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F <br /> r <br /> r <br /> IMM <br /> as. <br /> HArding Lawson Associates <br /> This alternative appears <br /> ' PP appropriate to the size of the <br /> site and to the small volume of ground water expected to be col- <br /> lected. This disposal method would not only remove the need for <br /> 1.4 <br /> on-site treatment, but would allow a pick-up schedule compatible <br /> with the rate of <br /> ground-water withdrawal. T"is <br /> alternative will <br /> be further considered. <br /> i_ <br /> $. Remedial Alternatives - Soils <br /> Primarily because of the very shallow.grnund water at the <br /> site, theotential of <br /> 1 <br /> p gasoline hydrocarbons to leach from soil <br /> '-� to water is considered very high.g As discussed in .the Problem <br /> f� Assessment Report, however, HLA believes that the physical char-. <br /> •� acteristics. of the site and ground water zone will help restr <br /> ict <br /> the movenent of hydrocarbons in the soil. Sail containing F. g gasp-line hydrocarbons is no shallower than 4feet below <br /> i grade and is <br /> overlain by asphalt and concrete. Thus contami <br /> ; isolated from. direct human contact a Hated soil is { <br /> and from surface water runoff. <br /> The selected ground-water treatment system will intercept an <br /> R. y <br /> { hydrocarbons that leach into the shallow.ground water. <br /> . water.. <br /> There- <br /> leve <br /> fore, we bel .that.higher- ccncentratlon �s of hydrocarbons <br /> .. <br /> ca <br /> be left in the soil than would be otherwise <br /> n <br /> t rwse acceptable. Accord- <br /> =t: i ingly, the following soil clean-up levels will be targeted: <br /> Benzene . . . <br /> (Yy : . . . ..1.0 ppm <br /> Toluene. . . • <br /> + #� . . . . . . . .50.0 ppm <br /> Ethylbenzene. . . . . . . . . <br /> . • . . . . .50 <br /> •0 ppm <br /> Total xylenes. . . . . . . . . . <br /> ...50.0 ppm <br /> Total petrole1m hydrocarbons. . .lOpO .ppm <br /> z <br /> 13 <br /> �r <br /> -h. <br />