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INTRODUCTION Jake Kauffman & Son, Inc. proposes to construct a water storage reservoir from a sand and gravel pit known as the Wagner/Kauffinan Pit #3. The site is located in Larimer County, Colorado adjacent to Larimer County Road 9E and also adjacent [o [he Kauffrnan Pit (Permit No. M-78-327) and the Stroh Pi[ (Permit No. M-85-216). The proposed mining operation will extract gravel reserves from the property in some locations that are adjacent to man-made structures. The rules and regulations of the Division of Minerals and Geology require that any mining within a 200 foot setback of a man-made structure show through engineering analysis that the proposed mining will not cause damage. The accepted method of demonstrating this is through a slope stability analysis. This report contains a stability analysis of the mining highwall and the ~) `mbankment that is proposed for lining the reservoir. The report also provides a general overview of the reservoir, the proposed embankment design, geotechnical results, and methodology, and conclusions and recommendations for construction of the reservoir. OVERVIEW The Division of Minerals and Geology Mining Plan, Exhibit C, proposes that the property be mined in 3 phases. The reclamation plan, Exhibits E and F, proposes future use as pastureland and a water storage reservoir. Concurrent reclamation is planned in that the reservoir lining will be constructed as the mining progresses. The total affected area for the reservoir is approximately 28 acres. The proposed reservoir will be constructed in the Valley Fill Aquifer of the Big Thompson River drainage. This a shallow alluvium stratum that varies in thickness up to a depth of approximately 16' for the proposed site. Underlying the alluvium is a relatively impermeable layer ofblue/gray siltstone/claystone, called the Pierre Formation. This formation is very thick and can have the top few feet removed for construction without compromising the integrity of [he formation. The adjacent pits, Stroh Pit (M-85- 216), Kauffman Pit (M-78-327) and Kauffman Pit #2 (M-93-024), shows that weathered bedrock (siltstone/claystone) was encountered at depths ranging from 11.5 feet to I S feet surrounding the site. This will serve as the foundation of the reservoir and will also provide some material for embankment construction. GEOTECHNICAL TESTING This report did not do site specific testing of the material for strength properties. Typical values that have been reviewed and approved in previous submittals were used in the slope stability analysis. Soil strength properties were estimated based on typical values for similar materials in this region. Table 1 represents a summary of [he results that were used in the stability analysis.