Effects of Highway Road Salting on the Water Quality of Selected Streams in Chittenden County, Vermont, November 2005-2007

A study of road-deicing chloride (Cl) concentrations and loads was conducted at three streams in Chittenden County, VT from November 2005 to 2007. This study was done by the U.S. Geological Survey, in cooperation with the Vermont Agency of Transportation. The streams, Alder Brook, Allen Brook, and Mill Brook, were selected to represent different land uses in the upstream watershed, different road types and densities, and different geometric patterns of the roadway draining to the receiving stream to assess the relative contribution of and differences in state road salt applications to steam Cl concentrations and loads. Water-quality samples were collected and specific conductance was measured continuously at paired stations upstream and downstream from State highways and related to Cl concentrations to assist in determining the effects of road-salting operations during winter maintenance on the levels of Cl in streams. Cl applied by the State of Vermont for deicing purposes represented less than 20 percent of the annual estimated Cl loads in all 3 streams below the state highways. None of the monitored Cl concentrations in the water-quality samples collected at the three paired sampling stations exceeded either of the US. Environmental Protection Agency’s (US EPA) recommended chronic and acute Cl toxicity criteria of 230 and 860 mg/L, respectively.