Soil Vapor Extraction (ex situ)
- In situ SVE was not used because of low soil permeability
- Soil was excavated on a grid basis
48 grids were excavated, each 10x10 ft square
- Treatment was conducted in metal building 60 ft wide by 120 ft long by 26 ft tall
- System included shaker (power) screen, 17 horizontal vapor extraction wells, 3 vacuum pumps, a baghouse, and a thermal oxidizer
Organic Compounds (Volatiles - Halogenated: trichloroethene (TCE); and Volatiles - Nonhalogenated: toluene, methyl isobutyl ketone (MIBK), and methyl ethyl ketone (MEK)) and Inorganic Compounds (Heavy Metals: lead and mercury)
- Toluene: BDL-220,000 mg/kg
- MIBK: BDL-66,000 mg/kg
- MEK: BDL-23,000 mg/kg
- Actual costs of $2,200,000 were expended, including $1,300,000 for before-treatment activities, $660,000 for activities directly attributed to treatment, and $220,000 for after-treatment activities
- The unit cost for activities directly attributed to treatment was $413/yd3 of soil treated ($275/ton), and $9.20/lb of VOC removed
Basket Creek was used in the 1960s for illegal disposal of liquid refinery and other hazardous wastes. In 1991, soil at the site was identified as a RCRA hazardous waste exhibiting the Toxicity Characteristic (TC) for lead, MEK, and TCE. Soil samples collected in March 1990, May 1991, and January 1992 showed the following concentrations in a total waste analysis: TCE - below detection limit (BDL) to 8,600 mg/kg; PCE - BDL to 2,700 mg/kg; toluene - BDL to 220,000 mg/kg; xylenes - BDL to 7,300 mg/kg; MEK - BDL to 23,000 mg/kg; and MIBK - BDL to 66,000 mg/kg.
An action memorandum for Basket Creek was signed on April 11, 1991 and specified soil treatment targets for TCE, PCE, benzene, MEK, lead, mercury, and total halogenated organic compounds (HOCs). An ex situ SVE system was used at Basket Creek, consisting of a 7,200 ft2 containment building, a shaker (power) screen, 17 vapor extraction wells, vacuum pumps, a baghouse, an induced draft blower, and a thermal oxidizer. Excavation, screening, and vapor extraction all took place inside the containment building. The system was run from November 1992 to February 1993, and again from March to April 1993, for a total of 6 months of operation.
Analytical data indicated that the soil treatment targets were met for all contaminants after the six month treatment period. Total VOCs in the treated soil ranged from 0.142 to 1570.7 mg/kg, and approximately 72,000 lbs of total VOCs were recovered from the soil. Toluene was the largest quantity VOC recovered, accounting for approximately 80% of the total VOCs recovered, and MIBK was the second largest quantity, accounting for 11%. Ex situ SVE was selected for this application after in situ SVE was ruled out because of the low permeability of the contaminated soil. Excavation of soil was performed within an enclosure to control emissions. Because of space constraints, this resulted in the excavation taking a much longer time (3 months) than would have been required were the excavation to have been done outside (a few days).