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ENVIRONMENTAL HEALTNEPARTMENT <br /> SAN JOAQUIN COUNTY <br /> Unit Supervisors <br /> Donna K.Heran,ME.H.S. Carl Borgman,R.E.H.S. <br /> Director 304 East Weber Avenue,Third Floor Mike Huggins,R.E.H.S.,R.D.I. <br /> Al Olsen,R.E.H.S. Stockton, California 95202-2708 Douglas W.Wilson,R.E.H.S. <br /> • cq �\P.• Program Manager Telephen*W209) 468-3420 Margaret Lagorio,R.E.H.S. <br /> Laurie A.Cotulla,R.E.H.S. Fes: (209) 464-0138 Robert McClellon,R.E.H.S. <br /> Program Manager Mark Barcellos,R.E.H.S. <br /> OCT 2 6 2004 <br /> GENE GABBARD INC JIM & SHEYLA CREEL <br /> 10335 CREEK TRAIL 640 EL DORADO <br /> STOCKTON CA 95209 STOCKTON CA 95202 <br /> RE: Gabbard Property SITE CODE: <br /> 640 EI Dorado <br /> Stockton CA 95202 <br /> San Joaquin County Environmental Health Department(SJC/EHD) has reviewed <br /> Groundwater Monitoring Well Installation Report(Report) dated March 16, 2004, and the <br /> second quarter groundwater monitoring and sampling report, prepared and submitted on <br /> your behalf by Ground Zero Analysis, Inc, (Ground Zero) and has the following <br /> comments. <br /> The Report documents the May 2003 installation of three additional shallow groundwater <br /> monitoring wells (MW-5, MW-6 and MW-7)at the above referenced contaminated <br /> underground storage tank site. The wells were installed to continue the investigation of <br /> the lateral extent of the shallow groundwater contamination documented at this site. Per <br /> the September 9, 2002 Ground Zero work plan, "Work plan for Well Installation and <br /> Feasibility Study, Second Revision', the borings for the wells were to have been <br /> advanced to total depth of 50 feet below surface grade (bsg), and a minimum of two <br /> water samples collected from each boring, one from an anticipated sand interval at <br /> approximately 26-30 feet bsg, and one from near bottom of each boring depending on <br /> the location of an appropriate permeable interval. Ground Zero made this proposal as <br /> an alternative to completing the vertical assessment of the groundwater contamination <br /> near the source area, and to look for and sample a possible deeper water bearing unit. <br /> However, during the field work this proposal was not carried out. A water sample from <br /> near 50 feet bsg was collected from only one boring, boring B-10 (MW-6), which is <br /> located down-gradient to the source area. This sample contained 25 micrograms per <br /> liter (µg/1)tetrachloroethene (PCE), 2.0 Itg/I trichloroethene (TCE) and 5.5 µg/I cis-1,2- <br /> dichloroethene, indicating that the vertical extent of the groundwater contamination has <br /> not been defined, nor the lateral extent at depth. <br /> Review of the recent quarterly groundwater monitoring and sampling report indicates <br /> that the issues at this site continue to be the presence of free product motor oil in <br /> monitoring well MW-3, located in the former tank pit area, and various volatile organic <br /> compounds, specifically PCE and TCE, present in all site wells. The highest <br /> concentrations of these compounds are in wells MW-7 and MW-6, indicating there may <br /> be an offsite source contributing to the plume. <br />