Central Wisconsin and communities along Lake Michigan’s shoreline experienced a building boom from the 1970s to 1990s. Steel septic and holding tanks, many from a now-defunct company, TMC Inc., were installed for new and replacement onsite systems. TMC offered several grades of tanks based on wall thickness. According to Chris Olson, assistant sanitarian for the Door County Sanitarian’s Department, most installers purchased the lighter, 1/8-inch-thick tanks, as they loaded easily for transport.

Within 15 to 20 years, sometimes sooner, the tar-coated tanks became pitted on the bottom and sides, and especially above the liquid level and around the riser where gases reacted with the metal. The rate of corrosion was more pronounced in sandy soils because of their iron content and the way positive and negative ions form. Top covers and baffles rusted away, and only the biomat coating the interiors prevented the tanks from caving in.

When Wisconsin’s revised sanitary code required septic tank maintenance, dozens of metal tanks collapsed after the pump-out. The failure was often catastrophic, with the top collapsing into the tank, leaving an open cylinder. Last summer, a Kangaroo Lake resident on a riding lawn mower fell into a septic tank. The back wheels of a pickup truck experienced the same fate on property elsewhere. During an inspection, an assistant sanitarian’s leg became stuck when his foot broke through the ground and the top of a tank.

In 2002, the Door County Sanitarian's Department began its Sanitary Survey, inspecting 300 or more onsite systems from top to bottom every year. Until the county began generating hard data, the state had only anecdotal evidence about onsite systems with steel tanks. In the last two to three years, the department has become aggressive about the program after seeing 80 to 90 percent of the tanks come out of the ground looking like Swiss cheese.

Olson regulates the state’s onsite wastewater program in Door County, educates homeowners, and is part of the survey team.

Pumper:

What were the results of the 2007 Sanitary Survey?

Olson:

We found that 26 percent of 373 inspected systems were failing, and 49 percent of those failures were due to bad tanks. Of the failed tanks, 96 percent were steel, and 82 percent of them were made by TMC Inc., which is out of business. About 20 percent of about 16,000 systems in Door County still have steel tanks.

The issue is gaining notoriety as people see the extent of corrosion. Articles in our local newspaper have alerted the people and they are concerned. Residents don’t want to be responsible for polluting their groundwater.

Pumper:

Don’t homeowners with leaking tanks notice ponding or other evidence of the problem?

Olson:

Most counties that are replacing these tanks have noted that they’re holding water only because a biomat forms in the soil around the leaks. According to pumpers, the tar coating and biomat holds pitted tanks together to a certain degree. The only way to see the holes is to pressure wash the tank or dig around it to look at the exterior.

Holding tanks installed in floodplains were anchored with concrete to prevent floatation. When they begin to leak, they’re full all the time. For example, a steel tank installed in 1995 was replaced in 2000 because it had to be pumped out every three days or so.

Pumper:

Are contractors still using steel tanks, and if not, what are they using as replacements?

Olson:

Very few contractors install (steel tanks) now, and those that do claim to be saving property owners money. No one in Door County installs them, so the market has corrected itself.

Septic and holding tanks must withstand harsh environments, and steel tanks should not be allowed. The problem is that state statutes prohibit counties from banning them or ordering their removal if they aren’t failing.

Installers are switching to polyethylene and fiberglass tanks when sites are inaccessible for precast concrete, and it appears that plastic will last underground provided minimal cover is maintained.

Pumper:

When leaking tanks are discovered, what does the county do about them?

Olson:

Following our investigation, we issue an order to the property owner to replace the tank or system. Door County’s policy states that most failing systems serving single-family homes must be replaced within one year. The situation may be handled differently with public facilities. If property owners meet certain financial criteria, the Wisconsin Fund Grant Program provides assistance to replace their onsite systems.

Pumper:

Besides environmental issues, are these leaking tanks causing other problems?

Olson:

Not really. Environmental issues are of great concern for our area. Door County has been called the Cape Cod of the Midwest for years, and with nearly 300 miles of shoreline, it remains a strong tourist-based economy. Good water quality is our lifeblood. As the media shows these corroded tanks, it’s easier to convince people that manufactured goods won’t last forever.

Steel tanks were installed all over Wisconsin. As their condition is evaluated, it may be necessary to raise the public’s awareness level statewide. I say “may,” because some steel tank manufacturers made a quality product.

Pumper:

What can pumpers do to diagnose these problems?

Olson:

We’re encouraging the use of high-resolution cameras to inspect the tanks. In some situations, a probe can test the steel’s integrity. When our survey team does an inspection with the homeowners standing by, the digital display from the camera is one of the best tools we have. We then show them pictures of other steel tanks of similar age, after which most agree that their corroded tank should be replaced.

If pumpers in other counties or states see tanks hanging on by a thread, regulatory bodies need to know about the situation to begin drafting a policy that looks at it. For example, most of Wisconsin isn’t looking at old systems because it doesn’t recognize that there is a problem. But this is a Catch 22, because pumpers who want to stay in business do not turn in all their bad clients. Besides anonymous tips, pumpers should provide information about these steel tanks and their limited life span to Realtors, homeowners, and plumbing contractors.

Pumper:

After an article in the Door County Advocate about your survey, did homeowners voluntarily report their steel tanks?

Olson:

We had a great response, and many property owners asked what steps to take to replace their tanks. It was reassuring to see people doing this on their own.

The article prompted the Door Property Owners Association to ask us to give a presentation about the Sanitary Survey. The association also suggested that we display a corroded steel tank at this year’s county fair, which we’ll try to do. This group and others asked that we continue publicizing the issue and educating homeowners.

Any group willing to go public about an issue carries a lot of weight, because it reinforces the elected officials’ decisions to create the Sanitary Survey and time-of-sale program, which evaluates systems before properties change ownership. Those two programs enable us to look at almost 1,000 systems a year.

Our office is talking about sending a letter to all known steel tank property owners containing the results of our Sanitary Survey and pictures of these tanks. That should stimulate a good response.

Without education, regulatory programs generate bad feelings. Even contractors, pumpers, and plumbers must believe that they’re doing the right thing. It sounds euphoric, but this industry is held together only by the people in it. If we want to accomplish something, everybody has to be in it together. We can’t afford issues that divide our industry.