HDR Engineering Inc. 10/6/2022 - Laserfiche WebLink

Exhibit A FY EXHIBIT A SCOPE OF SERVICES Background and Summary Combined Sewer Overflows (CSOs) contribute to the degradation of water quality in the Snohomish River (River), and water quality treatment is essential to the recovery of Endangered Species Act (ESA)-listed salmonid species and Resident Puget Sound Killer whales, to the continued support of beneficial uses of Waters of the State and is required by the MS4 National Pollutant Discharge Elimination System (NPDES) discharge permit. To address this, the City of Everett (City) has been working to eliminate CSOs within their stormwater drainage basins. The proposed Lexington Avenue Storm Drainage Improvements would replace undersized sections of the stormwater trunk line conveyance system within subbasins LW-9, LW-10, and LW-11 of the Lowell Basin Plan, and would route the drainage from the three basins to a new stormwater treatment facility and then through a new discharge (outfall) to the Snohomish River. Project improvements include: • Construction of a stormwater conveyance system to separate 85 acres of basin area that is tributary to the existing CSO system, reducing the hydraulic loading on the CSO system and lowering the frequency and severity of overflow events. • Construction of a regional stormwater treatment facility to provide water quality treatment. • Stormwater conveyance piping from the stormwater treatment facility with a new stormwater outfall to the Snohomish River. Much of the 231 acres within these subbasins (including the 85 acres of the CSO basin) is occupied by pollutant-generating impervious surfaces from which stormwater runoff presently receives little runoff treatment. In addition to stormwater conveyance improvements, this project will provide treatment of the stormwater prior to its discharge to the River. Stormwater treatment will be provided via an engineered enhanced water quality treatment facility with media treatment cells, treating the initial flows according to the City stormwater manual criteria. Following treatment, stormwater would be discharged directly to the River through a new stormwater outfall. This project also includes environmental permitting (to include the development of an Inadvertent Discovery Plan) necessary for construction and implementation of the proposed Storm Drainage Improvements. A later phase of this project will include regulatory coordination services, final design, and construction support. The project schedule, by task, is illustrated below (Table 1), along with the necessary budget for task completion. All tasks will be completed by May 15, 2023, as the present grant period expires June 30, 2023, unless otherwise approved by the city. Lexington Avenue Storm Drainage Improvements Preliminary Design Scope of Services 1