Moline's water pollution control department is recommending a $37.6 million upgrade and expansion at the North Slope treatment plant, needed in part to comply with Illinois EPA guidelines.

"This is critical infrastructure to our community and has serviced us well, but the time has come for us to reinvest so we can keep providing a high level of service to our community," said Greg Swanson, Moline's utilities general manager.

The city has two wastewater treatment plants. North Slope, which is north of River Drive and just east of the Rock Island border, serves all Moline properties north of Avenue of the Cities.

South Slope is at 2800 48th Ave., across from SouthPark Mall, and serves the rest of Moline.

In July of 2009 the Illinois EPA told the city it needed to address sanitary sewer overflows on River Drive.

Mr. Swanson said River Drive manholes overflow during big rainfalls because the North Slope plant doesn't have enough capacity to handle the influx of water. Water then backs up in the sanitary sewer interceptor that runs under River Drive.

The city hired Simbiont to find a solution to the overflow problem, and the company recommended building a 2-million-gallon water tank at 18th Street and River Drive and one at 34th Street and River Drive, and a 5-million-gallon tank at 39th Street and River Drive.

The tanks would collect water only during significant rains, and the rest of the time would serve no real useful purpose, Mr. Swanson said, adding that the number of "significant" rain events a year can range from none to 10.

The cost for three tanks is about $37 million.

He said he told the city council the cost was high and asked to study the entire WPC system to see if system improvements would reduce the overflow problem and update the aged plant.

North Slope was built in 1965. An addition was built in 1975, and only minor improvements have been made to the plant in the past 37 years.

A study by Strand Associatesfound North Slope improvements would allow Moline to meet EPA requirements, improve efficiency by replacing outdated treatment processes and equipment, and maintain room for future plant upgrades, Mr. Swanson said.

He andTroy Stinson, project manager for Strand Associates, proposed a plan to the Moline Committee of the Whole Tuesday to increase capacity at the plant and at the 39th Street pumping station and, if needed, build a 5.2 million gallon water storage tank on 34th Street.

Improvements would include a new pumping station and two new clarifiers behind the North Slope sewer maintenance building, and numerous updates to existing equipment.

Mr. Swanson said an upgrade to the disinfection system also would improve efficiency and safety for workers and the public.Plant updates also would increase its reliability, flexibility anddecrease energy consumption, he said.

Mr. Stinson said improvements could be funded with a $35.6 million Illinois EPA low-interest loan and $2 million in WPC capital reserves.The estimated annual loan and interest payment, due beginning in 2016, would be $2.16 million, he said.

WPC is an enterprise fund, which means it operates only on the revenue it generates through billing for wastewater service. It is not supported with property tax money.

Mr. Swanson said the loan payment could increase the revenue needs of the department by 27 percent, possibly increasing the monthly bill of the average customer by $7 a month. However, he and Mr. Stinson strongly suggested a rate study be done to formally quantify the impact.

Mr. Swanson asked aldermen for approval to spend up to $1.9 million in WPC capital reserves on a professional services contract with Strand Associates so design and engineering could begin. Public meetings would be scheduled before plans would be submitted to the Illinois EPA, he said.

However, aldermen requested additional information which is expected to be discussed next week during committee of the whole.

Mr. Swanson said the project could be put out for bid in 2014 and construction would take about a year and half.