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Mr. Fernando Amador -2- 2 July 1996 have been generally decreasing over time; (5) PNAs were also detected in Zone B beneath Area H of the site; and (6) other historic sources of petroleum hydrocarbons (former service stations) were located near Area II. It is not clear what is meant by "The extent of PNAs in Zone B has been confirmed beneath Area I." The simple fact remains that the extent of PNA contamination in Zone B has not been defined. It is also not clear if the report is suggesting that the former service stations located near Area II are the source of PNAs in Zone B beneath Area II. PG&E should compare the PNAs present in fuel petroleum hydrocarbons with those present in the ground water beneath Area II to determine the latter's origin. If the PNAs present in ground water are not PNAs which are associated with fuel petroleum hydrocarbons, then PG&E is the likely source of ground water contamination in Zone B in Area II. 2. Page ES -2, Executive Summary The report states that PNAs were detected in hydropunch samples from Zone A in MW -14 and from Zones A and B in MW -15 during the drilling of these Zone C wells. The report also states that since these wells are upgradient of the site, there could be upgradient sources of the PNAs in ground water. However, the presence of PNAs in ground water in Zone A at MW -14 and PNAs in Zones A and B at MW -15 has not been confirmed because of the absence of monitoring wells (MWs) at these locations. Furthermore, all the MWs which show PNA contamination around PG&E could have been contaminated by PG&E due to ground water elevation fluctuations and flow reversals. Some evidence of flow reversal is shown in Table 3-4. In addition, the MWs at the Fire Department (northwest of PG&E) show a Zone A ground flow direction to the northeast which differs from PG&E Zone A ground water flow direction which is predominantly to the east. This could be an artifact of flow reversal or some hydrogeologic condition which results in different ground water flow directions in Zone A. Also, onsite and offsite ground water elevations have only been measured since 1992. The plant started operations in the 1800s. It is likely that ground water flow reversals and fluctuations occurred over the years and could have resulted in the formation of pockets of contamination which are now contributing sources to the overall contamination coming from locations of former MGP structures. For example, MW -14 is only approximately 70 feet west of NT IO '-1R and 1`. IN- D, both of which have PNA contamination. The proximity of MW -14 to onsite MWs showing contamination, the very flat gradient, and the potential for flow reversal suggest that MW -14 has been impacted by onsite contamination. 3. Page ES -2, Executive Summary The report states that there is no current risk from constituents of potential concern (COPCs) in soil or ground water since no complete exposure pathway exists as determined by a risk assessment (RA). This is not an accurate statement because the RA did not consider ground water as a receptor. Since ground water is a receptor and has already been impacted, a complete pathway does exist.