Dam Removal Under Way at Pawtuxet Falls

On Tuesday afternoon, workers began work on the largest dam removal project yet undertaken in Rhode Island. By removing the concrete spillway of Pawtuxet Falls Dam, which spans the mouth of the Pawtuxet River, they will uncover a natural bedrock falls and restore seven miles of free-flowing river habitat to one of the state’s largest and most historic rivers.The dam deconstruction will be visible and can be photographed from Broad Street Bridge in Pawtuxet Village. 

The purpose of the project is to improve the ecosystems of the Pawtuxet River watershed and Narragansett Bay by restoring populations of native migratory fish, such as river herring and American shad, which have been blocked from fully accessing their natural spawning habitat for hundreds of years. Herring and shad are important components of marine and freshwater ecosystems, providing abundant food for bluefish, striped bass, largemouth bass, herons, ospreys and many other predators—even harbor seals, which winter in the Bay. In addition, the dam removal will provide modest flood reduction for homes and businesses, and improve water quality in the lower Pawtuxet River. 

The dam removal is sponsored by the Pawtuxet River Authority and Watershed Council, a state-chartered non-profit organization with the mission of restoring and preserving the Pawtuxet River, with the support of the Narragansett Bay Estuary Program, one of 28 National Estuary Programs established by Congress under the federal Clean Water Act. The project is funded through a partnership of more than a dozen federal, state, and non-profit organizations; construction is expected to cost about $600,000. Removal of the dam will lower the water surface in the river immediately upstream of the dam by about three feet, and by about two feet at Warwick Avenue. 

PRA’s construction contractor, SumCo Eco-Contracting of Salem, Mass., is staging the construction primarily from Hunter’s Garage, just south of the dam. SumCo will position a crane behind Hunter’s and use it to lower construction equipment into the river. A hydraulic hammer on a small excavator will be used to chip apart the concrete spillway, first creating a ten-foot slot in the dam, then using a large steel plate and one-ton sandbags to establish the river’s restored flow in a controlled way. SumCo will then remove the spillway section by section, using the sandbags as coffer dams to isolate each work area. The dam removal process is expected to take about two weeks.

As the water surface comes down to its restored level, new areas of riverbank will be exposed on each side. SumCo will plant native bushes and grasses on the exposed banks, beginning with downstream areas visible from the Broad Street Bridge. Upstream areas, including the riverbank at Rhodes-on-the-Pawtuxet, will be planted beginning in September. The entire restoration project is expected to be completed by the end of October, and we expect to see river herring and shad running back up the Pawtuxet River beginning next Spring, 2012. Fish will naturally find their way upstream once the dam is removed; however, R.I. Dept. of Environmental Management will transplant fish from other streams to accelerate the recovery process.

River herring and American shad were once highly abundant in Rhode Island’s rivers, an important component of the marine food web and the basis of a large fishery. Beginning in the 1700’s, however, more than 600 dams were built in Rhode Island to provide water power for the mills of the Industrial Revolution. The dams blocked the fishes’ access to historic spawning habitat and led to precipitous declines in their numbers. Biologists estimate that more than 100,000 herring and shad will return to spawn in the Pawtuxet following removal of the dam.  

In developing the restoration project, the PRA and its partners completed major engineering, environmental and cultural studies of the Pawtuxet River, examining river flow, sediments, wetlands, and historic resources in order to ensure that the dam removal will improve the environment of the Pawtuxet River and Narragansett Bay while avoiding adverse impacts to human health or economic uses. In order to begin construction, extensive permitting was necessary, including approvals by the R.I. Dept. of Environmental Management, R.I. Coastal Resources Management Council, and U.S. Army Corps of Engineers.

To follow progress on the dam removal work, visit the construction blog at: http://pawtuxet-falls-dam-destruction.blogspot.com/