FLOOD07651

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

was located 824 ft west of production well 3 and
observation well 2 was located 850 ft west of production
well 3. Pumping was started at 9:45 a.m. on July 2 and was
continued at a constant rate of 220 gpm for about 8 hours
until 6:02 p.m. Time-drawdown data for the production well
and observation well 1 adjusted for minQr barometric
pressure changes are presented in Table 5.1.
A straight line was fitted to a semilogarithmic
time-drawdown graph for production well 3. The slope of
the straight line was used to calculate aquifer
transmissivity. Aquifer storativity cannot be calculated
with the graph because the effective radius of the

82 GROUNDWATER PUMPING TESTS

Table 5.1. Database for Case Study 5.1

Time After Weill
Pumping Adjusted
Started Drawdown
(min) (ft)

3 0.3
5 0.7
8 1.3
12 2.1
20 3.2
24 3.6
30 4.1
38 4.7
47 5.1
50 5.3
60 5.7
70 6.1
80 6.3
90 6.7
100 7.0
130 7.5
160 8.3
200 8.5
260 9.2
320 9.7
380 10.2
500 10.9

Time After
Pumping
Started
(min)

15
25
45
60
76
90
132
166
195
256
282
314
360
430

CASE STUDIES 83

production well is unknown and total drawdown in the
productiQn well is affe.cted by well loss.
The type curve for model 1 (Figure F.l in Appendix F)
was matched to the logarithmic time-drawdown graph for
observation well 1. Match point coordinates were used to
calculate aquifer transmissivity and storativity.
Calculations for. the production well and observation well
1 are as follows:

Production Well

Q= 220 gpm
T = 2.64 X 10'(2.2 X 10')/4.8

5, = 4.8 ft

T = 12.100 gpdIft

Observation Weill

Well 3
Adjnsted
Drawdown
(ft)

24.8
25.5
26.6
27.3
28.0
28.2
29.0
29.5
30.3
30.5
30.6
30.7
30.8
31.5

Q = 220 gpm. r = 824 ft, m = 18 ft

Match Pt. Coord. W(u) = 0.1, 1/u = 1.0
5 = 0.25 ft, t = 4.3 min

T = 1.146 X 10'(2.2 X 10')1 X 10-1/2.5 X 10-1
T = 10,100 gpdlft

S = 1.01 X 10'(1.0)4.3/[2.693 X 10'(6.8 X 1()5)j
S = 0.00002

Time-drawdown graphs for the production well and obser-
vation weill are presented in Figures 5.1 and 5.2.
The average calculated aquifer transmissivity and
storativity are 11,000 gpdlft and 2.2 X 10-', respectively.
Well storage capacity impacts are appreciable during the
first 5 minutes of pumping; in analyzing test data, empha-
sis was placed on data after this time. The pumping test
sampled a cylindrical volume of the aquifer with a height of
18 ft (aquifer thickness) and a radius of about 22,000 ft.
Aquifer hydraulic conductivity is 611 gpdlsq ft, which is
indicative of a fine sand aquifer. (See Table C.l in Appen-
dixC.)
A pumping test was conducted in Case Study 5.2 on June