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`ntb~rf ~n~ ~ss~~ittf~s <br />CONSULTING GEOTECHNICAL ENGINEERS AND MATERIAL TESTING <br />Bowie Resources <br />P.O. Box 483 <br />Paonia, Colorado 81428 <br />Attention: Mr. William Bear, Jr. <br />Subject: Coal Mine Refuse (GOB) pile <br />Bowie Number 2 Mine near <br />Paonia, Colorado <br />Mr. Bear: <br />July 30, 1999 <br />PN: M99012GE <br />This letter is intended as a supplement to our letter dated May <br />26, 1999 presenting our geotechnical engineering analysis of the <br />slope stability of the GOB pile. This letter is in response to a <br />request by Mr. Jim Stover to provide additional slope stability <br />analysis to include a layer about one (1) to two (2) feet thick of <br />spoil material from the ventilation shaft. The material is at the <br />existing surface of the GOB pile. <br />We understand that the existing surface is at an elevation about <br />fifty (50) feet above the elevation of the GOB pile slope toe. Our <br />additional slope stability analysis included an assumed layer of <br />ventilation shaft material two (2) feet thick at the existing GOB <br />pile surface elevation and assumed completed conditions of the GOB <br />pile. <br />We obtained a sample of the ventilation shaft spoil from a <br />stockpile which had been previously placed on the surface of the <br />GOB pile. We performed a standard moisture content-dry density <br />relationship (Proctor) test, ASTM D698, for the material sampled <br />and performed a staged triaxial compression test of a sample <br />remolded to about ninety (90) percent of the maximum dry density as <br />defined by ASTM D698. <br />The strength values for the ventilation shaft spoil material used <br />in our stability analysis were an internal angle of friction of 12 <br />degrees, a cohesion of 300 pounds per square foot and a moist soil <br />unit weight of 110 pounds per cubic foot. All other strength <br />values presented in our May 26, 1999 letter were used for the <br />surrounding GOB material. All other assumed conditions of the <br />completed GOB pile as identified in our May 26 letter were included <br />in the assumptions for our additional slope stability analysis. <br />P. O. BO% 3986 P. O. BOX 0045 214 BODO DR. <br />GRAND JUNCTION, CO 81502 MONTROSE, CO 81402 DURANGO, CO 81701 <br />(970) 2466606 (970) 24F2154 (970) 259-5095 <br />FA%: (970) 209.9759 FA%: (970) 249-3262 FA%: (970) 782.2515 <br />