2008-04-30_REPORT - M1973021 ‎(3)‎

• Permit No: M1973021
• IBM Index Class Name: REPORT
• Doc Date: 4/30/2008
• Doc Name: Geotechnical Addendum/ 2007 Annual Report
• From: Tetra Tech
• To: DRMS
• Permit Index Doc Type: Annual Reclamation Report
• Media Type: D
• Archive: No

joint set 2 average spacing was 20 inches. Joint set 1 exhibited closed, slightly rough
• faces while joint set 2 was moderately open, up to 0.5 inches with slightly rough faces.
• Stations 0+50 through 0+90 consisted of biotite gneiss. The foliation strike ranges
from 0 to 10 degrees with dips ranging between 23 and 32 degrees with an average
• spacing of 6 inches and moderately open, slightly smooth, wavy faces. The foliation
dips slightly out of the highwall. The primary joint set strike ranges from 135 to 140
degrees and generally dips from 47 to 55 degrees. The secondary joint set strike ranges
from 224 to 230 degrees with dips of 56 to 65 degrees. The spacing of joint set 1
• averaged 8 inches while the spacing of joint set 2 averaged 14 inches. Joint set 1
t Joint set
th
lik
l
I
i
a
e
y
t
s
exhibits open (up to 4 inch) apertures with slightly rough faces.
1 in this area is subject to minor toppling potential. Joint set 2 had moderately open
• apertures displaying slightly rough faces.
• Stations 0+90 to 1+50 consisted of biotite gneiss with tight joint spacing. The foliation
strike ranges from 140 to 150 degrees with dips ranging between 12 and 20 degrees
• with an average spacing of 1.5 inches and moderately open, slightly rough faces. The
foliation dips into the highwall. The primary joint set strike ranges from 130 to 138
degrees and generally dips from 50 to 60 degrees. The secondary joint set strike ranges
• from 215 to 225 degrees with dips of 74 to 82 degrees. The average spacing of both
• joint sets was 3 inches and both joint sets exhibited moderately open to closed
apertures with slightly rough faces.
Stations 1+50 to 2+00 consisted of biotite gneiss. The foliation strike ranges from 95 to
105 degrees with dips ranging between 15 and 23 degrees with an average spacing of
12 inches and moderately open, slightly smooth, wavy faces. The foliation dips into
the highwall. The primary joint set strike ranges from 275 to 285 degrees and
generally dips from 38 to 47 degrees. The secondary joint set strike ranges from 0 to 5
degrees with dips of 73 to 81 degrees. The spacing of joint set 1 averaged 24 inches
while the spacing of joint set 2 averaged 8 inches. Joint set 1 exhibits moderately open
apertures with slightly smooth faces. Joint set Z had moderately open apertures
displaying slightly rough faces.
Figure 6 is a photo documentary of the features observed in Bench 1.
4.0 RESULTS AND DISCUSSION
Observations of the Central Quarry indicate little change in the finished slopes. Local rock
sloughing was observed and was classified as minor based on rock accumulations observed on
bench surfaces throughout the Central Quarry. The general condition of the highwalls is
anticipated to remain stable with only small scale rockfall expected to occur.
The baseline rock conditions described in Amendment 3 to Mining Permit M-1973-021 are
"competent" for granite or biotite gneiss and "poor" for shear zones or highly to extremely
weathered zones that have the potential to decrease the stability of the slope. The conditions
observed in highwalls mined in 2007 in the North Quarry indicate that the rock is
predominantly "competent" with localized areas of "poor". Further, no features were observed
that are anticipated to cause large block size failures. Markland orientation data indicates very
-6-
F:\3919 038\Annual_Rcport_2007\Gcotech_Addendum_2007Wnnual_Report_2007_Geotech.doc April 2008