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the placement of the annular seal. Monitoring well completion details are shown on Figure 5. Following well installation each monitoring well was developed using a pneumatic pump. Stabilization of electric conductivity, pH, and temperature was measured to ensure that samples collected were representative of formation water. Prior to well development depth to water was measured to determine gradient direction and rate of movement (Figure 6). Using the monitoring wells that were drilled on site during this investigation, the groundwater gradient is in a east -southeasterly direction at 0.002 feet/feet. Table 1 summarizes depth to water and monitoring well elevations. The development water will remain on-site, in secured 55 gallon drums until laboratory results are received. Tab.' Le 1. Groundwater Elevation and Depth to Water, March 28, 15 DATE WELL I D. DEPTH TO WATER {FT } ELEVATION* 03/28/91 CPMW-1 4 925 1 075 CPMW-2 4 715 1 285 CPMW-3 4 815 1 185 * Based upon Assumed Datum of 6 feet from west Stockton 7 5 min Quadrangle Map 191. Groundwater samples were collected using a sterile Teflon bailer, labeled and transported to the laboratory under strict chain -of - custody procedures. Samples were analyzed by state -certified Applied Analytical Environmental Laboratories. 5.0 LABORATORY ANALYSIS - SOIL During drilling of the monitoring wells soil samples were collected at 10.5 feet below grade, the soil/groundwater interface, for laboratory analysis. Soil samples were collected at five feet below grade in the former tank pit borings. Soil samples were analyzed for benzene, toluene, ethylbenzene, and total xylenes (BTEX) using EPA method 8020, TPHG and TPHD using modified EPA method 8015, total lead using EPA method 7420, and total soluble lead using EPA methods 1310/3010/7420. According to laboratory analyses, benzene, TPHG and TPHD concentrations were below method detection limits in the soils of wells CPMW1, CPMW2, CPMW3, and boring CPSB2. Petroleum hydrocarbons were detected only in boring CPSB1, the former diesel tank pit area. Because total lead was detected above state action levels, the soil of CPMW2, CPMW3, and CPSB1 were also analyzed for total soluble lead. Total soluble lead levels were below state action levels for all analyzed samples. A summary of laboratory analyses is presented in Table 2 and laboratory reports with chain - of -custody documents are presented in Appendix III. Corrigan Property - 381 3 R0691 TLP