Lower Shannock Falls Dam Removal
Challenges
There were multiple hurdles that needed to be overcome before the dam could be removed. Design issues were complicated as stakeholders wished to minimize changes to the river’s morphology. However, bedrock in the area was not stable enough to safely navigate river herring upstream and allow for a full dam removal. The water quality and sediment were degraded by more than a century’s worth of upstream discharge of human and industrial waste, including the hazardous waste. Furthermore, at the time, it would have been the largest ecological dam removal undertaken in Rhode Island. Lastly, Pawtuxet Falls Dam was in a highly visible historic location and the dam and waterfall were part of the local landscape and sense of place.
Solutions
In 2010, the dam was removed and three weirs were installed to ensure that river flows met the migratory needs of the fish. The Knowles Mill Public Park was developed by the town of Richmond on the river bank below the falls providing trails as well as fishing and boating access downstream of the former dam. The historic smoke stack from the mill was left in place and interpretive signs were installed in the park to document the historic and cultural importance of the area.
Successes
Throughout the project, the project team consulted with the local community and the Narragansett Tribe. This collaboration allowed for the historical preservation concerns of the community to be addressed while allowing for the dam to be removed. By creating a public park surrounding the old dam site, public access to the river was enhanced. The history of the site is communicated through the preservation of ruins as well as signage in the park that displays historic photos.
The project benefited from a team experienced in fishery biology, hydrology/hydraulics, sediment transport, and water management. Completing the weirs in “dry” conditions helped achieve elevations and other design features required for fish passage. Testing river flows during and following construction allowed site-specific modifications that would help fish in their migration up and down the river.
