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i � 1SKTN71, i`,r� <br /> JwL <br /> ENVIRONMENTAL7ECHNOLOGIESCORPORATION ��r 1 ,. 1rSa C!+. <br /> l J _ <br /> December 12, 1997 <br /> 94373 <br /> Ms Mary Meays <br /> San Joaquin County Public Health Services <br /> Environmental Health Division <br /> 304 E Weber Street, Third Floor <br /> Stockton, California 95202 <br /> Subject Monitoring Report Fourth Quarter 1997, Former Thiemann's Service Station, 106 <br /> West Second Street, Ripon, California <br /> Dear Ms Meays <br /> This report presents the results of quarterly groundwater monitoring and sampling performed in <br /> October 1997 by Smith Technology Corporation (acquired by ATC Associates) at Former <br /> Thiemann's Service Station The site is located at 106 West Second Street in Ripon, California <br /> (Figure 1) Sampling was performed to monitor the distribution of petroleum hydrocarbons in <br /> groundwater at the site Monitoring was performed to deterrune the groundwater flow direction <br /> and the hydraulic gradient in the uppermost aquifer <br /> SITE HISTORY <br /> In March 1991, three underground storage tanks (USTs) were removed from the site Analysis of <br /> soil samples collected from the excavation indicated that high concentrations of petroleum <br /> hydrocarbons were present in soil beneath the tanks Groundwater was not encountered in the <br /> excavation The location of the former USTs is shown on Figure 2 <br /> In July 1993, a subsurface investigation was conducted at the site to determine the extent of <br /> petroleum hydrocarbons present in soil and to determine if groundwater had been impacted This <br /> included drilling eight soil borings and collecting soil samples Three of these bonngs were <br /> completed as shallow groundwater monitoring wells (MW-1, MW-2 and MW-3) Analysis of soil <br /> samples Indicated that the majority of petroleum hydrocarbons in soil were present from about 10 <br /> feet below ground surface (bgs) to groundwater at a depth of approximately 29 feet bgs and <br /> within a radius of 35 feet from the former UST pit <br /> w D43731quart1yl4gr-1997 doc 1 <br /> 1260 Graphics Drive - Modesto,CA 95351-1502 (209)579-2221 Fax(209)579-2225 <br /> Engineering Consulting - Remediation Construction <br />