Assessment of water quality in the South Indian River Water Control District, Palm Beach County, Florida, 1989-94

The South Indian River Water Control District is located in an area of northern Palm Beach County, Fla., where many residents must rely on private wells for domestic water supplies and individual septic tanks for waste disposal. As a result, contamination of the surficial aquifer system and availability of a potable water supply have become of increasing concern. To address this concern, the U.S. Geological Survey, in cooperation with the South Indian River Water Control District, conducted a study to assess ground-water and surface-water quality in the District from 1989 to 1994. The study consisted of water-quality monitoring at 11 wells and 14 surface-water sites located within the District. Water samples were analyzed for major inorganic constituents and physical characteristics, trace metals, nitrogen and phosphorus species, and synthetic organic compounds.

The predominant water type within the South Indian River Water Control District is calcium bicarbonate; however, mixed-ion type water and sodium bicarbonate type water also exist in varying amounts. Sodium chloride type water is present in the western areas of the District due to incompletely flushed residual sea water. Results of the study indicated that concentrations of most constituents were within State drinking-water standards as established by the Florida Department of Environmental Protection, but concentrations of certain constituents occasionally exceeded drinking-water standards in some ground-water and surface-water samples. Sodium and chloride concentrations exceeded the standards in ground water at two wells, dissolved-solids concentrations at five ground-water wells and one surface-water site, and color values at all 11 ground-water wells and all 14 surface-water sites.

Other constituents also exhibited concentrations that exceeded drinking-water standards. Cadmium and zinc concentrations exceeded the standards in ground water at one well, and lead concentrations exceeded the standard in ground water at five wells. Nitrogen and phosphorus specie concentrations did not exceed respective drinking-water standards in any ground-water or surface-water samples. Additionally, organic compounds were not detected at four surface-water sites monitored for National Pollutant Discharge Elimination System constituents. Several synthetic organic compounds were detected at or above 50 micrograms per liter in water samples collected from six ground-water wells and three surface-water sites.