Frozen septic systems are emerging as an unexpected consequence of climate change in Minnesota — one that is bedeviling homeowners across the state and could soon cost taxpayers more for the repair and maintenance of fragile rural roads.

The cause is a dramatic long-term decline in insulating snow early in November and December. Combined with still-freezing conditions, that drives the frost line deep underground — well below septic pipes and drain fields.

As a result, thousands of the half-million Minnesotans whose homes, cabins or businesses rely on underground septic tanks are facing a costly solution: pump their tanks more often and use their showers, washing machines, dishwashers and toilets less. And this year isn't the worst in a recent history of freeze-ups, septic haulers say.

The problem grows especially acute in March and April because Minnesota imposes local road weight restrictions for heavy trucks like the massive septic "honey wagons." That can leave homeowners stranded as they watch their septic tanks fill up with nowhere for the liquid to go. Except back in the house.

"We tell people, pretend like you're camping," said Lori Ende of Ende Septic Services in Rogers.

Over the years, the increasingly aggravating problem has prompted Minnesota governors to issue annual executive orders giving septic trucks an exemption from weight restrictions. Now the Legislature is considering a bill that would make that exemption as permanent as Minnesota's woefully inadequate early winter snow cover.

"If we aren't given the exemption, do we consider breaking the law to do what we know is in the best interests of the health and safety of our customers with raw sewage backing up into their homes?" Cindy Tiemann, co-owner of Fiedler's Your Pumping Specialists in Royalton, wrote in a recent letter to legislators. "Or do we tell them there is nothing we can do until we receive authorization?"

This winter, Tiemann's company serviced more than 450 residences with frozen lines or drain fields, and half lived in areas with seasonal road limits, she said. Without the governor's exemption, that means 225 would have had to wait until thaw for a pump-out.

But engineers say spring weight restrictions, which affect mostly county and township roads, serve a purpose — to protect roads from wear when they are most vulnerable. Allowing more road use is essentially a cost shift from industry and homeowners to taxpayers, especially in rural areas where septic tanks are common and the tax base is small.

"Everyone wants to use the biggest vehicle they can use," said Anne Finn, a lobbyist for the League of Cities. "But it's really beating up the roads."

The problem has been building almost invisibly for decades because it's been both gradual and hard to see.

Some parts of Minnesota have plenty of snow, and some winters bring a lot that falls early and stays late. But according to Kenny Blumenfeld, Minnesota's state climatologist, rising average winter temperatures have led to a dramatic change in snow cover. The average annual snow depth in Minnesota between Nov. 1 and March 31 has dropped by 20 to 30 percent, comparing the past 18 years against the period 1970 to 1999. And the total number of days without snow cover has increased even more — 30 to 50 percent, and even higher in some places.

Loss of insulation

In Duluth, for example, the average number of March days without snow cover increased from 1.5 in the 1970s to seven in the 2010s, Blumenfeld said. "The once-dependable December snow cover isn't what it used to be," he said.

Yet conditions are still cold enough to drive the frost line deep into the soil. "This year it's 36 to 50 inches" in some places, said Tristan Ende of Ende Septic.

At the same time, septic systems and home designs have changed in ways that can make the problem worse. High-efficiency furnaces, which produce more water, create a slow, steady drip into sewer lines that can easily freeze. The addition of pumps on septic systems means tanks and drain fields are closer to the surface. And so-called mound systems, which protect groundwater by placing the drain field higher, also place the tank higher.

For Justin Vagle of Lakeville, it's been an expensive learning experience. He grew up in a suburb with a sewer system. He didn't think twice about what it meant to buy a house with a septic tank, and for a time it all worked fine.

But this year it froze up. When his pump alarm went off, he called Swedlund Services in Belle Plaine. They came out and replaced the pump ($1,200). But that didn't fix things.

The problem could be that his mound and drain field are frozen, and the company could pump hot water through them ($1,000). But that won't help if a pipe is frozen, leaving Vagle a gambler's choice. He could bet that defrosting the mound would do the trick. Or he could pump the septic tank every three weeks ($250 a pop) and hope for an early spring.

He's still pumping.

"I assumed usually in March we hit some 50-, 60-degree days," he said. "Now we are well over that $1,000."

Move the kennel

Septic service operators say homeowners can take steps to help prevent freeze-ups, guidance that they now offer routinely. Letting the furnace hose drain into a bucket in winter rather than the sewer can prevent line freezes. Straw and mulch around drain fields and pipes can do the same insulating job as snow. And, they say, homeowners should keep pets and people off septic lines so they don't compress the snow, mulch and soil, which reduces insulating power.

"I had a lady on the phone today," said Travis Thoreson of TRT Excavation and Septics in St. Francis. "She had a dog kennel over the line, and that drove the frost down."

Road engineers and local officials argue that wider adoption of such measures might be a better solution than another heavy truck exemption.

"The cost of a mile of new pavement is a minimum of a million dollars," said Finn of the League of Cities. "When you start shortening the life span of a road, it gets expensive and falls to property-tax payers."

Glenn Olson, president of the City Engineers Association of Minnesota, said improved pumping schedules would be a better option. In some densely packed suburbs, hundreds of septic trucks go in and out of neighborhoods monthly, he said.

"The damage could be significant," he said.

And septic companies could use smaller trucks that meet spring weight restrictions, even though that might cost them or their customers more money, he said. Service operators say there will still be problems, and that they would use the exemption sparingly and only in emergencies.

Thoreson, however, said there is a permanent solution that would do away with questions of who pays, and that would work regardless of the unpredictable consequences of climate change and frost lines.

Build better roads.

"There should never be a five-ton road. They should all be seven and above," he said. "If you make 'em more durable you'll have less repairs."

Josephine Marcotty • 612-673-7394