Millbrook Dam Emergency Spillway
Built in the 1820s, the Millbrook Dam is a cultural landmark in the local Millbrook, Ontario community. Millbrook has had a mill since the community was founded, and was named as such because of the presence of a mill on a brook. Otonabee Regional Conservation Authority (ORCA), which owns the dam, needed to replace the dam because it was deemed unsafe. At 200 years old, there were concerns that a major rainfall could cause the dam to fail, and ultimately flood downtown Millbrook.
The project involved engineering innovation to resolve foundation material and seepage challenge, while providing an optimized design for capacity. The 'As Low as Reasonably Practicable' (ALARP) principle was applied to develop a spillway hydraulic capacity solution and emergency embankment overflow that would be acceptable to the Ontario LRIA Dam Safety Guidelines.
Flexamat was selected to armor the emergency embankment overflow. Flexamat would protect the earthen embankment during high flood events while aesthetically conforming with the historical site.
The existing spillway was the only outlet for the river/pond. Care was taken during the dewatering to rescue and release over 800 fish, crayfish, turtles, frogs, and otters. Upon project completion, these species are all once again thriving. The pond remains an important resting area for geese and ducks.
The reconstruction of the Millbrook Dam renewed confidence in the dam safety for residents of Millbrook as well as preserving the historical and social characteristics for the enjoyment of future generations.
