2018-11-21_REVISION - M2004044 ‎(22)‎

• Permit No: M2004044
• IBM Index Class Name: Revision
• Doc Date: 11/21/2018
• Doc Name Note: Part 5 of 5
• Doc Name: Request For Amendment To Permit
• From: Aggregate Industries-WCR
• To: DRMS
• Type & Sequence: AM1
• Email Name: JLE
• Email Name: MAC
• Media Type: D
• Archive: No

T
TETRA TECH Updated Tucson South Proposed Gravel Mine Slope Stability Analysis
N
November 9, 2018
4.2 INPUT PARAMETERS
Each section was modeled to resemble the existing site topography. Material thicknesses were modeled based
on previous drilling on the site. In general, the sand and gravel were thinner on the west side of the site. The
materials were assumed to be horizontal in the subsurface.A three-foot thick weathered claystone bedrock was
modeled based on a letter from Allen Sorenson to Kate Pickford dated March 6, 20037. The sections modeled
should not be used as an estimation of the aggregate resource.
The input parameters for each of the materials used were those required for the 2004 analysis and are based on
a memo from Allen Sorenson to Larry Oehler, dated August 29, 20048. The material properties are presented in
Table 1. All materials were modeled using the Mohr/Coulomb framework.
Table 1:Material parameters used in the slope stability models8.
Material Parameters
Material Moist Unit Weight Saturated Unit Effective Effective
(pcf) Weight(pcf) Cohesion c' (psf) Friction Angle
4)' (degrees)
Overburden 114 126 50 28
Sand & Gravel 130 137 0 35
Weathered Claystone 124 134 0 14
Bedrock (residual
strength)
Claystone Bedrock 124 134 100 28
(peak strength)
Mud Lens 114 126 50 28
Slurry Wall 110 122 0 0
*pcf=pounds per cubic foot;psf=pounds per square foot
A seismic analysis was also conducted for each of the sections. The seismic analysis accounts for the effects of
horizontal acceleration experienced during an earthquake. The horizontal acceleration used was 0.067 g. The
value was obtained from a U.S. Seismic Design map of the areas. The U.S. Seismic Design Maps program
considers the soil classification and location of the site. For the Tucson South site, Site Class D—Stiff Soil was
used.
Other applicable DRMS requirements that were used are as follows:
• Highwalls were modeled as vertical slopes.
• The minimum factor of safety for the static analysis is 1.5.
• The minimum factor of safety for the seismic analysis is 1.3.
The scenarios were modeled with entry/exit geometry for currently proposed setbacks. The setbacks were
adjusted as needed to reach the minimum required factor of safety in each case.
Sorenson, A. (2003, March 6). RE: Pit Wall Stability Analysis, Irwin Corporation, Bernhardt Resource Gravel Pie,
Permit No. M-2002-120. Denver, CO.
8Sorenson, A. (2004, August 29). RE: Reclamation Cost Estimate and Pit Wall Stability Analysis, Aggregate
Industries, Tucson South Resource Gravel Pit, File No. M-2004-044.
s U.S. Geological Survey. (2017, July 27). U.S. Seismic Design Maps. U.S. Geological Survey.
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