Coralville working toward Wastewater Treatment Plant upgrades

CORALVILLE — Coralville's population nearly doubled in the decade from 1990 to 2010, from about 10,000 residents to more than 19,000. Since 1994, the community's Wastewater Treatment Plant has managed to keep up.

But after more than 20 years of service, the majority of the plant's operations — an intricate pattern of buildings, pipes, blowers and pumps — are reaching the end of their life span, and city officials are planning close to $27.1 million in updates to the plant.

City Engineer Dan Holderness said the plant, at 750 Camp Cardinal Rd., has served the community well and could continue to do so for several more years. But with the city's population projected to continue to grow, major updates to the plant are necessary.

'Typically you design a treatment plant for a 20-year design life. Our plant has done what we've needed it to do — it's just nearing the end of it's design life.' he said.

On Tuesday, the Coralville City Council approved setting a public hearing for Feb. 24 to discuss applying for a state loan to fund updates to the city's roughly 21-year-old plant.

Funding

If approved by the council at the public hearing, and the Iowa Department of Natural Resources grants the city the $27.1 million, 20-year Clean Water State Revolving Fund loan, work on the project could begin September 2016 and be finished November 2018, Holderness said.

The project cost will be covered through net revenues of the city's Sewer Enterprise Fund, meaning Coralville residents likely will see a few more years of increasing sewer rates.

To begin the funding process, Coralville rates increased last fiscal year from $12.54 per month for a user of 400 cubic feet of water to $13.34 per month.

[naviga:h3 style="width: 100%;"]Monthly bill for using 400 cubic feet From July 1 for each year. Proposed rate for July 1, 2015 is $14.69

This fiscal year's budget proposes another $1.35 per month increase — to $14.69 a month — for a user of 400 cubic feet each month. Coralville's rates were unchanged from 2007 through 2011.

Coralville Director of Finance Tony Roetlin said the proposed increase for fiscal year 2016, which needs to be approved in the budget by March, is the second of a five-year planned increase in rates to fund the plant updates.

'That's a multiyear stair-stepping approach that we're in the second year of with the current budget proposal,' he said. 'It's to put the city in a position where it can fund the upgrades that we're planning for and service the needs of the community for the next 20 years.'

An aging plant

Coralville's first wastewater treatment facility was built in 1969, with sewage pumped through lift stations to Iowa City's plant before that.

Over the years the plant has seen several upgrades due to increasing flows and changing regulation requirements by the Iowa Department of Natural Resources.

Walking through the many buildings of the plant this past Tuesday, Superintendent Chris Gilstrap pointed out the systems of pumps, aerators, blowers and roughly 400 ultraviolent disinfecting bulbs.

'These units in here were installed in 1993, so they have 22 years worth of hours on them,' Gilstrap said.

The proposed upgrades would convert the current sequencing batch reactor plant into a continuous flow activated sludge plant.

In simpler terms, Holderness said the updated plant would offer more capacity for a growing community, provide easier operation for the plant's five staff members and allow for more flexibility to meet any changes to water-quality requirements.

'This is obviously a very significant upgrade to the plant,' Holderness said. 'It's kind of a change in the process in its entirety.'

Gilstrap said the upgrades also would greatly increase efficiency at the plant.

The next 20 years

When the current plant was built, city officials made an estimate on what the community's population would be when the plant reached its 20-year design life.

Coralville grew faster than expected and the estimate ultimately fell about 3,000 people short of the 19,000 people recorded in the 2010 census.

Holderness said another estimate puts Coralville's population at about 30,000 people at about 2035, when the plant's updates will be reaching the end of their 20-year design life.

Holderness said the proposed updates aim to keep up with Coralville's growing population and ensure the community has the utilities needed to handle that growth for the next two decades.

'Our council always wants to be ahead of the curve, we want to make sure we have adequate public utilities so they don't hinder potential growth,' he said.

'It's kind of like a car, we're getting to the end of the use of life of the plant and are looking forward to the future to design a new facility to take us to the next 20 years.'