2023-05-05_INSPECTION - C1980007

Home Browse Search

April 26, 2023 C-1980-007/West Elk Mine LDS raise material higher than a single excavator could alone. The pile was within the footprint of the un-reclaimed area on the top of the LRP. Some material had sloughed off the north side of the temporary pile but had been caught by the berm. Aerial images of the area were collected with a drone and processed to produce a 3- dimensional digital model,using Pix4D Mapper. The volume of the temporary stockpile was estimated,using the same software. The software calculates the difference between the Digital Surface Model (DSM) and a base surface that is created by interpolating between the vertices of a user-created polygon. There are several methods that the software can use to create the base surface,but all give similar results. Using the default method (triangulation),the estimated net volume of the pile at the time of the inspection was 26,315 m3 (+/-402 m3). The currently approved PAP allows for the temporary stockpiling of 150,000 cubic yards of compacted refuse and/or coal on the RPE and LRP (Page 2.05-46). As discussed below,the volume of the temporary waste pile on the RPE at the time of the inspection was 36,732 m3 (+/- 918 m3);the total volume of temporarily stockpiled material is estimated at around 82,500 cubic yards. The Division finds that the configuration of the temporary fines pile is not out of compliance with either the Rules or the approved mine plan,however it is a large stockpile that does not have an approved design. The stockpile should not grow any larger, and should be reduced in size as soon as possible. Future permitting work will be necessary to clarify language in section 2.05.3 of the PAP discussing the configuration of temporary stockpiles, and to remove inconsistencies between pages 2.05-44 and 2.05-46. PROCESSING WASTE/COAL MINE WASTE PILES—Rule 4.10 and 4.11 Drainage Control; Surface Stabilization; Placement: At the time of the inspection ground conditions were still too wet to allow transportation of waste to the RPEE, so waste was continuing to be temporarily stockpiled on the RPE. The volume of the temporary stockpile was estimated at 36,732 m3 (+/- 918 m3), and the material remained within the footprint of the un-reclaimed area on the top of the RPE. ROADS—Rule 4.03 Construction 4.03.1(3)/4.03.2(3), Drainage 4.03.1(4)/4.03.2(4), Surfacing and Maintenance4.03.1(5) and (6)/4.03.2(5)and (6), Reclamation 4.03.1(7)/4.03.2(7): Wells Excavating had done work on the RPEE haul road to improve the surface and to clean the ditch in preparation for the transportation of waste to the RPEE,however continuing wet weather had led to several rockfalls and slumps in the days preceding the inspection that had partially blocked the road, and more work was necessary for it to be passable. SLIDES and DAMAGE-Rule 4.12: Surface slides and rockfall were evident around the wider area, as well as within the permit area(for example, on the haul road to the RPEE). Mine staff reported that the MSB slump had been moving again following the wet winter and spring, and Barr Engineering were being consulted on a mitigation plan. Drone imagery of the MSB was collected at 400' above the bench,which gave a ground sampling distance of approximately 2"per pixel. The raw images clearly show the cracks on the outslope of the bench. The images were processed to produce a DSM, and contours were generated at 2' intervals. The contours show how the surface has deformed. Number of Partial Inspection this Fiscal Year: 7 Number of Complete Inspections this Fiscal Year: 3 Page 3 of 14