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i <br /> Il San Joaquin County <br /> Environmental. Health Department DIRECTOR <br /> : �.:..p Donna Heran, REHS <br /> z y 600 East Main Street <br /> J"% PROGRAM COORDINATORS <br /> Stockton, California 952023029 Robert WClellon,REHS <br /> • Jeff Carruesco, REHS,RDI <br /> '• _ ` �•• <br /> Website: www sjgov org/ehd Kasey Foley, RENS <br /> cr�o� Phone: (209) 468-3420 <br /> f <br /> Fax: (209)464-0138 <br /> June 21, 2010 <br /> Mr. Sergio Morescalchi <br /> Environmental Business Manager <br /> Atlantic Richfield Company <br /> P.O. Box 1257. <br /> San Ramon, CA 94583 <br /> Subject: ARCO Service Station No. 5469 <br /> 130 S. Wilson Way <br /> Stockton, California, 95205 <br /> San Joaquin County.Environmental Health Department (EHD,) has reviewed Second Semi-Annual <br /> 2009 Groundwater.Monitoring andRemediation Progress Report, dated'.March 23, 2010, prepared <br /> by your consultant Arcadis. In the report, Arcadis recommended: <br /> • Removal of di-isopropyl ether (DIPS), ethyl tertiary butyl ether (ETBE), tertiary amyl methyl <br /> ether (TAME), ethylene dibromide (EDB), and ethanol from the suite of analytes for <br /> groundwater samples; <br /> • Modification of-the monitored natural attenuation (MNA) monitoring program by collecting <br /> the parameter data annually from,monitoring wells MW-2, MW-4, MW-6, MW-8, MW-11, <br /> MW-12, MW-9 and MW-10, dropping the tests for total iron, nitrite (NO2) and total dissolved <br /> solids (TDS) from the current monitoring. regimen -and. adding tests. for methane..and <br /> alkalinity, and performing plate counts during the first annual monitoring event; <br /> • Shutdown of the ozone injection system; and <br /> Initiating post remedialmonitoring and sampling to evaluate remediation effectiveness. <br /> f <br /> The EHD approves these recommendations for. immediate implementation with the exception of <br /> dropping the analysis for DIPS in samples from MW-9 and MW-10. <br /> SII <br /> Questions or comments may be directed to Nuel Henderson at (209) 468-3436. <br /> Sincerely, <br /> Nuel C. Henderson,Jr., PG Adrienne Ellsaesser, REHS <br /> Engineering Geologist Acting Program Coordinator <br /> C: Thomas Potter—Arcadis — 950 Glenn Dr.; Ste 125, Folsom, CA 95630 <br /> James Barton, PG - CVRWQCB - 11020 Sun Center Dr:#200, Rancho Cordova, CA 95670 <br /> y Directive tetter 0610.doc <br />