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i <br /> PUBLIC AALTH SERVI&S <br /> SAN JOAQUIN COUNTY <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Karen Furst, M.D., M.P.H., Health Officer <br /> 304 East Weber Avenue, Third Floor • Stockton, CA 95202 C`7 <br /> 209/468-3420 AUG 2 91997 <br /> GEORGE AND MEI TERANISHI <br /> 1600 WEST DURHAM FERRY RD <br /> TRACY CA 95376 <br /> RE: GEORGE'S SERVICE SITE CODE: 1550 <br /> 1600 WEST DURHAM FERRY <br /> TRACY CA 95376 <br /> San Joaquin County Public Health Services, Environmental Health Division(PHS/EHD) has completed <br /> review of the " Report- Soil and Groundwater Investigation"dated August 5, 1997. PHS/EHD has the <br /> following comments for your consideration and response. <br /> The Report included a summary of the installation of five shallow and one deep groundwater monitoring <br /> well and the results of one groundwater monitoring event. The monitoring wells were installed between <br /> April 29, 1997 and April 30, 1997. The shallow monitoring wells,MW4 - MW8,were drilled to a total <br /> depth of 22 feet below ground surface(bgs)and the deeper well, MW 102, was drilled to a total depth of <br /> 50 feet bgs. A temporary 12 inch conductor casing was used during the installation of MW 102. <br /> Soil samples were collected during the drilling of the monitoring well boreholes which provided <br /> additional information regarding the distribution of contamination. Unfortunately, insufficient soil was <br /> recovered for laboratory analysis from the sample collected at 10 feet bgs during the drilling of MW5. If <br /> this sample had been obtained,the extent of soil contamination evidenced in the soil sample collected at <br /> 9-9.5 feet from HP-6 which was located approximately 10 feet east of MW5, may have been defined. <br /> With the exception of this area,west of the former tank and pump island, the extent of soil contamination <br /> appears characterized. <br /> The groundwater monitoring wells and nearby domestic wells were most recently sampled on May 5, <br /> 1997. The analytical results from the groundwater samples collected from the domestic wells did not <br /> detect contamination above the detection limit; however, significant groundwater contamination was <br /> detected in the sample collected from MW102, indicating that the groundwater plume is not limited <br /> vertically. The analytical groundwater sample results, from MW102 which was screened between 42.5 <br /> and 45 feet bgs and from MW2 which was screened between 5 and 20 feet bgs, were comparable. These <br /> samples evidenced benzene concentrations between 219 ppb and 287 ppb and total petroleum <br /> hydrocarbons-gasoline concentrations between 9,000 ppb and 6,819 ppb. Methyl tertiary butyl ether <br /> contamination was confirmed at 5.8 ppb from the sample collected from MW2. <br /> The report stated that the newly installed wells were surveyed relative to the elevation of MW2 on May <br /> 9, 1997 and that there may have been an error with collecting elevation data from MW5 which would <br /> warrant the re-survey of the wells. MW2 was previously surveyed relative to an arbitrary plane. <br /> PHS/EHD highly recommends that the wells be surveyed by a licensed surveyor relative to a known <br /> permanent benchmark. <br /> Please submit laboratory QA/QC data for the samples submitted for analysis. Also. PHS/EHD questions <br /> the necessity to submit for analysis 5 bailer blanks and 1 trip blank for 12 groundwater samples collected <br /> from the monitoring wells. Generally, bailer blanks are run if evidence exists to suggest that the <br /> A Division of San Joaquin County Health Care Services <br />