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PUBLICHEALTH SEMCES <br /> SAN JOAQUIN COUNTY <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Karen Furst, M.D., M.P.H., Health Officer •., P <br /> 304 East Weber Avenue,Third Floor • Stockton, CA 95202 <br /> 209/468-3420 <br /> AUL 0 500 <br /> KAREN PETRYNA <br /> EQUIVA SERVICES LLC <br /> PO BOX 7869 <br /> BURBANK CA 91510-7869 <br /> RE: WATERLOO SHELL SITE CODE: 1760 <br /> 4315 WATERLOO ROAD <br /> STOC'KTON CA 95205 <br /> San Joaquin County Public Health Services,Environmental Health Division(PHS/EHD)has reviewed <br /> Grawzi=terMonit%ing Report-Sewnd Quarter 2001 dated June 18,2001 prepared by Cambria Environmental <br /> Technology,Inc. The concentration of methyl tertiary butyl ether(MTBE)detected in the ground water <br /> samples collected from monitoring well MW-1 continued to rise since Apra 2000. <br /> 04/18/2000 07/27/2000 1 10/19/2000 01/16/2001 04/12/2001 <br /> MW 1 16.8 44.1 1 65.9 1 136 164 <br /> All units are in micrograms per liter(µg/1) <br /> MW-1 has been the only groundwater monitoring point installed at the site to date. The oxygenate compounds <br /> di-isopropyl ether,ethyl tert-butyl ether,tert-amyl methyl ether,and tert-butyl alcohol,as well as 1,2- <br /> dichoroethane(1,2-DCA) and 1,2-dibromoethane (EDB)were analyzed for but not detected in a groundwater <br /> sample collected from MW-1 on October 22, 1999. Groundwater samples collected during subsequent <br /> sampling events have been analyzed for MTBE only. <br /> The vertical extent of soil contamination has not been defined at this site. The lowest historical groundwater <br /> elevation in the area,according to San Joaquin County Flood Control's Lines of Equal Depth to Groundwater <br /> publication for 1979,is between 80 and 90 feet below surface grade (bsg). Therefore,the investigation to <br /> define the vertical extent of contamination in soil should extend down to a depth of at least 90 feet bsg. The <br /> vertical and lateral extent of contamination in groundwater has not been defined at this site either,based on the <br /> previous investigation and quarterly sampling analytical results of MW-1. Therefore,additional groundwater <br /> investigation of the contamination is required. <br /> Submit a work plan that will define the vertical and lateral extent of soil and groundwater contamination at this <br /> site to PHS/EHD by August 10,2001. The analytical suite for groundwater should include all five oxygenates <br /> and 1,2-DCA and EDB,which are included in the EPA Method 8260B analysis. PHS/EHD recommends <br /> installing monitoring wells and utilizing appropriate borehole technologies such as cone penetrometer <br /> technology or continuous core sampling in order to understand the lithology and its control on migration of <br /> petroleum hydrocarbon contamination. If you have any questions please contact Jeffrey Wong at(209)468- <br /> 0335. <br /> Donna Heran,RENS,Director <br /> vironmental Health Division " <br /> effrey Wong,Senior REHS Dot Lofstrom, G <br /> LOP/Site Mitigation Unit IV LOP/Site Mitigation Unit IV <br /> cc: RWQCB,Central Valley Region-Marty Hartzell <br /> cc: Cambria-Joe Neely <br /> A Division of San Joaquin County Health Care Services <br />