2019-06-25_REVISION - C1981035

• Permit No: C1981035
• IBM Index Class Name: Revision
• Doc Date: 6/25/2019
• Doc Name: Adequacy Review - Preliminary
• From: Tom Bird
• To: DRMS
• Type & Sequence: TR27
• Email Name: RDZ
• Media Type: D
• Archive: No

GCC
GCC Energy, LLC
Telephone: [phone] County Road 120
Energy "Safety as a Value" Facsimile: 970.385.4638 Hesperus, CO 81326
Appendix 1O
4. The cover pages for Appendices 10(4), 10(4A) and 10(4B) appear to have been mislabeled
as 4(4), 4(4A) and 4(4B). Please update these cover pages.
GCCE June 25, 2019: Cover pages for Appendices 10(4), 10(4A) and 10(4B) have been properly
labelled as per your suggestion. Appendix 10(4) (see#5 below) has been replaced in its entirety.
Revised cover pages are included to replace those in Appendices 10(4A) and 10(4B).
5. Page I of the Stoner report references the Division of Minerals and Geology;please update
to Division of Reclamation, Mining and Safety. Also on this page, there is a reference to
Rules 2.05(8), 2.50(9) and 2.05(10). Should these be 2.05.3(8) and 2.05.3(9)?If so, please
update the report.
GCCE June 25, 2019: The reference in the Stoner report to Division of Minerals and Geology
describes a Division stipulation which was, at the time,issued by the Colorado Division of
Minerals and Geology. Also, the Stoner report Appendix 10(4) page 1 has been revised as per
your suggestion. Revised Appendix 10(4)is included with this submittal.
6. Per Rule 4.10.1(1)(a), coal mine waste banks must be constructed in accordance with
Rules 4.09.1 and 4.09.2. Rule 4.09.2(2)(d) includes underdrain minimum size criteria.
The proposed underdrain extension does not meet this criteria. However, the Division
approved an alternative sizing with the currently approved underdrain for the King I
Refuse Pile based upon the information provided in Appendix 10(1) in the current PAP.
Per Rule 4.10.3(5), please provide additional information that ensures the proposed
underdrain size is sufficient to alleviate water within the entire refuse pile, including the
existing pile and the proposed expansion.
GCCE June 25, 2019: The underdrain sizing was based upon the original design included in the
original 1997 Don May report. This original underdrain sizing was checked against the
recommendations made by Trautner Geotech in its July 2014 report. Section 6.4 of the Trautner
report identified that there was a lack of pre-existing subsurface springs suggesting that
subsurface water migration into the deposit would not be significant. The Trautner analysis
assumed a steady state flow within the waste pile while acknowledging that the condition
provided the most conservative case even though it was highly unlikely to ever occur.
The Trautner report determined that based upon the small amount of water that may
potentially migrate through the waste pile, the design of the subsurface drain was not considered
to be a critical portion of the design. The location of the proposed underdrain system was
determined to be the critical consideration to ensure that all portions of the proposed waste pile
are allowed to freely drain. The Trautner report recommended that the underdrain consist of 2-
4 [ft3/ft] of trench for the underdrain construction based upon an area/footprint of 27,000 [ft2]
(assumes achieving a steady state flow within the waste pile).
The waste pile footprint for TR-27 is roughly 140,000 [ft2],which is slightly over 5x larger than
the area considered in the July 2014 Trautner report. This increased waste pile area also results
in an increase to the recommended underdrain sizing to 10-just over 20 [ft3/ft] of trench for the