REP12043

• Permit No: C1981044
• IBM Index Class Name: Report
• Doc Date: 2/12/1980
• Doc Name: GEOTECHNICAL ASPECTS OF EMPIRE ENERGY CORP PERMIT APPLICATION FOR UNDERGROUND EAGLE 5 & 9 COAL MINES
• From: MLR
• To: ROGER FUNSTON
• Permit Index Doc Type: SUBSIDENCE REPORT
• Media Type: D
• Archive: No

STATE OF COLORADO RICH aaD D. L/+MM. Goy^~~~~ 111 ^I~III ~II II1I ~II
DEPARTMENT OF NATURAL RESOURCES 11111 II 1 V
Harris D. Sherman, Executive Director gg9
MIlVED LAND RECLAMATION
723 Centennial Building, 1313 Sherman Street
Denver, Colorado 80203 Tel. [phone]
Haml~st J. Barry, 111,
Director
E M O R A N D U M
2 February 1980
T0: Roger Funston
FROM: Jim Pendleton
RE: Geotechnica spects of Empire Energy Corporation's Permit Application
' f the erground Eagle No, 5 and No, 9 Coal Mines
Pursuant to your request I have completed a review of the permit application
submitted by Empire Energy for the Eagle No. 5 and No. 9 Coal Mines, In
accordance with your indication of the applicant's desires, I have reviewed
the application to ascertain conformance with the permanent federal regs.
Mr comments regard three general areas of concern: (1) Ground surface
subsidence, (2) protection of the hydrologic balance, and (3) stability of
the proposed mining waste disposal pile.
Ground Surface Subsidence
In brief ,the permanent federal regulations require that underground mining be
planned and conducted in such a way as to prevent "material damage to the
surface". The applicant is required to submit a "subsidence control plan",
Among other specifics the regs require protection of areas of renewable
resources, with particular emphasis placed upon perrenial streams and aquifers
which constitute "significant source of water supply to any public water system".
Empire Energy's application includes section 4.6, entitled "Subsidence Controlled
Survey". It appears that the applicanC intends this section to constitute the
required subsidence control plan. In essence, the applicant proposes to prevent
material damage to the surface and renewable resource areas through a program of
partial extraction. This approach is specifically allowed in section 817.121(a)
of the permanent federal regulations.
The permit application utilizes an analytical technique based upon a paper by
A, H, Wilson & D. P, Ashwin titled "Research into the Determin.stion of Pillar
Size", published in The Mining Engineer in June, 1972. This technique purports
to determine the minimum pillar size necessary to assure long term stability
by equating the imposed load upon a pillar with an equation d~:scribing the
theoretical carrying capacity of the pillar. I have briefly reviewed Wilson
& Ashwin's paper, which presents a hypothetical development of equations to
define the imposed loads and theoretical carrying capacity of pillars, Their
hypothesis assumes material properties characteristic of the Anthracite coals
of their native Brittain. These Anthracite coals manifest angles of internal
friction higher than the Subbittuminous coals characteristic of Colorado.
This factor results in their expression for carrying capacity being somewhat
high for the Eagle Mine situation. Furthermore, their expression for applied