Conductivity tests planned for county geothermal system

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Tests will be conducted in early May to determine the conductivity of the ground in anticipation of installing a geothermal heating and cooling system at the St. Croix County Government Center.

Building Services Director Art Tobin said the test will involve installing one vertical heat exchanger to a depth of 200 feet.

At a minimum, the test will be conducted for 36 hours. Bids for the work are due by noon Friday, April 11. Construction, testing and reporting are to be completed within 30 days of contract signing.

The geothermal system proposed for the government center would involve 30 wells on 2.5 acres, said Tobin.

He said each “well” is a sealed system, involving a looped tube in a vertical hole. Concrete is used to fill between the heat exchanger and the sides of the holes.

“Nothing is released into the ground. Nothing is taken from the ground,” said Tobin.

He said the city of Hudson requires a 1,200-foot protection zone around each of its well heads, and both the test bore and the eventual well field will be outside that area.

In February the Finance Committee voted to authorize up to $1,500 for engineers to prepare specifications for test wells and conductivity tests and to spend up to $10,000 to hire a company to drill the well and do the test.

The geothermal system will replace a heating and cooling plant that maintenance workers say has become undependable and expensive to repair.

Specifications for the test bore can be viewed by going to the county Web site: www.co.saint-croix.wi.us/ and clicking on “Procurement.”

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