Rotten Eggs – Why Some Door County Water Stinks

Illustration by Ryan Miller.

Most of us take our tap water for granted. We open the tap and out comes clean, odorless water. But in certain parts around the county the odorless part is no sure thing, particularly in Ephraim.

“We’ve had customers come in and ask if our water smells like the water at their hotel,” said Chef’s Hat owner Todd Bennett. “Fortunately we’ve never had a problem with our water, but there are others in Ephraim where it will have a strong odor to it.”

Those not so fortunate homes and businesses will have water that smells like rotten eggs, sometimes particularly strong. But the water remains perfectly safe to drink. That’s because the smell comes from sulfur deep below the soil.

Roger Kuhns, a geologist who has extensively studied Door County for years, explained the source.

Roger Kuhns

“Down below the soil, in the dolomite, there’s iron sulfide, which has a brassy, yellow color,” he said. “It’s very common, and when oxidized this is what creates rust. And when it does, it releases iron and sulfur into the water.

“You also have a dozen common bacteria in ground and surface water that will eat through metal and iron. Some of these bacteria, called sulfur-reducing bacteria, release sulfur as a waste gas as they break down metals. When you get a lot of that, you get sulfur dioxide, and that has an odor to it.

“Then you have hydrogen sulfide, now that really stinks.”

Click the image to see all of our 2016 Sustainability Issue articles. Illustration by Ryan Miller.

These are often entirely natural, stemming from natural sulfur in the rocks deep in the ground, though hydrogen sulfide can also come from agricultural waste, stormwater runoff or leaky septic systems.

Up the road from Chef’s Hat, Paul Wanish at Czarnuszka Soup Bar says he only notices a smell when he turns on the water after being closed a few days. “After I run it awhile, it goes away. I’ve never had a customer mention a smell before.”

What Wanish experiences is not uncommon. The rotten egg odor associated with hydrogen sulfide is often stronger when water is initially turned on, or when running hot water, which forces the gas into the air.

All that is to say that the rotten egg smell is caused by sulfur in the ground and is usually not something to be worried about, except that it smells bad. But how come one home has perfectly normal water, and the water next door smells like a fart?

“You can have more sulfur in certain layers of rock than in others,” Kuhns said, “so the depth of your well can dramatically impact the smell or quality of your water. That’s why neighbors in a place like Ephraim can have dramatically different water makeup.”

Door County’s karst topography, the leaky Swiss cheese-like rock that we stand on and draw our drinking water from, doesn’t help either, as water can travel great distances through many types of rock before getting to the table where your well draws it to your tap.

“You can get that smell out with a good charcoal filtration system,” Kuhns said. “But even if you have that, you may still get the smell after a big rain event, especially if you’re near a farm.”