Ground-water development in East St. Louis area, Illinois. Urbana, IL ...

charged into the river as ground-water runoff or into the
atmosphere as evapotranspiration is diverted toward the
pumped well. Water levels are ultimately lowered below
all or part of the river bed in the immediate vicinity
of the well, and the aquifer is then recharged by the influent
seepage of surface water. The cone of depression
will continue to grow until sufficient area of the river bed
Table 10. Drillers Logs of Test Holes Used in Aquifer Test 3
Figure 12. Time-drawdown data for observation well 2,
aquifer test 2
Figure 13. Location of wells used in aquifer test 3
depth, respectively. The lower 6.4 feet of casing in each
test hole was slotted. The logs of test holes are given in
table 10.
A distance-drawdown field data graph (figure 14)
prepared with water-level data collected in the observation
wells after a pumping period of 1335 minutes was
superposed on the nonequilibrium type curve. The Theis
(1935) equations were used to determine coefficients of
transmissibility and storage of the aquifer. The coefficient
of transmissibility was computed to be 134,000
gpd/ft. The coefficient of storage (0.155) is in the watertable
range.
The cone of depression created by pumping a well
near a river that is hydraulically connected to the aquifer
is distorted. The hydraulic gradients between the river
and the pumped well will be steeper than the hydraulic
gradients on the land side of the well. The flow towards
the well will be greatest on the river side of the well, and
under equilibrium conditions most of the pumped water
will be derived from the river.
When the well is pumped, water is initially withdrawn
from storage within the aquifer in the immediate vicinity
of the well. If pumping is continued long enough water
levels in the vicinity of the river will be lowered and
water that under natural conditions would have dis-
Formation From To
(ft)
Test hole 3
Brown clay 0 20
Soft blue clay 20 46
Fine sand 46 50
Medium to coarse 50 82
Sand, loose 82 104
Gray clay 104 116
Fine sand, loose 116 120
Red clay 120
Rock
Test hole 4
Brown clay 0 9
Fine sand, clay streaks 9 25
Medium sand, some clay 25 30
Fine tight sand 30 52
Coarse sand and gravel, loose 52 79
Hard gray clay 79 83
Fine sand, clay streaks 83 90
Bedrock 90
Test hole 5
Brown clay 0 11
Fine sand and clay 11 17
Fine sand 17 55
Coarse sand and gravel, loose 55 83
Gray clay 83 100
Test hole 6 (Pumped Well; )
Brown clay 0 10
Fine sand and clay 10 18
Fine sand 18 48
Coarse sand and gravel, boulders
drilled like rock ledge at 57 feet 48 80
Gray clay 80 84
Figure 14. Distance-drawdown data for aquifer test 3
16