Remediation of Toulene-Affected
Soil and Groundwater
Work Description
– General:
Chase Environmental Group was contracted for the removal
and closure of two 20,000-gallon heating oil tanks. Traces
of toluene were encountered in the excavation pit upon removal
of the heating oil tanks. Subsequent assessment identified
extensive subsurface toluene contamination in an area immediately
adjacent to the heating oil underground storage tank pit
area. A Work Plan was submitted and approved by the Kentucky
Superfund Branch for characterization and determination
of the extent of toluene-contaminated soil and groundwater.
The Work Plan identified cleanup levels for toluene in soil
and groundwater based on USEPA Region 9 Preliminary Remediation
Goals and Maximum Contaminant Levels and Kentucky Underground
Storage Tank (UST) Branch standards for cleanup of toluene
in soil from a release from an underground storage tank
fuel system.
Custom Chrome Project
Subsequent removal of toluene-affected
soil uncovered a spent solvent recovery piping system that
was once connected to a 10,000-gallon underground flow-through
tank and a 20,000-gallon storage tank. Review of historical
“as-built” plans provided details on the design and construction
of the spent solvent recovery system. Residual toluene in
the product piping system was removed by vacuum extraction
and the accessible piping was removed. The remaining piping
that ran under the concrete foundation of an adjoining warehouse
was cut-off and closed in-place by filling with concrete.
Toluene contamination was subsequently identified in the
sandy fill materials of the former toluene underground storage
tank pit. Field screening and Geoprobe sampling techniques
were utilized to determine the potential extent of subsurface
contamination. Approximately 700 cubic yards of toluene
contaminated soil and fill materials were removed by excavation
for packaging and transportation to a hazardous waste disposal
facility.
Chase installed twelve temporary
monitoring wells in perimeter areas surrounding the waste
removal area in order to assess potential toluene contamination
in groundwater outside of the excavation pit area. The temporary
monitoring wells were sampled for volatile organic compounds.
The depth to groundwater was measured in the temporary monitoring
wells for determination of groundwater flow direction. No
groundwater contamination was identified outside of the
waste removal area. The waste removal excavation pit was
back-filled with gravel. Toluene-affected pit water was
remediated in-situ using a combination of enhanced bioremediation
and dual-phase vacuum extraction remedial methods. Cleanup
to the adopted cleanup levels for soil and toluene-affected
excavation pit water – which was determined to be recharged
by groundwater - was achieved within six months of the discovery
of the subsurface toluene contamination. Both the Kentucky
UST and Superfund Branch issued no further action letters
after remediation efforts were completed.
Location:
Louisville, Jefferson County, Kentucky
Regulatory Basis:
Kentucky Department of Environmental Protection, Division
of Waste Management and Underground Storage Tank Branch
