The most recent Natel/Pacific Northwest National Laboratory test of 186 large rainbow trout measuring up to 500 mm (19. 7 inches) in length, found no meaningful difference between the fish passed through Natel’s 1.9 meter (roughly 6 feet) in diameter turbine and the control group, indicating that the RHT allows safe passage of some of the largest fish ever successfully passed through a compact hydro turbine.
In 2019 Tony Grassi, owner of The Mill at Freedom Falls, partnered with Natel to install the first Restoration Hydro Turbine.