As an MS4 permittee, West Hempfield Township needed to submit a pollutant reduction plan (PRP) to comply with the Pennsylvania Department of Environmental Protection’s MS4 Program requirements. The Township needed to determine the existing pollutant loading rates attributed to the MS4-regulated area, and identify stormwater best management practices (BMP) to reduce sediment, phosphorus, and nitrogen loads by 10, 5, and 3 percent respectively.

The Township’s goal was not only to meet the percentage requirements, but also establish the lowest possible pollutant load. The existing urban boundary included significant areas of rural and agricultural land uses. RETTEW worked with West Hempfield Township to exclude these areas from the plan and reduce the regulated area from 5,189.9 acres to 1,853.8 acres, an approximate 65 percent reduction in area. RETTEW also reduced existing pollutant loads by removing areas covered by other National Pollutant Discharge Elimination System Permits and state road rights-of-way, and was credited for 46 existing stormwater BMPs for water quality benefits. The reduction in baseline pollutant loads, in turn, reduced the required pollutant reductions, resulting in cost savings for the Township.

RETTEW’s extensive experience in pollutant reduction planning and our GIS mapping expertise helped the Township achieve the minimum required pollutant reductions in a cost-effective manner and will save municipal taxpayer dollars.