State Water Resources Control Board holds workshop on draft urban stormwater infiltration policy

State Water Resources Control Board staff held a public webinar to solicit feedback on a proposed statewide urban stormwater infiltration policy, outlining a framework that would guide where and how stormwater may be infiltrated to benefit groundwater recharge while protecting groundwater quality.

Board staff said the policy is still in early development and will be refined through outreach and public comment; written comments are due to stormswaterboards.ca.gov by 12 noon on Feb. 24. Staff said they plan continued engagement over the next eight months before issuing formal policy language and that implementation would likely occur through MS4 permits rather than creating a new Waste Discharge Requirement (WDR) or separate statewide permit.

Staff described three central aims of the project: provide consistent statewide standards for infiltration, clarify where infiltration is and is not appropriate, and reduce regulatory confusion that currently discourages some permittees from installing infiltration systems. A staff member said, "We don't want to require that stormwater meet MCL before it gets infiltrated," and emphasized the team is studying vadose-zone (soil) attenuation and where pretreatment or monitoring will be necessary.

Key provisions discussed included a tiered risk system that would assign lower requirements to…