2015-10-19_REPORT - C1996083 ‎(2)‎

• Permit No: C1996083
• IBM Index Class Name: Report
• Doc Date: 10/19/2015
• Doc Name: 3rd 2015 Quarter refuse pile inspection report
• From: J.E. Stover & Associates, Inc
• To: DRMS
• Permit Index Doc Type: Waste Pile/Fill Report
• Email Name: JDM
• Email Name: DIH
• Media Type: D
• Archive: No

CWDA No. 2
#01349-0001
10/14/15
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Discussion of Inclinometer Monitoring
The latest inclinometer readings indicate no significant movements since the last quarterly
reading.
Vibrating Wire Piezometers
Between 2005 and 2012, a total of ten vibrating wire piezometers were installed in CWDA No.
2. However, several of the piezometers have been damaged or have otherwise ceased to
function. Currently, five of the piezometers are functional.
Monitoring of the functioning piezometers was completed by DOWL on September 26th, 2015.
The attached monitoring report prepared by DOWL includes the piezometer monitoring data and
the data is summarized in the following table.
VWP
ID
Initial Pore
Pressure
(psi)
06/26/15 Pore
Pressure
(psi)
08/01/15 Pore
Pressure
(psi)
09/26/15 Pore
Pressure
(psi)(psi)
Difference Since
Installation
Difference
Since Last
Reading (psi)
VWP-05
6.8
1.8
2.2
-4.6
+0.4
VWP-06
11.3
15.9
15.7
15.4
+41
-0.3
VWP-08
8.2
9.7
9.8
9.9
+1_7
+01
VWP-09
2.8
2.9
2.9
+0.1
0
VWP-10
-1.9
-1.8
-1.8
+0.1
0
Discussion of Vibrating Wire Piezometers
VWP-n 5
VWP-05 was installed on August 3, 2005 near the toe of CWDA No. 2 adjacent to the access
road/bench. The pore pressures recorded at VWP-05 have shown some seasonal fluctuations;
however, the range of pore pressure changes is fairly smallln general, HBET does not believe
that the pore pressures in VWP-05 are cause for concern regarding stability of the gob pile.
VWP-06
VWP-06 was installed on June 5, 2009 near the existing top of CWDA No. 2. The pore
pressures recorded at VWP-06 have fluctuated since installation. The pore pressures increased
following installation until March 2013 and then fell until April 2014. However, between April
2014 and August 2014, the pore pressures again increased. This likely reflects the fact that gob
placement was occurring in the vicinity of this instrument during the spring and summer 2014.
There was a slight decrease between August 2014 and January 2015 which likely reflects the fact
that gob placement operations slowed and finally ceased for the winter. A slight increase was
reported between January 2015 and March 2015. However, the pore pressures have been
decreasing since March 2015. In general, HBET does not believe that the measured pore
pressures are an indication of any instability in CWDA No. 2.
VWP-08
VWP-08 was installed on June 5, 2009 at a slightly lower elevation than VWP-06. The pore
pressures recorded at VWP-08 have fluctuated since installation. However, the fluctuations have
generally been within a narrow range of values. Slight pore pressure increases were recorded in
VWP-08 from April 2014 through January 2015. However, a slight decrease occurred between
January and March 2015. Since March 2015, pore pressures have increased slightly. As
indicated in the referenced Stability Evaluation report, the stability of CWDA No. 2 is sensitive
to increases in pore pressures in VWP-08. An increase in the pore pressure of 7 psi in VWP-08
would result in a reduction of the Factor of Safety to below 1.5.
X:\2008 ALL PROJECTS\01349 -Bowie Resources, LLC\01349-0001 Bowie Mine\200 - Geo\Gob 2\Imtr ntation Monitoring\2015\01349-0001 GP2 3rdQ 2015 101415.doe 2