During due diligence assessment, soil and groundwater impacts were identified beneath the building slab at two discrete locations. Chlorinated volatile organic compounds (CVOCs), or dry-cleaning solvents, including tetrachloroethylene (PCE) and trichloroethylene (TCE), were identified above MassDEP Reportable Concentrations (RCs). The extent of CVOC impacts were isolated, based on the presence of dense till with a high clay content located beneath shallow urban fill soils. Site redevelopment plans include removal of the existing building and mixed commercial and residential redevelopment.
To facilitate redevelopment of the site for unrestricted residential use without the need for an Activity and Use Limitation, in situ chemical oxidation (ISCO) was chosen as the preferred method for destruction of CVOCs in soil and groundwater. EBI contracted XDD Environmental (XDD) to perform bench scale testing in the two treatment zones, in order to determine the soil oxidant demand and select the ISCO reagent. The bench test indicated that potassium permanganate would we be most effective oxidant, based on the soil oxidant demand and desired longevity of residual oxidant (one year of post-application reactivity).
EBI prepared a Release Abatement Measure (RAM) Plan for ISCO treatment of CVOCs using potassium permanganate as the oxidant. Evaluation of several application methods were evaluated to determine the most effective method of delivering the oxidant to impacted media. Soil mixing, using a drum rotary mixing head, was selected, based upon soil conditions. Soil mixing technology using a rotary mixing head effectively agitates soils, creating a homogeneous treatment area, where the oxidant is mechanically introduced to soil and groundwater. Traditional pressure injection, where the oxidant is pressure injected through direct push tooling, has shown limited success in tight till and clay formations, due to low soil porosity and limited dispersion of the oxidant to target treatment areas.
EBI conducted monthly groundwater gauging, soil vapor monitoring, indoor air monitoring, and quarterly groundwater sampling for the ongoing project. Preliminary data indicated that remedial efforts were effective in reducing CVOC concentrations in groundwater within the treatment zones.
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