2021-05-27_PERMIT FILE - C1981019A ‎(7)‎

• Permit No: C1981019A
• IBM Index Class Name: Permit File
• Doc Date: 5/27/2021
• Doc Name: Addendum Collom and South Taylor Highwall Mining Geotechnical Design
• Section_Exhibit Name: Volume 20 Exhibit 27 Item 7
• Media Type: D
• Archive: Yes

Agapito Associates, Inc. www.agapito.com
ENGINEERS & GEOLOGISTS
NPENEW
April 23, 2021 227-43
Mr. Lee Sampson, P.E.
Senior Mining Engineer
Colowyo Coal Company
5731 Highway 13
Meeker, CO 81641-9124
Re: Additional Highwall Mining Areas, Collom Box Cut and South Taylor Pit, Colowyo
Coal Mine, Meeker, Colorado
Dear Lee:
As you requested on behalf of Colowyo Coal Company(Colowyo),Agapito Associates,Inc.(AAI)
has reviewed additional target areas for potential highwall mining (HWM) near the Collom box
cut (Collom) and from the South Taylor Pit (South Taylor). AAI previously studied HWM areas
for Collom and South Taylor and developed detailed reports for each.',2 The additional targets
relative to the previously studied areas are shown in Figure 1.
AAI's previous South Taylor study' included mining of the G7 Seam, and where the G7 and G8
Seams come together, their combined thickness (referred to as the G78 Seam). This mining was
planned from the low wall (southeast portion) and endwalls (southwest and northeast portions) of
the pit. Colowyo is currently considering an additional area not specifically addressed in our
previous report, in the northwest and southwest portions of the pit, where only the G7 Seam will
be targeted. The original study area and the expanded area for South Taylor are shown in Figure 1.
AAI's previous Collom study2 included mining of several seams from the low wall and endwalls
of the Collom Box Cut. Most of the targets are seam splits that occur close to one another, with
little or no parting thickness. For example, the B2/B3 Seam consists of the combined B2 and B3
splits. Mining from the low wall generally included HWM panels mined downdip to the north.
This previously studied HWM area in Collom is also shown in Figure 1. Colowyo is currently
considering two additional areas not specifically addressed in our previous report. The area in
Figure 1 labeled "North Target Area" may be mined updip to the south, and targets the B1/B2,
C3/C5, D1/D2, and E2 Seams. The area labeled "South Target Area" may be mined generally
along strike from either side of the drainage and targets the D 1/D2 and E2 Seams.
' Agapito Associates,Inc. (2014),"Geotechnical Design and Operational Considerations for Highwall Mining, South
Taylor Pit G78 and E/D2 Seams, and West Pit F, E, D2, and C Seams," report to Colowyo Coal Company,
April 21, 78 pp.
2 Agapito Associates, Inc (2019a), "Geotechnical Design and Operational Considerations for Highwall Mining,
Collom Box Cut,"report to Colowyo Coal Company,November 20, 143 pp.
DISCLAIMER:This report contains professional opinions based on information provided by the Owner. AAI makes
no warranties, either expressed or implied, as to the accuracy or completeness of the information herein. Opinions
are based on subjective interpretations ofgeologic data;other equally valid interpretations may exist. Identification
and control of hazardous conditions are the responsibilities of the Owner.
1536 Cole Blvd.,Suite 310, Bldg. 4 715 Horizon Drive, Suite 340
Lakewood, CO 80401 Grand Junction, CO 81506 USA
+1 303.271.3750 +1970.242.4220