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ATTACHMENT 6. <br /> Geotechnical Stability Exhibit <br /> Prepared 23 August 2016 by Nathan A. Barton, CE, PE, DEE <br /> Purpose: To provide geotechnical and engineering evaluation and analysis of the situation of <br /> the J&J Pit in 2016, and detail specific measures of mitigation and prevention to ensure the <br /> geotechnical stability of the J&J Pit during continued mining and reclamation, supporting <br /> revised Exhibits C, D and L. <br /> Scope: This exhibit applies only to activities after its date of approval by DRMS. <br /> Summary of Findings and Recommendations: <br /> 9) The proposed slopes, highwalls, and other terrain features are geotechnically stable <br /> and present no significant potential to adversely affect any structures or facilities on- or <br /> off-site, provided that recommended actions are taken as identified in this report. <br /> 10)This finding is based on the assumption that soil and deposit conditions already <br /> revealed by extraction of construction materials will continue to be present in the <br /> remainder of the extraction to be done as proposed in Exhibit B. <br /> 11)Modification of any part of the proposed mining and reclamation, and the discovery <br /> of any significant deviation from known conditions, as mining and reclamation <br /> proceed, will require additional engineering evaluation at that time. <br /> 12) Recommended actions: Summary: See Section X below for detailed discussion. <br /> 1) Mine and reclaim by lots (block). <br /> 2) During active mining, establish setbacks, maximum heights and minimum widths <br /> for benches (in accordance with engineering and MSHA standards), inspect <br /> frequently, and immediately address any problems noted. <br /> 3) During reclamation (to be done by block), continue to inspect and address <br /> problems noted. Reclaim to 1:1 unless engineered retaining walls or related <br /> methods are used. Buttress highwalls using selected and compacted backfill, <br /> and vegetate as described in Reclamation Plan. <br /> As stated in Rules Section 6.5: (underlines added), this exhibit shall address: <br /> 14)On a site-specific basis, an Applicant shall be required to provide a geotechnical <br /> evaluation of all _geologic hazards that have the potential to affect any proposed <br /> impoundment, slope, embankment, highwall, or waste pile within the affected area. <br /> The Applicant may also be required to provide a geotechnical evaluation of all <br /> geologic hazards, within or in the vicinity of the affected lands, that may be de- <br /> stabilized or exacerbated by mining or reclamation activities. <br /> 15)On a site-specific basis, an Applicant shall be required to provide engineering stability <br /> analyses for proposed final reclaimed slopes, highwalls, waste piles and embankments. <br /> An Applicant may also be required to provide engineering stability analyses for certain <br /> slopes configuration as they will occur during operations, including, but not limited to <br /> embankments. Information for slope stability analyses may include, but would not be <br /> limited to, slope angles and configurations, compaction and density, physical <br /> characteristics of earthen materials, pore pressure information, slope height, post- <br /> placement use of site, and information on structures or facilities that could be <br /> adversely affected by slope failure. <br /> Technical Revision to M1985-001 J&J Pit, LaPlata County, dated 24 AUG 2016 Page 23 <br />