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Geological Technics In ``' Page 2 <br /> Former Moresco Property <br /> Soil Boring Report <br /> Project No.251.2 <br /> May 12, 1995 <br /> �I I <br /> 2.0 SUBSURFACE INVESTIGATION%: <br /> A series of soil borings were advanced through and surrounding the former tank <br /> excavation to provide a better understanding of the site's vadose zone how its <br /> geology may have affected the transport of petroleum hydrocarbons and its <br /> attenuation processes. Soil samples were' analyzed to evaluate the vertical and <br /> horizontal extent of the contamination. <br /> .1 Soil Boring Installation <br /> On April 5 - 7, 1995 well drilling company Osterberg & Stewart Inc. of Modesto <br /> mobilized drilling equipment to the site. Hollow stem auger drilling methods <br /> and wire line sampling equipment were utilized for. this investigation. <br /> Geological Technics Inc. personnel supervised the drilling offour soil borings: <br /> SB-1 was advanced to a depth of 60 feetbgs through the former UST excavation <br /> (Figure 2). SB-2, located approximately 30 feet west of the former UST, was <br /> advanced to a depth of 50 feet bgs, SB-3, located approximately 20 feet south of the <br /> former e UST, was advanced to a depth of s50 feet.bgs, SB-4, located approximately <br /> 20 feet north,of the former UST, was advar ed to a depth of 100 feet bgs. <br /> After a review of laboratory data from 'the April 5-7, 1995 investigation it was <br /> evident that further definition was needed below 60 feet beneath the former UST i <br /> location. On April 21, 1995 soil boring SB-1A was advanced to a depth of 100 feet <br /> bgs through the former UST excavation to further evaluate the vertical extent <br /> r beneath the point of release and to gauge ..tle potential for groundwater impact. <br /> During drilling, soil samples were collected for geological and analytical <br /> evaluation at 5 foot intervals starting at five feet below ground surface to the <br /> total depth of each boring. In SB-1, "h 6wever, soil samples were collected <br /> beginning at 18 feet below grade (beneath the UST removal excavation). Soil <br /> samples for laboratory analyses were collected in brass liners using a 2.0 inch <br /> modified California split spoon sampler. All soil samples were sealed with <br /> aluminum foil, capped, labeled and placed in a cooler at 4° Celsius for transport <br /> Lto the laboratory following Chain of Custody protocol. <br /> 2.2 Field Screening Methods <br /> Because every soil sample collected was' not selected for laboratory analysis, a <br /> screening process was used to gather additional information through field <br /> observation noting sediment type, es.pe,cially grain size and clay content, <br /> moisture content, visible evidence of contamination, i.e., color change due to <br /> r reduction of iron or discoloration from hydrocarbons and other pollutants, and <br /> L <br />