Distribution of dissolved nitrate and fluoride in ground water, Highland-East Highlands, San Bernardino County, California

In the Highland-East Highlands area of southern California, concentrations of nitrate in water from many wells exceed the U.S. Environmental Protection Agency 's and the California Department of Health 's recommended limit for public water supplies. The nitrate standards for public water supplies in the study area are commonly met by blending the high-nitrate water with low-nitrate water before distribution; however, some of the low-nitrate water sources have fluoride concentrations that exceed the optimum level, or in a few cases exceed the maximum level recommended by the California Department of Health. Nitrate-nitrogen concentrations in the study area are generally between 1 and 20 milligrams per liter. In general, nitrate-nitrogen concentrations exceeding 10 milligrams per liter are found in water from wells perforated at depths of less than 500 feet. (Woodard-USGS)