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Ms. Angela Bellantoni Hard Rock Paving i~ Redi-Mix, Inc. June 14, 1999 Page 2 Ground water was not observed at the site at the time our field reconnaissance. At this location, we estimate the groundwater level to be near an elevation of 8000 feet. Mining at the site proposes to remove the outwash deposits using conventional heavy equipment and crush and sort the materials for use as aggregates for concrete, asphalt and road base. The material is to removed to an approximate elevation of 8020 feet in the bottom of the pit. The maximum natural ground surface elevation is approximately 8070 in the northeast corner of the site and the minimum is approximately 8040 in the southeast corner of the pit. The pit excavation will therefore have a minimum depth of 20 feet and a maximum depth of 50 feet, relative to the natural ground surface. Pit faces are typically as steep as feasible during the active mining phase and the reclamation plan calls for maximum slopes of 2 horizontal to 1 vertical. Mining and reclamation are to proceed across the site from west io east. Based on our field observations the outwash deposits to be mined are well graded. Well graded deposits contain a full range of particle sizes from sand to large boulders. This wide range of particle size results in deposits which are stable at steep to very steep angles. This was demonstrated by the near vertical slopes observed on the site. For the purposes of assessing the stability of mined and reclaimed slopes, we conservatively estimated these materials have an angle of internal friction of 35 degrees. The fan alluvium deposits are similar to the outwash deposits with regard to stability due to the angular nature of the materials. The smaller grain size will make these deposits more susceptible to erosion. Due to the free draining nature of the deposits at the site, ground water (if encountered) will have little effect on the stability of slopes. The stability of the gravel pit was assessed using cross-sections of the areas derived from information provided on the reclamation map provided in the 112 conversion application. The cross-sections used in the stability analyses are shown on the attached Figure 1. Our stability analysis indicated that temporary, near vertical slopes may be stable for short periods of time. The analysis also showed that in a worst case situation, where temporary pit slopes were made to fail, the failures did not affect the stability of either the railroad facilities or the residences to the west of the property. Reclaimed slopes graded to an angle of 2:1 (H:V) will be stable and present no hazard to adjacent properties provided excessive erosion does not occur. Crushing of aggregates in the pit may create vibrations which could potentially be felt on the adjacent properties. The outwash and fan deposits will tend to absorb the energy of the crushing activities. In our opinion crushing activities will not result in damage to adjacent properties. Placing the crusher on the north and east portions of the pit, away from occupied buildings, will further reduce the potential for vibrations to be felt outside the limits of the pit. To summarize, our observations and analysis indicate the gravel mining operations, as outlined in the 112 conversion application, will not result in damage to Union Pacific Railroad Facilities or to the Koehler Property adjacent to the Buena Vista Pit.