5.3. SR 07-19-2004 - Laserfiche WebLink

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The City cannot land apply sludge between April and October due to regulations for highly permeable soils. The sludge can be land applied if crops are to be planted within 14 days of application, which typically does not occur in the fall. Therefore, other options were analyzed to determine how the sludge could be removed if the digester was taken off line. Plant staff and HRG have contacted Jorja DuFresne of the MPCA. The City basically has three options as listed below. Each option has advantages and disadvantages. · Maintain operating conditions and hope that the cover is safe and that further structural damage does not occur. · Hire a contractor to set up at the plant site to remove the sludge from the storage tank and run it through a belt press. The City would then haul the dried sludge to a landfill. · Hire a contractor to haul the sludge to one of the Met Council treatment plants. MAINTAIN OPERATING CONDITIONS HRG recommends that the tank be taken out of service to provide operator safety and avoid further structural damage. The cover seems to be stable at this point, but if pressure builds up within the tank and causes the cover to move a substantial amount, further structural damage is definite and would be extremely costly. The Contractor predicts a worse case scenario of replacing the entire above grade portion of the concrete tank that is 12-inches thick. The below grade portion of the tank is 18-inch thick and should not suffer as much damage. It is recommended that the City review the two options below and take the primary digester out of service as soon as possible. LANDFILL The City has contacted a contractor that can provide equipment on-site that would remove the sludge from the storage tanks, run it through a belt filter press to dry the sludge, and the City would haul the dried sludge to a landfill. The local landfill has been contacted to determine if they would take the sludge. The contractor stated that the sludge could be removed, dried, and hauled to the landfill at a cost of $0.045/gallon. The contractor previously provided this service to the City of Owatonna, MN. There would also be an additional chemical cost of $2,500 to assist in drying the sludge. To remove the entire storage tank volume estimated at 520,000 gallons, the cost is estimated at $23,500 + $2,500 = $26,000 or $0.05/gallon. Landfill fees were based on two options. If the landfill can consider the dried sludge a cover, the cost would be $12 per ton of solids. If the sludge is considered disposal, the cost would be $36 per 18 cubic yards. The landfill decided that the sludge would be considered a cover material. Sludge quantities were estimated assuming 520,000 gallons of wet sludge at 4.9% total solids. It was assumed the sludge could be dried to 18% with the belt filter press and have a specific gravity of 1.06. Based on approximately 620 tons of 18% solid sludge at $12 per ton, the cost would be $7,500 or $0.015/gallon for a total of $0.065/gallon or $35,000. The City has trucks available to haul dried sludge to the landfill. These costs are not included. METROPOLITAN COUNCIL The City has another option to haul liquid sludge from the storage tank to one of the Met Council treatment facilities. HRG spoke with Leo Hermes the manager of the Industrial Waste C:\Documents and Settings\jmiller. ELKRIVERPD\Local Settings\Temporary Internet Files\OLK20\mem-071304- 2 coverproblems 11 .doc