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iii iiiiiiiiniiiiu <br />STATE OF COLvx~iw <br />MINED LAND RECLAMATION DIVISION <br />OF, Grp <br />Department of Natural Resources a~','~y <br />„Q%%Fer~dl3Y\~ o <br />1313 Sherman St., Room 215 ~, <br />Denver. CO 80203 • ~C'~ ~~J.~> <br />303 866-3567 "ia ~s• <br />Rnx: 303 8328106 <br />Roy Ramer, <br />Governor <br />DATE: April 5, 1991 Fretl R. Banta, <br />Division Director <br />T0: Anthony Wal dron \ <br />_- l~ , <br />FROM: Jim Pendleton <br />RE: The Eagle o. 6 e's Subsidence Report - February, 1991 <br />(Permit No. C-81-044) <br />I have the reviewed the Cyprus Empire Eagle No. 6's Subsidence Monitoring <br />Report, dated February 23, 1991. This report reflects subsidence monitoring <br />data collected as of December, 1990. Consistent with subsidence monitoring <br />conducted at the Eagle No. 6 for the past decade, this report is clear, <br />concise and complete. <br />Very briefly summarized, the subsidence monument survey data verifys that <br />subsidence due to the E-seam mining beneath the earlier extraction conducted <br />in the F-seam, is occurring as predicted. Beneath subsidence monument #S-5, <br />located approximately mid-line in the First East panel, approximately 3.6' of <br />subsidence had occurred as of March, 1988. This subsidence was a result of <br />overlying F-seam extraction. As of November of 1990, 12.327' of subsidence <br />had occurred at that same monument. Therefore, 8.7ti' of additional subsidence <br />had occurred since E-seam extraction commenced. Some of this subsidence may <br />be due to additional subsidence of F-seam gobbed underground mine workings, in <br />addition to new subsidence of the recently extracted E-seam workings. <br />Monitoring point #S-5 has experienced the maximum combined ground level <br />subsidence observed at the Eagle No. 6 mine to date. <br />I recommend that you accept the subsidence report as submitted. It fulfills <br />the requirements of their semi-data submittal. It will be important to assure <br />that they include detailed descriptions of observed surface phenomena <br />accompanying the measured E-seam subsidence when submitting their more <br />detailed annual subsidence report. Documentation of these surface expressions <br />of subsidence will be particularly important when considering future requests <br />by the operator to mine beneath protected structures or renewable resource <br />areas. <br />You recently commented that Terrell Johnson, on the staff of Cyprus Empire <br />Energy, had requested an indication of what requirements the Division would <br />place upon the company's commencement of extraction beneath protected <br />structures or renewable resource areas, such as Highway 13. Before we can <br />approve development or retreat extraction beneath any structures or renewable <br />resource lands, the operator will have to present their projection of the <br />anticipated consequences of that proposed extraction. Their subsidence <br />monitoring data shoulo provide verification of their projections. Formally <br />