Remediation of the New Bedford Harbor Superfund Site
Steve Wolf, ENSR, Westford, MA

Excavation of PCB-Contaminated Sediment Adjacent to the Intake of a 12-MGD Drinking Water Plant
Bryan R. Maurer, Cummings/Riter Consultants, Inc., Pittsburg, PA

Effectiveness of in situ Cement Stabilization for Remediation of Sediment Containing Coal Tar Derived Hydrocarbons
Chris Leuteritz, Anchor Environmental, LLC, Andover, MA

Monitoring the Uplift of a Low-Permeability Sediment Cap Due to Gas Entrapment Beneath the Cap: Findings of the First 18 Months
Robert D. Mutch Jr., HydroQual, Inc., Mahwah, NJ

Optimization of PCB Dechlorination by Palladized Magnesium in Marine Sediments
Irina Calante, University of New Hampshire, Durham, NH

Excavation of PCB-Contaminated Sediment Adjacent to the Intake of a 12-MGD Drinking Water Plant

Bryan R. Maurer, P.E., Cummings/Riter Consultants, Inc., 10 Duff Road, Suite 500, Pittsburgh, PA, 15235, Tel: 412-241-4500, Fax: 412-241-7500, Email: bmaurer@cummingsriter.com.

The ROD for the former Westinghouse plant in Sharon, Pennsylvania issued in February 2003 included the removal of approximately 4,000 CY of PCB-contaminated sediment from several locations along the Shenango River to a cleanup goal of 1.0 mg/kg.  Delineation sampling indicated a maximum total PCB concentration of about 400 mg/kg, although 97% of the sediment samples were less than 50 mg/kg, and 88% of the samples were less than 10 mg/kg.  Remediation planning was complicated by the presence of a 12 MGD drinking water plant with a surface intake less than 200 feet from the remediation areas, along with an active 24-inch cast iron water line crossing the river underneath the riverbed.  Given the water depth and composition of the riverbed, as well as potential flow velocities during high flow periods, it was determined that the best means of protecting the water plant intake during the remediation would be to isolate the excavation areas using sheet piling, with placement of silt screens around the intake as well as downstream of the pile installation areas.  In addition, a mobile laboratory was brought on site to provide rapid analysis of surface water samples at quantitation limits of 0.05 ug/l, in order to provide reassurance to all interested parties that the water supply would not be impacted by the work.

Remediation commenced in summer 2004, and to date, more than 800 surface water samples have been collected downstream of active work areas, including more than 300 samples collected directly from the water plant intake.  No PCBs have been detected in any of the water samples collected from the intake, and only five other samples collected downstream of work areas were found to contain PCBs (up to 0.26 ug/l).  The sediment remediation, delayed by Hurricanes Frances and Ivan, is expected to be completed in spring 2005.

Effectiveness of in situ Cement Stabilization for Remediation of Sediment Containing Coal Tar Derived Hydrocarbons

Todd Thornburg, Anchor Environmental, L.L.C., 6650 SW Redwood Lane, Suite 110, Portland, OR, 97224, Tel: 503-670-1108, Fax: 503-670-1128, Email: tthornburg@anchorenv.com
Chris Leuteritz, Anchor Environmental, L.L.C., 2 Dundee Park, Suite 102, Andover, MA 01810, Tel: 978-474-9090, Fax: 978-474-9080, Email: cleuteritz@anchorenv.com
David Templeton, Anchor Environmental, L.L.C., 1423 Third Avenue, Suite 300, Seattle, WA, 98101, Tel: 206-287-9130, Fax: 206-287-9131, Email: dtempleton@anchorenv.com
Tim Metcalf, Honeywell International Inc., 101 Columbia Road, Morristown, NJ, 07962-1139, Tel: (973) 455-4107, Fax: (973) 455-3082, Email: tim.metcalf@honeywell.com
Tracey Bell,  KeySpan Energy, One Metrotech Center, 15th Floor, Brooklyn, NY  11201-3850, Tel: (718) 403-3053, Fax: (718) 222-1546, Email: tbell@keyspanenergy.com
Kurt Paschl,  Beazer East, Inc., One Oxford Centre, Suite 3000, Pittsburgh, PA, 15219-6401, Tel: (412) 208-8863, Fax: (412) 208-8869, Email: paschlk@hansonle.com

Sediments adjacent to a former coal tar processing facility are associated with intermittent releases of hydrocarbon droplets and sheen to the overlying marine water column, particularly during low tide.  In situ sediment stabilization with Portland cement was one of the alternatives considered for a response action to control sheen in accordance with Surface Water Quality Standards.  The remedial design concept consisted of driving large-diameter caissons through the sediment and into the underlying clay aquitard, mixing Portland cement inside the caissons (approximately 15 percent by weight) using an auger or similar piece of equipment, and removing minor amounts of surficial sediment that had bulked up above the original mudline. The caissons would then be pulled, offset in a systematic overlapping pattern, and the process repeated until the sheen-producing area had been stabilized.

Bench-scale laboratory testing was conducted on composite samples of both untreated and stabilized sediments from the area to better characterize the effectiveness of cement stabilization for controlling sheen.  The bench-scale tests included the Sequential Batch Leaching Test (SBLT), a U. S. Army Corps of Engineers protocol (Myers et al., 1992) that simulates the effects of contaminated sediment on pore-water chemistry, and a more qualitative Static Sheen Test, per USEPA (40 CFR Chapter 1, Part 435).  Tests were conducted on sediments treated with 10, 15, and 20 percent dry cement, 15 percent cement slurry, and, for comparison, 10 percent organoclay, a hydrocarbon adsorbent.  Sediment mixtures were allowed to cure for seven days before testing. 

The bench-scale test results indicate in situ stabilization as a stand-alone technology would not be effective at controlling sheen; the response action would require additional components, such as the addition of a thick cap or placement of sediments in a confined disposal facility, to achieve this objective.  Even the most effective stabilization mixtures leached polycyclic aromatic hydrocarbons (PAHs) and mid-range aromatic and aliphatic hydrocarbons at concentrations well above their effective solubilities, indicating a strong tendency for continued sheen production.  Performing the appropriate bench-scale tests cost-effectively demonstrated the need for a different approach to designing and implementing an effective remedial solution for this site. 

Monitoring the Uplift of a Low-Permeability Sediment Cap Due to Gas Entrapment Beneath the Cap: Findings of the First 18 Months

Robert D. Mutch, Jr., P.Hg., P.E. (MSCE) and Egon Weber, Ph.D., HydroQual, Inc., 1200 MacArthur Blvd., Mahwah, NJ 07430, Email: rmutch@hydroqual.com
Daniel Kearney, P.E. (MSCE), Brown and Caldwell, Inc., 100 Commerce Drive, Allendale, NJ  07456, Email: dkearney@brwncald.com

The Hazardous Substances Research Center (HSRC), in conjunction with Battelle, Horne Engineering, and HydroQual, Inc., is conducting a major field study of “active” sediment caps on the Anacostia River near Washington, DC. As a part of this overall study, the potential uplift and deformation of low-permeability sediment cap constructed with AquaBlok^TM is being studied using highly sensitive, in-place horizontal inclinometers. The potential for low permeability sediment caps to be uplifted by increases in sediment pore pressures due to the designed restriction of groundwater discharge caused by the cap or by transient tidal fluctuations has been shown to be significant in some riverine and estuarine settings. Uplift could potentially cause cracking and jointing of the low permeability cap substantially increasing its hydraulic conductivity and, consequently, compromising the cap’s ability to restrict contaminant flux.

The research project involves construction of several pilot scale sediment caps. One such pilot scale sediment cap consists of six inches of AquaBlok^TM overlain with six inches of sand. A 100-foot long horizontal inclinometer casing was constructed within the 100 by 80 foot pilot-scale cap overlying the AquaBlok^TM.  A string of ten in-place horizontal inclinometers is housed in the casing and has been measuring uplift or deformation of the cap since March 26, 2004. The data have recorded initial settlement of the cap due to sediment consolidation. Following initial settlement, the further offshore portion of the cap began to slowly uplift a total of about one inch over a period of 40 days before suddenly uplifting more than two feet. Uplift events of similar magnitude occurred intermittently throughout the summer and early fall of 2004. Initial indications point to instability caused by a buildup of decomposition gas from the sediments under the cap. Bathymetric surveys have revealed that the cap is thinner in the area of observed instability. The cap has been relatively dormant during the late fall and winter likely corresponding to declining temperatures and concomitant reductions in gas generation. Monitoring will continue throughout 2005 to observe whether a renewed cycle of uplift events occurs when temperatures rise again in the spring and summer.

Optimization of PCB Dechlorination by Palladized Magnesium in Marine Sediments

Irina Calante, University of New Hampshire, 330 Gregg Hall, 35 Colovos Rd., Durham, NH, 03824, Tel: 603-862-1197, Fax: 603-862-3957, Email:  Icalante@unh.edu
Kevin H. Gardner, University of New Hampshire, 336 Gregg Hall, 35 Colovos Rd., Durham, NH, 03824, Tel: 603-862-4334, Fax: 603-862-3957, Email:  Kevin.Gardner@unh.edu
Jeannie C. Spear, University of New Hampshire, 222 Gregg Hall, 35 Colovos Rd., Durham, NH, 03824, Tel: 603-862-1445, Fax: 603-862-3957, Email:  Jeannie.Spear@unh.edu
Emese Hadnagy, University of New Hampshire, 330 Gregg Hall, 35 Colovos Rd., Durham, NH, 03824, Tel: 603-862-1197, Fax: 603-862-3957, Email:  Ehadnagy@unh.edu

Currently, marine sediments contaminated with Polychlorinated Biphenyls (PCBs) are treated ex-situ through dredging followed by landfill.  This form of treatment can be very costly, has high impacts on the marine environment, and can further disturb and disperse PCBs from the sediments. Capping and monitored natural recovery are two other viable options, both of which suffer from leaving contamination in place. This research focuses on the optimization of in-situ treatment of marine sediments contaminated with PCBs by dechlorination with palladized magnesium.  Three sediments (New Bedford Harbor, MA, Housatonic River, MA, and Hudson River, NY) have been tested for dechlorination with palladized magnesium (4 mm magnesium particles coated with 0.1% by weight palladium).  High PCB removals were observed for sandy sediments with low organic carbon content, whereas lower removals where seen for sediments with higher organic carbon content.  Desorption experiments using Tenax beads were conducted to see whether PCB desorption from sediment was a rate limiting step for dechlorination.  Sediment characteristics such as PCB concentration, organic carbon content, particle size distribution and water content are being used to optimize the percent addition of palladized magnesium to each sediment.  A study will also be conducted to see how well the solvent d-Limonene extracts PCBs from the sediment and makes them available to react with the palladized magnesium.  The results from these studies will be presented. 

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