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GENERAL47659
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Last modified
8/24/2016 8:22:55 PM
Creation date
11/23/2007 3:41:52 PM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1980007
IBM Index Class Name
General Documents
Doc Date
12/28/1981
Doc Name
Portals and entries, PAP review
From
J. Pendleton
To
TOM GILLIS
Permit Index Doc Type
STIPULATIONS
Media Type
D
Archive
No
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<br />STATE OFCOLORADO RICHP.gDD LR MM. Gov III IIIIII IIIIIII III <br />DEPARTMENT OF NATURAL. RESOURCES 999 <br />D. Monte Pascoe, Executive Director <br />MINED LAND RECLAMATION <br />423 Centennial Building, 1313 Sherman Street <br />Denver, Colorado 80203 Tel. (303) 866-3567 <br />David C. Shelton <br />Director <br />December 28, 1981 <br />TO: Tom Gillis <br />FROM: Jim Pendleton <br />RE: Review of A ed Section 3.5.2 of the Mt. Gunnison No. 1 Mine <br />Permit App ion, Submitted by ARCO Coal Company <br />Pursuant to your request, I have reviewed the amended "Portals and Entries" <br />section (Section 3.5.2) of the permit application for the Mt. Gunnison No. 1 <br />mine. I forward the following comments for your consideration. <br />ARCO Coal Company's amended Section 3.5.2, filed in conformance with State <br />Stipulation No. 9, Permit No. C-007-80, satisfies the geotechnical requirements <br />of that stipulation. The amended section presents two sealing schemes, one <br />for non-toxic drainage situations and another if toxic drainage is encountered <br />during the mining. The proposed non-toxic sealing technique consists of the <br />placement of a concrete block wall and earthen backfill at the portals with <br />the installation of 4 inch PVC drain pipes to allow drainage of effluent from <br />the mine after abandonment. The design scheme to be utilized if toxic drainage <br />conditions are encountered consists of a series of three sets of concrete seals <br />placed at intermediate points in the mine, as well as at the portal entries. <br />Calculations included within the amended submission demonstrate that factors <br />of safety in excess of 5 would result from the proposed designs. The analysis <br />contained therein assumes that a peizometric ground water surface similar to the <br />pre-mining case would reestablish following cessation of mining and the instal- <br />lation of the seals. Further, material strengths for the coal, floor rock and <br />roof rock are obtained by conversion from limited compressive strength data <br />obtained during ARCO's earlier drilling programs. ARCO commits to the collection <br />of additional geologic and hydrologic data as the mine is developed and to the <br />re-evaluation of the seal designs prior to installation and abandonment of the <br />mine, <br />I recommend that we accept and approve the amended permit application section <br />3.5.2, "Portals and Entries", submitted by ARCO Coal. 6Je should, however, <br />condition that approval upon the agreement of the operator to follow through <br />with its commitment to collect additional geologic and hydrologic data and to <br />re-evaluate the seal designs prior to construction, as presented on page 3-104 <br />of the amended permit application document. <br />I have forwarded the amended section 3.5.2 to Roy Cox for his evaluation of <br />the hydrogeologic aspects of that supplemental submission. <br />/mt <br />cc: Ed aischoff <br />Dave Shelton <br />
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