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r rGREGG IN SITU, INC. ADVANCED GEO December 5, 2002 Den's Auto Repair I01-169ma Stockton, Ca In situ groundwater samples were taken at three locations Groundwater samples were collected using a Hydropunch® 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 bailer 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 9 ) p were collected in approximately 1 118 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 referenced to existing ground surface This data includes CPT logs of measured soil parameters and a computer tabulation of interpreted soil types along with additional Igeotechnical parameters and pore pressure dissipation data 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 soils (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 measure hydrostatic water pressures and approximate depth to groundwater table In addition, the PPDT data can be used to estimate the horizontal permeability (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 (too) The PPDT correlation figure (figure 4) is provided in the Appendix The interpretation of soils encountered on this project was carried out using recent correlations developed by Robertson et al, 1990 It should be noted that it is not always 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 sal classification chart (figure 5) used to interpret soil types based on qc and Rf is provided in the Appendix