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5.3. SR 07-19-2004MEMORANDUI ! Item ~ 5.3. TO: Mayor and City Council FROM: Pat Klaers, City Administrator DATE: July 19, 2004 SUBJECT: ~f~VTP Digester Cover Project Attached for your information is a memo from Dawn Homer from Howard R. Green Company who is wot -king with the city on the digester cover project. As you can tell by the memo, this project certainly could not have waited another year and, in fact, maybe should have been done last year. Nonetheless, based on the cover shifting that has recently taken place, it is very timely that the City Council has moved this project forward in 2004. The digester cover shifting at this time moves the removal of the cover up approximately one month. The city is moving forward with the landfill recommendation to address the sludge disposal situation. There are sufficient funds in the WWTP reserve for this addition to the project. While the cost per gallon for disposal at the Met Council Treatment Facility is slightly below the total cost for the landfill option, the Met Council option does not include the trucking expenses which are guesstimated to be substantial. S: \Council\ Pat \ 2004\xvxvtpdigestercover.doc MEMO To: Distribution From: Dawn Homer Elk River Digester - Cover Subject: Problems Date: July 13, 2004 Howard R, Green Company PURPOSE This memo summarizes the cover problems with the primary digester. The digester was scheduled to be taken offline in early September for rehabilitation and new cover installation. The digester was scheduled to be placed on line within eight weeks. Due to problems with the existing cover, which are described below, it is recommended that the primary digester be taken offline approximately four weeks earlier than originally scheduled. COVER PROBLEMS In June, the primary digester cover began to shift and eventually caused bolts to come out of the concrete and cause structural damage around the wall of the digester. The pictures show the bolts and structural damage to the concrete. The tank is also venting gas directly to the atmosphere. In order to make the plant a safer environment and to avoid further structural damage, which could be very costly, HRG recommends taking the digester out of service as soon as the temporary piping to heat the secondary digester is available and arrangements are made to remove the liquid sludge. The Contractor is set to begin temporary piping July 19th to provide heat to the secondary digester. This will provide some treatment of the sludge prior to routing to the storage tanks. This was a very important part of the design when the digester was scheduled to be down for 8-weeks and will be even more important if this time is extended. The existing sludge storage tanks can hold 700,000 gallons. The operators assume the tanks are currently at 520,000 gallons. This sludge would need to be removed in order to ~ empty the contents of the primary digester. The digester volume is approximately 394,000 gallons. The sludge taken from the digester would need to be tested prior to land application and meet vector attraction and pathogen reduction regulations. C:\Documents and Settings\jmiller. ELKRIVERPD\Local Settings\Temporary Intemet Files\OLK20\mem-071304- coverproblems 11 .doc 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 department for Met Council (651-602-4701). Met Council would classify this as a shod-term discharge (lasting 2 to 3 weeks) from an out of area location. Several fees would be involved and were roughly calculated for the City of Elk River. Actual liquid sludge strengths were not available so they were assumed to be typical levels for preliminary estimates. · Permit application with $300 fee · Strength charge: Based on 25,000 mg/I of TSS (total suspended solids) and 20,000 mg/I of COD (carbonaceous oxygen demand), the cost for communities within the metro service area would be $36.00/1000 gallons. This charge would be approximately doubled since Elk River is outside of the Metro Area, which would make it $72.0011000 gallons. · The industrial load charge includes the strength charge plus a volume charge of $1.34/1000 gallons. · Out of Service Area charge of $50 per load. Loads are typically 5000 gallons. This equates to a cost of $1011000 gallons. This totals approximately $84/1000 gallons, $0.084 per gallon or $45,000 based on the estimated amount of sludge. This does not include trucking costs. The City does not have equipment available to haul liquid waste. Met Council would need the completed permit application and $300 fee submitted. The sludge strength and heavy metal concentration would need to be submitted with the permit. A letter describing the reason for discharging to Met Council would also be required. Once submitted, they would determine which plant location would be available to accept the liquid sludge. They would then write an approval form that would need to be authorized. They said the process can take up to two weeks, and that accepting sludge within two or three weeks would be possible. RECOMMENDATION It is recommended that the City select the landfill option. The estimated cost of $35,000 is very rough since several assumption were involved beginning with the amount of sludge that needs to be removed from the storage tank. The digester project contractor has been contacted and can begin temporary piping to the secondary digester July 19th. Plant staff is conducting the necessary tests required by the landfill to allow disposal and should be approved by next week. Once the sludge is approved by the landfill, the contractor that will remove the sludge and dry will mobilize equipment to the plant site. The sludge drying rate was estimated at 3000 gallons per hour. Based on an 8-hour day, this would take approximately 22 days. The City should begin emptying the tank with the least amount of sludge. That tank could then be used to hold the primary digester sludge while it is taken offline and the other tank can continue to be emptied. City staff plans to have the primary digester offiine by early August. Once the tank is empty, the digester project contractor will began removal of the existing cover. The structural damage will be assessed at this time and a change order is possible. Distribution: Gary Leirmoe, City of Elk River WWTP Lori Johnson, City of Elk River Finance Director Terry Maurer, HRG C:\Documents and Settings\jmiller. ELKRIVERPD\Local Settings\Temporary lnternet Files\OLK20\mem-071304- 3 coverproblemsl 1 .doc