This report looks at how urbanization has affected the storm water quality of Waller Creek. This data was analyzed with a database constructed for the report. As such, the report contains hydrologic data, impervious cover maps, and other important data for analyzing how various factors have impacted the creek over time. ; EXECUTIVE SUMMARY: This report completes the requirements of a grant study funded by the United States Environmental Protection Agency (USEPA). The fIrst objective of this study was to establish a stormwater database for Waller Creek basin. Secondly, the study would evaluate the impact of urban development on stonn water quality. Finally, the study would identify retrofIt measures for the improvement of water quality in the basin, as well as in Town Lake -- the primary receiving waters. As part of the City of Austin's (COA) Stonn Water Monitoring Program, the City has monitored the stonn water discharges at fIve sites in Waller Creek basin for the past three years. With data collected from the stonn water monitoring, the COA has implemented the EPA's Stonn Water Management Model (SWMM) model for Waller Creek basin. The City has also' developed a statistical water quality model for this basin. Through watershed simulations using these models, the City was able to estimate the quality and quantities of stonn water discharges in this basin for various retrofIt plan options. The results of simulation indicate that the flood control plans specifIed by the studies of Chan and Loomis (see Reference List) provide some water quality benefIts. As compared to the present condition, the tunnel diversion suggested by the Loomis study would not only protect the downtown area from flooding, but reduce the pollutant loads entering Town Lake by an average of about 10 percent. This reduction is due to less bank erosion between the diversion and Town Lake. The "Option 7" flood management plan (4 flood control detention basins) proposed by the Chan study for the upper watershed would reduce the pollutant loads carried by Waller Creek by about 5 percent. An alternative to the "Option 7" plan is to modify the detention ponds into dual-purpose, dry or wet ponds. This option would increase the water quality benefIt to an average of about 10 percent. The channel erosion control projects recommended by these studies (that is, the repair and modifIcation of 67 channel bank section), would likely provide good water quality benefIt. This benefIt can be quantifIed through a monitoring and modeling project. The data presented by this study further confIrms that the impact of urban development on stonn water quality is two fold. The pollutants discharged from a creek generally increase with increasing urban development in the basin. In addition, the channel and bank erosion will increase with increased flow rates resulting from higher basin imperviousness. This additional erosion will increase the concentrations of pollutants in the stream. On the average, the channel and bank erosion contributed about 50% of total loads or concentrations of pollutants discharged by Waller Creek. The testing of control measures indicates that wet pond, sand fIltration, and vegetated channels are effIcient in detaining pollutants. Dry pond and large oil/grit separator are good pre-treatment devices. Dry or wet pond, and vegetative channels are most suitable for retrofIt projects. The database, computer models. and retrofIt plan evaluations are useful for studying other urban watersheds in Austin. as well as in areas of other municipalities. ; Waller Creek Working Group