Solidification/Stabilization at the New Bedford Harbor Superfund Site, New Bedford, Massachusetts

Site Name:

New Bedford Harbor Superfund Site


New Bedford, Massachusetts

Period of

November 30 to December 4, 1995



- Bench-scale study of seven solidification/stabilization reagents from Foster Wheeler, MARCOR Environmental (MARCOR), and World Environmental (WORLD)
- Reagents included Foster Wheeler - Portland cement and absorbent clay; MARCOR - HWT-27 (a sintered calcium silicate material); and WORLD - LPC II (15% SiO2 and 68% CaO, similar to Portland cement), Clarion SM-399 (complex of montmorillonite clay and quaternary ammonium compound), Zoneco-P1 (mixture of some 30 organic and amino acids and other organic compounds), and OT-P2 (liquid containing 40% active alkoxysilane emulsified in water)
- Reagents were mixed with sediments (proportions and length of mixing times varied); the mixtures were placed in molds and allowed to air cure for 30 days

Cleanup Authority:
- ROD signed April 1990

Site Contact:
Helen Douglas
Foster Wheeler Environmental Corporation
470 Atlantic Avenue
Boston, MA 02210
Telephone: (617) 457-8263
EPA Contact:
James M. Brown
U.S. EPA Region 1 (MC HBO)
1 Congress Street, Suite 1100
Boston, MA 02114
Telephone: (617) 918-1308

- Maximum concentrations in sediments of more than 200,000 mg/kg

Waste Source:
Discharge of polychlorinated biphenyl (PCB)-contaminated wastewater from electronics manufacturing

Type/Quantity of Media Treated:
- Fine sandy silt with some clay-sized particles present; some small shell fragments present
- Moisture content - 50% by weight

Purpose/Significance of Application:
Bench-scale testing of solidification/stabilization to treat PCB-contaminated sediments

Regulatory Requirements/Cleanup Goals:
Objectives of the bench-scale study included evaluating the ability of solidification/stabilization to reduce the leachability of PCBs, SVOCs, and heavy metals in Hot Spot sediments
- Toxicity Characteristic Leaching Procedure (TCLP) regulatory limits for SVOCs and metals
- For TCLP PCBs, no regulatory limit had been established; therefore, results were used for comparison purposes only
- Compressive strength of treated material

TCLP PCBs - concentrations in all batches for the three vendors was found to be higher in the treated sediment than in the untreated sediment, by a factor of two to four times
- TCLP SVOCs - results were mixed, with concentrations generally higher in the treated sediment than in the untreated sediment; for example, TCLP concentrations for phenols increased in mixtures from all three vendors from 2 ug/L in the untreated sediment to as much as 4.7 ug/L in the treated material
- TCLP metals - concentrations in the untreated sediment used for these tests were below regulatory limits; in most cases, metals concentrations in the sediment were reduced by solidification/stabilization; however, increases in concentrations for several metals, including barium, copper, and zinc, were observed in some of the tests
- Compressive strength - the Foster Wheeler mixtures had the highest compressive strength, ranging from 195 to 270 psi; the MARCOR has the lowest compressive strength, ranging from 45 to 80 psi

Cost Factors:
No cost data were available for the treatability study; and no projections were developed for the full-scale costs for solidification/stabilization of Hot Spot sediments

The New Bedford Harbor Superfund Site is located along the northwestern shore of Buzzards Bay in New Bedford Massachusetts, approximately 55 miles south of Boston. From the 1940s to 1978, PCB-contaminated wastewater from electronics manufacturing operations was discharged onto the shoreline and into the harbor. Site investigations determined that sediments were contaminated with PCBs and heavy metals. The site was listed on the National Priorities List in September 1983. The ROD for a five acre area known as the "Hot Spot area" included dredging of PCB-contaminated sediments followed by incineration. However, due to opposition to incineration, EPA postponed the incineration component of the Hot Spot remedy to explore alternative treatment technologies. EPA evaluated four technologies as possible alternatives to incineration - solvent extraction/dechlorination, vitrification, thermal desorption/gas phase chemical reduction, and solidification/stabilization. This report covers the bench-scale testing of a solidification/stabilization process.

The bench-scale test was performed using seven reagents from three vendors - Foster Wheeler, MARCOR, and WORLD. The reagents were mixed with Hot Spot sediments (in varying proportions and mixed for varying times), placed in containers, and air cured for 30 days. Samples were analyzed for TCLP PCBs, TCLP SVOCs, and TCLP metals to evaluate the ability of solidification/stabilization to reduce the leachabiliy of contaminants from Hot Spot sediments. None of the solidification/stabilization mixtures tested during the bench-scale study was effective in stabilizing PCBs or SVOCs in the Hot Spot sediments. In many cases, the contaminant concentrations in the treated material were higher than in the untreated sediment. Specific reasons for the increase in concentrations were not identified, though it is possible that the process increased the mobility of PCBs and other organics in the aqueous phase. While the concentrations of metals in the untreated sediment were below the regulatory limits, solidification/stabilization generally reduced the TCLP metals concentrations in the treated material, and may be appropriate for treating metals in the Hot Spot sediments.