One hundred and fifty years ago, Minneapolitans walked down to the shores of the Mississippi River, dipped a bucket and toted home their drinking water. Today, residents of Minneapolis, Hilltop and Columbia Heights still pull their water from the river, but it’s much cleaner than it was then.
It’s all due to far-sighted city planners who purchased land on what’s now the Fridley-Columbia Heights border and mapped out a water delivery system that operates 24/7/365 today. Laid end-to-end, Minneapolis’ 1,000 miles of water mains would stretch from here to Washington, DC.
During a recent tour of the Minneapolis Water Treatment and Distribution facility (the “Water Works”) at 4300 Marshall Street N.E., the Mississippi was a placid, lead-
colored sheet that flowed slowly past the plant and the sliver of an island that stands before it. The ice was out, and Canada geese made a racket as they chased each other around the island. Red-winged blackbirds called from a nearby marsh on the 120-acre site. Spring was in the air, but snow still covered the ground.
Inside the plant, Water Quality Manager George Kraynick enthusiastically showed visitors not only where Minneapolis and many of its neighbors get their water, but how it’s processed into a clean, refreshing drink. The free tour was sponsored by Mississippi Park Connection, the nonprofit arm of the Mississippi River National River and Recreation Area.
The tour started, naturally, at the river, where water flows through an intake tunnel that leads to pipes within the plant. The tunnel is guarded by heavy aluminum bars that keep large objects such as plastic milk jugs, trees, pieces of metal and other pollutants out. As the water enters the intake, it passes over ladder-like screens that sift out sticks, leaves and smaller contaminants.
It then flows to 63-inch-diameter cast-iron pipes that carry it to the softening plant.
Of the 960 water plants in Minnesota, only 10 percent are surface water plants; the others draw water from aquifers. Kraynick noted that surface water pulled from a river or lake is naturally softer than water that comes from an underground aquifer. That’s why many Twin Cities suburban households have installed water softeners. Folks in Minneapolis don’t need them.
At the softening plant, which went online in 1940, lime is added to the water to soften it further. “The city wanted to bring businesses into the city,” said Kraynick, “so they made the water softer.” The lime brings the water’s pH up to 11, which takes calcium and magnesium out of the water, improves its taste and makes soap lather better. (One of the “selling points” for the addition of the softening plant was that it would reduce the need for soap and save customers money on soap, which was cost-averaged at $5 per year.) Lime also disinfects the water, removing viruses and pathogens such as cryptosporidium. The plant uses 30 tons of lime per day.
Minneapolis also adds tiny amounts of powdered anthracite coal and aluminum sulfate to the water to clarify it further. “You should never smell chlorine in your tap water,” Kraynick said.
Many of the pipes that run from the street to homes are made of lead. Minneapolis puts a tiny amount of orthopolyphosphate into the water. It puts a thin coating on the insides of the pipes that prevents lead from leaching into the water supply. The coating stays on the pipes and remains separate from the water. “If Flint, Michigan, had done this,” said Kraynick, “they wouldn’t have had a lead problem.”
The water flows through the softening plant to a softening chamber full of tanks where the chemicals settle to the bottom. Drainpipes extend from the roof to the tanks. Kraynick said the city captures rainwater and adds it to the river water. “If it’s a heavy rain,” he said, “we might have to readjust the pH.”
Eight of the tanks were in operation the day of the tour; it was like being surrounded by waterfalls. It takes four hours for the water to spill over the edge of the tank into a pipe that carries it to another part of the plant, exposing the chemical sludge. When all the chemicals have sifted to the bottom of the tanks, the water flows to another series of chambers where carbon dioxide is added to lower the pH to between 8.5 and 9. It then goes to one of the Water Works’ filtration plants.
The lime/charcoal/aluminum phosphate sludge in the bottom of the tanks is cleaned out, compressed and shipped out to farmers in Minnesota and Wisconsin, who use it to adjust the soil pH in their fields. The plant generates 60 to 100 tons of calcium lime sludge daily.
Ten years ago, the City invested in ultrafiltration, which it does at its 80-million-gallon-capacity Columbia Heights plant. Water passes through a bristly membrane that strains out particles larger than .02 microns. The fibers are coming due for their first replacement.
Gravity filtration is carried out at the Fridley filtration plant, used also to process Fridley’s own water supply. The plant is undergoing renovation at this time, so the plant is running at half capacity. Kraynick noted that the renovation, which requires replacing the “guts” of the plant, avoids spending the $200 million that would be needed for a new plant. “The building is in great shape. We’re very mindful of our budget.”
The water department’s fiscal prudence extends to its maintenance activities, too. The newest building on the campus provides work space for a blacksmith and a tinsmith, who repair pumps and pipes that date back several decades.
Kraynick said the City has some concerns about contaminants leaching from the old Northern Ordnance site across Marshall Street. “The [contaminant] plume is spreading very slowly,” he said. “We have monitoring wells scattered throughout the campus. We haven’t found anything getting into the river yet.”
Asked about an upstream pollution event, he said the plant could shut down until the contaminants flowed past the plant. “We have a three-day supply of fresh water available every day,” he said.
Think about that the next time you turn on your faucet.
Minneapolis Water Works key dates
1867: Minneapolis starts a water works department, primarily for fire protection in the Mill District.
1872: First drinking water station goes online at St. Anthony Falls and Minneapolis starts pumping and delivering river water to residents. The water is untreated.
1897: First pumping station starts at 4300 Marshall St. NE. The water mains were made of wood.
1910: Minneapolis starts treating water with chlorine.
1913: Filtration plant built in Columbia Heights.
1925: Second filtration system doubles capacity.
1910 – 1941: The incidence of death caused by typhoid or cholera decreases as more cities begin treating their water supplies.
1940: Lime softening plant begins operation.
2005: Columbia Heights membrane filtration plant upgraded to ultrafiltration.
2017-18: Fridley filtration plant undergoes $60 million rehab; a new plant would cost $2 million per million gallons, or $200 million.
Below: Chemicals settle to the bottom of the softening pools. Water enters the plant in green pipes and exits in blue. (Photos by Cynthia Sowden)