REV105700

• Permit No: C1982057
• IBM Index Class Name: Revision
• Doc Date: 11/10/2003
• Doc Name: Adequacy Review Letter
• From: DMG
• To: Seneca Coal Company
• Type & Sequence: PR4
• Media Type: D
• Archive: No

acid-forming water discharge is anticipated from the highwall openings, with
reference to the appropriate sources of such statements in the hydrologic
analyses provided for the respective coal seams in the Groundwater sections of
the body of the Permit Application Package. As a backup, please add "However, if
toxic-forming or acid-forming water discharge is encountered, the opening of
discharge will be backfilled within 72 hours after completion."
15. Rule 4.23.2(4)(b) requires that each auger hole not discharging water shall be sealed as
in 4.23.2(4)(a), to close the opening within 30 days following completion. The application
is not in compliance with this rule. Please add to Paragraph 5.1 10 on page 12.4-3, that
"However, no highwall entrance will be left open more than 30 days."
16. Rule 4.23.2(6)(d) requires the Division to prohibit auger (highwall) mining if it determines
that subsidence resulting from auger mining may disturb or damage powerlines,
buildings, or other facilities. Subsidence is not expected (page 12-4-1 of the application),
but if it does occur, no such damage would result. However, a minor wording change is
requested to more specifically address pertinent regulatory requirements. Please amend
the sentence, on page 12-4-1, that reads: "If subsidence does occur there are no
structures that will be highwall mined underneath." to read "There are no
structures on areas overlying, or within a possible subsidence angle of draw of,
highwall mining."'
17. Rule 4.23.2(7)(a) requires that auger (highwall) mining shall be conducted in
accordance with the bac)~Iling and grading requirements of 4.14. Please
include, under the comments for Rule 4.23.2(7) on page 12-4-1, a description of any
waiver requested to the 180-day rough backfilling and grading of pit areas used for
access for highwall mining, or include a cross reference to such requested waiver
in Tab 19.
2.05.3(4) Ponds, impoundments, other treatment facilities and diversions
18. Sediment Pond 017 as-built designs, stability analysis and certification were submitted within
the PR-4 application. The pond was built one foot shallower but with a slightly larger
capacity than original design due to greater surtace area. Pond 017 construction meets
applicable design requirements, and the exceptionally thorough and well presented
construction certification demonstrates that the structure was built to specifications.
The application will need to be revised with regard to the Pond 17 stability analysis, to
incorporate certain supplemental information and amended analysis submitted informally
during the review. We have the following specific comment.
Please include in the Sedimentation Pond 017 Stability Analysis of As-Built
Conditions Seneca II W Mine Area Routt County, Colorado, August 2003, the
source of material unit weights as was done for the effective friction angle and
effective cohesion on page 2. Addendum 13-5H-D Pond 017 Compaction Testing
Results record dry densities ranging from 97.6 to 110.1 pounds per cubic foot (pcf)
for compacted embankment materials. The stability analyses used dry densities of