NTM Engineering was recently awarded a contract for professional engineering services to complete a Pollutant Reduction Plan (PRP) for the Centre Region MS4 Partners (PARTNERS). The PRP will be included with each PARTNERS 2017/2018 National Pollutant Discharge Elimination System (NPDES) Municipal Separate Storm Sewer System (MS4) permit renewal. The PARTNERS are electing to collaborate on a Pollutant Reduction Plan for the 16,884 acres of urbanized area within their borders.
NTM is collaborating with the PARTNERS to develop a GIS based regional sewershed map defining regulatory boundaries for the assessment of pollutant loads and necessary pollutant load reductions. Pollutant loading is being assessed using the Mapshed watershed modeling tool. Mapshed is a process based modeling tool that has the ability to model a wide range of urban landscape and cover conditions, and includes additional functionality to more directly support MS4-related analysis. To produce more realistic pollutant load estimates, the model is being calibrated to reflect the unique surface runoff characteristics associated with the underdrained karst nature of local watersheds.
NTM’s approach includes aggregating over 200 individual sewersheds and discharge points into six subwatersheds for analysis. Existing pollutant loads and regulatory load reductions are being evaluated by subwatershed and PARTNER municipality/institution. Pollutant load reductions associated with existing Stormwater BMPs are included in the existing load analysis effectively reducing load reduction requirements.
NTM is working with the Partners to identify and site appropriate BMP’s to meet regulatory load reductions. A BMP implementation schedule and cost estimates are also being developed, and NTM will present the PRP at a joint municipal public meeting.
