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AZAW' ►� 1992 Third Quarter Report,Site Code 1178 City of Stockton,Police Facility October t4, 1992 Page 2 these leak indicators the San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) required further investigation to assess the extent of contamination On October 19, 1989, a soil boring was drilled to a total depth of 55 feet below grade to determine the vertical extent of hydrocarbon impacted soils and to facilitate the installation of a groundwater monitoring well (MW1) The soil boring/monitonng well was located in as close proximity as possible to the area of suspected soil contamination between product line samples #2 and #3 The locations of the monitoring well and initial soil samples are shown on Figure 2 Laboratory analyses of soil samples collected at five foot intervals from 10 0 to 40 0 feet in the well boring did not detect the presence of gasoline constituents above the method detection limit The depth to first groundwater beneath the site was recorded at approximately 38 feet below grade Analysis of groundwater samples collected subsequent to the development of MW 1, indicated groundwater was not impacted by petroleum hydrocarbons Monitoring well MW1 was sampled again in March, 1992 and was found to be free of gasoline constituents iAn additional investigation was requested by the SJCPHS in a letter dated August 13, 1991, including a submittal of a soil remediation plan to address the soil contamination remaining in place On behalf of the City, RESNA submitted a workplan (May 21, 1992) to remove the remaining hydrocarbon impacted soils at the site The workplan was approved by PHS/EHD in correspondence dated June 11, 1992 FIELD ACTIVITIES Excavation Pursuant to RESNA's May 21, 1992, workplan, excavation activities were initiated on July 23, 1992, under the direction of RESNA The excavation was performed by Falcon Energy Associates (Falcon Energy, license #584524) using a backhoe tractor Excavated soils were field screened using a photoionization detector (PID) to measure volatile - organic vapors Hydrocarbon impacted sods were detected outside the previously estimated - horizontal and vertical limits of impaction Continued excavation activities encountered concrete-encased electrical lines trending northwesterly (Figure 3) Due to safety considerations the soil under the concrete encasing was not removed QRTLYRPTIQR090292 FNL