KEMRON completed a $24.5 million remedial action at the Southeastern Wood Preserving Superfund Site in Canton, Mississippi, a former wood-treatment facility impacted by creosote, pentachlorophenol, dioxins, and RCRA-listed hazardous wastes in soil, dissolved in groundwater and as a dense non-aqueous phase liquid (DNAPL). The project was performed for U.S. EPA Region 4 and included subsurface containment, contaminated soil excavation and management, engineered landfill construction, slurry wall installation, synthetic cap installation, stormwater controls, demolition, and site restoration.

A central component of the remedy was construction of a 3,030-linear-foot-cement-bentonite slurry wall around the most heavily impacted portions of the site. The 36-inch-wide wall extends approximately 40 feet below ground surface and is keyed into the underlying unweathered Yazoo Clay layer to create a low-permeability hydraulic barrier. KEMRON used a one-pass trencher to excavate and simultaneously mix the soil with Portland cement, bentonite, and water. Construction quality control included continuous monitoring of wall alignment and depth, as-built profiling, and testing for viscosity, density, and unconfined compressive strength.

The remedial action also required excavation, segregation, treatment, consolidation, and off-site disposal of multiple contaminated soil streams. Approximately 56,826 cubic yards of creosote-stained soil were excavated and consolidated within the on-site containment area, while approximately 6,070 cubic yards of dioxin-contaminated soil were transported off site for incineration. The remedial design also called for excavation and consolidation of approximately 87,750 cubic yards of creosote and highly contaminated subsurface soil and sediment and approximately 64,526 cubic yards of contaminated surface soil within the barrier wall.

KEMRON constructed an engineered containment cell within the slurry wall and installed a geosynthetic clay liner and ClosureTurf® final cover system over approximately eight acres. The cap incorporates a subsurface gas-venting system and was integrated with final grading, clean backfill, vegetative cover, and erosion-control measures to reduce infiltration and provide long-term protection of the contained waste.

Stormwater management was an integral part of the project and included retention and drainage features, riprap, silt fencing, diversion structures, and temporary control of Batchelor Creek to support excavation and barrier-wall construction.

One of the project’s most challenging activities involved demolition of a 50-foot-tall reinforced concrete former woodchip mixer located approximately 25 feet from a public roadway and near overhead powerlines. Conventional excavator demolition posed unacceptable risks from falling concrete and limited equipment reach.

KEMRON developed a remote demolition solution using a BROKK 120D robotic hammer mounted on a custom-fabricated steel platform and supported by a CAT 1255 telehandler. Operators controlled the BROKK remotely from outside the structure’s fall zone while the concrete roof and upper walls were systematically demolished inward. Once the structure was reduced to a safe height, conventional excavators completed demolition. The operation was completed without an unplanned risk event involving workers or the public.