2011-01-04_PERMIT FILE - C1981012

• Permit No: C1981012
• IBM Index Class Name: Permit File
• Doc Date: 1/4/2011
• Doc Name: DEVELOPMENT WASTE DISPOSAL AREA DESIGN
• Section_Exhibit Name: Exhibit 37 Development Waste Disposal Area Design
• Media Type: D
• Archive: No

Draft: August 23, 2010
3.0 LABORATORY TESTING
Page 4
Samples of the coal refuse at the current DWDA site, development waste from the
current rehabilitation work, and subgrade materials from DH -6 were sent off for testing at the
Huddleston -Berry Engineering and Testing laboratory (HB) in Grand Junction, Colorado. Due
to the rocky nature of the materials, re- molded direct shear tests were run on the material passing
the #4 mesh (4.76 millimeters [mm]) screen. The coal pond refuse and the development waste
samples were re- molded at 90% relative compaction based on the standard proctor
(ASTM D698) maximum compaction. The subgrade material was prepared at 85% relative
compaction based on the standard proctor maximum compaction. Table 1 presents the results of
the laboratory testing.
Table 1. Laboratory Test Results
4.0 COMPUTER MODELING
The proposed DWDA has a maximum width of approximately 168 feet (ft). AAI
recommends that a berm be constructed around the pile to collect any storm water runoff. A
3 -ft -tall berm will occupy approximately 14 ft per side, leaving 140 ft for the base of the pile.
The minimum width at the top should not be less than 20 ft. Using a 2:1 horizontal: vertical
slope, would result in a maximum height of 30 feet. This height was modeled using Geo- Slope's
ft
Slope/W soware to model various DWDA slope configurations. Table 2 presents the results of
the computer modeling. Figures 3 through 14 present the results of the analyses.
Table 2. Factors of Safety for Various Slope Conditions
Maximum
Depth to
Ultimate
Ultimate
Remolded
Phreatic Surface
Material Description
Sample ID
Test Saturation
Friction Angle 0 Cohesion
Compaction
Standard Proctor
2.0:1.0
0
2.859
Coal pond refuse
1.5:1.0
0
optimum Moisture
Coal pond refuse
1.0:1.0
(%)
(degrees)
(pst)
( %)
(pct) Content ( %)
Coal pond refuse
DWRDA -1
100
23
1092
91.0%
96.7 12.8
Development waste
DWRDA -2
100
37
461
90.2%
116.4 11.9
Subgrade materials
DH -6
100
38
767
84.6%
99.3 13.0
4.0 COMPUTER MODELING
The proposed DWDA has a maximum width of approximately 168 feet (ft). AAI
recommends that a berm be constructed around the pile to collect any storm water runoff. A
3 -ft -tall berm will occupy approximately 14 ft per side, leaving 140 ft for the base of the pile.
The minimum width at the top should not be less than 20 ft. Using a 2:1 horizontal: vertical
slope, would result in a maximum height of 30 feet. This height was modeled using Geo- Slope's
ft
Slope/W soware to model various DWDA slope configurations. Table 2 presents the results of
the computer modeling. Figures 3 through 14 present the results of the analyses.
Table 2. Factors of Safety for Various Slope Conditions
Geo -Slope International (2009), GeoStudio 2007, Version 7.14, April 20.
Agapito Associates, Inc.
Maximum
Depth to
DWDAMaterial
Slope
Phreatic Surface
Factor of Safety
(H: V)
(ft)
Coal pond refuse
2.0:1.0
0
2.859
Coal pond refuse
1.5:1.0
0
2.350
Coal pond refuse
1.0:1.0
0
2.261
Development waste
2.0:1.0
0
2.132
Development waste
1.5:1.0
0
1.668
Development waste
1.0:1.0
0
1.253
Alternating pond —first
2.0:1.0
0
2.535
Alternating development —first
2.0:1.0
0
2.549
Development waste
1.5:1.0
10
2.275
Development waste
1.5:1.0
20
2.709
Development waste
1.5:1.0
30
2.719
Geo -Slope International (2009), GeoStudio 2007, Version 7.14, April 20.
Agapito Associates, Inc.