MD002 – Ferox™
Federal Facility, Maryland
Figure 1: Federal Facility, Maryland
ARS’ Ferox™ Technology was applied at Site 13 of the former Naval Surface Warfare Center (NSWC) in White Oak, Silver Spring, Maryland to treat a TCE-contaminated saprolite formation.
The primary goal of this remedial action was to reduce contaminant levels in the areas of greatest contamination within Site 13. The VOCs of concern were identified as 1,1,2,2-PCA, cis-1,2-DCE, PCE, TCE and vinyl chloride. The total VOC concentrations have been detected at levels greater than 1,000 ug/liter in the groundwater.
The project was completed during the winter of early 2005. More than 77,000 lbs. of the H-200 Zero-Valent Iron (ZVI) powder were injected via 15 boreholes from approximate depths of 12-35 ft. bgs. The injection boreholes were spaced approximately 50 ft. apart within a 13,000-sq. ft. treatment area. Pneumatic Fracturing (PF) was applied when necessary to facilitate the emplacement of the ZVI powder using ARS’ proprietary Atomized Liquid Injection (ALI) technique.
Pneumatic Fracturing was required in roughly 58% of the injection intervals, typically toward the deeper half of the boreholes into more competent saprolite. Fracture initiation pressures ranged from 50 to 400 psi and maintenance pressures ranged from 40-210 psi. PF events occurred with greater frequency at the deeper injection intervals. ALI injection of the H-200 was performed under pressure ranging from 50-140 psig.
The field application of PF and Ferox™ demonstrated the effectiveness of these technologies as a means of enhancing permeability and as an effective delivery technique for the emplacement of ZVI into the subsurface.
Figure 2: Federal Facility, Maryland
Five days after injection, reducing conditions were evident in the injection area by the increase in pH (from 4.85 to 7.18) and the decrease in oxidation-reduction potential (ORP) (from 294 mV to -290 mV). Reducing conditions continued in the treatment area one month (pH of 7.27 and ORP of -184 mV), two months (pH of 6.74 and ORP of -185 mV), and three months (pH of 7.18 and ORP of -271 mV) after injection of ZVI.
Contaminant concentrations in the treatment area showed significant decreases immediately after the fracturing and injection. The 1,1,2,2-Tetrachloroethane (PCA) concentration in the remediation area dropped from 700 μg/L to 130 μgL (5 days after the injection), and then to 110 μg/L (1 month after the injection) and 51 μg/L (3 months after the injection). Similarly, the trichloroethylene (TCE) concentration in the remediation area dropped from 150 μg/L to 22 μgL (5 days after the injection), and to 17 μg/L (1 month after the injection) and 8 μg/L (3 months after the injection).
The positive outcome from this Ferox™ application has led to an expanded implementation to a larger area including part of an adjacent private property.