Heavy summer rains hit more than just the people living in flooded areas — they can halt lake recreation altogether when cities are forced to release untreated sewage into lakes and rivers.
Moose Lake is a case in point. The city's 88 campsites on Moosehead Lake fill up on weekends, but swimming and boating came to a standstill for two whole weeks in July because of heavy rains and flooding.
City officials closed the beach and advised no water contact after untreated sewage was released into the lake and the Moose Horn River — a result of the city's wastewater treatment system being overwhelmed by rainwater.
"You have to wait until it clears out because you get E. coli in here," said campground manager Joe Filipiak as he prepared for the holiday weekend last week.
The closure came at a bad time, he said, because the days that followed the flooding were among the hottest of the summer.
"People were calling like crazy hoping it would have gotten cleared up," Filipiak said.
The city tested the water and waited until E. coli levels were low before reopening the beach.
Heavy rains pummeled Moose Lake and surrounding areas July 11-12. Two-day measurements ranged from 4 to 9 inches across a wide swath of central Minnesota and western Wisconsin.
When it rains that much that fast, there's a limit to where all the water can go. It ends up in basements where some homeowners' sump pumps illegally empty it into drains. It also seeps into aging sewer pipes underground.
Everything that flows through the sewer pipes — toilet water, washing machine and sink water — is supposed to be treated, for obvious reasons. But there's only so much most wastewater treatment plants can handle, so when rainwater mixes with the sewage multiplying its volume, some of the water just isn't cleaned.
"Correcting these problems is very, very expensive," said Wendy Turri, wastewater manager for the Minnesota Pollution Control Agency.
Turri said the agency gets a call every time sewage is released, and trends showing more heavy rain events in the state increase the likelihood of treatment plants being overwhelmed.
"This is a statewide issue. It's definitely about aging infrastructure and more rain," she said.
The fact that heavy rains make the sewage highly diluted should alleviate some concerns. "That said, we're trying to minimize it," she said.
The heavy rain-sewage situations are happening hundreds of times a year in Minnesota, though we usually only hear about it when there's a public health threat. July's heavy rains came just four years after the 2012 flood, which hit Duluth and Moose Lake especially hard. Even more untreated sewage was released into Moosehead Lake then, stopping water recreation.
Steve Ellingson, who lives on the lake with his wife and 9- and 6-year-old sons, said his family has been lucky not to have any flood damage from either 2012 or this year. But after the June 2012 storms, Ellingson said they didn't let the boys in the water the rest of that summer, or the following summer.
"Our boys were younger at that time, and their choice of drinking lake water wasn't always the smartest, or putting their hands in their mouth, things like that," Ellingson said.
Even four years later, he said he and his wife weren't in a hurry to let the boys jump in after the "all-clear" in July. But unlike the first flood, they've still gotten a chance to enjoy summer lake life in recent weeks.
The flooding this summer came as a surprise to city residents, some of whom had just finished cleaning up damage from 2012, said City Administrator Tim Peterson.
No one was expecting to see another flood so soon, he said.
"A 500-year flood coming every four years is not the math that I was taught," Peterson said. "We definitely don't need any more rain events like that."
If there's anything that comes close, the city will be better prepared. Peterson said a new main lift station should help prevent both sewage releases and sewage backups into people's homes. Sewage backups were a problem in 2012.
"We looked at how high the water level got in 2012, and we built our lift station above that and then some," Peterson said.
Other cities have also invested heavily in new infrastructure to reduce sewage releases. After years of frequently releasing untreated sewage into Lake Superior, Duluth officials spent more than $160 million on new infrastructure, including backup storage tanks to hold massive amounts of water during a heavy rain.
But that system still was unable to handle storms in March that fell on already saturated ground. And so, sewage from Duluth and the Western Lake Superior Sanitary District flowed into Lake Superior once again.
WLSSD director Marianne Bohren said the mild winter was a factor because moisture that normally would have been snow fell as rain.
"We had rain in every month of the year last year," she said. "Generally you don't have rain in December, January and February."
Was it an El Nino fluke? A sign of what's to come under climate change? Researchers say it's likely both, though it will take time to fully analyze.
Whatever the reason, the MPCA is drawing up maps showing which of the state's wastewater treatment plants are most vulnerable to heavy rains and flooding.
Yet cities and state officials have to weigh the costs and benefits of any improvements, because not every sewage release can be prevented, said Bill Priebe, wastewater engineer supervisor for the MPCA.
"It'd put a city out of business and bankrupt for them to put in pipes big enough to carry every potential rainfall event, and folks just can't afford to do that," he said.