Groundwater Cleanup Update

North Basin Areas: Fullerton, Anaheim and Placentia
South Basin Areas: Irvine, Santa Ana and Tustin

After working closely with the US Environmental Protection Agency (EPA) for several months, the Orange County Water District (OCWD; the District) has entered into a formal agreement to perform a Remedial Investigation and Feasibility Study (RI/FS) for the North Basin groundwater cleanup project. The EPA has issued a press release regarding this project milestone. 

This agreement calls for OCWD to perform a detailed scope of work under EPA oversight. Upon completion of the prescribed investigatory work and analysis of cleanup options, the EPA will then select one of those options as a preferred interim remedy.  It is envisioned that the remedy will capture the most contaminated portion of the plume, cut off its continued spreading and begin to clean it up so that it no longer threatens the Orange County Groundwater Basin. 

Up until now, the District has pursued State Court litigation to compel the responsible parties to clean the contamination emanating from their sites, with very limited success. While some of the industrial dischargers have settled with the District and paid for remedial actions, many others have not, leaving much of the responsibility for cleanup unresolved.

This agreement is important because it will put in place a formal and scheduled plan to do the RI/FS work needed as a first step in the North Basin cleanup plan. The District’s work will provide the technical basis for beginning cleanup of the site and will establish a schedule for its implementation.  The final selection of an interim remedy and the apportionment of responsibility will be left to the EPA.

In addition to moving the project forward under EPA oversight, the District has also applied to the State Water Resources Control Board for grant funding support available from Proposition 1. OCWD’s priority is the protection of the groundwater basin.  This agreement facilitates the next steps toward meeting that interest.

After more than a decade of effort, the OCWD has also reached important milestones on the South Basin groundwater contamination area. Under two new oversight agreements, regulatory participation in the South Basin will involve the DTSC and the RWQCB without EPA involvement. While the mass of contaminant release in the South Basin is on par with the North Basin, the geology is different and likely will require a different cleanup approach.  In the North Basin, groundwater velocities are relatively high and the plume spreading has extended more than five miles laterally and several hundred feet deep.   In the South, the soil is more layered causing the contaminants to move more slowly laterally and with less of a downward velocity.

Even with the protective geology, the South Basin plume has still spread two miles long and one mile wide. In this area, the two state agencies will oversee both the source-site cleanups as well as the comingled downgradient plumes.  The recent agreements approved by the OCWD Board will continue the District’s ongoing RI/FS work for the comingled groundwater plumes and will reimburse the State agencies for their efforts to review and comment on the OCWD’s groundwater-related technical work products.

These new developments in both the North and South Basin areas bring together many formerly disparate elements. Work scopes are defined and tentatively agreed upon by the District and all three regulatory agencies; RI/FS work is proceeding in a systematic fashion; grant funding has been applied for in both areas; and active funding is provided by the District, and potentially from willing PRPs.  Hopefully the PRPs will see what is emerging as voluntary and cooperative remediation planning as a good alternative to continued litigation or possible Superfund listing.

OCWD staff will continue its commitment to regularly scheduled open session updates at Board meetings, regular publications in our newsletters and monthly updates to our groundwater producer meetings. In the meantime, if you have any questions, please do not hesitate to contact Bill Hunt at or (714) 378-8229.