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.: . <br />Richartl D. Lamm <br />Governor <br /> <br />DEPARTMENT OF NATURAL RESOURCES <br />David H. Getches, E:eculive Director <br />MINED LAND RECLAMATION DIVISION <br />DAVID C. SHELTO N, Director <br />DATE: March 21, 1986 <br />T0: Dan Mathews \ <br />FROM: Jim Pendleton \ /"`""~Q`~ <br />RE: FOIDEL CRE K MINE - 85 <br />(PERMIT C- <br />ANNUAL SUBSIDENCE SURVEY REPORT <br />~II ~I~I~~~I~~~~~ ~I~ <br />I have completed the review of Twentymile Coal Company's 1985 annual <br />subsidence survey report for the Foidel Creek Mine, certified by Michael <br />Joseph Astuto, Colorado Registered Land Surveyor No. 13821. This report <br />presents a clear and concise summary of the past year's mechanical subsidence <br />and slopes stability monitoring results for the Foidel Creek Mine. <br />Hydrological information will be summarized separately within the operator's <br />annual hydrology report. It is important that this hydrology report presents <br />a clear summary of the hydrologic impact of subsidence. Please refer it to <br />my attention upon its receipt. <br />To date only development of the main entries and the "first panel south" <br />subentries have been accomplished at the Foidel Creek Mine. No caving of the <br />overburden has been stimulated and no subsidence of the surface has been <br />detected by the monitoring program, as projected within the permit <br />application. The company has installed appropriate monuments with which to <br />monitor possible subsidence due to the mining occurring at this time and <br />projected it to occur within the next six months. The company has also <br />surveyed the appropriate structures, including two hurried water tanks, the <br />CYCC office building, a gasoline storage tank, and 13 electric power poles. <br />The data presented depict at least two surveys of all existing monuments and <br />structures. In the case of monuments SM-32 through SM-41, and for each of the <br />structures, two surveys were performed on subsequent days. Nontheless all <br />surveys closed within + 0.1 foot, which is acceptable accuracy. Further, the <br />survey data suggests tFiat all monuments have been stable to date, showing no <br />evidence of freeze/thaw or other distorting effects. <br />The only monuments showing significant movement are those within the slope <br />stability monumentatiort set placed at the toe of the fi17 slope immediately <br />south of the Foidel Creek Mine portals. Monument SP-1 underwent -0.4 feet of <br />movement prior to its removal in September 1984. Monument SP-2 has undergone <br />-0.9 feet of movement to date. I assume that these monuments reflect <br />consolidation effects due to the adjacent backfill spoil. However, I believe <br />it appropriate for the operator to conduct a brief surface reconnaissance of <br />the spoil area adjacent to monument SP-2, in order to ascertain whether any <br />evidence exists to suggest any differential movement which might be occurring <br />in the spoil. <br />423 Centennial Building, 1313 Sherman Street Denver, Colorado 80203 Tel. (303) 866-3567 <br />