Study of heavily salted rivers will flag chloride sources
40 monitors will remain in field for full 2 years
Kendra Carey is a “winter watchdog.” As a cold weather volunteer for the Milwaukee Riverkeeper, Carey monitors water quality in local streams even if they are ice-covered, specifically checking for chloride that flows into waterways after the spreading of salt on roads and parking lots.
Carey scooped several water samples last week from an ice-locked Cherokee Creek in Zablocki Park. It was her first visit of the season to the shallow stream in the Kinnickinnic River watershed.
The environmental advocacy group has sent out its “hardy volunteers” each winter since 2010 and they are finding steadily rising levels of chloride in most streams over that time, said Riverkeeper Cheryl Nenn.
An increasing number of samples collected during winter from the Kinnickinnic and Menomonee rivers and their tributaries contain toxic amounts that can harm and even kill fish, snails, insects and other aquatic life, Nenn said.
In response to growing public concern over such widespread contamination, the Southeastern Wisconsin Regional Planning Commission is set to begin a $1.7 million, multi-year study of the effects of chloride on the environment in the seven-county region, SEWRPC Executive Director Mike Hahn said.
Commission staff will deploy up to 40 water-quality monitors in area streams this year and those instruments will remain in place for a full two years. The monitors will continuously
Kendra Carey, a volunteer with the Milwaukee Riverkeeper, collects a water sample from Cherokee Creek in Zablocki Park as part of a road salt monitoring project. DON BEHM / MILWAUKEE JOURNAL SENTINEL
check conductivity, the ability of water to pass an electric current.
Conductivity is an indicator of the presence of road salt and other chloride products, such as fertilizers. The higher the chloride level, the easier to pass a current.
Testing by the Milwaukee Metropolitan Sewerage District shows that conductivity has worsened since 1981 at nearly every monitoring spot on the Milwaukee, Menomonee and Kinnickinnic rivers.
For the commission’s study, researchers will grab water samples to be tested for chloride from the same locations as the conductivity monitors, Hahn said.
While several past water quality studies have looked at trends in road salt contamination in a limited number of streams in the region, SEWRPC intends to fill a gap in the information by assessing chloride effects on both surface water and groundwater in all seven counties of the region.
The commission’s study will step into another uncharted territory by estimating the amount of chloride reaching water resources and pointing to where it is coming from.
“We will assess contributions from all sources of chloride to the environment,” Hahn said. When the study is completed in 2021 or 2022, SEWRPC will calculate the magnitude of each source.
The application of salt on roads, parking lots and sidewalks in winter is the most visible source and linked to abrupt increases of chlorides in rivers and creeks after snow and ice storms.
Among other sources that SEWRPC will consider: water softeners that discharge to municipal sewage treatment plants and private septic systems; road salt storage; fertilizers; food processing; landfills; and large-scale animal feedlots.
One goal of the regional study is to identify better management practices that will reduce the volume of chlorides flowing from all sources to waterways, lakes and groundwater, Hahn said. This will include a search for state-of-the-art winter road maintenance activities, he said.
Monitoring of streams in southeastern Wisconsin for the past several decades shows that chloride levels have been increasing as the number of miles of roads and acres of paved parking lots have ballooned.
One reason for that: public expectations of safe, ice-free winter road conditions have grown at the same time as the amount of pavement expanded, according to Hahn.
A study by the U.S. Geological Survey confirms a trend of streams across the northern U.S., particularly in urban areas, becoming increasingly salty from 1992 to 2012. The USGS study included locations in the Milwaukee, Menomonee, Kinnickinnic and Root rivers.
More than 25% of the water samples from the Kinnickinnic River watershed tested during that time were toxic to aquatic life.
While saltiest conditions were found in winters, the federal study found chloride levels in surface water and groundwater had increased over time in all seasons of the year in some northern cities, including Milwaukee.
Chloride concentrations will only get worse without changes in road salt applications, according to Hahn.
The four-year study will cost an estimated $1.7 million, according to Hahn. SEWRPC will spend $573,000 on the project and the state Department of Transportation has agreed to match that amount. Other funding sources and amounts include $127,000 from the Fund for Lake Michigan and $80,000 from the state Department of Natural Resources.
The regional planning commission is continuing to enlist other funding partners, Hahn said.
Milwaukee Metropolitan Sewerage District Executive Director Kevin Shafer has asked the district’s commission to approve spending $170,000 as its share of the study’s cost.
The commission will act on the request at its Jan. 22 meeting.