2021-03-20_REVISION - C1981019

• Permit No: C1981019
• IBM Index Class Name: Revision
• Doc Date: 3/20/2021
• Doc Name: Adequacy Review
• From: Colowyo Coal Company
• To: DRMS
• Type & Sequence: TR145
• Permit Index Doc Type: General Correspondence
• Email Name: ZTT
• Email Name: JDM
• Media Type: D
• Archive: No

3/23/2021 State-co-us Executive Branch Mail-Fwd:[EXTERNAL]Colowyo Mine TR-145 Adequacy Letter
STATE OF DRMS—CoalAdmin -DNR, DNR<dnr—drms—coal—[e-mail]>
COLORADO —
Fwd: [EXTERNAL] Colowyo Mine TR-145 Adequacy Letter
1 message
Trujillo - DNR, Zach <[e-mail]> Mon, Mar 22, 2021 at 5:41 PM
To: DNR DRMS_CoalAdmin - DNR<dnr—drms—coal—[e-mail]>
The following is correspondence from Colowyo (C-1981-019)to the Division regarding TR-145. Thanks.
---------- Forwarded message---------
From: Tennyson, Tony(Colowyo) <[e-mail]>
Date: Sat, Mar 20, 2021 at 10:51 AM
Subject: RE: [EXTERNAL] Colowyo Mine TR-145 Adequacy Letter
To: Trujillo- DNR, Zach <[e-mail]>
Cc: Gilbreath, Chris <cgiI breath @tristategt.org>
Zach,
Per comment 5 in the TR-145 adequacy you provided on Friday March 19. If I respond to this latest comment now
(below in italics),you will get the just about the same exact response that I have provide the last two adequacy
rounds. I have included part of the latest comment please refer to the yellow highlights specifically.
"Regarding curve numbers and stage of reclamation, the PAP shows under Table 1, SCS Curve Number
(page 4 of Exhibit 7) for lands with less than three years of vegetation growth, the CN value should be
greater than 62. Please provide and explanation to why most of the areas in the East Taylor Pond
watershed have a CN value of 62 despite the fact that Map 29 shows significant reclamation after year
2020.
All the reclaimed areas presented on Figure Exh. 7-14ET 2 that are reclaimed less than three years do have a higher
curve numbers than 62. They are all presented and modeled as topsoiled and seeded with a curve number of 80 as
required by the Exhibit 7,Table 1 in the permit.
have attached Figure Exh. 7-14ET 2 for a visual demonstration only for the Division. I superimposed the spoil grading
blocks and associated timing from Map 29 also submitted under this TR, and all the reclaimed areas/year seeded
blocks for the entire East Taylor Watershed. As the figure demonstrates, and as I have continued to state to the
Division in two adequacy responses now,the subwatersheds, curve numbers and applicable timing applied for the
East Taylor watershed model are in compliance with Exhibit 7 in the permit. This model also demonstrates
compliance with the subparts of Rule 4.05.9.
For the northern portion of the watershed, since the Division will not allow us to apply for Phase III bond release,
there are some reclamation units at the northern end of the watershed that could be Phase III released that are still
modeled with a curve number of 62. In reality, given the age of these some of these reclamation units they could be
modeled with a lower curve number at this point if the permit allowed for it.
https://mail.google.com/mail/b/ALGkdOyxwy3ZsZS73bfyjuyXJXKgdOuyRP01 jondRRKsTjsynVC-/u/O?ik=deb7fOcd20&view=pt&search=all&permthid=th... 1/3