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IN-SITU VACUUM EXTRACTION PROJECTS:
10. TPVE IN CLAYEY SOIL AND FRACTURED BEDROCK

Confidential Client, New Jersey

Two tank farms that had been in service since the 1940's were the sources of releases of volatile organic compounds to the soil, fractured bedrock and groundwater at this major manufacturing facility. The site is underlain by the Brunswick formation, which is composed of red shale and siltstones and is characterized by dipping bedding planes and vertical jointing. The hydrologic characteristics of the upper part of the formation include low groundwater yield and unpredictable flow patterns. These characteristics pose difficulties for remediation. The subsurface included a shallow, poor-yielding zone with elevated VOC levels, and a deeper, higher yielding fracture system with somewhat lower VOC concentrations. For the deeper zone, a groundwater extraction was designed with treatment by air stripping and carbon polishing. The treated water was used as non-contact cooling water prior to discharge to the local sewer authority, resulting in decreased use of the public water supply. This approach made it possible for the authority to accept the discharge despite a regulatory climate in which treatment of contaminated groundwater was discouraged. The groundwater plume was completely controlled by pumping 15 gpm from 120 feet, however, less than 100 pounds total VOCs were removed in a year of pumping. In 1992, a pilot test of two-phase vacuum extraction (TPVE) was conducted in soil and shallow (10 to 70 feet below grade) bedrock groundwater. The results of the test included:

• The yield of groundwater from the shallow clayey soil in the tank farms increased from ~0 to 0.5 gpm
• The vacuum radius of influence was from 10 to 30 feet in the overburden. The shallow bedrock water yield increased from ~0 to 2.6 gpm.
• The entire shallow bedrock plume was captured from one well.
• More than 1000 pounds of hydrocarbons were removed from the overburden in one week.
• More than 80 pounds total VOCs (primarily TCE, TCFM) were removed in one day from shallow bedrock.
• Ninety-nine percent of the VOCs were removed from the extracted water by vacuum stripping.

Based on these results, a remedial action plan that included continued control of the deeper plume by pumping and treating and cleanup of the source areas in the soil and shallow fractured bedrock by the application of TPVE was approved by the New Jersey Department of Environmental Protection. Final design work is underway.