APPCOR11818

• Permit No: C1981047
• IBM Index Class Name: Application Correspondence
• Doc Date: 10/30/1981
• Doc Name: MEMO SUPPLEMENTAL STABILITY AND SUBSIDENCE SUBMISIONS FOR BLUE RIBBON COAL MINE
• From: MLR
• To: TOM GILLIS
• Media Type: D
• Archive: No

STATE OF COLORADO
qIG HAflD D. Ld•Govc rn nr
DEPARTMENT OF NATURAL RESOURC ES
D. Monte Pascoe, Executive Director
MINED LAND RECLAMATION
423 Centennial Building, 1313 Sherman Street
Denver, Colorado 80203 Tel. [phone]
III IIIIIIIIIIIII III
999
David C. Shelton
Director
M E M O R A N D U M

30 October 1981
TO: Tom Gillis
FROM: Jim Pendleton
RE: Supplemental abil'ty and Subsidence Submissions for
B1 Ribbon Coal Mine
Pursuant to your request, 2 have reviewed the supplemental materials
submitted by Western Associated Coal Corporation for the Blue Ribbon Coal
Mine. 2 forward the following cormnents for your consideration.
Portal and Well Sealing:
The sealing techniques descriptions and drawings are acceptable,
with one deficiency in the companys' presentation. The operator fails to
discuss whether mine drainage will occur at the location of the portals
following reclamation and sealing. The hydrology section should be amended
to specifically discuss this topic.
Portal Bench and Highwall Stabilitu:
The supplemental materials contain discussions of both operational and
backfilled portal bench and highwall slope stability. The applicant and
the applicants' consultants both recognize the existence of a slope
instability problem on the portal bench facial slope. The applicant has
submitted a remedial plan to eliminate this problem in response to an
inspection notice of violation (October 22, 1981 letter by Ute Engineering
& Surveying Company). This design includes installation of a perforated
interceptor drain ti le and a regrading of the bench surface, both intended
to decrease infiltration of moisture into the bench which the applicant
believes is the cause of the problem. The applicant further commits, in
the amended application, to the completion of appropriate geotechnical
and stability analyses and the installation of three standpipe piezometers
to monitor the phreatic surface and degree of saturation of the portal
bench. This proposal and the applicants' indication of completion of the
remedial construction by February of 1982 can be approved immediately
in order to expedite correction of the problem and completion of the
geotechnical analyses.
The amended application also commits the applicant to completion of
a stability analysis of the proposed final backfilled configuration,
including shear strength testing and definition of the phreatic surface.
The application incorporates a request for variance from AOC based upon
the existence of steep slope mining conditions within the portal area.