No Quarantine for Cooperation – Reasonable Assurance Analysis for Stormwater Management Planning in the Santa Clara Valley

Date / Time:
Wednesday, Sep 16 4:30pm to 5:00pm
Track / Session:
Track: Data Management, GIS / GIS Tools, and Modeling / Session 9

The Santa Clara Valley Urban Runoff Pollution Prevention Program (SCVURPPP) performed a two-phased study to support municipalities in Santa Clara County with stormwater management planning to address requirements of the Municipal Regional Stormwater Permit. The first phase quantified baseline existing condition hydrology and loadings of Polychlorinated Biphenyls (PCBs) and mercury to San Francisco Bay. The second phase included a Reasonable Assurance Analysis (RAA) to evaluate the costs and benefits of different Green Stormwater Infrastructure (GSI) planning alternatives for attaining TMDL goals. A key aspect of this study was to quantify load reductions associated with (1) existing GSI, (2) GSI within areas projected for future redevelopment, and (3) potential future site-scale and regional GSI projects. The analysis highlighted economies of scale opportunities among many of the planned multi-jurisdictional regional projects, where municipalities could collaborate and save costs by implementing projects across municipal boundaries , compared to a “quarantined” approach of implementing smaller projects within their own jurisdictional boundaries.

The baseline watershed model of the existing condition was used to establish pollutant load reduction targets for this analysis. It was calibrated and validated using historic monitoring data. The cost-benefit optimization model was run iteratively to generate cost-effectiveness curves representing different combinations of GSI projects within each municipal jurisdiction. The model results were used to establish goals for GSI implementation by evaluating the trade-offs between different scenarios.

A unique aspect of this RAA was how the outputs considered perspectives of multiple stakeholder, while balancing an appropriate level of detail and specificity and preserving ample opportunity for future adaptive management of the plan. In this presentation, the speakers will provide an overview of the modeling approach and scenario results, and engage the audience to demonstrate how the RAA outputs can communicate essential actionable and trackable information to the various stakeholders. The presentation will demonstrate that where there is cooperation among jurisdictions and stakeholders, outputs from these types of analyses provide a useful framework for communicating, planning, and cost-sharing implementation of the most cost-effective management scenarios.

Primary Speaker:
Chris Sommers, EOA, Inc.

Chris has over 20 years of experience in developing and implementing pollutant of concern (POC) source identification and stormwater management projects/programs. Chris advises various government agencies on all aspects of federal, state and local regulations associated with stormwater management and has served as advisor and project manager on a number of stormwater pollutant control programs and ecological monitoring and management projects/programs in California. Chris currently serves as the coordinator for the Santa Clara Valley Urban Runoff Pollution Prevention Program’s (SCVURPPP) Watershed Monitoring and Assessment Program and managed the development of SCVURPPP’s Reasonable Assurance Analysis (RAA) for PCBs and mercury.

Supporting Speaker 1:
Steve Carter, Paradigm Environmental

Steve Carter is a principal engineer and Director of Paradigm Environmental, and has 20 years of experience supporting municipal, state, and federal agencies in watershed and pollutant loading analyses and the planning and implementation of stormwater management practices. Steve was the primary author of the Santa Clara Valley Urban Runoff Pollution Prevention Program (SCVURPPP) Green Stormwater Infrastructure Reasonable Assurance Analysis (RAA) for PCBs and Mercury.