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Mr.Chris Oestreich May12,2023 Page 2 and was presumably logged from cuttings. Based on our experience and observations made during construction of the slurry wall,the bedrock weathered zones tend not to exceed three feet. In addition,sandy clay overburden was encountered during slung wall construction. The total thickness of the alluvial deposit ranged from approximately 34.5 to 46 feet. Groundwater was encountered in the borings at depths ranging from approximately four(4)to twelve(12)feet below the ground surface. From a geotechnical standpoint,the sand and gravel make up most of the mine slope. The sand and gravel are generally strong and stable when dewatered. STRUCTURES WITH 200 FEET OF DISTURBED AREAS The known,permanent,man-made structures within 200 feet of the proposed mine limits that are not owned by the miner are listed below. 1. The Plumb Ditch on the south and east parts of the mine. This ditch is approximately 40 feet from the mine limits at its closest point on the southwest part of the mine. 2. Fences encroaching to within approximately 40 feet from the mine limits. 3. An unnamed ditch approximately 45 feet from the mine limit on the southeast part of the mine. 4. A water turn-out structure on the south part of the site approximately 40 feet from the mine limits. 5. Farm buildings southwest of the mine(Borys property)approximately 180 feet from the mine limit. 6. Weld County Parkway approximately 125 feet southwest of the mine limit. 7. A gas line approximately 45 feet to the east of the mine limit. This gas line may be abandoned following the plugging and abandonment of area gas/oil wells. 8. An unnamed ditch approximately 45 feet east of the mine limit. 9. A farm road approximately 45 feet from the north mine limit. 10. Overhead utility lines approximately 45 feet from the north mine limit. 11. A farm road approximately 50 feet from the west mine limit. These structures are closest to the planned mine limits and will be stable per the stability analyses described herein. All other known structures are at greater distances and,therefore,will also be stable. STABILITYANALYSES Division of Reclamation and Mining Safety(DRMS)drafted a policy regarding stability analyses of neighboring structures. The policy summarizes adequate factors of safety(FOS)for non-critical and critical structures. Most of the structures at the Nissen Farms Mine are considered critical structures. The FOS are for both static and seismic(ground accelerations from an earthquake)stability analyses are listed in the DRMS policy. For generalized strength assumptions and critical structures,an FOS of 1.5 is considered sufficient for static conditions and an FOS of 1.3 is considered suitable for seismic conditions. The stability of structures within 200 feet of the proposed mining limits was evaluated at the most critical representative section under anticipated loading conditions as discussed below. The GALENA computer program was used for the analysis. The method for selecting the critical failure surface for each analyzed loading condition was the following. The Simplified Bishop's Method of Analysis was used to find the critical failure surface by randomly searching 22,001 trial failure circles over a broad range of the slope surface and at the structure in question to evaluate the lowest FOS. Both static stability under anticipated mining conditions and seismic stability under peak ground acceleration(PGA)loads were performed. Seismic loading was obtained from the U.S.G.S. Unified Hazard Tool attached to this report. Review of the Hazard Tool indicated a maximum horizontal acceleration of 0.0715g with a return period of 2,475 years for the site. The most critical cross section location was selected and analyzed as described below.