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GREGG IN SITU, INC. ADVANCED GEO October 21, 2002 1601 Turnpike Road 02-572tx Stockton, Ca In situ groundwater samples were taken at one location Groundwater samples were collected using a HydropunchO type groundwater sampling system (figure 2) The groundwater sampler operates by pushing 1 75 inch diameter hollow rods with a retrievable tip A stainless steel filter screen is attached to the tip At the desired sampling depth, the rods are retracted exposing the filter screen and allowing for groundwater infiltration A small diameter baler is then used to collect groundwater ' samples through the hollow rod Soil samples were taken using a piston type soil sampler (figure 3) The soil samples were collected in approximately 1 1/8 inch diameter stainless steel sample rings 3.0 CONE PENETRATION TEST DATA & INTERPRETATION The cone penetration test data is presented in graphical form Penetration depths are re€erenced to existing ground surface This data includes CPT logs of measured soil parameters and a computer tabulation of interpreted soil types along with additional geotechnical parameters and pore pressure dissipation data lie The stratigraphic interpretation is based on relationships between cone bearing (qc), sleeve friction (fs), and penetration pore pressure (U) The friction ratio (Rf), which is sleeve friction divided by cone bearing, is a calculated parameter which is used to infer soil behavior type Generally, cohesive soils (clays) have high friction ratios, low cone bearing and generate large excess pore water pressures Cohesionless sols (sands) have lower friction ratios, high cone bearing and generate little in the way of excess ' pore water pressures Pore Pressure Dissipation Tests (PPDT's) were taken at various intervals in order to rmeasure hydrostatic water pressures and approximate depth to groundwater table In addition, the PPDT data can be used to estimate the horizontal penneab€I€ty (kh) of the soil The correlation to permeability is based on the time required for 50 percent of the measured dynamic pore pressure to dissipate (t50) The PPDT correlation figure (figure 4) is provided in the Appendix The interpretation of soils encountered on this protect was carried out using recent correlations developed by Robertson et al, 1988 It should be noted that €# is not always 1 possible to clearly identify a soil type based on qc, fs and U In these situations, experience and judgement and an assessment of the pore pressure dissipation data should be used to infer the soil behavior type The soil classification chart (figure 5) 1 used to interpret soil types based on qc and Rf is provided in the Appendix i