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I I I I I I I I I I I I I I I I I I I Geotechnical Engineering Investigation Representative soil samples were obtained from the exploratory borings at selected depths appropriate to the soil investigation. Soil samples were obtained using the 2-inch a.D. split- spoon sampler. All samples were transmitted to our laboratory for evaluation and appropriate testing. Resistance blow counts were obtained with the samplers by dropping a 140-pound hammer through a 30-inch free fall. The sampler was driven 18 inches, or a shorter distance where hard resistance was encountered, and the number of blows were recorded for each 6 inches of penetration. The blows per foot recorded on the boring logs represent the accumulated number of blows that were required to drive the last 12 inches, or the number of inches indicated where hard resistance was encountered. These blow counts are the standard penetration resistance values. The following tables provide a generic correlation between consistency and blow counts, i.e.: SPT "N" values, for various material types. Sand & Gravel Blows per Foot Slit & Clay BlOWs per fOOt Very Loose 0-4 Very Soft 0-2 Loose 4 -10 Soft 2-4 Medium Dense 10 - 30 Firm 4-8 Dense 30 - 50 Stiff 8 - 16 Very Dense Over 50 Very Stiff 16 - 32 Hard Over 32 Rock core was classified according to the method outlined in Bieniawski (1984). Rock Quality Designation (RQD) was obtained for each core run. RQD is a quantitative index incorporating the measurement of sound core pieces 4-inches (100 mm) or greater in length relative to the entire length of the core run, expressed as a percentage. Percent core recovery was also measured for each core sample. R D(%) < 25 25 - 50 50 - 70 70 - 90 90 -100 Fair Good Excellent Continental Dam Page 7