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ENVIRONiENTAL HEALTH trEPARTMENT <br /> SAN JOA UIN COUNTY <br /> { y Program Coordinators <br /> q, Donna K. Here,R.E.H.S.. 304 East Weber Avenue,Third Floor Carl Borgman,R.E.H.S. <br /> ` Director <br /> . ' La„rie A.Cotutta;R.E.H.S. Stockton,California 95202-2708 Mike Huggins,R.E.H.S.,R. ;t: <br /> Assistant DirectorTelephone: (209)46$-3420 Margaret Lagorio, R.E.H.S. <br /> Robert McC1e11on,R.E.H.S. <br /> Fax: (209)464-0138 Jeff Carruesco,R.E.H.S. <br /> Wbbsite-:www.sjgov.org/ehd/ Kasey Foley,R.E.H.S. <br /> XA$jW1R SINGS A DA:LWINDER DHOOT 9 LUVD <br /> 156 00 S HAIZLAN ROAD <br /> LATHRQP. CA 95:33.0 <br /> P.Ev :J.oe's:Place- SITE CODE: 2315.85 <br /> 15600 Harlah:.R+oad <br /> ,t athrop,,Ca: <br /> Sari Joaquin jaunty Environmental Health Department(EHD)has reviewed°Additional.. <br /> Assessment Report"dated June 27, 2006,prepared by SECOR International Inc.for the above <br /> referenced site: Concentrations of MTBEn the water samples from the monitoring wells were <br /> Highest in MVI. 1 and MW2 fn:2000. By 2002 the highest concentrations of MTBE in:the water <br /> samples from the monitoring wefts was found in MW3. By September 2005 the highest, <br /> concentrations:in the water samples from the monitoring wells was found in off site MW. and <br /> concentrations;in M11V1 I the mast down gradient off site well have confirmed MTBE to be in`tfte <br /> ground"ter in that locatfon..:Aithough the concentrations of MTBE in the.groundwater are rn:uch. <br /> reduced from those found in 2000;thecontaminant plume is continuing to migrate. <br /> In the reporfSECOR recorhmends in,situ:pulse injection of oxygen to increase the dfssolved <br /> oxygen doncentratlon,which should ricrease the rate of biodegradation and does not recommend <br /> groundvi+a#er eXtraction because it ie not C05t-effective, SECOR did not provide any details:on the <br /> costs of a groundwater extraction system in comparison to the cost of in-situ pulse injection .. <br /> oxygen system to justify thelr recommendatlon. <br /> EHD staff discussed the recommendation of in=situ pulse injection of oxygen with.staff of the <br /> Central Valley Regional Water Quality.Control Board {CVRWQCB). SECQshould provide more <br /> information on this recommendation, If oxygen is#o be used then an evIaluation.of the <br /> geochemistry of,the.water must be performed to show that a waste would no#"be generated from <br /> thoinkoduction of oxygen that would require Waste Discharge Requirements by the CVRW.QCB. <br /> In additiort, addresses.of sees.with similar characteristics(lithology;depth to groundwater,: <br /> contaminant concentrations)where this technology has been successful in remediating MTBE <br /> must be provided to EHD::and CVRWQC9. SECOR should also evaluate the alternative of <br /> extracting and disposing of:contaminated water from monitoring wells with the highest <br /> concentrations<of MTBE on an interim basis to reduce the concentrations of MTBE contamination <br /> on:and off site. <br /> In.addition, sini a the dnwrt gradient extent of the MTBE=contamination is not defined<a work}plan <br /> for defining the MTBE.contarininant plume should be submitted to EHD by October 2, 2006.. <br /> If you have any questions contact me at{209}468-3449. <br /> Donna Heran,RENS, director <br /> Erivironmental Health Department <br /> Margaret gorio, REHS <br /> Program Coordinator Unit IV <br /> c:: CVRWQCB-Jinn Barton <br /> SECOR—Todd Brawn <br />