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The Scarlet & Black

Source of mysterious noise revealed – not the end of the world

What, you may ask, is that obnoxious sound that, over the past few weeks, has made our campus seem like it was located 50 yards from a bustling airport?

According to Jan Anderson, the Water Resources Director for the city of Grinnell, it is the sound of water surging to the surface of the well as air pressure is released.

With overwhelming pressure and a noise that can be heard over nine blocks away, municipal employee Paul Daehn controls the release of compressed air from the Jordan aquifer beneath Grinnell. This process, known as air-surging, picks up loose white silica at the bottom of the aquifer and pushes it out of the top, preventing the pumps from getting clogged with the fine white dust - Aaron Barker

“Our number 8 well started developing some problems about August,” Anderson said. “We noticed that the production or amount of water that it was pumping had been dropping.”

A contractor was called in to remove the pipe, the pump and the motor. The motor had been basically destroyed by something abrasive. A camera was sent down into the well, where, it turned out, there was a lot of sand. “It’s the first time it’s happened here in I don’t know how long, it’s been in excess of 50 years,” said Anderson.

“What they’re doing is a process called air-surging and baling,” Anderson said. Northway Well and Pump has been contracted to pump air into the 2500 ft well, compressing the water back into the Jordan Aquifer, which supplies the water to this well and all others in Grinnell. Then, a valve is released and the water surges upward, depositing the sand in a sump just below the aquifer. After a few hours, a “baler” is inserted into the pipe where it scoops up the sand deposits that have collected in the sump.

The noises are expected to stop this week, after exactly four weeks of air-surging and baling. “It’s very annoying, I know,” Anderson said. “I have a lot of residents that call and aren’t very happy with me.”

Grinnell has spent an estimated $100,000 to clean the well and replace the pump. However, the process of building a new well would have cost between 1.5 and 1.6 billion dollars. The well was built in 1973 and is one of the largest in the city.

“In the overall scope of things, it’s a relatively new well,” said Anderson.

The far older wells were built in the 1920’s and are usually only used during periods of higher than normal water use.

“We have three large producing wells. They’ll produce anywhere from 1200 to 1500 gallons per minute. The two smaller wells, the older wells, between the two of them, they’ll produce about 700 gallons per minute,” said Anderson.

While the repair of the well has been a rather boisterous affair, it is a necessary one, as the residents of Grinnell and Grinnell College use between 1.2 and 1.4 million gallons of water a day.

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    Matthew Z.Nov 12, 2010 at 1:56 pm

    A 1.6 billion dollar well? I could put a high-speed train through Wisconsin for that price!