2025-05-22_INSPECTION - C1981019

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May 15, 2025 C-1981-019/Colowyo Coal Mine HR1 Number of Partial Inspection this Fiscal Year: 8 Number of Complete Inspections this Fiscal Year: 3 Page 3 of 11 Area 4: Area 4 is comprised of two areas, bisected by Moffat CR 17 which are reclaimed water line areas. The parcel to the northwest is comprised of 10.4 acres and the parcel to the northwest is comprised of 17.7 acres. Reclamation activities included backfilling and grading the trench used to construct the water line, topsoiling and seeding. Area 5: Area 5 is comprised of three parcels in the West Pit that total 99.1 acres. Reclamation activities for all three parcels include backfilling and grading to the approved post mine topography, replacing topsoil, and seeding to the approved seed mixture. Release acreage in West Pit, Area 5, was walked during the inspection. All other areas were traversed via a vehicle and were supplemented with visual and sporadic on the ground inspection checks of these areas. The Division has summarized observations for each of the five areas. Area 1 (Photo 4): This area was accessed from Section 25 Pond and inspected on foot. There were no signs of erosion or unevenly graded surfaces. The old drill pad area was indistinguishable from the surrounding areas. While Phase I only seeks release for backfill and grading activities, it can also be noted that mature and native vegetation was covering the entirety of this area. Area 2 (Photos 5 and 6): This area was first accessed from its midpoint and inspected via vehicle down its southern length. The northern portion of the reclaimed water line acreage was viewed from Collom Haul Road. No erosional issues were noted and the backfilled and graded trench area blended in very well to the surrounding area. Again, mature vegetation had taken over the entirety of the release area. Area 3 (Photos 7-10): This area is comprised of twelve smaller areas, all of which were driven to and inspected and or inspected from alternate vantage points when slopes became too steep to access by vehicle. Areas were in various states of revegetation and grading work was consistent throughout with no sign of major riling or washout- even on the steepest slopes. Area 4 (Photos 11 and 12): The northwestern portion of this area was inspected first and traversed by vehicle. The southwestern parcel was viewed from its northern end and viewed from vantage points along the site entrance road. Grading of the backfilled trench areas were indistinguishable from the surrounding undisturbed landscape. Area 5 (Photos 1-3): Elevational GPS points were collected at twelve different locations along the West Pit parcels, following the transect lines A-A’ and B-B’ as shown on the bond release Map 2 provided in the Bond Release application and shown below in Figure 1. GPS points were taken along the transects at approximately every 400 ft at a known survey station point. In total, 12 GPS points were collected. These point locations are labeled below on Figure 1 and summarized in Table 1. The GPS elevation information will be post- processed and compared to the data provided by Colowyo to verify the approved post-mining topography has been achieved. Discussion of this analysis can be found in the SL-24 Findings Document. The West Pit reclamation parcels were well graded and cross ripped for erosion protection. An example of the surface roughening lines used for erosional protection can be seen in Photo 1. No major erosional issues were noted throughout all three reclamation parcels. One mid-size rill, approximately 1.5 ft wide was noted by staff for future repair. However, this feature was not an overall concern to the Division in regard to the Phase I release. Overall, the three parcel areas were graded to allow proper drainage and tie- in edges were well matched to surrounding areas that have not yet been regraded to approximate original contour. No issues were observed with any of the three reclamation parcels.