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�N <br /> PUBLIC H?ALTH SERVI( L'S <br /> SAN JOAQUIN COUNTY a - '— <br /> Q: <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Karen Furst, M.D., M.P.H., Health Officer cq., P <br /> 304 East Weber Avenue, Third Floor • Stockton, CA 95202 `'FSR <br /> 209/468-3420 <br /> PETER J NIEMIEC ESQ <br /> UNOCAL CORPORATION <br /> 376 S VALENCIA AVE <br /> BREA CA 92823 FEB 2 4 2000 <br /> RE: UNOCAL#6981 SITE CODE: 1217123 <br /> 4707 Pacific Ave. <br /> Stockton, CA <br /> San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) has <br /> reviewed the"Well Installation and Soil Boring Report" dated November 15, 1999 and the"Fourth <br /> Quarter 1999 Groundwater Monitoring &Sampling Report" dated December 20, 1999, prepared <br /> by Gettler-Ryan Inc. for the above referenced site. <br /> The vertical extent of Benzene, TPH as gasoline, and MtBE in soil appear to be defined in the <br /> area of VW7. The highest concentrations of contamination in the soil at this site appear to be in <br /> the area of VW7 at depths of 36 to 61 feet below surface grade (bsg). Soil contamination above <br /> 36 feet bsg in the area of VW7, which is located near VW2 (1311), appears to be reduced. When <br /> VW2 was installed it was screened from 25.5 to 50.5 feet bsg. VW2 has collapsed or been <br /> obstructed since its total depth is now 28.5 feet. If this had not occurred, remediation of soil <br /> beneath 36 feet bsg may have been achieved. The highest soil contamination in VW7 was <br /> evidenced at 41 feet bsg. <br /> Soil contamination appears reduced in the area of MW2 (132) to a depth of 46 feet bsg. Soil <br /> sample results from MW16 (collected 8/17/99) at 26, 36 and 46 feet bsg are much lower than the <br /> soil samples from MW2 (collected 2/1/90) at 25, 35 and 45 feet bsg. In addition, soil <br /> contamination in the area of MW5 (B5) and VW3 (B12) appears reduced when the soil sample <br /> results from their installation are compared to the non-detect soil sample results obtained when <br /> VW9 was installed. <br /> Soil sample results from MW7 (B8) installed in March 1992 and PTW1 (B18) installed in August <br /> 1992 evidenced low levels of contamination from 35 to 56.5 feet bsg. Analytical results of the soil <br /> samples collected from 21 to 39 feet bsg when installing MW14 in August 1999 were non-detect. <br /> Soil samples collected from MW16 (installed 8/99)were non-detect at 21, 26, 56 and 61 feet bsg, <br /> but contamination was evidenced in the samples from 36 and 46 feet bsg. This is the same <br /> interval where the highest concentrations of contamination exist in the area of VW7. Soil samples <br /> from this interval were not analyzed when MW11 (616)was installed in August 1992. <br /> There are no monitoring wells in the areas of VW2 and MW2 or down-gradient of these areas that <br /> have screens intersecting the 36 to 46 feet interval. Therefore, the extent of groundwater <br /> contamination at this level has not been determined. <br /> A Division of San Joaquin County Health Care Services <br />