HUGHES ENVIRONMENTAL SYSTEMS, INC.

(Steam Enhanced Recovery Process)

TECHNOLOGY DESCRIPTION:

The Steam Enhanced Recovery Process (SERP) removes most volatile organic compounds (VOC) and semivolatile organic compounds (SVOC) from perched groundwater and contaminated soils both above and below the water table (see figure below). The technology is applicable to the in situ remediation of contaminated soils below ground surface and below or around permanent structures. The process accelerates contaminant removal rates and can be effective in all soil types.

Steam is forced through the soil by injection wells to thermally enhance the recovery of VOCs and SVOCs. Extraction wells are used for two purposes: to pump and treat groundwater, and to transport steam and vaporized contaminants to the surface. Recovered nonaqueous liquids are separated by gravity separation. Hydrocarbons are collected for recycling, and water is treated before being discharged to a storm drain or sewer. Vapors can be condensed and treated by any of several vapor treatment techniques (for example, thermal oxidation and catalytic oxidation). The technology uses readily available components such as extraction and monitoring wells, manifold piping, vapor and liquid separators, vacuum pumps, and gas emission control equipment.

WASTE APPLICABILITY:

The SERP can extract VOCs and SVOCs from contaminated soils and perched groundwater. Compounds suitable for treatment are petroleum hydrocarbons such as gasoline and diesel and jet fuel; solvents such as trichloroethene, trichloroethane, and dichlorobenzene; or a mixture of these compounds. After application of the process, subsurface conditions are excellent for biodegradation of residual contaminants. The process cannot be applied to contaminated soil very near the ground surface unless a cap exists.

STATUS:

This technology was accepted into the SITE Demonstration Program in 1991. The demonstration of the technology began in August 1991 and was completed in September 1993. The demonstration took place in Huntington Beach, California at a site contaminated by a large diesel fuel spill. The Demonstration Bulletin (EPA/540/MR-94/510), Technology Capsule (EPA/540/R-94/510a), and Innovative Technology Evaluation Report (EPA/540/R-94/510) are available from EPA.

For more information regarding this technology, see the profiles for Berkeley Environmental Restoration Center (completed projects) or Praxis Environmental Technologies, Inc., in the Demonstration Program section (ongoing profiles).

This technology is no longer available through a vendor. For further information on the technology, contact the EPA Project Manager.

DEMONSTRATION RESULTS:

Evaluation of the posttreatment data suggests the following conclusions:

• The geostatistical weighted average for total petroleum hydrocarbon (TPH) concentrations in the treated soils was 2,290 milligrams per kilogram (mg/kg). The 90 percent confidence interval for this average concentration is 996 mg/kg to 3,570 mg/kg, indicating a high probability that the technology did not meet the cleanup criterion. Seven percent of soil samples had TPH concentrations in excess of 10,000 mg/kg.
• The geostatistical weighted average for total recoverable petroleum hydrocarbon (TRPH) concentrations was 1,680 mg/kg, with a 90 percent confidence interval of 676 mg/kg to 2,680 mg/kg. Levels of benzene, toluene, ethylbenzene, and xylenes (BTEX) were below the detection limit (6 micrograms per kilogram) in treated soil samples; BTEX was detected at low mg/kg levels in a few pretreatment soil samples.
• Analysis of triplicate treated soil samples showed marked variability in soil contaminant concentration over short distances. Analogous results for TPH and TRPH triplicate samples suggest that the contaminant concentration variability exists within the site soil matrix and is not the result of analytical techniques. This variability is the reason that confidence intervals for the average concentrations are so large.
• The data suggest that lateral or downward migration of contaminants did not occur during treatment.

FOR FURTHER INFORMATION:

EPA PROJECT MANAGER:
Paul dePercin
U.S. EPA
National Risk Management Research Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
513-569-7797
Fax: 513-569-7105
E-Mail: dePercin.Paul@epamail.epa.gov