Case Study: SuAsCo Watershed Fish Restoration

SuAsCo Watershed Diadromous Fish Restoration Feasibility Study & Conceptual Design

MA Div. of Marine Fisheries (Billerica, MA)


Gomez and Sullivan conducted a feasibility study to restore diadromous fish to the Concord, Sudbury, and Assabet Rivers (known as the SuAsCo Watershed) in Massachusetts. Project partners included the MA Div. of Marine Fisheries, NOAA Restoration Center, US Fish and Wildlife Service, and MA Dept. of Environmental Protection. The scope of the project focused on the primary impediment to fish passage—Talbot Mills Dam in Billerica, MA—but several downstream sites that may present issues for fish passage were also evaluated, including Middlesex Falls (a natural bedrock falls and remnants of a breached dam) and Centennial Falls Dam (an active hydropower dam equipped with a fish ladder of unknown effectiveness). The entire river was also assessed for potential water depth and/or velocity barriers to fish passage. Species targeted for restoration included river herring (both blueback herring and alewife), American shad, American eel, and sea lamprey. Services included an existing information report, topographic survey, sediment depth mapping and core sampling, a sediment management plan, hydrologic and hydraulic analyses, structural assessment, management of a cultural resources analysis, conceptual designs and cost estimates for fish passage options, a feasibility report, and public meetings. Alternatives considered for Talbot Mills Dam included dam removal or a Denil fish ladder with an eel ramp and downstream passage notch. Providing fish passage at the Talbot Mills Dam would restore access to over 35 miles of diadromous fish habitat on the mainstem rivers, plus more than 100 miles of tributary habitat and at least 260 acres of lacustrine habitat (not including areas that could be accessed with fish passage at additional upstream dams).