One contamination plume under Orange County, CA       Graphic: Orange County Water District

By Natasha Lasky, ODP Staff Writer

Over 70% of the drinking water in Orange County, California comes from groundwater. But historic manufacturing nearby has polluted it due to the improper discarding of toxic chemicals. The LA Times reports that there are three major cleanup projects involving groundwater beneath 22 Californian cities, including Anaheim, Santa Ana, Fullerton, Tustin, Garden Grove, Orange, Villa Park, Yorba Linda, Irvine, and Placentia.  The federal Superfund program is helping to find the responsible parties and it also makes other assistance possible.  According to the EPA, the underground aquifer is a “critical water resource” that supplies drinking water for 2.4 million people.

Why this Matters:  The problem of water contamination is more widespread than most Americans realize.  Orange County runs the largest water purification system in the world because of its dependence on groundwater. The county must ensure that the contamination does not reach the main aquifer or even drinking wells, which is hard because it’s underground. Industrial activity throughout the 20th century, before waste disposal for military manufacturing and metalworking was regulated, continues to cause problems today. The district has to test drinking water wells regularly for all varieties of chemicals, but so far they are staying ahead of the contamination.

In Uncharted Waters

Orange County is already in the process of cleaning up the groundwater under the cities of Anaheim, Santa Ana, Fullerton, Tustin, Garden Grove, Orange, Villa Park, Yorba Linda, Irvine, and Placentia.  But solving this problem could be incredibly difficult and expensive to treat because the contamination is far underground. The contaminated area in the South Basin is about two and a half miles long and about a mile and a half wide. This plume has formed out of many different sites of contamination, which then seeped into the groundwater to form a large area of contamination. Meanwhile, a five-square-mile plume of contamination in the North Basin, contaminated with volatile organic compounds from industrial manufacturing in the mid 20th century. Five water wells have already been shut down because of the pollution, and other wells could be shut down as well. Meanwhile, more than 40 wells were shut down when the O.C. Water District found PFAS, a toxic substance linked to cancer

Roy Herndon, chief hydrogeologist with the water district, told the LA Times: “Getting your arms around a large groundwater plume takes many years. It’s a step-by-step process because everything is underground. You can’t see it. You have to do a lot of water well drilling and test boreholes where we collect water samples at different depths.”  He continued: “The difficulty is trying to figure out where and how did the contamination get from the shallow aquifer into the principal aquifer,” Herndon said. “The sooner we can get a remedy in place, in terms of cleaning up the shallow aquifer then that will then take away the threat of how these contaminants are finding their way down into the principal.”