Saving Mamanasco Lake: Improvement Plan Includes Projects To Quell Erosion, Will Depend On Town Funding

The ruins of an old mill lie just below the dam at Mamanasco Lake. Native Americans once gathered nearby in what is now Richardson Park. Historical homes dot its shores.

Mamanasco Lake has a lot of stories to tell, but the one that truly lives on is told by the Ridgefield residents who to this day swim there, canoe there, fish there and live there.

And the Mamanasco Lake Improvement Fund hopes to allow that history to continue and keep the lake healthy enough for the residents of Ridgefield to enjoy.

“There’s a lot of history at this lake,” said MLIF board member Kitty Fischer as she stood by the shore Wednesday afternoon. “The way we feel at the Improvement Fund is that we’re protecting this lake for the town.”

For several years now, the MLIF has collected private donations as well as funds from the town that it contributes to projects preventing the environmental degradation of the lake. The funds for these projects recently approved by the Board of Finance and to be decided by town voters in the capital budget amount to $35 thousand for 2011-12.

Mamanasco Lake’s actual ownership is uncertain, but the town owns the largest amount of shoreline – other parts of it belong to private homeowners, a point of contention that had the finance board voting 3-2 to approve the funds.

The 96-acre lake collects water from over 530 acres of developed and wooded land, a watershed that extends mostly to the southwest of the lake across Mamanasco Rd. and Old Sib Rd.

And one of the biggest issues with this watershed is that, as water flows quickly downhill, it takes with it large amounts of sediment and nutrients that end up in the lake.

This can pose a problem. Parts of the lake look very different than they did even a couple years ago.

“If we didn’t do the kinds of things we’re doing, this lake would become a marsh,” said environmental engineer Tessa Jucaite, also with the MLIF board. Deltas have formed along Mamanasco Rd., and the land continues to encroach onto lake waters.

In addition to large catch basins emptied of sediment once or twice a year by the Highway Department, two major projects are planned to improve storm water drainage.

The first includes large “scour holes” at five different outfalls on the southwest side of the lake – these are intended to slow the water velocity as it flows into the lake, thus allowing for less erosion of sediment.

Farther uphill, the MLIF, with help from the Highway Department, plans to create riprap inlets also for the purpose of slowing the water down. By doing this and by increasing the vegetation in the areas of fast-moving water, Jucaite said, major sedimentation of the lake can be remedied.

“We’re doing the things we can do to help,” Jucaite said. “This is pretty much the minimum we can do.”

If sedimentation reaches a certain level, one of the only options that would remain would be to dredge the whole lakebed, a project that can cost as much as one million dollars – the smaller projects, though not perfect, are the least intrusive and costly, Jucaite said.

Another issue is nutrification, or the introduction of too many nutrients from the surrounding area. This can lead to large amounts of algae in the water that, in some years, has prevented use of the lake.

An influx of phosphorous, for instance, in some cases a derivative of fertilizers, is a main concern, Jucaite said, and the lake must be treated with chemicals such as allum to break down the resulting algae, which in turn also contributes to more sedimentation.

Another battle the MLIF is fighting is that against the invasive species Eurasian watermilfoil, a plant that is very difficult to control once it’s established in a body of water.

The MLIF focuses on education, as well, especially for residents within the watershed whose practices on their own properties affect what happens to the lake.

“This is a town resource, a beautiful town resource, and it’s used by the people of the town, not just by the people around the lake,” Fischer said. “And we want to maintain it for perpetuity – it’s a wonderful resource.”