Ten years ago, Watershed Management Division (WSMD) scientists completed a study of Ticklenaked Pond, in Ryegate, VT, to determine sources of excess phosphorus, and identify options to reduce loading of this nutrient to the lake, which was resulting in excessive algae blooms. That study indicated the need to address watershed-based phosphorus sources, but also to interrupt the annual summertime release of stored-up phosphorus from bottom sediments. Alum is a chemical commonly used to treat drinking water that can “bind” sediment phosphorus, and keep it from releasing when conditions would otherwise promote that release. WSMD wrote a TMDL (total maximum daily load) pollution control plan to clean up the lake, which was approved by the US Environmental Protection Agency (USEPA).
Over the last 10 years the Ticklenaked Pond Association has worked with camp owners around the lake on all of the watershed sources. They planted buffers, addressed driveway erosion and stormwater runoff, and worked with the town to address town road erosion issues and enforce strict lakeshore zoning regulations. The Department of Environmental Conservation, Vermont Agency of Agricultural Foods and Markets and US Natural Resources Conservation Service also worked with farmers in the watershed to address agricultural sources of phosphorus in the watershed. Bit by bit, the partners working in the watershed “checked off” source after source from the list generated by the lake’s TMDL remediation plan.
Over the past year, the Town of Ryegate and Ticklenaked Pond Association worked with consultant DEC and Aquatic Control Technologies to design and successfully complete an Alum Treatment of Ticklenaked Pond, which occurred May 16th through May 22nd. The alum treatment was the last remaining cleanup action, which was funded through a $95,990 Ecosystem Restoration grant to the Town of Ryegate.
The treatment of the lake was made challenging due to an algae bloom taking place at the start of the treatment. That required careful monitoring to ensure that levels of alum did not create toxic conditions for fish and other aquatic life. The total treatment consisted of 20,000 gallons of aluminum sulfate, and 3,000 gallons of sodium aluminate. These doses were injected over the four-day treatment period in accordance with specifications that were developed by expert lake scientist Ken Wagner of Water Resources Services, Inc. Ken’s work was also funded by a prior Ecosystem Restoration Grant.
At the end of the treatment the lake had already begun the process of clearing up. The water transparency, which was less than six feet, increased to over 10 feet in just a few days – nearly doubling transparency! This was also noticed by a local fisherman who commented that the pond “looks cleaner than it has in a long time.” Treatments with alum are rare in Vermont. Only a very few lakes are suitable candidates for this approach to controlling phosphorus. Determining the suitability of an alum treatment requires considerable study. The last alum treatment executed in Vermont took place at Lake Morey in 1986, and the results of that restoration are still in place today. The Ticklenaked Pond Association, Town of Ryegate and local farmers will continue to keep phosphorus loading levels down, so that new phosphorus does not accumulate on the ponds bottom and allow the sediment phosphorus release to begin once again. The Watershed Management Division, along with the Town and Lake Association, are optimistic for many years of effectiveness of this treatment.