Geologists and geophysicists gathered on the tarmac at Robertson Airport in Plainville Tuesday to watch a small plane take off.
The orange and white plane, which can seat nine passengers, was filled with hundreds of pounds of geological surveying equipment, instead of people.
The plane is part of an aerial mapping of large swaths of New England, conducted by the U.S. Geological Survey (USGS). Nearly the entirety of Connecticut will be included in the mapping, which will take about four months.
“The goal of the project is to fly over the area and collect data that tells us about the rocks below,” USGS research geophysicist Anji Shah said. “We do this by looking at magnetic fields and by looking at natural, low level radioactivity.”
One of the survey’s purposes is to identify the presence of the mineral pyrrhotite in Connecticut’s rock beds. Pyrrhotite is the mineral that has caused crumbling foundations in thousands of Connecticut homes.
“By mapping out this pyrrhotite, you can find out where it is, and then once the data are collected, it's made available to the public,” Shah said. “Then anyone doing any sort of quarrying will know where that pyrrhotite is, and then they'll know to not use it in construction.”
Connecticut, Rhode Island, New Hampshire, Massachusetts and slivers of Vermont are included in the survey, Shah said.
The mapping will be helpful for more than avoiding pyrrhotite in concrete mixtures, Shah said.
“We're also learning about the broader geology across the state, and that can have a lot of different applications,” Shah said. “If there was a small earthquake, maybe we'll be able to map out the fault on which that earthquake occurred. Or suppose there's a group that wants to build a tunnel in a certain area, then they want to know, well, what's the rock here?”
Homes and businesses can still be built on land containing pyrrhotite, but soil containing the mineral cannot be used to make concrete foundations.
Quarries in Connecticut now test their deposits for pyrrhotite. This practice has decreased the risk of pyrrhotite being used in the concrete mixture to create foundations, according to Connecticut State Geologist Meghan Seremet, who works for the Department of Energy and Environmental Protection (DEEP).
About 30,000 homes in Connecticut are impacted by crumbling foundations and repairs are expensive, according to Massachusetts state geologist and University of Massachusetts Amherst professor Bryan Yellen.
“One thing an intervention is to replace foundations and estimates range as high as $300,000,” Yellen said. “By learning about one place, we can really extrapolate what's happening across the region, specifically with respect to crumbling foundations caused by this corrosive mineral, pyrrhotite.”
The mapping process is called an Earth MRI, and operates similar to a medical MRI. The radars within the plane pick up a roughly 300 foot radius at each pass, so the planes move over the land in rows similar to lawn mowing patterns.
Pilots will take off each day from Robertson Airport in Plainville and map for about six hours. Once the mapping is complete, public data and maps will be ready about six months later.
