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. TABLE 2. GROUNDWATER CHEMICAL DATA Sample TPHG Benzene Toluene Ethylbenzene Xylene No -------------------------------ug/l --------------------------------- PB-1, 8-12@ 230 ND ND 2 2 3 5 PB-2, 8-12 ND ND ND ND 054 PB-3, 8-12 ND ND ND ND ND PB-4, 8-12 130,000 98 390 2,900 5,600 PB-5, 8-12 ND ND ND ND 1 3 PB-6, 8-12 ND ND ND ND ND - PB-7, 8-12 130,000 110 540 340 380 PB-8, 8-12 1,900,000 780 7,400 64,000 74,000 PB-9, 8-12* ND ND ND ND ND ND - Not Detected * - Analyzed by Pnonty Laboratory TOC - Total Organic Carbon NA - Not Analyzed mg/kg - milligram per kilogram ug/kg - microgram per kilogram ug/I - microgram per liter PB - Push Boring TP - Former Tank Pit Area @ - Monroe Lab reports that the component peaks do not resemble typical gasoline ranges Discussion The contaminants appear to have migrated in a northerly direction from the former tank pit . area, with some northeasterly movement at PB-7 (see Figures 1 , 2, 3) Field evidence ti indicates that the migration in the aquifer has occurred along or dust below the capillary fringe A dissolved plume has moved to the north and crossed the Tracy High School property line, the downgradient edge of which has been defined at P13-5 A subsurface irrigation line occurs on both the Tracy High and Cox properties and may have influenced the plume migration to the north, somewhat parallel to the pipeline course Borings PB-1 and P13-2 on the adjacent Heinz property revealed trace levels of contaminants, although the laboratory data indicates that the pattern did not match gasoline at P13-1 The northeastern plume edge is interpreted to be under the railroad alignment between the Heinz and Cox properties (see Figure 3) The most elevated TPHG and BTEX concentrations occurred at P13-8, roughly in the center of the site This would support a relatively slow northerly movement Again, these concentrations indicate highly degraded volatile components in the gasoline product, with concentrations declining one order of magnitude north between P13-8 and P13-7 Chemical analysis of TOC indicates that roughly 0 049% of TQC occurs in the aquifer, some of which may be related to hydrocarbons since the TOC test does not discriminate between indigenous carbon and possible hydrocarbon input The low TOC value is consistent with young (10,000-100,000 years before present) semi-arid alluvial deposits and environments which contain only traces of organic carbon due to geologic degradation processes (Hunt, 1972 pp 278-279) A calculation for a retardation factor is not considered feasible for this data since 0 049% TOC falls below the 3% TOC (total in soil) threshold value considered necessary for valid retardation computations (Dragun, 1988, pp 242-251) .� Mr Ed's Muffler Project No 4090-P Page 5