Davenport, Bettendorf taking steps to address sewage plant overflows

Davenport recently approved a $1.3-million engineering contract to plan sewage system improvements aimed at alleviating overcapacity at its treatment plant and the discharge of partially treated sewage into the Mississippi River.

Meanwhile, Bettendorf -- one-quarter owner of the Davenport treatment plant -- is eyeing a four-year 49 percent overall sewer rate hike to fund its share of the plant upgrade and pay for a new sewer interceptor and lift-station for future development of the I-80/Middle Road corridor.

Davenport has been facing a Dec. 31, 2015 deadline from the Iowa Department of Natural Resources (IDNR) to complete the projected $40 million sewage treatment plant improvements.

Veenstra & Kimm, Inc., of West Des Moines, was hired Wednesday (12/12) by Davenport to develop an overall plan, and the IDNR will now wait until June 2012 before trying to finalize a binding consent order on specific improvements between the city and the IDNR.

The Davenport plant, built in 1973, is designed to handle an average of 26 million gallons of sewage per day during dry weather flows, and up to 40 million gallons per day during times when rainwater infiltrates into the city's sanitary sewer lines.

When flows exceed the plant capacity –– which regularly occurs according to the IDNR –– sewage is only partially treated, blended with treated wastewater and then discharged into the Mississippi River.

During 2010, Davenport discharged 548 million gallons of partially treated wastewater into the Mississippi over 74 days, in addition to discharging untreated wastewater on three occasions.

Bettendorf experiences sewage backup in its sewer lines during high "wet weather" flows. To cope with the backup, the city operates pumps along the riverfront which, in 2010, discharged nearly 18 million gallons of untreated wastewater into the river.

In the current Bettendorf capital improvement plan under consideration by the city council, $7 million is budgeted in fiscal 2014-15 for the city's share of the sewage treatment plant equalization basin project.

To pay for the improvement -- plus a new sewer interceptor and lift-station along Spencer Creek estimated at $5.4 million -- Bettendorf is looking at an overall 49 percent increase in sewer rates over the next four years.

The new Spencer Creek sewer interceptor and lift-station would serve the I-80 and Middle Road corridor, including the Iowa Gateway Center Business Park the city has been marketing. The city purchased land north of I-80 and east of Middle Road four years ago, saying the purchase was necessary in order to better control development of the northeast corner of the I-80 interchange.

The phase-in of sewer rate increases would start in the coming fiscal year beginning June 1, boosting the current $1.68 per unit charge to $1.85 per unit. The rate would go up 15 cents, 25 cents and 25 cents, respectively, in the following three years.

By fiscal June 1, 2015, the rate would be $2.50 per unit in order to repay the sewer revenue bonds issued by the city.

The average residential customer currently pays $19.28 per month, according to city officials. At the end of the four-year phase-in, the cost would be $27.75, or about a $100 increase on an annual basis.