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MAY. -0?' 99 (FRI) 08:55 UNOCAL r--")T NORTH RE TI.L:510 3181 P, 002 <br /> PUBLIC HEALTH SERVICES ' <br /> SAN.JOAQUTN COUNTY <br /> - =r' i <br /> LNVIRONMHNTAL HEALTH DIVISION <br /> Karen Furst, M.D., M.P.H., Heal& Officer <br /> 304 East Weber Avenue, Third Floor - Stockton, CA 95202 <br /> 2091468-3420 <br /> ROBERT BOVST <br /> UNOCAL CORPORATIONlAY Q 4 1999 <br /> if 2121 N CALIFORNIA BLVD SMTE 250 <br /> WALNUT CREEK CA 94596 <br /> RE: UNOCAL SITE CODE: 1213 <br /> 1665 Pacific Avenue <br /> Stockton, CA <br /> San Joaquin County Public Health Services, Environmental Health Division (PHSIEHD) has <br /> reviewed the"Supplemental Site Characterization Report'dated February 26, 1999, prepared by <br /> ARCADIS Geraghty & Miller, Inc. for the above referenced site. <br /> PHSIEHD does not agree that the Site has been adequately characterized and that the <br /> infon•nation provided shows that the Site will attain Basin Plan water quality objectives with no <br /> further action. With gnawing populations and limited soureps of water, the issues of defining - <br /> contaminant plumes and restoring groundwater quality are important since it is not known when ` <br /> the water will be used. <br /> The lateral and vertical extent of soil and groundwater carrtamination from the unauthorized <br /> release of petroleum from the underground storage tanks formerly operated at this site has not <br /> been adequately identified. Feasibifi studies of viable remedial'iaftemativos, given the current <br /> site conditions have not been conducted. Compliance with the Corrective Action Requireme-nTs ink '. <br /> the California Code of Regulations, Title 23, Division 3, Chapter 16, Article 11 has not occurred. a' <br /> The vertical extent of soil contamination on site has been shown; however further analysis of <br /> water from NF1 must be completed to evaluate whether the vertical extent of groundwater <br /> contamination oil site Iius been determined.. Tne downgr'adient extent of impact tD soil and <br /> groundwater has not been shown_ Soil samples off site and downgradient from below 40 feet of <br /> surface grade have not been analyzed_ Analysis of sail samples off site and downgradient from <br /> below 40 ll&ul of surface grade should be conducted to demonstrate the lateral and vertical extent <br /> Of soil contamination. <br /> The Ievels of contaminants in fire groundwater sample from monitoring well (MW) 10 (screened <br /> interval 50—60 feet)obtained on February 4, 1999, are between the level of contaminants found <br /> in the water samples collected from 50 feet and 60 Beet below surface-grade (bsg) on January 5, <br /> 1999, using the Simulprobe during drilling of NP1. The level of contaminants in the groundwater <br /> sample from MM are higher than those found in the groundwater sample from MW2(screened <br /> interval 20—60 feet). <br /> Downgradient monitoring wells do not extend to the most contaminated depth of 60 feet below <br /> surface grade (bsg); so lateral definition at this depth has not been shown. in addilinn. there are <br /> no monitoring wells downgradlent and off site that are screened at 90 feet bsg or deeper to show <br /> that the petroleum contaminants did not impact the deeper water downgradient and off site, <br /> EXHIBIT 1 <br /> A 0Mslon or San Joaquin County Health Cam Swviem � <br /> I <br />