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Memo to Erica Crosby 2 July 8.2002 <br />The primary reason for the high degree of slope stability at this pit, and the ability to safely employ minimal <br />setback distances, is a result of the implied commitment in the Ground report that the pit Operator will <br />excavate the back cut to a slope no steeper than 1.SH:1 V. Whenever an Applicant proposes to excavate at a <br />prescribed slope angle, it is imperative that the DMG emphasize that the result of the proposal will be to <br />limit the pit Operator's flexibility in the progression of the excavation. Since the stability of valuable offsite <br />structures depend on maintenance of the 1.SH:1V working pit slope, this sloping would be an enforceable <br />condition of the mined land reclamation permit. The DMG would view any transgression of the sloping <br />requirement, i.e. any slopes steeper than 1.SH:1 V located within 200 feet of any offsite structure, to be a very <br />serious violation to the terms of the permit and to the Colorado Land Reclamation Act for the Extraction of <br />Construction Materials. Given the importance of the sloping requirement to the protection of offsite <br />structures, the DMG has the following suggestions: <br />The Applicant should describe, in terms of the mechanics of earth moving, how the pit Operator will <br />maintain the 1.SH:1 V working slopes over slope heights of between 40 and 50 feet. Typically, a pit is <br />excavated from the toe of the slope and the pit walls progressively cave into the pit leaving near vertical <br />pit walls at the working face. At a small percentage of gravel pits, the Operator will work from the top of <br />the bank and push material down into the pit floor; using this mining method shallow angles at the <br />working face are easily maintained. However, slopes steeper than 2H:1 V are not safe for the operation of <br />equipment. The preceding discussion leads to the DMG's inquiry as to how the pit Operator will work <br />with I.SH:1 V slopes as required to be in compliance. <br />To increase the pit Operator's flexibility in the methods employed to complete the excavation, the <br />Applicant may want to consider an alternate method for establishing and measuring the setbacks required <br />for the protection of offsite structures. The following diagram illustrates this possibility and also shows <br />the relationship between the easement line and the Fulton Ditch location as discussed above. <br />