LOCALadk Magazine

24 Winter 2018 LOCALadk Magazine LOCALadk The stor y of how road salt runoff is impacting Mirror Lake doesn't end there. As the salt-laden water flows into Mir- ror Lake it hugs the lake bottom because the additional salt makes it denser than the water in the lake. Throughout the winter, this water builds up at the bottom of the lake, and by the end of the winter, the water at the bottom of the lake often exceeds 100 mg/L of chloride, while at the surface the concentration is less than half that. The density difference from salt buildup at the bottom of the lake increases the energy required to mix the water column. Think of the Italian salad dressing sitting in your fridge, and the amount of energy (shaking) you have to put into the bottle before pouring it on your salad. The physics of what is happening in Mirror Lake are the same. Research by AsR A and AWI has linked the buildup of sodium and chloride at the lake bottom, and the result- ing increased energy required to mix the lake, with a lack of mixing in the spring. When the lake should turnover, it does not. Lake mixing is a fundamental physical process that drives much of the chemistr y and biology of our lakes. Most lakes of sufficient depth to thermally stratif y in the summer turnover twice a year in our part of the world. Road salt is interrupting this process in Mirror Lake. As a result of the reduced mixing, the water at the bot- tom of Mirror Lake lacks oxygen. This causes a shift in the chemistr y of the water, most notably a release of phospho- rus from the sediments. This makes Mirror Lake more vulner- able to algal blooms and reductions in water clarity. The lack of oxygen also puts a pinch on the lake trout found in Mirror Lake. Low oxygen at the bottom and warm temperatures at the surface squeeze these fish into an increasingly narrow band of water as the summer progresses. If the lake contin- ues down this path, it may lose this iconic Adirondack fish. The stor y of the environmental impact of road salt doesn't end there, and unfortunately hits a little closer to home. AsR A and AWI have long suspected widespread groundwater contamination after obser ving elevated chloride concentra- tions in Adirondack streams throughout the summer and fall, months after the last application of road salt. AWI recently released the results of a groundwater study conducted park- wide. They sampled 358 wells throughout the Adirondack Park; roughly one-third receive no road runoff, one-third re- ceive runoff from local roads, and one-third receive runoff from state roads. They found that 55% of wells receiving run- off from state roads exceeded the drinking water guidance value for sodium, compared to 10% receiving runoff from lo- cal roads, and zero wells receiving no road runoff exceeded this value. In the Adirondack Park, many homes are on private wells, which are unregulated, and for which the responsibility falls on the homeowner. When regional contamination of the wa- ter people rely on to drink occurs, it puts a significant burden on these rural communities. It may mean investments in ex-

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