DEVELOPMENT AND EVALUATION OF SCENARIOS FOR NON-TIDAL PASSAIC RIVER NUTRIENT TMDL

The technical basis for establishing TMDLs to address phosphorus impairments in the non-tidal Passaic River Basin is presented. The non-tidal Passaic River basin encompasses an 810 square mile watershed in northern New Jersey. Extensive monitoring throughout the Passaic River Basin was performed from May through November of 2003, and additional monitoring was performed during Summer of 2004, in order to identify existing and potential water quality impairments due to nutrients, to characterize nutrient sources, and to obtain adequate data to calibrate a comprehensive basin-wide water quality model. Water quality targets (e.g. dissolved oxygen criteria) were defined to solve or prevent nutrient impairments at critical locations in the streams. Additional water quality targets were defined at potable water intake locations that provide water to reservoirs or directly to water treatment plants based on acceptable loading rates to those water bodies and facilities. A model to simulate water quality variables of interest, such as phosphorus and dissolved oxygen, was developed using the Water Quality Analysis Simulation Program 7 (WASP7) that accounts for the impact of aquatic plants and periphyton. The time frame of the model includes four consecutive years (October 1999 through November 2003) that represent normal, dry, extreme drought, and wet years. The resultant watershed model relates nutrients from various sources to water quality variables such as dissolved oxygen in order to assess the impact of various pollutant sources under different environmental conditions on water quality targets at critical locations throughout the watershed.Using the watershed model, a number of different nutrient reduction scenarios will be tested under a variety of conditions during the simulation period. The methodology specifically accounts for point source trading by developing source weighting factors upstream of critical locations. Wasteload allocations for point sources and load allocations for nonpoint sources will be established to satisfy water quality targets at all critical locations and will form the basis for the watershed-specific criteria and TMDL for the non-tidal Passaic River basin. Ultimately, the evaluation of future scenarios for a watershed-wide nutrient TMDL is used to focus nutrient reduction efforts toward real water quality improvements.