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it <br /> PUBLIC HEALTH SERVICES ,o.�uIN . <br /> SAN JOAQUIN COUNTY =' : <br /> ENVIRONMENTAL HEALTH DIVISION " ` <br /> Karen Furst, M. D . , M.P.H. , Health Officer <br /> • �7P <br /> � . . W <br /> 304 East Weber Avenue, Third Floor • Stockton, CA 95202 Foo <br /> 209/468-3420 FILE COP Y <br /> PAUL SUPPLE JUN 181998 <br /> ARCO PRODUCTS COMPANY <br /> P O BOX 6549 <br /> MORAGA CA 94570 <br /> RE : ARCO #548 SITE CODE: 1127 <br /> 1612 Hammer Lane <br /> Stockton , CA <br /> San Joaquin County Public Health Services , Environmental Health Division ( PHS/EHD) <br /> has reviewed the "Underground Storage Tank and Product Delivery Line Removal" <br /> report dated April 30, 1998, the "Quarterly Groundwater Monitoring" reports dated <br /> February 5 , 1998 and May 19 , 1998, and a letter dated May 4, 1998 , all prepared by <br /> Pinnacle Environmental Solutions for the above referenced site. In addition , soil sample <br /> results presented in past reports were reviewed . <br /> Soil contamination was evidenced to 45 feet below surface grade (bsg) in 1991 when <br /> soil samples were collected during drilling of soil borings . The vertical extent of soil and <br /> groundwater contamination should be defined on site near the former underground <br /> storage tanks ( UST' s) location . With the definition of on site contamination , the <br /> proposed investigation of off site contamination can be evaluated and changed if <br /> necessary. <br /> Current water level bsg is above the top of the screened interval of all the monitoring <br /> wells installed on and off site . Monitoring wells which intercept the current water level <br /> and vadose zone should be installed . <br /> It has been proposed to destroy monitoring well (MW) 3 and not replace it because <br /> MW2 is downgradient from the source areas . The analysis of soil samples collected <br /> beneath the piping and dispensers, at the time of their removal , at locations PL3, PL10 , <br /> PL13 and D1 revealed contamination in these areas . MW2 is 90 to 100 feet from these <br /> locations , further soil investigation in these areas and installation of a monitoring well <br /> close to these locations will be required . Since we don't know when the release of <br /> petroleum occurred in these locations the information from borings B13 and B15 is not <br /> sufficient. <br /> Methyl-tert butyl ether (MTBE) was evidenced in the analysis of soil samples collected <br /> beneath the UST's and the above discussed piping/dispenser areas . Tertiary butanol <br /> was evidenced in the analysis of a soil sample from a stockpile. This stockpiled soil was <br /> used to fill the UST excavation . Since there are no operating UST's at this site or in the <br /> immediate vicinity , PHS/EHD will agree to analysis of the groundwater samples from the <br /> current monitoring wells for MTBE using EPA method 8020. <br /> A Division of San Joaquin County Health Care Services <br />