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PUBLIC HgALTH' SERVICMS Cu, <br /> a.�,N .� <br /> SAN JOAQUIN COUNTY = ; <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Karen Furst, M.D., M.P.H., Health Officer <br /> 304 East Weber Avenue, Third Floor • Stockton, CA 95202 <br /> 209/468-3420 <br /> ANDY EGGIMAN SEP 2 0 20M <br /> C/O ROBERT EGGIMAN <br /> PO BOX 580 <br /> MOUNTAIN RANCH CA 95246 <br /> Re: Eggimans Hydraulic Site Code: 1914 <br /> 1112 E. Harding Way <br /> Stockton, CA 95205 <br /> San Joaquin County Public Health Services Environmental Health Division (PHS/EHD) <br /> has reviewed the Summary Report of Supplemental Subsurface Investigation (report) <br /> dated September 8, 2000 prepared by ATC Associates, for the above referenced site. <br /> Soil and groundwater samples collected at the site evidence petroleum contamination. <br /> Further site investigation to determine the lateral extent of soil contamination and the <br /> lateral and vertical extent of groundwater contamination is necessary. <br /> Total petroleum as gasoline, benzene, toluene, ethylbenzene, and xylene contaminants <br /> were evidenced in water in concentrations of 4,700 parts per billion (ppb), 24 ppb, 120 <br /> ppb, 480 ppb, and 520 ppb, respectively. Methyl-tert-butyl ether(MTBE) was <br /> evidenced in a groundwater sample collected at the site at concentrations as high as 270 <br /> parts per billion(ppb). The maximum contaminant level for MTBE is currently 13 ppb. <br /> Concentrations of contaminants in the groundwater must be confirmed by utilizing <br /> repeatable sampling points to obtain representative groundwater samples. <br /> Monitoring wells must be constructed at the site to evaluate the groundwater conditions <br /> and to establish the groundwater gradient. Monitoring wells should be screened at an <br /> interval that is representative of the affected groundwater. Groundwater samples must be <br /> analyzed quarterly for total petroleum hydrocarbons as gasoline by EPA Method 8015; <br /> benzene, toluene, ethylbenzene and xylene by EPA Method 8020; and for oxygenates, 1,2 <br /> dichloroethane, ethylene dibromide, methanol and ethanol by EPA Method 8260. <br /> MTBE groundwater plumes can be long, narrow, and erratic (meandering). Because of <br /> the migratory nature of MTBE and the potential for pumping influence from wells <br /> located near this site, it is particularly important to determine the lateral extent of this <br /> contaminant in the groundwater. If further site evaluation reveals MTBE to be a <br /> significant problem, it may be necessary to construct additional monitoring wells and/or <br /> monitoring well clusters in transect or perpendicular to the MTBE plume. <br /> A Division of San Joaquin County Health Care Services <br />