34    GASOLINE RECOVERY IN SOUTHERN MICHIGAN
Richard G. Eaton, Project Hydrogeologist
Michael V. Glaze, Senior Hydrogeologist
O.H. Materials Corp.
Findlay, Ohio 45839
INTRODUCTION
As of the end of 1985, the United States Environmental Protection Agency estimated that there
were between 3 to 5 million buried tanks nationwide and that 25% of those were in a leaky condition.
Every gas station has at least one and most have several buried tanks. Many major businesses have
underground storage tanks for storing liquids ranging in character from gasoline to solvents and spent
pickling liquors.
Leaking underground storage tanks constitute one of the largest sources of ground water pollution
in the country today.
CASE HISTORY
In southern Michigan, a large factory had an underground gasoline storage tank for the use of
intra-plant vehicles. The transmission lines from this tank were fiberglass. The fiberglass transmission
lines deteriorated over time and began to leak. No determination of lost gasoline inventory was
generated nor any realistic time as to when the loss or losses occurred. Current operating procedures
now require that inventories be kept. Periodic tank and line testing of the Petro Tite or Ezy-Chek type
is also recommended.
In the illustrated case, however, as in many other instances, gasoline fumes permeated through an 8-
inch-thick concrete floor into a work area filled with heavy machinery. Immediate resolution of the
vapor phase gasoline was performed by proper ventilation in the effected area. O.H. Materials Corp.
(OHM) was retained to locate and to determine the source and abate the effect of the contaminant.
HYDROGEOLOGIC INVESTIGATION
The initial recommendation was to perform a leak test on the tank and ancillary lines to determine
the potential leak source or sources. Since the underground tank was of steel construction and upon
replacement showed no sign of leak occurrence, the fiberglass transmission line was believed to be
suspect and was subsequently replaced. With that acquired information, no leak test was felt to be
warranted.
Secondly, installation of monitor wells around the site was accomplished to determine the areal
extent of the plume, flow direction and rate of contaminant transport. Because of restraints on well
locations due to equipment and in-plant construction, a perimeter placement approach was utilized. A
series of 11 monitor wells were installed inside and outside the building. The installed wells were 2-
inch-inside-diameter PVC screen and casing. They were installed to a depth of 15 feet. Two-inch-split-
spoon samples, taken for lithologic determinations, were screened to determine appropriate screen
slot size. Split-spoon samples were also tested with a photoionization detector (PID) to help determine
the vertical extent of contamination.
Upon completion of drilling, the wells were surveyed to within 0.01 inch and located on a scaled
map. Measurements of static water levels and product thickness were taken for baseline readings.
True static water levels were calculated for ground water gradient determination using the following
formula modified from Shepherd [1]:
Sr = [(I - D) x T] + Sw
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