Technology:
Groundwater Extraction followed by Granular Activated Carbon (GAC); In situ Air Sparging of saturated zone
Groundwater Extraction With GAC - 4 extraction wells installed in two phases (1988 and 1992); depths up to 28 feet below ground surface (bgs) with extraction rates of 50 and 100 gpm - Extracted water treated using two GAC vessels in series; recovered free product sent to storage in aboveground tanks In-situ Air Sparging - 30 two-inch diameter air sparging wells with 3-foot screens - Installed to depths of 25-30 feet - Two 300 scfm blowers
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Cleanup Authority:
Other: Voluntary cleanup
SIC Code:
4612 (crude petroleum piping) | Point of Contact:
Paul Ressmeyer
Remedial Project Manager
Amoco Corporation |
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Contaminants:
Benzene, Toluene, Ethylbenzene, Xylenes (BTEX), Methyl tert butyl ether (MTBE) - An estimated 300,000 to 2 million gallons of gasoline, fuel oil, and kerosene released to subsurface - Free product present in an approximate 6-acre area at an average apparent thickness of 2 feet |
Waste Source:
Other: Petroleum pipeline leak |
Type/Quantity of Media Treated:
Groundwater - 775 million gallons of groundwater between 1988 and 1993 - Sand and gravel - Porosity 30-40% - Hydraulic conductivity 0.0002 - 0.0004 cm/sec |
Purpose/Significance of Application:
Full-scale pump and treat of petroleum contaminated-groundwater using granular activated carbon to recover free product and treat groundwater. In situ air sparging was subsequently added to treat the saturated zone. |
Regulatory Requirements/Cleanup Goals:
- The remediation is being performed as a voluntary action by Amoco; final cleanup criteria will be established in the future with concurrence from the Michigan Department of Natural Resources - Treated water required to meet SPDES permit requirements prior to discharge - benzene (5 ~g/L), total BTEX (20 ~g/L), MTBE (380 ~g/L), pH (6.5-9.0) |
Results:
Groundwater Extraction with GAC - 118,000 gallons of free product recovered (10/87-12/93); rate of free product recovery has decreased to 20 to 25 gallons per month as of late 1993 - Free product has been hydraulically contained and observed apparent thickness of free product has been reduced to <0.01 feet - Concentrations of BTEX in extracted groundwater have remained relatively constant; MTBE concentrations have decreased - Treated effluent from GAC have generally met SPDES discharge limits In-situ Air Sparging - Pilot testing indicated a radius of influence of 65-150 feet per single well - No additional results were available at the time of this report |
Cost Factors:
- Total Capital Costs: about $297,000 for groundwater recovery and treatment system (including well construction, pumps, system installation, engineering); $375,000 for the air sparging system (including 3 months of initial operations, and testing) - Annual Operating Costs (approximate): about $475,000 for groundwater recovery and treatment system; not yet defined for air sparging system - An estimated total cost for completing the cleanup is not available at this time |
Description:
The Amoco Corporation owns and operates a liquid petroleum product pipeline that transverses the Constantine site. As a result of a pipeline leak, discovered in June 1987, an estimated 350,000 to 2 million gallons of gasoline, fuel oil, and kerosene were released to the subsurface. Free product was present at an average apparent thickness of 2 feet. Beginning in October 1988, a groundwater pump and treat system, consisting of 4 extraction wells and granular activated carbon (GAC) vessels, was used to recover free product and treat the contaminated groundwater. In situ air sparging of the saturated zone was subsequently added and began operating in February 1994.
Through December 1993, groundwater extraction with GAC had recovered an estimated 118,000 lbs of free product and reduced the observed apparent thickness of the free product layer to <0.01 feet. MTBE concentrations were reduced; however, BTEX concentrations near the source of contamination remained relatively constant. No full-scale performance data were available for the air sparging system at the time of this report.
The groundwater extraction with GAC system operated > 95% of the time through December 1993. Periodic shutdowns of 1 to 3 days were required for carbon changeout and extraction well rehabilitation. Leasing the activated carbon system and carbon provided flexibility to modify the treatment system in response to changing operating conditions. However, GAC proved to be inefficient in removing MTBE when compared to BTEX. |
