2012-07-02_REVISION - C1981019

• Permit No: C1981019
• IBM Index Class Name: Revision
• Doc Date: 7/2/2012
• Doc Name: 2nd Adequacy Letter
• From: DRMS
• To: Colowyo Coal Company
• Type & Sequence: TR95
• Email Name: RDZ
• Email Name: DIH
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF RECLAMATION, MINING AND SAFETY
Department of Natural Resources
1313 Sherman St., Room 215
Denver, Colorado 80203
Phone: [phone]
FAX: [phone]
July 2, 2012
Kurtis Blunt
Colowyo Coal Company
5 731 State Highway 13
Meeker, CO 81641
Re: Colowyo Coal Company, Permit No. C -81 -019, TR -95 — Revision of hydrologic methods,
Second adequacy letter
Dear Mr. Blunt:
COLORADO
Q I V I S I O N O F
RECLAMATION
MINING
SAFETY
John W. Hickenlooper
Governor
Mike King
Executive Director
Loretta E. Pineda
Director
In a letter dated June 1, 2012 the Division provided comments based on our preliminary adequacy
review (PAR). We received your responses to our PAR on June 26, 2012 (letter from Tony Tennyson
dated June 25, 2012), and have additional comments based on these responses. The following lists the
Division's original comments in italics. Colowyo Coal Company (CCC) responses are left out for the
sake of brevity.
Over the last five years, the Division, Colowyo Coal Company staff, and CCC consultants have put in a
great deal of time and effort focused on preventing water quality violations and improving the safety of
public users ofHighway 13 below Prospect Pond This effort
has included improving modeling
accuracy. Colowyo most recently updated the approved curve numbers at the mine through technical
revision 73 (TR -73, June 2009). As part ofTR -73, Colowyo identified soils on the mine site as C soils
and associated CN values were approved.
The Division is certainly willing to consider changes in Hydrologic Soil Group (HSG) values and the
related curve number values. However, we stand by our assertion that information from other mines and
information from a small area on Colowyo Mine is not enough information to identify all reclaimed land
on Colowyo as C soils.
Furthermore, the intent of TR -73 was not "more conservative modeling" but rather to move the model
closer in line with flows witnessed on the ground.
CCC references the 1981 report by Striffler and Rhodes, `Hydrologic and Erosional Characteristics of
Regraded Surface Coal Mined Land in Colorado, " which includes sample sites at eleven surface mines
in Colorado. 'Specific to Colowyo, the sampling was done on 11 acres of lands reclaimed at Colowyo in
1978. Colowyo now has thousands ofacres ofreclaimed lands. On page 14 of this report, the authors
state, `However, any generalizations about the similarities of surface hydrology or regraded coal mined
land from state to state, between areas within a mining region, or even between sites within a mine are
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