Montpelier, VT – Engineers, contractors, landowners, and scientists gathered in late May for the pre-construction meeting for the removal of Connolly Pond Dam in Shrewsbury Vermont. This week the excavator and dozer arrived and work is underway. The dam is being removed in the interest of public safety to reduce flood risk, and reconnect and restore a headwater tributary to the Mill River, which ultimately flows to the Otter Creek and then Lake Champlain.
Connolly Pond Dam Removal
Photo Credit: SLR Consulting
In 2020, the Vermont Dam Safety classified the dam as in poor condition with a Significant Hazard potential dam rating. The Dam Safety Inspection, stated that “Failure could result in damage and economic losses due to shallow flooding of property and overtopping of multiple road crossings.” “Downstream flood risk was reduced when the water level was drawn down in November 2020, but risk remains given the poor condition of the dam,” says Karina Dailey, Restoration Ecologist with VNRC.
The dam is reported to have been constructed c. 1965 for fire suppression, and to provide a water source for farm crops and livestock, and as a pond for recreation. The earthen embankment dam is about 6 to 15 feet tall and 320 feet long with a 50-foot-wide spillway.
The project is designed to reconnect the headwaters to the Mill River and ultimately Lake Champlain. Many co-benefits result from dam removals including restoring natural sediment transport, reduced erosion, restored aquatic organism passage (AOP), reconnection with the floodplain to support flood resilience, restored wetlands, stream channel processes, and a restored ecosystem with increased biodiversity.
SLR Consulting, the design engineers for this project recommended a relatively passive approach to dam removal for this project. “The plan is to remove the middle three-quarters of the dam while leaving the ends in place near the valley walls. This approach is the most cost-effective way to improve public safety, restore aquatic organism passage, and naturalize sediment transport. It also returns the site to the most likely pre-dam condition – creating a smooth transition between the upstream and downstream river corridors,” says Roy Schiff, Project Engineer. The earth from the dam embankment will be used to fill and re-form the east and west valley walls, therefore no sediment is being hauled off site, which also saves on dam removal costs.
The Connolly Pond Dam is owned by Amy Leah de Camp-Thomas & Jason Price. The dam is located behind 2165 Keiffer Road in Shrewsbury, VT. Karina Dailey, restoration ecologist with VNRC, is managing the project in partnership with the landowners. The engineering firm is SLR Consulting of Waterbury, and the construction firm completing the removal is Birdseye Construction of Richmond.
Funding for design, permitting, and construction has been provided by Vermont Natural Resources Council, NEIWPCC in partnership with the Lake Champlain Basin Program, the Vermont Department of Environmental Conservation through Watershed United Vermont, US Fish and Wildlife Service and the landowners.