Development of New Statewide Guidance on Drywell Siting, Design, and Implementation
The State Water Resources Control Board (SWRCB) is working with Geosyntec Consultants to develop statewide guidance for the siting, design, and implementation of drywells. Municipalities, developers, and commercial/industrial operators are increasingly turning to drywells as a cost-effective stormwater best management practice in order to protect downstream surface water quality, while also providing water supply benefit. In addition, drywells are a convenient solution when space is limited due to their small footprint and because they provide opportunities to infiltrate in deeper permeable soil layers when the surface infiltration may be limited. While these benefits are evident clear statewide guidance on how to safely implement drywells in order to protect groundwater quality and public health is lacking. The SWRCB and Geosyntec, along with a technical advisory committee (TAC) including industry, municipality, and institutional stormwater and groundwater practitioners, are beginning a study to evaluate what existing guidance exists, synthesize available water quality data, and identify modeling or data needs to understand how to safely implement drywells throughout California.
The purpose of this presentation will be to provide an overview of the project, including the findings of our initial research and other progress, as well as a summary of work under development and potential future planning efforts. The framework of this guidance is still being developed but may include: groundwater quality protection (including applicable standards and points of compliance), spill containment, clogging reduction, pretreatment selection (based on the preceding three factors), geotechnical risk avoidance, groundwater mounding characterization and impacts, infiltration rate estimation and sizing, existing soil or groundwater contamination, permitting, construction, monitoring and other aspects. According to the SWRCB and TAC priorities, contaminate fate and transport modeling, hydrogeology and geochemical condition evaluations to understand plume migration, and pollutant vadose zone modeling may be reviewed or performed to inform the final guidance.
The presenters may also identify potential options for the SWRCB to integrate this technical guidance into new or existing policy, general permits, or other regulations.
The audience will be invited to participate through a Q&A session to clarify how this guidance may relate to their past, ongoing, or future drywell projects. This presentation is directly related to the conference’s theme of “Summit to Sea” as it is outlining guidance for a cost-effective tool capable of capturing and infiltrating stormwater runoff from upland watersheds, thus reducing pollutant discharges to downstream receiving water bodies, while also replenishing groundwater aquifers.