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<br />t A minimum setback from the edge of the pit to the high water <br />elevation of Foothills Reservoir must be maintained at 200 feet <br />' unless the applicant provides a more sophisticated stability analysis <br />including an analysis of seepage and pore water pressure to <br />demonstrate that a lesser setback would be stable. From the maps <br />provided, it does not appear that maintenance of a 200 foot setback <br /> from the reservoir will cause the Operator a hardship. <br /> • Maintenance ofa 3:1 mining setback from the water conveyance <br /> ditches on site will be adequate to protect the ditches from any <br />ti <br />t <br />bili <br />H <br />t <br />i <br />d <br />t <br />l i <br />d <br /> excava <br />on a <br />a <br />owever, <br />ewa <br />er <br />ng an <br />a <br />structura <br />ns <br />ty. <br /> horizontal distance three times the excavation depth from a flowing <br />a ditch may increase seepage loss from the ditch. The Rocky Mountain <br /> Consultants letter included in Exhibit G to the application discusses <br /> possible mitigation for increased seepage from ditches, but no <br /> concise mitigation plan is provided. <br />Q • Map Exhibit C- 1 shows a number of underground utilities without <br />u specifying the type of utility present. The applicant must specify if <br /> the buried utilities include any gas pipelines, sewer lines, or critical <br /> water supply pipelines as these types of utilities would require <br /> specific protection in addition to the proposed 3:1 setback. <br />' Typically, the Division would require installation and monitoring of <br /> strain gauges on pipelines prior to and during mining within 200 feet. <br /> Response: The Division is referred to Attachment #15, a memorandum dated <br /> October 29, 1999 from Allen Sorenson to Erica Crosby addressing man- <br /> made structures and mining setbacks. <br /> a. Western Mobile will locate all above ground and subsurface utilities <br /> on the site prior to the start of any mining or related construction <br /> activities such as conveyor installation across the Southdown <br />Q Entrance Road corridor. <br />b. Previously submitted Exhibit C-1 illustrates the location of above <br />~' ground utilities located within the cement plant access corridor. <br />c. WMI will provide the Division with copies of any agreements <br />necessary to install the conveyor to the Phase 1 mining area. <br />.,45. Comment: It is recommended that the applicant be dvected to provide a concise <br />mining setback and structural protection plan for this project. The plan <br />DMG Adequacy Review Response Page 19 <br />