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STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Department of Natural Resources <br />1313 Sherman St., Room 215 <br />Denver, Colorado 80203 <br />Phone: 13071 866~J567 <br />FA%:13031 872-8106 <br />March 7, 1995 <br />Mr. Henry Barbs <br />Hountain Coal Company <br />P .O. Box 591 <br />Somerset, CO 81434 <br />I~~~~ <br />DEPARTMENT OF <br />NATURAL <br />RESOURCES <br />Roy Romer <br />Governor <br />lames S. lochhead <br />Executive Director <br />Michael B. Long <br />Division Director <br />RSS 6th Quarter 1996 Lower Refuse Pile Compaction Testing; Weat Blk Niae; <br />Permit Mo. C-80-007 <br />Dear Mr. Barbs; <br />The Division has reviewed Hountain coal Company's (MCC) relative compaction test <br />reaulte from the Lower Refuse Pile compaction testing dated December 27, 1994. <br />The results were submitted with the fourth quarter 1994 pond and stockpile <br />inspection reports. <br />The Division understands the column labeled Proctor Density PCF ie the maximum <br />dry density (MDD), in pounds per cubic foot (pcf), determined from a aeries of <br />testa (Proctor) run on a typical sample of material from the refuse pile. <br />According to MCC's result e, the MDD ie 68 pcf when the sample was compacted at <br />the optimum moiature content of 17 percent. Generally speaking, any compaction <br />done on material that deviates +59 from the optimum moiature content will not be <br />able to pate the standards established in the Rules. However, MCC's reaulte <br />indicate that material that is 15 percent drier that the optimum moiature content <br />has not only passed the required standards, but exceeds the maximum dry density <br />by 21 percent. It appears that the composition of the original gob sample that <br />was tested to determine the maximum dry density standard ie no longer a <br />representative sample. Therefore, the Division recommends that HCC perform a new <br />Proctor teat in accordance with ASHTO 99-74 standards on the refuse pile to <br />determine what the MDD ie for the material now being placed in the pile. MCC <br />should send the reaulte of the testa with the associated compaction curves as a <br />revision to be incorporated into the permit. <br />Preferably, this information should be provided to the Division prior to <br />performing the next compaction teat. However, since it ie near the end of the <br />first quarter and if MCC has already conducted the compaction testa, this <br />information should be provided prior to conducting the teats for second quarter. <br />Please call if you have any questions. <br />Y, <br />Christine ~. <br />Environmental <br />Specialist <br />LEJ/007COMP <br />