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Mr. Eric Scott <br /> RE: Technical Revision No. 3 for Greeley Pit(M-1977-151) <br /> July 31, 2022 <br /> Page 2 of 3 <br /> Hiner recognizes the need to comply with the approaches outlined in the April 30, 2010, DRMS <br /> letter, and therefore for the time being proposes to bond to backfill a sufficient area to eliminate <br /> the 22.75 acre-feet per year of evaporative loss that is not covered by Hiner's current GIC <br /> ownership(Approach No. 1). Based on the net evaporation rate established in the SWSP,that area <br /> is approximately 8.3 acres. <br /> As shown in Figure 1, Hiner has already backfilled approximately 0.5 acres during the spring of <br /> 2022, thereby reducing the necessary backfill area to 7.8 acres. <br /> Hiner has identified an additional 3.0 acres to be backfilled in phases during the spring and fall of <br /> 2023. The depth of the ponds in these areas are relatively shallow, and Hiner estimates that filling <br /> these areas to an average depth of eight feet will be sufficient to eliminate the exposed groundwater <br /> surface to a depth of two feet above the prevailing groundwater table as required by the DRMS. <br /> The length of the interface between the fill area and the water is approximately 950 feet. Assuming <br /> the fill area is graded into the water at a slope of 3H:1 V and assuming the final compacted volume <br /> will be approximately 80%of the loose fill volume,I estimate that the amount of loose fill material <br /> required to backfill these 3.0 acres is approximately 52.6k cubic yards. <br /> An additional 4.8 acres would need to be backfilled to achieve the necessary backfill area. The <br /> location of these 4.8 acres has not been identified at this time,but assuming the same ratio of loose <br /> fill material would be required indicates that an additional 84.2k cubic yards would be needed for <br /> this as-of-yet unidentified fill area. <br /> Therefore, the total loose fill material required to backfill the necessary area totals approximately <br /> 136.8k cubic yards. A typical dump truck hauls approximately 14 cubic yards of loose fill material, <br /> indicating that approximately 9.8k truck loads would be needed to provide the necessary fill <br /> material. <br /> A stockpile of material of unknown volume is currently stored on site at the location indicated on <br /> Figure 1. However,most of this material will need to be hauled in from offsite and placed directly <br /> into the fill area. Hiner is working with nearby gravel pit operator Bucklen Equipment Company <br /> to acquire the necessary material and quoted Hiner a cost of$65 per truck load delivered to the <br /> Greeley Pit. Conservatively escalating that cost to $85 per truck load for placement and <br /> compaction would indicate a cost of approximately$833k for the material. In my opinion,it would <br /> be reasonable to increase the existing$47k bond by this amount in order to comply with Approach <br /> No. 1 of the April 30, 2010, DRMS letter for the exposed groundwater area not covered by <br /> Approach No. 4. <br /> To reiterate,Hiner intends to utilize a combination of backfilling and acquisition of additional GIC <br /> shares to comply with DRMS requirements. At this time additional GIC shares are not available, <br /> so for the purpose of this Technical Revision the bond is estimated based on the cost of backfilling <br /> only. <br /> www.applegategroup.com Denver • Glenwood Springs • Hotchkiss (303)452-6611 <br />