Reservoir Pond Dam

Canton, MA

The Town of Canton recently obtained ownership this Large Size, Significant Hazard dam after a private developer purchased former mill property inclusive of the dam. The crest carries Pleasant Street, a Town road, while the Dam was privately owned until the transfer. The Town engaged SA to review history and documentation of previous, unsuccessful repairs, and to design new repairs to mitigate persistent uncontrolled seepage, improve operations, reduce future maintenance costs, and improve dam safety.

Following document review, SA conceptualized alternatives for repair and estimated costs for design, permitting and construction of the alternatives to assist the Town in budgeting. SA subsequently designed and prepared permit applications for a temporary cofferdam to reduce seepage risks to the Dam while maintaining Pond elevations near normal levels for wetland resource protection and public recreational use while repairs were designed.

The Dam and Pond are used for both recreation and flood control, attenuating flooding to protect downstream areas, including the Town Center. SA evaluated hydrology and hydraulics using the most recent precipitation predictions, and found that the Dam as previously configured and operated was no longer capable of safely passing the spillway design flood. SA designed a new primary spillway to pass the deign flood while mitigating seepage through the former stone masonry raceway, and optimized spillway operations to maintain previous seasonal pool elevations for recreation, maintain adequate freeboard during floods, and limit downstream flood flows to no greater than the previous configuration and operation.

SA also performed subsurface explorations, evaluated subsurface seepage by 2D-finite element modeling, and designed embankment drainage and soil filters to control seepage. SA prepared an operation and maintenance manual and design/contract documents, applied for applicable permits, and assisted the Town during project bidding. Design, permitting and bidding is complete, and the project is ready for construction, which SA plans to observe on the Town’s behalf.