The OCWD/OCSD Partnership

How It Began More Than Four Decades Ago

When there is extensive pumping of the Orange County groundwater basin, the basin becomes vulnerable to seawater intrusion. In the 1950s, traces of salt water were detected in the basin as far as five miles inland. The area of intrusion was focused primarily across a three-mile stretch between the cities of Newport Beach and Huntington Beach. This vulnerable area is associated with a subsurface geological feature referred to as the Talbert Gap (the gap). The gap is the mouth of an alluvial fan formed millions of years ago by sediment deposited by the flowing waters of the Santa Ana River.

In 1976, to protect the basin from further seawater intrusion, the Orange County Water District (OCWD) initially constructed the internationally known Water Factory 21 (WF-21). This precursor facility to the GWRS treated wastewater utilizing a state-of-the-art purification process, which included reverse osmosis, and injected it into 23 multi-casing injection wells along the Talbert Gap. Injection in these wells formed a hydraulic barrier to seawater intrusion. This mound of fresh water near the coast allowed for seasonal fluctuations in the aquifers landward of the barrier without the risk of seawater intrusion and its associated salt water contamination.

WF-21 was a world-renowned, and first-of-its-kind, water recycling facility that helped pave the way for many international projects and ultimately the Groundwater Replenishment System (GWRS).

The Partnership Today - Stronger Than Ever

In the mid-1990s, OCSD faced the possibility of having to build a second ocean outfall that would have cost approximately $200 million. At the same time, OCWD was faced with continued problems of seawater intrusion and the need to expand its WF-21 from 22.6 million gallons (85,600 cubic meters) per day to 35 million gallons (132,500 cubic meters) per day. Building upon their long-standing partnership, the two public agencies collaborated once again, this time to develop and construct the GWRS.

Under a joint cooperative agreement, OCSD agreed to supply OCWD with 96 million gallons (363,400 cubic meters) per day of secondary treated wastewater, without cost, to OCWD. OCSD committed to maintaining a stringent source control program to keep potentially harmful contaminants out of the treated wastewater before it was supplied to the GWRS. OCSD and OCWD also agreed to share the cost to construct the GWRS, which was $481 million (U.S. Dollars). OCWD agreed to manage and fund the operations of the facility into the future.

WF-21 discontinued production in 2004 and was demolished in February 2007 to make way for the GWRS. The new generation facility was built to be bigger and better than its predecessor. The GWRS consists primarily of membrane processes, replacing the physical-chemical processes of WF-21.  The GWRS is built to produce 70 million gallons (265,000 cubic meters; 215 acre-feet) of recycled water per day and a total production of 23.5 billion gallons (89 million cubic meters; 72,000 acre-feet) per year. Unlike WF-21, the GWRS utilizes microfiltration as pre-treatment prior to reverse osmosis and ultraviolet light with hydrogen peroxide. (For more information regarding the processes, please visit The Process section of the GWRS website.) The GWRS product water not only supplies water to an expanded seawater barrier, but is also pumped to two of OCWD’s recharge basins where it blends with Santa Ana River and imported waters and naturally filters into the groundwater basin, ultimately becoming part of north and central Orange County’s drinking water supply.

Together, the two agencies developed and implemented an aggressive education outreach program to build upon the public’s trust and earn overwhelming support for this unprecedented water recycling project. They were also very successful in securing $92 million in state, federal and local grants to help fund the project. In addition, the GWRS also receives a $7.5 million annual subsidy for 12 years from the Metropolitan Water District of Southern California.

Construction of the GWRS broke ground in September 2004 and was completed in late 2007. On January 10, 2008, the GWRS received approval from the California Department of Public Health and the Santa Ana Regional Water Quality Control Board to inject half of the GWRS product water into its seawater intrusion barrier. January 18, 2008 marked another important milestone as the project received final approval to send the other half of its product water to OCWD’s spreading basins in Anaheim to replenish groundwater supplies. The introduction of this ultra-pure water into these locations assures both a protection against seawater intrusion as well an uninterruptible and continuous groundwater recharge supply.

The cooperation between OCWD and OCSD was essential in designing and building the GWRS, which ensures north and central Orange County’s water supplies remain reliable and safe.  OCWD has already completed the design to expand the project from 70 million gallons (265,000 cubic meters) per day to 100 million gallons (378,500 cubic meters; 306 acre-feet) per day. The two agencies will undoubtedly continue to work together to make history in the world of water.