Lakeside Trail Closed As Teatown Rebuilds Dam

OSSINING, NY — At the heart of one of the region's most popular nature preserves is Teatown Lake, constructed in the early 1900s by throwing up a dam across Bailey Brook.

For the rest of November, as Teatown Lake Reservation mends the century-old dam, its most popular trail, the Lakeside Loop (a trail so busy that during the height of the coronavirus pandemic it was made one-way and masks were required), has been re-routed.

That's OK — try one of the other 13.5 miles of trails, such as Hidden Valley or Cliffdale or, if you're ambitious, the Three Lake Loop.

Officials at the 1,000-plus- acre preserve in northwestern Westchester County are repairing not only some minor cracks in the dam’s concrete but are also replacing the lower-level outlet valve.

"Due to the dam’s age, repair work is needed to ensure continued, safe operation," Director of Science and Stewardship Danielle Begley-Miller told Patch.

It's a low-level earthen dam with a front facia of concrete. Its outlet is an 11-foot spillway, which plunges into a small pool that then drains into the brook.

Fixing the outlet valve will allow staff to lower the level of the lake as needed, she said. Lake lowering would most commonly occur in the days before a predicted heavy rainfall to avoid high water levels that would risk overtopping the dam.

"These types of heavy storms are becoming more common in the area thanks to climate change," she pointed out.

The dam is also getting some added armoring to the backside and a new bridge to protect the stream during a high flow from the spillway. All repairs are deemed essential, and required, by the New York State Department of Environmental Conservation.

The lake has been lowered for the duration of work, which is likely to last through the end of November.

That part of the trail will remain closed until the work is completed, as well.

"We understand that this is an inconvenience but ask all visitors to please follow all posted signs and closures for their safety," Begley-Miller said. "We will notify members and newsletter subscribers when the work is complete."

Once the dam repair is done, the lake will naturally refill with water once the new outlet valve is closed.

"This will allow us to replace the flashboards at the dam’s spillway safely, which will raise the level of the lake above where it has been the last 2 years," she said. "The lake will refill with water slowly, over the span of several weeks unless we get heavy rain, which would accelerate this process."

Teatown Lake has been shrinking for years. If you've walked around it you know about the life spans of artificial lakes through Teatown's educational signs along the way.

"Artificial lakes have finite life spans because they are, by design, at the lowest elevation of the surrounding area," Begley-Miller said. "This means that everything drains into them, including sediments from surrounding roads and area hillsides. Over time, those sediments settle into the lake reducing its depth, especially around the lake’s edges."

The dam repair work is the first step in ensuring the safe operation of Teatown dam, but it does not address the broader issue of sediment loading, she said. "However, the Wildflower Woods Wetland Restoration Project, which was completed in July, did address some of these concerns, filtering sediments from our main parking lot and Spring Valley Road."

That will slow the rate of fill-in around Wildflower Island, and is part of a broader investment in Teatown Lake’s longevity.

There are educational signs about all of this dotting Wildflower Woods as well. Teatown has always been about environmental education as well as stewardship, the preservation of the land and trails.

In partnership with schools and universities, natural science day camps and programs for under-resourced communities, Teatown serves as a living laboratory. In 2019 the reserve opened a new Environmental Science Center to provide state-of-the-art facilities for its environmental education programs, which before the pandemic served more than 20,000 people a year.