Bypass built at Cannondale Dam to aid passing trout

WILTON: For trout approaching the small, impassible dam in Cannondale, there is a new current entering the river. Environmentalists hope it lures the trout, leading them up a bypass built last fall to enable fish to reach native spawning grounds farther upstream. "Upriver, there's a clear area with lots of gravel that's good for spawning," said Jeff Yates, a member of the Mianus chapter of Trout Unlimited.

• Three dams on the lower Norwalk River have prevented anadromous fish from reaching upstream spawning areas for years. The Flock Process Dam, just south of the Merritt Parkway, is 22 feet high. For three years, environmental groups have worked on plans to help fish get past the dams. Besides Flock Process, there are Strong Pond Dam in Merwin Meadows, a Wilton town park, and the Cannondale Dam near the Cannondale train station.
• The dam and bypass are on private property, but an easement, acquired by the Wilton Land Trust, provides public access from Pimpewaug Road near the Cannon Road bridge. The bypass is a horseshoe-shaped, manmade trench that diverts water from the river at one end, above the dam, and returns the water to the river at the other end, below the dam.
• Bypasses have been successful in the state, including at a spot on the Saugatuck River, said Chris Malik, western coastal watershed coordinator for the state Department of Environmental Protection. "It's not at all unusual to create bypass channels when feasible," Malik said. "It's less expensive and more natural, and fish are more likely to adapt to something more natural."
• Anadromous fish will not use the Cannondale Dam bypass until they can get past the first two dams on the Norwalk River. The wild trout and brook trout in the river can use it, though they won't until the fall, when they spawn. Then the engineering of the bypass, designed by Milone & MacBroom, will be tested. "It had to be steep enough to draw the fish with the strong current, but not too steep so the fish couldn't effectively use it," said Yates of Trout Unlimited. "They're trout, not salmon."
• Plans for the Flock Process and Strong Pond dams are ongoing, officials say. The plan for Strong Pond is complicated by the presence of contaminated sediment in the water behind the dam, officials said. The plan is to vacuum much of the sediment and slowly breach the dam, Yates said. But town officials are concerned about the potential to flood Merwin Meadows, a popular park and place for families to fish.
• The DEP stocks the Norwalk River with brook trout from Ridgefield to Wolfpit Road in Wilton. About 4,000 trout were put in the river this year, and 2,000 more will be added in the summer. The river is a trout management area, which means trout smaller than 9 inches must be released if caught.