Consulting Solutions that Work for People and the Environment

Merrimack Village Dam Removal

After five years, including two Patriot Super Bowl victories and two Red Sox World Series wins, the Merrimack Village Dam on the Souhegan River in Merrimack, NH was finally removed in July-August 2008. The dam, owned by Pennichuck Water Works, was the lowermost dam on the Souhegan River, a tributary to the Merrimack River. With its removal, migratory fish can once again ascend the Souhegan River as 14 miles of riverine habitat were opened.

One of the interesting facets of the project involved allowing for the natural transport of impounded sediment during and after the removal process. Thousands of cubic yards of sand were allowed to naturally transport downstream after sediment testing was conducted and evaluations that habitats below the dam would not be compromised. It is one of the few projects in the northeast where considerable pre and post-monitoring of geomorphic changes above and below the dam are being conducted. In fact, post-monitoring studies of geomorphic changes will continue for the next two to three years following the dam’s removal. In addition to geomorphic changes, pre and post-monitoring studies are also being conducted on plants, macroinvertebrates, and fish. The monitoring studies will allow professionals to understand how the physical environment above and below the dam changes over time.

Gomez and Sullivan worked closely with several Project Partners throughout the process to secure financial assistance from federal, state and non-profit grantors that helped to defray a portion of the feasibility and removal costs. Pennichuck and Gomez and Sullivan were extremely fortunate to have a group of dedicated and talented individuals throughout the process. Eric Derleth with the US Fish and Wildlife Service, Eric Hutchins with the National Oceanic and Atmospheric Administration and Debbie Loiselle with the NH Department of Environmental Services were integral members of the team and we truly appreciated their commitment to the project.

Removal of the Merrimack Village Dam was a challenging endeavor as it required varied components of professional expertise in environmental investigation, engineering and design, and perhaps most importantly, public outreach and education. Our experience has found the most challenging aspect of dam removals to be educating the public and working at the local level. Establishing relationships with local individuals and maintaining open and consistent communications throughout the process is essential, leading to a much smoother overall project.