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ENVIRONMENTAL HEALTH DEPARTMENT <br /> ° SAN JOAQUIN COUNTY <br /> °� Unit Supervisors <br /> :2 <br /> .� Donna K.Heran,R.E.H.S. <br /> :< 304 East Weber Avenue, Third Floor Carl Borgman,R.E.H.S. <br /> Director Mike Huggins,R.E.H.S.,R.D.I. <br /> Al Olsen,R.E.H.S. Stockton, California 95202-2708 <br /> Douglas W.Wilson,R.E.H.S. <br /> • cq... ��P • Program Manager Telephone: (209) 468-3420 Margaret Lagorio,R.E.H.S. <br /> <<FOR Laurie A.Cotulla,R.E.H.S. <br /> Program Manager Fax: (209) 464-0138 Robert McClellon,R.E.H.S. <br /> Mark Barcellos,R.E.H.S. <br /> FRANK MORITA <br /> NOV '2 4 2004 <br /> 6622 BELMONT PL <br /> STOCKTON CA 95207 <br /> RE: Morita Brothers Site Code: 1061 <br /> 814 E Charter Way <br /> Stockton, CA <br /> San Joaquin County Environmental Health Department (EHD) has received and <br /> reviewed Report: Groundwater Monitoring Yd Quarter 2004 (QR) dated 12 November <br /> 2004, prepared by Geological Technics Inc. (GTI) on your behalf. In the QR, GTI <br /> recommends: 1) Maintaining the quarterly monitoring schedule; 2) Reducing the <br /> sampling frequency from quarterly to semi-annually for monitoring wells MW-1, MW-3, <br /> MW-4, MW-5, MW-6 and MW-104; 3) Performing a file review of EHD records for the <br /> two up-gradient LUFT sites to determine if a co-mingled plume exists; and 4) Advancing <br /> a CPT boring east of the site to delineate the groundwater plume margin. <br /> Reviewing the site data, particularly the recent groundwater analytical data, EHD <br /> believes it may be appropriate to move toward a closure consideration at this time. <br /> Contaminants in only one well (MW-106) exceed a primary maximum contaminant level <br /> (MCL), that for methyl tert-butyl ether (MTBE) at 16 micrograms per liter (µgh), and four <br /> wells exceed the odor/taste threshold for total petroleum hydrocarbons quantified as <br /> gasoline (TPH-g) at 192 µg/I, 106 µg/I, 57 µg/l and 302 µg/I in wells MW-106, MW-107, <br /> MW-108 and MW-208, respectively. These concentrations are not suggestive of a <br /> significant dissolved contaminant mass that poses a high risk to sensitive receptors, <br /> additional groundwater supplies or human health. GTI has suggested that the dissolved <br /> contaminants encountered in MW-108 and MW-208 may be from off-site. <br /> Preparatory to submitting a closure request, please update your site conceptual model, <br /> incorporating recently acquired lithological and analytical data to present a <br /> hydrogeological model with sorbed and dissolved contaminant masses and migration <br /> pathways. The model should incorporate a fate and transport model for the sorbed and <br /> dissolved contaminants. If you believe some of the contamination originates from other <br /> sites, review of their reports and incorporating the data into your model to demonstrate <br /> this hypothesis would be appropriate. If you need to acquire additional field data to <br /> complete your model, please submit a work plan addendum to advance the CPT <br /> boring(s). <br /> As samples from most of the older wells have not been analyzed for fuel oxygenates or <br /> lead scavengers since June 2001 and samples from the new wells have never been <br /> analyzed for these analytes, please include these analyses for the next quarterly <br />