Technology:
Air Sparging/Soil Vapor Extraction (SVE)
- SVE system consists of approximately 230 feet of horizontal SVE piping installed immediately below the asphalt parking lot surface of the site; piping is connected to a 20 HP Lamson Blower operating at 12 to 14 inches of mercury; extracted vapors are treated using a thermal oxidizer.
- Air sparging system, which began operating two weeks after the SVE system was activated, consists of ten vertical air sparging wells, each installed at a depth of about 26 feet with 5-foot well screens; wells are connected to a Kaeser SK-26 air sparge compressor operating at 68 to 70 psi.
- A total of 28 wells (on-and off-site) are used to monitor groundwater
|
Contaminants:
MTBE, BTEX, Naphthalene
- MTBE concentrations as high as 5,110,000 ug/L
- BTEX concentrations as high as 301,000 ug/L for toluene
- Naphthalene concentrations as high as 2,700 ug/L |
Regulatory Requirements/Cleanup Goals:
- Site-specific target levels (SSTLs) were established by SCDHEC for MTBE, benzene, toluene, ethylbenzene, xylenes, and naphthalene, with 15 monitoring wells used in setting the SSTLs.
- Total SSTLs (sum of individual SSTLs for each well) - MTBE - 646 ug/L; benzene - 191 ug/L; toluene - 11,938 ug/l; ethylbenzene - 9,426 ug/L; xylenes - 78,496 ug/L; naphthalene -418 ug/L |
Results:
- As of August 2000, the total mass and maximum concentrations of MTBE, BTEX constituents, and naphthalene in the groundwater had decreased, with the SSTLs being met for toluene, ethylbenzene and xylenes.
- Total MTBE concentrations have been reduced by about 99.99 %; BTEX concentrations by more than 99%, and naphthalene concentrations by about 96%; the SSTLs had not been met for benzene, MTBE, or naphthalene
- The system will continue to be operated until all SSTLs have been met; the contractor projects cleanup of the site to be completed by April 2001 |
Description:
Eaddy Brothers is a gasoline service station located in Hemingway, South Carolina. In September 1998, a release was reported from the station's underground storage tanks (USTs). Initially, the local fire department was dispatched in an emergency response because of gasoline vapors that had accumulated in a storm sewer underlying downtown Hemingway. Soil and groundwater at the site were found to be contaminated with MTBE, BTEX, and naphthalene, and free product was present in the groundwater. Data from October 1998 showed concentrations of contaminants in groundwater as high as 5,110,000 ug/L for MTBE, 226,000 ug/L for benzene, 301,000 ug/L for toluene, 280,000 ug/L for ethylbenzene, 278,000 ug/L for xylene, and 2,700 ug/L for naphthalene. A Corrective Action Plan (CAP) was implemented in July 1999 under Subtitle I of the RCRA program. The CAP included free product recovery and treatment of dissolved-phase groundwater contamination using air sparging/SVE.
The SVE system, installed in July 1999, consists of a 230-foot horizontal SVE pipe installed immediately below the asphalt parking lot surface of the site, with extracted vapors treated using a thermal oxidizer. The air sparging system, which began operating two weeks after the SVE system was activated, consists of ten vertical air sparging wells. After about a year of operation of the air sparging/SVE system, the SSTLs have been met for toluene, ethylbenzene, and xylenes. While MTBE, benzene, and naphthalene levels have been reduced by more than 90%, they remain above the SSTLs. The system will continue to operate until all SSTLs have been met, with the site contractor estimating completion of the remediation in April 2001. |
