2020-10-01_REVISION - C1981010 (2)

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Mr. Forrest Luke Page 3 of 4 September 2020 Rule 4.09.1(7): Disposal of Excess Spoil DRMS August 2020 The Division of Reclamation, Mining and Safety (DRMS), has reviewed Evaluation ofI and J Pit Spoil Pile Stability Report by Aga Associates. Inc. dated May 26, 2019 for the Trapper Mine Permit Revision PR-10. 4. In the Conclusion and Recommendations section of the report, the Operator states the spoil piles will be constructed in small lifts (20-40 feet) to allow for better compaction of the spoil particles. Pursuant to Rule 4.09.1(7), please explain how the spoil piles will be concurrently compacted to ensure mass stability and prevent mass movement. 5. Please provide the Rockscience Inc. slope stability analysis data for the Agapito Associates, Inc. geotechnical evaluation of the I and J Pits Spoil Piles to allow the Division to duplicate the analysis with Clover Technology's Galena software for verification purposes. Please include the profile geometries and the material properties used in the stability analysis, preferably in paper and electronic forms. Trapper Response to Comment 4: The spoil piles will be dumped in 20-foot lifts for the most part with the large overburden trucks providing the required compaction for the layers of fill. To sort the rock required for the underdrain, taller dump faces, up to 40 feet tall, will be utilized to collect the rock. Even allowing for this taller face, the compaction provided during this process allows for safety factors above 1.75 at the worst case, exceeding the 1.5 criterion. DRMS October 2020 Trapper's response is adequate. Trapper Response to Comment 5: The profile geometries are included separately as DXF files so that they may be opened as digital files and measurements taken from them. They are called A Section through D Section and their material properties are included in Table 1, Summary Numerical Model Input Parameters, Page 4 of Agapito Associates, Inc. report `Re: Evaluation of I and J Pit Spoil Pile Stability, Trapper Mine. DRMS October 2020 Trapper's response is adequate with the exception of: 5a. Please export the x,y coordinates from the DXF file crossections A-D into an excel file and submit the excel file to DRMS. Rule 4.23.2 Auger Mining DRMS August 2020 DRMS notes that as per the above referenced rule, auger mining shall maximize coal recoverability of remaining reserves after completion of mining. DRMS finds that there may be areas of undisturbed coal left in unmined sections that are in excess of 2500 feet apart. Given that the ownership is the State of Colorado with a Trapper Lease, please demonstrate: