Monitoring Finds Highest Ever Levels Of Road Salt Deposition In Mirror Lake

Apr 17, 2019

The latest report assessing the health of Mirror Lake in the Adirondacks finds it continues to be negatively affected by road salt.

The Ausable River Association conducts biweekly chemical monitoring of the health of the Ausable River watershed, testing for contaminants.  In 2015, they focused on Mirror Lake after detecting elevated levels of chloride traced to road salt.  An annual Mirror Lake Water Quality Report has since been released.   In 2017 the report found that the lake experienced diminished spring mixing, which is when thermal stratification between its warm and cold waters occurs.  Report author and Ausable River Association Science and Stewardship Director Brendan Wiltse wrote that even with efforts to reduce road salt, the 2018 report found the highest ever concentrations of chloride in the lake.  “When that salt is applied it does its job of melting snow and ice, goes through its stormwater system, makes it to the lake. That water at times has ten-thousand times the concentration of salt that we would expect to find in a stream in the Adirondacks. And all that additional salt makes that water more dense than the water that’s in the lake.  So when it enters the lake it flows along the lake bottom and accumulates at the deepest part of the lake.  As that happens all winter long you end up with this more salty dense layer in the bottom half of the lake and less dense water above it. And that is what’s preventing the lake from mixing.”

Wiltse adds that Mirror Lake’s inability to complete its natural cycle prevents redistribution of oxygen and nutrients throughout its waters.  “Because Mirror Lake isn’t doing that the bottom half of the lake has very low oxygen right through the whole entire summer.  That releases phosphorous from the sediments within the lake and that in combination with the elevated salt concentrations all make the lake more vulnerable to things like harmful algal blooms and perhaps fish kills and other things that we really don’t want to see happen in the lake.”  

Mirror Lake a centerpiece of Lake Placid’s recreation and tourism.  About 250 businesses, residents and visitors have signed a letter and petition to village and town officials seeking alternatives, and to obtain Sustainable Winter Management certification. Ausable River Association Executive Director Kelley Tucker says they don’t want salt damage to become a real or visible reality.  “This year I think especially with the business owners in the Lake Placid region they were like you know there’s too much at stake. The lake is the centerpiece of our economy and they began to understand that lakes turn over twice a year. It’s like breathing for a lake and Mirror Lake has lost that opportunity to breathe in many springs now. And we don’t want to see this happen but worst case scenario is if it doesn’t turn over in fall that’s when we can have impacts that would be visually unappealing and would affect the quality of the water. So these businesses are like it’s time to act now and we see a way forward. We don’t think it’s too late to find solutions and correct this.”