2016-07-14_PERMIT FILE - M2016010 (4)

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A*Ah Transit Mix Concrete Co. DRMS COMMENTS—PETER HAYS—REVIEW OF EXHIBIT 6.5 - GEOTECHNICAL Comment: The following list describes the information used by the Division as presented in the permit application to evaluate slope stability for the proposed quarry. Please review the list and confirm the list is accurate. • The Geotechnical Assessment was based on seven(7) boreholes completed by Norwest Corporation(Norwest) and six (6)boreholes completed during a previous site investigation by another company. • Granite and granite composites are the most common rock types within the proposed quarry and pit wall locations. • The rock mass was characterized using the 1989 version of the Rock Mass Rating System. Points were assigned using the following categories; Uniaxial Compressive Strength(UCS), Rock Quality Designation(RQD), Discontinuities Spacing, Discontinuities Condition and Groundwater Conditions. • Groundwater levels were not identified during drilling due to the use of drilling mud. • Stability analysis models were performed assuming saturated groundwater conditions. • The overall stability analysis was performed for five (5) cross-sections at various wall heights and orientations. • A bench stability analysis was performed for each rock type and condition for a 40 foot bench height at a 2V:1H slope. • The geotechnical analysis was performed by Norwest using GeoStudio software SLOPE/W Version 8.4. • The wall heights used in the overall analysis varied from 275 feet to 410 feet. • The proposed bench dimensions are forty(40) feet in height and twenty(20) feet in width. • The bench highwall angle was designed at 63 degrees, 2V:1H. • A Factor of Safety of 1.3 for Static and 1.0 for Pseudo-Static Conditions design criteria was used for the bench scale slope analysis. • The overall highwall angle was designed at 45 degrees, 1 H:IV. • A Factor of Safety of 1.5 for Static and 1.0 for Pseudo-Static Conditions design criteria was used for the overall slope analysis. • The TS 1 - Topsoil Stockpile facility will contain 317,000 bank cubic yards of topsoil. • The F1 - Fines/Overburden Stockpile will be constructed with 314:1V slopes. Response: See table below. Hitch Rack Ranch Quarry (M-2016-010) Response to Comments—July 14, 2016