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y 3 <br /> 16 September 1997 <br /> AGE-NC PI <br /> ajet cNo95- <br /> 0134 <br />' Page 2of5 r <br /> 22 COLLECTION OF GROUND WATER SAMPLES <br /> ` Water samples were collected from each well using disposable plastic bailers The samples were <br /> transferred Into 40-m1 EPA-approved VOA vials containing 0 5 ml of 18% hydrochloric acid as a <br /> preservative and Into 1-liter amber bottles without preservative The sample containers were labeled, <br /> placed in a chilled container and transported under chain-of-custody to McCampbell Analytical, Inc <br /> (MAI) in Pacheco, California Each sample was analyzed for total petroleum hydrocarbons <br /> quantified as gasoline (TPH-g) and diesel (TPH-d) in accordance with EPA methods 5030/8015m <br /> and for volatile of ganics (benzene. toluene ethylbenzene and xylenes, BTE&X) with methyl <br /> ternary-butyl ether (MTBE) in accordance -,vitt EPA methods 602 and 8260 <br />' 2 3 REVIEW OF HISTORIC CHROMATOGRAMS <br /> Chromatograms for the March, June and September 1994 and January 1996 monitoring e-'ents we're <br /> submitted to Western Environmental Science & Technology laboratory (WEST) Chromatograms <br /> were examined for indications of the presence of MTBE WEST had performed the original analyses <br /> of these samples <br /> lie <br /> 24 MASS BALANCE CALCULATIONS <br /> The extent of impacted soil was estimated based upon soil borings and observations made during <br /> excavation procedures Impacted soil was observed between 10 to 13 feet below surface grade (bsg) <br /> along the northern wall of the excavation for the former USTs 'The highest concentrations of <br /> petioleum hydi ocai bons were observed in sample TP-3, collected from this location The average <br /> concentration of gasoline was estimated as 120 parts per million (ppm) based on soil samples from <br /> MW-1, MW-4,B-5 and the excavation,the average concentration of diesel was estimated as 25 ppm <br /> Petroleum hydrocarbons were detected in four soil samples collected from the west and north walls <br /> of the excavation fol the installation of the new USTs Hydrocarbons were limited to between 9 and <br /> 12 feet bsg The lateral extent of hydrocarbons is also limited based on samples collected from B-8 <br />' and field observations An average soil density of 1 5 grams per cubic centimeter, or 1146 kilograms <br /> per cubic yard (kg/yd') of soil, was used in the calculations Gasoline has a density of approximately <br /> 0 75, diesel has a density of approximately 0 84 The estimated lateral extent of impacted soil is <br /> illustrated on Figure 4 <br />' Advanced 6coEmironnlenIAI,Inc <br /> a <br /> 11 i M <br />