2017-04-14_HYDROLOGY - C1996083 ‎(2)‎

• Permit No: C1996083
• IBM Index Class Name: Hydrology
• Doc Date: 4/14/2017
• Doc Name Note: Impoundment Report
• Doc Name: Quarterly Sediment Pond/Impoundment Report
• From: J.E. Stover & Associates, Inc.
• To: DRMS
• Annual Report Year: 2017
• Report Quarter_Month: 1
• Permit Index Doc Type: Sediment Pond Inspections
• Email Name: CCW
• Email Name: JRS
• Media Type: D
• Archive: No

CWDA No. 2
#01349-0001 ]H[uddlrston Berry
04/11/17 ��1 lnilnmini&Tn inp LLC
Discussion of Inclinometer Monitoring
Some minor movement was observed in the data for BG05. However, the movement was in the
direction parallel to the face of the gob. In addition, the data profile was consistent with previous
data and may simply reflect a measurement error. In general, 1St Quarter 2017 monitoring data
does not provide any indication of instability in CWDA No. 2.
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 March 10', 2017. 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)
12/14/16 Pore
Pressure
(psi)
03/10/17 Pore
Pressure
(psi)
Difference Since
Installation
(psi)
Difference
Since Last
Reading (psi)
VWP-05
6.8
2.0
1.9
-4.9
-0.1
VWP-06
11.3
13.6
13.6
+2.3
0.0
VWP-08
1 8.2
9.9
9.8
+1.6
-0.1
VWP-09
1 2.8
2.8
2.9
+0.1
+0.1
VWP-10
1 -1.9
-1.8
-1.7
+0.2
+0.1
Discussion of Vibrating Wire Piezometers
VWP-05
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 small. In 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. In general, the fluctuations
have been seasonal and reflect the level of coal mine waste placement activity on top of CWDA
No. 2. Although an increase was recorded in the 1St Quarter 2016, the pore pressures recorded in
VWP-06 decreased and then stabilized since then. 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. The measured pore pressures are generally
consistent with the level of coal mine waste placement activity at CWDA No. 2.
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\Instrumentation Monitoring\2017\01349-0001 GP2 1stQ 2017 L041117.doc 2