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provided in terms of the mechanics of earthmoving as to how the <br />prescribed slope angle will be maintained. The Applicant must further <br />describe the surveying and monitoring controls that will be employed <br />to check the slopes and the frequency of the surveying and monitoring. <br />These slopes are actively established by heavy equipment, commonly <br />an excavator. The excavator's eye is the best monitor and surveyor of <br />slope. The act of extraction creates active walls that the excavator will <br />not allow to exceed the stated limits. <br />It is the daily duty of our mines supervisors and managers to assure <br />MSHA levels of safety to our operations. In this instance, the <br />observation of pit walls will be ongoing and active with operations on <br />a daily basis. <br />Where the wall lies adjacent to a significant and valuable man-made <br />structure, staff will look for evidence of slumping or cracks in the <br />passive wall pending grading. Active walls simply will not be allowed <br />to be left at anytime steeper than 1.25H:1 V, and will commonly be <br />flatter. <br />The Applicant must state definitively that the 1.25H:1 V slopes will be <br />maintained throughout the excavation, regardless of the distance from <br />the working face to a protected structure, or must provide a plan for <br />where and what distance from structures the working face will <br />transition from steeper slopes to the prescribed 1.2511:1 V slope. <br />Again, the 1.25H:1 V are a `not to exceed limit' to extraction. The <br />evaluation from C.G.R.S. suggests the limit is reasonable. The limit <br />by force of reason suggests that lesser slopes will therefore be equal to <br />or better in terms of stability of the advancing wall when approaching <br />structures. We believe as a working limit of wall steepness, it <br />establishes an enforceable condition to assure the continued protection <br />of structures in proximity of the advancing wall. <br />d. If the Applicant chooses the flexibility to mine steeper than 1.25H:1 V, <br />a stability analysis of vertical pit walls must be provided. <br />The vertical wall limit of 1.25H:1 V will be honored over the entire <br />extraction area where an advancing wall exists. We may file a later <br />revision to the approved permit to allow steeper advancing walls with <br />adequate provision for buffers separation respective of any potential <br />failure relative to the approach of an advancing wall to surrounding <br />structures. <br />Varra Companies, Inc. correspondence of 1 September 2009 to the Colorado Office of Mined Land 13 <br />Reclamation (Office) in reply to Office correspondence of 27 July 2009 - Heintzelman Project - <br />M2009-018.