Latest sewage bypass lasted four days and totaled 18.4 million gallons pumped into Mississippi River

Bettendorf pumped 18.4 million gallons of untreated sewage mixed with storm water into the Mississippi River over a four-day period earlier this month after heavy rain and high water clogged the main interceptor along the riverfront and flows overwhelmed the treatment capacity of the Davenport/Bettendorf sewage treatment plant.

Pumps along the riverfront operated from June 14 through June 18, transferring back-up in the sewer lines into storm water pipes that empty into the river.

The "bypassing" has become a regular occurrence each spring when heavy rain and high river levels infiltrate the large interceptor line carrying sewage from Riverdale, Bettendorf and Davenport to the jointly owned sewage treatment plant along Concord Street in Davenport.

Davenport, Bettendorf and Riverdale signed a consent order with the Iowa Department of Natural Resources in 2012 pledging to fix infiltration problems in the sewer lines and expand the treatment capacity of the sewage plant.

The engineering consultant for the three cities submitted plans for expanding the treatment capacity of the plant January 1 of this year, in accordance with the consent order.

The goal of the plant optimization project is to increase the capacity of "secondary capacity" treatment from 45 million gallons per day to approximately 52 million gallons per day. The optimization project is to be complete by July 1, 2017, under the consent order.

Overall, the sewage treatment system owners are to spend an estimated $160-million over 20 years to upgrade the sewer system.

Meanwhile, each spring sets of pumps are put in place near the Interstate 74 bridge to "bypass" sewage into storm water lines.

And, to handle the peak flows during such times, sewage at the treatment plant receives only primary treatment before being dumped into the river.

The sewage treatment plant makes its report on secondary treatment "bypasses" monthly, so the amount of sewage discharged to the river with only partial treatment won't be known until next month.

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