The Old Mill Dam on Pearl Street in Bellingham.
12/20/2016 Update: The removal of the Old Mill Dam in Bellngham has begun!
This year, the Town of Bellingham will begin work to remove the Old Mill Dam on Peal Street in Bellingham, making Mill Dam the first Charles River dam to be removed. The Town of Bellingham is the first town to begin a dam removal project in the Charles River Watershed. This project was made possible with financial support from the Massachusetts’ Executive Office of Energy and Environmental Affairs Dam and Seawall Repair or Removal Program and technical support from the Department of Fish and Game’s Division of Ecological Restoration (DER). Removing the dam, which is unsafe in its current state, will reconnect 9.2 miles of river habitat upstream of the dam to 50 miles of unobstructed river downstream.
The pond behind the Old Mill Dam
In addition to removing the dam structure from the river, the restoration project will include dredging of the pond behind the dam. DER tested the sediment that has accumulated in the pond and has found trace levels of mercury contamination. In its current state, the sediment does not pose a threat to humans or wildlife. However, if the sediment were to be left in place during the dam removal process, it would be released to the wetlands downstream. The low-oxygen conditions found in wetlands are conducive to the production of methyl mercury, which is harmful. Consequently, the contractor for the project will dredge the accumulated sediment from the riverbed before removing the dam. The sediment will be used to fill in an area that has ponded and become filled with cattails due to backwatering from the dam. The filled area will be covered with stabilizing fabric and clean fill material to create an upland area in which the sediment will be retained away from the river. Although it is normal for a dam removal project to temporarily impact water quality and sediment movement in a river, we expect that there will be no measurable impacts to water quality and sedimentation within a year after the project has been completed.
Other site improvements will include demolition of deteriorating structures and installation of new stormwater management infrastructure. The old mill buildings themselves, which are located downstream of the dam, are currently being removed as part of a separate project. As part of the restoration project, the Town of Bellingham will construct a new treatment basin to clean polluted stormwater runoff from a portion of Pearl Street. The treatment basin will reduce the amount of phosphorous pollution that enters the Charles River and will make a large contribution toward meeting the phosphorus reduction goals CRWA established under the Total Maximum Daily Load (TMDL) for the Upper Charles River Watershed.
We currently anticipate that the dam removal and dredging will be largely completed by February of 2017, with additional site stabilization and planting to be performed in the spring of 2017. The Town of Bellingham will provide notice of any anticipated impacts to road access over the course of the project.
CRWA is very pleased with the initiative the Town of Bellingham has taken with this project and hopes that this project will serve as an example for future dam removal and environmental restoration projects on the Charles River.
Mill Dam Removal FAQ
- Why is the dam being removed?
- Removing the dam will improve the health of the river, improve public safety, and reduce future maintenance costs for the Town of Bellingham. This project will improve the health and safety of the Charles River downstream, as well.
- How does removing the dam improve river health?
- Removing the dam restores the free flow of water and sediment. It also allows fish and other wildlife to travel between portions of the river. Dam removal converts an human-made impoundment back to free flow conditions with improved water quality.
- What are the short term impacts of the dam removal project?
- Dredging the sediment from the river bottom and removing a concrete channel from the river will stir up sediment. The river may look cloudy for a few days to a few weeks. This is expected during a project like this. The impacts are minor and short term. Animals living in the river will generally be able to find refuge as needed like they would during a rainstorm. In the medium to long term, the entire river, including wildlife, benefits from having the dam removed.
- What is the schedule for the project?
- Construction is anticipated to begin in early November. The dam removal and dredging will occur between November of 2016 and February of 2017. Additional drainage improvements, repaving, and revegetation will occur between April and June of 2017.