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UW scientists map areas of historic lead, zinc contamination

Tom Hunt, an expert on Wisconsin's history with lead and zinc mining, walks the grounds of a former lead-processing site in Dodgeville on Oct. 15. At left is a slag furnace, built in 1876, that was once used to melt lead from nearby mines. (John Hart/Wisconsin State Journal via AP)

Tom Hunt, an expert on Wisconsin’s history with lead and zinc mining, walks the grounds of a former lead-processing site in Dodgeville on Oct. 15. At left is a slag furnace, built in 1876, that was once used to melt lead from nearby mines. (John Hart/Wisconsin State Journal via AP)

By CHRIS HUBBUCH
Wisconsin State Journal

HIGHLAND (AP) — The first year Kurt Menke planted soybeans in a 22-acre field at the edge of town, he noticed something odd: His crop came up healthy but then part of it in one particular area later died.

Menke’s mother brought the failure to the attention of Chris Baxter, a soil scientist at UW-Platteville. Baxter’s subsequent testing suggested zinc was present in the soil at an astonishingly high concentration. Instead of the 10 to 300 parts per million that would be considered normal, Menke’s soi had closer to 15,000 parts per million. That meant zinc made up 1.5 percent of the soil.

Baxter discovered the reason in historic maps: Menke was farming on mine tailings, invisible remnants of an industry that had been the economic engine of this corner of southwestern Wisconsin in the 19th century but had vanished years before he was born.

“The whole community was surrounded by mines of various sizes,” Baxter said.

It has been 40 years since Wisconsin’s last zinc mine closed and nearly two centuries since the Driftless area was the country’s primary source of lead. But the toxic remains are there, often undetected, in the soil.

And it isn’t just a cause for concern for farmers.

Where there’s zinc, there’s lead, which even in small amounts can lead to serious health troubles, especially in children. And there’s evidence that people are living on top of contaminated soils, said Geoffrey Siemering, a soil researcher at UW-Madison.

“Every town out there is there because of lead mines,” he said. “All the major population centers are sitting right on top of old mine features.”

Now, University of Wisconsin soil scientists are attempting to document that history and bring attention to place areas where lead and zinc residue could threaten plant and human health.

Using archival company records, researchers have pinpointed more than 2,000 sites that over time produced more than 600 million tons of ore. Their work has led to the production of a digital atlas mapping possibly contaminated sites. The hope is that farmers, developers and residents will turn to the atlas when making land-use decisions.

Siemering said the idea for the “Digital Atlas of Historic Mining Features in Southwestern Wisconsin” came from talks with Baxter, who mentioned he’d been asked for advice on several cases in which farmers were dealing with similar instances of mysterious contamination.

“The mining industry has been gone from this part of the state for many, many years,” Baxter said. “Land changes hands. Older farmers may have known that was a mine there on the back 40. Today they might be renting land or having purchased new land.”

Relics of the region's mining history are displayed in the house of Tom Hunt in Ridgeway on Oct. 15. The artifacts he has on display include a piece of mined lead, a remnant of melting procedures and a brick that had been part of a lead furnace. Hunt is an expert on land reclamation and Wisconsin's lead- and zinc-mining history. (John Hart/Wisconsin State Journal via AP)

Relics of the region’s mining history are displayed in the house of Tom Hunt in Ridgeway on Oct. 15. The artifacts he has on display include a piece of mined lead, a remnant of melting procedures and a brick that had been part of a lead furnace. Hunt is an expert on land reclamation and Wisconsin’s lead- and zinc-mining history. (John Hart/Wisconsin State Journal via AP)

Country’s primary source of lead

Before it was the dairy state — before it was a state at all — Wisconsin was known for its mineral deposits, rich veins of lead and zinc forced by intense heat into crevices in limestone bedrock and even up to the surface.

The Ho-Chunk and other Native Americans knew where to find chunks of “float lead” sulfide, or galena, which they would trade with French fur traders in the 1680s, according to the Wisconsin Historical Society.

As the demand for lead — used to make pewter utensils, paint and, primarily, ammunition — grew in the early 1800s, the rich reserves lured settlers up the Mississippi River into what are now Grant, Crawford, Iowa and Lafayette counties, giving rise to places like Mineral Point, Lead Mine and New Diggings.

By 1829, more than 4,000 miners were producing 13 million pounds of lead a year, and the Driftless Region was the nation’s primary source of the heavy metal.

These early pick-and-shovel miners dug shallow “badger holes” and melted ore in the brick furnaces that had once dotted the landscape.

“The getting was good on the surface initially,” said Tom Hunt, a retired UW-Platteville professor of land resource management. “They scoured the land. It’s really tough to find anything these days.”

As the topmost deposits were depleted, miners began cutting vertical shafts into the limestone to reach deeper reserves, a technique made possible by the arrival of Cornish immigrants who brought winches, pumps and other mining technology.

Lead production peaked in the 1840s, but was soon supplanted by the mining of zinc, another mineral found in the same underground ore.

Zinc mining required advanced techniques, which led to the construction of mills to crush the ore into gravel-size particles and separate out the metals.

The waste rock, or tailings, were piled near mine sites and often scavenged for roads and buildings. They were also left exposed to rains, which could wash small pieces of rock — still rich with lead and zinc as well as arsenic and chromium — into nearby soil or creek beds.

“Those metals haven’t gone anywhere,” Siemering said.

A planning tool

As zinc production tailed off during the 20th century, mines closed, and the accompanying records were consolidated with the remaining companies. After the last zinc mine was shut down in 1979, six van loads of records were hauled off to the Wisconsin Geologic and Natural History Survey, which preserved those from Wisconsin. (The rest were sent to Illinois.)

“It was buried in their database,” Siemering said. “You couldn’t access it.”

Working with Siemering and his fellow soil scientist Steve Ventura, a graduate student dug through the records, which they merged with modern land-use data.

The maps show the locations of historic mine features, including bore holes and mine shafts, as well as long-gone rail corridors where ore would have been crushed before being shipped off for smelting, as well as places where surface mining took place.

Siemering says he hopes the atlas will eventually be used by officials when they are planning new developments. It could help steer future residential projects away from places that are most likely to be contaminated, he said.

Cleaning up contaminated soil by removing or capping it can minimize the risk of exposure, but the costs — up to $100,000 an acre — are out of reach for most people and require environmental permits. Researchers are instead placing a priority on cheaper lead-abatement schemes, which can reduce risk without bankrupting landowners.

Amy Bares, an engineer for the firm Town and Country Engineering, consulted Siemering’s data when designing a new water tower in Grant County.

“What we were really doing is some due diligence,” she said. “We know that area is rich with mining history, so we wanted to make sure the couple of sites we were most interested in weren’t over a mine shaft.”

Copyright 2019 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

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