A reconnaissance water-quality appraisal of the Fountain Creek alluvial aquifer between Colorado Springs and Pueblo, Colorado, including trace elements and organic constituents

This report describes the hydrology and chemical quality of water in the stream-aquifer system along Fountain Creek and relates groundwater quality to land use, water use, and wastewater discharges. The alluvial aquifer, which is underlain by shale bedrock, is transmissive, extensively pumped, and primarily is recharged by Fountain Creek and irrigation-return flow. Groundwater flows south about 20 ft/day, average residence time is less than 10 yr. Land use primarily is urban in the northern one-third and agricultural in the southern two-thirds of the area. Major ions, boron, iron, lithium, selenium, strontium, and uranium increased in concentration downgradient. The largest concentrations of nitrogen and detergents were in the northern end of the area because of recharge of sewage effluent in Fountain Creek. Other trace elements usually were present in concentrations less than 20 mg/L. Volatile organic compounds were detected in water from 11 of 20 wells sampled. Samples from 4 of the 20 wells were analyzed for semivolatile organics using a closed-loop stripping technique, which detected additional compounds at nanogram/L concentrations. (USGS)