SITE INFORMATION AND CORRESPONDENCE

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Former Lyoth Loading Station• _ 2 - • 8 October 1998 Chevron Pipe Line, San Joaquin Co. 4. The lateral extent of TPHc, TPHd, and PAH soil contamination at GP-9 and GP-10 needs definition. Groundwater Sample Results 1. Although crude oil at the site has been described as being very viscous, the occasional detection of TPHd in MW-6,the one-time detection of pyrene in MW-7, and the presence of free phase product in MW-2 show that at some point crude oil becomes soluble and impacts water quality. Since the TPHd levels are relatively low and Chevron has used silica gel cleanup on the samples, we will be able to make a better determination after additional sampling (see Item l.c below). 2. The groundwater sampling program was inconsistent, similar to that described above for soil sampling. GP-3 through GP-10 need to be sampled for TPHd/g using a screening method such as a geoprobe or hydropunch. The results will determine if a monitoring well has to be placed at GP-3 and/or in the vicinity of GP-9 and GP-10. 3. Due to the nature of contamination,the site has several pockets of contaminated areas which are isolated from each other. Therefore, each pocket of contamination requires lateral and vertical definition. The vertical extent of groundwater contamination in the vicinity of MW-2, MW-6, and potentially at MW-7, GP-3, and GP-9/10 needs to be defined. 4. The test method for PAHs is not sufficiently sensitive to allow their detection below the water quality objectives. Mr. Gordon Lee Boggs of the Board's Underground Storage Tanks Unit, in his 25 August 1998 letter to CPL, stated that some PAHs have maximum contaminant levels for drinking water which are below the detection limits, CPL and Board staff agreed that it is difficult to calculate a theoretical mass that may cause a water quality problem, an analysis for total PAHs with speciation for those above the detection limits will provide a base to calculate the total and speciated PAHs that could exceed toxic levels in the groundwater, and both water and filtered material (such as that retained during silica gel cleanup) should be analyzed to determine the total PAHs and speciation. Therefore, PAH testing at this site should follow this procedure. Comparison of Site Data to Chevron's Technical Approach 1. The approach states that the lateral and vertical extent of affected soil shall be defined. As stated in the Soil Sample Results above, some source areas need further definition. 2. The approach states that the lateral and vertical extent of dissolved petroleum hydrocarbons in groundwater will be defined. As stated in the Groundwater Sample Results above,the vertical extent of groundwater contamination in the vicinity of MW-2,MW-6, and potentially at MW-7, GP-3, and GP-9/10 needs to be defined. 3. Step 2 of the technical approach states that if all groundwater sample results,based on preliminary or screening level groundwater information from historical or new data, are nondetect or less than the Board's water quality objectives (WQOs), the site will be identified as a"soil only" (vadose zone) case and will be transferred to the county. Due to the limited vadose zone at the site (0-15 feet), soil contamination extending below the water table, and the presence of separate phase product and dissolved constituents, the site cannot be considered a"soil only" case and should be treated as a"groundwater case".