FLOOD07651

• County: Statewide
• Basin: Statewide
• Title: Groundwater Pumping Tests: Design and Analysis
• Date: 12/1/1997
• Floodplain - Doc Type: Educational/Technical/Reference Information

04 l:Jt1UUI\lUVVI-\I t:N "'UIVlt"II\l1,;. I t::.~ I ~ CASE STUDIES 85
32 100.0
Production Well
30 Observation Well I
.... 10.0
.....
c 28
.
0
-0
~ 1.0
is 26

24
10

Figure 5.1.

100 1000

Time After Pumping Started CHin)

Time-drawdown graph for production well in Case Study
5.1.

2, 1960, using a group of fully penetrating wells located
about 1.5 miles north of the corporate limits of the village
of St. David, Illinois (see Walton, 1962, pp. 47-48). In gen.
eriil, 40 ft of sandy clay overlie an 8-ft.thick fine sand an?
some gravel aquifer which is underlain by shale. The aqUl'
fer pinches out (barrier boundaries) east and west of ~he
production well. There are no nearby interfering productIOn
wells. The effects of discharging the production well were
measured in observation wells 1 and 2. Observation well I
was located 165 ft east of the production well and observa-
tion well 2 was located 20 ft west of the production well.
Pumping was started at 10:00 a.m. and was continued for
six hours at a constant rate of 62 gpm. Time-drawdown
data for the observation wells adjusted for minor changes
in barometric pressure are presented in Table 5.2. .
The type curve for model 2 (Figure F.3 in ;\pp~n~ F)
was matched to early portions of the loganthmic tIme-

0.1

0.1 1 10 100 1000

Time After Pumping Started CHin)
Figure 5.2. Time-drawdown graph for observation weIll in Case Study
5.1.

',;,drawdown graphs for observation wells 1 and 2 before
': boundary impacts became appreGiable. Aquifer transmis-
; sivity and storativity were calculated with match point
'coordinates. After about 12 minutes-of pumping, the time-
j'a~ of drawdown in the observation wells increased. and
data deviated upward from type curve traces, indicating
the presence of a barrier boundary. The model 1 type curve
(Figure F.l in Appendix F) was matched to later time-
drawdown data affected by the barrier boundary. The
divergences of the first and second type curve traces were
.: used to determine the distances from the observation wells
to the first barrier boundary image well.
;. After about 70 to 100 minutes of pumping, the time-rate
'ofdrawdown in the observation wells again increased, and
data deviated upward from the second type curve trace,
. dicating the presence of a second barrier boundary. The
odel 1 type curve was matched to late time-drawdown
ata affected by both barrier boundaries. The divergences