ENTACT was contracted by the PRP group to perform the multi-faceted remediation of former waste oil pits situated in a cypress swamp. The swamp was influenced by a nearby a tidal tributary of the Atlantic Ocean creating a highly saturated work zone. Initial remedial activities required the relocation of a half-mile of the primary swamp channel to divert existing flow away from the waste oil pits. ENTACT then performed in-situ stabilization on 45,000 cubic yards of hydrocarbon contaminated pit sludges to immobilize VOCs, SVOCs, PCBs, and metals. Another major aspect of the project was the construction of a 3,100 linear foot perimeter soil-bentonite slurry wall to prevent the infiltration of groundwater into the treated waste. The wall had a vertical installation depth of 80 ft below ground surface (bgs).
ENTACT encountered and adapted to the unique challenges posed by installing a slurry wall in the brackish subsurface conditions found near the ocean. Salt impacts deriving from the groundwater, submerged sediments, and saturated zone soils contributed to significant slurry degradation, necessitating a change from bentonite to a salt water resistant mud (SW101) and eventually attapulgite to prevent the loss of slurry.
Additional aspects of the project included the construction of an 11.5-acre RCRA compliant capping system over the entire site; installation of an extensive underdrain network to serve as a stormwater collection system; installation of a gas collection system; and final site restoration.
ENTACT was engaged by a developer to perform remediation activities under the NJDEP Voluntary Cleanup Program to prepare an industrial site for residential redevelopment. The scope of the remedial effort at this site entailed the removal of chromate ore processing residue (COPR). Site activities included excavation, characterization, management, and off-site disposal of 22,000 tons of chromium impacted soils; installation of a capillary break liner system; construction of a bentonite slurry groundwater cut-off wall; UST removal, and site restoration and backfill. ENTACT performed all excavation, load out and backfill activities under a portable containment structure.
ENTACT performed the slurry wall installation on a design-build basis using imported clay and bentonite fines to design and install a groundwater barrier with a permeability of less than 1 x 10-7 cm/sec. Design components included work platform slope stability, slurry trench stability, development of the complete mix design, work plan development, regulatory negotiation, and professional engineering certification. Construction activities included trenching, mixing and pumping slurried bentonite, and backfilling. ENTACT was also responsible for QA/QC on the cut-off wall (including slump tests, viscosity, filtrate loss, gradation, and hydraulic conductivity), the generation of as-built drawings, and submittal of the Final Report to the NJDEP.
