Protecting Local Groundwater Supplies

The Orange County Water District (District; OCWD) continues to work toward remediating both the North­ Basin and South Basin groundwater contaminant plumes to protect our local drinking water supplies.  Both the North and South projects are being implemented with similar parallel approaches: technical work to develop a cost-effective remedy and efforts to get the parties responsible for the contamination (responsible parties; RPs) to pay for the remediation, rather than place that burden on the water ratepayers. The status of the technical analysis and cleanup in both areas is mixed. Driven primarily by state regulatory enforcement, the RPs have primarily conducted on-site studies and soil remediation. Very little groundwater remediation has been conducted, particularly off site. The RPs have not taken on the comprehensive assessment of the large comingled and multi-mile long plumes that extend far beyond their property boundaries. It is this off-site contamination that is the emphasis of OCWD’s technical work. Time is of the essence, because this contamination has impacted several water supply wells, and is moving and threatens to impact additional wells.

North Basin [Fullerton, Anaheim, and Placentia areas]

For the North Basin project, the District’s Board of Directors (Board) has authorized staff to enter into an agreement with the United States Environmental Protection Agency (EPA).  In that agreement, the District will cooperatively perform a remedial investigation and feasibility study (RI/FS) under EPA oversight. The agreement includes the installation of 14 additional monitoring wells (OCWD has already installed 70 in the area). These new wells will fill in data gaps regarding the hydrogeology and the vertical and lateral extent of the contaminant plumes.  Some of these wells will also be useful after the implementation of a remedy for the long-term monitoring of the cleanup efforts. OCWD is currently working on securing access and permits to install the new monitoring wells.  Drill rigs and supporting equipment are expected to be deployed in late spring or early summer. The data from the RI will support the FS. The FS will develop and evaluate cost-effective interim remedial alternatives to contain the most contaminated parts of the plumes. Following completion of the FS, an interim remedy will be proposed and public input and comment will be solicited. After a 30-day public review and comment period, the interim remedy will be selected by the EPA.  It is expected that the RI/FS and selection of an interim remedy will be completed in late 2018.

While the RI/FS studies proceed, the plume continues to spread. While only drinking water that meets state and federal standards is provided to Orange County, an area of the plume in the eastern project area has been identified as a particularly worrisome source of shallow groundwater contamination spreading deeper into parts of the aquifer used for potable water supplies. Consequently, early action has been deemed necessary by OCWD’s Board. In response, the District’s engineers and geologists are currently equipping a well that will pump 1,000 gallons per minute specifically to contain groundwater contamination in that area. That well, referred to as EW-1, is located near the intersection of State College Boulevard and Valencia Drive in Fullerton. Installation of this well, paid for by one of the cooperative RPs and OCWD, is expected to be in operation before the end of 2017.  

The RI/FS work is being performed in conformance with the National Contingency Plan (NCP), federal regulations that will allow for both EPA enforcement against the RPs, and future cost recovery by OCWD. As always, the District’s priority in the North Basin is to cost-effectively remediate the groundwater contamination, protect the aquifers used for drinking water supply, and pursue financial contribution from the parties responsible for the contamination. 

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

The South Basin RI/FS, also approved by the District Board, is proceeding with the installation of 24 additional monitoring wells in the southern part of the South Basin area. As with the North Basin Project, many sources in the South Basin area are regulated by the state and have produced considerable information concerning impacts to groundwater from industrial chemicals. What has not happened is the delineation and remediation of the larger plumes that emanate from multiple sources and comingle downgradient from the RP sites. It is this off-site contamination that is the focus of OCWD. OCWD is determined to ensure that impacts to groundwater are controlled and that the drinking water supplies are protected for the benefit of water producers and consumers of the Orange County Groundwater Basin. 

The well drilling rigs may be deployed on this project as early as April. As with the North Basin Project, the results of the South Basin RI (also NCP compliant) will feed into a South Basin FS and the selection of one or more interim remedies intended to control the spreading of contamination and thereby protecting the underlying water supply. This NCP compliant RI/FS will allow for future cost recovery against those responsible for causing the problem.


The District is currently funding the RI/FS work for the North and South Basin areas from its general fund and capital reserves. To help relieve some of the financial burden on ratepayers, the District has applied to the State Water Resources Control Board’s recently enacted Proposition 1 grant funding program. Three matching funds applications have been submitted; two for RI/FS planning studies and one for the construction of the initial pumping system in the North Basin. Notice of funding approval is expected soon.