Laserfiche WebLink
CPT Investigation Work Plan <br /> BP Oil Site No 11193 <br /> C A M B R 1 A Stockton, California <br /> August 12, 1999 <br /> During recent tank and piping replacement activities, more than 1,000 tons of soil were excavated <br /> from the tank pit and the piping runs, and approximately 15,000 gallons of water were extracted from <br /> the tank pit(see Figure 2) Well MW-1,located immediately south of the tanks, was destroyed during <br /> replacement activities <br /> Site Hydrogeology The soil beneath the site consists of silt, clayey silt and/or silty clay to <br /> 5-10 feet bgs which is underlain by silty sand/sand to the total depth explored of 35 feet bgs (see <br /> Appendix A) Beneath the northern portion of the site, a 5-foot thick clayey silt/sandy silt interval has <br /> been encountered within the silty sand/sand interval <br /> As shown on the graph below, water levels have risen 8 to 10 feet since 1992 On January 19, 1999, <br /> groundwater was encountered at 11 to 14 feet bgs and the groundwater flow direction ranged from <br /> northeasterly to southwesterly This broad range of groundwater flow directions has been shown using <br /> wells screening similar intervals and soil types during previous groundwater monitoring events Rose <br /> diagrams constructed using one average groundwater flow direction for each monitoring event would <br /> oversimplify site conditions and may not be representative of the aggregate groundwater flow direction <br /> at the site <br /> Slug tests performed on wells MW-1, MW-2 and MW-5 indicate that the hydraulic conductivity <br /> ranges from 8 68 x 10 5 to 4 48 x 104 centimeters per second (cm/sec) with an average of <br /> 2 53 x 10 4 cm/sec (see Appendix A) Based on this average value, a typical hydraulic gradient of <br /> 0 007, an effective porosity of 0 3, and using the appropriate unit conversions, a groundwater flow <br /> velocity of 6 0 feet per year is calculated using the relationship shown below <br /> v =kiln <br /> where v=groundwater flow velocity <br /> k=hydraulic conductivity <br /> i =hydraulic gradient <br /> n =effective porosity <br /> 2 <br />