35 Ill. Adm. Code 671.APPENDIX
D Neuman Equations and Pump Test Procedures for Unconfined or Water Table Aquifers
Section 671.APPENDIX D Neuman
Equations and Pump Test Procedures for Unconfined or Water Table Aquifers
If no data is available for
unconsolidated or non-fractured bedrock aquifer constants, a pump test can be
conducted to determine the lateral radius of influence as follows:
A. At least one fully penetrating observation well is necessary.
B. The pump test should be conducted for at least 48 hours.
C.
The flow equation for unconfined aquifers is given by:
T
=
114.6Q
W(u
A
, u
B
G
)
(h
o
– h)
Where:
T
=
transmissivity (gallons per
day per food)
Q
=
production well discharge rate
(gallons per minute)
h
o
-h
=
drawdown in the observation
well (feet)
W(u
A
, u
B
G
)
=
well function for unconfined
aquifers, the well function is calculated and (u
A
G
), (u
B
G
) is obtained from Table B.
=
u
A
=
2693r
2
S
(Early
phase draw down)
G
=
r
2
K
v
Tt
b
2
Kh
u
B
=
2693r
2
Sy
(Late phase
draw down)
T
=
Khxb
Tt
Where
S
=
storativity (dimensionless)
Sy
=
specific yield (dimensionless)
t
=
time (minutes)
b
=
aquifer saturated thickness
(feet)
K
v
=
aquifer vertical hydraulic conductivity
(gallons per day per square feet)
Kh
=
aquifer horizontal hydraulic
conductivity (gallons per day per square feet)
r
=
distance from the production
well to observation well (feet)
The radius
of influence can then be calculated using the following:
r
=
Ö
u
B
Tt
2693Sy
Where
t
=
time pumped under normal
operational conditions (minutes).
Two sets of
type curves are used (Neuman, 1975). Type-A curves are used for early phase
drawdown data, and Type-B curves are used for late phase drawdown. The type
curves are used to evaluate field data for time and drawdown, which are plotted
on logarithmic paper of the same scale. The following procedure can be used:
1.
Overlay time drawdown data on Type-B curves. At any match point, the
values of W(u
B
,
G
), u
B
,
t, and h
o
-h are determined. The value of
G
comes from the type curve. The value of T and Sy is
calculated using these values and the following equations:
T
=
114.6Q
W(u
B
G
)
Sy
=
Tt
H
o
-h
3693r
2
2. Use the early phase drawdown Type-A curve to calculate W (u
A
G
), u
A
, t, h
o
-h
and S using the
G
value previously
determined for the Type-B curve and the following equation:
S
=
Ttu
A
2693r
2
3. The value of horizontal hydraulic conductivity can be
determined using:
Kh
=
T
b
4. The vertical hydraulic conductivity can be determined using
the following:
K
v
=
G
b
2
Kh
r
2
5.
The lateral radius of influence can then be calculated with the
following:
r
=
Ö
u
B
Tt
2693Sy