NORTH LIBERTY– Some North Liberty residents may soon notice a tangible shroud of mystery hanging over one northeast part of the city.
The city’s water tower on 240th Street is scheduled to be repainted this year, and the process requires a large curtain to be draped over the entire structure in order to contain any debris it might create.
The North Liberty City Council approved funding for the project in June, at that time estimated to cost around $300,000 to $400,000. However, North Liberty Water Superintendent Greg Metternich said bids were opened last week, and some have come in lower than anticipated.
It’s still a pricey paintjob. But Metternich said it’s necessary to maintain the integrity of the structure. Over time, the steel tanks of water towers begin to rust and show signs of damage and age, both inside and out.
“We have to protect the tank to keep it from rusting and to maintain the quality of the water stored inside,” said Metternich. The protective paint coatings on water towers generally last 20 to 30 years, depending on the environment. “We get extremely cold and extremely hot temperatures here, and the fluctuations are hard on those coatings.”
The tower on 240th Street was erected in 1995. Its capacity is 400,000 gallons of water, and one of its major functions is to maintain pressure in the city’s water system, as well as store enough water to provide backup capacity in case of an emergency; for example, if one of the city’s major well pumps malfunctions.
“With the ASR (Aquifer Storage Recovery) well, you rely on several outside factors; electricity, and a mechanical device that is 630 feet in the ground,” said Metternich. If the system’s pump and motor ever fails, the well could be down for several months for repairs. “While the ASR well is a great technology and does what it is supposed to do, there are a lot of factors that go into it, plus the electricity to operate it costs a lot.”
In contrast, above ground storage tanks rely on hydrostatic pressure– produced by the combination of elevation and gravity– to push water into the city’s treatment and distribution plant. That’s why having a water tower is also very important to the city’s water system.
“We had no backup power in the plant until 2007. If the plant went down, (at current demand) we would probably get a day and a half of use before having issues,” Metternich said. The DNR (Department of Natural Resources) also requires cities to have mechanisms in place, including enough stored water, to handle emergencies.
Metternich has been with the city for 18 years, and he said the city’s towers have been inspected routinely every two years. This tower, now nearly 20 years old, has been spot treated several times, but it has aged to the point where spot treating– necessary in perhaps as many as 400 small places where the tank is rusting or has weld marks– is no longer an efficient use of resources.
“The last time this tank was inspected, it was recommended we sandblast and paint the entire structure. But it’s such a huge investment, we had to put things in order to make sure we could afford it. We decided at that time to address the most immediate problem, which was the wet part of the tank,” said Metternich.
So two years ago, the tank was drained and its interior sandblasted and painted to protect the water source. Knowing the outside would need to be done soon, the company went ahead and welded steel plates around the outside of the tank that will hold the giant drape around the tower during its upcoming exterior makeover.
The curtain, which Metternich expects to be some sort of heavy canvas, will simply protect the businesses and vehicles in the areas near the foot of the tower from any debris sandblasting might create, and contain any wayward paint drips.
“It’s very messy, and when you roll paint, a drip can carry a long way in a light wind,” he said.
Weather will dictate the progress of the repainting project, as the paint can only be applied within a certain temperature range. The tower will again be drained, even though the painting is only to the outside, because stored water creates condensation on the outside of the tank that would make it impossible to coat properly. Metternich said he expects the repainting project to be completed by October.
Meanwhile, city’s wells and the second water tower located on Kansas Avenue– which has a million gallon capacity– will work in tandem to ensure that North Liberty residents continue to have water when they want it.
“People shouldn’t notice any difference,” Metternich said.
Except, perhaps, for a very large drapery suspended about 150 feet above 240th Street; it might get a little attention.