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Brighton Water Storage Project ' Slope Stability Calcularioas Adams County, Colorado ' Subsurface Exploration and Laboratory Testin Field exploration for the project was conducted in April, 2002. Eight test holes were drilled at the ' approximate locations indicated on Figure 1, with atruck-mounted, continuous flight, hollow- - stem, power auger rig to evaluate subsurface conditions and to retrieve samples for laboratory I, testing and analysis. AGROUND engineer directed subsurface exploration, logged the test holes in the field'and prepared the samples for transport to our laboratory. ' Samples of the subsurface materials were retrieved with a 2-inch LD. "California",-type liner sampler and a 1 -inch LD. Standard Penetration sampler. The samplers were driven into the ' substrata with blows frbm a 140-pound hammer falling approximately ~30 inches in general accordance (for the Standard Penetration sampler) with ASTM Method D-1586. Penetration resistance values (reported, as blows per distance driven, typically 12 inches), when properly . ,evaluated, indicate the relative density or consistency of soils and bedrock. Depths at which the _ samples were obtained, and associated penetration resistance values, are shown on the test hole logs..-place densities and moisture contents for the shallow soils also were determined in the' field by means of "sand cone" tests performed in general accordance with ASTM D-1556. Samples retrieved from our test holes were examined acid visually classified in the laboratory by the project engineer;' Laboratory testing of soil samples obtained from the subject site included standard property tests, such as natural moisture contents, dry unit weights, grain size analyses and liquid and plastic limits. Laboratory tests were' performed in general accordance with applicable ASTM specifications. A composite sample of claystone was submitted to an " independent analytical testing laboratory for hydraulic conductivity and direct shear strength testing. The latter tests were performed on material re-compacted to approximately 95 percent of the maximum "standard Proctor" dry density (ASTM D-698) to model that material placed as compacted fill forming the reservoir liner. Logs of the exploratory test holes are presented on Figures 2 and 3. Explanatory notes and a legend are provided on Figure 4. The laboratory test data are summarized in Table 1. Subsurface Conditions' In_general, the project site occupies a portion of a stream terrace overlooking the South Platte River floodplain to the west. The site vicinity is underlain by deposits of sands and gravels interpreted to be Broadway Alluvium as depicted on published maps such as Trimble and ' ~ Job No. 02-0065 ~ - Ground Engineering Consultants, Inc ~ . ~ Page 3