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1117 Lone Palm Avenue <br /> V <br /> Suite B <br /> Modesto CA 95351 <br /> ATC I I 209 579 2221 <br /> Fax 209 579 2225 <br /> A S S O C I A T E S I N C <br /> , l <br /> January 20, 2000 <br /> 14981 <br /> Mr Ron Rowe <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 1999, N & S Irrigation Property, 215 West <br /> Main Street, Ripon, California <br /> Dear Mr Rowe <br /> This report presents the results of quarterly groundwater monitoring and sampling performed on <br /> December 30, 1999 by ATC Associates Inc at the site located at 215 West Main Street, Ripon, <br /> California (Figure 1) Monitoring was performed to determine the groundwater flow direction <br /> and the hydraulic gradient in the uppermost aquifer Sampling was performed to monitor the <br /> distribution of petroleum hydrocarbons in groundwater at the site <br /> BACKGROUND <br /> In March 1990, one 1,500-gallon unleaded gasoline underground storage tank (UST), one <br /> unleaded gasoline UST of unknown size, and all associated piping and dispensing equipment <br /> were removed and transported off-site Laboratory analysis of soil samples collected from <br /> beneath the former 1,500-gallon UST location indicated the presence of detectable <br /> concentrations of total petroleum hydrocarbons Discoloration of the soil and a petroleum <br /> hydrocarbon odor were noted in the field After the tanks were removed, the areas of the former <br /> tanks were backfilled <br /> On November 14, 1997, a geologist from ATC Associates supervised the advancement of two <br /> soil borings to 30 feet below ground surface (bgs) Analytical results of soil samples indicated <br /> the presence of petroleum hydrocarbons One groundwater sample was collected from each <br /> boring at the depth groundwater was first encountered, approximately 30 feet bgs Groundwater <br /> samples indicated the presence of petroleum hydrocarbons Results are summarized in ATC's <br /> Summary Report of Subsurface Investigation, dated January 14, 1998 <br /> On July 13, 1998, a geologist from ATC Associates supervised the advancement of four soil <br /> borings to 26 to 31 feet bgs Analytical results of soil samples indicated the presence of <br /> w 1149811quardyAgr-1999 doe 1 <br />