PERMFILE54775

• Permit No: C1981018
• IBM Index Class Name: Permit File
• Doc Date: 5/13/2002
• Doc Name: Surface Operations on or Adjacent to Alluvial Valley Floors
• Section_Exhibit Name: SECTION II.D ALLUVIAL VALLEY FLOOR REPORT
• Media Type: D
• Archive: No

• drawdown calculations a transmissivity of 19,000 gpd/ft was used
as a compromise between these two measured transmissivities.
Because of the bedrock encountered beneath the aquifer and the
clay above the aquifer, equations for unsteady-state radial flow
in isotropic nonleaky aquifers with fully penetrating wells and
constant-discharge conditions were used for drawdown calculations
(Walton, 1970). The equation was
r
sl _ s2 = 527.78 log r2 C1)
1
where sl and s2 are drawdown at wells 1 and 2 respectively (feet),
Q is the pumping rate (gpm), T is the transmissivity (gpd/ft),
and rl and r2 are the distances (feet) from the center of the
• pumped well to wells 1 and 2 respectively. Because of the proximity
of the wells to the White River, the river was considered to be a
line source and was treated as such by using the technique of
image wells outlined by Walton (1970). The resultant lines of
constant long-term drawdown caused by pumping all six of the
proposed wells simultaneously were determined by superimposing
the cones of depression for each individual well and adjusting
for the image wells. The resulting lines of constant longterm
drawdown are shown in Map 102. The estimated drawdown shown in
Map 102 probably overestimates the actual drawdown that will be
experienced because six wells producing 125 gpm would yield 750 gpm,
but actual peak useage is expected to be only 601 gpm. As shown
in Map 102, the large portion of the drawdown occurs within the
• mine permit area. Presently cultivated lands will be unaffected
4/81 II.D-23