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Response 2: CC&V made enhancements to the primary containment of the leach <br /> tanks by installing 30" downcomer pipes. This change increased the effective free <br /> board because lower differential pressure is required to flow from tank to tank with <br /> the new downcomer pipes. Improvements made to the process flow between tanks is <br /> outlined in Response#3. <br /> Comment 3: During the April 28, 2016 inspection, the Division observed evidence that <br /> Vat Leach Tank#1 had overtopped and splattered on the adjacent building. Please <br /> specify hoiv TR-81 addresses enhancements to the tank battery to minimize spills from the <br /> tanks, specifically spills related to the splatter on the adjacent building. The Division <br /> believes the installation of guards around the crest of the tank could direct wind--blown <br /> froth doivn the sides of the vat leach tanks and prevent splattering outside of the <br /> secondary containment. <br /> Response 3: Upon further investigation CC&Vconcluded the cause of the spill <br /> relating to splatter on the adjacent building was the restriction of material flow <br /> through the leach tank circuit and overtopping of the conditioning tank. <br /> Accordingly, this has been addressed by replacing upcomer 8" pipe with <br /> downcomer 30" pipe to improve flow from tank to tank in the leach circuit (Figures <br /> 1 and 2). <br /> This improvement has eliminated the chance of future upset conditions and the <br /> chance for splatter as the new downcomers allow unrestricted flow between tanks so <br /> solution does not back up above the normal exit paths thus maintaining tank <br /> freeboard that is acting exactly as guarding. The freeboard increases down the train <br /> with each progressive leach tank in the tank circuit. <br /> As a result of the changes outlined above, CC&V has evaluated the placement of <br /> guarding would not afford any additional protection, considering the likely failure <br /> mechanism which caused the original event. <br />