As the City of Columbia advises residents to reduce their use of road salt, a research team is measuring how much gets into local waterways. Sodium chloride, the primary ingredient in road salt used for deicing, may be exceeding safe levels and causing harm to the environment.
The team of scientists from state and federal agencies comprises the Hinkson Creek Adaptive Collaborative Management, which has been studying the chloride levels in Columbia waterways.
This study, which began research in 2023, centers on a hypothesis that elevated chloride levels in the Hinkson Creek and other local streams are due to road salt use.
So far, preliminary findings seem to bolster this theory.
Joshua Horne, who works for Jefferson City-based environmental engineering firm Geosyntec Practitioners, said the research team has observed the highest levels of chloride – almost three times as high as the safe level set by the Missouri Department of Natural Resources – in downtown Columbia’s Flat Branch Creek.
“In theory, more road salt is being applied in downtown versus rural areas,” Horne said. “So we would expect a creek like that, which is right near downtown, to have the highest level of chloride because of all that extra road salt influence.”
Data was also taken from different times of year. In the summer, rainfall was shown to reduce the chloride levels in creeks and streams. However, in the winter, the research team observed that rain instead caused chloride levels to increase.
Horne and the research team attribute this to the use of road salt for deicing.
“When the rain hits all these paved areas around Columbia, it's essentially draining all of that salt into the Hanks and Creek and its tributaries,” Horne said.
Michele Woolbright Hickman, a stormwater educator for Boone County, said when excess salt travels into waterways, it harms aquatic life, plants and even the concrete and rebar used in roads.
Michael Heimos, the City of Columbia’s Environmental Education Coordinator, agreed.
“70-78% of sodium chloride applied to roads, parking lots [and] sidewalks stay within the local watershed, accumulating in groundwater, lake streams and soil,” he said.
Woolbright Hickman said these effects can be mitigated through the reduction of salt use.
“The easiest way to prevent salt from getting into our waterways is actually just the reduction of it being used in general,” Woolbright Hickman said. “It is actually extremely difficult to remove chloride once it has entered the environment.”
Heimos also advises residents to be mindful of their road salt usage this winter.
“When we put salt out on the roadways, we have to be conscious of what we put into our watersheds,” Heimos said. “This is where our water comes from. These are our water resources for our water here in Columbia, so it's important to protect that.”
Heimos said the City of Columbia Public Works Department is also taking measures to reduce road salt usage through using pre-treatment and wetting to make the salt more effective, as well as through using machinery that calibrates how much salt is being distributed.
Finalized results of the Hinkson Creek CAM research study are expected to be released later this year.
