What to Do with the Sperry Water Tower?

The 146-foot-tall water tower in Eagan is a money-maker for the city, but the aging building needs at least $510,000 in maintenance.

Demolish the Sperry Water Tower? Convert it into a giant hydro-battery? Make it a public art installation? Allow someone to take up private residence in it?

The ideas ranged far and wide at an Eagan City Council meeting on Tuesday night, as the council considered the fate of the 146-foot structure just north of Central Park in Eagan.

Built in 1967, the 500,000-gallon reservoir was the city's first water tower, and for decades it served as an integral part of the city's water system. But in recent years, the Sperry tower has been supplanted by newer infrastructure. No longer needed for its original purpose, the tower was disconnected from the water system in 2009.

The aging tower needs at least $510,000 in maintenance over the next 3-5 years to protect its structural integrity, according to Eagan Public Works Director Russ Matthys. City officials are loathe to pay for those maintenance costs, but don't want to lose a potential landmark—and a proven money-maker.

Although it no longer holds water, the tower hosts a handful of cell phone antennae for companies like Verizon, T-Mobile and Sprint. In exchange for the use of the tower, those companies pay Eagan; in 2013 alone, the city made $146,805 from the companies.

“Right now, it's in essence functioning as a cell phone tower," Matthys told the council on Tuesday.

At the meeting, Matthys presented three options to the council: Pay the maintenance costs and keep the tower, demolish the water tower and build a city-owned cell phone tower to continue to generate revenue or demolish the tower to develop or sell the land.

But the council sought other, more creative alternatives. Councilor Paul Bakken suggested the city simultaneously use it as a cell phone tower and large-scale hydro-battery, which converts stored water in the tower into energy via gravity and a turbine.

Mayor Mike Maguire wondered whether the tower should maintained and converted into a public art installation, with community input on the final designs for the structure.

In the end, the council took no action, but asked Matthys to dig deeper into the feasibility of various options.

Maguire also suggested the council seek input from the public on potential uses for the tower.

"It would be a shame not to take a month or two to shake the tree and see what falls out," Bakken said.

What should the city do with the Sperry Water Tower? Post your ideas in the comment section below.

M.M. May 15, 2013 at 12:20 PM
Keep the tower. I would be in favor of the hydro-battery idea, as long as the turbine is quiet. VERY quiet.
Paul Carlyon May 15, 2013 at 12:41 PM
Google "abandoned water towers" - lots of possibilities. Put it on EBay
Joe Cesarek May 15, 2013 at 02:59 PM
Keep the tower - paint a old town mural on it and make it a place to stop and remember the good old days..... it's historic and the cell compnaies can help pay for the upgrade.
Kirk Walztoni May 16, 2013 at 01:45 AM
Hmmm, so use energy to pump the ware into the tower, then convert the stored energy through a turbine at low efficiency? Someone needs a physics lesson.
Paul Bakken May 16, 2013 at 03:11 PM
Kirk, you are absolutely correct that pumped hydro loses energy in the storage and conversion process. Broadly speaking, pumped hydro can achieve anywhere from 50% to 70% effective conversion of the "useable electricity put in" to "useable electricity taken out." It depends on design and components, mostly. From a physics/chemistry standpoint, ANY conversion of energy from one form to another or to potential energy results in an efficiency loss. So, the reality that pumped hydro is not highly efficient should not come as a surprise to anyone. However (and this is the main point), the ECONOMICS of power generation, transmission, and storage can result in pumped hydro being a desirable application. First off, pumped hydro is usually used as a peak-load shedding generator. That is, water is pumped into the reservoir using off-peak, cheap power. The hydro generator is then placed on demand call by the G&T to operate during peak demand times. The price differential in the MISO market between peak and off-peak power, and the comparative costs for running other types of peak load generators (usually diesel) is where pumped hydro can find value. Moreover, recent changes in State law have placed additional mandates on entities such as Xcel regarding cleaner power generation. Accordingly, it is possible that a G&T like Xcel would choose to operate a pumped hydro battery even at an internal economic loss, because of regulatory compliance pressures and clean energy credits.


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