2008-04-15_REVISION - M1980244 ‎(325)‎

• Permit No: M1980244
• IBM Index Class Name: REVISION
• Doc Date: 4/15/2008
• Doc Name: VOL II Appendix 2, Hydrologic Evaluation Report
• From: CC & V
• To: DRMS
• Type & Sequence: AM9
• Media Type: D
• Archive: No

Grassy Valley hydrologic conditions 23
the piezometers are shown on Figure 4.1. Direct rotary drilling was performed.
Geologic logging was conducted in the field by WMC staff, and included documentation
of lithology, color, evidence of oxidation, zones where rates of penetration changed
significantly, well construction details, etc. Borehole logs and field notes are provided in
Attachment B. Piezometers were constructed with 2-inch diameter PVC casing, and
screens consisted of 2-inch diameter PVC with 20-slot machine-slotted screens. Table
61 (Attachment B) provides construction details, total depths and screened intervals for
the piezometers.
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•
The second phase of field work was conducted during August 10 through 20, 2007, and
consisted of the drilling and installation of three additional bedrock wells and two alluvial
monitoring wells. The locations of these wells are shown on Figure B-1 (and Figure 4.1).
Direct rotary drilling was performed. Geologic logging was conducted in the field by
WMC staff, and included information on lithology, color, evidence of oxidation, zones
where rates of penetration changed significantly, well construction details, water strikes,
and air lift flow rates. Borehole logs and field notes are provided in Attachment B. Wells
were constructed with 2-inch diameter PVC casing, and screens consisted of 2-inch
diameter PVC with 20-slot machine-slotted screens. Table 61 (Attachment B) provides
construction details, total depths and screened intervals for the new monitoring wells.
4.3 Grassy Valley hydrologic and hydrogeologic conditions
The hydrologic and hydrogeologic conditions in Grassy Valley drainage have been
assessed through CC&V exploration activities, several field programs and hydrologic
monitoring data. Surface water and groundwater quality monitoring data have been
collected at several locations by CC&V personnel. Data through the end of 2007 are
summarized in Attachment C and are described briefly below.
4.3.1 Geology
Grassy Valley is underlain by both Tertiary diatreme and Precambrian Pikes .Peak
granites. The upper reaches of Grassy Creek and much of the north side of the valley
are underlain by granites. The northwestern and southern portions of Grassy Valley are
underlain by an area of the diatreme which is distinct from the main body of the diatreme
with regard to some structural and hydrogeologic characteristics (Adrian Brown, 2008).
On the hillslopes of Grassy Valley, the bedrock is overlain by a layer of unconsolidated
alluvium/colluvium (alluvium); in the valley bottom, riparian areas are underlain by
alluvial sediments. The MLE components in Grassy Valley (ECOSA and East Cresson
WHEX portion of the East Cresson surface mine) occur mainly over the diatreme rocks
on the south side of Grassy Valley.
4.3.2 Surface Water
Surface water conditions in Grassy Valley are monitored at three locations, designated
GV-01, GV-02 and GV-03. Monitoring locations are shown on Figure 4.1.
2736 - Cripple Creek & Victor Gold Mining Company
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