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1992 Third Quarter Report,Site Code 1178 <br /> City of Stockton,Police Facility <br /> October 14, 1992 <br /> Page 2 <br /> these leak indicators the San Joaquin County Public Health Services, Environmental Health <br /> Division (PHS/EHD) required further investigation to assess the extent of contamination. <br /> On October 19, 1989, a soil boring was drilled to a total depth of 55 feet below grade to <br /> determine the vertical extent of hydrocarbon impacted soils and to facilitate the installation of <br /> a groundwater monitoring well (MWl). The soil boring/monitoring well was located in as close <br /> proximity as possible to the area of suspected soil contamination between product line samples <br /> #2 and #3. The locations of the monitoring well and initial soil samples are shown on Figure <br /> 2. <br /> Laboratory analyses of soil samples collected at five foot intervals from 10.0 to 40.0 feet in the <br /> well boring did not detect the presence of gasoline constituents above the method detection limit. <br /> The depth to first groundwater beneath the site was recorded at approximately 38 feet below <br /> grade. Analysis of groundwater samples collected subsequent to the development of MW 1, <br /> indicated groundwater was not impacted by petroleum hydrocarbons. Monitoring well MW1 <br /> was sampled again in March, 1992 and was found to be free of gasoline constituents. <br /> An additional investigation was requested by the SJCPHS in a letter dated August 13, 1991, <br /> including a submittal of a soil remediation plan to address the soil contamination remaining in <br /> place. <br /> On behalf of the City, RESNA submitted a workplan (May 21, 1992) to remove the remaining <br /> hydrocarbon impacted soils at the site. The workplan was approved by PHS/EHD in <br /> correspondence dated June 11, 1992. <br /> FIELD ACTIVITIES <br /> Excavation <br /> Pursuant to RESNA's May 21, 1992, workplan, excavation activities were initiated on July 23, <br /> 1992, under the direction of RESNA. The excavation was performed by Falcon Energy <br /> Associates (Falcon Energy, license #584524) using a backhoe tractor. <br /> Excavated soils were field screened using a photoionization detector (PID) to measure volatile <br /> organic vapors. Hydrocarbon impacted soils were detected outside the previously estimated <br /> horizontal and vertical limits of impaction. Continued excavation activities encountered <br /> concrete-encased electrical lines trending northwesterly (Figure 3). Due to safety considerations <br /> the soil under the concrete encasing was not removed. <br /> QRTLYRPT1QR090292.FNL <br />