Wabasha officials tweak facilities as Mississippi crests
WABASHA — Dave Vosen thought he had it made this spring, that he would breeze through without a flood on the Mississippi River.
The Wabasha Public Utilities superintendent said he hates floods. High water penetrates the city's old sewage lines, sending several times more material into the sewage-treatment plant. That messes up the crawling, free-swimming or stalked ciliates that feed on the sewage and clean it. And that, in turn, messes up his love of clean water.
But Vosen's hopes for a flood-free spring were snowed under when melting snow from up north, and snowmelt from record snowfall in this region last week, sent the river to about 12 feet. That is flood stage, but it doesn't mean much to most of Wabasha because the river has to rise at least a few more feet before it begins to close roads and cause other problems.
Not at Vosen's plant, however.
Some of the city's sewage lines are up to 100 years old and are made of clay. The joints were left unsealed so ground water could seep in and flush them out. When they were installed, the city took care of its sewage by sending it right into the river, he said.
Cities began to build sewage treatment plants, but the porous lines remained. Because Wabasha is built on sandy river soil, high water penetrates through the soil and floods the lines, he said.
That's where the problems begin for his plant.
Normal flow is maybe 200,000 gallons per day, he said. Now, it's more than twice that and increasing. The plant can handle a flow of maybe 600,000 for a day but not for several days, which happens in a flood (in times of severe flooding, the flow into the plant can hit 2.5 million gallons per day).
So this year, Vosen has to bypass some of the material into the river. Fortunately, 90 percent or more of it is river water returning to the river. But there also is some sewage in it.
The choice is to swamp the plant and kill all the bugs that digest the sewage, leaving the plant out of commission for months as the bugs grow back, or bypass some of the wastewater and save the plant, Vosen said.
Vosen would have to bypass even more wastewater if the city hadn't fixed about 10,000 feet of its main lines. A company pushed flexible fabric inside the existing pipes and then heated the fabric so it hardened, sealing old joints. To really help fix the problem, each homeowner would have to spend between $5,000 and $10,000 to have that done to the lines between their homes and the mains, he said.
The heavy flow into the plant costs taxpayers money, he said. The plant has to pump more, costing about $1,000 per day for electricity, which is much more than normal, Vosen said.
For him, the problem also is personal.
"I hate bypassing, because you're putting sewage into the river," he said. "I got into this business to treat wastewater."
Unless the region gets more rain, the river is expected to begin dropping soon, and that is fine with Vosen. So far, he's been able to keep those helpful bugs working and at the right levels.
"We have happy bugs right now," he said.