This report provides guidelines to evaluate and select hydraulic modifications to existing drainage infrastructure that will help mitigate potential impacts of highway runoff on receiving waters. The guidelines are directed specifically at roadway facilities in dense urban areas that can be particularly difficult and costly to retrofit because of space limitations, high pollutant loadings, hydrologic flashiness, hydraulic constraints, legacy contamination, utility conflicts, and other issues. The guidelines are accompanied by a Microsoft® Excel-based design and sizing tool on a CD-ROM included with the print version of the report. The tool generates best management practice (BMP) performance curves that relate the performance and design criteria for selected BMP controls described in the guidelines for each of the 15 U.S. rain zones. The excel spreadsheet that is content on the CD-ROM is available for download at http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_728.xlsx. (Author/publisher)
Samenvatting