U.S. EPA Contaminated Site Cleanup Information (CLU-IN)

U.S. Environmental Protection Agency
U.S. EPA Technology Innovation and Field Services Division

Dense Nonaqueous Phase Liquids (DNAPLs)

Treatment Technologies

Soil Vapor Extraction and Air Sparging

Multi-Component Waste

Due to the low volatility of coal tar, creosote, and heavy oils, SVE alone is unlikely to remove more than the light ends that may be found within mixtures. SVE generally must be used in combination with other technologies—such as thermal treatments—that can volatilize heavier contaminants, thus making them accessible to extraction equipment. The Thermal Processes section contains case studies of soil heating and vapor extraction used together.

Sparging has been shown to be effective at removing dissolved groundwater contaminants and is widely employed as a remediation technology for volatile contaminants, such as gasoline; however, its effectiveness against concentrated semivolatile contamination, such as undissolved coal tar, has not been demonstrated. Consequently, sparging is viewed as a polishing technology that could be effective in treating dissolved-phase contaminants, such as BTEX, and potentially in reducing the mobility of coal tar, but likely would be only marginally effective at remediating tar (Oneonta ROD 2005).

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Case Studies: Coal Tar | Case Studies: Creosote

Case Studies: Coal Tar

Adobe PDF LogoRecord of Decision: NYSEG Oneonta MGP Site, City of Oneonta, Otsego County, New York, Site Number 4-39-001
New York State Department of Environmental Conservation, 48 pp, 2005

In 1994, NYSEG constructed an AS/SVE system as an interim remedial measure. This system was constructed in the main source area on the western plant site, which was very heavily contaminated with MGP waste products. The intent was to help reduce the amount of groundwater contamination leaving the site by introducing air into the subsurface. Air was pumped into the subsurface through a series of sparge wells. At the same time, air was withdrawn from the subsurface through a horizontal well. This air was collected for treatment prior to discharge to the atmosphere. The SVE system operated for four years, from 1997 to 2001, but the system proved ineffective against the high concentrations of contaminants. Samples collected from the air recovered by the horizontal well prior to treatment showed very low levels of volatile contaminants, and it appeared that little contamination was being removed. Consequently, NYSEG proposed closing down operation of the SVE system, and it was abandoned in July 2001. It should be noted, however, that sparging technology may still be effective against lower-level contamination found around the fringes of the contaminated area. A biosparge system will be constructed outside the limits of the MGP site excavation to accelerate the degradation of MGP-related contaminants in groundwater.

Case Studies: Creosote

Adobe PDF LogoFirst Superfund Five-Year Review Report, Cape Fear Wood Preserving, Fayetteville, Cumberland County, North Carolina
U.S. EPA Region 4, 110 pp, 2006

The original site remedy specified 3 technologies for groundwater: extraction and treatment of groundwater/DNAPL with on-site discharge of the treated groundwater, air sparging, and injection of nutrients to promote in situ biodegradation of the contaminants. Based on the findings in a 2004 remediation system evaluation, the air sparging and nutrient injection systems were shut down. The time frame estimated in the Remedial Design to achieve the groundwater cleanup goals was underestimated due to the unexpected extent of the creosote DNAPL. It will take significantly longer than 8 years to achieve the groundwater cleanup goals.