REV96542

• Permit No: C1981019
• IBM Index Class Name: Revision
• Doc Name: WEST PIT EXCESS SPOIL FILL
• Type & Sequence: PR1
• Media Type: D
• Archive: No

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WEST PIT EXCESS SPOIL FILL
The following information is submitted to the Division in
order to meet the requirements regarding permanent excess spoil
disposal structures in Rules 2.05.3(6)(b), (c) and 4.09 Disposal of
Excess Spoil.
BACKGROUND
On March 1, 1991, CTL/Thompson, Inc. completed the report
"Geotechnical Investigation, West Pit Excess Spoil Disposal Site,
Colowyo Coal Mine, Moffat County, Colorado". The report provides
a geotechnical evaluation of the West Pit Fill area and a stability
analysis of Colowyo's proposed design for the fill. The proposed
design for the fill utilized by CTL/Thompson for their analysis was
a fill similar in construction to the Streeter Fill that is
designed and constructed under the alternative design standards set
forth in Rule 4.09.1(3). The results of the site investigation,
stability calculations and knowledge of the highly successful
performance of the Streeter Fill lead CTL/Thompson to a number of
findings and recommendations for construction of the West Pit Fill.
A design and construction plan for this fill which followed
closely the design and construction of the Streeter Fill was
subsequently submitted to the Division on May l0, 1991.
MLRD later reviewed Colowyo's proposal during the preliminary
adequacy review process.
This review resulted in a determination that although MLRD
essentially believed the West Pit Fill could be constructed
appropriately under Rule 4.09.1(3) as designed, OSMRE would require
the fill be constructed under the requirements of Rule 4.09.2
Valley Fill. OSMRE rational was that the specific design
requirements of Rule 4.09.2 Valley Fills, have precedence over Rule
4.09.1(3) General Requirements.
On November 19, 1991, Colowyo met jointly with representatives
of CMLRD and OSMRE to discuss the permitting of the two excess
spoil fills; West Pit and Section 16. The meeting (see attached
memo from OSMRE) led to a discussion of the ability of the excess
spoil fill designs to meet a number of the specific requirements of
Rule 4.09.2 Valley Fills.
Colowyo agreed that the design and stability analysis would be
supplemented so as to demonstrate compliance with Rule 4.09.2(3)
(a,b,c,d). CTL/Thompson completed a review of this Rule in their
correspondence dated December 16, 1991 attached herein.
Colowyo also committed to meeting the requirements of a
subdrainage system to be extended from the head to the toe of the
fill. CTL/Thompson had initially provided a design for a
controlled underdrain under a portion of the fill and a gravity