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Ms. Katie Hower SECOND DRAFT <br /> Chevron Pipe Line Company <br /> 24 January 1997 <br /> Page 5 <br /> molecular weight PNAs are the most water soluble petroleum components of <br /> concern„ and RWQCB has WQOs for these constituents. Benzene and the <br /> carcinogenic PNAs are the most toxic constituents potentially associated witb the residual <br /> petroleum. Therefore, both soil and groundwater samples will be analyzed for BTEX and <br /> PNAs. <br /> The measurement of TPH as crude oil in soil by Method 8015M(GC-FID), or equivalent, at <br /> Old Valley Pipeline sites is useful as a site investigation tool, but it is not <br /> used in health risk assessments. The RWQCB WQOs include TPH measurements for gasoline <br /> and diesel products, but not crude oil/Bunker C, in groundwater. Although gasoline and diesel <br /> products are not present at these sites, the RWQCB has made it clear that these WQOs will be <br /> applied to "gasoline-range hydrocarbons" (C4 to C12) and"diesel-range hydrocarbons" (CSO to <br /> C24) found in site groundwater samples. Accordingly, TPH measurements incorporating these <br /> ranges will be performed on site groundwater samples. Because the WQOs are for gasoline <br /> and diesel products, the groundwater samples will be quantified against gasoline and diesel <br /> standards so that the comparison to WQOs is as direct as possible. Groundwater samples will <br /> not be analyzed for fractions greater than C24 or by Method 418.1,; o vInCn has i fia;,,,,tea that <br /> they are not _.,._eemea with the Tnv 4aett:,�-- 0,w,,,..,use of its low Solubility and <br /> do not e^ ..ider Method 418.1 appEopriate measurement f r , ..,1wat„- /1]RlQGB 1996b). <br /> e <br /> Using TPH as WQOs at Old Valley Pipeline sites is problematic because of positive <br /> interferences to the Method 8015M measurement. Based on recent research performed by <br /> Geomatrix(Zemo and Synowiec, 1995; Zemo, 1996; Foote et al., 1996),the TPH <br /> measurement of groundwater samples has been demonstrated to be positively interfered with <br /> by both soluble non-petroleum hydrocarbons resulting from intrinsic biodegradation and non- <br /> dissolved petroleum sorbed to particulates entrained within turbid(not"oily") samples. This <br />