2006-06-07_PERMIT FILE - C1996083

• Permit No: C1996083
• IBM Index Class Name: Permit File
• Doc Date: 6/7/2006
• Doc Name: 02/15/2006 Gob Pile #2 Stability Evaluation TR-42 Buckhorn Geotech Inc
• Section_Exhibit Name: Volume IX Coal Waste Disposal Area No. 2
• Media Type: D
• Archive: No

pressures are a key component of stability of the coal waste stockpile. Monitoring of the
vibrating wire piezometers is discussed in Section 5.1 of this report.
The vibrating wire piezometers were manufactured by Slope Indicator, Inc. The piezometers
have a built in thermistor and have a pressure range of 0 to 100 psi. The piezometers were
installed at depths and locations indicated in Table 2 and as presented on the attached Site Plan.
The piezometers were grouted in -place using a bentonite- cement grout. Cables for four of the
five piezometers have been routed to the lower bench at the south face of the coal waste
stockpile. The cable ends are housed in electrical boxes allowing for monitoring access and
providing protection. The cable for piezometer VWP -04 has not yet been routed to the face of
the stockpile due to possible changes to the slope and access road between the piezometer and
the lower bench. Bowie has been placing coal waste around the piezometer with care not to
damage the instrument. Buckhorn recommends routing the cable to a safe location as soon as the
long -term location of the access road is known.
Table 2. Summary of Piezometer Locations
Piezometer
Serial
Borehole
Approx.
ID
No.
ID
Piezometer
Elevation (ft)
VWP -01
82412
BG05 -01
6,030
VWP -02
82415
BG05 -02
6,011
VWP -03
82414
BG05 -02
6,026
VWP -04
82413
BG05 -03
6,048
VWP -05
82416
BG05 -06
5,991
On January 11, 2006, the reading of piezometer VWP -01 indicated the instrument had been
damaged. Diagnostic tests performed with a multi -meter indicate that the cable has likely been
damaged and a short has developed. Damage occurred during the time between November 22,
2005 and January 11, 2006. It is unlikely that the piezometer can be repaired.
3.3 Inclinometers
A total of three inclinometers were installed in three of the drilled boreholes. Inclinometers are
utilized to monitor ground movement, rates of movement and can detect the depth(s) of
movement. The inclinometers are ABS plastic pipe designed to deform with movement of
adjacent ground. The inclinometer casing is typically installed 10 to 20 feet into a soil or
bedrock zone that is considered to be stable (i.e., below the potential shear zones). The casing
has four orthogonal precision grooves cut longitudinally along the inside of the pipe. Monitoring
is conducted by inserting a wheeled probe into the grooves and taking readings of the
inclinometer tilt at specified depths along the entire inclinometer. The first monitoring event is
the "baseline" reading and is conducted shortly after installation. Subsequent monitoring events
are compared to the baseline reading to detect any ground movement. At Bowie, we have
proposed to monitor the inclinometers on a quarterly basis.
Inclinometers were installed through the placed coal waste and into the native foundation soils.
The three inclinometers were installed in boreholes BG05 -04, BG05 -05, and BG05 -07. As
indicated on the attached Site Plan, these boreholes are all located on the lower bench at the
Bowie No 2 Gob Pile Stability Dec2005
Project #05- 126 -GEO
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