Jepsen, R, Caraco, D,and Fraley-McNeal, L. 2020. Evaluation of the Benefits of Stormwater Retrofits Using MS4 Monitoring Data in Carroll County,Maryland. Watershed Science Bulletin, Center for Watershed Protection, Ellicott City, MD.

Stormwater, MS4, Monitoring, Retrofits

The Interstate Commission on the Potomac River Basin and the Center for Watershed Protection conducted a pilot study for three subwatershed monitoring locations in Maryland to characterize stormwater discharges and evaluate watershed restoration activities. The main objectives were to determine if there are trends in water quality over time and if they are related to watershed restoration or best management practices (BMPs). This article focuses on a pilot study of the Airpark Business Center in Carroll County, Maryland. Trend analysis of water quality parameters, unit loads, and runoff coefficients was implemented on the water chemistry data using a variety of statistical methods. Overall, the Carroll County subwatershed showed the most noticeable response to BMPs of the three watersheds studied in the pilot, with decreasing metals and nitrogen species noted at the outfall site, where a large wet pond retrofit had taken place. The results suggested that the impacts of the retrofit at the Carroll County outfall could be directly linked to reductions in both pollutant concentrations and pollutant loads.