Long ago, lead and zinc mining were a way of life for the people of Southwest Wisconsin. But the industries left their imprint in the region’s soils — an issue today’s residents must contend with.

Lead mining began in the state’s Driftless Area in the 1820s and quickly grew. In the second half of the century, the focus shifted to zinc, which is a less harmful metal but one that also contains lead in its ore. Mining of both metals left behind a toxic legacy. To help identify areas of possible contamination, a team from the Department of Soil Science has developed maps showing the aftermath of lead and zinc mining in the region.

The Digital Atlas of Historic Mining Features in Southwestern Wisconsin builds on digitized information about mine shafts, open-pit mines, smelters, abandoned rail lines, and other features from the 150-year history of lead and zinc mining in Green, Lafayette, Grant, and Iowa Counties.

The atlas only shows areas where contamination may be found, not the results of any soil tests for either metal. But just knowing where toxins could still be lurking is vital, says Geoffrey Siemering, a soil science researcher who led the project.

“The health effects of lead, especially for children, are largely irreversible,” he says. “Preventing exposure is the best defense, and although this is not great news for parts of the affected counties, we feel it’s essential to get the information out so people and communities can plan in order to minimize health risks.”

In addition to the four Wisconsin counties, the atlas refers to adjacent portions of Iowa and Illinois and a small area in southwest Dane County. According to the atlas, “From 1830 to 1871, the mining district was by far the most important lead producing area in the United States.” By the time mining for lead and zinc ceased in 1979, an estimated 600 million tons of ore had been extracted, leaving behind more than 2,000 mining and processing sites.

Lead is highly toxic to the human nervous system, kidneys, and other systems. So, as Flint, Michigan; Milwaukee; and other cities grapple with the health impact of lead water pipes and lead paint, lead contamination in the soil also needs to be considered, says soil science professor Doug Soldat BS’01, MS’03. Although not involved in the atlas project, Soldat has developed inexpensive lead-testing methods for urban gardeners.

The atlas is compiled from mining company records of where lead and zinc were prospected, mined, extracted, and smelted. As mines closed, their records were consolidated at the remaining mines. Eventually, six cargo vans hauled records to the Wisconsin Geologic and Natural History Survey, which digitized the Wisconsin data.

Former environmental studies graduate student Kyle Pepp, working with soil science professor Stephen Ventura, processed these records to start the new atlas.

Siemering, an expert in soil contamination, says the maps show an unfortunate overlap of lead and people. Early settlements revolved around lead mining, so people gravitated toward lead mines in Potosi, Shullsburg, Platteville, and many other population centers.

After ore was removed from near the surface, as is the case with lead, or from deeper underground mines, where zinc is found, it was concentrated by using water to separate the heavier, metal-bearing minerals. An estimated 70% of the original material removed from the mines was usually dumped in piles near the mine sites. Although not containing enough metal to be worth further processing, the ore waste, called tailings, still contains both lead and zinc at environmentally hazardous levels.

Later, rain and runoff carried lead and zinc from tailing sites to local wetlands, streams, and rivers. Today, the federal government lists six lead- and five zinc-impaired waterways in Southwest Wisconsin.

A second source of concern is the reuse of mine waste rock. “Photos from the 1920s show huge piles of rock that we don’t see now,” Siemering says. “Where did they go? No one hauls rock without a purpose, and these piles were ready sources of mate- rial for roadbeds and foundations.”

Because the maps were based on mining records rather than on-site measurements, soil tests would be required to determine actual lead levels, Siemering says. In theory, removing the contaminated soil could solve the problem, but hauling it to an approved hazardous waste dump can cost $100,000 per acre. In 1994, an engineer at the Wisconsin Department of Natural Resources estimated that a three-story pile of mine tailings in New Diggings, Wisconsin, could be cleaned up — for $700,000.

Capping contaminated soil with clean soil may be somewhat less costly, and it can work if done correctly and monitored regularly. And there are other options for reducing human exposure to lead in the soil, says Soldat.

“Scientific understanding of the environmental, health, and chemical situation can point to lead-abatement tactics that are safer, healthier, and more affordable,” he says. “So we are focused on finding realistic, affordable ways to reduce the hazard without bankrupting landowners.”

One tactic entails vigilance for signs of contamination. Farmers in Southwest Wisconsin have noticed yellowed, stunted crops — often a sign of zinc poisoning. Siemering says they can avoid plowing these areas and plant them with permanent cover, such as prairie plants, to minimize erosion.

In addition, future residential developers can use the atlas to avoid areas that are likely to have high lead concentrations in the soil. And for homeowners, Siemering wrote a UW–Madison Division of Extension report, Managing Mine-scarred Lands in Southwestern Wisconsin, that offers practical steps for minimizing exposure.

How the Badger State Got Its Name

Lead and Wisconsin go back a long way. Although explorers and fur trappers were the state’s first European visitors, the first European settlers were largely Welsh immigrants who began the hard, hazardous, and toxic underground mining of lead ore in the 1820s.

The first strikes, in Galena, Illinois, were supplanted by richer, more accessible finds across the border in Wisconsin’s Grant, Iowa, and Green Counties.

The Badgers (named for the pits that some lived in) and their occupation did more than garner the nickname “Badger State.” In 1836, the legislature of the Wisconsin Territory had its first meeting at Belmont, deep in lead country. And as towns grew up around the mining camps, names like Mineral Point and New Diggings reflected the primacy of mining. (New Diggings was named in reference to Galena, otherwise known as Old Diggings.)

Tower Hill State Park, near Spring Green, preserves a “shot tower,” a shaft through which workers dropped molten droplets of lead that solidified into balls as they fell. The tower made ammunition from the 1830s until 1860.

Lead from Southwest Wisconsin was likely used in paint, ammunition, batteries, pipes, and fungicide. But the lead boom was brief: In 1848 the California Gold Rush siphoned away miners eager to strike the precious metal, and the lead industry was already fading.

In the latter half of the 19th century, the mining focus shifted to zinc, a less toxic metal with ore that also contains lead. As mines “played out,” many were closed or sold to new operators. By the 1960s, the advent of regulations on air and water pollution raised costs and led to the cessation of metallic mining in Southwest Wisconsin by 1979.

But by then, the mining district in Lafayette, Iowa, Green, and Grant Counties, together with a spur in western Dane County, produced 600 million tons of ore, which supplied about 2 million tons of metallic lead and zinc.