CORRESPONDENCE_2007 (7/07 - 12/07)

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San Joaquin County =nvironmental Health Department 600 East Main Street Stockton, California 95202-3029 Website: www.sjgov.org/ehd Phone: (209) 468-3420 Fax: (209) 464-0138 August 27, 2007 Mr. Desi Reno, Integrated Solid Waste Manager San Joaquin County Department of Public Works Solid Waste Division P.O. Box 1810 Stockton, CA 95201 Subject: Corral Hollow Landfill (39 -AA -0005) Closure Cap Investigation Project Dear Mr. Reno: DIRECTOR Donna Heran, REHS ASSISTANT DIRECTOR Laurie Cotulla, REHS PROGRAM COORDINATORS Carl Borgman, REHS Mike Huggins, REHS, RDI Margaret Lagorio, REHS Robert McClellon, REHS Jeff Carruesco, REHS, RDI Kasey Foley, REHS An initial investigation conducted at Corral Hollow Landfill in 2005, determined that solid waste materials extended beyond the prescriptive closure cap. Because the investigation did not identify how far the waste extended beyond the cap, an additional investigation was conducted in June 2007, to determine the horizontal extent of the waste. This investigation revealed that waste extended at least to the eastern property line. In an attempt to fully delineate the extent of the waste, the Department of Public Works, Solid Waste Division (DPW-SWD), conducted an investigation on the property belonging to the California Department of Transportation (Caltrans) on August 16, 2007. Through a request from Caltrans, the DPW-SWD was allowed to conduct a subsurface investigation east of the landfill property line. The investigation conclusively showed that waste extended onto the Caltrans property; however; the vertical and horizontal extent of the waste was not determined. Waste was first encountered at 8 feet, but it extended beyond the reach of the backhoe (13.5 feet in depth). The waste discovered in the excavation did not appear to have been burned, and there was a certain amount of paper and plastic present. Due to safety issues, the Caltrans representative on site did not want the excavations to encroach too closely to the Highway 580 on-ramp area. Although this investigation did provide additional information about actual site conditions, the full extent (vertical and horizontal) of the waste on the Caltrans property was not determined. Accordingly, an additional investigation will be necessary. Once the full extent of the waste onto Caltrans property is determined, waste found outside of the closure cap will require mitigation. Options for mitigation include clean closure of the area or closure as described in Title 27 of the California Code of Regulations (T27CCR). Clean closure would require the complete removal of the waste not covered by the prescriptive cap in accordance with an approved plan. Closure as described in T27CCR, by extending the closure cap, would require a cap design that meets T27CCR requirements and is approved by the Regional Water Quality Control Board (RWQCB), California Integrated Waste Management Board (CIWMB) and the Environmental Health Department (EHD). Amendments to the Closure/Post Closure Maintenance Plan (CPCMP) and the Closure Cost Estimate for the facility would be needed and should include the newly capped area and the associated cost.