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�3"...L..- 5��,� T�„'- x ,, .;�� n�. �' '`s ..rte.' :��. .,•a1 ,.'< .a 3 -;t Y o-Y+ 1 site and aerated in accordance with the San Joaquin Local Health District approved soil remediation work plan of December 7, 1988 and the January 19, 1989 and March 2, 1989 amendments to the soil remediation workplan. To assess the extent of chemicals in the soil and groundwater beneath the site, fifteen soil borings, ten of which were completed as shallow groundwater monitoring wells, were installed by McLaren Engineering between May 15 and June 2, 1989. The borings and monitor wells were completed to characterize the lateral and vertical extent of soil and groundwater contamination associated with leakage from the former tank. Results of soil analyses showed the presence of petroleum hydrocarbons in concentrations exceeding 100 ppm in the area surrounding the tank excavation. Results of groundwater analyses (see Table l) showed the presence .of benzene in concentrations above the California Department of Health Services (DHS) Maximum Contaminant Levels (MCLs) for drinking watar in four of the ten shallow monitor wells installed during the site assessment. Site assessment findings indicate that remediation of soil and groundwater is required, Specific elements of the proposed remediation are presented below, SOIL REMEDIATION Excavated Soil Remediation A soil remediation Work Plan was submitted to the SJLHD by Sebastiani Vineyards/Woodbridge Cellars on December 7, 1988. In accordance with the Work Plan, excavation work was begun on April 6, 1989 to remove soils contaminated with petroleum hydrocarbons. The amount of soil to be excavated was to be determined with field measurements (HNu photoionization detector). Soils with petroleum hydrocarbon _. concentrations in excess of 100 ppm were to be excavated and stockpiled for aeration. However, field observations suggested that the soil contamination was somewhat more extensive than anticipated and that groundwater may have been impacted. As such, excavation work was suspended to allow evaluation of possible remedial alternatives. Aeration of the soils which had been excavated was begun at two locations (designated Aeration Pile 1 and Aeration Pile 2) at the Woodbridge Cellars facility. Samples were collected from Aeration Pile 1 on May 25, 1989, composited, and submitted for analysis of total petroleum hydrocarbons, specifically gasoline (TPH/C) and benzene, toluene, xylenes, and ethylberzene ($TXE). 4 NNOMMEMBOMM9