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Ms.Anne Olson,RWQCB� • December 28,2010 Work Plan for Diamond Pet Foods Impoundment Closure Page 2 of 4 PROPOSED CLOSURE METHOD AND ALTERNATIVES Two closure alternatives were evaluated—clean closure and capping the sludge in place with a vegetative cap. The capping-in-place option was chosen as the most cost effective. Clean Closure The closest facility that could accept the sludge is the Forward Landfill in Manteca, California, approximately 14 miles from the Diamond site. We used the following assumptions for the analysis of clean closure: • The waste would be trucked to Forward Landfill in one-hour round trips at $95 per hour. • Truck capacity would be 21 tons. • The material has a density of 67 pounds per cubic foot. Using these assumptions, the cost for trucking alone would be over$160,000. Additionally there would be cost for an excavator, operator, finish grading, erosion control, and tipping fees at the landfill. Capping in Place The second closure option evaluated was capping in place with a native-soil vegetated cover. In this option, the impoundment itself is eliminated by removing the one of the berms. This provides soil for the cover and potentially reduces percolation through the material that might occur if water collected in the impoundment. The existing material (both sludge and soil cover) will be consolidated, graded to drain, and capped with a one-foot thick vegetative layer. Use of soil from the east berm of the impoundment eliminates the need to import soil. Plan Sheet C3.0 shows the proposed closure contours. Plan Sheet C4.0 shows details through the proposed closure cap. Drainage off the cap will sheet flow towards the West Percolation Field. Monitoring well OB-9 must be decommissioned before construction, as it is located on the berm that is to be removed. It is not proposed to replace this well, as it is located close to, and between, two other wells (013-12 and 013-18) that have similar water quality and show similar trends as 013-9. Additionally, all of three of these wells show decreasing trends in water quality(improving water quality). Final construction specifications would be submitted to RWQCB for approval before beginning construction. During construction, Lawrence&Associates will provide periodic construction quality assurance (CQA) inspection. After the construction is complete, an as-built report will be submitted, including CQA results. 010107.00 Lawrence&Associates W.•ICLIENTYDiamond Pet FoodsW10107.00-Ripon ROWDIDiamondPet_Ripon_Impoundment_Closure.docx