SITE INFORMATION AND CORRESPONDENCE

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Ms. Katie Hower SECOND DRAFT Chevron Pipe Line Company 24 January 1997 Page 3 chart format(Figure 2); analytical requirements are discussed in the next section. The data requirements for each of these stens may be met by using historical site data a new data collection program. or by a combination thereof ^«e„ epnted > , assume dat r r� eelleetion for a newly diseevered site; eikisting data fiam an aetive site will be ineei-7parated into these steps 1. TheT'nefi*&4he lateral and vertical extent of affected soil shall be defined and ebtais preliminary(or screening level) groundwater information shall be obtained using either historical or newly acquired data Q-ps^'"'„b s""" ate.. ^ ndi«ions using soil boring/grab groundwater sampling method is acceptable to provide this data. petroleum-affected area must be clearly constrained. Several gFab-groundwater samples will be collected immediately downgradient of affected soil(if gradient direction is known). If gradient direction is unknown,grab-groundwater samples will be collected from locationsplaeed such that a plume would be detected(if one exists). AUnless field eenditions require otea groundwater samples will net-be collected from within the affected soil area e to The potential is for substantial-interference�to the groundwater measurements by petroleum-affected particulates andZar biogenic byproducts wille addressed using filtering and/or silica gel cleanup stepL(see following discussion). 2. If allgFab groundwater sample results are non-detect or less than RWQCB Water Quality Objectives (WQOs), then refer-the site will be identified as a"soil only” (vadose zone) case and to-the County Health Department (or equivalent) will rn Ovide regulatory oversight. potential risks to human health posed by residual petroleum in soil will be evaluated under appropriate land use scenarios.