06/22/2021 (3) - Laserfiche WebLink

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K mley>>)Horn MEMORANDUM Himanshu Mehta, PE To: IRC SWDD From: Jill Grimaldi, BCES Kimley-Horn and Associates, Inc. Date: June 11. 2021 Subject: Centrate Tank Refurbishing by Crom As the Solid Waste Disposal District evaluates options for the treatment and disposal of the leachate generated by the County's landfill, the existing centrate tank associated with the biosolids dewatering facility is in the process of being repurposed for leachate storage. To be able to properly store the leachate, the existing centrate tank requires an interior coating that is designed and rated to withstand the corrosive environment created by the leachate. The existing interior coating does not meet those requirements. Kimley-Horn has engaged the original tank manufacturer, Crom Corporation, to determine what process is required to recoat the tank walls and bottom, while preserving the tank's integrity and any remaining warranty items per Crom's specifications. In addition, the tank will require the addition of a mixing mechanism to keep the leachate mixed during storage. The potential mixing options currently under evaluation include jet pump mixers that require cores to be drilled in the walls of the tank. It is imperative that this work be performed by the tank manufacturer to reduce the risk of damaging the prestressing rings that span the circumference of the tank. Crom routinely performs such core drillings on their pre -stressed tanks for various applications and it would not be advisable to allow a separate contractor to complete such work. It is for that reason that we recommend that SWDD proceed with a sole -source contract to Crom for the recoating and installation of the mixer (to De direct purchased by the County upon completion of the mixing evaluation). Attached is Crom Corporation's propcsal for the cleaning of the tank, removal of the existing coating, visual inspection of the tank interior and exterior for cracks and overall condition and application of the specified coating for leachate storage. Options were included within this proposal for the coating of the underside of the dome (if warranted by the selected mixer design), coating of the interior piping to provide additional corrosion protection, an-- for up to four (4) wall penetrations to accommodate the mixer and fill line modifications. If the mixer ti -at is ultimately selected does not require the dome coating or wall penetrations, a deductive change order could be issued to recoup that budget from Crom.