Drinking Water Contaminant Findings

CalEnviroScreen 4.0 Drinking Water Contaminant values are used to evaluate the amount of environmental contamination in the census tracts due to the impacts of contaminated drinking water. The data shown in the above figure is based on a drinking water contamination index for selected contaminants from 2011 to 2019. It is important to note that “the drinking water contaminant index in CalEnviroScreen 4.0 is not a measure of compliance” with California’s state standards. “The drinking water contaminant index is a combination of contaminant data that takes into account the relative concentrations of different contaminants and whether multiple contaminants are present. The indicator does not indicate whether water is safe to drink.” (OEHHA 2021a, page 54) 

“Most drinking water in California meets health standards. However, drinking water sometimes becomes contaminated with chemicals or bacteria above the standards. Both natural and human sources can contaminate drinking water. Natural sources include rocks, soil, wildlife and fires. Human sources include factories, sewage, and runoff from farms. One common contaminant, arsenic, occurs naturally in some rocks and soil and is often found in groundwater in California. It can cause cancer. Nitrate from fertilizer or manure can leach into groundwater and contaminate wells. Nitrate can cause a blood disorder in infants called blue baby syndrome.”  (OEHHA 2021b)

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Locations of Underground Contamination Plumes

Groundwater Threats

CalEnviroScreen 4.0 (CES4) Groundwater Threat values are used to evaluate the environmental effects in census tracts due to the presence of groundwater threats which are calculated as the sum of weighted “GeoTracker” sites from the State Water Resources Control Board (SWRCB), and downloaded by OEHHA in July 2021. (OEHHA 2021a, page 113) “Hazardous chemicals are often stored in containers on land or in underground storage tanks. Leaks from tanks can contaminate soil and groundwater. Common soil and groundwater pollutants include gasoline and diesel fuels at gas stations, as well as solvents, heavy metals and pesticides. Leaking tanks can affect drinking water and expose people to contaminated soil and air. The land and groundwater may take many years or decades to clean up.” (OEHHA 2021b)It is important to note that “the nature and the magnitude of the threat and burden posed by sites maintained in GeoTracker vary significantly by site type (e.g., leaking underground storage tank or cleanup site) and status (e.g., Completed Case Closed or Active Cleanup). The indicator takes into account information about the type of site, its status, and its proximity to populated census blocks.” (OEHHA 2021a, page 113) Note, it is not clear whether the CES4 data took the EPA’s 2019 and 2020 studies into account which show a large groundwater contamination plume covering the Del Amo community, and issued a technical impracticability waiver for the “2020 EPA Containment Zone” that allows the groundwater to remain contaminated forever due to the inability to clean its with today’s technology. These waivers are very rare. Normally the responsible party would be required to clean the groundwater to drinking water standards. These layers are shown in Figure 1 (page 8) and Appendix A (page 35)

To view the full health report on the Coalition for Clean Air website, please click here.