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STATE OF CALIFORNIA—ENVIRONMENTAL PROTEIR AGENCY • PETE WILSON,Governor <br /> DEPARTMENT OF TOXIC SUBSTANCES CONTROL <br /> 10151 CROYDON WAY,SUITE 3 <br /> SACRAMENTO,CA 95627-2106 <br /> (916) 855-7700 <br /> November 25, 1991 <br /> Mr. Robert Doss, P.E. <br /> Project Manager <br /> Pacific Gas & Electric Company <br /> Environmental Services <br /> 77 Beale Street, Room F-1636 <br /> San Francisco, California 94106 <br /> Dear Mr. Doss: <br /> PG&E STOCKTON, DRAFT REMEDIAL INVESTIGATION/FEASIBILITY STUDY <br /> (RI/FS) WORKPLAN <br /> The Department of Toxic Substances Control (Department) has <br /> reviewed your response to our comments issued September 17, 1991 <br /> for the RI/FS Workplan dated August 1991. Our review indicates <br /> that several comments have not been adequately addressed. To <br /> keep from delaying the project, the Department hereby approves <br /> the RI/FS Workplan contingent upon the remaining comments being <br /> addressed. Implementation of the workplan shall commence upon <br /> receipt of this approval. The following are the remaining <br /> comments: <br /> 1. Investigation of Area II should not focus just on gas plant <br /> residues which may exist in the vicinity of the gas holder. <br /> The investigation should be designed to detect any <br /> contaminant residue which may exist due to the handling or <br /> use of hazardous materials or wastes in Area II . Research <br /> of historical records for Area II must be conducted to <br /> identify additional locations of concern where contaminants <br /> may exist and to justify the sampling criteria selected such <br /> as type, number, depth, location of samples, and target <br /> constituents. Locations of concern should include the gas <br /> holder, the street R.R. powerhouse, and any other location <br /> that may have stored, handled, used, or released hazardous <br /> materials or wastes. The sampling plan must include the <br /> rationale for the sampling activities proposed. Include a <br /> map to indicate the location of the proposed samples. <br /> 2 . The Department does not recommend drilling the deep wells <br /> with a hollow stem auger as PG&E is considering. Drilling <br /> beyond the saturated zone with an auger tends to allow water <br /> to move down the auger and contaminate the lower zones. The <br /> existing plan, to use a mud rotary drill through the <br /> saturated zone, should be maintained. Any major <br /> modification of this plan would require review and approval <br /> by the Department. <br />