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1117 Lone Palm Avenue Suite 8 <br /> Q Modesto California 95351 <br /> vwvwatc-enviro com <br /> 209 579 2221 <br /> ' r Fax 209 579 2225 <br /> tar- cf 7 <br /> A S S O C I A T E S I N C <br /> 1 f ^ fli# � 32 <br /> October 9, 2000 <br /> 54 13099 0001 <br /> Mr Harlin Knoll <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 Third Quarter 2000, Ripon Unified School District, 304 North <br /> Acacia Avenue, Ripon, California <br /> Dear Mr Knoll <br /> This report presents the results of quarterly groundwater monitoring and sampling performed on <br /> September 13, 2000 by ATC Associates Inc at the site located at 304 North Acacia Avenue, <br /> Ripon California (Figure 1) Monitoring was performed to determine the groundwater flow <br /> • direction and the hydraulic gradient in the uppermost aquifer Sampling was performed to <br /> monitor the distribution of petroleum hydrocarbons in groundwater at the site <br /> BACKGROUND <br /> In February 1991, one 500-gallon underground storage tank (UST) of unknown fuel type was <br /> removed, in August 1991, one 550-gallon unleaded gasoline UST was removed, in October <br /> 1991, 47 feet of single wall piping was removed, and, in December 1991, one 7,500-gallon <br /> unleaded gasoline UST was removed Laboratory analysis of soil samples collected from <br /> beneath the former USTs and piping locations indicated the presence of detectable concentrations <br /> of total petroleum hydrocarbons Discoloration of soil and petroleum hydrocarbon odors were <br /> noted in the field After the tanks were removed, the areas of the former tanks wei e backfilled <br /> with the stockpiled material <br /> On April 23, 1998, a geologist from ATC Associates supervised the advancement of six soil <br /> borings, SB 1 through S136, to 21 feet below ground surface (bgs) Soil samples were collected at <br /> five-foot intervals and grab groundwater samples were collected from each boring Samples <br /> were analyzed for petroleum hydrocarbons and elevated concentrations of petroleum <br /> hydrocarbons were detected in soil and groundwater samples The April 1998 subsurface <br /> investigation results are detailed in ATC's Summary Report cif Subsurface .Investigation, dated <br /> June 17, 1998 <br /> DD-D <br /> w 1130991quar 1yl3gr-2000 doc 1 <br />