Final Report of the Nationwide Urban Runoff Program in Austin, Texas

dc.creatorCity of Austin
dc.creatorEngineering-Science, Inc.
dc.description.abstractThis report presents an overview of the Nationwide Urban Runoff Program in Austin, Texas. The study documents the existing impacts of storm water runoff loadings upon Lake Austin and Town Lake water quality (two lakes within the Austin metropolitan area), and characterizes runoff water quality from two low-to-medium-density residential land uses and one structural control measure. The storm water monitoring program was divided into a receiving water and a storm water sampling study. The storm water sampling study involved an examination of two test watersheds and analyzed the mitigating effects of percent of impervious cover and storm water retention on runoff pollutant loads. The two test watersheds were evaluated on the basis of such storm water quality parameters as chemical oxygen demand, biochemical oxygen demand, total organic carbon, ammonia, phosphates, suspended solids, fecal coliforms, metals, and toxic organics. The receiving water study emphasized water quality sampling, sediment quality sampling, and the analysis of resident fishes for selected indicators of urban storm water pollution (i.e., metals and pesticides). A detailed analysis of both the storm water runoff monitoring data base and the receiving water survey data are presented. Data developed for Austin residential land use indicated that a medium density residential land use (impervious cover approximately 39 percent) does produce a larger runoff pollutant load than a low-density residential land use {impervious cover approximately 21 percent) primarily because of the quantity of storm water runoff from the two areas. Other than the presence of measurable quantities of lead and zinc, only trace levels of insecticides and defoliants were present in the storm water runoff samples collected from the two test watersheds. Comparison of runoff and pollutant loadings from the two residential areas with those from an undeveloped area with otherwise similar hydrologic characteristics clearly indicated that urbanization of lands with this type of geology, soils, vegetation, and topography significantly increases runoff pollutant loads. Storm event oriented water quality sampling on Town Lake and Lake Austin indicated that the short-term effects of runoff-generated pollutants on receiving water quality can be significant, although chronic water quality impacts were not apparent. Lake bottom sediments contained environmentally persistent constituents (i.e., metals and pesticides) which probably were deposited over many years. The concentrations of metals and chlorinated hydrocarbon pesticides and PCBs measured in the tissues of fish samples collected from both Town Lake and Lake Austin were not at a level considered hazardous to public health. The total chemical cost associated with the treatment of drinking water was affected by storm water runoff and subsequent lake water quality. The incremental increase in cost of treatment is minimal, however, based on the magnitude of the difference and the small percentage of time during the year that the situation occurs.
dc.description.departmentWaller Creek Working Group
dc.publisherCity of Austin
dc.relation.ispartofWaller Creek Working Group
dc.titleFinal Report of the Nationwide Urban Runoff Program in Austin, Texas
dc.typeTechnical report

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