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ADDITIONAL ASSESSMENT WORKPLAN <br /> JAMAR SERVICE, STOCKTON <br /> APRIL 2002 <br /> In addition,the sensitive receptor survey will include data collection of the surrounding <br /> population,water quality and use, subsurface soil conditions and hydrology, locations of <br /> subsurface utilities and other preferential pathways,climatological conditions, and ecological <br /> receptors <br /> Monitoring Well Installation <br /> Based on the data collected from the CPT borings,present distribution of petroleum <br /> hydrocarbons and MTBE in on-site groundwater monitoring wells and the groundwater flow <br /> patterns determined from quarterly groundwater monitoring at the site, GHH will propose two or <br /> three off-site locations to mstall additional groundwater monitoring wells The new wells will be <br /> used to monitor the vertical and horizontal extent of impacted groundwater off-site The new <br /> wells will also provide further information on the gradient and direction of groundwater flow <br /> Dnlhng and well installation activities will be reviewed by a California Registered Geologist or <br /> Licensed Civil Engineer <br /> Drilling will be performed by hollow-stem auger drilling techniques using a truck-mounted drill <br /> rig equipped with 8-inch outside diameter hollow-stem augers Prior to drilling, augers and <br /> associated drilling and soil sampling equipment will be cleaned with a high pressure hot water <br /> washer To mmu nine the possibility of cross contamination, the sampling equipment will be <br /> washed and rinsed with distilled water before collecting each soil sample Drilling and sampling <br /> will be performed according to ASTM Method D 1452-80,Soil Investigation and Sampling by <br /> Auger Barings as described herein <br /> Soil samples will be collected at 5-foot intervals for classification by the Unified Soil <br /> Classification System(USCS), field screening and for possible chemical analysis Soil samples <br /> will be collected by placing the augers above the desired sampling depth and then driving a <br /> modified California split-spoon sampler lined with three brass tubes into the undisturbed soil <br /> The sampler will be driven by a 140-pound hammer with a 30-mch drop according to ASTM <br /> Methods D 1586-84 Split Barrel Sampling in Soil and the resulting blow counts will be recorded <br /> in 6-inch intervals after every sampling event The middle of the three brass tubes in the sampler <br /> will be selected for submittal to the laboratory for analysis To preserve the sample, the liners at <br /> each end will be sealed using Teflon sheeting secured by tight fitting plastic caps The samples <br /> will be stored in a chilled cooler at 4 degrees Centigrade for transport to a California State <br /> certified laboratory for analysis <br /> To provide a preliminary indication of the presence of petroleum hydrocarbons, a portable <br /> organic vapor detector wall be used to monitor for the presence of organic vapors in soil collected <br /> from the borings <br />