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1117 Lone Palm Avenue <br /> Suite B <br /> 'VAT(: Modesto, CA 95351 <br /> 209.579.2221 <br /> Fax 209.579.2225 <br /> A S S O C I A T E S I N C - ' <br /> December 22, 1999 <br /> 54.62574.0005 <br /> Ms. Lori Duncan <br /> San Joaquin County Public Health Services <br /> Environmental Health Division <br /> 304 E. Weber Street, Third Floor <br /> Stockton, California 95202 <br /> Subject: Monitoring Report Fourth Quarter 1999, City of Stockton Fire Station No. 3, <br /> 1116 First Street, Stockton, California <br /> Dear Ms. Duncan: <br /> This report presents the results of quarterly groundwater monitoring and sampling performed on <br /> December 2, 1999 by ATC Associates Inc. at the site located at 1116 First Street, Stockton, <br /> California (Figure 1). Monitoring was performed to determine the groundwater flow direction <br /> and the hydraulic gradient in the uppermost aquifer. Sampling was performed to monitor the <br /> distribution of petroleum hydrocarbons in groundwater at the site. <br /> SITE HISTORY <br /> One gasoline underground storage tank (UST) of unknown size, and all associated piping and <br /> dispensing equipment were removed and transported from the site. Laboratory analysis of soil <br /> samples collected from beneath the former UST location indicated the presence of detectable <br /> concentrations of total petroleum hydrocarbons. After the tank was removed, the area of the <br /> former tank was backfilled. Following tank removal activities, four soil borings (SP-1 through <br /> SP-4) were advanced in the immediate vicinity of the former UST. Analytical results indicated <br /> that soil impacted with petroleum hydrocarbons extended to approximately 28 feet below ground <br /> surface (bgs). The approximate locations of the former UST and soil borings are shown on <br /> Figure 2. <br /> On July 20, 1998, Advanced GeoEnvironmental Inc. (AGE) supervised the advancement of one <br /> soil boring, NMI, through the former UST excavation to a depth of 65 feet bgs. The boring was <br /> completed as a two-inch diameter monitoring well screened from 45 to 65 feet bgs. Analytical <br /> results of soil samples indicated the presence of petroleum hydrocarbons at 20 feet bgs but the <br /> impacted soil appeared to attenuate rapidly with depth. The monitoring well was developed and a <br /> groundwater sample was collected from the well although water was measured to be above the <br /> w:\62574\62574.05keports\4qr-1999.doc 1 <br />