Reasonable Assurance Analysis: Guidance and Source Control Load Reduction Accounting
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Bay Area Municipal Regional Permit (MRP) Provision C.3.j required the Permittees to develop a Green Infrastructure (GI) Plan for inclusion in their Annual Report.

MRP Provisions C.11.c and C.12.c require the Permittees to prepare a Reasonable Assurance Analysis (RAA) for inclusion in the their Annual Report that quantitatively demonstrates that mercury load reductions of at least 10 kg/yr and PCBs load reductions of at least 3 kg/yr will be achieved by 2040 through implementation of GI throughout the MRP area. Additionally, MRP Provisions C.11.d. and C.12.d. require the Permittees to prepare plans and schedules for mercury and PCBs control measure implementation and an RAA demonstrating that those control measures will be sufficient to attain the mercury total maximum daily load (TMDL) wasteload allocations by 2028 and the PCBs TMDL wasteload allocations by 2030. The objective of these two Bay Area Stormwater Management Agencies Association (BASMAA) regional projects was to support the development of a regional framework and guidance for conducting PCBs and mercury RAAs in the Bay Area for GI as well as source control measures.

Geosyntec's Scope of Services

Geosyntec led the development of the Bay Area RAA Guidance Document which established the regional framework for conducting RAAs in the Bay Area. The guidance document identifies viable RAA technical approach options that are capable of demonstrating compliance with the MRP load reduction requirements and can reliably quantify the anticipated effectiveness of the types of control measures that may be implemented by the Permittees; reflects the current understanding of the distribution, fate, and transport of PCBs and mercury in stormwater runoff in the Bay Area; incorporates the appropriate level of accuracy and precision given the levels of uncertainty and variability in the data, assumptions, and TMDL load estimations and required reductions; and considers modeling methods that are only as complex as necessary, yet incorporate sufficient analytical rigor, while meeting MRP requirements and Regional Water Board staff expectations and withstanding the peer review validation process.

The Source Control Load Reduction Accounting for RAA report refines and expands the source control accounting methodology used during the MRP 2 permit term. The source control measures and load reduction accounting methodologies considered in the report include Source Properties; Trash Full Capture Systems; PCBs in Building Materials; PCBs in Electrical Utilities; PCBs in Roadway and Storm Drain Infrastructure; Enhanced Operations and Maintenance Control Measures; Pump Station Diversion; and Mercury Load Avoidance and Reduction. Technical approaches are based on PCBs and mercury data collected throughout the Bay Area spanning several years. 

Notable Accomplishments

Geosyntec successfully managed these projects, which involved coordination with multiple municipalities, stakeholders and regulators and include a wide array of pollutant load reduction estimation and computational methods that are understandable yet rigorous, to deliver high-quality technical approaches within a short timeline and modest budget.

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Project Summary

  • Location: San Francisco Bay Area, California
  • Client: Bay Area Stormwater Management Agencies Association (BASMAA)
  • Project Practice Areas: Water & Wastewater, Environmental Management, Water and Natural Resources
  • Type of Facility: MS4 Programs
  • Services Provided: Reasonable Assurance Analysis, MS4 Permit Compliance Guidance, PCBs and Mercury TMDL Implementation Planning, Source Control Load Reduction Accounting
  • Type of Work: TMDL implementation
  • Governing Regulation: Clean Water Act