Dramatic and rising concentrations of Chloride from road salt have been identified in New Hampshire waters and mirror a trend that is being seen by other states in the US and Canada due to the application of de-icing chemicals. In 2008 New Hampshire listed 19 chloride impaired water bodies on the 303(d) list under the Clean Water Act. In 2010 that number increased to 40. Chloride can lead to a reduction in the diversity of aquatic species, a decrease in dissolved oxygen and an increased nutrient loading which promotes eutrophication in lakes.
At this time, the only way to prevent chloride from reaching surface and ground water is to reduce the amount applied to our roadways and parking lots without compromising safety. When road salt dissolves in water, the chloride molecule is not retained by the soil and easily moves with water flow. Chloride is not significantly removed by chemical reactions or evaporation. Therefore, nearly all of the chloride applied to the land surface as road salt will eventually end up in the nearby surface waters or groundwater.
Following the listing of Chloride Impaired Waterbodies along the I-93 Corridor in Southern New Hampshire, NH DES, NH Department of Transportation (DOT), and several municipalities and private contractors are working together to reduce chloride while continuing to provide safe passage for traffic and pedestrians.