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. lage 9 0 <br />Tom Gillis <br />March 12, 1981 <br />CWI shouIcl include boring logs <br />of the mine site. The amended <br />specific geologg or hydrology <br /> <br />of all holes drilled during the investigation <br />application does not include any detailed site- <br />for the mine site. <br />3. The results of complete physical analysis of the bedrock, colluvium and <br />fil.i materials encountered. RocY. and soil mechanics parameter determinations, <br />including ultimate and residual shear strength (angle of internal friction <br />and cohesion), for both the effective stress and total stress conditions. <br />Mechanics testing should utilize testing techniques appropriate For the material <br />and hydrologic conditions existing at the site. Appropriate density/compaction <br />relations (Proctor analysis)should be determined for use in completing the <br />required stability analyses of the proposed cut and fill benches. If jointing <br />or fracturing is determined to be an important structural element, mechanical <br />testing should include determinations of the strength parameters of jointed <br />specimens. <br />The amended CWI application contains no discrete laboratory rock or soil <br />mechanics testing results. Shear strength parameters are developed by <br />correlation with penetration testing, which is extremely crude. Material <br />assumptions of this sort are inappropriate for a mine site with known <br />potential geological hazard problem . <br />9. A general plan and detailed engineering design for the proposed backfilled <br />final configuration, in accordance with Rule X1.27.3. Specific concerns <br />should be focused upon the drainage facilities of the proposed final reclaimed <br />configuration. Rule 9.27.3(7) .states that: "Unlined or unprotected drainage <br />channels shall not be constructed on backfills unless approved by the <br />Division as stable and not subject to erosion." The drainage scheme depicted <br />on map 38 within the amended application indicates a plunge pool which infringes <br />upon the fill bench on the "crushing and screening level", which could compromise <br />the stability of that fill bench if infiltration were to occur. <br />The permanent diversion ditch proposed at the upslope boundary of the Orchard <br />Valley mine surface facilities is a point of major concern. The occurence of. <br />landsliding on the upslope face of the ditch, evident during the short life <br />of the facility to date, could compromise the ditches function if landsliding <br />occurred following reclamation of the surface areas of the mine. Resulting <br />failure of tl~e diversion ditch could expose the entire reclaimed area of the <br />surface facilities to deleterious saturation. The application should demonstrate <br />the viability of the diversion ditch in light of this suspect upslope history <br />of Iandsl.i.de mass movement. <br />5. An appropriate state-of-the-art stability analysis of the proposed <br />final configuration of the Orchard Valley mine site. This mathematical <br />analysis should employ an appropriate'accurate'method of.static slope factor <br />of safety calculation, such as the SPENCER'S method, or a:~ equivalent <br />technique. The stability analysis must include bedrock, colluvium and fill <br />materials as possible critical failure surfaces. The analysis, in <br />order to be representative, must accurately model the proposed cut and fill <br />slopes of the final configuration. As such, it should include discrete materials <br />testing results determined for appropriate materials and degrees of ground water <br />saturation. In cases in which specific testing data is not available, sensitivity- <br />. i:~ i Y <br />