California’s State Water Resources Control Board is developing the new Statewide Urban Stormwater Infiltration Policy that will contain a risk-based framework for urban infiltration projects. A draft of the policy is anticipated in the Fall 2025 that intends to provide clear, science-based direction on urban stormwater infiltration best practices while protecting groundwater quality and beneficial uses.
Stormwater management agencies are prioritizing stormwater capture and groundwater recharge as a method of increasing water supplies. However, there are regulatory inconsistencies in current permits and local ordinances that result in confusion about where, when, and how to implement stormwater infiltration projects. Municipal agencies are recognizing potential liabilities with their infiltration projects as existing regulations are often not integrated into larger basin recharge programs. The current lack of a cohesive regulatory framework and clarity about water quality objectives are obstacles to wide-scale implementation of safe stormwater capture and use.
The Urban Stormwater Infiltration Policy will propose a risk-based framework that will take into consideration existing site conditions such as soil characteristics, geology and geotechnical information, expected pollutants based on land use, and pretreatment system selection and design criteria. The Policy intends to set a minimum vertical distance between the bottom of the infiltration system (e.g. drywells) and groundwater; and minimum distances between infiltration systems and drinking water wells, septic tanks, and contaminated sites to protect drinking water quality.
The Policy presents new development and construction considerations where stormwater runoff must be managed. In areas with medium-risk land use types, such as commercial areas or strip malls, pretreatment may be required to ensure the stormwater is safe to infiltrate. In some high-risk cases, infiltration systems will be prohibited in locations with certain types of industrial activities, contaminated soil, or with existing groundwater contamination.
The State Water Board is posting updates and new information on public workshops on its website. Urban Stormwater Infiltration Policy | California State Water Resources Control Board.
EEC Environmental is assisting municipal, commercial and industrial clients throughout California address their water infiltration and stormwater management challenges, and we’re prepared to discuss how the new policy may impact you. If you have any questions concerning these or any other related issues, please contact EEC’s team of professionals at (714) 667-2300.
Bill O’Braitis, Sr. Project Geologist, bobraitis@eecenv.com
Will Shaffer, Sr. Project Engineer, wshaffer@eecenv.com
