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GENERAL48106
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Last modified
8/24/2016 8:23:57 PM
Creation date
11/23/2007 4:06:41 PM
Metadata
Fields
Template:
DRMS Permit Index
Permit No
C1981038
IBM Index Class Name
General Documents
Doc Date
7/30/1993
Doc Name
PROPOSED DECISION & FINDINGS OF COMPLIANCE FOR PR3
Permit Index Doc Type
FINDINGS
Media Type
D
Archive
No
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The operator, in conformance with recommendations made by its <br />geotechnical consultants, has installed sophisticated tilt-metering <br />devices within several of the fill benches which exist within the <br />surface facilities at the Orchard Valley Mine. The purpose of these <br />devices is to collect additional geotechnical data with which to <br />verify past analytical assumptions and with which to complete final <br />analysis and design, originally stipulated as Phase III of the surface <br />facility studies, within the approved original permit. <br />Utilizing the results of Geo-Hydro, Consultants, Int.'s analyses, <br />Merrick & Company, Inc., design consultant to the operator, completed <br />a Phase II amended design for the drainage facilities at the existing <br />surface facility area of the Orchard Valley Mine. The operator also <br />completed a detailed stability analysis and redesign of the proposed <br />final reclaimed configuration for the surface facilities at the mine. <br />In order to ensure stability and control erosion on final graded <br />slopes, the Division has approved a post-mining topography of cut-and- <br />fill terraces at the main mine. These terraces are compatible with <br />the post-mining land use of grazing and meet all the requirements of <br />4.14.2(2) with the exception of 4.14.2(2)(a). Terraces will all <br />exceed 20 feet in width and range in width according to the reclaimed <br />configuration map series 6A-5. <br />In August 1986, the operator submitted a permit revision application <br />to construct a west portal facility in the East Roatcap Creek valley <br />at the Orchard Valley Mine. This application proposed the <br />construction of a new portal facility and haul road, because the <br />existing portals at the Orchard Valley Mine had been rendered <br />unuseable by an underground coal mine fire. The applicant proposed to <br />upgrade an existing public access road to serve as a coal haul road to <br />the proposed west portal bench, which wilt be constructed by a <br />balanced cut-and-fill method. The portal bench fill includes a <br />130-foot maximum height terraced earthen fill constructed across East <br />Roatcap Creek. Maximum interterrace facial slopes shall not exceed a <br />2.5h:l.Ov (horizontal to vertical) slope gradient. A 48-inch concrete <br />culvert was installed beneath the cross valley fill to accommodate the <br />100-year flow of the East Roatcap Creek. <br />The permit revision application included geotechnical specifications <br />documented in the OVWM Appendix, Volume 6, prepared by Golder and <br />Associates, consultants to the operator. This appendix presents the <br />results of geotechnical investigations, stability analyses and <br />detailed engineering designs for the west portal bench cut and fill <br />and the accompanying upgraded haul road. The stability analyses are <br />based upon projected slope configurations and material mechanical <br />properties obtained from material sampling and laboratory analyses. <br />Stability analyses were completed for both the operational and <br />reclaimed configurations of the west portal facility area. Curing <br />final reclamation of the OVWM, the fill will be removed. The portal <br />cut will be backfilled with this fill and a slope ranging from 2.5:1 <br />to I.5:1 (v:h) will be established. This slope will approximately <br />achieve the post-mine configuration. <br />-35- <br />
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