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 130 million gallons per day of high-quality water that exceeds all state and federal drinking water standards for nearly one million 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).
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 130 million gallons of water per day of high-quality water. That is enough to meet the needs of nearly one million residents in north and central Orange County.
The GWRS came online in January 2008, producing 70 million gallons of water a day, enough for 600,000 people. It was expanded in May 2015, producing 100 million gallons of water a day, enough for 850,000 people. The final expansion, completed in 2023, increased production capacity to 130 million gallons of water a day, enough for one million people.
Total project costs for the Groundwater Replenishment System including all expansions are more than $900 million. The project came online in January 2008 at a cost of $481 million. It expanded in May 2015 at a cost of $142 million. A second and final expansion, completed in 2023, cost $284 million. Several grants and low-interest rate loans were received over the years by many state and federal agencies. See breakdown for each phase below.
Construction cost: $481 million
- Annual Local Resources Program (LRP) operational subsidy of $121 per acre-foot over 23 years that amounted to $86.2 million. The LRP subsidy was provided and administered by the Metropolitan Water District of Southern California (MWD).
- $67 million grants from the 2000 California State Water Bond including $37 million from the State Water Resources Control Board (SWRCB) and $30 million from the Department of Water Resources (DWR)
- $5 million from the SWRCB through its Water Recycling Construction Program
- $700,000 from the California Energy Commission
- OCWD also received six Clean Water State Revolving Fund (CWSRF) loans in the amount of $162 million from the SWRCB
- $20 million from the U.S. Bureau of Reclamation (USBR) through its Title XVI program
- $500,000 from U.S. Environmental Protection Agency (EPA)
Construction cost: $142 million
- $137 million CWSRF loan from the SWRCB
- $1 million Proposition 84 Integrated Regional Water Management (IRWM) Implementation grant from the DWR
Construction cost: $284 million
- $3.6 million Proposition 1 IRWM Implementation grant from the DWR
- $5 million Proposition 13 and Proposition 1 grants from the SWRCB
- OCWD also received two CWSRF loans in the amount not to exceed $186 million from the SWRCB
- Low interest rate loan not to exceed $135 million from EPA’s Water Infrastructure Finance & Innovation Act (WIFIA)