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18 <br /> GROUND ZERO ANALYSIS, INC. <br /> i n✓ <br /> 3422 W Hammer Lane, Suite C-294 ' <br /> Stockton, California 95219 w •. <br /> Telephone. (209) 952-3481 <br /> l+acsunile. (209) 952-9891 <br /> December 11, 1995 <br /> Ms Linda Turkatte <br /> San Joaquin County Public Health Services <br /> Environmental Health Division <br /> P O Box 388 <br /> Stockton, CA 95201-0388 <br /> Subject Former Laidlaw Corporation Facility <br /> 1444 Tillie Lewis Drive, Stockton, California <br /> Site Code 2454 <br /> Dear Ms Turkatte <br /> This letter is submitted on behalf of Laidlaw corporation in accordance with correspondence from San <br /> Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) dated October 31, <br /> 1995 The purpose of this letter is to update PHS/EHD on the status of subsurface <br /> investigation/remediation activities at the subject site The site location is shown on Figure 1 <br /> Site Background <br /> On June 29, 1990, one 4,000-gallon underground xylene storage tank was removed at the protect site <br /> by Semco Corp of Modesto, California Soil samples were collected beneath the tank and analyzed <br /> for benzene, toluene, ethylbenzene, xylenes (BTEX), and total petroleum hydrocarbons as gasoline <br /> (TPHG), by BC Laboratories, Inc , utilizing appropriate EPA and DHS methodologies The presence <br /> of elevated concentrations of xylenes in the tank pit soil samples indicated further investigation was <br /> necessary to determine the lateral and vertical extent of soil and/or groundwater contamination at the <br /> project site <br /> To prevent the contaminated material associated with the former xylene tank from presenting a <br /> continued threat to groundwater, approximately 750 cubic yards of contaminated soils were excavated <br /> from the protect site on March 19 and 20, 1991 Groundwater was encountered at approximately 15 <br /> feet below grade during the excavation Soils within the saturated zone were not excavated <br /> Verification soil samples collected from the excavation side walls indicated that all impacted soil in the <br /> unsaturated zone had been removed except where the excavation was limited on the west side by the <br /> warehouse and access ramp A verification sample collected from the west wall of the excavation <br /> contained only 2 3 parts per million (ppm) xylene Soil analysis and field observations collected from <br /> soil borings MW1 through MW6 confirmed soil contamination was limited to the immediate vicinity <br /> of the former tank pit <br />