LACK OF RETREAT MINING AND SURFACE EFFECTS IN INDIANA

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(LACK OF) RETREAT MINING AND SURFACE EFFECTS IN
INDIANA
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Outline

• Various Secondary Mining Methods
• Examples of Surface Effects
• Indiana Regulations
• Requirements for successful second mining

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Longwall Mining

• Hand longwalls in IL in 1857
• Modern method introduced in U.S. in 1960s
• Represents 50 of u/g production today
• Four active faces in IL today, none in W. KY

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Bigger-the-Better! (Barczak)

• Mid 80s - 700-800 ton shields common
• 1989 - Galatia installs 900 ton, 4-legged
  shields, claims ours are the biggest
• Mid 90s - shields evolve to 980 tons
• By 2001 - 1,170 ton shields in use
• Today - Peabodys Twentymile has max. shield cap
  of 1,300 tons

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Full-Pillar Extraction

• 1960s, 70s 80s Old Ben Coal, Inland
  Steel Freeman United conducted high extraction
  retreat RP mining
• Harco Mine experience leads AOI Kathleen Mine to
  attempt first pillar panel in 1991.

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Supplemental Support

• Timbers are traditional, Kathleen Conant used
  6-inch oak roundposts
• Limited to 50 ton bearing cap.
• Limited convergence range (1-2 in.)
• Material handling problems

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Mobile Roof Supports

• 1st set of Alpine supports in WV, 1988
• This set purchased from Donaldson Mine for
  Kathleen Mine in 1993.
• Fletcher dominates market w/ 300 units
• Voest-Alpine basically retreated from North
  America

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MRS Advantage

• Remote operation
• Excellent support capacity (600-800t)
• Maintain load, even w/ 1ft convergence
• Eliminate most material handling
• Typically offer a speed advantage over timbers
  moving lift-to-lift

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Who is pulling pillars?

• Kevin Stricklin, Admin. For Coal Mine Safety and
  Health before the Senate Comm. On Health,
  Education, Labor, and Pensions on Oct. 2nd -
• Retreat mining is a common practice nationwide
  where coal is mined from coal pillars. When this
  coal is mined, the roof normally falls in a
  structured manner to relieve the pressure placed
  on the underground mine workings. Currently, 223
  underground coal mines have approved roof control
  plans that allow for pillar removal. This
  represents 48 of all active underground coal
  mines.

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Subsidence Effects

• Creating large enough void translates through
  overlying bedrock and surficial materials
• Trough subsidence is predominant effect
  associated with longwall and full-extraction RP
  panels.
• Max. subsidence over high-extraction retreat
  operations averages 50-60 of extraction height.
• Max. subsidence over longwalls averages 60-70 of
  ext. ht.

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Subsidence Effects

• Depth affects amount of subsidence bulking of
  gob, arch effect, etc.
• Kathleen experienced 3.5 sub. W/ 6.5-7.0 ext.
  ht.
• Still falls within normal expected range, but
  should have been at high end or above the
  expected range in 110 overburden. Why?
• High percentage of competent rock made up total
  bedrock, 4 major limestone members in 80 of
  rock. Behaved like Appalachia. Rarity in IL
  basin.

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Indiana Regulation

• IC 14-34-1-3 PURPOSE OF ARTICLE (34)
• Assure that the coal supply essential to the
  nations energy requirements and economic and
  social well-being is provided and strike a
  balance between protection of the environment and
  agricultural productivity and the nations need
  for coal as an essential source of energy

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Indiana Regulation

• 312 IAC 25-4-91 Underground mining permit app.
  reclamation plans subsidence control plan
• Section 91 (b) (4, 5, 7) address measures to be
  taken in event planned subsidence will occur.

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DNR Web-site

• Underground Mining Subsidence Control Plan
• The DoRs subsidence specialist evaluates
  supplied information to obtain determination..th
  at planned subsidence mining, such as longwall
  mining or pillar removal mining, is designed to
  occur in a planned and predictable fashion, which
  will be conducive to the restoration of the land
  surface.

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Operational Requirements?

• Enlightened Senior Management
• Surface Control/Subsidence Rights
• Absence of Critical Structures
• RELIEF
• Good Planning
• Proactive State Reclamation Agency
• Conducive Geology Hydrology

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CLOSING REMARKS