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STATE OF CALIFORNIA - Environmental Protection Ac, -...;Y PETE WILSON, Govemor <br />CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD <br />CENTRAL VALLEY REGION °F`"" <br />3443 Routier Road, Suite A --- <br />Sacramento, CA 95827-3098 <br />PHONE: (916) 255-3000 <br />FAX: (916) 255-3015 <br />2 July 1996 <br />Mr. Fernando Amador <br />Department of Toxic Substances Control <br />10151 Croydon Way, Suite 3 <br />Sacramento, CA 95827-2106 <br />COMMENTS ON PHASE IV GROUND WATER INVESTIGATION REPORT, PG&E <br />FORMER MGP STOCKTON, SAN JOAQUIN COUNTY <br />I have reviewed the June 1996 Phase IV Ground Water Investigation Report for PG&E's former <br />manufactured gas plant (MGP) in Stockton. PG&E conducted the Phase IV investigation to evaluate the <br />extent of polynuclear aromatic compounds (FNAs) and benzene in Zones A and C and confirm the extent <br />of PNAs and benzene in Zone B. My comments on the report are presented below. <br />General Comments <br />The report's authors and their qualification are missing. California Business and Professions Code <br />Sections 673 5, 7835, and 7835:1 require that engineering and geologic evaluations and judgements <br />be performed by or under the direction of registered professionals. Therefore, the cover sheet <br />should be signed by at least one registered professional who is responsible for the investigation <br />report. <br />2. The site maps using air photos should be changed with regular computer aided drawing (CAD) <br />maps. The air photos are appropriate when identifying former structures which could be potential <br />sources of contamination. Once these structures have been identified, a CAD map (incorporating <br />these structures) with a convenient scale should be used. The air photo map has extraneous <br />components which really do not add value to the information being presented but in fact blur the <br />picture because of the shadows. When using air photo maps, labeling the essential components also <br />presents a problem because of the varying shades of light and dark. Sometimes labels are placed in <br />dark areas and are difficult to read. <br />Specific Comments <br />Page ES -1, Executive Summary <br />The report states that: (1) the extent of PNAs in Zone B has been confirmed beneath Area I and will <br />continue to be monitored; (2) PNAs upgradient and downgradient were at about the same <br />concentration; (3) PNAs in Zone B may not originate from the PG&E site; (4) PNA concentrations <br />