Issue #9           

Winter 2005           


The Basin Bulletin   
Newsletter for Stakeholders of the Raritan Basin Watershed    



D&R Canal Tributary Assessment & NPS Management Plan,

Franklin Township & South Bound Brook Borough, Somerset County

Partners:  NJWSA, Franklin Township, South Bound Brook Borough

This project addresses nonpoint sources of pollution from influent water sources to the Canal in the State Park and in the vicinity of drinking water intakes.  New Jersey Water Supply Authority (NJWSA) and Franklin Township have located and assessed the “infalls” to the Canal.  The “infall” assessment included determining which ones contribute the most pollutants and suspended sediment to the Canal and development of conceptual approaches for the management of nonpoint source loads. The consultants, Princeton Hydro and SWM Consulting, are preparing preliminary designs of nonpoint source control best management practices.  Where necessary, resources beyond this 319(h) grant will be sought to implement BMPs based on the nonpoint source pollution management plan.

NJWSA’s project began with field reconnaissance to identify all infalls to the Canal within the study area.  While a 1999 USGS study found twelve infalls within this area, NJWSA identified 63 infalls.  Infall identification was complicated by the lack of a comprehensive stormwater system map and the fact that portions of the stormwater system are channeled underneath the Canal for discharge into the Millstone River.  During the field reconnaissance, each infall was photographed and located with GPS.

NJWSA delineated the drainage area for each infall using Watershed Analyst, an ArcView GIS extension.  Then the drainage area for each infall was field verified.  NJWSA and Princeton Hydro/SWM Consulting entered NJDEP land use data into WinSlamm (Source Loading and Management Model for Windows) to estimate the sediment and phosphorus loads from each drainage area.   WinSlamm allows the user to divide each land use (residential, commercial, industrial, open space, institutional and freeway) into source areas (parking areas, roof, landscaped areas, driveways, undeveloped, etc.).  The model then calculates how much of the pollutant load originates from each land use and from each source area within the drainage area for each rainfall event in the model run.   

Based on the pollutant loads from WinSlamm, NJWSA and Princeton Hydro/SWM ranked the infalls based on the unit (pounds per acre) and total phosphorus and solids discharged from each infall (see attached table of infall rankings).  Total solids, the primary concern of the study, were given a weight of 1.0, total phosphorus was given a weight of 0.5, unit solids were given a weight of 0.2 and unit phosphorus a weight of 0.1.   A final ranking of infalls was then performed based on the total number of points  (weighted points for total solids + total phosphorus+ unit solids + unit phosphorus) each infall received. 

Princeton Hydro/SWM are using the infall rankings to guide the development of recommendations for BMPs.  They will begin with the top 10 infalls and develop recommendations for as many infalls as funding allows.

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