North and South Basin Cleanup

After more than a decade of effort, the OCWD has reached important milestones on both the North Basin and the South Basin groundwater contamination areas.

On Wednesday, June 15, the OCWD Board of Directors authorized the District’s executive staff to finalize oversight agreements with the United State Environmental Protection Agency (EPA), the California Department of Toxic Substances Control Board (DTSC), and the Santa Ana Regional Water Quality Control Board (RWQCB).  These agreements include descriptions of the sites and the scope of work for the next phase of Remedial Investigations and Feasibility Studies (RI/FS) for both areas.  The Board has also approved a voluntary agreement between the District and a potentially responsible party (PRP) to collaborate and share costs on the performance of the RI/FS.

North Basin [Fullerton, Anaheim, & Placentia areas]

The EPA has taken the lead in overseeing the groundwater characterization and restoration in the North Basin.  In their arrangement with DTSC and the RWQCB the EPA will focus on the larger areas of the comingled plume while the DTSC and the RWQCB will focus on the source-site cleanup activities.  The OCWD’s role under this latest agreement will be to perform National Contingency Plan (NCP)-compliant groundwater studies under the EPA’s oversight.  District activities will therefore focus on the evaluation of alternatives for an interim groundwater remedy that will capture the comingled plume as it emerges from the many source sites and thus prevent its continual leaching into the clean water downgradient of the former and active industrial sites.  The two state agencies will work closely with the potentially responsible parties to accomplish their on-site remediation work.

As a parallel initiative, one of the PRPs has been working closely with the District on a voluntary basis to get this RI/FS work done.  They have offered technical and financial support to the District in advance of the latest EPA agreement.  Their offer to collaborate has encouraged the OCWD Board and is seen as an important element of completing the prescribed work in a direct and cost effective way.  It is hoped that the voluntary cooperation between the District and this PRP will encourage other potentially responsible parties to also join in and to work toward the implementation of a remedy for the benefit of all parties and for the groundwater resource itself.

South Basin [Irvine, Santa Ana, & Tustin areas]

Under these latest 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 affect the 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 slowly laterally and with less of a downward vector.   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 NCP-compliant RI/FS work for the comingled groundwater plumes and will reimburse the State agencies for their efforts to review and comment on the groundwater-related technical work products.  Their source-site regulatory activities will proceed without financial contribution by the OCWD.

Next Steps

These new developments in both the North and South basin areas bring to 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 and NCP-compliant fashion; grant funding has been applied for in both areas; active funding is provided by the District, the agencies, and willing PRPs.  The willing cooperation of the willing PRP and the OCWD serves as a model for fast, efficient and cost effective remediation activities.  Hopefully other PRPs will see what is emerging as voluntary and cooperative remediation planning as a good alternative to possible Superfund listing or continued litigation.