Brown and Caldwell Inc. 2/3/2022

Port Gardner Storage Facility Scope of Work 1-06-22 • Establish pretreatment(screening and grit) criteria. Remote at basin pretreatment will be evaluated strictly for the Sewer M basin. If remote pretreatment is the preferred option, the other drainage basins will need to incorporate the pretreatment in the design when the storm drainage infrastructure is developed. • Develop the stormwater treatment system configuration including stormwater conveyance, high flow bypass, pretreatment, equalization storage, biofiltration treatment, and influent and effluent pumping. • Develop stormwater treatment hydraulic profiles through the proposed stormwater treatment train considering tailwater conditions associated with pumping of treated stormwater flows to the deep-water outfall. • Prepare for and attend two design development coordination meetings with BC and the City, with the outcome being selection of a recommended stormwater improvements plan. • Prepare Stormwater Treatment Design Report documenting outcomes of the analysis and recommendations.The report will include the stormwater treatment system Basis of Design that may be incorporated in the overall PGSF Basis of Design under Task 320. This will provide a basis for estimating the construction and annual operating and maintenance (0&M) costs of the facility and a basis design. Task Assumptions • Field visit will be up to two days for 2 HDR stormwater staff and the HDR project manager. • Pretreatment screening options will be evaluated at the basin level and at PGSF. • The alternatives analysis will be limited to the evaluation of pretreatment options and the limits of the potential watershed. • The watershed area for the Port Gardner Stormwater Treatment Facility is based on the four basins in Figure 5-37 of the Conveyance Alternative Technical Memorandum (Appendix D) of the Port Gardner Storage Facility Engineering Report.These basins include Sewer M (131 Acres), Grand Ave Phase 1 (18 Ac), Grand Avenue Phase 2 (59 Acres)and Rucker Hill (100 Ac). • Biofiltration will be based on the GULD approved Filterra Bio-Scape technology. • HDR will summarize improvement component quantities and equipment needs (with vendor quotes as needed)for input to BC OPCC cost opinions development for the stormwater improvements • A draft and final version of the Stormwater Treatment Design Report(10 pages in length plus figures)will be prepared in response to a single BC and City review and comment iteration. • Design development coordination meetings will be 2 hours in duration and will be attended by 2 HDR stormwater staff and the HDR project manager. • The content from the technical memorandums will be incorporated into the Stormwater Treatment Design Report with review comments addressed. • The first coordination meeting will review the potential watershed,facility sizing and pretreatment options, and pretreatment options. • The second meeting will review the treatment system configuration and design development. • Final Stormwater Treatment Design Report will be provided with the 30% Design under Phase 350. 19