SITE INFORMATION AND CORRESPONDENCE 1995-2004

Home Browse Search

IPJames L. Tjosvold, P. October 5, 1999 Page 2 federal RCRA regulations. These regulatory changes eliminated certain exemptions from RCRA regulation for manufactured gas plant-derived wastes which contain constituents above RCRA threshold criteria, and required that such wastes be subject to management as a RCRA waste as of August 24, 1998 (Land Ban Phase IV Final Rule, May 26, 1998, 63 Fed. Reg. 28555). These changes, considered together with analytical results from further sampling of the site source areas, essentially eliminated the possibility of using an onsite asphalt batch reuse process for the management of site wastes. Accordingly, the September 21 request contained the following description of soil management measures to be employed: • Soil that is below certain specified threshold concentrations of polynuclear aromatic hydrocarbons ("PNAs")would be reused onsite as backfill; • Soil containing PNAs in concentrations above the threshold limits, but which is not a hazardous waste according to California or RCRA regulations, would be transported offsite for disposal at a Class II landfill; and, • Soil containing constituents in concentrations greater than RCRA hazardous waste thresholds would be transported offsite to a RCRA Subtitle C licensed facility. By letter dated November 5, 1998, DTSC acknowledged the required soil management measures and accepted PG&E's proposal of September 21, noting that"...the selected cleanup alternative already includes excavation and offsite disposal of material"and that "...this modification essentially adds additional volume of material for offsite disposal in place of treatment and reuse." The DTSC letter went on to conclude that"...these changes are not considered major modifications and therefore will not require formal procedures to incorporate them into the RAP." On October 30, 1998,PG&E submitted a draft Remedial Design and Implementation Plan ("RDIP") to DTSC which incorporated the revised soil management measures; DTSC approved the RDIP by letter dated December 17, 1998, contingent on various comments being addressed in the final version of the document; the final RDIP incorporating those revisions was submitted by PG&E on April 30, 1999. Description of the Proposed Change At the time the RDIP was prepared, PG&E estimated that the quantity of soil requiring otr-site management as a RCRA hazardous waste would be approximately 111 cubic yards,originating primarily in Source Area 3. However, significant quantities of materials excavated principally from the bottom of Source Area 2, and in the vicinity of the forma lampblack separators, have shown soluble concentrations of benzene above the RCRA hazardous waste threshold concentration of 0.5 mg/L. This material, which constitutes approximately 1000 cubic yards, is currently stockpiled onsite, covered with plastic shazting. An additional 600-700 cubic yards of soil which potentially contains