Laserfiche WebLink
~~ 96 South Zuni Street <br />Denver, Colorado 80223-1292 <br />i E C H N O L O G I F 5 I N C Telephone: 1303) 744-71 O6 <br />• July 10, 1996 Feceimia: 13031 744-0210 <br />L Morrison Knudsen Corporation <br />7100 East Belleview Avenue, Suite 300 <br />Englewood, Colorado 80111 <br />L: <br />Attention: Mr. Peter A. Stauch, P.E. <br />L Subject: Preliminary Geotechnical Engineering Study for the Bowie No. 2 Mine Surface <br />Facilities, Bowie, Delta County, Colorado <br />L Job No. 5002-60-2655.01 <br />Dear Mr. Stauch: <br />At your request, we have conducted a geotechnical engineering study to evaluate the general soil <br />[ and subsurface conditions at the proposed Bowie No. 2 Mine surface facilities. We understand <br />that the subject mine will have at least a 35-year life. The project site is located in Sections 10 <br />(SW1/4) and IS (Nl/2), Township 13 South. Range 91 West of the 6th Principal Meridian, <br />Delta County, Colorado. The study was prepared in accordance with our proposal, dated May <br />' 21, 1996. This letter provides a summary of our findings, which are detailed in the attached <br />report. <br />l • Most of the surface facilities for the mine will be situated on an ancient landslide within steep <br />i terrain formed by horizontally interbedded sandstone and shale of the Mesaverde Formation and <br />underlying Mancos Shale. The ancient landslide mass appears to be globally stable with respect <br />to slope movement potential, while the surrounding slopes exposing rock at outcrop are much <br />less stable, as evidenced by recent slope ntovelnents adjacent to the mine site. <br />Subsurface conditions encountered in the 23 exploratory borings at the site vary with location <br />and depth, with the strata typically consisting of a very thick layer of very stiff to hard, slightly <br />moist, lean clay with gravel and scattered to numerous small to large rock fragments (CL-GC), <br />overlying shale or interbedded sandstone and shale or coal at depths exceeding 70 feet. Ground <br />water was encountered in only three borings, at depths of 20 to 48 feet. The presence of <br />cobbles and boulders of sandstone and shale in the clay serves to increase strength of the soil <br />mass. Because the soil is predominantly clay, it is the limiting material for strength <br />considerations. The clay generally has high strength in its present partially saturated state. <br />However, the clay is sensitive to loss of strength and/or swelling upon moisture increase. <br />I~ <br />L• <br />Astern • Austin Research Engineers •Chen-Northern • Empire Soils Investigations • Kansas City Testing <br />Maxim Engineers • Nebraska Tasting • Palzig Testing • Southwestern Laboratories • Thomas-Hartig • Twin City Testing <br />