Joe Knaeble’s garage in The Wedge is filled with nearly 300 pounds of rock salt. He’s collected the salt with a broom and a dustpan over the past two years, removing the excess from sidewalks and streets before it ends up in the chain of lakes.
“I try to get out in the spring, because the spring rains wash it out into the storm sewers and lakes and streams,” he said.
According to the Minnesota Pollution Control Agency, the chronic level of salt content in Minnehaha Creek is harmful to aquatic life. That threshold is 230 milligrams per liter, which equates to one teaspoon of salt in a five gallon bucket of water.
“One of the challenges with chloride is it’s an invisible pollutant. It dissolves in water, and you never see it,” said Brooke Asleson, watershed project manager for the Minnesota Pollution Control Agency (MPCA). “Concentrations could be skyrocketing and you’d never see it. It may not be a very obvious problem.”
Knaeble became interested in the issue after becoming a Master Water Steward through the Minnehaha Creek Watershed District and Freshwater Society. He’s long been eco-minded, working at the ReUse Center and founding the salvaged building material business Better Homes & Garbage.
“At Minnehaha Creek, if you’ve ever paddled it, you see all kinds of stormwater sewers emptying into the creek,” he said.
Knaeble is currently sifting all the dirt and debris out of the salt in his garage, and he’s planning to distribute it for reuse at the April 20 Lowry Hill East Neighborhood Annual Meeting as a way to educate people on the issue.
Knaeble said much of the salt seems to accumulate on the side of buildings, apparently sprayed there by automated salt spreaders. He also discovers large salt spills, one of them amounting to 42 pounds at 24th & Hennepin.
“I got there just before it rained, otherwise 42 pounds of salt would have been in Lake of the Isles,” he said.
Consequently, Knaeble wants to see change in regulations related to salt spreading. He finds much of the excess salt inside “Special Service Districts,” which are areas that collect extra taxes to pay for improved snow removal and other services.
Change has already come to the Lyn-Lake Special Service District, where contractors must clean up spills and pick up any salt accumulation at the end of the season. A targeted salt cleanup in Lyn-Lake took place about three weeks ago as part of the revised contract.
In March, seven volunteers from Whittier, Lowry Hill East and Cedar-Isles-Dean collected 67 pounds of salt and debris from Lake Street and Hennepin Avenue, much of it in the core of Uptown where a Special Service District operates.
Darren Lochner, education program manager at the Minnehaha Creek Watershed District, said chloride levels have increased in the watershed. The number of chloride-impaired water bodies more than doubled in 2015, according to the MPCA.
“Once it’s in there, for the most part it’s in there for the long term,” he said.
Asleson said sodium chloride doesn’t break down over time. She said raingardens or stormwater ponds can help remove phosphorus or sediment from water, but they aren’t an effective method to deal with salt. The only known way to treat salty water is through reverse osmosis through massive filtration plants, according to the MPCA, which is very expensive.
A 2008 University of Minnesota study found that 78 percent of chloride applied to roads was staying in the metro area, and wasn’t flushing downstream.
“Once you put deicer on the road, you have to be prepared to live with that,” Asleson said.
Asleson said it would take a huge amount of sodium chloride to become a health risk for most people to drink, but water does begin to taste salty at 250 milligrams per liter, a level that’s present in shallow groundwater throughout the state.
Chloride in Flint, Mich. water is one of the contributing factors that made the water corrosive, she said. According to a Virginia Tech research team, the Flint River holds at least time eight times more chloride than Detroit’s water, and chloride is considered very corrosive to metal plumbing. As a result, the corrosion can leach lead from plumbing materials into the water, researchers said.
“You see how corrosive it is to vehicles and infrastructure,” Asleson said.
The MPCA offers a “Smart Salting” training program designed for road salt applicators.
Knaeble said he’d like to ensure that all machine operators receive the training, rather than a single company representative. MPCA instructors teach salt applicators how to apply the right amount of deicer at the right time, in order to use less material and save time and money. Rock salt doesn’t work below 15 degrees, and other chemicals can melt ice at lower temperatures.
“There is always this dynamic or tension between safety and what’s environmentally sound,” Knaeble said. “Most people way overdo it. … If salt is used correctly you should never see it.”
Knaeble is hoping to spread the word to other neighborhoods.
“I’d really like to have all neighborhoods starting to monitor salt use with the hope that we can reduce the amount of salt being spread,” he said.
For more information about road salt and water quality, visit pca.state.mn.us.