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F: <br /> kr <br /> was extrapolated east every 30 feet beneath the property to the open area immediately <br /> } east of the condominium complex (see Figure 4). The same decline rate and distance <br /> were used to prepare Figure 5. <br /> On the east side of the condominium complex, an estimated 4.7 µg11 of benzene were <br /> extrapolated for July 7, 1995 across a scaled distance of 240 feet (see Figure 4). An <br /> estimated 8.2 �tg/l of benzene were extrapolated at the east side of the condominium <br /> complex for January 22, 1997 (see Figure 5). It should be noted that the report <br /> Recommendations to Improve the Cleanup Process for California's Leaking <br /> Under round Fuel Tanks (Lawrence Livermore National Laboratory, October 16, 1995, <br /> page 11) indicated that "plume concentrations greater than 10 ppb benzene extended <br /> :a. no more than about 250 feet in 90% of the cases". <br /> As established in the Problem Assessment Report (W.W. Irwin, Inc., August 8, 1995) <br /> following a review of water well files at the SJCPHS-EHD, there are no public or <br /> ' privately-operated water wells within 2,000 feet of Village West Marina. The nearest <br /> domestic production well is located at Benjamin Holt Drive and Interstate Highway 5 <br /> approximately one mile to the east. <br /> r- <br /> CONCLUSIONS <br /> Closure of this site is hereby requested. It is my opinion that the elevated TPH-g and <br /> benzene concentrations identified in the sample collected from MW-6 on January 22, <br /> 1997 should not adversely affect pians for closure of this low-risk site and the <br /> abandonments by pressure-grouting of MW-4 through MW-8. The case for an <br /> != isolated, relatively minor spill source (not another UST) having occurred somewhere in <br /> the soil between the slough shoreline and MW-6 merits serious consideration. <br /> Hydrocarbon degradation by natural attenuation has been taking place with the <br /> passage of time. An exploratory levee excavation to expose and remove the <br /> suspected source is not a feasible option. <br /> i.`.i As a courtesy, two copies of this report will be forwarded to: <br /> Mr. Steve Sasson, R.E_H.S. <br /> San Joaquin County Public Health Services <br /> Environmental Health Division <br /> P.O. Box 388 <br /> Stockton, California 95201-0388 <br /> DAYNE L. FRARY, GEOLOGIST 7 <br /> 1296-012.197 <br />