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Geotechnical Engineering Report <br />Sand and Gravel Study <br />Terracon Project No. 21085006 <br />Terracon <br />present stream courses with stream deposits consisting of coarse and fine aggregate resources. <br />This is consistent with the materials encountered in our borings. <br />Mapping performed by the USGS (3Trimble and Fitch, 1974) adjacent to the project site <br />indicates that the site likely contains a gravel deposit underlying flood plains and terraces. The <br />materials are described as pebbles and casts generally well rounded, unweathered, and <br />contain little deleterious "lime" (CaG03). Clasts are composed chiefly of quartzite, granite, <br />gneiss, and pegmatite. The material contains few or no reactive constituents and is a source of <br />quality gravel for concrete and aggregate and road metal. Thicknesses of the deposits mapped <br />close to the area range from approximately 16 to 28 feet in thickness. Based on the materials <br />encountered in our borings, it is likely that commercially extractable mineral deposits are located <br />on the project site. <br />Due to the relatively flat nature of the site, geologic hazards at the site are anticipated to be low. <br />Seismic activity in the area is anticipated to be low, and the property should be relatively stable <br />from a structural standpoint. With proper site grading around the proposed mine, erosional <br />problems at the site should be reduced. <br />Soil Conditions: As presented on the Logs of Boring, surface soils consisted of about 6 inches <br />of topsoil and about 3 feet of clayey sand. The overburden materials underlying the surface <br />soils and extending to depths of 50 to 57 feet consisted of cobbles, gravel, and sand with <br />varying amounts of silt and clay. <br />Field and Laboratory Test Results: The classifications included in Appendix B indicate the <br />overburden materials generally classify as gravels and sands with varying amounts of silt. <br />These classifications were performed on the bulk samples which were returned in the cutting <br />funnel during drilling activities. <br />Gravels encountered ranged from 3/e-inch diameter to 4-inch diameter. Percentages of size <br />distribution are presented-in the laboratory test results in Appendix B. <br />Groundwater Conditions: Groundwater was encountered at depths of about 4 to 8 feet below <br />existing site grade in the test borings at the time of field exploration. These observations <br />represent groundwater conditions at the time of the field exploration, and may not be indicative <br />Trimble, Donald E., and Fitch, Harold R., 1974, Map Showing Potential Sources of Gravel and Crushed Rock <br />Aggregate In the Boulder Fort Collins-Greeley Area, Front Range Urban Corridor, Colorado, United States Geological <br />Survey, Map 1-655-D, <br />3