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r n'�I�lAA�-lFRAfA will be drilled vertically aruund the excavation to e•.,a:uate the 13terai extent of petroleum hydrocarbons in the soil. The borings will be sampled at five-foot intervals and drilling will continue until at least one sample is collected beyond the deepest suspected contamination. Drilling will cease if groundwater is encountered, although information supplied by the PHS-EHD indicates that groundwater is nct expected to be encountered. Based on this procedure, the completion depths of the vertical borings are estimated at 20 feet below ground surface. After sampling of the borings is completed, the borings will be backfilled with a cement/bentonite grout. The cuttings from the borings will be placed in drums for temporary onsite storage until the results of the laboratory analyses are completed. Stockton Unified School District, being the generate-of the cuttings, will be responsible for their appropriate disposal. INVESTIGATION METHODS Drilling and Soil_Samnf� Ali drilling will be performed by hollow-stem auger drWing techniques using a truck- -or 8-inch outside diameter hollow-stem augers. mounted drill-rig equipped with either 6 The augers will be steam cleaned between each use and the drive sampler will be washed i ! with a trisodium phosphate solution to limit cross contamination between uses. , i .. . E i Drilling and sampling will be performed in accordance with ASTM Method D 1452-80, "Soil Investigation and Sampling by Auger Borings." For logging and analytical purposes, soil samples will be collected from each of the borings at five foot intervals beginning at a depth of five feet below the ground surface. Additional samples may be collected at changes in lithology and specified intervals at the discretion of the field geologist. Samples will be collected by advancing the auger to a location immediately above the desired sampling depth and then driving a modified California split-spoon sampler lined with three brass tubes into the undisturbed soil. The sampler will be driven by a 140-1b hammer with a 30-inch drop (or an automatic hammer system with an equivalent force) In accordance with ASPM Methods D 1586-84 "Split Barrel Sampling of Soil." Blow counts will be recorded in six inch Intervals after every sampfirg event. The ends of the bottom brass tube will be wrapped in Teflon sheeting or aluminum foil and capped with tight f itting plastic caps. The brass tube containing the sample will then be labelled with a unique sample number and the date and time sampled, and placed in a chilled ice chest- type cooler for preservation. The contents of the remaining brass tubes will be used to if for qualitative Field screening. Each soil sample visually describe soil characteristics and q will be classified In accordance with the Unified Soil Classification System as described in the ASTM Standard D 2488-84"Description.and Identification of Soils (Visual-Manual ;,. A - 2