Exfiltration Trenches for Post Construction Storm Water Management for Linear Transportation Projects: Field Study of Suspended Materials

Highway storm water runoff contributes to the degradation of surface water quality in the United States. The most important pollutant in highway runoff is the total suspended solids (TSS). The United States Environmental Protection Agency (U.S.EPA) requires the runoff to be treated before it is conveyed to surface water. The exfiltration trench is one of the best management practices (BMP's) utilized by the Ohio Department of Transportation (ODOT) to treat highway runoff in-situ and consists of three layers: pervious concrete, type 3 backfill material (aggregate) and type 2 backfill material (sand). In this study, the exfiltration trench located on SR7, OH, is evaluated based on the pollutants' removal efficiency, particularly, TSS. TSS was removed at an efficiency of 41% in the originally constructed trench while the reconstructed trench achieved 69% TSS removal. Other water quality parameters investigated in this study include particle size analysis, turbidity and pH which were performed on both influent (highway runoff) and effluent (treated influent) samples.