GENERAL50842

• Permit No: C1981016
• IBM Index Class Name: General Documents
• Doc Date: 3/2/1981
• Doc Name: SUBSIDENCE ASPECTS OF HAWKS NEST MINE
• From: MLR
• To: CAROL RUSSELL
• Permit Index Doc Type: GENERAL CORRESPONDENCE
• Media Type: D
• Archive: No

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OEPARiMEN7 OF NATI)q AL flES~I 11nm~ n. i nen,n ~..~v,~„~.,,
D. Monte Pascoe, Executive DirectorU LACES III IIIIII'llllll
999
MINI':I) I,ANI1 IiI~,1:I.AMA'I'11)N
423 Centennial Building, 1313 Sherman Street
Denver. Colorado 80203 Tel. [phone]
David C. Shelton
Director
March 2, 1981
T0: Carol Russell ~ `c~~
FROM: Jim Pendleton -~
SUBJECT: `Subsidence ects Hawks Nest Mine
In anticipation of the completion of your Phase I review of lJestern Slope
Carbon's permanent permit application for the Hawks Nest Mine, I forward the
following comments concerning the subsidence aspects of that permit application.
~,(1) Western Slope Carbon states that all structures lie outside the area of
potential subsidence effect (outside the area defined by projecting '.:ie boundary
of the mined area to the surface along the projected angle of draw) and that
no renewable resource lands exist within the permit or adjacent areas.
To support the first contention WSC refers the reader to Exhibit 2.05.6-C.
Through some oversighton their part this Exhibit does not delineate the subsidence'
boundary mentioned. This oversight must be rectified. However, State highway
133 does constitute a structure and is proposed to be undermined by the east
portals.
In order to support their second contention Roy Cox and yourself will need to
corroborateWSC's contention that no renewable resource lands (including aquifers
and areas of recharged to aquifers) exist within the permit or adjacent areas.
(2) ,The subsidence monitoring program proposed within the application will have
~to be amended to, include the monuments shown on Figure 4.20.1-A paralleiling
State highway 133. In addition the application references the possible installation
of survey monuments above the longwall portions of the mine. Such monuments
should be installed and included on a plan.
t (3) WSC must describe the installation of its survey monuments to be used for
subsidence observation. These monuments must be permanent and capable of resisting
damage by normal traffic or climatic extremes.
(4) :Past generations of WSC's subsidence control plan for the Hawks Nest Mine
included steel arched supports within the portals driven beneath highway 133 at
the east mine portal. Reference is now made to steel arch support in the existing
portal within the control plan on page 4.02-4 of the permanent permit application.
However, the application does not propose to install steel arch support in the
additional proposed entries to be driven beneath that highway.