The facility is situated on a small knoll, with small hills, valleys, and streams throughout the area. The site is located in the Valley and Ridge Physiographic province, which contains folded and faulted sedimentary rocks. The Liberty Hall rock formation lies beneath the site and contains interbedded dark gray to black slatey mudstone and medium- to coarse-grained bioclastic limestone. The bedrock in the area is covered by yellow-reddish clay and silt that range in thickness from 6 to 15 feet. The bedrock and overlying area of clay and silt serve as water-bearing zones. Groundwater movement throughout the clay and silt zones is primarily through the pore spaces along the saprolitic features; groundwater in the bedrock flows through existing fractures. The clay and silt exhibit a thin zone of saturation, making the bedrock the suitable location for bioremediation.

• Fractured Bedrock

VOC migration occurs in the bedrock fractures in the south and southeast.

• Trichloroethene (0 µg/L)
• 1,1,1-Trichloroethane (0 µg/L)
• 1,2-Dichloroethane (0 µg/L)
• Vinyl chloride (0 µg/L)
• Chloroethane (0 µg/L)
• Acetone (0 µg/L)
• Isopropyl alcohol (0 µg/L)

• Borehole Geophysics
  • Acoustic Televiewer
• Pumping Tests
• Other (Helium/Pressure Readings)

Comments:
A pilot test was completed in one of the three on-site contaminant source zones. Air was injected for 6 weeks until limited nutrient availability was found from the groundwater monitoring data in conjunction with the U.S. Environmental Protection Agencys (EPA) Superfund Innovative Technology Evaluation (SITE) Program. An air and nutrient injection phase was completed over a period of 10 weeks. Results of the injection indicated a reduction in the concentration of methane. Methane, air, and nutrients were then injected throughout the full-scale operation. The objective of the pilot-scale test was to reduce concentrations of volatile organic compounds (VOCs) in groundwater.

• Other (Cometabolic methanotrophic bioremediation)

The long-term goal of the full-scale project was to reduce overall concentration of VOCs in groundwater by targeting the deeper fractures at the site. These deeper fractures were targeted to allow the injected amendments to reach a larger area and to achieve drinking water standards if feasible.

The bioremediation system at Building 3 operated from January 2000 for four years. The full-scale system was applied in three source areas and contained three more injection wells than the pilot-scale test. Each injection was applied at two depths at each well. The injection depths were approximately 50 and 80 feet below ground surface (bgs). The first injection was completed at 12 pounds per square inch and 30 standard cubic feet per hour. The injections produced amendment delivery to shallow factures and to the clay overburden area (15 to 30 bgs). The first source area where the technology was applied to showed 99 to 99.96 percent reductions in the concentration of VOCs in the source area and in some of the downgradient monitoring wells. The concentration of VOCs in a few of the monitoring wells remains above drinking water standards despite the 4-year duration of the remedial effort. The second source zone had shown levels of acetone and isopropanol below detection limits after 3 months. The third source zone showed a 90 percent reduction in concentrations of chlorinated hydrocarbons and increased microbial populations.

References: Carter, Gregory L., Tiffany M Dalton, Barbara B. Lemos, and Rosann Kryczkowski. Gaseous Nutrient Delivery in Fractured Rock For Cometabolic Bioremediation. Paper A-41. In Situ and On-Site Bioremediation-2003. The Seventh International In Situ and On-Site Bioremediation Symposium (Orlando, Florida). June 2003.

Carter, Gregory L., Tiffany M Dalton, Barbara B. Lemos, and Rosann Kryczkowski. Case History for Treating Contaminated Groundwater with Cometabolic Methanotrophic Bioremediation. Paper A-42. The Seventh International In Situ and On-Site Bioremediation Symposium (Orlando, Florida). June 2003.