The Mill at Freedom Falls

Freedom, Maine
Project Stats
Turbine Supply:
Natel Energy
Project Developer:
Natel Energy
35 kW
7 m (23 ft)
Number of RHT Units:
RHT Unit Diameter:
.55 m (3 ft)
RHT Unit Type:
Commission Date:
December 2019

The historic Freedom Falls Mill is situated on the headwaters of Sandy Stream in central Maine. The project delivers 35 kW to the surrounding community and directly to the operation of The Mill’s Lost Kitchen restaurant. Average annual generation is approximately 65 MWh per year.

The original dam structure was constructed as a gristmill in 1834. The property operated as a gristmill from 1834 until about 1894, and then as a woodturning mill until about 1967. From 1967 to 2012, the Mill at Freedom Falls was abandoned. In 2012, the Mill was purchased by Tony Grassi, who rehabilitated the mill and added hydropower generation. In 2019, Grassi partnered with Natel to install the first FishSafe™ Restoration Hydro Turbine as a demonstration site. In 2023, Grassi sold the mill to the owners of the Lost Kitchen restaurant, who continue to operate the project. This project includes upstream and downstream passage facilities for American eel.

The dam is a 12-foot tall, 90-foot-long stone masonry concrete-capped structure. Water is conveyed from the dam to the powerhouse through a 60-foot-long penstock that creates a short bypassed reach in Sandy Stream. The project operates in run-of-river mode and impounds a 1.6-acre mill pond downstream of Sandy Pond. Pond level sensors on the upstream face of the dam send readings to a turbine control system which ensures instantaneous run-of-river operations. The project provides a 3 cfs spillway flow to maintain aesthetics of the spillway and keeps the bypassed stream be watered. This flow regime is based on conditions stipulated by the US Department of Interior under the FERC license for the project.

The Freedom Falls Mill is certified as a Low Impact Hydropower project by the Low Impact Hydropower Institute (an independent non-profit organization) to have environmental impacts in key areas below levels the Institute considers as the maximum acceptable for hydropower facilities. For more information about the certification, please visit

Watch how the RHT was installed at Freedom Falls: