Low-flying helicopter surveying local bedrock

Published: Jan. 6, 2021 at 8:57 AM CST|Updated: Jan. 7, 2021 at 5:02 PM CST
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GREEN BAY, Wis. (WBAY) - Starting Monday, people in several Northeast Wisconsin counties may see a helicopter flying very low to the ground.

Helicopters will fly over Northeast Wisconsin in January as part of an effort to measure the depth to bedrock.

Through a partnership with several state and federal agencies, the Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) is set to use airborne electromagnetic technology to measure the depth of bedrock in a number of Northeast Wisconsin counties where groundwater problems have surfaced for years.

Generally, the problems have stemmed from farmers spreading manure in areas where there is shallow bedrock allowing the nutrients to seep into the groundwater.

“With this project, we’re going to have a very accurate and efficient way to provide depth to bedrock data to these farmers rather than having them have to go and verify or use an outdated map,” Rachel Rushmann with the DATCP Land and Water Bureau said.

Maps currently being used by farmers and state regulators date back as far as 1979 and relied on well construction reports or in-field probing.

But now, a low flying helicopter will tow a magnetic sensor to provide more accurate data of what’s below the surface. The low-flying helicopter will “tow a magnetic sensor that will provide accurate science-based data about below ground properties to update depth to bedrock maps,” reads a statement from the DATCP.

Over two weeks, the helicopter will fly nearly 2,000 miles of flight lines, a half mile apart in a grid pattern, collecting data every 100 feet, pinpointed by GPS.

The survey is focused on areas with Silurian bedrock. It’s composed of “highly fractured dolomite” that allows materials to reach groundwater.

“We didn’t have that in 1979. That was one of the more difficult things to ever do is know where is that data located in space and elevation,” according to David Hart with the isconsin Geological and Natural History Survey. “All of these abilities to manipulate and collect data are really helping us understand these systems better and help us protect our groundwater.”

The U.S. Geological Survey is leading the effort with help from the DNR, the Wisconsin Geological and Natural History Survey and DATCP.

“This project will update our maps and help landowners better understand how surface applications of certain materials can impact groundwater quality,” said Sara Walling, Administrator of DATCP’s Division of Agricultural Resource Management. “Protecting Wisconsin’s groundwater is essential to public health and to the state’s economy. We all rely on clean groundwater for drinking, irrigating crops, watering livestock, and processing foods.”

Helicopters will survey the counties of Brown, Calumet, Door, Fond du Lac, Kewaunee, Manitowoc and Sheboygan.

A map of the airborne study of bedrock in Northeast Wisconsin.
A map of the airborne study of bedrock in Northeast Wisconsin.(USGS)

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