On the last day of August, Jeff van den Noort spotted thick swirls of neon green film coating the water just steps from his home in Vermont. He waded in up to his ankles and dipped a jar to get a sample of the scum.

It wasn’t the first time he’d seen the slime. Since his parents bought the house on an island in Lake Champlain in 1966, van den Noort has spent part of nearly every summer in this quiet spot. Back then, the lake was clear.

But he began to witness the water’s deterioration as he grew older, especially after he moved into the home full time in 2010 to care for his ailing mother. That day in late August was the worst he’d seen all summer.

Later that week, van den Noort grabbed a bucket, a few Mason jars and a smartphone and got into his rusty Saab. He drove past the boat launches, frozen-in-time general stores and windswept pastures of the lake’s islands in northern Vermont and stopped at four other spots along the shore. Each time, he collected some murky water, gauged how thick the muck was, took a few photos and jotted down the weather conditions. He then uploaded his report to an online database.

Van den Noort was one part of a large volunteer effort to monitor a problem that has plagued Lake Champlain, which supplies drinking water to about 200,000 people. In recent decades, blooms of potentially toxic cyanobacteria, often called blue-green algae, have killed pets, forced beaches to close and hurt business and property values along the shores of this iconic Vermont feature.

“I just don’t feel like enough is being done,” van den Noort said. “And I think the state needs to take this seriously.”

Just over a decade ago, state leaders seemed to be doing just that. In 2015, then-Gov. Peter Shumlin stood a few feet from Lake Champlain by the Burlington waterfront and signed Vermont’s Clean Water Act. It promised to tighten limits on pollution and provide funding to clean up the state’s waterways.

The move was a response to ratcheting pressure from environmentalists and the U.S. Environmental Protection Agency. The EPA had been telling Vermont officials for years that they needed to take much stronger action. In 2016, the agency finalized tougher cleanup targets that the state must meet by 2036.

But after 10 years and nearly a billion dollars spent on water quality projects and programs, Vermont’s cleanup effort is faltering. In a little-noticed letter to the head of Vermont’s Department of Environmental Conservation last year, the EPA’s regional administrator warned that the state was “not on track” to meet its cleanup goal and would need to more than double its annual pace.

Halfway through the two-decade timetable, Vermont has achieved only 35% of the goal, according to the state’s most recent estimates. And the steps that Vermont has taken to get there, such as upgrading sewage treatment plants, represent “low-hanging fruit,” Eric Perkins, a former EPA official involved in setting the target, wrote in an email in response to questions from Seven Days and ProPublica.

The culprit behind these blooms is phosphorus, an element that is an essential building block of life, present in all organic matter. But too much of it has been pouring into the lake from farm fields saturated with fertilizer and manure, dirty stormwater, and raw sewage from treatment plants overwhelmed by heavy rains. That has tipped the lake’s ecosystem out of balance, spurring the growth of microorganisms that turn shallow bays and shorelines into no-go zones.

Ingesting cyanobacteria-laden water can cause vomiting, diarrhea, dizziness and liver damage, while skin contact can lead to rashes. Researchers have also detected possible links between chronic exposure to cyanobacteria and heightened risk of Parkinson’s disease and ALS, also known as Lou Gehrig’s disease. The algae blooms can also deprive fish and other aquatic life of oxygen.

While some areas of Lake Champlain have seen incremental improvements in phosphorus concentrations and cyanobacteria blooms, other parts of the lake are getting worse. Seven of the lake’s 15 sampling stations have exceeded the EPA’s annual phosphorus limits every year since 2015, a Seven Days and ProPublica analysis of lake monitoring data through 2025 shows. Four stations recorded higher average phosphorus levels over the past decade than in the decade before, including in the southern part of the lake and its northeast arm.

In September, the Department of Environmental Conservation reported to the EPA that in two northeastern sections of the lake most chronically plagued by phosphorus runoff, the state is not nearly on track to meet its targets. The department specifically........

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