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ENVIRONMENTAL HEALTH DEPARTMENT <br /> ° <br /> Donna K. Heran, R.E.H.S. SAN JOAQUIN COUNTY Unit Supervisors <br /> Director 304 East Weber Avenue,Third Floor Carl Borgman,R.E.H.S. <br /> At Olsen, R.E.H.S. Stockton,California 95202-2708 Mike Huggins, R.E.H.S., R.D.I. <br /> • c9( Foa`'�P • Program Manager Telephone: (209)468-3420 Douglas W. Wilson, R.E.H.S. <br /> Laurie A. Cotulla, R.E.H.S. Margaret Lagorio,R.E.H.S. <br /> Program Manager Fax: (209)464-0138 Robert McClellon, R.E.H.S. <br /> Website:www.sjgov.org/ehd/ Jeff Carruesco, R.E.H.S. <br /> HAROLD & DENA KNOWLES AUG 3 i 2005 <br /> C/O LAW OFFICE OF PATRICK D RIDDLE <br /> 1811 GRAND CANAL BLVD STE 2 <br /> STOCKTON CA 95207-8107 <br /> RE: 102 S. Wilson Way Site Code: 9031 <br /> Stockton, CA <br /> San Joaquin County Environmental Health Department (EHD) has reviewed <br /> Second Quarter 2005 Groundwater Sampling Report, dated 29 June 2005 and <br /> data from other reports prepared on your behalf by Ground Zero Analysis, Inc. <br /> (GZA) for the above referenced site to evaluate GZA's recommendations to <br /> reduce the quarterly ground water monitoring requirements. EHD has given <br /> verbal approval to GZA to reduce sampling during the second and third quarterly <br /> groundwater monitoring events this year. <br /> In the quarterly report for the third quarter 2005 groundwater monitoring event, <br /> please provide a proposed sampling schedule for each well in your monitoring <br /> well network and provide the rational for the sampling frequency proposed for <br /> each well. EHD's main concerns for evaluating the proposed schedule include: <br /> • Detection of plume migration, <br /> • Tracking concentration trends of key chemicals of concern (COC), such as <br /> 1,2-dichloroethane (1,2-DCA), methyl tert-butyl ether (MTBE), total <br /> petroleum hydrocarbons quantified as gasoline (TPH-g), and benzene, <br /> toluene, ethylbenzene and total xylenes (BTEX); and <br /> • Effectively differentiating the three plumes inferred to be impacting your <br /> site. <br /> EHD had directed you by letter dated 18 September 2003 to test each vapor <br /> extraction well for mass contribution during operation of the soil vapor extraction <br /> (SVE) extraction system. To address this directive while the site's SVE system is <br /> not operational, GZA proposed to utilize their technician, who was conducting <br /> some vapor extraction tests in the area, to test the vapor wells on this site during <br /> the third quarter groundwater monitoring event. EHD gave verbal approval on 15 <br /> August 2005 to conduct the test on 16 August 2005. Please submit a report of <br /> findings on the soil vapor extraction test with a description of the methodologies <br /> utilized to conduct the test to EHD no later than 01 November 2005. <br />