1991-10-07_PERMIT FILE - M1991123 ‎(5)‎

• Permit No: M1991123
• IBM Index Class Name: Permit File
• Doc Date: 10/7/1991
• Doc Name: REGULAR OPERATION 112 RECLAMATION PERMIT APPLICATION FORM
• Media Type: D
• Archive: No

Moisture Loss is Materials
All of the mine material hauled from the site will contain moisture
from groundwater and the washing operation. Generally sand and
gravel contains a 4% moisture content after it has been left in a
stockpile for at least one week. This amount is the accepted
industry standard for replacement. The volume of material mined is
market driven and will vary from year to year. An average year is
expected to produce 160, 000 tons of material. This will consume
4 . 71 acre-feet of water.
Evaporative Losses
The proposed mining operation would create a lake with a water
surface area of 58 .7 acres. This would be the final configuration
and would only occur after the dewatering pumps had been stopped
and the lake allowed to refill. When the lake refills, the average
annual evaporative loss will probably range between 2 .0 to 2 .5
acre-feet per acre. Therefore, the expected depletion that must be
replaced would be 117 .4 to 146.8 acre-feet. There is an allowance
for historic credits for evaporation due to historic groundcover.
Therefore, there should be some additional credit allowance in the
water balance. The high groundwater table would justify a credit
of at least 12 inches of subirrigation which would reduce the net
evaporative loss down to 58.7 to 88.0 acre-feet.
The mining project will also be straightening Idaho Creek to
optimize the mining of the resource. In doing this, approximately
1, 120 feet of the creek will be eliminated which in turn reduces
evaporative losses to the stream system. It is estimated 0.26
acres of exposed water will be eliminated which would equate to
0.64 acre-feet per year reduction in the liability for
augmentation.
The total consumptive use of the project during mining would be as
follows:
Description Consumptive Use
Process Waters 0. 14 of
Dust Control 0.70 of
Moisture Loss 4 .71 of
Evaporative Loss 88.00 of
TOTAL WATER CONSUMPTION 93.55 of (maximum)
The evaporative loss will increase in a linear advancement as
mining progresses. As long as dewatering is continued, there will
be no losses due to evaporation other than evaporation from exposed
water in the dewatering trench.
G-4