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MEMO <br /> <br />To: Distribution <br />From: Dawn Homer <br /> Elk River Digester - Cover <br />Subject: Problems <br />Date: July 13, 2004 <br /> <br /> Howard R, Green Company <br /> <br />PURPOSE <br />This memo summarizes the cover problems with the primary digester. The digester was <br />scheduled to be taken offline in early September for rehabilitation and new cover installation. <br />The digester was scheduled to be placed on line within eight weeks. Due to problems with the <br />existing cover, which are described below, it is recommended that the primary digester be taken <br />offline approximately four weeks earlier than originally scheduled. <br /> <br />COVER PROBLEMS <br />In June, the primary digester cover began to shift <br />and eventually caused bolts to come out of the <br />concrete and cause structural damage around <br />the wall of the digester. The pictures show the <br />bolts and structural damage to the concrete. The <br />tank is also venting gas directly to the <br />atmosphere. In order to make the plant a safer <br />environment and to avoid further structural <br />damage, which could be very costly, HRG <br />recommends taking the digester out of service as <br />soon as the temporary piping to heat the <br />secondary digester is available and <br />arrangements are made to remove the liquid <br />sludge. <br /> <br />The Contractor is set to begin temporary piping <br />July 19th to provide heat to the secondary <br />digester. This will provide some treatment of the <br />sludge prior to routing to the storage tanks. This <br />was a very important part of the design when the <br />digester was scheduled to be down for 8-weeks <br />and will be even more important if this time is <br />extended. <br /> <br />The existing sludge storage tanks can hold <br />700,000 gallons. The operators assume the <br />tanks are currently at 520,000 gallons. This <br />sludge would need to be removed in order to ~ <br />empty the contents of the primary digester. The digester volume is approximately 394,000 <br />gallons. The sludge taken from the digester would need to be tested prior to land application <br />and meet vector attraction and pathogen reduction regulations. <br /> <br />C:\Documents and Settings\jmiller. ELKRIVERPD\Local Settings\Temporary Intemet Files\OLK20\mem-071304- <br />coverproblems 11 .doc <br /> <br /> <br />