Rock Salt Affecting Water Sources and Wildlife

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COLUMBIA - The harsh winter weather caused crews to spread roads and sidewalks with rock salt. New research is showing large amounts of salt on the roads may be affecting the environment.

The City of Columbia used about 4,000 tons of rock salt this winter, which is a little more than last year. Columbia Public Works Public Information Officer Steven Sapp says during winter events the city makes conscious decisions about whether to use salt to treat roads.

"Certainly we know what the consequences of using any chemical treatment on the roadways is. It's going to go into our local creeks and waterways and eventually not only here in Columbia but throughout Boone County and farther down stream," Sapp said. "And so, we do weigh that."

He also says the city is aware that rock salt is affecting wildlife in the waterways, but currently it doesn't have a good alternative to use.

"It comes down a lot to a public policy decision and right now public policy is telling us when it snows or when there's ice they want roads clear," Sapp said. "It's also a public safety issue. We need to clear the priority routes to at least get public safety through."

Dr. Jason Hubbart is a professor of hydrology and water equality in the School of Natural Resources and Director of the Water Center for the MU College of Agriculture, Food, and Natural Resources. He says experts used to think of chloride as something that would easily filter in and out of water systems quickly. However, recent studies show it can take months for chloride to wash out. This could be largely affecting biological organisms in the creek that may be living in a habitat laced with chloride. Dr. Hubbart said chloride is known to impact reproductive rates among organisms and cause additional issues.

The MU School of Natural Resources, Boone County and the City of Columbia have been working on improving policies and practices in Hinkson Creek. The MU School of Natural Resources has been working on a project in attempts to restore the creek.

In the fall of 2008, Dr. Hubbart's project obtained its first set of funding from the Missouri Department of Natural Resources. That winter, he installed a nested scale experimental watershed study design in Hinkson Creek with five permanent monitoring sites to observe climate, precipitation and stream flow around the clock.

"Those things are very important because precipitation provides the transport mechanism for pollutants," Hubbart said.

As soon as the monitoring sites were established he began looking at pollutants. The project is currently examining levels of nutrients, suspended sediments, chloride, dissolved oxygen, and temperature. The pollutant data can tell researchers a lot about an aquatic ecosystem, including its potential for providing an adequate habitat for organisms in the creek.

Research students manually collect data every other day from all five monitoring locations. "This is important because you can go out once and get a sample but that won't tell you about seasonal effects, when the chloride shows up in the water, how long it persists in the water," Hubbart said.

During the five years of research, there was a drought year and one year with excess snowfall which gave researchers a good look at what happens to the creek because one of the main places chloride in the creek comes from is road salts.

So the question is: even if the chloride isn't at toxic levels is its ongoing presence in the creek high enough to cause long-term problems?

The City of Columbia falls within 60 percent of the Hinkson Creek watershed toward the lower end. That area shows great impact from urban development, impervious surfaces and products like road salts.

"I think we can expect to see degradation continue. People often ask me ‘How can we fix Hinkson Creek?' My favorite answer is remove all the people from the watershed and never let them come back, ever," Hubbart said. "The likelihood of that is not good but that's what we would have to do to restore Hinkson Creek, really, to pre-settlement conditions."

"We all know that anything we put on to the roadways whether it's break fluid that drips out of your vehicle or oil or gas, or the cigarette butt you throw out the window, or whether it's a little bit of trash it is going untreated, untreated into our creeks and streams," Sapp said.

Dr. Hubbart hopes his data can be useful for other cities the size of Columbia in the Midwest and globally.

Visit the Hinkson Creek Watershed Restoration Projects site to learn more.