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New Jersey Water Science Center
Great Falls of the Passaic River at Paterson, N.J.
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Determining Loads of Sediment and Chemicals-of-Concern at the Dundee Dam, Passaic River, Patterson, New Jersey
Project Title: Determining Loads of Sediment and Chemicals-of-Concern at the Dundee Dam, Passaic River, Patterson, New Jersey
Statement of Problem
The NY/NJ CARP program attempted to determine the loads of dissolved and sediment bound contaminants of concern that entered the Newark Bay through the Passaic and Hackensack Rivers. Towards this goal, a sampling station was established on the Passaic River at the Passaic Valley Water Commission Plant located at Little Falls, NJ. This station is located adjacent to the US Geological Survey (USGS) gaging station, where the discharge of the Passaic River has been monitored for nearly 100 years. This sampling station worked well for the CARP program, producing samples needed for estimating sediment and chemical loads leaving the Passaic River basin. However, the site is located upstream of a waterfall, the city of Paterson, NJ and the large impoundment (Dundee Lake) behind the Dundee Dam. As a result, the loads determined in the CARP program may not accurately represent the loads that actually enter the saline Passaic River estuary. Accurate load information is required for the ongoing efforts to model sediment and contaminant transport in the estuary, and to evaluate and/or monitor cleanup/remediation efforts.
This proposed work will develop a water discharge monitoring station, estimate loads of sediment, and measure concentrations and estimate loads of dissolved and sediment bound PCBs, dioxin/furans, PAHs, and selected metals that are transported across the Dundee Dam into the saline Passaic River estuary.
Strategy and Approach
The USGS recently proposed to the USEPA a sampling program to determine the sediment loads crossing the Dundee Dam (figure 1). In that work, samples were to be collected for from the Ackerman Avenue bridge for analysis of suspended sediment and particulate organic carbon. The previous proposal also describes the installation and calibration of a water-discharge monitoring (gage) station at the dam. The approach taken in this proposal combines efforts to remove redundancy, and to collect/analyze a minimum of samples required to produce a lower limit of accuracy in load estimates.
Regardless of sampling scheme ultimately used, the first step will be to install and calibrate a water discharge gaging station at the dam. This station will provide real-time information on the volume of water flowing over the Dundee Dam, information critical to this work and to other work being performed on the Passaic estuary.
Once the gage station has been installed and stage-discharge calibration begun, sampling of low-flow and storm events will begin using equal width interval (EWI) sampling. EWI sampling produces a single “instantaneous” composite grab sample, thereby producing an estimated average concentration of sediment/water at a point in time during the rising limb of the hydrograph. Sampling will be conducted from the Ackerman Avenue bridge using a bridge crane and a weighted sampler. In the EWI method, the river is sectioned off into 10-15 intervals of equal width. At each interval, three vertically integrated grab samples will be collected, with all sampling being completed during the rising limb of storm discharge (likely taking 2 to 3 hours to complete). Samples for low-flow events will be collected only when water is flowing downstream and not being affected by the rising tide. The first sample from each interval will be poured into a large (25 gallon) conically shaped stainless steel vat, from which the sediment and dissolved phases will be separated using a TOPS sampler. The second sample from each interval will be composited and analyzed for suspended sediment, carbon (required for calculating chemical concentrations in the sediment phase) and for trace metal content. A third sample will be collected and either archived or analyzed as a discrete sample (for suspended sediment) to help demonstrate cross- sectional mixing at different flow regimes.
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