Take a walk along the Mississippi River in Minneapolis with Steve Lee, and you'll hear the word "poop" a lot.
That's because it used to be a huge problem for the Twin Cities, said Lee, a history buff and retired pollution regulator with the Minnesota Pollution Control Agency.
He led a history tour along the river's Minneapolis banks, and took the opportunity to talk about the variety of things we used to dump in the water. But he made clear that although we have stricter rules about everything from sewage to sawdust, the Mississippi today still faces plenty of threats.
"The pollution problems have changed dramatically," he said. "They've gotten harder. They've gotten more expensive."
Here's a look at the pollution that used to be a big problem for the Mississippi — and how today's concerns compare.
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Then: One of the reasons people would settle near rivers was to have a way to dispose of waste, including human waste, Lee said. In the early days of the Twin Cities, raw sewage went straight into the river.
"It worked kind of OK," he said, "because every spring the big toilet would flush: The snow would melt up north, the rains would come. All that water would come down and flush that sewage and stink downriver to wherever it goes, to the land of 'away.'"
But then dams were built and significantly slowed the river's flow. By the 1920s, Lee said, the river in the Twin Cities was like a series of bathtubs, with up to 15 feet of sewage sludge backed up above the Ford Dam, Lock & Dam No. 1. At that point, he said, the only thing living in the river was sewer worms: organisms that can tolerate low oxygen levels, so they can live in dirty water when other aquatic organisms can't..
Now: Twin Cities residents now flush all their dirty water to the Metropolitan Wastewater Treatment Plant in St. Paul. It's treated before being released back into the river. But there are still pollutants that get through, including phosphorus, a nutrient that can cause harmful algae blooms; pharmaceuticals like codeine and other chemicals like BPA, a plasticizer, that treatment processes haven't been able to remove.
Some of the chemicals that remain in the water mimic hormones and affect aquatic life by disrupting organisms' endocrine systems. Scientists are now working to explore the implications.
"There's a lot of fish in there," Lee said. "The problem is [that] more of those fish than you'd expect are lady fish."
He added: "That's a terrifying thing to me."
Then: The early forestry industry sent logs down the Mississippi to sawmills in Minneapolis, where they would be turned into lumber. The sawmills dumped the waste from all that lumber — sawdust — in the river, Lee said.
"There were vast sawdust banks by the river in St. Paul, and the steamboats couldn't get to the landing," Lee said.
Congress passed a law in the 1880s against dumping waste that might impede navigation into rivers.
Now: Sawdust isn't a problem any more, but sediment is.
Soil running off of river banks and farm fields ends up in the Mississippi, and the U.S. Army Corps of Engineers dredges the river to keep navigation open. Just last week, the Upper Mississippi River Basin Association, which includes Minnesota and four other states, announced an agreement with the Army Corps on a planning project to deal with floods, droughts and sedimentation.
Then: Two Mississippi River oil spills — one in 1962 and another in 1963 — changed the course of environmental regulation in Minnesota, and Lee has researched them extensively.
In December 1962, a burst pipe at Richards Oil in Savage spilled a million gallons of oil into the Minnesota River.
In January 1963, a facility in Mankato spilled 3.5 million gallons of soybean oil, which made it into the Minnesota and later the Mississippi.
Two months later, George Serbesku, a weigher at a St. Paul stockyard, found dead, oily ducks south of the city. He was so mad about it that he delivered two bushel baskets of the dead ducks to the State Capitol rotunda, Lee said. Even the governor helped with a duck cleanup effort in Serbesku's basement, and the Legislature passed a law to require dikes around storage tanks to catch leaks.
Now: Oil leaking from tanks isn't nearly as big a concern as it used to be, but we still have plenty of oil moving near rivers in pipelines and on trains.
Experts have said the aging Enbridge Line 3 pipeline is vulnerable, and construction on a replacement line is expected next year. Unlike in the 1960s, Lee said, companies that spill oil nowadays are obligated to clean it up — and have to have strong spill-response plans in place.
4) Blood and guts
Then: Slaughterhouses used to put all of their waste in the river. Lee said he remembers a time early in his career when a turkey plant was putting turkey heads down the storm sewer.
That's now illegal, and the turkey heads are sent to landfills instead.
Now: Slaughterhouses aren't a big worry here anymore, but manure from livestock feeding operations is.
In southeastern Minnesota, for example, local residents are worried about a proposed hog farm that they say could contaminate water supplies in the region's fragile karst geology. The Minnesota Pollution Control Agency is reviewing the proposal.
5) Industrial waste
Then: Minneapolis had a coal gasification plant that produced oil for streetlights, Lee said. Where did the waste go? "The leftover stuff, they'd chuck in the river. It was full of arsenic and other things," he said. Not even the sewer worms could survive in the contaminated river near the plant, Lee said.
Now: Industrial chemicals are heavily regulated, but the Mississippi is still polluted. While plenty of fish live in the river, they are contaminated with mercury, PCBs and other chemicals, prompting the Minnesota Department of Health to recommend people limit their consumption. Fluorinated chemicals once manufactured by 3M to make non-stick and stain-resistant materials are also in the river and have been detected in humans and animals' bloodstreams, Lee said.
"Those miracle fluorinated chemicals that do so much for us have spread around the world," he said. "Nobody knows for sure if that's of health consequence or not. ... That's one of the problems with pollution now: Who is going to set the standard on these very small potentially toxic or maybe not toxic things?"