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INFORMATION SHEET PACIFIC GAS AND ELECTRIC COMPANY CLASS II SURFACE IMPOUNDMENTS McDONALD TRACT SAN JOAQUIN COUNTY The site is about 10 miles west of Stockton in the Sacramento-San Joaquin Delta, in Section 25, T2N, R4E, MDB&M. The site consisted of three Class II surface impoundments having an area of 8.7 acres and volumes of about 10, 12, and 9 million gallons. The ponds are located adjacent to Whiskey Slough and were originally constructed as agricultural silage pits. Only Pond 3 has been actively used for waste disposal operations for the discharge of'designated' and 'inert' wastes and was closed under Chapter 15 requirements. This pond contained about 31,000 cubic yards of spent drilling fluids and produced formation water and well completion fluids discharged between 1974 and 1986. Because of design deficiencies, the Discharger was ordered in 1986 to stop discharging materials to the ponds. Since August 1986, all production fluids and spent drilling mud from the McDonald Island facility have been disposed of offsite and Discharger has proceeded with closure of the ponds. A Solid Waste Assessment Test (SWAT) was submitted by the Discharger on 29 June 1990 which determined that hazardous waste was not leaking from the site, therefore closure was based on Title 23, Division 3, Chapter 15 (no Title 22 requirements). A Closure Plan was submitted by Discharger on 30 April 1991 and conditionally approved by the Board on 9 April 1992. The Discharger also submitted a Preliminary Hydrogeological Assessment Report (PHAR)evaluating surface and ground water in the vicinity of the ponds which indicated that chlorides and barium in the waste material had leached into the shallow ground water and migrated southwest, to the adjacent surface water body (Whiskey Slough). Results of soil and waste sampling indicated that only Pond 3 contained a significant quantity of waste and needed to be closed under Chapter 15 requirements. Ponds 1 and 2 did not contain any appreciable waste and was not closed under Chapter 15 requirements. Revised cleanup levels were approved by the Board on 12 October 1994 for 200 mg/l chloride, 5 mg/l barium, and 250 mg/1 sulfate. The limit of 1500 µmhos/cm for EC would be used as an indicator parameter rather than absolute criteria during cleanup. The closure construction of the disposal ponds was conducted August through November 1994. Pond closure activities included removing and properly disposing all drilling mud materials and six inches of underlying native soil from Pond 3. About 20,000 cubic yards (30,000 tons) of non-hazardous drilling mud and native soil were removed from the site. The native soil layer beneath the drilling mud was visually examined and found to be clean and not discolored. Analysis of confirmation soil sampling indicated that all of the chemical constituents of concern - barium, chloride, sulfate and EC were at levels below the approved site cleanup levels. Ponds 1 and 2, which were not used for drilling mud disposal, were backfilled. Regrading of Pond 3 began immediately after soil cleanup was confirmed as complete. Ponds 1, 2 and 3 were regraded according to the Final Grading Plan. After regrading, revegetation of the pond site with native plants was completed. KAS:rev: 15 April 1996