During 1992–94, the U.S. Geological Survey (USGS), in cooperation with the North Central Texas Council of Governments (NCTCOG) collected stormwater runoff data for the cities and Texas Department of Transportation (TxDOT) Districts in the Dallas-Fort Worth (DFW) area to meet the regulatory requirements of the application phase for the National Pollutant Discharge Elimination System (NPDES) stormwater permit. The Phase I permit requirements applied to cities with populations of 100,000 or greater and to TxDOT districts with population centers of 100,000 or greater (U.S. Environmental Protection Agency, 1990). The following cities and districts in the DFW area met the population criteria: Arlington, Dallas, Fort Worth, Garland, Irving, Mesquite, Plano, TxDOT Dallas District, and TxDOT Fort Worth District. The permit applications were submitted to the U.S. Environmental Protection Agency (EPA) for approval.