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SUBSURFACE CONDITIONS The subsoils found in the borings generally consisted of sandy clay overlying clayey sand and gravel to the total depth drilled of 30 feet. Three feet of embankment fill was encountered in TH -2. TH -1 was drilled adjacent to the embankment where we encountered 7 feet of sandy clay. The test pits from our previous work also encountered sandy clay at the ground surface underlain by clayey gravel and sand. Refusal due to rocks occurred in TH -1 at 17 feet. We encountered groundwater in TH -2 at 25 feet. The clay was very stiff and very sandy. Three samples obtained during drilling contained 52 to 58 percent silt and clay -size particles (passing the No. 200 sieve). Four samples contained from 3 to 33 percent gravel in our gradation analysis and from 23 to 58 percent silt and clay -size particles (passing the No. 200 sieve). The particle size in these samples was limited by the sampling barrel (1.935 inch I.D.). The gravel was medium dense and very clayey and sandy with thin layers of sand and /or clay. Based upon the material observed in the stockpile, there are also cobbles within the gravel deposits. We were not able to sample the cobbles in our borings due to the size of the sampling barrel. Sampling of the stockpile involved random grab samples as shown in Picture 4. Sampling included gravel and cobbles from the stockpile. The samples may not be fully representative of the larger sized material (cobbles) in the stockpile or natural ground. REGULATIONS The Colorado Mined Land Reclamation Board administers the rules and regulations that govern tailings pond embankments. Rule 6.5 of the "Hard Rock, Metal, and Designated Mining Operations" dated September 30, 2010 provides the geotechnical requirements an Applicant must meet for a permit. There are several provisions in this rule that this letter addresses. • an Applicant shall be required to provide a geotechnical evaluation of all geologic hazards that have the potential to affect any proposed impoundment, slope, embankment, highwall or waste pile in the affected area. o We have not identified any geologic hazard that would preclude the development of the tailings pond as designed for the Union Mill. • an Applicant shall be required to provide engineering stability analysis for proposed final reclaimed slopes, highwalls, waste piles, embankments, and ore leach facilities. o We have performed stability analysis for the proposed embankment and planned tailings configuration. We find that a factor of safety of 2.3 or greater applies to the proposed design. THE UNION MILLING COMPANY TAILINGS POND EMBANKMENT AND FUTURE TAILINGS SLOPE UNION MILL CTL T PROJECT NO. DN45,584 -130 S:\PROJECTS 45500 \DN45584.000 \130\3. Lettere\L1 \DN45584- 130- L1.doc 5