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HomeMy WebLinkAbout01_Kennydale_ShorExLetter_May 2024 146 N Canal Street, Suite 111  Seattle, WA 98103  www.confenv.com May 2, 2024 Andrew Van Gordon City of Renton, Planning Division 1055 S Grady Way, 6th Floor Renton, WA 98057 Re: Kennydale Lakeline Sewer System Replacement Project – Geotechnical Explorations (Renton CIP Permit: C24001917) Dear Andrew: The City of Renton (Renton) Public Works is proposing a geotechnical investigation along several waterfront houses to support replacement of the Kennydale Lakeline Sewer System (lakeline system). The existing lakeline system provides sanitary sewer service to approximately 57 lakefront homes along Lake Washington from the north end of Gene Coulon Memorial Beach Park to just south of May Creek in Renton. The lakeline system consists of a flush station, an 8- inch cast iron sewer pipe buried offshore in Lake Washington, a system of side sewer laterals connecting customers to the lakeline system, and the Lake Washington No. 2 lift station that pumps the flow to the King County regional system. Renton Public Works conducted a 2018 assessment of the lakeline system, made several attempts at cleaning and maintenance, participated in an in-water sewer workgroup, and evaluated numerous alternatives. As a result, Renton Public Works selected replacement of the existing lakeline system with a land-based grinder pump sewer system. Five borings (B-1 through B-5) are proposed to be conducted in public properties or the public right-of-way (ROW) along Lake Washington Boulevard North to provide soil information for the Kennydale Lakeline Sewer System Replacement Project (Site Plan Fig. 1). Renton Public Works is seeking a Shoreline Exemption and Critical Area Exemption from the Renton Planning Division to conduct this geotechnical exploration work. REQUIRED DOCUMENTS The following documents are provided for this effort:  Land Use Master Application Form  Critical Areas Exemption Form  Project Narrative  Site Plan, including parcel and topography information Kennydale Lakeline Sewer System Replacement Project – Geotechnical Explorations May 2, 2024 www.confenv.com page 2 of 3 ACTIVITY DESCRIPTION The proposed work includes geotechnical exploration using borings to aid design of the project. There would be a total of five borings located along public property or the ROW along Lake Washington Boulevard North, details of the parcel and location are included in Table 1 below. The equipment, work area, access considerations, and duration of drilling for each boring location is described below. The proposed borings avoid work below the ordinary high water mark of Lake Washington (i.e., no in-water work). Exploration Parcel Location Surface Present B-1 King County Parcel Access Road Asphalt B-2 King County Parcel Access Road Asphalt B-3 City of Renton ROW City ROW near 3500 Burnett Ave N Asphalt B-4 City of Renton ROW Lake Washington Blvd Asphalt B-5 King County Parcel Mt. View Ave Parking Area Compacted Gravel Source: Shannon & Wilson 2024 Proposed geotechnical borings will be advanced using a track-mounted Acker Recon drill rig and mud-rotary drilling methods to a depth of 15 feet to 25 feet below ground surface. Soil samples will be obtained in conjunction with standard penetration tests at 2.5-foot intervals. Each boring will include an observation well for measuring groundwater depths. A vibrating wire piezometer will be installed at each boring location to monitor water levels continuously for the duration of the project. Additional details of the proposed geotechnical investigation are provided in the project narrative and Site Plan. Access Access to the boring locations will be through City of Renton or King County owned parcels or public ROW (Site Plan Fig. 2-6). Most staging areas will be at the same location as the borings. Due to the location of nearby residences, B-1 will likely be staged from the B-2 location. The boring will require a work area that is approximately 20 feet wide by 50 feet long (~1,000 square feet). Kennydale Lakeline Sewer System Replacement Project – Geotechnical Explorations May 2, 2024 www.confenv.com page 3 of 3 Construction Timing Geotechnical explorations will occur as soon as the permits are obtained. A King County Special Use Permit is concurrently under review. This work is anticipated to take approximately 2 days to complete. BEST MANAGEMENT PRACTICES The project narrative describes the best management practices that will be implemented to protect shoreline areas. REGULATORY EXEMPTION The proposed work is State Environmental Policy Act (SEPA) exempt under the Washington Administrative Code (WAC) 197-11-800 (17)—Information collection and research, and exempt from shoreline substantial development under WAC 173-27-040 (m)—site exploration and investigation. Please contact Marlene Meaders (Confluence Environmental Company) at 206-724-5781 or by email at marlene.meaders@confenv.com, or Joe Stowell (Renton Public Works) at 425-430-7212 or by email at JStowell@Rentonwa.gov if you require additional information or have any questions about this project. Respectfully yours, MARLENE MEADERS Principal Marine Biologist 206.724.5781 marlene.meaders@confenv.com