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were the The detection limits used for the projectection limits can now be now by ts used in 1988. It is true that in 1994 lower the analytical laboratories. Even if constituents were reported below the 1988 detection levels, it is unlikely that additional assessment would be warranted since the he11998 detection limits were higherleanulevels are generally ufficie tato evaluate the 1988 detection levels. constituents and areas of concern. As underground storage tanks are uncovered, there is typically surface and shallow petroleum hydrocarbons staining and odors around the top of the tanks. This is normally associated with tank management practices and overspill. Because of the typical surface staining, guidelines recommend that samples be collected from the native soil beneath the tanks to assess the presence of contamination. 2. Comment: Oil/Water Separator On October 7, 1988, the City of Stockton uncovered another UST and requested a PHSIEHD inspector to be on site to witness soil sampling. The soil sample collected (#16964) at 8.5 feet below ground surface (bgs) indicated elevated levels of xylene (0.34 ppm) and lead (43 ppm). Response: Xylenes were detected just above the laboratory reporting limit of 0.1 mg/kg. This result is elevated in that xylenes are not naturally occurring in the soil. The fact that TPH, benzene, toluene and ethylbenzene were not detected and that the xylenes were detected just above the laboratory reporting limit indicated that the soil had not been sufficiently impacted to be a concern. Total lead was detected in the sample below the Total Threshold Limit Concentration (TTLC) and below 10 times the Soluble Threshold Limit Concentration (STLC). Lead was detected at a concentration that could be naturally occurring or considered background. A sample was collected from the sediment/oil sludge at the bottom of the sump. Petroleum hydrocarbons were detected in the sample, but xylenes and lead were not detected in the sample. 3. Comment: Tank##3 On October 31, 1988, one 500 gallon UST was removed and sampled under PHS/EHD inspection. The soil sample (#18149) was collected at 9 feet bgs and no contamination was detected; however, slightly higher than normal detection limits were used. Response: The detection limits used were standard for 1988, and are acceptable for evaluation areas and constituents of concern. GL344(1994) Page 3 of 5 June 1, 1994 Copyright 1994 Kleinfelder, Inc. L,LEI\FEL1)ER 2240 i'arkway, Santa Kos,), CA 95407 1707) 571_188; GL3-44(1994) Page 4 of 5 June 1, 1994 Copyright 1994 Kleinfelder, Inc. +,LEINFFI DER ??1(} Vnrihlxiint I',)rk��,)v, tianla Rntia. C 1 U�•1U.' i'f)-i ;'I-li;ts;