Hyde Pond Dam Removal

Connecticut Fund for the Environment (FE) and Save the Sound (STS), in partnership with USFWS and CTDEEP Inland Fisheries Division, secured federal funding to remove the Hyde Pond Dam, restoring Whitford Brook, the primary in-flowing stream to the Mystic River estuary, to a natural free-flowing condition. This created unobstructed fish passage from Mystic River up through the project site, and removed a threat to public safety. The existing dam was an earthen embankment with a concrete capped masonry spillway 4.8 feet high that created a 12-acre impoundment. A fishway installed at the dam by CT DEEP to support a regionally-important river herring run and sea-run brook trout fishery was known to be ineffective due to its outlet location, beaver interference, and frequent low flows due to leakage through the dam. The dam removal restored fish passage to 4.1 miles of stream and provide access for alewife, blueback herring, American eel, American shad, and sea-run brook trout.

Princeton Hydro confirmed through impoundment probing and bathymetric survey that the impoundment contained significant quantities of impounded sediments that had become densely vegetated as scrub-shrub vegetation. Sediment management and wetland impacts became driving factors in the project design and regulatory process. Princeton Hydro coordinated with CT DEEP Planning and Standards Division to develop and approve a sediment sampling plan that included multiple samples throughout the site as well as downstream and upstream.

Results indicated some elevated contaminant levels in some areas. Princeton Hydro developed a sediment management plan and construction sequence, informed by the sediment analysis that balanced active sediment management and passive river restoration. The design entailed excavation of a portion of the sediment prone to mobilization that was then replaced, stabilized, and vegetated on-site.

Princeton Hydro coordinated closely with CFE/STS to negotiate with US Army Corps of Engineers and CT DEEP regulatory divisions to minimize impacts to wetland resources as much as practicable, protect downstream water quality, restore river and riparian functions to the site, and stay within grant cost limits. RiverLogic Solutions provided construction services, and Princeton Hydro provided construction supervision to remove the dam within budget and on schedule in 2015. Since removal, the site has undergone a gradual transition in vegetation but remains a vibrant stream-floodplain wetland complex.