||As part of the National Water-Quality Assessment (NAWQA) program, the U.S. Geological Survey (USGS) studied the effects of human activities on the quality of shallow ground water in areas with recently developed urban land use in Salt Lake Valley, Utah, an urban area within the Great Salt Lake Basins study unit (fig. 1). Pioneers first settled Salt Lake Valley in 1847, and an irrigation system was developed soon after to grow crops in the semiarid climate. Agricultural and undeveloped areas in the valley were converted to residential and commercial uses as the population increased to about 850,000 in 1999 (U.S. Census Bureau, written commun., 2000). The study was done from 1999 to 2001 in recently developed residential/commercial areas of the valley in which shallow ground water has the potential to move to a deeper aquifer that is used for public supply.