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r <br /> t <br />` 1117 Lone Palm Avenue <br /> Suite B <br /> Modesto CA 95351 <br /> 209 579 2221 <br /> i Fax 209 579 2225 <br /> A S S O C I A T E S I N C <br /> •� ('-. to ` „1 .[+1 f,. <br /> May 3, 1999 <br /> 62500 <br /> Mr Jeff Wong <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 First Quarter 1999, Continental Grain, 1805 Harbor Street, <br /> Stockton, California <br /> Dear Mr Wong <br /> This report presents the results of quarterly groundwater monitoring and sampling performed in <br /> February 1999 by ATC Associates Inc at the site located at 1805 Harbor Street, Stockton, <br /> California (Figure 1) Sampling was performed to monitor the distribution of petroleum <br /> hydrocarbons in groundwater at the site Monitoring was performed to determine the <br /> groundwater flow direction and the hydraulic gradient in the uppermost aquifer <br /> SITE HISTORY <br /> In January 1988, one 10,000-gallon gasoline underground storage tanks (UST) and all associated <br /> piping were removed from the location shown on Figure 2 One soil sample was collected from <br /> each end of the UST and analytical testing indicated the sample contained detectable <br /> concentrations of petroleum hydrocarbon constituents The excavation was subsequently <br /> backfilled <br /> In October 1997, an ATC geologist supervised the advancement of seven soil borings to <br /> approximately 26 feet bgs The borings were advanced using a truck mounted Geoprobe® <br /> narrow diameter rig employing direct push technology Soil and grab groundwater samples <br /> collected from the vicinity of the former 10,000-gallon UST contained elevated concentrations of <br /> petroleum hydrocarbons <br /> On August 12, 1998, ATC personnel supervised the advancement of three soil borings, MWI <br /> through MW3, at the site to depths of approximately 28 feet bgs to investigate the horizontal and <br /> vertical extent of petroleum hydrocarbon impacted soil and groundwater The soil borings were <br /> icompleted as groundwater monitoring wells and on August 14, 1998 the wells were developed <br /> w 1625001quart1y11gr-1999 doc 1 <br />