You are here:
GROUND-WATER QUALITY CLASSIFICATION FOR THE VALLEY-FILL AQUIFER IN SPANISH VALLEY, GRAND AND SAN JUAN COUNTIES, UTAH --A BASIS FOR PRESERVING HIGH QUALITY GROUND-WATER RESOURCES, UTAH GEOLOGICAL SURVEY
Impact/Purpose:
Spanish Valley, (in Grand and San Juan Counties) are semi-rural areas in southeastern Utah experiencing an increase in residential development. Spanish Valley includes Moab, the County Seat of Grand county, and a portion of unincorporated San Juan County. In 1998, the population of Moab was 4159 and the population of all unincorporated areas of San Juan County was 781; by 2020, these populations are expected to increase to 8159 and 1012, respectively (Utah Division of Water Resources 2000). While most of the development in the Grand County portion of Spanish Valley is on a community sewer system, development in the San Juan County portion uses septic tank soil-absorption systems for wastewater disposal. These septic-tank systems are on valley-fill deposits which are a major drinking water aquifer for the area.
The increase in development and its potential impact on the quality of ground-water resources has caused concern among local government officials in Spanish Valley who wish to preserve the high quality of ground water in the aquifer system. Local government officials would like to utilize the Aquifer Classification by the Utah Water Quality Board, to help protect their valuable ground-water resources from degradation associated with poorly planned development.
Description:
The proposed study will consist of an evaluation of current ground-water quality using the Utah Water Quality Board's ground-water-quality classification system based mostly on total-dissolved-solids concentrations as follows: class 1A (Pristine), less than 500 mg/L; class 2 (drinking water quality), 500 to less than 3000 mg/L; class 3 (Limited Use), 3000 to less than 10000 mg/L; and class 4(saline), 10000 mg/l and greater. Two other ground-water-quality classes, class 1B (Irreplaceable) and class 1C(Ecologically Important), are not based on total-dissolved-solids concentrations determined from sampling and analyzing ground water from 40 wells completed in the valley-fill aquifer and with a widespread geographic distribution in Spanish Valley. Potential contaminant sources in the valley will also be mapped via a windshield survey. The product will include GIS maps showing total-dissolved-solids concentrations, ground-water-quality classes, and potential contaminant sources. The final classification map will be approved by the Utah Water Quality Board and be available for all regulatory agencies to consider for ground-water protection when performing activities in this area.