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FINAL DRAM' CONFIDENTIAL ATTORNEY/CLIENT WORK PRODUCT the soil during the drilling of VP4 (adjacent to ASBA), and it was not thought necessary by the County to drill a confirmation boring at this location. I - 2) Due to the probable necessity of shoring the" excavation, no sidewall confirmation samples will be collected. Explanation: Sampling of the existent soil borings has provided'sufficient data to defuse the extent of contamination and therefore will provide confirmation that excavation has been J successful in removing same. y . n 3) The excavation will be carried to a depth of 25 feet below grade. At the option of the Responsible Party the excavation may be deepened. Explanation: Using conventional..earthmoving equipment, extending the excavation below 25 feet would require ramping. The dimensions of the site and:proximity of buildings and roadways would make this a time consuming and expensive proposition for a limited incremental benefit. Contaminant concentrations in general beneath 25 feet are considerably lower than those nearer the surface. Morever, San Joaquin County Flood Control District maps for spring 1986 (generally considered representative of a high water year) indicate that the historical seasonal high groundwater at the site isoapproximately 25 feet below grade. Given the fact that groundwater beneath the site is impacted by petroleum hydrocarbons it is likely that soils below 25 feet will be recontaminated during high water years. Soil beneath this depth can appropriately be dealt with as a facet of groundwater remediation. . F 4) Upon completion of excavation, as outlinedabove, San Joaquin County will issue closure for the soil contamination portion of the.,irivestigation/remediation at the site. No further investigation or cleanup will be required for'soil� however the Responsible Party will continue with the required groundwater remediation. At this point we ask you to consider whether San Joaquin County can agree in principal to the suggestions outlined above for soil closure. 'If it appears that this may be possible we would suggest a meeting to agree on specifics. In theeinterim, soil vapor extraction will continue.in order to further reduce contaminant concentrations.