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

Locations of the majority of the boreholes were surveyed. Borehole locations are summarized in
Table 1 and are presented on the Site Plan in Appendix A.
Table 1. Summary of Borehole Locations
The boreholes were generally drilled with a 4'/4 -inch solid stem continuous flight auger. Portions
of the native soil and bedrock were cored using an HQ wireline coring system. Soil samples
were generally obtained at 10 -foot depth increments using a two -inch I.D. split -spoon
"California" sampler. Standard penetration tests (SPT) were conducted in general accordance
with ASTM D 1586 to characterize the consistency of the coal waste. The recovered soil and
bedrock were logged by a geotechnical engineer, and representative samples of subsurface
materials encountered were brought back to our laboratory for detailed examination and testing.
The stratigraphy encountered in the borings and laboratory results are presented in Appendix B.
The composition of the coal waste encountered during drilling varied from lean clay with
variable sand and gravel contents to clayey gravel with sand to clayey sand with gravel. The
material was typically damp to moist with stiff to very stiff consistency. N- values in the coal
waste material ranged from 9 to 40 blows per foot with an average N -value of 22.
Native soils were encountered at depths ranging from 28.5 to 59 feet. Native soils were typically
damp to moist, firm to hard, clayey sand with gravel to lean clay with gravel. Sandstone with
interbedded shale bedrock was encountered in boreholes BH05 -04 and BH05 -05.
3.2 Vibrating Wire Piezometers
A total of five vibrating wire piezometers were installed in four boreholes in June 2005. The
vibrating wire piezometers are pressure transducers consisting of a tensioned steel wire
connected to a diaphragm. Changes of water pressure on the diaphragm result in changes in the
tension of the wire. When the steel wire is excited by a magnetic coil, the wire vibrates at its
natural frequency. The frequency of the vibrating wire is related to the water pressure acting on
the diaphragm. Using calibration factors, the water pressure can be determined from reading the
frequency of the vibrating wire via a portable readout device. Calibration records for the
piezometers are included in Appendix C. As discussed in Section 6.0 of this report, the water
Bowie No 2 Gob Pile stability Dec2005
Project #05- 126 -GEO
Page 6 of 18
Elevation
Borehole ID
Northing
Easting
(ft)
BG05 -01
19351
37846
6,058
BG05 -02
19307
37631
6,061
BG05 -03
19287
37355
6,063
BG05 -04
19094
37985
6,018
BG05 -05
18991
37824
6,018
BG05 -06
18993
37831
6,018
BG05 -07
18980
37494
6,014
BG05 -08
19333
37675
6,066
BG05 -09
Not Surveyed
BG05 -10
Not Surveyed
BG05 -11
19257
37613
6,062
The boreholes were generally drilled with a 4'/4 -inch solid stem continuous flight auger. Portions
of the native soil and bedrock were cored using an HQ wireline coring system. Soil samples
were generally obtained at 10 -foot depth increments using a two -inch I.D. split -spoon
"California" sampler. Standard penetration tests (SPT) were conducted in general accordance
with ASTM D 1586 to characterize the consistency of the coal waste. The recovered soil and
bedrock were logged by a geotechnical engineer, and representative samples of subsurface
materials encountered were brought back to our laboratory for detailed examination and testing.
The stratigraphy encountered in the borings and laboratory results are presented in Appendix B.
The composition of the coal waste encountered during drilling varied from lean clay with
variable sand and gravel contents to clayey gravel with sand to clayey sand with gravel. The
material was typically damp to moist with stiff to very stiff consistency. N- values in the coal
waste material ranged from 9 to 40 blows per foot with an average N -value of 22.
Native soils were encountered at depths ranging from 28.5 to 59 feet. Native soils were typically
damp to moist, firm to hard, clayey sand with gravel to lean clay with gravel. Sandstone with
interbedded shale bedrock was encountered in boreholes BH05 -04 and BH05 -05.
3.2 Vibrating Wire Piezometers
A total of five vibrating wire piezometers were installed in four boreholes in June 2005. The
vibrating wire piezometers are pressure transducers consisting of a tensioned steel wire
connected to a diaphragm. Changes of water pressure on the diaphragm result in changes in the
tension of the wire. When the steel wire is excited by a magnetic coil, the wire vibrates at its
natural frequency. The frequency of the vibrating wire is related to the water pressure acting on
the diaphragm. Using calibration factors, the water pressure can be determined from reading the
frequency of the vibrating wire via a portable readout device. Calibration records for the
piezometers are included in Appendix C. As discussed in Section 6.0 of this report, the water
Bowie No 2 Gob Pile stability Dec2005
Project #05- 126 -GEO
Page 6 of 18