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October 4, 2022 C-1981-019/Colowyo Coal Mine ZTT <br /> Inspection Topic Summary <br /> NOTE: Y=Inspected N=Not Inspected R=Comments Noted V=Violation Issued NA=Not Applicable <br /> N -Air Resource Protection N -Roads <br /> N -Availability of Records N -Reclamation Success <br /> N -Backfill&Grading N -Revegetation <br /> N -Excess Spoil and Dev. Waste N - Subsidence <br /> N -Explosives N - Slides and Other Damage <br /> N -Fish&Wildlife N - Support Facilities On-site <br /> R -Hydrologic Balance N - Signs and Markers <br /> N -Gen. Compliance With Mine Plan N - Support Facilities Not On-site <br /> N -Other N - Special Categories Of Mining <br /> N -Processing Waste N -Topsoil <br /> COMMENTS <br /> This was a partial inspection of the Colowyo Mine conducted by Zach Trujillo of Colorado Division of <br /> Reclamation,Mining and Safety(DRMS)on October 4, 2022.Tony Tennyson representing Colowyo Coal <br /> Company(Colowyo)accompained the inspection.The weather for inspection was clear with wet gound conditions <br /> from previous precitation events.High temperatures during the inspection were around 65 degrees fahrenheit. <br /> The primary focus was to inspect the Prospect Drainage and associated ditches in the East Pit. On October 2,2022, <br /> an intense storm event dropped approximately 0.86 inches in 3 hrs, 0.6 inches of that in an hour.This storm event <br /> impacted the Final East Pit Ditch which allowed water from disturbed runoff to flow off-site. <br /> HYDROLOGIC BALANCE -Rule 4.05 <br /> Drainage Control 4.05.1,4.05.2,4.05.3; Siltation Structures 4.05.5,4.05.6; Discharge Structures 4.05.7,4.05.10; <br /> Diversions 4.05.4;Effluent Limits 4.05.2; Ground Water Monitoring 4.05.13; Surface Water Monitoring 4.05.13; <br /> Drainage —Acid and Toxic Materials 4.05.8;Impoundments 4.05.6,4.05.9; Stream Buffer Zones 4.05.18: <br /> The following precipitations amounts were measured at the East Pit rain gauge adjacent to the substation located <br /> in the East Pit near the haul road: <br /> • 9/30/22— 0.42 in. <br /> • 10/1/22— 0.31 in. <br /> • 10/2/22— 0.86 in. in 3 hr duration(0.6 in.in 1 hr duration) <br /> The Final East Pit Ditch(FEPD)is located in the southern extent of the East Pit.It consists of a total of three <br /> reaches separated by two stock tanks,EP1 and EP2.The upper portion of the FEPD is Reach 3 which flows into <br /> EP2,followed by Reach 2. Reach 2 flows into EP1 before flowing down the final length of the ditch,Reach 1. The <br /> FEPD then connects into the South Collection Ditch where water then flows to the Prospect Pond where it is <br /> passively treated and discharged. See Figure 1 at the end of this report. <br /> Reach 3 of the FEPD was stable with no issues observed (Photo 1). Stock tank EP2 held water with minimal <br /> Number of Partial Inspection this Fiscal Year: 3 <br /> Number of Complete Inspections this Fiscal Year: 1 <br /> Page 2 of 20 <br />