2014-01-06_REVISION - M2000041

• Permit No: M2000041
• IBM Index Class Name: REVISION
• Doc Date: 1/6/2014
• Doc Name: Response to Adequacy of October 7, 2013 AM01
• From: Environmental Alternatives, Inc
• To: DRMS
• Type & Sequence: AM1
• Email Name: TC1
• Media Type: D
• Archive: No

geotechnical investigation, groundwater elevations in bore holes near the open pit were likely
influenced by dewatering. Several other factors likely influence the alluvial groundwater
elevations and gradients on and near the project site. The aquifer is confined on the southern
boundary by the Arkansas River and the alluvium pinches out approximately one -half mile north
of the property. Irrigation canals and ditches, agricultural wells, and irrigated lands on and
adjacent to the property likely provide depletions and recharge to the alluvial groundwater
system that create seasonal and localized fluctuations in groundwater elevations and gradients.
Table 2
Summary of May 2006 Selected Bore Hole Gradation Data
Exploration
D10(')
D50(2)
1360 (3)
Uniformity
Sand (5>
Hydraulic (6)
Hole
(mm)
(mm)
(mm)
Coeff.(4)
Fraction
Conductivity
( %)
(feet/day)
THM -5
9.2
73
9.5'- 11.0'
0.16
0.42
0.59
3.7
88.2
80
2.6
94
THM -5
53.2
477
19.5' - 21.0'
0.41
5.5
11
27
44.1
303
2.7
n/a
THM -16
18.9
290
9.5 - 11.0'
0.31
3.4
6.5
21
78.8
206
2.3
n/a
THM -16
20.7
409
19.5' - 21.0'
0.39
2.0
3.0
7.7
76.7
387
2.6
177
39.7
524
Bulk Sample
0.43
2.8
4.9
11.4
59.9
444
0.4
n/a
(1) 10% of the particles in the sample are smaller than this diameter.
(2) 50% of the particles in the sample are smaller than this diameter.
(3) 60% of the particles in the sample are smaller than this diameter.
(4) Uniformity Coefficient = D60/D10
(5) Sample composition: gravel (top )/sand (middle) /fines (bottom)
(6) Method results for estimating hydraulic conductivity: Hazen Method from Fetter 1994 (top)Beyer
Method from Kresic 2006 (middle)/Prugh graphical method from Powers 2007 (bottom, n/a = method
not applicable)
Groundwater elevations and average estimates of the alluvial saturated thickness taken from the
site bore log data are consistent with values obtained from published data for the Arkansas River
valley. Reference material (Nelson et al. 1989 and USGS 2002) suggests that the alluvial
groundwater elevation across the site should be about 4514 to 4520 feet above mean sea level
(amsl) with annual and seasonal fluctuations of several feet and a saturated thickness ranging
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