Great Pond Upper Reservoir Dam

About Great Pond Upper Reservoir Dam

The primary purpose of Great Pond Upper Reservoir Dam is water supply. The dam stores water for municipal, industrial, or agricultural use, helping ensure a reliable supply for the surrounding area. The dam is owned by Tri-town Water Board (local government). It impounds the Norroway Brook near Braintree.

The dam stands 18 feet tall and stretches 2,775 feet across, creates a reservoir covering 200 acres, has a maximum storage capacity of 2,283 acre-feet, and collects water from a drainage area of 5 square miles. Completed in 1942, the structure is well-established, with more than 75 years of service.

This dam carries a high hazard potential classification, which means that a failure or uncontrolled release of water would likely cause loss of human life. This classification reflects the consequences of failure, not the likelihood — it indicates that people live or work in the area downstream. Its condition is rated fair — the dam has minor deficiencies that are being addressed or do not pose an immediate safety threat. An emergency action plan is in place for this dam. The most recent inspection on record was 08/18/2020.

Living Downstream

If you live or work downstream of this dam, consider taking these steps: learn your local evacuation routes, check whether your county emergency management office has a dam failure inundation map, and sign up for local emergency alerts. The Massachusetts dam safety program can provide more specific information about emergency planning for this structure.

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