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PUBLIC HEALTH SERVIC ; o <br /> SAN JOAQUIN COUNTY <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Karen Furst, M.D., M.P.H., Health Officerq:: <br /> 304 East Weber Avenue, Third Floor • Stockton, CA 95202 'FOR <br /> 2091468-3420 <br /> APR 2 5 2001 <br /> JOE KIRIM <br /> DIRECTOR,PHYSICAL PLANT <br /> UNIVERSITY OF THE PACIFIC <br /> 3601 PACIFIC AVENUE <br /> STOCKTON CA 95202 <br /> RE: 1081 MENDOCINO AVENUE <br /> STOCKTON,CA 95202 <br /> San Joaquin County Public Health Services,Environmental Health Division(PHS/EHD)has reviewed the <br /> "Additional Groundwater Assessment Report"submitted.on your behalf by Environmental Science <br /> Associates(ESA),dated March 26,2001. <br /> The report describes the results of an additional soil and groundwater assessment completed in January <br /> 2001. The purpose of the assessment was to define the horizontal and vertical extent of methyl tertiary- <br /> butyl ether(MtBE)detected in a previous groundwater investigation at the site. In July 2000,a <br /> concentration of 1300 micrograms per liter(gg/1)of MtBE was detected in a grab groundwater sample <br /> collected at the north end of the underground storage tank(UST)excavation at a depth of approximately 20 <br /> to 24 feet below ground surface. In January 2001,ESA returned to the site with the intent of installing ten <br /> additional borings to collect grab groundwater samples around the former UST location, as well as four <br /> borings to collect soil samples. Unfortunately,ESA was unable to install borings TP-6,TP-7,TP-8,and <br /> TP-11 due to saturated conditions as a result of heavy rain. Borings TP-8 and TP-11 are located in the <br /> presumed downgradient direction of groundwater flow. Therefore,MtBE contamination has not been <br /> adequately defined at the site. <br /> Three monitoring wells must be installed at the site to establish direction of groundwater flow. Following <br /> monitoring well installation,groundwater samples must be collected for a minimum of four quarters and <br /> analyzed for MtBE. Please note that before this site can be considered for closure,groundwater samples <br /> must be collected from all three wells and analyzed at least once for the following constituents:total <br /> petroleum hydrocarbons as gasoline;benzene,toluene,ethylbenzene and xylenes;the standard seven <br /> oxygenates by EPA Method 8260;and 1,2-dichloroethane and ethylene dibromide. <br /> Please submit a workplan for the installation of three monitoring wells at the site within 60 days of the date <br /> of this letter. If you have any questions,feel free to call Dot Lofstrom at(209)468-3436. <br /> Donna Heran,REHS,Director <br /> Environmental Health Division <br /> Dot Lofstr R.G. <br /> LOP/Site Mitigation Unit IV - <br /> cc: Marty Hartzell,CVRWQCB <br /> Peter Hudson,ESA <br /> A Division of San Joaquin County Health Care Services <br />