ENVIRONMENTAL DREDGING PILOT ON THE LOWER PASSAIC RIVER: ONE OF AMERICA'S MOST POLLUTED RIVERS

摘要

As part of the Lower Passaic River Restoration Project, an environmental dredging pilot study was implemented in December 2005 to evaluate remedial dredging of contaminated sediments from the Lower Passaic River in New Jersey. The dredging pilot was led by NJDOT along with the USACE and USEPA.rnApproximately 5,000 cubic yards (cy) [3,825 m~3] of contaminated sediment were dredged from a 1.5 acre [6,070 m~2] area in 10 to 15 feet [3.0 to 4.6 m] of water at an average rate of 830 cy [635 m~3] per 10-hour workday using an eight (8) cy [6.12 m~3] Cable Arm® mechanical clamshell dredge bucket. The dredge bucket was equipped with sensors for bucket positioning and monitoring bucket closure. The results of a comprehensive monitoring program to evaluate near-field and downstream transport of the contaminated sediment are documented in a separate manuscript (Bilimoria et al., 2006).rnOne of the pilot study objectives was to determine a reasonable production-rate for remedial dredging. The specifications required a vertical dredging accuracy of +/- 6 inches [15 cm]. Design techniques and other nuances of the dredging design are presented. In general, the average daily cycle times ranged from 1 3/4 to 2 3/4 minutes. A rinse tank was used to clean the dredge bucket between each cycle. Numerous variables, and their effects on sediment resuspension and transport, were tested during the study, including:rn1. Dredging cycle time;rn2. Depth positioning technique (depth transducers vs. measuring chain);rn3. Equilibration holding time (i.e., length of time the bucket was held in position at the water surface to allow for pressure equilibration); andrn4. Number of lifts per dredging area.rnThe dredged material was transported to a near shore processing facility for treatment by two innovative decontamination technologies (a sediment washing process and a thermo-chemical destruction process using a rotary kiln) to make beneficial use end products.