Soil Vapor Extraction (SVE)
- ABC: Six extraction wells installed in April 2000. In July 2002, two additional wells installed and three others shut down. For treatment of contaminated groundwater, five extraction wells installed, with four in the surficial aquifer and one is the Castle Hayne Aquifer
- Parisian: Two vertical extraction wells installed for the SVE system. One well placed inside the building and other well placed next to the building.
- Randolfs: SVE system consisted of a 50 HP blower designed to operate at an extraction rate of approximately 480 SCFM at a vacuum of 16 inches of mercury. Extracted vapors treated in two GAC units.
Contacts: Varied by site
Chlorinated Solvents, Petroleum Hydrocarbons
(Groundwater) 1,2-DCE - 1,200 µg/L; PCE - 5,400 µg/L; TCE - 640 µg/L; VC - 110 µg/L. (Soil) 1, 2 DCE - <31,000 µg/kg; PCE - 2,100,000 µg/kg; TCE - 33,000 µg/kg; VC - <31,000 µg/kg
(Groundwater) 1,2,4-trimethlybenzene - 365 µg/L; 1,3,5-trimethylbenzene - 120 µg/L; PCE - 320µg/L; TCE - 4.4 µg/L. (Soil) 1,2,4-trimethlybenzene - 410 µg/kg; naphthalene - 570 µg/kg; PCE - 130 µg/kg; xylenes - 188 µg/kg
(Groundwater) cis-1,2-DCE - 840 µg/L; PCE - 47,760 µg/L; DCE - 7 µg/L; TCE - 275 µg/L; VC - 27 µg/L. (Soil) PCE - 18,000 µg/kg; TCE - 54 µg/kg; Toluene - 199 µg/kg; TPH - 12,000 µg/kg
Waste and wastewater from dry cleaning operations.
At ABC One-Hour Cleaners, prior disposal of PCE wastes and still bottoms as pothole fill may also have contributed to the contamination.
Type/Quantity of Media Treated:
Soil, Groundwater, DNAPL
Depth to Groundwater: 15 ft bgs; Conductivity: 10.3; Gradient: 0.13 ft/ft
Depth to Groundwater: 12.5 ft bgs; Gradient: 0.003 ft/ft to 0.004 ft/ft
Depth of Groundwater: 45-55 ft bgs; Conductivity: 3 ft/day; Gradient: 0.024 ft/ft
Purpose/Significance of Application:
Use of SVE to treat soil and groundwater contaminated with chlorinated solvents at dry cleaner facilities
Regulatory Requirements/Cleanup Goals:
- ABC: Soil remediation goals based on soil to groundwater leachability. Groundwater cleanup goals equivalent to groundwater standards.
- Parisian: Groundwater: PCE - 3 µg/L; TCE - 3 µg/L; naphthalene - 20 µg/L; 1,2,4-trimethylbenzene - 10 µg/L; 1,3,5-trimethylbenzene - 10 µg/L. Soil (leachability): PCE - 0.3 mg/kg; TCE - 0.3 mg/kg; naphthalene - 1.7 mg/kg; 1,2,4 trimethylbenzene - 0.3 mg/kg; 1,3,5-trimethylbenzene - 0.3 mg/kg
- Randolfs: Groundwater: PCE - 3 µg/L; TCE - 3 µg/L; cis 1,2-DCE - 70 µg/L; VC 1 µg/L. Soil: PCE - 30 µg/kg; TCE - 30 µg/kg; TPH - 340,000 µg/kg
- ABC: Contaminant concentrations in soil decreased since installation of extraction wells in April 2000, but remedial objectives have not been met. Contaminant concentrations in groundwater decreased since installation of extraction wells in January 1999, but remedial goals have not been met in the surficial aquifer. Contamination in the Castle Hayne aquifer has migrated beyond the zone of extraction well influence.
- Parisian: Contaminant concentrations in soil and groundwater decreased since using the SVE system. No further action (NFA) is the final remedy for both soils and groundwater.
- Randolfs: After one year of operation, an estimated 345 pounds of chlorinated ethenes were recovered. Approximately 90 percent of this contaminant mass were recovered from soil vapor. Approximately 1.6 million gallons of groundwater have been recovered and treated. Except for one well, contaminant concentrations in groundwater samples produced by recovery wells are the same order of magnitude since system startup with PCE concentrations in 4 of the 6 recovery wells ranging from 1,300 to 4,300 µg/L. PCE concentrations in groundwater samples collected from monitor wells however, have dropped by one order of magnitude from 10s of mg/L to less than 10 mg/L. The SVE system operation rate has been 73% and the groundwater recovery system operation rate has been 87%. Downtime has been due to power interruptions, air stripper upsets, and broken drive belts on the SVE system. Hydraulic capture of the contaminant source area also has been achieved.
- ABC: $521,463 for treatment of contaminated soil and $2,262,900 for treatment of contaminated groundwater
- Parisian: Assessment - $92,120.30; design and implementation - $72,458; operation and maintenance - $29,264; monitoring - $8,689; total cost - $202, 531
- Randolfs: Assessment - $147,800; design and implementation - $298,500; operation and maintenance - $64,500 (includes monitoring and utility payments.
Soil vapor extraction was conducted at three dry cleaner sites contaminated with chlorinated solvents from leaks, spills, or dumping of dry cleaning solvents or wastewaters. The concentration of contaminants varied by site with levels of PCE in groundwater as high as 47,760 µg/L and 1,2-DCE as high as 1,200 µg/L. Levels of TCE in soil were as 33,000 µg/kg and PCE as high as 2,100,000 µg/kg. At all three sites remediation was carried out at full scale.
At the ABC One-Hour Cleaners site, the SVE system is being expanded with an additional two to three wells, since the remedial objectives have not been met. Additional monitoring wells are being installed for treatment of groundwater and monitored natural attenuation will be investigated as a viable option. An important lesson learned at this site was that after more than a decade of soil and groundwater remediation, neither the soil nor the groundwater remediation goals have been attained. Soil excavation may have been a more expensive alternative than SVE; however, source removal would have been accomplished. The removal of the dominant source may have allowed the pump and treat system a better chance at remediation. An important lesson learned at the Parisian Cleaners site was that good soil sampling under the building provided a good design of the SVE system. Lessons learned at the Randolphs Cleaners and Alterations site were that in low permeability sediments, considerable contaminant mass can be trapped in unsaturated zone, capillary zone, and the upper most portion of the saturated zone. Also, a seasonal rise in the water tale at the site resulting in an order of magnitude increase in contaminant concentrations in monitor well groundwater samples, indicates the presence of DNAPL in and near the capillary zone at the site.