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grown and Caldwell( <br /> Consultants <br /> 723 S Street <br /> Sacramento <br /> California 95814q092 <br /> (916)444-oi23 <br /> FAX(916)444-8437 <br /> AUG <br /> August 13, 1991 ENVIRONMENTAL IHEALTI� <br /> P E RNI r 5E V r <br /> Ms. Laurie A. Cotulla, Program Manager <br /> Environmental Health Division <br /> Public Health Services <br /> San Joaquin County <br /> Post Office Box 2009 <br /> Stockton, California 95201 017-3258=03/3 <br /> Subject: Groundwater Elevations and Flow Directions, ARCO Station 6080, <br /> Lathrop, California <br /> Dear Ms. Cotulla: <br /> As a supplement to my letter of July 26, 1991, enclosed are Figures I through 4 that show water- <br /> level elevations and flow directions for ARCO-St-ati-o-n-6080;located,at-85 Easf'Louiiikyenue <br /> in Lathrop, California. As indicated on the figures and summarized below, thegToundwater—flo-W-71 <br /> cd#e(tionT�has,varied-gi-griificAhtly, under a low hydraulic gradient. <br /> Date Flow direction Hydraulic gradient Figure <br /> 4/28/87 SE 0.001 1 <br /> 12/21/87 W-SW 0.0005 2 <br /> 8/26/88 NW 0.003 3 <br /> 5/23/91 SE 0.002 4 <br /> These data indicate there is no single up- or downgradient well; each well is sometimes <br /> upgradient and sometimes downgradient. <br /> As discussed previously, three rounds of groundwater monitoring have indicated that there are <br /> no detectable petroleum hydrocarbons in the groundwater. Furthermore, with the exception of <br /> very low levels of hydrocarbons detected in two soil samples (attributed to minor surface spills <br /> or cross contamination), there is no known source of contamination at the site. Therefore, further <br /> work is not warranted at this site and it is requested that this site be "closed" and removed from <br /> San Joaquin County's list of environmental-impacted sites. <br />