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Even good farming may pollute groundwater

By Kate Golden
Wisconsin Center for Investigative Journalism

Crevices in this frozen Door County farm show how water can travel so quickly through cracks in the bedrock that it reaches aquifers before any pollutants can be filtered out. (Photo provided by Door County Soil and Water Conservation Department)

Crevices in this frozen Door County farm show how water can travel so quickly through cracks in the bedrock that it reaches aquifers before any pollutants can be filtered out. (Photo provided by Door County Soil and Water Conservation Department)

Two new studies of private well water in Kewaunee County have linked contamination to fertilizer, livestock manure and human waste.

One study found the potentially toxic salmonella, which could come from people, livestock or wild animals, in drinking water.

“I’ve never seen groundwater like this before,” said Mark Borchardt, a microbiologist with the U.S. Department of Agriculture’s Agricultural Research Service who co-wrote the study. “It’s a really high hit rate for contaminants.”

In northeastern Wisconsin — parts of Kewaunee, Brown, Calumet, Manitowoc and Door counties — dirty water can travel quickly down to aquifers without getting filtered along the way because the soils are so thin and the karst bedrock so cracked.

As of May, 30 percent of the county’s wells had been found unsafe due to bacteria or nitrates.

Since 2006, 66 Wisconsin wells have been or will be replaced due to livestock manure contamination, according to state Department of Natural Resources data. Three-quarters of them were in areas with susceptible karst geology, but none in Kewaunee County.

In the town of Lincoln in Kewaunee County the soil is particularly thin, and half the wells used by 334 households have tested as unsafe. Potential culprits include human waste from septic systems and fertilizers, manure or other waste spread on fields for agriculture.

The County Board is considering an ordinance that would prevent contamination by limiting the spreading of waste on thin soils in winter.

Even good farming can pollute

Two researchers who tracked 10 town of Lincoln wells each month for a year estimated that agriculture contributed 96 percent to the high nitrate level in the groundwater, and septic systems contributed 4 percent. The county’s 42,000 cows produce as much waste as 1 million people. Kewaunee County has a population of about 20,500.

Researchers Kevin Masarik, an outreach specialist with the University of Wisconsin-Extension, and Davina Bonness, a Kewaunee County water quality specialist, concluded that agriculture is tainting private wells even when farmers follow generally accepted farming practices, including nutrient management plans that limit how much fertilizer, manure or other waste can be added to fields and when it can be added.

But Dairy Business Association lobbyist John Holevogt raised questions about the conclusion.

“I don’t think that these studies show that nutrient management plans are inadequate,” he said, “in large part because they don’t clearly show what the source of the nitrogen is.”

The DNR and the Department of Agriculture, Trade and Consumer Protection regulate agricultural waste. DATCP spokeswoman Donna Gilson said agency officials have not had a chance to fully review the studies and would not comment on them.

But DATCP and DNR officials agreed that nutrient management plans are designed to minimize, not eliminate, pollution.

“The idea of having absolutely no runoff, whether to surface or groundwater, is a very difficult standard to meet,” said Keith Foye, who runs DATCP’s Land and Water Bureau, “and that’s not how the technical guidance is set up.”

Asked whether the current standards for farming are adequate to protect the karst area’s groundwater, DNR nutrient management specialist Andrew Craig said it is difficult to determine.

“We have to implement the rules the Legislature passes,” he said. “They’re designed to be protective. They could be in some situations; they may not be in others.”

Bonness and Masarik’s study examined the month-to-month variation in water quality in wells with a history of contamination. The results varied so much, the researchers found, that testing just once a year may give homeowners in that area a “false sense of safety.”

In a second study, a pilot project testing 10 wells in Kewaunee County, two were found to be contaminated by cattle manure, two by human waste, and one by both.

Salmonella, an uncommon finding in groundwater, turned up in four of the 10 wells, Borchardt said. One well also tested positive for Campylobacter jejuni, another bacterium that can make people sick.

The genetic tests cannot distinguish between live and dead bacteria. Live bacteria can make people sick, but “if they’re dead, it’s not an immediate public health concern,” said Chuck Czuprynski, a professor who directs the UW-Madison Food Research Institute.

Holevogt, the dairy lobbyist, focused on the presence of human waste in the wells.

“A lot of the contamination,” he said, “doesn’t come from dairy at all.”

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