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<br />April 2022 Page 1 of 35 Jacobs Engineering Group <br /> <br />Exhibit A <br /> <br />Amendment No. 1 <br />Detailed Design & Bidding Period Support Services <br /> <br />--------------------- <br />City of Everett <br />SCOPE OF SERVICES <br />CSO Storage at 36th ST, UP 3765 <br /> <br />--------------------- <br />Jacobs Engineering Group <br />April 2022 <br /> <br /> <br />1. PROJECT UNDERSTANDING <br /> <br />Two separate planning and design efforts are in progress that involve combined sewer infrastructure <br />improvements to reduce combined sewer overflow (CSO) discharges at NPDES permitted outfalls SRO7 <br />and SRO8 to comply with the Department of Ecology (DOE) requirement of no more than one CSO event <br />per year per outfall averaged over a moving 20-year period. These projects also aim to eliminate chronic <br />sanitary sewer overflow (SSO) events at various locations. Another consultant (BHC) previously <br />completed a modeling study in 2020 that identified several improvements (grey infrastructure) that <br />would achieve CSO and SSO control. Sewer flow meters were installed in the system to support model <br />calibration and validation. The City plans to implement the following two project elements: <br /> <br />CSO Storage <br />Preliminary modeling with CSO storage showed that excess volume can be stored and slowly released <br />over time and is effective in reducing CSOs at SRO8 and flooding at various locations within the project <br />area. Exact dimensions of the vault (or other storage structure), orifice, and weir will be finalized during <br />design and may be impacted by other site constraints. <br /> <br />Modifications to 36th Street Regulator <br />Modeling indicates that diverting more flow from the 36th Street regulator to the Snohomish River CSO <br />Interceptor (SRI) will decrease flooding at City sewer manholes in the vicinity of this CSO control project <br />by reducing flow in the Summit Interceptor and flattening the hydraulic grade line (HGL). Modifications <br />to the 36th Street Regulator to accommodate CSO storage will need to be coordinated with Phase II of <br />the Sewer O projects (being completed by City staff), which will also divert more flow to the 36th Street <br />Regulator. The Sewer O projects seek to control SSO events at various locations. Modeling for Sewer O <br />determined that the proposed improvements would move an SSO problem farther downstream and <br />that additional system improvements are necessary. The City’s immediate objective is to ensure that