APPCOR12967

• Permit No: C1987072
• IBM Index Class Name: Application Correspondence
• Doc Date: 5/5/1987
• Doc Name: REMAINING ADEQUACY CONCERNS-LA PLATA 1 PERMIT APPLICATION
• From: MLRD
• To: PETER OCONNOR
• Media Type: D
• Archive: No

III 111111111! 11
STATE OF COLORADO
Roy Romer, Gove
DEPARTMENT OF NATURAL RESOURCES
MINED LAND RECLAMATION DIVISION
DAVID C. SHELTON, Dlreetor
DATE: May 5, 1987
T0: Peter O'Connor
FROM: Tom Gillis `~~
RE: Remaining adequacy concerns - La Plata #1 Permit Application
Backfilling and Grading
The backfilling and grading portion of the permit application text still
contains inconsistent and contradictory information regarding the
proposed backfilling scheme. Certain portions of the text describe a
backfilling plan which would return the disturbed areas to approximate
original contour; other portions describe a plan to backfill only a
portion of the highwall or face-up. The application also contains
unsubstantiated statements regarding the existence of "natural highwalls"
within the mine area and the difficulty in achieving a static factor of
safety of 1.3 for areas backfilled to angle of repose. Additionally; the
proposed post-mining topography map depicts little or no backfilling of
the east and west portions of the portal bench, substantial backfilling
and over steepening of slopes in the center of the portal bench; and no
backfilling of the access road cut or lower facilities area. Based upon
the Division's calculations, the backfilling plan currently proposed
results in a substantial fill material deficit which would reouire the
importation of fill material from an off-site location in order to
achieve the proposed post-mining contours.
Based on the considerations described above, the applicant needs to amend
the backfilling and grading plan portion of the text and the post=mining
topography map to describe and depict an appropriate, consistent
backfilling and grading plan for the portal area, access road cut; lower
facilities area, and sediment pond. Specifically, the following items
need to be adequately addressed:
In consultation with the Division's engineering geologist,
Mr. Jim Pendleton, the applicant needs to prepare an appropriate
stability analysis of a complete highwall backfill scenario (the
"A.O.C." case). If the analysis results in a static factor of
safety of 1.3 or greater, the proposed backfilling and grading plan
must be amended to provide for complete backfilling of the exposed
highwall. An exception to this reouirement will be considered if
the applicant can sufficiently demonstrate that the original
pre-mining configuration of the portal
423 Centennial Building, 1313 Sherman Street Denver, Colorado 80203-2273 Tel. [phone]