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1 <br /> R10/71-51-1C <br /> 5.0 INVESTIGATIVE RESULTS AND FIELD OBSERVATION <br />' 51 FIELD MONITORING <br /> Field monitoring using a Foxboro OVA was conducted mainly for worker safety <br /> considerations All readings of the drilling area breathing zone had registered a zero <br /> ppm Readings of selected soil sample taken from the brass sleeves varied from zero to <br />' greater than 1,000 ppm (See borehole logs, Appendix D) <br /> ' 52 LABORATORY ANALYTICAL-RESULTS <br /> Results of the laboratory analyses of the soil and groundwater samples are included in <br />' Appendix G Table 8 (see Appendix C) presents a summary of water sample analytical <br /> results Tables 10A through 10P (see Appendix C) presents summaries of sod sample <br /> analytical results Table 11 presents a summary of analyses on water samples collected <br /> ' from soil borings that were not converted into monitoring wells <br /> 5 2 1 Sods <br /> Tables 10A through 10P tabulate analytical results on soil samples at each sampling <br /> ' horizon Figures 12 through 25 (see Appendix J), present zero concentration of maps <br /> for benzene, toluene, and xylenes at horizons from 5 feet to 70 feet, the approximate <br /> depth where groundwater was encountered Soil samples were initially collected at depth <br /> ' of 1 25 or 1 5 feet below grade and then at every five feet below grade thereafter In <br /> general, the following sampling locations have non-detectable to low levels of gasoline- <br /> derived contaminants including benzene, toluene and xylenes S1315, MW16, S1318, <br /> MW19, MW20, S1322, SB23 and MW24 The following sampling locations have varying <br /> levels of gasoline-derived contaminants at different horizons MW13, MW14, and SB17 <br /> These latter locations are around the gravel area where underground tanks were removed <br /> ' in the past <br /> Moderate levels of gasoline-derived contaminants are found in MW13 from approximately <br /> ' 35 feet to 55 feet below the surface <br /> In MW14, the concentration of contaminants appear to increase going down from dust <br /> ' beneath the surface, maximizing between 25 to 40 feet below grade, and then at <br /> decreased levels down to 70 feet below grade <br /> 16 <br />