Soil Vapor Extraction
- 80 vapor extraction (VE) wells, 9 dual extraction (RD) wells, and 7 bedrock extraction wells connected to a central processing plant
- Depth of VE wells- <10 feet (approximate depth to bedrock)
- Vapors treated using activated carbon adsorption
- Water extracted using the RD wells was treated by air stripping and carbon polishing
- Design air flow rate- 15,000 scfm at 13 inches of mercury (Hg) vacuum
- More than 14 enhancements were made to the system including varying the number and types of wells, heating the soil using several techniques, destroying contaminants in situ, and physically creating new flow paths
- ROD date: 12/21/84
- Revised ROD: 3/31/88
- Revised ROD: 7/20/96
|Remedial Project Manager:|
SARA Special Site Section
U.S. EPA Region 3
841 Chestnut Building
Philadelphia, PA 19107
Ciba Specialty Chemicals Corp.
P.O. Box 71
Toms River, NJ 08754
Volatile Organic Compounds:
Spills and waste disposal in lagoons
Type/Quantity of Media Treated:
Soil - 30,000 cubic yards
Purpose/Significance of Application:
SVE application involving more than 14 enhancements
Regulatory Requirements/Cleanup Goals:
The ROD specified cleanup goals of 0.05 mg/kg each for 1,2,3-trichloropropane, benzene, trichloroethene, and tetrachloroethene.
In addition, the cleanup goals were to be achieved within 26 months after startup of the SVE system. If cleanup goals had not been met within the first year of operation of the SVE system, supplemental measures were to implemented to improve the vacuum extraction process.
- The system initially removed about 10,000 lbs/month of VOC. However, between September and December 1989, extraction rates decreased to 2,000 lb/month. In response, Terra Vac implemented 14 enhancements in an attempt to improve system performance.
- While many of the SVE system enhancements (varying the number and types of wells in the system, heating the soil, destroying contaminants in situ, and physically creating new flow paths as a means to improve the diffusion rate) produced short-term improvements in the extraction rate, in all cases, the results were only temporary. (The report includes a detailed summary of all enhancements and the results of each).
- Results of soil borings taken after 32 months of operation showed that concentrations of 1,2,3-trichloropropane, benzene, trichloroethene, and tetrachloroethene remained above the cleanup goals. In a number of cases, the constituent concentrations reported were higher than pre-remediation concentrations.
- EPA subsequently determined that the SVE system was incapable of meeting the cleanup goals in a timely and cost effective manner, and amended the ROD to change the remedy to a wet soil cover.
The total actual cost for the SVE system was $43.4 million, including approximately $3.5 million for design and pilot studies, and $39.9 million in treatment costs, including construction and operation and maintenance costs.
Tyson's Dump Superfund site is a four-acre, abandoned septic waste and chemical waste disposal site reported to have operated from 1960 to 1970 in a sandstone quarry. Franklin P. Tyson and Fast Pollution Treatment, Inc. used lagoons on the eastern and western portions of the site to dispose of industrial, municipal, and chemical wastes. Results of soil samples from the lagoons taken during the Remedial Investigation indicated the presence of VOCs at concentrations that exceeded 500 mg/kg. A ROD was issued in 1984, specifying excavation and off-site disposal of contaminated soils. In response to the results of a study submitted by the RPs, EPA negotiated a partial consent decree to implement SVE and issued a revised ROD in 1988.
The initial design of the SVE system at Tyson's Dump included 80 vapor extraction wells, nine dual extraction wells, and seven bedrock extraction wells connected to a manifold that led to a central processing plant. Most of the VE wells were drilled to a depth of less than 10 feet (approximate depth to bedrock). Extracted vapors were treated by activated carbon adsorption, with regeneration and solvent recovery on site. Water extracted using the dual extraction wells was treated by air stripping and carbon polishing. VOC extraction rates for the system initally were about 10,000 lb/month. However, by December of 1989 the extraction rate decreased to about 2,000 lbs/month. The results of additional investigations performed by Terra Vac identified several conditions at the site that were limiting the diffusion rate of VOCs and adversely impacting the performance of the SVE system, including greater variation in the permeability, porosity, particle size, and moisture content of the soils than identified during previous investigations. In addition, DNAPL was found to be present over a larger area of the site than had previously been identified. In response, Terra Vac implemented 14 enhancements in an attempt to improve system performance. Many of the SVE system enhancements produced short-term improvements in the extraction rate. However, in all cases, the results were only temporary. After 32 months of operation, sample results showed that concentrations of 1,2,3-trichloropropane, benzene, trichloroethene, and tetrachloroethene remained above the cleanup goals. EPA subsequently determined that the SVE system was incapable of meeting the cleanup goals in a timely and cost effective manner, and amended the ROD to change the remedy to a wet soil cover.