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REV10086
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REV10086
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Entry Properties
Last modified
8/25/2016 1:11:21 AM
Creation date
11/21/2007 10:09:39 AM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
M1977342
IBM Index Class Name
Revision
Doc Date
8/27/1996
Doc Name
GROUND WATER MONITORING PROGRAM HENDERSON MINE & MILLE TR5 PN M-77-342
From
DMG
To
CLIMAX MOLYBDENUM CO
Type & Sequence
TR5
Media Type
D
Archive
No
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<br />Letter to J.J. Jones -4- August 27 1996 <br />monitored at wells GW-7 and GW-6, with well GW-7 designated as a point of <br />compliance for meeting numeric protection levels. The Division and CMC <br />have disagreed on the need to monitor ground water in the precambrian <br />basement rock. It is CMC's position that the precambrian basement rock <br />is much less permeable than the overlying Troublesome/glacial/alluvial <br />unit, and, as such, the precambrian basement rock will not transmit <br />significant quantities of ground water relative to the overlying <br />glacial/alluvial ground water unit. CMC's conclusions are based on packer <br />tests in the precambrian unit that were conducted during 1969 and 1970 at <br />a location approximately two miles from the location of the point of <br />compliance monitoring well, and on a single pump test conducted in 1993 <br />in the upper ground water unit. <br />It is the Division's position that the packer tests conducted at the East <br />Branch Reservoir dam site may not be representative of conditions beneath <br />and down gradient from the tailing impoundment, and even if the packer <br />tests are representative, it is the Division's position that a ground <br />water unit with an average hydraulic conductivity of 3.6x10-5 cm/sec and <br />a peak hydraulic conductivity of 2.9x10_q cm/sec is capable of <br />transmitting significant quantities of ground water, particularly if a <br />stronger hydraulic gradient is imposed on the lower unit ground water than <br />is acting on the upper unit ground water. In further support of the <br />Division's position, the packer tests of the type employed at the East <br />Branch Reservoir dam site may underestimate hydraulic conductivity by as <br />much as an order of magnitude. Also, packer tests do not measure vertical <br />hydraulic conductivity, which is a critical consideration in understanding <br />the potential rate of seepage from the tailings into the basement rock, <br />and understanding ground water movement that may occur between the two <br />ground water units that have been identified. In addition, ground water <br />velocity in the fracture controlled basement rock ground water unit may <br />be much higher than the velocity in the granular materials of the upper <br />ground water unit. Higher ground water velocity in the basement rock <br />would diminish the opportunity for ground water cleansing (e.g. <br />adsorption) along the flow path. Given the uncertainties regarding ground <br />water flow in the basement rock, the Division continues to believe that <br />a monitoring well in the basement rock ground water unit is needed, and <br />that a point of compliance needs to be established. Such a monitoring <br />well can be used to characterize existing water quality conditions upon <br />which numeric protection levels for the basement rock ground water unit <br />will be based. Characterization of existing ground water quality at this <br />time may serve to protect CMC from the potential application of the <br />default provisions of the Interim Narrative Standard at some time in the <br />future. <br />A well design that incorporates a packer that will isolate the screened <br />interval is critical to assure that only ground water derived from the <br />basement rock is sampled. The well design also needs to incorporate a <br />relatively long screened interval to better assure that ground water <br />inflows to the well will be sufficient to allow representative sampling. <br />The Division would prefer to work with CMC to reach an agreement on the <br />
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