Determining urban storm water BMP effectiveness

The goal of this U.S. EPA-funded cooperative research program with the ASCE is to develop a more useful set of data on the effectiveness of storm water best management practices (BMPs) used to reduce pollutant discharges from urban development. BMP monitoring data gathered at a particular site should not only be useful for that site, but also need to be useful for comparing the effectiveness of similar and different types of BMPs at other locations. Most BMP effectiveness studies in the past have provided data that is difficult, if not impossible, to use in comparing BMP design effectiveness and in the selection among individual BMP types to meet desired goals. This paper describes some of the comparability problems encountered between different BMP effectiveness studies. Also discussed are considerations that affect data transferability, such as methods used for determining efficiency and statistical significance. It outlines the efforts used to establish and analyze the currently available data and proposes protocols for future analyses, when more studies that have data are available. Finally, it recommends that effluent quality appears to be a much more robust measure of BMP efficiency than the currently used "percent removal" metrics.