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County decides geothermal system too expensive

A proposal for a geothermal heating and cooling system for St. Croix County Government Center has been abandoned by the Finance Committee.

Instead the committee voted last week to go with a high efficiency water-cooled chiller and condensing-style boiler. The installed cost is estimated at $1,672,500. Annual energy costs for the system are estimated at $155,200.

Administrators had been considering a geothermal option -- high efficiency water-to-water heat pumps -- and had test wells drilled for that alternative, but in the end decided it was too expensive.

In his most recent estimates, Karges-Faulconbridge Inc. engineer Robert Aschenbrenner predicts geothermal would cost $675,000 more than the chiller/boiler system. Since the savings on utility costs would be less than $9,000 a year, the payback period is roughly 75 years.

"The well drilling process is diesel intensive," said Aschenbrenner. With the cost of diesel hovering at $4.60 a gallon and higher costs on other materials, the price shot above earlier estimates, he said.

"At one time it looked like we were on the verge of something really good," summarized Supervisor Buck Malick. "(But) the world of geothermal has changed with petroleum costs."

The geothermal system considered by the consultants would have used a well field. Supervisor Sharon Norton-Bauman said other geothermal systems use a strip of land and a coil system.

The heat transfer for those "slinky fields" isn't as good as with vertical bores, said Aschenbrenner. Also the coil systems use more land and nothing can be built above them, he said.

Geothermal could have an advantage if natural gas prices spike, said the engineer.

Decision-makers are reacting to a heating/cooling system that is having problems, but they don't know if there will be a need to expand the Government Center, said Supervisor Daryl Standafer. He worried about making piecemeal decisions without knowing what the big picture is.

"We're not backing ourselves into a corner. That's what I want to hear," he said.

"I think you need to look at what you've got," replied Aschenbrenner, "and you've got to replace it."

While he admitted that it could save money if supervisors knew where they are going, Aschenbrenner said they can also run into problems planning for things that don't happen.

"This system is modular, and we can build on," said Facilities Manager Art Tobin, explaining that the chiller/boiler option can be adapted if the building is expanded.

Supervisors also asked the engineers to gather more information on an option that would make ice during the night to help cool the building during the day. The installed cost of that alternative is $67,000 with an estimated payback time of 14 years.

"There's efficiency, and there's cost savings," commented Aschenbrenner. He said the ice-storage option uses a little more energy but shifts some utility use to nighttime when the rates are lower.


Tobin reported that summer storms damaged roofs on six buildings at the Health Center campus in New Richmond, and plans are being made to repair those.

He said the total cost of the work is $180,000. The county must pay just a $15,000 deductible.

Proposals were received earlier in July to replace the Government Center roof, but Finance Committee members want more information before choosing a contractor. A decision is expected in August.

In the meantime, administrators preparing to borrow money for building projects were directed to plan to borrow up to $500,000 for the Government Center roof.

Tobin said the 15-year-old roof "leaks terribly" and buckets have been set up in the building to catch water.