Chlorides and Winter Management
In 2004 chloride Total Maximum Daily Loads (TMDLs, a pollutant budget for a waterway) were placed on several segments of the West Branch DuPage River, East Branch DuPage River and Salt Creek. The TMDLs were triggered by exceedences of the State Water Quality Standard (currently at 500 mg/l). The exceedences occurred during the winter months, a finding confirmed by subsequent monitoring conducted by the DRSCW.
Chlorides and Winter Management Resources
Project Introduction
Welcome to the DRSCW Chlorides and Winter Management page. In 2004 chloride Total Maximum Daily Loads (TMDLs, a pollutant budget for a waterway) were placed on several segments of the West Branch DuPage River, East Branch DuPage River and Salt Creek. These TMDLs were triggered by exceedences of the State Water Quality Standard (currently at 500 mg/l). The exceedences occurred during the winter months, a finding confirmed by subsequent monitoring conducted by the DRSCW. Winter snow and ice control, which relies heavily on compounds of chloride such as rock salt, magnesium chloride and calcium chloride, was clearly the source of the exceedences. Area POTWs also release substantial amounts of chlorides (averaging 142 mg/l based on a summer survey of the West Branch POTWs) but are not the principle drivers of the water quality exceedences. The DRSCW’s original evaluation of area chlorides and how to meet the goals of the TMDL can be found here.
When salt dissolves in water it is, for practical purposes, impossible to remove. Once chlorides are in solution, they do not break down or go away, making them one of our most persistent pollutants. However, chlorides are very effective freeze-point depressants; the most commonly used products that melt ice and snow contain chlorides in various concentrations. We have provided resources below, grouped by category, to assist you find information relevant to your operations. If you do not find the information for which you are searching or have suggestions, please let us know at info@drscw.org.
High concentrations of chlorides in streams is toxic and kills biological organisms. The USEPA’s National Aquatic Life Criteria for chloride recommends 230 mg/l as a chronic threshold and 860 mg/l as a toxic threshold. Research by the DRSCW shows that chloride is a proximate stressor in the Upper DuPage and Salt Creek river systems. This means that it was one of the variables that best correlates with biodiversity of fish and macroinvertebrates. A report prepared for the Minnesota Pollution Control Agency by Fortin Consulting, Inc., found that the savings made by reducing one ton of salt from winter operations were as high as $3341 (Source: “The Real Cost of Road Salt Use for Winter Maintenance in the Twin Cities Metropolitan Area of Minnesota” January 21, 2013).
Education Materials
Education Materials
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