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J, H. KLEINFELDER &ASSOCIATES <br /> A liquid phase leak occurring in the vicinity of B-15 from the product <br /> x'414 lines around the pump islands is indicated by an examination Figures 36 <br /> through 39. ' If lateral migration had occurred from B-8 moving towards <br /> B-13 then high concentration of contaminants should be found at similar <br /> depths in B-10 and B-13, given the similar lithologies found in these <br /> borings (Appendix C). Higher concentrations are found below 20 feet in <br /> B-10, but above 20 feet in B-13. No corresponding high contaminants exist <br /> at these two levels in E-2, which is situated between B-10 and B-13. <br /> These conditions would tend to suggest that contamination in B-13 <br /> originated from a source different from that of B-10, probably near B-15, <br /> , <br /> or south of 8--13. <br /> i <br /> The clayey layer in B--2 between 15 and 25 feet appears to have prevented <br /> any contamination .from moving through this strata, while the sandy layers <br /> below appear to have provided a pathway for migration of the contamination <br /> below 25 feet. The higher concentration of the lighter constituents <br /> (xylene) appear to have separated from the heavier constituents (toluene), <br /> occupying the upper part of the 25 to 40 foot zone in B-2 (Iso-Chem, <br /> Figures 36 through 39, Table 2). <br /> Hear surface contamination at B-15 may also have been caused by spillage j <br /> k <br /> of product during fueling of vehicles over along period of time. B-15 s <br /> appears to be situated between the pump islands where fueling of vehicles <br /> i <br /> took place. This could account for the lower concentration contamination <br /> found between 3 and 10 feet (Table 2). The lower concentration of toluene ; <br /> of contamination <br /> between 25 and 30 feet is probably from lateral migration i <br /> t <br /> } from B-2 through B-13. The strata at the 25- to 30-foot depth in B-2, <br /> B-13, and B-15 is a sand similar to the highly permeable sand at the same <br /> i <br /> depth in B-11. The high permeability would allow lateral movement of the <br /> gas of contamination from B-2 towards B-15, or from some point between <br /> .;'. <br /> B-15 and B-2. <br /> An estimate of the volume of soil containing various concentrations of ' <br /> i <br /> total petroleum hydrocarbons (Table 9) was derived based on the areal and ; <br /> vertical distribution of TPH concentrations at different poring locations <br /> and depths. Given the heterogeneity of the subsurface sediment (Figure <br /> 53-87-443 25 <br />