Brown and Caldwell, Inc. 9/27/2023 Amendment 1

Amendment 1 PSA with Brown and Caldwell for Port Gardner Storage Facility Project Exhibit A Scope of Work 23 Work Products • See individual subconsultants work products. Phase 420 – Hydrologic & Hydraulic Modeling Objective: Inform design advancement and operational strategy of PGSF components including new additions such as LS 46 using the existing hydraulic model. Activities/Approach: This task includes the following activities: • Model updates to support task activities. − Incorporate Conveyance Package D when HDR advances it to 30% design. − Refine pipe diameters and alignments of Package ACE to be physically based within model given preliminary understanding. Update at ACE 30% Design. − Refine PGSF major components (basins, pumping, inlet structure, etc.) within the model per refined facility design for both storm and sewer. • Determine stormwater peak flow management strategy and conveyance criteria. − Determine isolation point and automation strategy for peak flow diversion. Model up to 3 scenarios and develop performance assessment of each scenario to inform decision making. − Determine detailed hydraulic criteria for conveyance alignments for preferred scenario. − Develop meeting materials PowerPoint to facilitate decision making within a meeting. − Develop brief TM summarizing modeling analysis and design recommendations. • Support design criteria for LS46 using a regional hydraulic capacity and operations-based modeling approach. − Remove LSX/LS6 from model, replace with LS46 concept. − Model effects of intended LS46 operation on downstream system, determine hydraulic impacts of increased pumping. − Identify acceptable capacity and operational strategy to minimize regional impacts. − Refine operational strategy for LS46 in concert with LS3 for PGSF dewatering. − Develop brief TM summarizing modeling analysis and design recommendations. • Plan for maintenance and failure models of regional system and incorporate into PGSF design. − Define failure mode scenarios at PGSF and of major components and facilities draining to PGSF. − Model scenarios to determine potential impacts to PGSF, required response times, and necessary responses to minimize impacts. − Define maintenance modes at PGSF and of major components and facilities draining to PGSF. Model scenarios to determine flow management strategies by maintenance. − Determine design criteria for PGSF and suggested design criteria for the ACE conveyance package. − Lead meeting to finalize selected maintenance and failure modes. − Lead meeting to review maintenance and failure mode analysis. − Develop TM summarizing modes, analysis, and design criteria.