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GENERAL32420
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GENERAL32420
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Last modified
8/24/2016 7:54:59 PM
Creation date
11/23/2007 7:18:37 AM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1981013
IBM Index Class Name
General Documents
Doc Date
6/28/1990
Doc Name
Proposed Decision & Findings of Compliance for PR1
Permit Index Doc Type
Findings
Media Type
D
Archive
No
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<br />C. Ground Water - Alluvial Aquifers <br />Investigation of the alluvial ground water along the Middle fork and main <br />stem of the Purgatoire River was conducted by drilling eight holes <br />(three at the New Elk Mine, and five at the Golden Eagle Mine) through <br />the alluvium to bedrock and excavating several back hoe pits. Ground <br />water was encountered only in the alluvium in direct contact with the <br />river. The thickness and lateral extent of the saturated alluvial <br />material is limited, The water table depth in the alluvial wells ranged <br />from about 4 to 5 feet below the ground surface, and was largely <br />controlled by the water level in the river. <br />Drill holes and back hoe pits encountered no ground water in the strath <br />terraces and no prominent springs were observed near the contact between <br />the strath alluvium and bedrock. This indicates that the strath terraces <br />do not contain a water table aquifer and that these deposits are not <br />hydrologically connected to the alluvial terraces adjacent to the <br />Middle Fork and mainstream of the Purgatoire River, <br />Auger hole tests were performed to determine the hydraulic conductivity, <br />(permeability) of the alluvial flood plain materials. The permeability <br />determined from the auger hole tests ranged from 0.014 ft/d to 2 ft/d. <br />Attempts to conduct an auger hole test at one hole failed because the <br />permeability was too high. A pump test was performed on that hole, and <br />from the observed drawdown, the permeability was estimated to be about <br />1,880 ft/d. <br />The alluvial flood plain ground water is a calcium-bicarbonate type water <br />with a chemistry similar to that of the Purgatoire River (see permit <br />application Exhibit 6, Figures 12 and 14), but with slightly higher <br />concentrations of the major ions. The only significant difference with <br />respect to the major ions is an elevated sodium concentration in the <br />alluvium relative to that in the stream. Although seepage from the <br />New Elk Mine refuse pile has high sodium concentrations, mining <br />activities are not the sole cause of the elevated sodium levels. Sodium <br />is high in all four wells. The sodium is probably being contributed, in <br />part, by the dissolution of one or more sodium salts contained in the <br />soils or alluvium. <br />Concentrations of major ions and the conductivity of alluvial wells at <br />the downstream Golden Eagle Mine site are less than the concentrations <br />and conductivities of wells at the New Elk Mine site (Exhibit 6, <br />Table 3), This is probably the result of inflows of better quality water <br />from the North Fork of the Purgatoire that joins the Middle Fork of the <br />Purgatoire between the two mine sites. <br />D. Surface Water <br />The Purgatoire River, a tributary of the Arkansas River, is the major <br />surface drainage feature of the area. The headwaters of the Purgatoire <br />are located on the eastern slope of the Sangre de Cristo Range west of <br />the study area. The three major branches of the river, the North Fork, <br />Middle Fork, and South Fork, all converge within the study area. The <br />New Elk Mine is located on the Middle Fork, about 1.5 miles upstream of <br />the confluence of the North and Middle Forks of the river. <br />-13- <br />
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