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respectively) are also constituents historically associated with <br />manufactured gas plant processes and the breakdown of gas plant wastes. <br />As these compounds have not been detected at other similar PG&E sites, 108 <br />of the soil samples of the highest apparent residue concentration will be <br />analyzed for sulfides and cyanides. <br />4.3.2 Analvze_the chemical composition of groundwater samples <br />' collected from the six existing and four proposed monitoring wells <br />A single set of groundwater samples will be collected from the six existing <br />and four proposed monitoring wells at the Tracy site and analyzed for PNAs <br />(EPA method 610), BTEX (modified EPA Method 602), phenols (EPA Method 604), <br />CAM metals (EPA Method 6010), cyanides (EPA Method 9010), sulfides (Standard <br />Method 426A), and general minerals. <br />PNAs may occur in groundwater by the leaching of gas plant residues through <br />the soils to the groundwater, although most PNA compounds are stationary in <br />soil (due to their large molecular size). <br />1 3542a/BAV102 21 <br />have been the source of residual BTEX in the soil and groundwater <br />surrounding the former tank location. It is likely that any elevated <br />concentrations of BTEX.detected during this investigation in this area are <br />related to the former underground tank and not gas plant residues. <br />Metal oxides have been associated with gas manufacturing residues. <br />However, previous investigations at similar PG&E sites have indicated that <br />manufactured gas plant processes have not significantly contributed to metal <br />concentrations in soils. Therefore, metals analyses will be performed <br />on 108 of the "worst case" samples chosen for PNA and BTEX analysis (see <br />Section 4.2.1 for a description of "worst case" samples). This 108 sample <br />selection process will provide a representative cross-section of metal <br />concentrations in the soil, while avoiding unnecessary analytical costs. <br />The include <br />metal analysis will the quantification of antimony, arsenic, <br />cadmium, chromium, cobalt, copper, lead, nickel, vanadium, and zinc. <br />Sulfides and cyanides (Standard Methods 426A and EPA Method 9010, <br />respectively) are also constituents historically associated with <br />manufactured gas plant processes and the breakdown of gas plant wastes. <br />As these compounds have not been detected at other similar PG&E sites, 108 <br />of the soil samples of the highest apparent residue concentration will be <br />analyzed for sulfides and cyanides. <br />4.3.2 Analvze_the chemical composition of groundwater samples <br />' collected from the six existing and four proposed monitoring wells <br />A single set of groundwater samples will be collected from the six existing <br />and four proposed monitoring wells at the Tracy site and analyzed for PNAs <br />(EPA method 610), BTEX (modified EPA Method 602), phenols (EPA Method 604), <br />CAM metals (EPA Method 6010), cyanides (EPA Method 9010), sulfides (Standard <br />Method 426A), and general minerals. <br />PNAs may occur in groundwater by the leaching of gas plant residues through <br />the soils to the groundwater, although most PNA compounds are stationary in <br />soil (due to their large molecular size). <br />1 3542a/BAV102 21 <br />