A 1,000-gallon fuel oil underground storage tank (UST) was
removed from the front yard of a State Agency-owned residential building in 1995. During
removal, evidence of petroleum product contamination was observed in the excavation.
Due to the proximity of the UST to the building foundation, all of the contaminated soil could not be removed. A remediation method of monitored natural attenuation was chosen to remediate the
residual soil contamination. FS Engineers, Inc. (FSE) was contracted to conduct
annual groundwater sampling from 2002 through 2006.
In 2006, FSE prepared a Release Abatement Measure (RAM) Plan for the
use of In-Situ Chemical Oxidation (ISCO) to remediate the residual soil and groundwater contamination. Following approval by the
Massachusetts Department of Environmental Protection (MassDEP), FSE oversaw the injection of 1,000 pounds of Oxygen BioChem
(OBC)™ slurry into selected points at the site and a downgradient property. FSE
conducted additional quarterly groundwater sampling in 2006 through 2007. Based
upon the evaluation of soil and groundwater analytical data, and upon a review of reports and field notes from the 1995 UST
excavation, FSE submitted a Modified RAM Plan to MassDEP in 2008. The Modified
RAM Plan included the further excavation of contaminated soils beyond the original UST excavation limits.
FSE oversaw the additional soil excavation at the site in 2008 which increased the total depth
of the UST excavation by several feet. Bill of Lading documentation was prepared
for the offsite disposal of the contaminated soil. Confirmatory soil samples
were collected from the excavation prior to backfilling and a subsequent round of groundwater sampling was conducted. Based upon the remedial actions performed and the laboratory analytical data, regulatory
closure of the site was achieved in 2008 with a Class A-2 Response Action Outcome Statement that was submitted to the MassDEP
in conjunction with a RAM Completion Statement Report.