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~~ <br />Water, Waste & Land, Inc. <br />CONSULTING ENGINEERS & SCIENTISTS <br /> <br />January 20, 1982 <br />MINING UEp ME <br />•` ~ <br />CF&I Steel Corporation <br />P. O. Box 316 <br />Pueblo, CO 81002 <br />Attn: Mining Department <br />Mr. Jack D. Gillespie <br />Gentlemen: <br />.//~il N 1~ ,'1, 1 <br />.. ~+_ <br />Re: Stability Analysis <br />Mine Waste Piles <br />Allen and Maxwell Mines <br />WWL N8105 <br />In response to your purchase order No. M12180, dated 12/04/81, we have <br />conducted a study on the proposed coal mine waste piles at your Allen <br />and Maxwell Mines near Weston, Colorado. This work has included laboratory <br />identification and shear strength testing of waste material, and a <br />stability analysis of the piles to evaluate their anticipated behavior. <br />The purpose of this report is to summarize the laboratory testing data <br />and present the results from the stability studies. <br />Laboratorv Testi <br />Laboratory identification and shear strength tests were performed on a <br />sample of coal mine spoils as provided by CF&I. As we understand it, <br />this sample was obtained from the existing piles at the Allen Mine. The <br />result of the identification testing is shown on Figure 1. Included in <br />this testing was specific gravity of the solids, grain size distribution <br />of the granular portion and Atterberg Limits of the fines. By the Unified <br />system, the spoil classifies as an SW-SC soil which is a well graded sand <br />to clayey sand with some organics. The spoil is considered to be "soil- <br />like granular" by OSM "Guidance Document for the Disposal of Excess Spoil" <br />(in press). The results of a moisture-density test conducted on the <br />portion of spoil finer than the No. 4 sieve is presented on Figure 2. <br />The maximum dry density of the minus 4 material is about 93.2 pounds per <br />cubic foot at an optimum water content of 12.9%. When corrected for the <br />percent of coarse material, the maximum dry and wet density of the entire <br />sample is about 98.3 and 108.1 pounds per cubic foot. <br />The results of direct shear testing is presented on Figure 3. This test <br />• was conducted according to ASTM 0-3080, "Standard Method for Direct Shear <br />Test of Soils Under Consolidated Drained Conditions" using minus No. 4 <br />sieve size materials. The results indicate that the spoil is cohesionless <br />I <br />