G&A Stormwater Initiatives 101

April 22, 2019

Pollutant Reduction Plans - Planning for Success

A recent PADEP requirement of the Municipal Separate Storm Sewer System (MS4) permit cycle is the development of a Pollutant Reduction Plan (PRP) and/or Total Maximum Daily Load (TMDL) Strategy Plan to reduce pollutant loading in impaired receiving waterways.  Those pollutants are from non-point sources, and are primarily sediment and nutrients washed from the land into streams.  The objective is simple: improving water quality.  The path to that objective is a bit more complicated.  Success starts with a strong understanding of hydrology and how we’ve impacted stream systems.  It continues with planning, informed by science, and enabled by technology. 

Gilmore & Associates Inc. (G&A) is a leader in the preparation of Stormwater Management Plans in a variety of municipal and watershed settings. Our municipal engineering staff oversees the administration of our client’s MS4 permits, and have prepared 28 separate PRP/TMDL Strategy Plans in pursuit of Individual and General MS4 Permits. Our staff is fully integrated across six Pennsylvania offices making for easy access to the shared knowledge of our many professionals.  We planned for the PRP requirements as a team, promoting efficiency for our clients, eliminating duplication of efforts, identifying points of contact within the team for communication with PADEP, and ultimately generating a PRP template for use throughout the Firm.

We have prepared plans ranging from urbanized watersheds such as the Wissahickon, Pennypack, and Little Neshaminy Creeks in Ambler Borough, Montgomery, Horsham, and Lower Moreland Townships to more rural, agriculturally dominated watersheds such as Skippack and Indian Creeks in Franconia Township to sparsely developed woodlands of the Sambo Creek in Middle Smithfield Township.  

G&A utilizes available technologies such as Smartphone/Tablet Theodolite Apps, Survey Hand-held GPS Units, ArcMap (GIS) and MapShed to assist in mapping, planning, and pollutant reduction analysis of the PRPs.  GIS is an integral part of developing a PRP.  It is the mapping backbone locating roads, inlets, outfalls, piping, swales, catch basins, channels, and any other components of the storm sewer collection system located in each municipality.  GIS is also used to determine the municipality’s planning area, which is the land within the municipality that collects runoff or contributes runoff to that municipality’s MS4.  Once the planning area is determined, programs such as MapShed are used to determine the municipality’s existing pollutant load data.  From there, BMPs are implemented within the MapShed program to ultimately reduce the municipality’s required sediment and nutrient loadings by 10% and 5%, respectively.

As approved PRPs emerge from the PADEP review process, Gilmore & Associates is preparing BMP designs for our clients to implement their PRPs/TMDLs.  We will be using the same integrated approach when it comes to turning the focus from planning to design of BMPs.  A team approach is necessary to efficiently navigate through the PADEP Chapter 102 and 105 permitting.  It is anticipated that the BMP designs could consist of existing detention basin retrofits, new infiltration basins, bioswales, forested streambank buffers, and streambank restoration.   G&A has successfully assisted our clients in obtaining over $60 million in grant funding for various municipal and municipal authority projects.  We are now implementing the same success measures to help our clients receive grant funding for these MS4 improvement projects.