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Alk City of Stockton Police Facility/Site Code 1178 �� W4 Soil Remediation Plan May 21, 1992 Page 2 Services, Environmental Health Division (SJCPHSEHD) 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/monitoring well was located as close as possible to the area of suspected soil contamination between product line samples #2 and #3. The location of the well is shown on Figure 2. The laboratory analysis of 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 laboratory test results for these samples and previous product line samples (#1 to #4) are summarized in Table 1. 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 MW1, 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. 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. The results of field PID readings and laboratory analyses of soils collected from a shallow (6 ft) trench and the well boring (MW1) located adjacent to the documented source, indicate that limited hydrocarbon contamination has occurred as a result of leakage of unleaded gasoline to the subsurface. The highest concentration of total petroleum hydrocarbons (800 ppm in sample #2) was recorded in the 6 foot soil sample collected nearest to the hole found in the unleaded product line. The non-detectable TPH concentration in the six foot product line samples SRP51992.TJL