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18 . Elevated levels of heavy metals arsenic, chromium, lead and <br /> nickel were also detected in many downgradient wells in the <br /> August 1991 quarterly sampling round. These metals are <br /> included as Chemicals of Concern for Operable Unit No. 1 <br /> (OU 1) and should be discussed more fully in this Work Plan. <br /> UNDERGROUND STORAGE TANKS <br /> Generally the RI/FS Work Plan, Field Sampling Approach for <br /> further characterization of the possible adverse environmental <br /> impact of the onsite underground storage tanks (USTs) is <br /> technically adequate. The field sampling methodology, numbers <br /> and locations of samples, and quality assurance and controls are <br /> outlined according to appropriate State of California Tri- <br /> Regional Board Staff Recommendations for Preliminary Evaluation <br /> and Investigation of Underground Tank Sites (1990) . However, <br /> there are some areas of the Work Plan which are contradictory or <br /> inadequately detailed as described below: <br /> 19 . As previously discussed there is a lack of background data <br /> available for total metals. These background levels, <br /> particularly for metals such as lead, are essential for <br /> evaluating the results of soil and groundwater analyses in <br /> the UST investigation. <br /> 20. Based on the age of most of these USTs, both soil samples <br /> and groundwater should be analyzed for at least the metal <br /> lead as a gasoline constituent. Based on the results of <br /> past investigations at the site, it would also seem <br /> reasonable to analyze all soil and groundwater samples for <br /> VOCs. <br /> 21. During field sampling of soils "an organic vapor analyzer <br /> [OVA] or equivalent" (i.e. Section 3 . 1.7 . 3 . 1. 3) will be used <br /> for "qualitative indication of the presence of hydrocarbon <br /> contamination. " This is an acceptable practice so long as <br /> the soil samples are also analyzed for all appropriate <br /> constituents with a level of quality control sufficient to <br /> attain an EPA Analytical Level IV for risk assessment. <br /> Field screening with an OVA is not to be used as a tool to <br /> determine which samples are analyzed. <br /> 22 . Table 3 . 1-1 does not list UST No. 16 or 21. UST No. 16 is <br /> shown on Figure 3 . 0-17, however, it is not included either <br /> in the text description of USTs or in any of the relevant <br /> tables. State when UST No. 16 was installed and removed, <br /> and what was stored in UST No. 16. There is no mention of a <br /> UST No. 21. Explain why was this number was skipped. <br /> Explain is there was a UST No. 21. If so, an installation <br /> and use history is needed. <br /> 23 . Site location No. 59 is described in the text (3 . 1. 0. 4) as <br /> I-6 <br />