The alluvial valley fill along the South Platte River and tributary streams, Cherry Creek, Bear Creek, and Clear Creek is exposed to residential, commercial, and industrial land-uses throughout the Denver metropolitan area. Because this aquifer is unconfined and has a shallow water table, the water quality can be easily altered by surface activities. A survey of groundwater qaulity in 30 shallow alluvial wells in the greater Denver metropolitan area was done to evaluate the effect of urban land use on this aquifer. Water-quality constituents analyzed include a broad range of organic and inorganic compounds. An objective of the survey was to define the areal distribution, ranges, and interrelation of these constituents.
Pesticides, hydrocarbons, and volatile organic compounds were frequently detected. The concentration ranges and distribution of analytes within the land-use classification scheme is presented. Several of the wells measured during sampling had dissolved-oxygen concentrations of less than 1.0 milligrams per liter. The lowest dissolved-oxygen concentrations and the highest sulfide and dissolved-iron concentrations occurred in hydrocarbon-contaminated groundwater. Preliminary results indicate that low nitrate concentrations may occur because of the negative redox potential associated with the low dissolved-oxygen conentrations.
1 U.S. Geological Survey, Box 25046, MS 415, Denver Federal Center, Lakewood, CO 80225