ES submitted the samples to OnSite Environmental laboratory in Redmond, Washington for an analysis of arsenic and lead concentrations with an Environmental Protection Agency (EPA) Method 6010D. ES prepared a report summarizing the results of the soil sampling 1. Ecology reviewed the report and concluded that the average soil concentrations were below the cleanup level of 20 milligrams per kilogram (mg/kg) for arsenic 1 Earth Solutions NW, LLC. Limited Phase II Environmental Site Assessment, Tacoma Smelter Plume, South 288th Street Short Plat, Federal Way, Washington. May 16, 2022. THE MTCA SOIL CLEANUP LEVELS: Average arsenic ≤ 20 mg/kg Average lead ≤ 250 mg/kg AND Maximum arsenic ≤ 40 mg/kg Maximum lead ≤ 500 mg/kg Figure 1. Vicinity Map Project Location and 250 mg/kg for lead (Table 1). Similarly, no samples exceeded the maximum allowable concentration for a single soil sample of 40 mg/kg for arsenic or 500 mg/kg for lead. Table 1. Summary of Soil Sampling ay Sample Depth (feet) Arsenic mg/kg (EPA 6010D) Lead mg/kg (EPA 6010D) Minimum Maximum Average Minimum Maximum Average 0-6 11 15 12 5.6 36 17 6-12 11 11 11 5.5 5.7 5.65 Duff 12 15 13.25 6.2 32 17.9 MTCA Levels 40 20 500 250 Ecology does not recommend this property enter the Voluntary Cleanup Program. No soil remediation for the contamination associated with the Tacoma Smelter Plume is needed for this property. Please note, this not a “No Further Action” determination for the property, since the property was not enrolled into the VCP. Eva Barber Technical Assistance Coordinator Toxics Cleanup Program Southwest Regional Office Washington State Department of Ecology; Eva.barber@ecy.wa.gov; Phone: 360-999-9593 Figure 2. Approximate locations of soil samples Appendix D WWHM Output WWHM2012 PROJECT REPORT WWHM_No Detention 3/17/2023 11:33:36 AM Page 2 General Model Information Project Name:WWHM_No Detention Site Name: Site Address: City: Report Date:3/17/2023 Gage:Seatac Data Start:1948/10/01 Data End:2009/09/30 Timestep:Hourly Precip Scale:1.000 Version Date:2019/09/13 Version:4.2.17 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year WWHM_No Detention 3/17/2023 11:33:36 AM Page 3 Landuse Basin Data Predeveloped Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Mod 0.695 C, Forest, Steep 0.095 Pervious Total 0.79 Impervious Land Use acre Impervious Total 0 Basin Total 0.79 Element Flows To: Surface Interflow Groundwater WWHM_No Detention 3/17/2023 11:33:36 AM Page 4 Mitigated Land Use Basin 1 Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Mod 0.138 C, Forest, Mod 0.379 C, Forest, Steep 0.028 C, Lawn, Flat 0.082 Pervious Total 0.627 Impervious Land Use acre ROOF TOPS FLAT 0.094 DRIVEWAYS FLAT 0.023 DRIVEWAYS MOD 0.046 Impervious Total 0.163 Basin Total 0.79 Element Flows To: Surface Interflow Groundwater WWHM_No Detention 3/17/2023 11:33:36 AM Page 7 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.79 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.627 Total Impervious Area:0.163 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.022603 5 year 0.036397 10 year 0.044067 25 year 0.051974 50 year 0.056717 100 year 0.060638 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.0617 5 year 0.083938 10 year 0.100269 25 year 0.122807 50 year 0.141028 100 year 0.160519 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.025 0.067 1950 0.047 0.124 1951 0.052 0.076 1952 0.017 0.048 1953 0.013 0.044 1954 0.018 0.058 1955 0.033 0.066 1956 0.028 0.066 1957 0.022 0.072 1958 0.023 0.057 WWHM_No Detention 3/17/2023 11:33:49 AM Page 8 1959 0.019 0.044 1960 0.033 0.065 1961 0.019 0.052 1962 0.011 0.043 1963 0.015 0.052 1964 0.019 0.059 1965 0.014 0.049 1966 0.014 0.053 1967 0.033 0.073 1968 0.019 0.076 1969 0.019 0.051 1970 0.015 0.052 1971 0.014 0.052 1972 0.039 0.090 1973 0.017 0.048 1974 0.018 0.054 1975 0.028 0.082 1976 0.017 0.052 1977 0.002 0.047 1978 0.016 0.065 1979 0.009 0.060 1980 0.025 0.069 1981 0.013 0.064 1982 0.027 0.102 1983 0.023 0.057 1984 0.015 0.055 1985 0.008 0.041 1986 0.041 0.082 1987 0.035 0.075 1988 0.013 0.036 1989 0.008 0.041 1990 0.056 0.131 1991 0.048 0.116 1992 0.016 0.053 1993 0.018 0.037 1994 0.004 0.033 1995 0.025 0.048 1996 0.049 0.092 1997 0.046 0.076 1998 0.009 0.062 1999 0.029 0.118 2000 0.018 0.067 2001 0.002 0.042 2002 0.023 0.067 2003 0.016 0.065 2004 0.041 0.133 2005 0.023 0.056 2006 0.029 0.060 2007 0.076 0.165 2008 0.062 0.113 2009 0.034 0.073 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.0755 0.1652 2 0.0620 0.1328 3 0.0555 0.1307 WWHM_No Detention 3/17/2023 11:33:49 AM Page 9 4 0.0520 0.1240 5 0.0488 0.1180 6 0.0478 0.1163 7 0.0468 0.1132 8 0.0458 0.1021 9 0.0412 0.0915 10 0.0409 0.0904 11 0.0386 0.0820 12 0.0346 0.0818 13 0.0342 0.0764 14 0.0329 0.0758 15 0.0327 0.0757 16 0.0326 0.0752 17 0.0293 0.0734 18 0.0289 0.0734 19 0.0284 0.0723 20 0.0276 0.0689 21 0.0267 0.0675 22 0.0254 0.0669 23 0.0250 0.0669 24 0.0250 0.0656 25 0.0232 0.0655 26 0.0228 0.0652 27 0.0227 0.0648 28 0.0225 0.0648 29 0.0215 0.0642 30 0.0192 0.0617 31 0.0192 0.0604 32 0.0189 0.0597 33 0.0187 0.0589 34 0.0185 0.0576 35 0.0182 0.0572 36 0.0182 0.0568 37 0.0180 0.0557 38 0.0180 0.0553 39 0.0174 0.0545 40 0.0173 0.0528 41 0.0166 0.0527 42 0.0163 0.0525 43 0.0163 0.0524 44 0.0156 0.0523 45 0.0154 0.0519 46 0.0152 0.0515 47 0.0151 0.0510 48 0.0144 0.0493 49 0.0141 0.0483 50 0.0138 0.0477 51 0.0135 0.0476 52 0.0128 0.0467 53 0.0125 0.0439 54 0.0113 0.0435 55 0.0092 0.0430 56 0.0088 0.0420 57 0.0082 0.0408 58 0.0078 0.0408 59 0.0045 0.0370 60 0.0023 0.0362 61 0.0018 0.0335 WWHM_No Detention 3/17/2023 11:33:49 AM Page 13 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0 acre-feet On-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. Off-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. WWHM_No Detention 3/17/2023 11:33:49 AM Page 14 LID Report WWHM_No Detention 3/17/2023 11:33:57 AM Page 15 Model Default Modifications Total of 0 changes have been made. PERLND Changes No PERLND changes have been made. IMPLND Changes No IMPLND changes have been made. WWHM_No Detention 3/17/2023 11:33:57 AM Page 16 Appendix Predeveloped Schematic WWHM_No Detention 3/17/2023 11:33:59 AM Page 17 Mitigated Schematic WWHM_No Detention 3/17/2023 11:34:00 AM Page 18 Predeveloped UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 WWHM_No Detention.wdm MESSU 25 PreWWHM_No Detention.MES 27 PreWWHM_No Detention.L61 28 PreWWHM_No Detention.L62 30 POCWWHM_No Detention1.dat END FILES OPN SEQUENCE INGRP INDELT 00:60 PERLND 11 PERLND 12 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Basin 1 MAX 1 2 30 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 11 C, Forest, Mod 1 1 1 1 27 0 12 C, Forest, Steep 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 11 0 0 1 0 0 0 0 0 0 0 0 0 12 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* WWHM_No Detention 3/17/2023 11:34:00 AM Page 19 11 0 0 4 0 0 0 0 0 0 0 0 0 1 9 12 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 11 0 0 0 0 0 0 0 0 0 0 0 12 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 11 0 4.5 0.08 400 0.1 0.5 0.996 12 0 4.5 0.08 400 0.15 0.5 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 11 0 0 2 2 0 0 0 12 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 11 0.2 0.5 0.35 6 0.5 0.7 12 0.2 0.3 0.35 6 0.3 0.7 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 11 0 0 0 0 2.5 1 0 12 0 0 0 0 2.5 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC END IWAT-PARM2 IWAT-PARM3 WWHM_No Detention 3/17/2023 11:34:01 AM Page 20 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Basin 1*** PERLND 11 0.695 COPY 501 12 PERLND 11 0.695 COPY 501 13 PERLND 12 0.095 COPY 501 12 PERLND 12 0.095 COPY 501 13 ******Routing****** END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 12.1 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* END PRINT-INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> END HYDR-INIT END RCHRES WWHM_No Detention 3/17/2023 11:34:01 AM Page 21 SPEC-ACTIONS END SPEC-ACTIONS FTABLES END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 SUM PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 SUM IMPLND 1 999 EXTNL PREC WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** COPY 501 OUTPUT MEAN 1 1 12.1 WDM 501 FLOW ENGL REPL END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 12 PERLND PWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 12 MASS-LINK 13 PERLND PWATER IFWO 0.083333 COPY INPUT MEAN END MASS-LINK 13 END MASS-LINK END RUN WWHM_No Detention 3/17/2023 11:34:01 AM Page 22 Mitigated UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 WWHM_No Detention.wdm MESSU 25 MitWWHM_No Detention.MES 27 MitWWHM_No Detention.L61 28 MitWWHM_No Detention.L62 30 POCWWHM_No Detention1.dat END FILES OPN SEQUENCE INGRP INDELT 00:60 PERLND 17 PERLND 11 PERLND 12 PERLND 16 IMPLND 4 IMPLND 5 IMPLND 6 COPY 501 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Basin 1 MAX 1 2 30 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 17 C, Lawn, Mod 1 1 1 1 27 0 11 C, Forest, Mod 1 1 1 1 27 0 12 C, Forest, Steep 1 1 1 1 27 0 16 C, Lawn, Flat 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** WWHM_No Detention 3/17/2023 11:34:01 AM Page 23 17 0 0 1 0 0 0 0 0 0 0 0 0 11 0 0 1 0 0 0 0 0 0 0 0 0 12 0 0 1 0 0 0 0 0 0 0 0 0 16 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 17 0 0 4 0 0 0 0 0 0 0 0 0 1 9 11 0 0 4 0 0 0 0 0 0 0 0 0 1 9 12 0 0 4 0 0 0 0 0 0 0 0 0 1 9 16 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 17 0 0 0 0 0 0 0 0 0 0 0 11 0 0 0 0 0 0 0 0 0 0 0 12 0 0 0 0 0 0 0 0 0 0 0 16 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 17 0 4.5 0.03 400 0.1 0.5 0.996 11 0 4.5 0.08 400 0.1 0.5 0.996 12 0 4.5 0.08 400 0.15 0.5 0.996 16 0 4.5 0.03 400 0.05 0.5 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 17 0 0 2 2 0 0 0 11 0 0 2 2 0 0 0 12 0 0 2 2 0 0 0 16 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 17 0.1 0.25 0.25 6 0.5 0.25 11 0.2 0.5 0.35 6 0.5 0.7 12 0.2 0.3 0.35 6 0.3 0.7 16 0.1 0.25 0.25 6 0.5 0.25 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 17 0 0 0 0 2.5 1 0 11 0 0 0 0 2.5 1 0 12 0 0 0 0 2.5 1 0 16 0 0 0 0 2.5 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 4 ROOF TOPS/FLAT 1 1 1 27 0 5 DRIVEWAYS/FLAT 1 1 1 27 0 6 DRIVEWAYS/MOD 1 1 1 27 0 WWHM_No Detention 3/17/2023 11:34:01 AM Page 24 END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 4 0 0 1 0 0 0 5 0 0 1 0 0 0 6 0 0 1 0 0 0 END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* 4 0 0 4 0 0 0 1 9 5 0 0 4 0 0 0 1 9 6 0 0 4 0 0 0 1 9 END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** 4 0 0 0 0 0 5 0 0 0 0 0 6 0 0 0 0 0 END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC 4 400 0.01 0.1 0.1 5 400 0.01 0.1 0.1 6 400 0.05 0.1 0.08 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN 4 0 0 5 0 0 6 0 0 END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS 4 0 0 5 0 0 6 0 0 END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Basin 1*** PERLND 17 0.138 COPY 501 12 PERLND 17 0.138 COPY 501 13 PERLND 11 0.379 COPY 501 12 PERLND 11 0.379 COPY 501 13 PERLND 12 0.028 COPY 501 12 PERLND 12 0.028 COPY 501 13 PERLND 16 0.082 COPY 501 12 PERLND 16 0.082 COPY 501 13 IMPLND 4 0.094 COPY 501 15 IMPLND 5 0.023 COPY 501 15 IMPLND 6 0.046 COPY 501 15 ******Routing****** WWHM_No Detention 3/17/2023 11:34:01 AM Page 25 END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 12.1 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* END PRINT-INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> END HYDR-INIT END RCHRES SPEC-ACTIONS END SPEC-ACTIONS FTABLES END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 SUM PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 SUM IMPLND 1 999 EXTNL PREC WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** COPY 1 OUTPUT MEAN 1 1 12.1 WDM 701 FLOW ENGL REPL COPY 501 OUTPUT MEAN 1 1 12.1 WDM 801 FLOW ENGL REPL WWHM_No Detention 3/17/2023 11:34:01 AM Page 26 END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 12 PERLND PWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 12 MASS-LINK 13 PERLND PWATER IFWO 0.083333 COPY INPUT MEAN END MASS-LINK 13 MASS-LINK 15 IMPLND IWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 15 END MASS-LINK END RUN WWHM_No Detention 3/17/2023 11:34:01 AM Page 29 Disclaimer Legal Notice This program and accompanying documentation are provided 'as-is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright © by : Clear Creek Solutions, Inc. 2005-2023; All Rights Reserved. Clear Creek Solutions, Inc. 6200 Capitol Blvd. Ste F Olympia, WA. 98501 Toll Free 1(866)943-0304 Local (360)943-0304 www.clearcreeksolutions.com Appendix E Approved Street Modification Request dated November 2, 2022. Western Washington Division Eastern Washington Division 165 NE Juniper St., Ste 201, Issaquah, WA 98027 407 Swiftwater Blvd, Cle Elum, WA 98922 Phone: (425) 392-0250 Phone: (509) 674-7433 www.EncompassES.net October 12, 2022 Mr. EJ Walsh Public Works Director Public Works Department City of Federal Way 33325 8th Avenue South Federal Way, WA 98003 Re: APL Short Plat – 2240 South 288th Street (File #21-105240-00-PC) – Request for Right-of- Way Street Improvements & Dedication Waiver Dear Mr. Walsh, The purpose of this letter is to formally request a Right-of-Way (ROW) Street Improvements Waiver and Right-of-Way Dedication Waiver for the APL Short Plat project on behalf of our client, American Pride Lending, LLC. Per FWRC 19.135.070(1) one of the reasons an Applicant can request modification, deferment or waivers is the improvement as required would not be harmonious with existing street improvements, would not function properly or safely or would not be advantageous to the neighborhood or city as a whole. Per FWRC 19.135.070(2) another reason the Applicant can request a modification, deferment or waiver is the required improvement is part of a larger project that has been scheduled for construction in the City’s adopted six-year transportation improvement program. In the following narrative, we will demonstrate that the frontage improvements are neither harmonious with the existing street improvements or planned future improvements under the S 288th St Road Diet the City has planned for construction in 2024 and that a 20’ ROW dedication is unwarranted as the City’s proposed road diet can be completed within the existing ROW. Current Street Conditions: Per the City’s Comp Plan, S 288th Street is a Minor Arterial planned as a Type “G” street, consisting of a 66-foot street with curb and gutter, 6-foot planter with street trees, 8-foot sidewalks, and streetlights in a 100-foot ROW. The frontage on S 288th Street has been improved with four lanes, including vertical curb/gutter and sidewalks. However, the street was not improved to the current adopted standard. As such, the Applicant would be expected to construct half street improvements as measured from the street centerline and dedicate approximately 20-feet of ROW. APL Short Plat ROW Street Improvements Waiver Request 10-12-2022 Page 2 of 8 Argument: Exhibits A and B show the potential difficulties with constructing the “Type G” cross section as part of this project with the new access location along the eastern and western property lines, respectively. Compared to current conditions, the face of curb would be offset 11 feet to the north. In order to make the transition to a wider road at the east and west ends, we would be required to construct a taper to allow traffic to smoothly move from the existing width to the wider roadway, and back again. According to the 2019 Public Works Department Development Standards for the City of Federal Way, tapers and transitions beyond the project frontage shall be based on the WSDOT Design Manual. Per the 2021 WSDOT Design Manual, taper length should be calculated using a ratio of 21:1 for posted speeds of 35 MPH. This calculation would give a taper length of 231 feet in each direction beyond the project frontage. The results of the taper length calculations show the challenge with constructing the “Type G” street cross section. If the tapers were to be built within the property, there is insufficient length to make the transition out and back again, as the parcel is only 275 feet in length. We assume it would be necessary to put the tapers beyond the east and west ends of the property. In order to build the tapers on the properties to the east and west of our site, there would be a significant disruption of traffic along S 288th Street. Also, pedestrian access along at least 737 linear feet of the sidewalk on the north side of the street would be temporarily closed. To the east of the project’s frontage, the construction would require the temporary relocation of one residential driveway, one commercial driveway, an existing power pole, and a variety of privately maintained landscape frontage improvements located in the public right away. To the west of the project’s frontage, the construction would require the temporary relocation of two residential driveways and a variety of privately maintained landscape frontage improvements located in the public right away. In addition, providing the minimum 231’ taper to west would also cause a disruption for traffic traveling through the S 288th Street/22nd Avenue S intersection. Another complication with constructing the tapers on the east and west end is the transition from the existing sidewalk. There currently is no landscape strip provided between the curb and sidewalk on the north side of S 288th St, so the sidewalk alignment is impossible if adhering to the “Type G” requirements. To allow for these transitions, a triangular easement would have to be established for public access across the two properties west of the APL Short Plat. It also appears that the property east of the APL Short Plat was platted in 2006 under permit number 06 -104450- 00-SU with only a 16’ dedication (no frontage improvements were constructed). The 16’ dedication on the property to the east is insufficient to provide the required improvements without a triangular public access easement being established across that lot as well to accommodate the sidewalk transition. The easements and the road, curb, gutter, and sidewalk improvements would not align with the S 288th St Road Diet proposed for construction in 2024. Although plans are not readily available to the public, per the City’s description of the project on their website, “this is a “road diet” project that will convert S 288th Street from two vehicle lanes in each direction, to a single lane APL Short Plat ROW Street Improvements Waiver Request 10-12-2022 Page 3 of 8 in each direction along with a two-way-left-turn lane and bicycle lanes. For the most part, the existing curb and gutter, as well as existing sidewalks, will remain as-is.” Based on the current ROW width in front of the subject property, there appears to be sufficient space to develop this revised lane layout within the bounds of the existing sidewalks which suggests the frontage improvements required for a Type-G road would be out of line with the future road improvement plan. In addition to the non-harmonious sidewalk and frontage alignment, the road diet makes the 20’ road dedication unnecessary and excessive for the upcoming road improvement. While S 288th Street is still designated as a Type-G road in the Comp Plan, the proposed “road diet” is expected to improve traffic and pedestrian safety, it is funded by a TIB grant and WSDOT grant , can be accomplished with little disruption to the existing City right -of-way, and results in a large cost savings to the City for construction and right-of-way acquisition. We would suggest that through evaluation of the proposed “road diet” construction that the City may consider a comp plan revision/amendment to the required road type for this improved area of S 28 8th St in the future. In addition, we have considered how the required 20’ ROW dedication would affect sight distance from the future access road for the short plat. Sight distance was evaluated for three (3) potential access locations under a separate Site Distance Analysis by Encompass Engineering & Surveying dated October 12, 2022. The three (3) locations are as follows: along the east property line (aligned with 23rd Place S), center of the lot, and along the west property line. The property to the east of our site is at a much higher elevation, and there is a significant slope from their property line down to the existing road. To construct the new access road anywhere along the project’s frontage, a significant cut into the existing hillside will need to occur. A 20’ dedication would result in the access road being tucked behind the higher elevated property at 2312 S 288th St. The uphill properties to the east would prohibit any reasonable site visibi lity to the east and likely make any turn from this site almost a blind corner. If the edge of ROW stays in its existing location, the access road would project further in front of the raised property to the east , providing better site distance for vehicles leaving the site. Although the City’s preferred location for the new access is to be aligned with 23rd Place S, it was determined that sight distance fails under all turning conditions at this location, even when evaluated without the dedication (Exhibit C). Therefore, the 20’ dedication would only exacerbate the sight distance concerns at this location (Exhibit A). The analysis determined that placing the access driveway along the western property line, with no ROW dedication, provides the longest sight distance line to the east and passes the requirements for right turn in, right turn out and left turn in. This makes the western access location the safest possible location for the new access road on the project site if the edge of ROW stays in the existing location (see Exhibit D). However, the uphill properties could still prove to be obstructive to sight distance if the 20’ ROW dedication is enforced (Exhibit B). Similarly with the eastern access location, a 20’ dedication could result in the western access road being tucked behind the higher elevated portions of the property and would negatively impact site visibility to the east. Please refer to APL Short Plat ROW Street Improvements Waiver Request 10-12-2022 Page 4 of 8 the Site Distance Analysis by Encompass Engineering & Surveying dated October 12, 2022 for additional information. We feel that the rationale above presents several compelling reasons for waiving the frontage improvement requirement and the 20-foot road dedication requirement for this project. If you have any questions or need any additional information, please contact me by phone at 425-392- 0250 or by email at BBennington@EncompassES.net. Thank you for your consideration of this waiver request. Sincerely, Encompass Engineering & Surveying, Inc. on behalf of American Pride Lending, LLC Briana Bennington, PE Project Engineer Referenced: CIP 95-07 (Table III-10 of the Federal Way Comprehensive Plan Chapter III) S 288th St Road Diet webpage S 288th St Road Diet (16th Ave S to 34th Ave S) | City of Federal Way US Dept of Transportation Road Diets Notice Road Diets (Roadway Reconfiguration) (cityoffederalway.com) LUTC Agenda Packet 07/11/22 04-03-06 LUTC Agenda (cityoffederalway.com) Site Distance Analysis by Encompass Engineering & Surveying dated October 12, 2022 Exhibits: Exhibit A – Conceptual Site Plan (East Access – Dedication) Exhibit B – Conceptual Site Plan (West Access – Dedication) Exhibit C – Conceptual Site Plan (East Access – No Dedication) Exhibit D – Conceptual Site Plan (West Access – No Dedication) S 288TH STTRACT CACCESSLOT 2LOT 1TRACT A10' LANDSCAPE/OPEN SPACETRACT DOPEN SPACE20' ROW DEDICATIONLOT 3TRACT BSTORM/OPEN SPACE23RD PLACE SCURVE TABLEPARCEL AREA TABLESHEETAPPROVEDCHECKEDDRAWNDESIGNEDSCALEDATEJOB NO.REVISIONS A PORTION OF THE SE 1/4 OF SW 1/4 OF SECTION 33, T. 22 N., R. 04 E., W.M.CITY OF FEDERAL WAY, KING COUNTY, STATE OF WASHINGTONAMERICAN PRIDE LENDING LLCEastern Washington Division 407 Swiftwater Blvd. ▪ Cle Elum, WA 98922 ▪ Phone: (509) 674-7433 Western Washington Division 165 NE Juniper Street, Suite 201 ▪ Issaquah, WA 98027 ▪ Phone: (425) 392-0250Know what'sCallbelow.before you dig.R1 of 1AMERICAN PRIDE LENDING LLC CONCEPTUAL SITE PLAN (EAST ACCESS - DEDICATION) SIKANDER SEKHON (VSM)VICINITY MAPSITESITE DATA:PROJECT TEAM:UTILITY DISTRICT INFORMATION:ZONING INFORMATION:EXISTING UTILITY NOTE:”””DATUM:BASIS OF BEARING:LEGAL DESCRIPTION:CONTRACTOR RESPONSIBILITY:DISCREPANCIES:BENCHMARK:NORTH S 288TH STTRACT AACCESS/STORMLOT 2LOT 120' ROW DEDICATIONTRACT C10' LANDSCAPELOT 323RD PLACE SPARCEL AREA TABLECURVE TABLESHEETAPPROVEDCHECKEDDRAWNDESIGNEDSCALEDATEJOB NO.REVISIONS A PORTION OF THE SE 1/4 OF SW 1/4 OF SECTION 33, T. 22 N., R. 04 E., W.M.CITY OF FEDERAL WAY, KING COUNTY, STATE OF WASHINGTONAMERICAN PRIDE LENDING LLCEastern Washington Division 407 Swiftwater Blvd. ▪ Cle Elum, WA 98922 ▪ Phone: (509) 674-7433 Western Washington Division 165 NE Juniper Street, Suite 201 ▪ Issaquah, WA 98027 ▪ Phone: (425) 392-0250Know what'sCallbelow.before you dig.R1 OF 1AMERICAN PRIDE LENDING LLC CONCEPTUAL SITE PLAN (WEST ACCESS - DEDICATION) SIKANDER SEKHON (VSM)VICINITY MAPSITESITE DATA:PROJECT TEAM:UTILITY DISTRICT INFORMATION:ZONING INFORMATION:EXISTING UTILITY NOTE:”””DATUM:BASIS OF BEARING:LEGAL DESCRIPTION:CONTRACTOR RESPONSIBILITY:DISCREPANCIES:BENCHMARK:NORTH S 288TH STLOT 1TRACT DOPEN SPACETRACT CACCESSLOT 3TRACT BSTORM/OPEN SPACETRACT A10' LANDSCAPE/OPEN SPACELOT 223RD PLACE SPARCEL AREA TABLECURVE TABLESHEETAPPROVEDCHECKEDDRAWNDESIGNEDSCALEDATEJOB NO.REVISIONS A PORTION OF THE SE 1/4 OF SW 1/4 OF SECTION 33, T. 22 N., R. 04 E., W.M.CITY OF FEDERAL WAY, KING COUNTY, STATE OF WASHINGTONAMERICAN PRIDE LENDING LLCEastern Washington Division 407 Swiftwater Blvd. ▪ Cle Elum, WA 98922 ▪ Phone: (509) 674-7433 Western Washington Division 165 NE Juniper Street, Suite 201 ▪ Issaquah, WA 98027 ▪ Phone: (425) 392-0250Know what'sCallbelow.before you dig.R1 of 1AMERICAN PRIDE LENDING LLC CONCEPTUAL SITE PLAN (EAST ACCESS - NO DEDICATION) SIKANDER SEKHON (VSM)VICINITY MAPSITESITE DATA:PROJECT TEAM:UTILITY DISTRICT INFORMATION:ZONING INFORMATION:EXISTING UTILITY NOTE:”””DATUM:BASIS OF BEARING:LEGAL DESCRIPTION:CONTRACTOR RESPONSIBILITY:DISCREPANCIES:BENCHMARK:NORTH TRACT AACCESS/STORMLOT 2LOT 3LOT 1TRACT B10' LANDSCAPES 288TH STPARCEL AREA TABLECURVE TABLESHEETAPPROVEDCHECKEDDRAWNDESIGNEDSCALEDATEJOB NO.REVISIONS A PORTION OF THE SE 1/4 OF SW 1/4 OF SECTION 33, T. 22 N., R. 04 E., W.M.CITY OF FEDERAL WAY, KING COUNTY, STATE OF WASHINGTONAMERICAN PRIDE LENDING LLCEastern Washington Division 407 Swiftwater Blvd. ▪ Cle Elum, WA 98922 ▪ Phone: (509) 674-7433 Western Washington Division 165 NE Juniper Street, Suite 201 ▪ Issaquah, WA 98027 ▪ Phone: (425) 392-0250Know what'sCallbelow.before you dig.R1 of 1AMERICAN PRIDE LENDING LLC CONCEPTUAL SITE PLAN (WEST ACCESS - NO DEDICATION) SIKANDER SEKHON (VSM)VICINITY MAPSITESITE DATA:PROJECT TEAM:UTILITY DISTRICT INFORMATION:ZONING INFORMATION:EXISTING UTILITY NOTE:”””DATUM:BASIS OF BEARING:LEGAL DESCRIPTION:CONTRACTOR RESPONSIBILITY:DISCREPANCIES:BENCHMARK:NORTH