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•~ <br />energy fuels corporation <br />box g .steamboat springs, Colorado E10477 . (3031 679-3800 <br />Mr. Robert Liddle <br />Reclamation Specialist <br />Colorado Mined Land <br />Reclamation Division <br />423 Centennial Building <br />1313 Sherman Street <br />Denver, CO 80203 <br />Dear Bob: <br />i <br />~ ~ _ . III IIIIIIIIIIIII III <br />RECEIVED <br />QEC 151980 ~ <br />MINED LAND RECLAMATION:C <br />COLD, DEAL OE IUTURAI RESOURCES <br />December 8, 1980 <br />Pursuant to your .recent letter of November 26, 1980, Gary Myers and <br />myself inspected Bond Release Area D at Mine Ik3 to examine the area of <br />ground cracks you observed on your inspection of the area on November 19, <br />1980. As you will recall during the field inspection, it was my opinion <br />that the ground cracks corresponded to the area of the old highwall at <br />this site. We have examined the old pit maps, premine and postmining <br />topographic contours of this site and have placed them on the enclosed <br />cross-section of the area we inspected. The location of the cross-section <br />we have prepared is delineated on the enclosed Mine 113 Bond Release Map. <br />As you will see from the attached memorandum from Gary Myers, the <br />reasons for the ground cracks are obvious. The cause of the ground cracks <br />is due to the subsidence of the backfilled overburden. As you are aware, <br />blasting and mining operations increase the volume of overburden materials <br />on the order of approximately 25 percent. Over time these recontoured <br />spoil materials settle and the elevation of the site is lowered. The <br />instance of subsidence on strip mined lands has been well documented. In <br />the Symposium - Adequate Reclamation of Mined Lands?, held in Billings, <br />Montana, two papers were presented on this subject. Groenewold and <br />Halvorson presented papers wherein they reported that the area-wide <br />settlement of recontoured spoils has been on the order of 1.5 to 3 feet. <br />Settling was found to be as high on scraper compacted spoils as it was for <br />end dumped spoils. <br />Comparing these subsidence amounts of the surface mines in the Great <br />Plains with those apparent in the ground cracks at Mine 1l3 reveals many <br />similarities. The only difference between them are that ground cracks <br />have appeared along the old highwall at Mine 113 whereas the area-wide <br />settling usually produces a uniform settling of the recontoured spoil. <br />Since the depth of overburden along the Mine 1l3 highwall was approximately <br />100 feet and [he depth of spoil dumped above the highwall is Less than 20 <br />