2021/06/09 Council Agenda Packet

EXHIBIT A SCOPE OF SERVICES Background The existing 17th Street Interceptor is a major sewage pipeline that conveys wastewater from the Port Gardner Basin and portions of the north end of the City to the Water Pollution Control Facility (WPCF). System analysis of the existing pipeline performed as part of the Port Gardner Storage Facility (PGSF) project indicates that it has inadequate capacity to convey peak wet weather flows. Hydraulic modeling indicates that sections of the pipeline are subject to surcharging that could result in basement backups or surface discharges. Increasing the constricted sections of the pipeline may result in increasing the flow to downstream facilities including the Siphon Headworks and Diversion Structure Zero. This increase in flow could increase the frequency of combined sewer overflows (CSOs) at SRO 3. This in turn may drive the need to accelerate the Diversion Structure Zero improvements. The objective of this project is to determine from existing information or information that may be collected in the near future, the existing and projected loading on the existing interceptor, improvements to eliminate the potential overloading of the interceptor, and develop potential operating strategies for the pump stations within the Port Gardner Basin (Lift Station 4, Lift Station 5), PGSF and control structures associated with the Sewer M basin that could reduce, delay or eliminate other capital improvements. The anticipated phases of this project include: • Phase I: Planning and Predesign — Revise the hydraulic modeling of the sewer collection system to reflect information collected since the last sewer plan and incorporate Sewer M revisions. This will also incorporate the model revisions for the Port Gardner Basin. Develop conveyance improvements to eliminate the constrictions in the interceptor and develop collection system facility operating strategies to minimize other potential improvements. Design of the selected alternative will be developed to 30% design level. • Phase II: Final design - The scope and budget for this phase will be developed upon completion of Phase I. • Phase III: Construction — The scope and budget for this phase will be developed upon completion of Phase I. This first phase of this project will be to complete the planning process by identifying the proposed improvements and assessing downstream impacts to the downstream facilities including the Siphon Headworks and Diversion Structure Zero. The following tasks are included in this scope of work: Task 100 — Project Management Task 200 — Collection System Modeling Task 300 — Alternative Development Task 310 — Project Surveying Task 320 — Geotechnical Investigations Task 400 — Development of System Facility Operating Strategies City of Everett— 17th Street Interceptor Improvements 1 Scope of Services