Lake Jefferson

About Lake Jefferson

The primary purpose of Lake Jefferson 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 Barbara A. & Kevin J. Gref (private). It impounds the East Branch Callicoon Creek near Jeffersonville.

The dam stands 22 feet tall and stretches 220 feet across, creates a reservoir covering 30 acres, has a maximum storage capacity of 350 acre-feet, and collects water from a drainage area of 30 square miles. Completed in 1927, 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 unsatisfactory, indicating serious safety deficiencies exist that require immediate attention or remedial action. An emergency action plan is in place for this dam. The most recent inspection on record was 06/05/2025.

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

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