Listen: Leaking septic systems an invisible but potent danger to water quality

As part of MPR's “Trouble in the Water” series, MPR’s John Enger reports on the pollution issue of failing septic systems along the rocky shore of Rainy Lake.

Report is sixth in an eight-part series.

Click links below for other parts of series:

part 1:

part 2:

part 3:

part 4:

part 5:

part 7:

part 8:


2016 MBJA Eric Sevareid Award, award of merit in Series - Large Market Radio category


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SPEAKER: This week on MPR News, we're continuing our look at threats to water quality across the state. Next up, sewage. The wastewater from half a million Minnesota homes flows into buried septic tanks. These are systems that are maintained and often ignored by homeowners, not professional engineers.

The Minnesota Pollution Control Agency estimates one in every five septic systems is failing. Leaking sewage takes a heavy environmental toll. But across most of the state, it's an invisible problem. John Enger takes us to Minnesota's northern border, where the impact and cost of failing systems is front and center.

JOHN ENGER: Ken Hendrickson looks out from his lakefront home at the scenery he loves.

KEN HENDRICKSON: We're standing right in the mouth of Tilson Creek. Right over there is Bald Rock. It's called The Bald Rock Narrows.

JOHN ENGER: Hendrickson's house rests on the rocky shore of a small cove on Rainy Lake, which Minnesota shares with Canada.

KEN HENDRICKSON: Over that is the main lake. So we're kind of protected in here.

JOHN ENGER: The water Hendrickson uses to fill his toilet is pumped right from that scenic lake. And when he flushes, it goes back to the lake. On its return trip, the wastewater does make a pit stop in a small septic tank and runs through a shallow drain field. But eventually, it winds up back where it came from.

KEN HENDRICKSON: And I'm not sure if it's a good system or not.

JOHN ENGER: Septic systems aren't supposed to leak raw sewage into lakes, but in Hendrickson's neighborhood, that's what they do. The water off his piece of shoreline is laced with sewage, likely his own and that of about 200 neighbors. That's how many failing septic systems there are in a 15-mile stretch to the east of International Falls.

KEN HENDRICKSON: Nobody says too much about it, but yeah. We know it's there.

JOHN ENGER: By all accounts, the problem is bedrock that's so close to the surface. Hendrickson's basement floor isn't concrete, but clean, smooth rock.

KEN HENDRICKSON: You can see these striations? That's from the glacier.

JOHN ENGER: That bedrock is never more than a few feet below the soil on Rainy Lake. It's hard to make a septic system work in such a place. Here's the crash course on why. A septic system has two main elements. One is a big underground tank where enzymes and bacteria break down the waste. Then there's the drain field. An underground network of perforated pipe. Drain fields are supposed to be at least 3 feet above the groundwater level. Those 3 feet of dirt filter nutrients from sewage, turning it back to clean water. But dirt is scarce on Rainy Lake.

DALE OLSON: Wastewater comes out, hits the bedrock and does not get completely treated before it, then flows on to wherever it goes.

JOHN ENGER: That's Koochiching County Environmental Director Dale Olson.

DALE OLSON: Generally, eventually, it will end up in the lake. All water does.

JOHN ENGER: And there, it can do some harm.

DALE OLSON: Anywhere where you have wastewater going into a lake, you're going to get extra weed growth. You're going to get extra algae. And that can kill off certain species or make them move to different areas.

JOHN ENGER: For the last 20 years, Olson has been working to extend a sewer line from the International Falls Water Treatment Plant to those failing systems. Now, thanks to a handful of state and federal grants, he has the $17 million it'll take to bore a pipe channel through more than 15 miles of solid granite.

In a little more than a year, hundreds of faulty Rainy Lake septic systems will be harmless. But MPCA's septic supervisor Aaron Jensen says the Rainy Lake Project solves just a tiny fraction of Minnesota's septic problem. The MPCA estimates more than 100,000 septic systems are too old or so close to the water table, they're putting groundwater at risk. A quarter of those are believed to be so degraded, they pose an immediate threat to human health. But Jensen says most people never think about their septic systems.

AARON JENSEN: It's not visual. It's not like the roof of your house, you can see it's kind of out of sight, out of mind. It's something that, oh, yeah, it's kind of leaking in the bottom. But I can still flush the toilet.

JOHN ENGER: Jensen says his agency isn't planning any large scale cleanup effort. Instead, he hopes inspection and installation requirements enacted in the 1990s will continue chipping away at the problem. Before then, a homeowner could use just about anything for a septic tank. Crews replacing old systems have found everything from fuel oil tanks peppered with buckshot to old Buicks with duct tape sealing the windows. Many of those old systems have now been replaced with modern ones, but the failing systems that remain are harder to find.

PHIL VOTRUBA: Because one septic system failure is not going to trip anything probably.

JOHN ENGER: This is State Watershed Researcher Phil Votruba. He tests hundreds of lakes and rivers across North Central Minnesota for contaminants and water quality. In his last round of tests, Votruba didn't find a single lake with clear signs of septic contamination. It takes a lot of sewage to raise red flags. Even so, he says if 100,000 septic systems were leaking sewage, they're almost certainly degrading Minnesota waters.

PHIL VOTRUBA: It all contributes. Each lake and each stream has got kind of a pollution diet, so to speak. And a lake's got so much capacity to assimilate nutrients.

JOHN ENGER: No one knows just how many septic systems are failing. All told, about 2% of septic systems are inspected each year. So the MPCA's figure of 100,000 failing systems is a guesstimate at best, and it can be hard to know how sewage is affecting a lake. The MPCA routinely tests rivers and streams for sewage-related bacteria but rarely lakes, because there's so much dilution in a large body of water. The only proof of untreated sewage actually affecting Rainy Lake is a bunch of photo slides stored in a dusty old folder in the Koochiching County Courthouse.

DALE OLSON: I've done this for so long, I forget.

JOHN ENGER: When County Environmental Director Dale Olson was just starting his career, he suspected septic systems weren't working right on Rainy Lake. He didn't know the extent of the damage. So in the 1990s, he hired a pilot to fly over the South Shore and take infrared photos. And he got the proof he wanted.

DALE OLSON: In fact, you can see some of that blooming along here. Weeds and algae bloom in these little bays here.

JOHN ENGER: Dozens of old slides projected on the wall of a storage room showing off algae feasting on sewage to generate visible heat signatures. Those images set Olson to work on the sewer line project that took most of his career. Taxpayers will foot 3/4 of the $17 million bill, but Ken Hendrickson and his neighbors will also pay for sewage treatment, about $100 a month. Hendrickson says it's worth it to him to keep his lake clean.

KEN HENDRICKSON: It's a beautiful area, and we got to take care of it.

JOHN ENGER: And Hendrickson says he doesn't want his grandchildren swimming in stuff that shouldn't be there. John Enger, Minnesota Public Radio News in International Falls.


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