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Home My WebLink AboutRTC RAP USE Memorandum_104059-021-M1 compiled 400 North 34th Street  Suite 100  PO Box 300303  Seattle, Washington 98103-8636  206 632-8020  Fax 206 695-6777  www.shannonwilson.com  104059-021-M1.docx/wp/tvv 1 MEMORANDUM TO: Greg Frost, Stride BRT | BT105 Resident Engineer FROM: Tim Stott, Environmental Engineer DATE: June 25, 2026 PROJECT: BT105 Renton Transit Center PROJ. #: 104059-012 SUBJECT: Reuse of Crushed Asphalt as Fill INTRODUCTION Shimmick Construction Company, the construction contractor for the Renton Transit Center project, has prepared and submitted a Reclaimed Asphalt Pavement (RAP) Blending Program via their subconsultant, Atlas Technical Consultants (Atlas). The purpose of the RAP program is to establish a controlled and documented process for incorporating RAP millings into imported and native aggregate materials. Shannon & Wilson has been requested to review the use of RAP as backfill at the site from an environmental standpoint. RAP – NOT SOLID OR DANGEROUS WASTE The use of RAP as fill is exempt from being considered Solid and Dangerous Waste as per Washington Administrative Code (WAC) 173-303-017(2)(a)(ii) because it substitutes for what would otherwise be imported fill and thereby constitutes recycling. Nevertheless, in consultation with the Washington State Department of Ecology (Ecology), Atlas had the material tested for metals and for acute fish toxicity.1 In summary, although the material is otherwise exempt from being Dangerous Waste, even if non-exempt, testing confirmed the material does not meet these criteria for being Dangerous Waste. USE IN AQUIFER PROTECTION ZONE AND RENTON MUNICIPAL CODE Development regulations in Renton Municipal Code (RMC), Title IV, Development Regulations, Chapter 4, City-Wide Property Development Standards, were reviewed. 1 Washington State Department of Ecology. (2024, March). Biological testing methods 80-12 for the designation of dangerous waste (Publication 80-12). Hazardous Waste and Toxics Reduction Program. MEMORANDUM Reuse of Crushed Asphalt as Fill BT105 Renton Transit Center 104059-012 2 June 25, 2026 Standards for fill material are addressed in Section 4-4-060, Grading, Excavation and Mining Regulations. Relevant portions from Subsection N.4 of include the following:  (a) General – fill materials are not allowed to have more than minor amounts of organic decomposable substances, which RAP does not.  (b) Construction, Demolition, and Land Clearing Waste is Prohibited. RAP is not a waste; it is a recycled material substituting for imported fill, considered a commercial product.  (c) Cleanliness of Fill. The fill is not allowed to constitute a solid or dangerous waste, which RAP is not because it is a recycled material substituting for commercial import fill. Furthermore, the asphalt has been tested for metals content and fish bioassay to ensure it does not exhibit these characteristics of dangerous waste.  (f) Imported fill for projects located in Zone 2 of the Aquifer Protection Area, such as the project site, are required to have a fill source statement; however, this is for the source of imported fill, not for reuse of RAP. The use of recycled asphalt in blended fill material was presented to Mr. Mike Sippo, Civil Engineer with the City of Renton, and he raised no objections, provided that the use of RAP was in accordance with RMC as just outlined. CONTEXT AND RECOMMENDATIONS FOR USE IN AQUIFER RECHARGE AREAS Asphalt (and coal tar seal coat in particular) is known to contain polycyclic aromatic hydrocarbons (PAHs) at low concentrations2 as well as other petroleum constituents. Although RAP is not a waste or contaminated soil, because the material can contain low concentrations of substances deleterious to groundwater quality and the project site is located in an area designated as an aquifer protection zone, it is recommended that the RAP fill be used in a manner consistent with fill soils containing low levels of petroleum contamination, such as Category 2 and 3 soils as designated in Ecology’s Guidance for Remediation of Petroleum Contaminated Sites.3 As such, RAP should only be placed above elevation 24 feet, North American Vertical Datum of 1988 (NAVD88), which is 2 United States Environmental Protection Agency (EPA). (2018, January). Stormwater best management practice, polycyclic aromatic hydrocarbons, coal-tar sealcoat, and stormwater pollution (Fact Sheet Document No. 833-F-12-004). 3 Washington State Department of Ecology. (2016, June). Guidance for remediation of petroleum contaminated sites (Publication No. 10-09-057). Toxics Cleanup Program. MEMORANDUM Reuse of Crushed Asphalt as Fill BT105 Renton Transit Center 104059-012 3 June 25, 2026 approximately a minimum of 1 foot above the highest anticipated ground water elevation (approximately 23 feet NAVD88 based on several years of monitoring events) and below surface paving to limit infiltration and potential migration to groundwater. Enc. Table 1 – Groundwater Elevation Data Figure 1 – Site Plan BT105 Renton Transit Center 5/30/2019 7/22/2021 12/9/2022 7/11/2023 8/10/2023 6/13/2024 09/25/2024- 09/26/2024 12/18/2024- 12/19/2024 3/18/2025- 3/19/2025 08/12/2025- 08/13/2025 11/3/2025 MW-1 20.2 19.65 22.49 -- 20.27 21.12 20.35 21.92 23.62 20 21.76 MW-2 18.49 18.37 19.15 -- 18.7 19.67 18.58 19.92 21.2 18.77 18.59 MW-3 19.57 19.37 20.67 -- 19.25 20.82 19.06 21.12 22 15.73 19.74 MW-4 19.09 -- -- -- -- -- -- -- -- -- -- MW-5 18.72 -- 19.71 -- 18.83 20.02 18.55 20.45 21.51 18.78 18.94 MW-6 19.35 19.18 20.43 -- 19.23 20.48 18.62 20.96 21.9 18.38 19.82 MW-7 19.87 17.51 21.49 -- 19.81 20.85 19.84 21.28 22.49 19.82 21.18 MW-8 -- -- -- 19.72 19 21.27 19.44 22 23.27 19.38 21.49 MW-9 -- -- -- 19.56 19.09 20.29 18.99 21.02 21.98 19.08 20.28 MW-10 -- -- -- 19.12 18.58 19.83 18.34 20.53 21.86 18.55 18.89 MW-11 -- -- -- 18.88 18.38 19.57 18.08 19.88 21.19 18.35 18.34 MW-12 -- -- -- 17.78 17.65 18.45 17.05 18.43 20.4 17.25 17.36 MW-13 -- -- -- 18.48 18.44 19.66 17.88 19.65 21.09 17.84 18.82 MW-14 -- -- -- 20.55 20.03 21.25 20.16 21.65 21.93 19.88 20.84 NOTES: 1 Monitoring well MW-4 was decommissioned in September 2022. Table 1: Groundwater Elevation Data Groundwater Elevation 2 MW-8 through MW-14 were installed in July 2023. Monitoring Well ID 104059-021 104059-021-M1-T1.xlsx - 6/23/2026/wp/tvv RTN002RTN001 RTN003 RTN004 S Grady W a y Ra i n i e r A v e S La k e A v e S Lake Ave S & S Grady Way - Bay 4 South Renton Park & Ride - Bay 1 Ha r d i e A v e S MW-11MW-13 MW-12 MW-14 MW-6 MW-10 RTN001-12 RTN001-13 RTN002-06 MW-8 MW-7 MW-9 MW-1 RTN002-05 MW-2 MW-5 MW-3 Fil e n a m e : D: \ _ P r o j e c t s \ S W \ 1 0 4 0 5 9 . 0 2 1 S T R e n t o n \ 1 0 4 0 5 9 . 0 2 1 S T R e n t o n T C . d w g L a y o u t : s& e p l a n ( 1 ) D a t e : 06 - 2 5 - 2 0 2 6 L o g i n : ca b r y 104059-212 Renton Transit Center (Sound Transit ROW Nos. RTN001-RTN004) Sound Transit Renton, WA Feet 0 75 N Notes: 1.Site features are approximate. June 2026 Site Plan Figure 1 LEGEND Active Monitoring Well Installed July 2023 Decommissioned Monitoring Well Site Boundary ST Parcels Former Buildings RTN001