Comparing Properties of Water Absorbing/Filtering Media for Bioslope/Bioswale Design

Drainage from highways, particularly the first flush of runoff, contains high levels of contaminants such as suspended solids, metals, and organics. To restrict the discharge of polluted stormwater, the National Pollutant Discharge Elimination System (NPDES) State Disposal System (SDS) General Permit issued by Minnesota Pollution Control Agency (MPCA) in 2013 requires that the first inch of stormwater runoff from new impervious should be held on site through infiltration, harvesting or reuse. Multiple types of infiltration materials have been studied in the laboratory and the field, but few studies have considered the application of local materials for best management practices (BMP). The objective of this project is to determine the characteristics of various naturally occurring water adsorbing and filtering media, such as peat and muck, found along road construction projects in Northern Minnesota. Salvage and reuse of these materials during road construction will be evaluated for stormwater treatment, including absorption, infiltration, filtration, and pollutant capture, in constructed vegetated slopes along highway right of ways. The naturally occurring material will be compared to leaf and grass feedstock compost. Based on the characterization results, suggestions for testing, design, implementation, and monitoring protocols for construction of an in-field pilot study will be developed for bioslopes and bioswales. The sites(s) for the real world evaluation will be determined by Dwayne Stenlund from the Minnesota Department of Transportation (MnDOT). The utilization of local salvage materials for stormwater treatment has potential implications for future green infrastructure development, as well as reducing project cost.