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Memo to Tom Schreiner 4 April 23, 1999 pipeline steel specified minimum yield strength. If the pipeline operator refuses to cooperate in the installation and monitoring of strain gauges, then the applicant could put together a proposal to monitor the pipeline easement through the use of inclinometers, extensometers, or similar devices, or could commit to a 200-foot minimum mining setback from the pipeline. 5. General Issues Relative to Minine Setbacks at the Proposed Pit The applicant should provide the following information relative to their proposal to mine within 200 feet of manmade structures. The construction materials statute provides that permit applicants and mine operators may mine within 200 feet of manmade structures if it is demonstrated that [he structures will not be damaged and if a compensation agreement cannot be reached with the owner of the structure. The applicant should state affirmatively that all efforts to secure compensation agreements have failed, as these agreements are preferred under the statute at C.R.S. 34-32.5-115(4)(f) to engineering demonstrations of stability. The justification or rationale for using a 30-foot depth to bedrock in the stability analyses provided. The applicant should provide core hole information or other information that forms the basis for this analytical assumption. To increase slope stability, the applicant has committed to mining temporary cut slopes at an angle no steeper than O.SH: l V. Typically, gravel pits aze mined by excavation at the toe of a gravel bank, whereby the bank collapses progressively into the pit, usually at a near vertical slope. It has been the Division's direct experience that efforts to maintain the mined face at a less than vertical slope are rarely successful unless the operator mines the gravel by pushing material down the bank using a bulldozer, in which case safety considerations require that slopes no steeper than 2.5:1 or 3:1 be developed. For this reason, the applicant must describe in terms of the mechanics of earth moving the procedures to be used to mine at a O.SH:1 V slope. It must be emphasized to the applicant that if less than vertical mine slopes are to be relied upon to enhance slope stability and protect manmade structures within 200 feet of the mined face, the Division would consider mining of the slopes at an angle steeper than specified in the permit a serious violation for which an enforcement action would be immediately implemented. The applicant should provide a detailed discussion of the measures to be employed to field mark any setbacks that aze approved in the reclamation permit. It is stated in the application that subsurface utilities will be located and staked prior to mining to assure that setbacks will be maintained. The Division suggests that the location of the setback boundary also be cleazly marked in the field [o better assure that inadvertent transgressions into the setback areas do not occur. attachment(s) c:\wi ndows\personal\camas.doc