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City of Everett Coordination of SRO7 and SRO8 CSO Control and Sewer"0"'Project <br /> Assumptions <br /> 1. Only the Sewer 0 model provided by the City will be calibrated. This model includes <br /> portions of Basins N and NG, and downstream piping. <br /> 2. The Master Model will not be updated. <br /> 3. Small diameter tributary pipes will not be checked for accuracy or completeness. <br /> Deliverables <br /> 1. Calibrated Sewer 0 model. <br /> 2. Summary Technical memorandum detailing calibration methods and results (PDF file via <br /> email). <br /> Task 400 — Hydraulic Analysis/Modeling <br /> Objectives <br /> This modeling effort shall coordinate the CSO/SSO Reduction Projects so that the resulting <br /> combined and coordinated improvements will most efficiently eliminate SSOs and reduce CSOs <br /> to sufficiently control CSOs discharges within the study area. This task will review the impacts of <br /> the CSO/SSO Reduction Projects on both street flooding and CSO compliance at hydraulically <br /> connected outfalls and analyze alternatives to mitigate these impacts. <br /> This task will identify a recommended alternative for pre-design and establish design sizing for <br /> the recommended alternative. <br /> This task will be broken out into two subtasks. Subtask 1.1 will include all grant-eligible work, <br /> such as modeling of alternatives to reduce CSOs. Subtask 1.2 will include all non-grant-eligible <br /> work, such as conveyance sizing. <br /> BHC Services <br /> 1. Hydraulic Modeling. <br /> a. Use Sewer 0 model calibrated in Task 300 to create a baseline model to <br /> compare with results from analysis models. Add boundary conditions associated <br /> with long term simulation rainfall time series as necessary to account for all flows <br /> into the system. Multiple baseline models with different rainfall time series and <br /> boundary conditions may be created as needed if various rainfall time series are <br /> used. <br /> b. Analyze 8-12 scenarios to reduce CSOs and SSOs. Initial modeling will be done <br /> using a design storm to approximate CSO compliance in order to more efficiently <br /> iterate configurations and sizing. Final modeling will use a long term simulation to <br /> more accurately determine CSO compliance and fine tune sizing and elevations. <br /> Depending on the scenario, existing, 2055, or 2085 rainfall time series will be <br /> used. Model scenarios will include various combinations of the following projects: <br /> • Sewer 0 Phase 1 Improvements <br /> • Sewer 0 Phase 2 Improvements <br /> • Constructing CSO storage in the vicinity of 36th Street regulator <br /> • Modifying the weir elevation in 36th Street regulator <br /> • Constructing a 48" overflow pipe from Pine Street regulator to the 72 inch <br /> SRI (as defined in the Comprehensive Sewer Plan). <br /> • Modifying the Pine Street regulator weir or upsizing connecting pipes. <br /> ■ <br /> Scope of Services 5 • C&I <br /> CONSULTANTS <br />