Orange County Water District Moves Groundwater Pumping Inland To Prevent Seawater Intrusion
Interim Program Put in Place While Seawater Barrier Is Expanded
Orange County Water District is working with the coastal and inland water agencies and cities in Orange County to shift groundwater pumping (6.5 billions of gallons of water this year) to lessen the strain on OCWD's seawater barrier. The seawater barrier holds back the Pacific Ocean from infiltrating and contaminating the fresh water in the groundwater basin, which provides water for 2.3 million residents in Orange County. The Coastal Pumping Transfer Program, which will shift pumping from along the coastal area to inland areas, is needed due to the recent four-year drought in the Santa Ana River watershed and to relieve pressure on the seawater intrusion barrier until expansion improvements are completed in 2007.
In the 1950s and 1960s, the ocean moved about three miles inland in Orange County due to increased groundwater use and resulting decreased water levels in the groundwater basin. This resulted in several drinking water wells along the coast being permanently closed due to seawater contamination.
In the 1970s, OCWD installed an underground fresh water barrier to hold back the ocean. The barrier consisted of 26 injection wells along the coast in Huntington Beach and Fountain Valley that injected purified wastewater underground to create a "fresh water mound" above sea level, preventing ocean intrusion. Due to increased groundwater use over the years, OCWD is now at a point where the barrier must be expanded. An additional eight wells will be installed to allow OCWD to increase the amount of purified water that can be injected from 5 million gallons to 40 million gallons per day.
In the interim, OCWD has worked out an innovative solution to minimize the stress on the existing barrier by moving the pumping inland and reducing the pumping along the coast.
Coastal water agencies and cities (Mesa Consolidated Water District [Costa Mesa] and Irvine Ranch Water District and the cities of Newport Beach and Huntington Beach) will pump less water and rely on more imported water, while the inland cities of Anaheim, Fullerton, Santa Ana, Buena Park, Orange, Westminster and the Southern California Water Company (serves Cypress, Los Alamitos, Placentia, Stanton) will pump more groundwater and use less imported water.
OCWD has designed the program so that there is no cost difference for the participating water agencies, even though some will pump cheaper groundwater (about $200 for each 326,000 gallons used) and others will use more imported water (costs about $450 for the same number of gallons).
Eventually, a new water purification and water supply project, called the Groundwater Replenishment System, will be online in 2007 and produce about 40 million gallons of water per day to expand and rejuvenate the seawater barrier that currently only receives 5 million gallons of water per day.
The inland pumping transfer program will be reviewed each year to see if it is necessary to continue. Gradual refilling of the groundwater basin by recharge of the Santa Ana River and natural rainfall will help fill the groundwater basin, which also reduces the stress on the seawater barrier.