Filamentous Algae Problem on Amston Lake

The problem: if you were to canoe around the perimeter of Amston Lake, you would find a very heavy infestation of filamentous algae near the intersection of Deepwood Drive and St. Ronan Road on the Hebron side. The algae is the result of excessive nutrients (especially phosphorous) entering the lake through runoff. Algae growth is especially prevalent near the storm drain outlet into the lake at 193 Deepwood Drive. The outlet pipe is at the center of the picture (but not visible). The algae grows on the lake bottom, eventually releasing enough oxygen to force it to the surface, where it floats downwind. Amston Lake is especially conducive to algae growth, being a shallow lake that allows sunlight to reach the lake bottom. This problem has been getting worse and worse over the past ten years.

The cause: The problem stems from the hill to the west of the lake, with steep streets such as Bass Lake Road and St. Ronan Road feeding storm runoff into antiquated storm drains and then into the lake. In the two pictures of Bass Lake Road, you can see a slight right-to-left slope and no curbs, allowing runoff to erode the south edge of the road. You can also see sand buildup from winter snow removal along the left edge of the street.

The storm drain itself is not recessed in the street, so some water just keeps flowing across Deepwood Drive and across the inadequate curbs and on into the lake.

To the left of the road, water flows down a stream from uphill wetlands and into a very small retention pond next to Bass Lake Road.  This retention area accumulates muck with phosphorous readings off the chart. The town of Hebron cleaned it in 2004, but it clearly needs cleaning again since it doesn’t impede storm water flow. Some material may also be seeping through the stone side from Bass Lake Road.

What happens to the people with shorefront property? The algae winds up on their beaches! This picture shows algae buildup near the storm drain outlet.

If you want to remove the algae from your beach, it requires at least raking the “pond scum” from the surface and drying it on shore. You can use it as garden fertilizer or mulch or haul it to the dump.

If you are really determined, you can don water goggles and remove the algae from the bottom.

Removing the algae manually is environmentally sound, since the algae would otherwise decompose and remove oxygen from the lake.

What else can be done? The nutrient-rich lake bottom near the storm drain outlet could be dredged. Reggie Miles mentioned possible discussions with the town of Hebron. Barley hay has been used  on ponds and other lakes.

On July 13, 2005 the Hartford Courant published an article concerning the Amston Lake algae problem that will be available on-line for a short time.