SITE INFORMATION AND CORRESPONDENCE

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MMUSanta Fe Pacific Pipeline Partners, L.P. J-6075 LW July 13, 1992 Page 2 Because groundwater is only about seven feet below ground surface (BGS), and potholling to about four feet BGS is necessary for utility clearance, one sample taken at approximately five feet will be sufficient to assess the presence of hydrocarbons in the unsaturated zone. One soil sample will be collected for analysis at the top of the first encountered water-bearing zone estimated at about seven feet BGS. The analysis of this sample will provide information in regard to the presence or absence of petroleum hydrocarbons near the water table. Because we are attempting to determine the presence of light hydrocarbons which have a tendency to float, one sample taken near the bottom of the saturated column within the depth of investigation (25 feet BGS) will give the necessary vertical hydrocarbon concentration gradient information needed for this investigation. The PID will be used to field screen the samples collected. Offsite Subsurface Assessment The Port of Stockton, in conjunction with the Technical Committee are in the process of conducting an assessment for the entire Port of Stockton; therefore, offsite work has not been included within the scope of this preliminary investigation. Boring I Monitoring Well Placement Between M-1 & EB-3 We will place an exploratory boring (EB-4) between existing monitoring well M-1 and proposed boring EB-3 for further definition of potential hydrocarbon impacted soils in that area. The soil samples obtained for chemical analysis from this boring will then be placed on hold by the analytical laboratory. If the chemical analysis of the soil samples collected in borings EB-1, EB-2 or EB- 3 indicate the soils are impacted by hydrocarbons, the samples from boring EB-4 will be analyzed to further assess the impact in that area. Our rationale is that the area where EB-1 and EB-2 are proposed is the most likely source area of onsite hydrocarbon impact. If we find this area not significantly impacted, then the possibility of an onsite source and downgradient migration of hydrocarbons is reduced. A site plan showing existing and proposed exploratory borings and monitoring wells is attached to this letter. Monitoring Well Installation Between M-3 & M-6 We will move the location of proposed well M-6 along the northwest property boundary to help identify the presence of potential upgradient hydrocarbon sources as requested by the RWQCB. The proposed monitoring wells M-5 and M-6 should be sufficient to identify the potential for the presence of upgradient sources.