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Pacific Gas and Electric Company Environmental Services <br /> P.O.Box 7640 <br /> San Francisco,CA 94120 <br /> March 9, 1992 415/973-7000 <br /> Direct Dial 415/973- <br /> Telecopy 415/973-9201 <br /> Mr. Val F. Siebal <br /> California Environmental Protection Agency MAR 1 7 1592 <br /> Department of Toxic Substances Control L HEALTH <br /> 10151 Croydon Way ENVIRO . <br /> r Sacramento, CA 95827 <br /> Attention: Mr. James Tjosvold <br /> Mr. Fernando Amador <br /> Dear Mr. Siebal : <br /> Re: Docket #HSA 90/91-08 - Stockton Manufactured Gas Plant Site <br /> Subject: Response to February 11 Comments on RI/FS Workplan <br /> This letter provides PG&E's responses to your comments of February 11 , <br /> 1992, regarding the Stockton RI/FS Workplan, and serves to amend the <br /> Workplan. The two comments are treated separately below. <br /> 1 . Sampling Locations - Area II . DTSC requested additional information <br /> to justify sampling locations in Area II, and that such information be <br /> used, together with the results of shallow subsurface samples to assess <br /> the need for further sampling in that area. <br /> Area II has operated as an electrical substation for almost 100 <br /> years, first by Western Gas and Electric prior to 1930 and by PG&E <br /> subsequent to its purchase during that year. PG&E has conducted a <br /> records review, and has provided the information pertinent to the <br /> historical chemical use and land use in Area II in the work plan and its <br /> addenda. This information, together with aerial photographs from 1937 <br /> to 1971 and historical site plans, were reviewed with Mr. Fernando <br /> Amador on December 18, 1991. Activities at the substation are well- <br /> documented from 1930 or earlier. We believe that the absence of any <br /> operating records or other records showing chemical handling at Area II <br /> is because such activities were not performed in that area. PG&E has <br /> over 1100 restricted access substations, and in our experience <br /> substations are seldom used for chemical handling, treatment, or <br /> storage. <br /> During our February 18 meeting, Mr. Amador indicated that the <br /> spatial relationship between the sampling locations and current or <br /> historical site features was not clear. PG&E has proposed to create a <br /> photographic base map of the substation correlating site features and <br /> sampling locations. Because this map will not be available for <br /> approximately one month, PG&E and CH2M Hill conducted a site tour for <br /> Mr. Amador on February 24. <br /> The results of the chemical analyses of near surface soil samples <br /> from Area II were reviewed with DTSC during the February 18 meeting. <br />