Watershed Management Bureau

  Coastal Program

    Restoration - Winnicut River Dam Removal Feasibility

• Feasibility Study (PDF - 7.5 Mb)

• Appendix 1 - Area Form (PDF - 6.5 Mb)
• Appendix 2 - Title Summary and Data (PDF - 7.6 Mb)
• Appendix 3 - Dam Inspection Report (PDF - 288 Kb)
• Appendix 4 - NH Fisheries Data (PDF - 175 Kb)
• Appendix 5 - Wetland Report (PDF - 2.3 Mb)
• Appendix 6 - Site Survey (PDF - 0.6 Mb)
• Appendix 7 - Hydraulics, Fish Passage, and Cost Estimates (PDF - 1.9 Mb)
• Appendix 8 - FEMA Data (PDF - 1 Mb)
• Appendix 9 - Sediment Analytical Results (PDF - 4 Mb)
• Appendix 10 - CRREL Ice Letter (PDF - 152 Kb)

• List of Figures in the Feasibility Study
  

The purpose of the Winnicut Dam Removal Feasibility Study (Feasibility Study) is to evaluate options for the restoration of native diadromous and resident fisheries, including alewife and blueback herring, in the Winnicut River ecosystem. The primary objective for achieving this restoration goal would be to improve upstream and downstream fish passage within the Winnicut River, with a secondary objective of enhancing the overall function of the Winnicut River ecosystem. The feasibility of each option was assessed with respect to its impacts to adjacent infrastructure, groundwater and wells, recreational use, natural resources, and historical and archeological resources.

The Winnicut Dam is owned by the New Hampshire of Fish and Game Department (NHFGD). It is situated at the head-of-tide on the Winnicut River in Greenland, New Hampshire, and represents the only anthropogenic barrier to upstream fish movement along the main stem of the river. The dam currently restricts fish movement within the Winnicut River, which in turn affects other ecological systems that are dependent upon the fish populations for dispersal within the ecosystem.

Although a fish ladder was incorporated into the dam at the time of its construction in 1957, its design has proven to be inefficient in providing upstream passage for most diadromous and resident fish species. Because the fish ladder is currently only operated to accommodate upstream migration of anadromous river herring in the spring, it is of limited utility in providing a means of upstream passage for anadromous rainbow smelt and catadromous American eel. Cumulatively, the poor performance and limited window of operation of the existing fish ladder combined with lack of dedicated downstream fish passage has adversely impacted the use of the Winnicut River by diadromous and resident fish.

Three primary alternatives for achieving the project goals are presented in this Feasibility Study. Alternative A is the "No Action" alternative. Alternatives B and C present differing approaches intended to achieve the project goals.

Alternative A, the No Action alternative, does not meet the basic project goals of restoring resident and diadromous fisheries in the Winnicut River, but is included as a baseline for the purpose of comparing the affects of the other alternatives. This alternative avoids some shortterm, temporary impacts associated with the other alternatives, but does not address impacts to fisheries associated with the Winnicut Dam, with the primary impact being the poor performance of the existing fish ladder. Under the No Action alternative, adverse impacts associated with the presence of the dam and the existing fish ladder would continue and would constitute a long-term impact to the natural resources dependent upon upstream and downstream fish passage and factors such as the loss of riverine habitat resulting from the presence of the Winnicut Dam. Alternative B would involve the construction of an Alaska Steeppass technical fishpass in place of the existing Canadian step weir fish ladder at the Winnicut Dam. This alternative meets some of the projects needs through the implementation of improved fish passage at the Winnicut Dam, but does not provide for increased free-flowing riverine habitat or enhanced downstream fish passage.

Alternative C would involve the removal of the Winnicut Dam and the construction of a technical fishpass under the State Route 33 Bridge (Rte 33 Bridge). The alternative would meet the project goal through the improvement of upstream and downstream fish passage and the restoration of approximately 250 feet of the Winnicut River below the Rte 33 Bridge to riverine conditions. The restoration of the riverine habitat is particularly important for achieving project objectives associated with the restoration of rainbow smelt populations in the Winnicut River, as this species is dependent upon riverine habitat for spawning and is not capable of ascending most types of fishpass systems.

Alternative C is the preferred option based on its ability to achieve the project goals associated with the restoration of resident and diadromous fisheries in the Winnicut River ecosystem. Specific benefits of this alternative include the restoration of riverine habitat that is suitable and accessible for spawning by smelt and improved upstream and downstream fish passage.

The Feasibility Study Project Partners include the New Hampshire Coastal Program at the Department of Environmental Services (NHDES), the New Hampshire Fish and Game Department (NHFGD), the National Oceanic and Atmospheric Administration Restoration Center (NOAA), the University of New Hampshire, and the Coastal Conservation Association. Project Partners who actively participated in the Feasibility Study include NHFGD, NHDES and NOAA. The Feasibility Study was performed by Woodlot Alternatives, Inc. (now Stantech) of Topsham, Maine, in coordination with Alden Research Laboratory, Inc. of Holden, Massachusetts, Public Archeology Library, Inc. of Pawtucket, Rhode Island, and Wright-Pierce, Inc. of Topsham, Maine.

Figures 10 and 12 are embedded in the body of the report. To view those figures click on the following link: Feasibility Study (PDF - 7.5 Mb)

• Figure 1 - Dam Location and Drainage Delineation (PDF 298 KB)
• Figure 2 - Selected Dams in the Great Bay Ecosystem (PDF 1.21 MB)
• Figure 3 - Conceptual Nature-Like Fish Ramp (PDF 85.8 KB)
• Figure 4 - Alternative B. Alaska Steeppass Fishpass (PDF 43.7 MB)
• Figure 5 - Conceptual Rock Fish Ramp (PDF 119 KB)
• Figure 6 - Wetland Reaches (PDF 2.56 MB)
• Figure 7 - Drainage Delineation for Oyster and Winnicut Rivers (PDF 344 KB)
• Figure 8 - Flow Duration Curve (PDF 55.4 KB)
• Figure 9 - Limit of Backwater During High and Low Flows (PDF 193 KB)
• Figure 11 - Estimated Sediment Volume (PDF 132 KB)
• Figure 13 - Sediment Sample Locations (PDF 217 KB)
• Figure 14 - Expected Wetland Impact (PDF 2.54 MB)
• Figure 15 - Wetland Delineation at Dam (PDF 582 KB)