Stormwater Master Planning – Pollutant Reduction Plans

G&A has extensive experience in the preparation of Stormwater Master Plans in a variety of municipal and watershed settings. Our municipal engineering staff oversee the administration of our client municipalities’ MS4 (Municipal Separate Storm Sewer System) permits, and a recent requirement of the MS4 permit cycle is the development of Pollutant Reduction Plans (PRPs) and/or TMDL Strategy Plans to reduce pollutant loading in receiving waterways. G&A has prepared 28 separate PRP/TMDL Strategy Plans in pursuit of Individual and General MS4 Permits. These plans range from urbanized watersheds such as the Wissahickon, Pennypack, and Little Neshaminy Creeks in Ambler Borough, Montgomery, Horsham, and Upper Moreland Township to more rural, agriculturally dominated watersheds such as Skippack and Indian Creeks in  Franconia Township. These plans utilize GIS mapping resources to establish planning areas to regulated outfalls.

A Generalized Watershed Loading Function model or GWLF is used to determine existing pollutant loads, and to inform the selection and siting of Best Management Practices (BMP’s) to reduce those loads to target levels. Public engagement and municipal adoption are  required components of each plan. Unlike many watershed studies, these plans drive the implementation of watershed restoration. As approved PRP’s emerge from the PADEP review process, G&A is providing BMP design to implement the BMP’s in the plan.  These range from existing detention basin retrofits, new infiltration basins, bioswales, forested streambank buffers, and streambank restoration. We are assisting with funding of these improvements through grant writing.


Various Municipalities

Southeastern PA

Market Segment



Erik Garton, P.E.
Executive Vice President