PROJECT A-8
In Situ Sub-Surface
Residence, Cohasset, MA
PROBLEM:
Contaminated soils and groundwater during removal of UST
Oil contaminated soils and groundwater were initially observed at a
residential property during the removal of a 275 gallon UST. The
dwelling was constructed on a concrete slab with a shallow
footing. The UST was located immediately adjacent to the
footing. Excavation of the contaminated soils was limited because of
the risk of undermining the footing and the nearby septic
system. Analysis of the residual contaminated soils in the sidewalls
of the excavation reported an average TPH level of 2,057 ppm with a
groundwater sample registering a TPH level of 880 ppm.
SOLUTION:
In situ bioremediation with MicroSorb® SC, MicroSorb® Nutrients, and MicroSorb® Biocatalyst
Because residual contaminated soils were present beneath the dwelling
and near the septic system, in situ bioremediation was the best
method to clean the site. A mixture of MicroSorb® SC,
MicroSorb® Nutrients, and MicroSorb®
Biocatalyst was applied to the impacted area via a perforated pipe
installed prior to backfilling the excavation. Three one-inch diameter
injection points were also installed with a hand auger.
RESULTS:
No detectable levels of TPH in groundwater
The soils and groundwater were resampled four months after
application. The results of these analyses reported no detectable
levels of TPH in the groundwater and an average TPH concentration in
the soils of 118 ppm. These levels are well below the cleanup
standards for residential properties. The cost of the biotreatment,
including MicroSorb® SC, MicroSorb®
Nutrients, MicroSorb® Biocatalyst, and application of
the mixture was $1,420.
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