When the aging nitrate-removal plant in Clear Lake, Minn., started failing, the city took its problem well offline and decided it had to dig a new one. That's an expensive undertaking for a town of 610 people described by public works director Dustin Luhning as a "bedroom community with a lot of farms."

Now, with a $1.3 million loan from the state, Clear Lake has finally broken ground on a well it hopes will rid them for good of the farm chemicals — a triumph for Luhning.

"I've been trying to get this drilled since roughly 2013," he said.

Clear Lake is one of at least 10 Minnesota communities forced to install costly nitrate-removal systems or drill new wells to find clean water in the state's ongoing battle with growing nitrate pollution. Many more now face undertaking the burdensome projects.

A report released Tuesday morning by a national environmental group says that one in eight Minnesotans are drinking nitrate-tainted tap water.

Years of unchecked pollution from farm chemicals have brought Minnesota "to the brink of a public health crisis," according to the Environmental Working Group, which based its findings on public records from the state Department of Health and Department of Agriculture.

"We should be moving faster to prevent it from entering crisis mode," said Sarah Porter, a senior mapping analyst in the organization's Minneapolis office and co-author of the study.

The group's one-in-eight count includes wells where at least one test in recent years detected nitrate above 3 milligrams per liter, the level at which the state Department of Health deems nitrate concentrations to be from a human source. The state and federal health limit for nitrate is 10 milligrams per liter, or 10 parts per million.

One of the most surprising findings, the authors said, is the extent of contamination in private wells across the state.

The analysis found that more than 3,000 Minnesota households drink from private wells with concentrations of nitrate at or above 10 milligrams per liter.

But only a fraction of the estimated 200,000 private wells around the state have been tested, said Anne Weir Schechinger, a senior economic analyst in the Environmental Working Group's Minneapolis office who co-authored the report.

"I think we would all be surprised how much nitrate is in these wells if we actually tested them," she said.

Drinking water high in nitrate has been linked to different types of cancer, elevated heart rates and a potentially fatal condition known as blue baby syndrome in which infants are deprived of oxygen. Most of the nitrate contamination comes from nitrogen fertilizer applied to row crops, as well as manure spread as fertilizer.

The Environmental Working Group analyzed five sets of state and federal data to create interactive maps so the public can easily find the drinking water information in one place.

The analysis focuses on groundwater and includes public water systems, community systems such as those serving a mobile home park, and private wells.

A separate study will examine nitrate concentrations in surface waters such as lakes and streams.

The group also said it wants to see the state's legal nitrate limit reduced because of new research linking even the lower levels of the contaminant to increased risk of colorectal cancer, for example.

The analysis comes as Minnesota begins formal enforcement of the Groundwater Protection Rule, a landmark provision aimed at curbing the use of nitrogen fertilizer in certain strategic areas.

On Wednesday, the state Department of Agriculture will post on its website official maps of the land subject to the state rule.

They will show growers exactly who is affected, although earlier maps gave many farmers a good idea.

Years in the making, the new rule prohibits applying commercial nitrogen fertilizer in the fall or on frozen fields in parts of the state with soil vulnerable to leaching chemicals, such as karst or sand, and in drinking water supply management areas that already have elevated nitrate levels.

The rule also establishes an enforcement program, albeit one that relies heavily on encouraging farmers to adopt greener practices.

Warren Formo, executive director of the nonprofit Minnesota Agricultural Water Resource Center, whose members include about two dozen major agriculture groups, said farmers support the new nitrogen fertilizer restrictions. He said he's optimistic the changes will have an impact on water.

"We know that farmers are taking it very seriously," he said. "The discussion about the rule has really generated a lot of conversation between farmers. Farmer are receptive."

Conservation groups and some agricultural experts have criticized the rule as too narrow. It doesn't address manure or contamination of private wells, and ultimately only covers only about 13% of the state's total cropland.

It also focuses only on when commercial fertilizer is applied and not how much is applied.

That's a big miss, retired University of Minnesota soils scientist Gyles Randall said when the final rule was first announced, because surveys show Minnesota farmers use too much commercial nitrogen.

The Environmental Working Group cited a 2014 survey by the state Department of Agriculture showing that 61% of fields across the state were getting more nitrogen fertilizer than the amount recommended by the U, and 71% of fields were getting more manure nitrogen than recommended.

Still, the advocacy group praised the rule as a strong first step, and said other states are watching to see how it's implemented.

"The Groundwater Protection Rule has its issues, but it's still a first in-the-nation rule," Weir Schechinger said.