1992-07-22_GENERAL DOCUMENTS - C1981017

• Permit No: C1981017
• IBM Index Class Name: GENERAL DOCUMENTS
• Doc Date: 7/22/1992
• Doc Name: Bid Documents ‎(IMP)‎ Proposed Decision & Findings
• Media Type: D
• Archive: No

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Pursuant to Rules 2.07.6(2)(j) and 3.02.1(1) , a performance bond in this
amount has been filed with the Division, payable to the State of Colorado and
the United States of America prior to permit issuance.
The proposed operation is in compliance with the requirements of this section.
XXI. Sealing Drilled Holes and Underground Openings - Rules 2.05.4(2)(g)
and 4.07
Mid-Continent Resources, Inc. proposes to seal mine portal openings in
accordance with MSHA regulations (30 CFR 75.1711-1) and to seal all bore holes
and wells with concrete plugs or welded locked steel caps, in the case of
monitoring facilities. The Division finds that these proposed techniques are
in compliance with the requirements of Rules 2.05.4(2)(g) and 4.07.
XXII. Subsidence - Rules 2.05.6(6) and 4.20
The applicant determined that "the only structures above underground workings,
or within areas of possible surface subsidence, are those related to the
mining operations such as exploration and light use roads and ventilation
fans" (page IV-E-23) . Potentially affected renewable resource lands include
only limited grazing lands, since the major local aquifers lie beneath the
coal seams being mined. In addition Mid-Continent Resources, Inc. presents a
thorough discussion or worst possible consequences due to subsidence,
including predictions of projected subsidence magnitude. The company predicts
a maximum vertical subsidence of 13.2 feet in areas overlying the extraction
of 24 feet of coal (9 feet to be extracted from one seam and 16 feet to be
extracted from the other) . Based upon limited observed data within the
western United States, the applicant also projects an angle of draw of 150.
The Division does not consider this angle of draw average projection to be
adequately justified. Observations of angle of draw at the nearby Somerset
Mine suggests that an angle of draw of 20.50 would be more appropriate, in
the opinion of the Division.
Finally, the company has installed an extensive system of subsidence
monitoring monuments with which it proposes to verify its projections of
subsidence occurrence. The program is designed to provide the following data:
- Maximum subsidence resulting from mining
- Horizontal movement of the ground surface resulting from mining
- Subsidence development profiles
- Subsidence profiles resulting from mining
- Strain profiles resulting from mining
- Determination of the angle of draw
- The effects of depth and mining geometry on subsidence.
The Division concurs with this opinion and with the company's observation
that: "The proposed monitoring program will result in the development of
site-specific subsidence projection models for the Coal Basin area" (page
IV-E-34) .