9900 19TH AVE SE WINCO FOODS 2025-03-27

JSACIVIL Engineering I planning I Management Technical Memorandum To: City of Everett From: Brandon Johnson, PE—JSA Civil, LLC Date: January 24, 2022 Subject Stormwater Flooding Documentation Project: WinCo Foods Store No. 104(Everett, WA) 1. INTRODUCTION: This memorandum has been prepared by JSA Civil (1SA) at the request of WinCo Foods (WinCo) and the City of Everett (City( to document the actions taken by WinCo to resolve the ongoing flooding issues at the intersection of 10& St SE and 16" Ave SE. 2. BACKGROUND: The site of WinCo foods was originally constructed as a Home Base in 1999. The construction included the filling of a wetland and creating a regional Stormwater system accepting approximately 10 acres of onsite runoff and 24 acres of upstream runoff. The system included two ponds, two pumps, a bypass system, and an ultimate discharge location at the northwest corner of the Home Base site. A brief description of each component is provided below: • Lower Pond: This pond is located at the Intersection of 16" Avenue SE and 100`h St SE and was constructed with the intent to detain and treat a portion of the upstream runoff which was previously discharged into the wetland filled by the Home Base construction. Upper Pond: This pond is located in the southwest corner of the WinCo (formerly Home Basel site and was constructed to detain and treat runoff from the WinCo site. This pond also provided additional treatment/detention for the runoff leaving the lower pond. • Pump Station No.1: This pump station was installed to allow the runoff from the Silver Lake Professional Center to enter into the Lower Pond for treatment/detention. Pump Station No. 2: This pump station was installed to lift the discharge from the lower pond into the upper pond for additional treatment/detention. JSA Civil, LLC -6945 Uttlerock Road SW Unit A - Tumwater, WA 98512