SITE INFORMATION AND CORRESPONDENCE 1995-2004

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James L. Tjosvold, P.E. August 7, 1996 Page 4 Response: 2. We are not aware of any compelling need to incur the considerable expense of changing the air photo-based site maps used for the past eight years on this project. Those specific labels which are judged difficult to read due to their placement in a dark area should be identified so that they can be modified. The air photo maps indicate much more detail--not extraneous components--than CAD drawings, and are very useful for locating soil borings, wells, and source areas in the field. The photo maps have also been useful during interpretation of source area definition which could not be accomplished using a CAD drawing. Specific Comments 1. Page ES-1, Executive Summary The report states that: (1) the extent of PNAs in Zone B has been confirmed beneath Area I and will continue to be monitored; (2) PNAs upgradient and downgradient were at about the same concentration: (3) PNAs in Zone B may not originate from the PG&E site; (4) PNA concentrations 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 H. It is not clear what is meant by "The extent ofPNAs 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 H. 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. Response: "The extent of PNAs in Zone B has been confirmed beneath Area I"means that the downgradient edge had not been determined previously and was assumed to be beneath Area I. As discussed in our conference call on June 24, 1996, Linda Turkatte of San Joaquin County has informed PG&E of former service stations and potential petroleum release sites that existed in the vicinity of the PG&E property,the closest of which are indicated on Figure 2-4 of the Phase IV report. The enclosed table,titled "PNAs in TPH-Diesel", indicates that PNAs are found in diesel fuels. The literature indicates that diesel fuels (and other fuels such as gasoline) are variable in nature depending on the specific processes involved and the nature of the end uses of these fuels. As such,the amount of aromatic compounds in diesel