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Runoff from roadways carries pollutants which may be detrimental to aquatic ecosystems. The primary pollutants of concern for roadway runoff are solids and heavy metals, particularly cadmium, copper, and zinc. Roadway runoff falls under the legislation of the Clean Water Act (CWA) via the National Pollutant Discharge Elimination System (NPDES). CWA regulates discharge of nonpoint source pollutants, such as roadway runoff, by issuing permits to public entities which manage Municipal Separate Storm Sewer Systems (MS4s). Part of the Nebraska Department of Roads (NDOR) permitting requirement is to create a design guide for Best Management Practices (BMPs) tailored to remediate roadway runoff in Nebraska, which this document is intended to fulfill.
BMPs which are most applicable to treating roadway runoff are those which can remove 80% of the total solid load in the runoff, reduce metal concentrations to below acute toxicity levels, have low maintenance burden, are cost effective, do not pose a safety hazard to motorists, can be implemented within the right-of-way, do not negatively impact the road subgrade, and are aesthetically pleasing. The BMPs which best fit these criteria are vegetated filter strips, vegetated swales, bioretention, sand filters, and horizontal filter trenches. In this study fact sheets and design guides have been compiled for each of these BMPs. The fact sheet provides background on the BMP including cost considerations, siting constraints, and predicted maintenance requirements. The design guide provides the process for sizing the BMP, design criteria the BMP must meet, and a design example which goes through the design process for a hypothetical application.
Adviser: John Stansbury