Minnesota winters confound mound septics

IMAGE: Custom Septic

Just a couple weeks ago it was thirty below zero. Now teenagers are wearing shorts and the dirt roads are breaking up. I saw forecasted highs in the 60s coming down the pike. That’s how fast the weather turns in Northern Minnesota.

A few weeks ago I warned about the possibility of frozen septic mounds this year due to the deep penetrating frost and lack of insulating snow cover. Well, with a few exceptions I’ve heard about, the major regional septic freeze didn’t happen. Now, with overnight lows near or above freezing, it won’t. We dodged a nasty, stinky bullet.

But last week veteran Iron Range septic installer and op-ed commentator Joseph Legueri contacted me with some independent research he had conducted on septic mounds over by Palo. Yes, these are the kinds of e-mails I get. Yes, I do answer them.

In essence, Legueri explains how the fact that septic mounds in Northern Minnesota typically spend half the year very near or even below freezing essentially depletes them of their sterilizing, detoxifying abilities for those months.

Legueri writes:

The mounds we use up here were developed in Madison, Wisconsin, which is over 400 miles south of Ely. Thus they are called “Wisconsin Pressure Dosed Mounds.” Although the mounds were tested extensively in Madison, the Minnesota Pollution Control Agency (MPCA) mandated their use in far Northern Minnesota without constructing a mound up here and testing it before they mandated it.

That’s a problem. Legueri found that for six months out of the year, mound septics don’t do anything. The waste does not break down; it waits for spring. And when spring arrives (like it will this month or next) the sudden warming of the dormant bacteria and toxins prove too much for the system, and bad stuff likely escapes into the groundwater.

Essentially, Legueri argues, the septic mounds mandated on so many rural Minnesota residential properties aren’t the most environmentally responsible option after all.

Is there more? Yes, so if you want to know how Legueri reached this conclusion, see the following. If not, you are a champ for reading this far on a beautiful day (in which metastasizing toxins are bubbling beneath the earth).

Here’s what Legueri did (the chart he references is found here):

In September of 2012, I asked six rural Palo, MN, homeowners with pressurized, mound-type septic systems if I could stick three soil thermometers into their mound. A soil thermometer is like a meat thermometer, only it has a three foot long stem; and a mound-type drain field sticks up four feet above the surface of the ground. Because I worked for a licensed septic system installer since the seventies, I was present as a laborer at the installation of dozens of mounds, so I knew exactly where to place the thermometers. We placed one thermometer where the wastewater entered the mound, one in the middle of the mound, and one at the end of the mound. The homeowners were kind enough to read the thermometers once per week (on Saturday) and report their readings to me. I kept track of those weekly readings until June of 2013.

You will see “In,” “Middle,” and “End” at the top of the chart’s columns. The word “Control” heads the fourth column. I placed a soil thermometer at the far end of my own underground, gravity-flow septic system. I read the thermometer each week and listed the readings under the “Control” Column. Please also note the average monthly temperatures and the snowfall figures listed at the right of the temperature chart.

Knowing that our refrigerators are factory-set at 40 degrees to reduce bacterial action, and knowing that septic systems use bacterial action to treat sewage, I sent the Mound Temperature Chart to more than a dozen bacteriologists, engineers, and biologists. Following are three of their comments about what happens when the mounds try to treat sewage at such low temperatures for six months:

Dr. Brian Lanoil, University of Alberta (Edmonton)-“When (mound) temperatures drop, biochemical reaction rates drop as well. So the treatment of wastewater will slow down at lower temperatures. Furthermore, pathogens (poisonous materials) such as viruses and bacterial pathogens will be preserved by the cold, making the end product more dangerous.”

Dr. Scott Meschke, University of Washington (Seattle)- “In general, as temps in the mound system approach freezing, the biological activity in the mound will slow reducing the degree of biological stabilization and pathogen reduction. Pathogen survival will likely be enhanced by colder temps (particularly for viruses; some bacteria and Protozoa may be slightly reduced by freeze-thaw damage if temps actually reach freezing).

Craig Mains, Engineer, National Environmental Services Center, West Virginia University (Morgantown)- “The worst case scenario would seem to me to be that in extremely cold weather there is little or no treatment taking place in the mound itself and treatment is taking place in the native soil underneath the mound…You might make the case that in those circumstances the mound is providing no better treatment than a conventional, in-ground drainfield…”

I could quote many more scientists and engineers, but all whom I have contacted say that at these temperatures, for six months out of the year, our northern mounds are manufacturing pathogens and putting them either into the soil or into the water table.

Legueri’s data and notes may be found here.