GROUND WATER QUALITY CLASSIFICATION FOR THE BASIN-FILL AQUIFER, EAST SHORE AREA, DAVIS COUNTY, UTAH

We classified ground-water quality in the basin-fill aquifer in the east shore area of Davis County for the Davis County Health Department. The study area is in the southern part of the east shore area of Great Salt Lake in the Great Basin physiographic province. Important ground-water resources in the east shore area exist in unconsolidated to semiconsolidated Quaternary basin-fill deposits.

We collected ground-water samples from 20 wells throughout Davis County and measured field parameters at each site. The Utah Department of Epidemiology and Laboratory Services analyzed all of the ground-water samples that we collected for general chemistry, dissolved metals, and nutrients; they also analyzed samples from two wells for organics and pesticides and a sample from one well for radionuclides. Our data were augmented by specific conductance, total-dissolved-solids concentration (TDS), and selected chemical constituents from other sources of ground-water data, including 39 samples collected from public-supply wells as reported by the Utah Division of Drinking Water and 64 samples from the U.S. Geological Survey.

We classified ground-water quality in the Davis County portion of the east shore area into two classes: Class IA (Pristine) and Class II (Drinking Water Quality). For Class IA, TDS concentrations in the Davis County part of the east shore aquifer system range from 86 to 488 mg/L. Most of the study area, about 85% of the area of the basin fill, is Class IA. For Class II, TDS concentrations in the Davis County part of the east shore aquifer system range from 520 to 1780 mg/L. Total basin-fill area coverage of Class II water quality is 15%. Class II ground-water quality is dominantly in the southeastern part of the study area.

We also mapped 1798 potential contaminant sources in the Davis County area. We located 997 potential contaminant sources from field observations via a windshield survey and compiled an additional 801 potential contaminant sources using information obtained from the U.S. Environmental Protection Agency, the Utah Department of Environmental Quality, the Davis County Health Department, and the Utah Automated Geographic Reference Center.