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1444 MARIPOSA <br /> WKA No 2307 02 <br /> May 24, 1993 <br /> ' Page 2 <br /> ' center of the excavation to a depth of approximately 44 feet below grade Because further <br /> excavation would require sloping of the side walls, the decision was made to drill exploratory soil <br /> borings to further evaluate the vertical and lateral extent of hydrocarbon contamination <br /> FIELD INVESTIGATION METHODOLOGY <br /> Soil! Boring Construction and Samplin <br /> ' The soil borings were drilled with a truck-mounted Mobile B-53 drill rig supplied by B & F <br /> Drilling and equipped with hollow-stem augers Soil samples were collected from each boring at <br /> ' five-foot maximum intervals with a modified California sampler equipped with clean, two-inch <br /> diameter, six-inch long brass tubes, samples and drill cuttings were described in the field by an <br /> experienced geologist or engineer from our firm using the Unified Soil Classification System <br /> (USCS) Logs describing the soils encountered in each boring are presented on Plates 3 <br /> ' through 14 <br /> Sample tubes were sealed with polytetrafluoroethylene (PTFE)-coated sheets, plastic end caps and <br /> ' duct tape to reduce volatile hydrocarbon loss The samples were screened in the field with an <br /> organic vapor analyzer (OVA) to evaluate potential hydrocarbon content Selected samples were <br /> ' placed in an ice chest containing ice, and submitted under chain-of-custody to a California- <br /> certified laboratory for analysis of Total Petroleum Hydrocarbons as gasoline (TPHg) using <br /> ' Modified EPA method 8015/Purge-and-Trap, Benzene, Toluene, Ethylbenzene, and Total Xylenes <br /> (BTEXO, using EPA method 8020/Purge-and-Trap <br /> ' Soil borings were sealed to the surface by pumping a slurry of Portland Cement and bentonite <br /> ' into each boring through a tremie pipe Soil generated during drilling activities was placed on <br /> the existing soil stockpiles generated during the removal operations Drilling equipment was <br /> steam cleaned between borings, steam cleaning ansate was contained in the steam cleaning <br /> rack/collection system, transferred to sealed 55-gallon drums and stored on site <br /> 1 � <br /> WALLACE•KUHL <br /> Pat- $ASSOCIATES INC <br /> Rerycted <br />