Middle Dam

About Middle Dam

The primary purpose of Middle Dam is hydroelectric. The dam generates hydroelectric power by channeling water through turbines, converting the energy of flowing water into electricity. The dam is owned by Brookfield Renewable Power Llc Nyro (private). It impounds the Rapid River near Errol.

The dam stands 22 feet tall and stretches 1,004 feet across, creates a reservoir covering 7,470 acres, has a maximum storage capacity of 130,738 acre-feet, and collects water from a drainage area of 472 square miles. Completed in 1883, the structure is over a century old.

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 07/26/2022.

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 Maine dam safety program can provide more specific information about emergency planning for this structure.

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