Frequently asked questions
The Groundwater Replenishment System (GWRS) is the world’s largest advanced water purification system for potable reuse. The GWRS takes highly treated wastewater that would have normally been discharged into the Pacific Ocean and purifies it using a three-step advanced treatment process consisting of microfiltration, reverse osmosis and ultraviolet light with hydrogen peroxide. The GWRS produces up to 100 million gallons (379,000 cubic meters) per day of high-quality water that exceeds all state and federal drinking water standards for nearly 850,000 residents in north and central Orange County.
In the mid-1990s, the Orange County Sanitation District (OC San) faced the possibility of having to build a second ocean outfall that would have cost approximately $200 million. At the same time, the Orange County Water District (OCWD) was faced with continued problems of seawater intrusion and the need to expand its Water Factory 21 (WF 21) from 22.6 million gallons (85,600 cubic meters) per day to 35 million gallons (132,500 cubic meters) per day.
At the time, California had just experienced a severe drought. Water experts also projected droughts would occur three out of every 10 years, that there would be increases in demand due to population growth, and that the demand and cost of imported supplies would increase in the near future. Faced with these future challenges, OCWD built upon its long-history of successfully treating wastewater at WF 21 for its seawater barrier and decided to implement advanced processes to purify the wastewater and send it to recharge basins, where it would ultimately become part of north and central Orange County’s drinking water supply.
The GWRS can produce up to 100 million gallons (379,000 cubic meters) of water per day of near-distilled, high-quality water. That is enough to meet the needs of nearly 850,000 residents in north and central Orange County. After its final expansion is complete, production will increase to up to 130 million gallons of water per day.
After more than ten years of planning and construction, the GWRS came on-line in January 2008. By October 2010, it had already produced more than 50 billion gallons (189 million cubic meters) of new, high-quality water.
The capital cost to build the GWRS was $481 million (U.S. Dollars) and was funded through $92.8 million in local, state and federal grants. Funding included $37 million from the State Water Bond (Proposition 13) approved by California voters in 2000, $30 million from the California Department of Water Resources, $5 million from the State Water Resources Control Board awarded in 2002, $20 million from the United States Bureau of Reclamation’s Title XVI program, $300,000 from the California Energy Commission, and $500,000 from the Environmental Protection Agency. OCWD and OCSD cost shared the remaining $388 million.
The GWRS initial expansion, completed in 2015, cost $142 million.
It costs approximately $40 million a year to operate the GWRS. Roughly $15 million is for power alone; however, it is important to note that the GWRS water can be produced using half the energy required to pump imported water from Northern California to Orange County. Other maintenance costs include $6 million for chemicals, $7 million for membrane and ultraviolet lamp replacement and $10 million for operating and management (O&M) staffing. The Metropolitan Water District of Southern California (Met; MWD), the importer of water for all of Southern California, subsidizes $7.5 million annually (for 12 years) to help operate the facility because it creates significant amounts of new water and helps to alleviate demand from fragile and unreliable imported water supplies that MWD is responsible for delivering to Southern California.