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T <br /> V TJ%ViAONMENTAL HEALTH DIVISION 1117 Lone Palm Avenue <br /> Q suite B <br /> Modesto CA 95351 <br /> 209 579 2221 <br /> Fax 209 579 2225 <br /> ASSOCIATES i N <br /> 3fD4 E Weber Ave Third Floor <br /> P O Box 388, Stockton CA 95201-0388 <br /> Approved <br /> Denied ° p <br /> April 11, 2000 Conditions('M- t.4u� AKn. ct'O.A_ 4A� c&5UA-e <br /> 54 13099 0001 ,,fit &4 <br /> Date too Y ��Lei G1 VIED <br /> Mr Harlin Knoll APR 12 2000 <br /> San Joaquin County Public Health Services ENVIRONMENTAL HEALTH <br /> Environmental Health Division PERMIT/SERVICES <br /> 304 E Weber Street, Third Floor <br /> Stockton, California 95202 <br /> Subject Monitoring Report First 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 /> March 6, 2000 by ATC Associates Inc at the site located at 304 North Acacia Avenue, 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 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 were backfilled <br /> with the stockpiled material <br /> On April 23, 1998, a geologist from ATC Associates supervised the advancement of six soil <br /> borings, SBI through SB6, to 21 feet below ground surface (bgs) A site plan showing soil <br /> boring locations is included as Figure 2 Soil samples were collected at five-foot intervals and <br /> grab groundwater samples were collected from each boring Samples were analyzed for <br /> petroleum hydrocarbons and elevated concentrations of petroleum hydrocarbons were detected in <br /> soil and groundwater samples The April 1998 subsurface investigation results are detailed in <br /> 0) ATC's Summary Report of Subsurface Investigation, dated June 17, 1998 <br /> w1130991quartiy\Igr-2000 doc 1 <br />