Well Contamination in Fresno County

Groundwater Contamination

Many of us do not think about what is in the water that we drink or where it is sourced, especially in the United States. Unfortunately, clean and safe drinking water is not accessible to all communities and is often the result of the contamination of water sources, like groundwater. Groundwater contamination occurs when chemicals like those used for agriculture, move into the hydrologic system. With the rise of more industrialized agriculture in the 1960s, the use of chemicals has continued to increase to improve crop productivity and control disease and pests. Common contaminants include nutrients like nitrogen and phosphorus and pesticides which infiltrate the water system USGS. Additionally, the transition of land into farmland further impairs and disrupts water systems. While certain areas suffer from elevated exposure, this issue is widespread. In a USGS study, researchers found that at least one pesticide was found in about 94 percent of water samples and in more than 90 percent of fish samples taken from streams across the Nation, and in nearly 60 percent of shallow wells sampled Hamilton et al. 2004. This poor groundwater quality can have negative effects on agricultural production, ecosystems, and disadvantaged communities as they lack the financial and technical capacity to manage water quality issues Hanak, 2019.

Fresno County, California

Fresno County is located in one of the most productive agricultural areas in the world. The county alone has nearly 1.9 million acres of farmland and produces more than 300 crops. In 2020, the county was ranked the #1 agricultural county in the U.S. with a gross value of $7.98 billion. Top crops include almonds, grapes, pistachios, tomatoes, oranges, and peaches Visit Fresno County. As a result, the use of pesticides, fertilizers, and other agricultural runoff heightens the risk of contamination via groundwater runoff. Across California, chemicals like per- and polyfluoroalkyl substances are being discovered in well-water and irrigated cropland is the largest source of groundwater nitrate pollution in the Central Valley Dzurella 2015. Effects of contamination include chronic diseases like cancer, gastrointestinal illnesses, and nervous or reproductive system impacts. Simazine, diuron, norflurazon, and bromacil have been detected in well water samples; they have been listed in regulation as known groundwater contaminants, and their use is regulated in vulnerable areas Troiano et al. 2013. Previous studies have established that race/ethnicity and socioeconomic class have previously been correlated with exposure to nitrate and arsenic contamination in community water systems in the San Joaquin Valley where small water systems are more vulnerable to inadequate regulatory protection and to uneven monitoring Balazs 2014.In addition to groundwater pollution, communities in West Fresno also rank as one of the areas most burdened by air pollution in California, and 20 of the most polluted census tracts in Fresno County compose of 89% of people of color in the county Fresno Department of Public Health. Additionally, previous studies in the San Joaquin Valley have shown that among these smaller water systems, community water systems that serve larger percentages of Latinos or home renters experience higher levels of nitrate in their drinking water Balazs 2011. Due to the high agricultural production in the county and the extensive use of pesticides and fertilizers, this project will analyze the relationships between population demographic characteristics and groundwater well contamination to determine if disadvantaged communities are disproportionately affected by the negative effects of groundwater contamination.

Maximum Contaminant Level in Groundwater Wells. Source: CA Small State Water System. Contaminants include NO3N, Uranium, Alpha particles, As, Cb, and lead. Of the 18 wells measured, one well had 4 contaminants above MCL, 1 well had 3 contaminants above MCL, 6 had 1 contaminant above MCL, and 8 did not exceed MCL. Based on these levels, well water quality risk was rated as low, medium, or high. Wells labeled high had at least one contaminant above MCL, and medium contained at least one between 80%-100% MCL.

Map of Groundwater Threat and Well Locations