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1117 Lone Palm Avenie <br /> �. Suite B <br /> Modesto, CA 95351 <br /> 209.579.2221 <br /> NT4tvIRONMENTAL HEALTH DIVISION Fax 209.579 2225 <br /> A s s a c I A T e s I N3b4 Weber Ave. Third Floor <br /> R O. Box 388, Stockton CA 95201-0388 <br /> Approved <br /> Denied [� <br /> April 11, 2000 Conditions(M" Ap p -d' Gee�w�E u� <br /> 54.13 099.0001 ,6t �. �- car, 1 <br /> D % .ate a 60 y 1 � � ' � <br /> °' <br /> Mr. Harlin Knoll APR 2?000 <br /> San Joaquin County Public Health Services =I\VJi {�NM EN 3 jai_ HEALTH <br /> Environmental Health Division ;.- M ITi Sc PR IiC S <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 /> �l ATC's Summary Report of Subsurface Investigation, dated June 17, 1998. <br /> Y <br /> w: 130991quardy11gr-2000.doc 1 <br />