Determine Dilution Factors for Snow and Ice Control Materials

Focus Area

Water Quality/Wetlands


Natural Resources






1-2 years

Research Idea Scope

Issue: Tests have shown that aquatic organisms have different tolerance thresholds to snow and ice control materials that are applied to roads, highways, and bridges. A major factor in terms of selecting appropriate deicers and material application and purchase amounts is the expected dilution concentrations after application that can potentially be discharged to receiving waters via runoff. The generally accepted dilution factor is 500 to 1 at the margin of a roadway. Recent tests, however, indicate that a 500 to 1 dilution is not sufficient to prevent chronic effects on Selenastrum and Ceriodaphnia from most commonly used deicers. Some of the deicers also caused acute effects to the test organisms. Although dilution will increase as the runoff moves from the roadway margins to the receiving waters, the commonly used rule of thumb 500 to 1 dilution factor, may not adequately protect aquatic biota.
Research Objectives: Test for deicer concentrations at roadway margins to determine whether a 500 to 1 is a typical concentration at the roadway margins. Determine appropriate methods to test, analyze and calculate application rates for commonly used deicing materials that will be protective of aquatic biota. Provide guidance on methods to select and apply appropriate deicing materials to meet aquatic biota protection goals and objectives based on dilution factors including proximity to receiving water bodies and other factors that will influence influent concentrations.
Specific Tasks: A literature review which includes a survey of State DOTs and their studies and research on dilution factors. Provide studies of various materials (liquid and solid) using tracers or other tracking methods to determine dilutions of applied materials at roadway margins.

TERI Administrator Note (May 2007): Related Research
NCHRP Report 577,
Guidelines for the Selection of Snow and Ice Control Materials to Mitigate Environmental Impacts (May 2007)

Abstract: TRB’s National Cooperative Highway Research Program (NCHRP) Report 577: Guidelines for the Selection of Snow and Ice Control Materials to Mitigate Environmental Impacts (published May 2007) explores guidelines for the selection of snow and ice control materials through an evaluation of their cost, performance, and impacts on the environment and infrastructure.  The report examines a decision tool for the selection of snow and ice control materials to suit the specific needs of any given highway agency, a purchase specification that can be used by an agency once agency staff have selected materials for use, and a quality assurance monitoring program that includes procedures and standard test methods to characterize snow and ice control products before their purchase or use.

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