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

Figure 20. Time-drawdown data for well S-2, aquifer test 6
Figure 18. Distance-drawdown data for aquifer test 5
The specific capacity is influenced by the hydraulic
properties of the aquifer, the radius of the well, r w , and
the pumping period, t. The relationship between the
theoretical specific capacity of a well and the coefficient
of transmissibility is shown in figure 21. A pumping
period of 24 hours, a radius of 12 inches, and a
storage coefficient of 0.1 were used in constructing the
graph.
There is generally a head loss or drawdown (well
loss) in a production well due to the turbulent flow of
water as it enters the well itself and flows upward
through the bore hole. Well loss and the well-loss coefficient
may be computed by equations given by Jacob
(1946). The computations for the well-loss coefficient,
C, require data collected during a step-drawdown test
Figure 19. Location of wells used in aquifer test 6
Table 13. Drillers Logs of Wells Used in Aquifer Test 6
Formation From To
Well S-1
Gray sandy clay 0 30
Gray fine sandy clay 30 40
Coarse gray sand, small gravel 40 45
Gray fine sand, scattered fine gravel,
brown fine sand 45 66
Brown coarse sand, fine gravel 66 76
Coarse sand and gravel 76 90
Coarse sand, fine to medium gravel 90 100
Bedrock About 120
Well S-2
Gray sandy clay 0 30
Gray fine sandy clay 30 40
Coarse gray sand, small gravel 40 45
Gray fine sand, scattered fine gravel,
brown fine sand 45 66
Brown coarse sand, fine gravel 66 75
Brown coarse sand, fine gravel, some
gray clay 75 76
Coarse sand, small to large gravel 76 90
Brown coarse sand, fine to medium gravel 90 100
Figure 21.
Theoretical relation between specific capacity
and the coefficient of transmissibility
21