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1 <br /> PUBLYC HEALTH SETVICES ,oPU I f4 �o <br /> SAN JOAQUIN COUNTY q �� <br /> JOGI KHANNA M.D..M.P H. "1 <br /> Health Officer •-P <br /> P.O. Box 2009 0 (1601 East Hazelton Avrnue) • Stockton, California 95201 <br /> (209) 468-3400 <br /> } <br /> l <br /> RIC NOTINI j <br /> DIRECTOR OF ENVIRONMENTAL SERVICES i <br /> CATELLUS DEVELOPMENT CORPORATION <br /> 201 MISSION STREET 30TH FLOOR h J U L 2 71992 <br /> SAN FRANCISCO CA 94105 <br /> RE: Catellus Development Property SITE CODE: 1284 <br /> 1325 West Weber St. <br /> Stockton, CA 95243 <br /> APN 145-190-16 <br /> San Joaquin County Public Health Services Environmental Health Division (PHS/EHD) <br /> has completed review of the "Supplement to the Interim Preliminary Assessment Report <br /> for the Former Tank Site #2" dated June 5, 1992 and the "Quarterly Monitoring Report" <br /> dated July 14, 1992. PHS/EHD has the following comments for your consideration. i <br /> Unusual hydrogeologic conditions were encountered during the March 1992 drilling of J! <br /> monitoring wells, MW1A - MW4A. Groundwater was 'initially encountered at depths of <br /> 19 feet during the drilling of MW3A and MW4A. Groundwater was encountered at 9.5 <br /> feet during the drilling of MW1A and at 3.5 feet during the drilling of MW2A. The <br /> report concluded that groundwater encountered at 3.5 feet was a perched zone and that + <br /> groundwater encountered at 19 feet was a part of a confined 'aquifer. It is generally <br /> accepted that the aquifer is not confined. If,however,itis confined, MW3A and MW4A <br /> would be not be placed in the first aquifer. <br /> Regardless of the confinement of the aquifer, the placement of the screened interval <br /> within MW3A and MW4A, is not in a position to evaluate petroleum contamination since <br /> petroleum contaminants have lighter densities than water and are considered "floaters". <br /> Once petroleum contaminates reach the water table they generally float on the top of the <br /> water and migrate with the water as it moves in its flows path.; Once gradient is <br /> confirmed it will be necessary to install an additional do gradient monitoring well to <br /> establish the boundaries of contamination. <br /> The chain of custody for soil sampling during the drilling of1VIW4A on March 28, 1992 <br /> was not included in the Supplement report. Please submit this chain of custody with the <br /> next quarterly report. <br /> A Division of San Joaquin County Health Care Services <br />