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t <br /> U <br /> ENVIRONMENTAL HEAL'T'H DEPARTMENT <br /> • <br /> SAN JOAQ rUIN COUNTY <br /> Coordtttatnrs <br /> Ram <br /> K <br /> Donna K. ,R.E.H.S. <br /> ," .• 304 East Weber Avenue,Third Floor Cart Borsman,R.E.H.s. <br /> Director <br /> ° Laurie A.Cowin,RXJLS. Stockton,California 95202-2708 Mike Huggins,R.R.H s.,R.D.T. <br /> ;jrc3' hbraret Lagorio,R.E.H.s. <br /> Ass t Direcioi Tele hone; 209 4f8 <br /> -Robert McClellon,R.E.H.S, <br /> Fax: (209)464-0138: _ Jeff Camtesco,R.E.H:s. <br /> Website:www.sjgov.orgleW Kasey Foley,R.E.H.& <br /> LE <br /> ." R nNt3H a AA41�f D1�R lki�ICiQfi 96 <br /> cooly I� <br /> 1"0,0 S :HART[AN R4 <br /> LATHRC?>is M 05330 <br /> REP. J0014 pude. SITE C00M. 284686 <br /> i1558i�0:::H+�iran::Riyad. <br /> :r'`athrca: <br /> San,lioa ttin.0antyfivironmentai Heaifh Department(EHC�)has r+evieuved ," dditioda�i <br /> ent <br /> AssessmReport"dated June 27,2086,prepared by SECOR Internatlonat Inc.for the above <br /> referenced site: Concentrations iofMT815in the water samples from the monitoring webs were <br /> highest Irr MW ! and MW2 in 2000. By 2002 the highest concentration of MTBE in the water � <br /> samples from the monitoring wells was found in MW3. By September 2005 the htghost. <br /> Condentrations in the water samples from the monitoring wells was found in Off site MW9 and <br /> concentrations In.MW 1-1 the most down gradient off site well have confirmed MT 115 to be in the <br /> groundwater In thtd6ca#ron Although the concentrations of MTBE In the groundwater are Muctl <br /> reduced from those fcwwr !Irl 26W the r ntaminant plume is continuing to rnigrete: <br /> !n the report SEC0R recommends ln,situ;pulse injection of oxygen to increase the dissaN <br /> taxygen concentration-Which should increase the rate of biodegradation and does not recotrirnend <br /> groundwater extractionoecause it Is not cost-effective. SECOR did not provide any detalls.+on the' <br /> -costs of a groundwater-extraction system in comparison to the cost of an in-situ pulse injection of <br /> •oxygen system t#:justify their.recommendation. <br /> E1,10 staff rdiscussed the,recommendation of In-situ pulse Injection of oxygen with sfaff of the` <br /> Central Valley regional Water Quality Control Sward(CVRWQCS). SECOR shouid.:orovide more <br /> Information on his recommendation. If oxygen Is to be:used:then an evaluation of the <br /> geochemistry of the watermust.#e;perfarrrted to show that a waste would not be generated from <br /> the introduction of oxygen#iiat would require'Waste Discharge,Requirements by the CVRWQCB. <br /> to addition.addresses of sift with similar characteristics(lithology,depth to groundwater, <br /> corhWminent concentrations)where this technology has:be+en successful in remediating M�`$ <br /> must`be provided to EHI)and CVRWQCB. SECOR should also evaluate the aiterna6e of j <br /> eattr acting and disposing ofcontaminated water from monitoring wells with the highest <br /> ovicentrations of MTBE on an interim basis to reduce the concentrations of MTBE contamination <br /> on ant off site: <br /> to addillok,sincer the down gradient extent of the MT8E contamination Is not defined a work ptart <br /> 46r defining Ehe tATSEzontaminant plume should be submitted to EHD by October Z.2006; <br /> Ilf you have anyquestions contaame at(209)468-3449. <br /> Donna Heron,AEHS,Clrector <br /> • <br /> Environmental tdeaith Department <br /> .Ariarganet otic,REFS <br /> grogram Coordlnator.Unit IV AUG <br /> c. CvkWQC8—Jim Darton 13 Y-. <br /> SECOR—Todd-Brown , <br />