35 Ill. Adm. Code 671.APPENDIX B
B Theis Equation Using Available Data
Section 671.APPENDIX B Theis
Equation Using Available Data
If pump test data is available
for an unconfined/confined unconsolidated or non-fractured bedrock aquifer the
lateral radius of influence can be calculated as follows:
r
=
the square root of
uTt
2693S
Where:
r
=
radius of influence (feet)
t
=
time well is pumped under
normal operational conditions (minutes)
S
=
aquifer storativity or
specific yield (dimensionless)
T
=
transmissivity (gallons per
day per foot)
u
=
= is a dimensionless parameter
related to the well function
W(u)
=
T(h
o
- h)
114.6Q
Where:
W(u)
=
well function, the well
function is calculated and u is obtained from Table A.
h
o
- h
=
drawdown in the piezometer or
observation well (feet)
Q
=
production well discharge rate
under normal operational conditions (gallons per minute)