RESEARCH· ·1970·

GROSSMAN
B207
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0 J FMAMJJASONDJ FMAMJJASONDJ FMAMJJASOND
1 962 1963 1964
FIGURE 3.-Relation between water levels in two observation wells and total hydrocarbon
content (as styrene, patterned area) of water from four bedrock wells at Gales
Ferry, Ooom., 1962 to 1964.
26
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evenly distributed throughout the year, but groundwater
discharge exceeds recharge during the late
spring and summer, chiefly owing to heavy evapotranspiration
losses. I-Iydrographs of two nearby observation
wells (locations shown in fig. 1), Gt 6 in crystalline
rock and NSn 25 in till (l\1eikle, 1967, p. 8; Meikle
and Baker, 1965, p. 12), indicate that the seasonal low
positions of the water table closely coincide in time
with the seasonal highs in styrene content of the
ground water (fig. 3). The inverse relationship between
ground-water level and styrene concentration is
seemingly contradicted by the direct relationship between
rainfnll nnd styrene concentration in 2 of the 4
wells, as shown in figure 2. Evidently waterborne styrene
was slowly moving into the aquifer, but its movement
wns accelerated during periods of substantial
rainfall, especially during the period of relatively effective
recharge in the autumn. The inverse relationship
is ascribed to concentration of waterborne styrene in
a smaller section of the bedrock aquifer and to seasonal
expansion of local cones of depression. The cones intermittently
deepen and grow in size during the summer
beb1use of increased domestic consumption from a
thinner saturated section of the bedrock aquifer. Thus,
their growing radii intercepted a greater vertical and
horizontal extent of the aquifer, including parts contaminated
by waterborne styrene. In addition, high
styrene concentration during seasonal lows may reflect
lack of dilution by new ground water.
Long-term changes in styrene content of ground
water shown in the graph (fig. 3) reflect changing
hydrochemical conditions in the aquifer resulting from
emplacement and removal of the two sources of contamination
shown in figure 1. The western source was
buried in the spring of 1960, and the eastern sourc~ is
believed to have been buried sometime in the same
year. All known styrene-contaminated soil at the
western burial site, amounting to about 5 cubic yards,
was removed in November 1961, and at least twice as
much material was removed from the eastern burial
site in October of 1962. The graph (fig. 3) shows that
the concentration of styrene peaked in the month and
year when the second of the two contaminating sources
was r~moved. Thereafter, annual styrene highs were
successively smaller, as shown by the styrene depletion
curve, until the fall of 1964 when measurable styrene
was detectable. in only one of the four wells. The data
indicate that styrene Jnay persist in a crystalline bedrock
aquifer for at lea.st 2 years •after removal of con­
1
taminating sources under the conditions described.
They also demonstrate that delineation of the movement
and storage of contaminated ground water is