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i • <br />STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Dcponmi•m ul Ndnrtal Resources <br />1313 Sherman SI., Room 215 <br />Denver, Colorado 80203 DIVISION O F <br />Phone: 0031 e65-3567 MINERAL S <br />rAx ulr11e32-elan & <br /> GEOLOGY <br /> 0.EC LAM ATION <br /> MINING•SAFEiY <br />DATE: March 8, 2000 <br /> Bil I Owens <br />TO: Carl Mount Governor <br /> Greg E. Walther <br /> <br />' ~ Eeecmrve Dvecbr <br />FROM: Allen Sorenson ~ Michael 8. Long <br /> Divivon Drtector <br />RE: Geotechnical Addendum for 1998 Annual Repo rt, Camas Colorado, Inc., <br />Morrison Quarry, Permit No M-73-021 <br />I have completed a review of the above referenced report. The following is a summary of the pertinent <br />information contained therein. <br />Bench 1 and Bench 2 were completed on the east side of the Central Quarry in 1998. The measured <br />foliation dip in these benches generally strikes sub-perpendicular/perpendiculaz to the slope in these <br />final benches. This is a favorable orientation for slope stability. The survey points established in <br />the azea of the 1996 slope failure on Benches 6 and 7 showed little movement indicating that the <br />repaired slopes are currently stable. <br />2. Observations in the south end of the Central Quarry indicate that the primary joint set dips into the <br />slope, which is advantageous for stability. However, secondary jointing frequently dips out of the <br />slope, so the Operator is developing quarry benches at an overall inclination of approximately <br />1H: l V or flatter as approved in the permit. <br />3. Adverse daylighting joints have also been observed in the north quarry. As a result, the Operator is <br />developing the benches and highwalls to an overall l H:1 V slope and is quarrying from east to west <br />so that the joints will not dip out of the working face. <br />Based on the information contained in the Geotechnical Addendum, the Operator is conducting quarry <br />operations in accordance with the permit conditions imposed to assure the development of stable <br />benches and highwalls. In many cases, the Operator is developing 40 foot highwalls with 40 foot <br />benches, which is more conservative with regard to stability than the bench/highwall configurations <br />approved in the permit. I would recommend that the Morrison Quarry be scheduled for inspection this <br />summer to observe the current condition of the quarry perimeters. <br />c:\windows\personal\morrison geotech.doc <br />