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ICAALTH SERVI'ESPUBLoPo�,N <br /> SAN JOAQUIN COUNTY <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Karen Furst, M.D., M.P.H., Health Officer <br /> 4C/PORN <br /> 304 East Weber Avenue, Third Floor • Stockton, CA 95202 <br /> 209/468-3420 r <br /> PETER NEMIEC <br /> ASSISTANT COUNSEL 1 <br /> UNOCAL CORPORATION <br /> DIVERSIFIED BUSINESS GROUP <br /> 376 VALENCIA AVENUE SEP 131999 <br /> BREA CA 92823 <br /> RE: UNOCAL <br /> 437 E. Miner Avenue SITE CODE: 1181 <br /> Stockton, CA <br /> San Joaquin County Public Health Services, Environmental Health Division <br /> (PHS/EHD) has reviewed the "Supplemental Site Characterization Report" dated <br /> June 3, 1999, prepared by ARCADIS Geraghty & Miller and the "Second Quarter <br /> 1999 Groundwater Monitoring & Sampling Report" dated June 3, 1999, prepared <br /> by Gettler-Ryan Inc. for the above referenced site. <br /> PHS/EHD does not agree that the Site has been adequately characterized or <br /> that sufficient data exists to prepare a Corrective Action Plan. The lateral extent <br /> of soil contamination from 60 to 70 feet below surface grade (bsg) has not been <br /> defined. The vertical and lateral extent of groundwater contamination has not <br /> been defined. Site specific feasibility studies of viable remedial alternatives have <br /> not been conducted, to comply with the requirements of Section 2725 (f) (2) of <br /> the California Code of Regulations, Title 23, Division 3, Chapter 16, Article 11. <br /> Analytical results of the groundwater samples obtained from NP1 and NP2 <br /> during the Simulprobe investigation at depths that correspond to NP1-22, NP1- <br /> 65, NP1-111, NP2-22, NP2-60 and NP2-116 (NP wells), are similar to the <br /> analytical results of the groundwater samples obtained during the first and <br /> second quarter 1999 groundwater sampling events from those NP wells. This <br /> data confirms the concentration of contaminants at these intervals. Although, <br /> groundwater samples from NPI-65 evidence the highest levels of contamination, <br /> including samples from NP2-60, contaminant concentrations are higher in the <br /> water samples from NP2-116 than the water samples from NP1-111. This <br /> indicates that deeper groundwater contamination concentrations are higher off- <br /> site, downgradient than they are in the area where the unauthorized release <br /> occurred. Therefore, it is premature to discuss plume stability or movement. <br /> The "Supplemental Site Characterization Report" (Report) states that the <br /> ,'monitoring well array provides data which allows interpretation of the impacts to <br /> A Division of San Joaquin County Health Care Services <br />