Southern High Plains Project

A drilling investigation of the hoist shaft and air shaft for the Satanic Bluebird Coal Mine was completed in 2023 (see Appendix A). This report provides information critical to the Satanic Bluebird Grouting Project and should be reviewed and understood. The Hoist Shaft dimensions are approximately 20-28 feet by 9-14 feet by 205-217 feet deep and is reported to be a 2-3 compartment shaft. There may be a manway to the north side of the shaft location (shown on the 1932 mine map). The total approximate volume of the Hoist Shaft based on these dimensions ranges from 1400 to 2800 cubic yards. Drilling logs indicate approximately 23 feet of a clayey fill soil plug, a large void space (estimated 27 ft by 17 ft by 27 ft high) under the soil plug, then discontinuous void and rubble (wood, cobbles, granite, concrete, steel, and debris) to the bottom of the shaft. Refusal on steel debris in one boring was at 184 ft below ground surface, which is not expected to be the total depth of the shaft. The Air Shaft is a decline at approximately 45° to the 200 ft level of the mine workings. Mine maps indicate there may be a horizontal bench around 50-60 feet below ground surface. The Air Shaft dimensions are approximately 4-10 feet by 4.5-8 feet by 290-345 feet long. Based on these dimensions, the total approximate volume of the Air Shaft is 230-880 cubic yards. Drilling logs indicate 13-20 feet of alluvium, void and rubble ranging from 22.5 to 69 feet below ground surface, and Laramie Formation bedrock. Void spaces were measured from 5 to 21 feet in height. Groundwater is present in the mine and was encountered at about 19-25 feet below ground surface in the Hoist Shaft, and 38-40 feet below ground surface in the Air Shaft borings. The Satanic/Bluebird Grouting Project is the second phase of this work. Compaction grout will be used to fill the void and rubble spaces in the two shafts in order to stabilize against future mine opening events. In the area of the Hoist Shaft, a drilling platform will be constructed to allow access over the shaft location. One to two borings approximately two hundred (220) linear feet will extend to the bottom of the hoist shaft, and approximately one thousand two hundred (1200) cubic yards of compaction grout will be injected into the shaft. In the area of the Air Shaft, two to three borings approximately one hundred (150) linear feet will extend into the angled shaft north of the bench location. Approximately two hundred fifty (250) cubic yards of compaction grout will be injected into the air shaft. The total project work will include drilling and casing up to four hundred (400) linear feet of borings to install up to one thousand five hundred (1,500) cubic yards of low-slump grout, in stages, using pressure grouting techniques, monumenting the shaft locations, and reclaiming disturbed areas.