The Great Falls Citizens Association Special Committee on Groundwater Contamination has reviewed the groundwater monitoring report issued for second quarter 2015 submitted by Fairfax Petroleum and its environmental engineering contractor, Kleinfelder East, to the Virginia Department of Environmental Quality.
As specified in the Department of Environmental Quality Corrective Action Plan, pumping and treatment of groundwater from wells on the contaminated site began in August 2014, and has significantly reduced the concentration of Methyl Tertiary Butyl Ether (MTBE) in groundwater. MTBE was the gasoline additive used under direction of the EPA prior to 2006, and some was released from the former Exxon Service station to groundwater.
Pumping has proceeded at approximately 5-8 gallons per minute, for a total of 2.7 million gallons. The groundwater has been treated by air stripping and by charcoal filtration in a special treatment trailer, and the clean treated water is released to the storm drain. Approximately 256 pounds of MTBE have been removed, including 27 pounds during the past 3 months of treatment.
Concentrations at key deep wells remain at 4700 ppb at point RW-1, at 630 ppb at point MW-16D, 1400 ppb at point PW-1, and 940 ppb at point 20-D, which are still higher than the so called “deep end point” of 343 ppb. The end point was specified by the Virginia Department of Environmental Quality as a target concentration unlikely to result in detectable levels of 1 ppb, in any private wells. Concentrations at Point 23D, to the south along Walker Road, have been greatly reduced to only 3 ppb, far below the end point there. Point 20-D is 175 feet to the southeast from the original site, across Walker Rd, on the Great Falls Center. Therefore, remaining deep concentrations at some locations must be reduced by a factor of approximately 10 before treatment can be considered complete. Well W-1, a so-called “shallow well” located 140 feet from the site, has had concentrations of 8800 ppb, compared to the “shallow end point” of 5000 ppb. Concentrations must be reduced by at least a factor of 2.
GFCA has commented to DEQ that the concentrations at all wells should be reduced to the lower end point, approximately 10 times, and that another recovery well, across Walker Road from the original site, is needed to accomplish treatment of the entire contamination plume. Fairfax Petroleum committed to this in applying for the Special Permit for the TD Bank. Similarly, the CAP Addendum committed to pumping from the east side of Walker Road as needed to meet the end points.
The monitoring is done each quarter, and it appears that pumping will need to continue for at least another 4 quarters. After the end points are reached, monitoring will continue for another 2 years to verify no contamination will ever reach private groundwater wells in the vicinity of the commercial center of Great Falls.
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The figure below depicts the deep MTBE groundwater concentrations distributed on the original site and on the site across Walker Road