EPA to Present its Role in Preserving the Orange County Groundwater Basin on Dec. 16

Water consumers in north and central Orange County are served a blend of two types of water: groundwater provided by the Orange County Water District (OCWD; the District) and imported water from the Metropolitan Water District of Southern California (MWD). Though the amount varies, approximately 2/3 of the water demand is met from the large underground aquifers found in the Orange County Groundwater Basin that is managed by OCWD. While the District is typically known as a water supply agency, it has an equal role in providing high-quality water.

Orange County groundwater supplies have been strained by the four-year drought, ongoing threats of seawater intrusion and two contamination locations that could compromise the safety of the water that provides the needs for 2.4 million people. OCWD, through its Groundwater Replenishment System (GWRS), has been successfully managing the first two challenges.

One of OCWD’s most effective water quality protection projects is the Talbert Seawater Barrier operating in Fountain Valley and Huntington Beach. The barrier is a “picket-fence” configuration of 120 injection wells which are used to inject up to 40 million gallons per day of ultra-pure recycled water from the GWRS into the ground. The injected water creates a freshwater “wall” or barrier against seawater intrusion. The injected water far exceeds drinking water standards and is of nearly distilled water purity.

Because very little of the injected water flows to the ocean, the Talbert Barrier represents a major source of replenishment to the groundwater basin (part of the GWRS’ total of 100 million gallons of water each day recharged into the basin). This is in addition to its primary purpose of protecting the aquifer from seawater intrusion. Year-round operation of the barrier allows for continued pumping on its landward side during times of drought and for recovery during wet years, thus offering a sustainable and continuous water supply in the area by moderating the impacts of cyclical drought conditions.

Despite the groundwater basin’s overall exceptional quality, OCWD has identified two contamination hot spots that present an ongoing concern. One is in the northern part of the basin (near Fullerton, Anaheim and Placentia) where manufacturing industries operating primarily in the 1950s, 60s and 70s left a legacy of industrial pollutants at their former factories. The pollutants, mostly volatile organic compounds (VOCs) including solvents and degreasers, have migrated through the soils and are now leaching into the underlying groundwater. These VOCs have impacted nearby water supply wells causing five of them to be taken out of service. OCWD has characterized the extent of the problem and has been working toward a solution. Recently, the U.S. Environmental Protection Agency (USEPA), recognizing the need for early action, has taken over as the lead regulatory agency and has begun working through its formal Remedial Investigation and Feasibility Study (RI/FS) process, where additional remedies will be evaluated. Following the RI/FS process, interim and then final remedial action plans will be evaluated, selected and implemented. OCWD and select potentially responsible parties (PRPs) are engaged with the regulators and are working toward a long-term solution.

Removing extensive toxic substances involves united efforts with regulatory agencies. At the December 16 OCWD board meeting, representatives of the USEPA will present their role in resolving the contamination that exists in the northern section of the groundwater basin and their efforts to keep the community informed. The board meeting will begin at 5:30 p.m. in the OCWD board room.

The second hot spot of concern is referred to as the south basin area (near Santa Ana, Tustin and Irvine). It is also contaminated near the surface with VOCs similar to the northern area hot spot. In this area, the geology is different and the migration rates of the pollutants are a little slower. OCWD’s approach on this site is similar to the north basin location, and it, too, has been put forward as a top priority for groundwater remediation. As with the northern site, OCWD is performing a National Contingency Plan (NCP) compliant RI/FS. However, unlike the north basin site, the USEPA is not involved and the regulatory oversight is provided by the Department of Toxic Substance Control (DTSC) and the Regional Water Quality Control Board (RWQCB). These two state agencies are working closely with OCWD and some cooperative PRPs to map the occurrence of the contaminants, identify appropriate remedies and implement groundwater cleanup.

Although these two hot spots in OCWD’s jurisdiction have caused some local water wells to be shut down, they have not yet spread to a point where overall groundwater production within the affected cities has been reduced. The aggressive actions by OCWD and the environmental regulatory agencies are intended to reverse the problems and restore the two plume areas to their pre-industrial clean condition.

OCWD’s overall management of the Orange County Groundwater Basin has been commended by regulatory agencies and has served as a model throughout the state. Its efforts to save the basin from contamination are further examples of pioneering endeavors that could become standard operating procedures for others in the near future.