3    CLEAN-UP OF TOLUENE-CONTAMINATED SOIL AND
GROUNDWATER USING SOIL VAPOR EXTRACTION
David R. Hale, Senior Project Engineer
Qsource Environmental Services
Philip L. Hayden, Chairman of the Board
Qsource Environmental Services
IVliamisburg, Ohio 45342
INTRODUCTION AND BACKGROUND
In 1986, a large commercial printing facility experienced a large leak of toluene solvent from a
faulty pressure gauge on an underground storage tank (UST) system. Although exact amounts could
not be determined, estimates of the amount spilled ranged up to 3,000 gallons. An emergency
response action was undertaken to remove a quantity of heavily contaminated soil, and a site investigation to determine subsurface impacts was begun.
SITE INVESTIGATION
The site investigation consisted of the installation and sampling of 14 shallow groundwater monitoring wells. During the installation of these wells, it was observed that the shallow geology of the site
consisted of sand and gravel outwash deposits overlying a glacial till layer. This aquitard till layer
separates a thin shallow layer of groundwater from the extensive sand and gravel deep aquifer beneath
the site. This deep layer is used as the sole source drinking water aquifer for a large metropolitan
area.
Shallow groundwater was detected at depths from 15 to 22 feet below the ground surface. The
thickness of this groundwater layer ranged from approximately one to three feet. Samples of this
shallow groundwater revealed toluene contamination ranging from non-detectable away from the
UST spill area to above solubility limits (>450 mg/L) beneath the spill area. No observations or
measurements of floating free product were made during the site investigation, although the substantial concentrations observed in several of the well samples (up to 220,000 mg/L) were undoubtedly the
result of recovered free product.
INITIAL GROUNDWATER REMEDIATION
Based on the results of the groundwater investigation, a groundwater remediation system consisting
of four recovery wells was installed. These wells were located in the area of highest groundwater
contamination. Each well had a 4" diameter PVC casing, and was installed with a air-operated
bladder pump to recover groundwater and free product. Recovered groundwater was then pumped to
an existing solvent recovery system for treatment prior to discharge.
Operation of the groundwater recovery system indicated that a total of approximately 1 gallon per
minute (GPM) of groundwater was being recovered by the four wells. Based on a this recovery rate,
and an average concentration of 300 mg/L toluene, this resulted in less than 0.5 gallons per day of
toluene being recovered. Because of the low pumping rates, cleanup of the site and control of
contamination by groundwater pump and treat was deemed not suitable.
REMEDIAL ALTERNATIVE SELECTION
At this stage, a decision was made to independently review the known conditions at the site and
assess alternative remedial strategies for cleaning up the site. Another environmental engineering firm
was retained, and after all available information on the site had been reviewed, a short-list of
applicable alternatives was developed. These included:
45th Purdue Industrial Waste Conference Proceedings, © 1990 Lewis Publishers, Inc., Chelsea, Michigan 48118.
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