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Kennedy/Jenks/Chilton Mr. Charles Whitworth i Cal-Farm Supply 14 July 1989 Page 13 inside the storage trailers. Recommendations to address these three areas are provided below. Underground -Storage Tank It is our understanding that future use of the Stockton facility by Cal -Farm Supply will not involve utilization of the underground fuel storage tank. Therefore, to bring the tank into compliance with California underground tank regulations, the tank should be removed rather than implement leak protection or monitoring. During excavation and removal of the tank, soil samples should be collected and analyzed for TPD and BXTE to assist in determining the extent of possible leakage from the tank. The presence of benzene in the groundwater is most likely related to leakage of fuel from this tank However, the horizontal and vertical distribution of this chemical in soil and groundwater, specifically in the down gradient direction, was not determined during the ! current investigation. An additional monitoring well may be necessary to obtain this information. A meeting should be held with representatives from the Regional Board (as lead agency) to discuss what additional action is I warranted to address the benzene concentrations in groundwater, if any. Surface Soils Containing Pesticides Surface soil with 4,4`-DDT concentrations above the TTLC of 1,000 ug/Kg should be further investigated to better characterize DDT concentrations in these areas. These areas are highlighted on Figure 7. Options for developing site specific cleanup levels and remediation alternatives are as follows- 0 The "no-action" alternative would result in no further work being performed on the property concerning the DDT soils If this alternative is chosen it is most likely that a deed restriction will be required for this property. ,i J o Rather than using TTLC criteria, cleanup levels could be derived from health-based criteria. This evaluation would consider the intended future use of this property which at the present time is assumed to be industrial . o Remediation of these soils could include excavation, treatment, and backfilling of treated material on site. It should be noted that treatment technologies for DDT are only in the developmental stages and that the EPA has not approved any treatment technology to date. o Another option for remediating these soils could entail excavation and disposal of the soils containing elevated levels of DDT at a Class I hazardous waste facility. At this time disposal of these soil is complicated because wastes containing DDT are included in the