MILWAUKEE (AP) –Thirty-year-old Conner Andrews has swum in Lake Michigan since his childhood days vacationing in Door County.

“It was always a huge deal for me to go to the beach and have fun there and enjoy the waves,” said Andrews, a Nashotah resident and former collegiate swimmer.

These days he gets the same feeling swimming at Milwaukee-area beaches. But he must pick his waters and timing wisely –î to avoid wading into a contaminated stew of pollutants that might swirl in some locations. That includes bacteria-laden stormwater and sewage flowing into local waterways.

Parts of the Milwaukee area rely on a combined sewer system to collect stormwater and sewage for treatment. But increasingly heavy rains can overwhelm the sewers, sending untreated waste into local rivers and Lake Michigan.

The overflows hinder locals who like to fish and swim. And they can contribute to beach closures and make people sick.

The wastewater flows intensified in 2018, even as the Milwaukee Metropolitan Sewerage District spends millions of dollars on a plan to eliminate overflows by 2035, state data show.

In 2018, the agency overseeing Milwaukee’s system, which serves 1.1 million people and 28 communities, saw six combined sewer overflows — the most events since 1999. Those overflows sent 1.2 billion gallons of stormwater and untreated sewage into rivers, canals and a stream that drain into Lake Michigan.

Milwaukee’s latest discharges come after the sewerage district spent $2.3 billion on pollution abatement in the 1980s and ’90s, including construction of what is now a 28.5-mile tunnel system to cut overflows into Lake Michigan.

The city is not alone in grappling with overflows.

Wisconsin in 2018 saw its most overflow events since 2010, with increasing volumes of discharged waste, Department of Natural Resources data show.

Experts say the problem plagues communities across the Great Lakes, a drinking water source for 48 million people in the United States and Canada.

Driving the spike: intensifying rainfall due to climate change.

Investment at all levels of government has fallen short in addressing aging sewer systems overwhelmed by the increasing flows.

“We’re seeing more extreme storms across the Great Lakes region, and you’ve got a recipe for some serious problems,” said Joel Brammeier, president and CEO of the nonprofit Alliance for the Great Lakes.

Andrews has sought to draw attention to Milwaukee’s water quality pollution challenges by organizing the Cream City Classic, in which contestants swim a 1.5-mile portion of the Milwaukee River that mixes with Lake Michigan. Organizers held the first race in August 2018, specifically choosing that time when heavy rainfall was thought to be less likely.

Rains have not thwarted the race in its first two years, but Andrews said he would not be surprised if that happens one day. Less than three weeks after the 2018 race, for instance, intense rainfall sent nearly 395 million gallons of stormwater and sewage into the Milwaukee River and other local waters.

As Wisconsin’s largest city, Milwaukee’s sewage system leads in wastewater releases.

In 2018, it discharged more than eight times more waste than systems in the rest of the state combined, due to wet weather, according to DNR data.

Milwaukee’s latest sewage surge into Lake Michigan follows decades of major progress on the issue.

About 8 to 9 billion gallons once overflowed from Milwaukee’s combined sewer system each year. That was before the sewerage district started building its Deep Tunnel in the 1980s, a 521-million gallon storage system 300 feet underground that collects sewage and stormwater until it can be treated and discharged.

The tunnel, built in three phases, dramatically cut overflows after 1994, the first full year its initial 19.4-mile phase went into service. It helps the district treat more than 98% of its wastewater in a typical year, keeping at least 128 billion gallons of polluted water out of Lake Michigan.

But increasingly heavy rains are now adding more stress to the city’s sewer system.

The Milwaukee sewerage district’s two wastewater plants collectively treat up to 600 million gallons of stormwater and sewage each day. But just one inch of rain across the district’s 411 square-mile service area equals more than 7 billion gallons of water.

“It’s when you get two inches of rain in 20 minutes that it overwhelms the sewer system,” said Bill Graffin, the district’s spokesman.

Steve Vavrus, senior scientist with the University of Wisconsin-Madison’s Nelson Institute Center for Climatic Research, said climate change is driving Wisconsin’s record rainfall. Last year was the wettest in the state’s recorded state history, while 2018 was third-wettest, according to data from the Midwestern Regional Climate Center.

Excluding Milwaukee, Wisconsin communities in 2018 discharged 150 million gallons of sewage and stormwater. That was the highest volume since 2010, the fifth-wettest year on record.

As of October 2019, 359 million gallons overflowed from those communities’ systems, while Milwaukee discharged more than 500 million gallons into waterways. That happened even as the Milwaukee district captured and cleaned a record 85.6 billion gallons of water.

Climate scientists expect the region’s rains will only intensify as worldwide carbon dioxide emissions speed earth’s warming. That could send more pathogens into the water, said Sandra McLellan, a professor with the School of Freshwater Sciences at UW-Milwaukee.

“Instead of that happening once a year, it’s going to happen two or three times a year,” she said.

In one extreme 1993 case, the waterborne-parasite cryptosporidium sickened an estimated 403,000 people in a five-county area around Milwaukee, according to the American Journal of Public Health. Later research linked 54 deaths to the outbreak, mostly AIDS patients.

The outbreak followed heavy rainfall, and experts speculated that human sewage and waste from slaughtered livestock and other animals contributed to the outbreak.

Milwaukee has invested $508 million in treatment upgrades and monitoring to prevent a future outbreak. But other communities remain vulnerable to pollution caused by heavy rains and runoff.

In a 2018 study, McLellan and other researchers found that gastrointestinal pathogens are “widespread in urban waterways following rainfall and 10-fold higher following (combined sewer overflows).”

Researchers are increasingly flagging high levels of E. coli at beaches in Milwaukee and elsewhere along Wisconsin’s Great Lakes shorelines. The bacteria arrive in human, bird and animal feces, triggering beach closures and advisories that have spanned more than 60% of summer days at Milwaukee’s South Shore Beach.

That beach and Maslowski Beach in Ashland are among those most prone to closure from unsafe swimming conditions, according to a July 2019 report from the advocacy group Environment America.

The contamination worries Melodie Phipps of Ashland. She loved to walk barefoot along the sandy shoreline of Maslowski Beach and swim in Lake Superior’s Chequamegon Bay. But that was before she learned that Ashland is among cities struggling with sewer overflows. Now, she steers clear of the water.

“I feel a huge grief –î huge sadness and a longing on a hot day when the humidity is 95% and you’re just sweating and it’s sunny,” she said.

Researchers at Northland College in Ashland regularly sample water quality along the city’s beaches. More than 30% of samples collected between 2014 and 2016 exceeded federal water quality standards for E. coli. The bacteria stemmed from a variety of sources, researchers noted.

In many cases, seagulls appear to be the most dominant contributor, said Matt Hudson, associate director with the Mary Griggs Burke Center for Freshwater Innovation at Northland.

McLellan said similar studies have shown high levels of E. coli at Milwaukee beaches come mostly from shoreline runoff and wildlife –î not sewer overflows. But the discharges are a prime source for the pathogens most likely to cause illness, she added.

“If I had to say what’s the most serious pollution sources, it’s sewage and any kind of human contamination.”

In 2012, Wisconsin’s roughly 600 publicly owned wastewater systems reported needing a collective $6.3 billion in extra investment to meet federal water quality goals –î nearly half for pipeline construction or repair and managing stormwater.

That includes Ashland. More than one-third of its sewer pipes are more than 50 years old, and nearly half are past their useful life, said John Butler, the city’s public works director.

Ashland’s wastewater treatment plant can handle up to 2,700 gallons per minute. But heavy rain events can increase flows 12-fold, overwhelming the plant. More than 6 inches of rain hit Ashland during Father’s Day weekend 2018, sending 15 million gallons of wastewater into Lake Superior.

Ashland’s overflows happen when water seeps into cracked pipes or into connections between the stormwater and sanitary sewer systems, Butler said.

Since 1991, the DNR has awarded more than $4.6 billion in loans and assistance for roughly 1,000 sewage and stormwater projects, with about 30% of funding going to Milwaukee, according to the state Legislative Fiscal Bureau.

Jim Ritchie, DNR environmental loan section chief, said funding requests are only increasing.

About 96% of U.S. spending on water and wastewater projects comes from state and local governments, according to the Congressional Budget Office. The federal government chipped in billions for water and wastewater programs in the 2019 fiscal year, but its investment has declined in recent years amid competing priorities in Washington.

Local governments are forging ahead with their own limited resources.

Beginning next year, Ashland plans to spend about $600,000 annually for deferred upkeep while also seeking state loans, Butler said. A U.S. Environmental Protection Agency grant also helped the city install a grassy channel at Maslowski Beach designed to capture and treat stormwater.

Along Lake Michigan, the Milwaukee sewerage district is pouring hundreds of millions of dollars into flood control along watersheds. It set a goal of zero overflows by 2035 by adding 740 million gallons of stormwater storage.

The district estimates it will cost at least $1.3 billion to install green roofs, rain gardens and other projects to capture water across its service area.

“We really live by the mantra that every drop counts,” said Kevin Shafer, the district’s executive director.

The nonprofit news outlet Wisconsin Watch provided this article to The Associated Press through a collaboration with Institute for Nonprofit News.