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Mr. Val F. Siebal <br /> Page Two <br /> March 9, 1992 <br /> The results indicated concentrations of PNAs in the soil that are <br /> consistent with background concentrations. DTSC concurred with PG&E's <br /> position (based on historical documents) that the gas manufacturing <br /> operations did not involve or affect the substation. <br /> DTSC expressed concern over total PCB concentrations measured in <br /> surface soil samples which ranged from non-detectable to 2 ppm. DTSC <br /> said that arsenic, copper, and lead concentrations might also be a <br /> concern as they were detected above typical background concentrations. <br /> PG&E does not believe that these results support further investigations <br /> in the substation for the following reasons. <br /> a. The concentrations detected are low. The PCB concentrations <br /> are well below the action levels/cleanup levels required by EPA in its <br /> comprehensive regulations and policies for PCB cleanups in restricted <br /> and unrestricted substations. Also, the concentrations are well below <br /> the action/cleanup levels generally provided in regulations adopted <br /> pursuant to the Federal Toxic Substances Control Act (TSCA) and for PCB <br /> hazardous waste sites. Both sources report 25 ppm as a threshold level <br /> as indicated in the attached excerpts. Also, California hazardous waste <br /> regulations (Title 22 of the California Code of Regulations, Section <br /> 66261 .24) defines waste soils containing PCBs to be hazardous waste if <br /> the total PCB concentration exceeds the Total Threshold Limit <br /> Concentration (TTLC) of 50 ppm. Likewise, the metal concentrations are <br /> well below TTLCs, except lead in only one sample out of the seven <br /> analyzed. Moreover, PG&E has an ongoing program for the maintenance and <br /> cleanup of substations. Our substations are within the jurisdiction of <br /> and are subject to numerous inspections by EPA TSCA field inspectors and <br /> contractors. These inspections are extremely rigid and the penalties <br /> for unmitigated PCB releases are quite severe. <br /> b. The potential for human exposure to soil is low. The area is <br /> within a working substation, which is fenced and locked and is <br /> accessible only to PG&E workers. The substation is not permanently <br /> manned, electrical workers do not report there on a daily basis. <br /> Excavations are prohibited in the substation, except under very limited <br /> circumstances. Furthermore, the soil is covered by a gravel blanket, <br /> which prevents direct contact with the soil . It is extremely unlikely <br /> that this land use will change in the foreseeable future. When PG&E de- <br /> energizes and closes a substation, before the surplus property is <br /> conveyed, it is tested and, if required, it is cleaned up, and a deed <br /> restriction is imposed, if warranted. <br /> c. The use of equipment to conduct subsurface investigation in <br /> the energized portion of a substation could be very dangerous and is <br /> quite disruptive. Incoming power on high-voltage overhead lines and <br /> overhead equipment present electrocution hazards. The shallow <br /> subsurface is criss-crossed by thousands of electrical lines. The <br /> ground grid is a buried mesh of copper cable which connects every piece <br /> of equipment in the substation to each other and to a ground in the <br />