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<br />STATE OF ~II II~~I~~I~~~~~ ~I~
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<br />DIVISION OF MINERALS AND GEOLOGY ' '-
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<br /> DEPARTMENT OF
<br /> NATURAL
<br />DATE: February 20, 1997 RESOURCE
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<br />Susan Burgmaier ~ h„
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<br />FROM: Jim Pendleton
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<br />RE: "Review of xis ~ g Compaction Data and Testing
<br />Frequency for the Existing Refuse Pile, Southfield Mine -
<br />Florence, Colorado" by TerraMatrix, Inc.
<br />(Permit No: C-81-014)
<br />In accordance with your request I have completed a review of the above
<br />referenced report prepared for the Southfield Mine by TerraMatrix, Inc., a
<br />geotechnical consultant. The Division recently directed the mine to address the
<br />possibly substandard compaction results submitted for the coal refuse pile at
<br />the Southfield Mine. In preparing my review I have also revisited a similar
<br />reanalysis of the Southfield Mine coal refuse pile prepared in 1992 by ACZ, Inc.,
<br />a former geotechnical consultant to the operator.
<br />The Situation at the Southfield Mine Coal Refuse Pile
<br />The permit, as amended in 1992, specifies that coal refuse will be placed and
<br />compacted in two foot lifts. A thin lift of fine coal refuse was to be placed and
<br />then covered with coarse refuse to a combined thickness of two feet. The
<br />combined material was then to be compacted to 90% relative density.
<br />TerraMatrix reports; "However, based on TerraMatrix's observations actual
<br />placement practices have been slightly different. Fines are generally being
<br />placed in one-foot lifts followed by a two to four foot lift of coarse refuse. The
<br />fine lifts were not compacted. However, the coarse lifts were compacted by a
<br />dozer with a pull behind sheeps-foot compactor. Additional compaction was
<br />provided from truck traffic."
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