River Mill Hydroelectric Project
| Company type | Hydroelectric facility |
|---|---|
| Industry | Energy |
| Founded | 1911 |
| Headquarters | Clackamas County , United States |
Area served | Clackamas River, Oregon |
| Owner | Portland General Electric |
River Mill Hydroelectric Project, frequently referred to as River Mill Dam or Station M, is a hydroelectric facility located in Clackamas County, Oregon, close to Estacada, Oregon, positioned on the Clackamas River at river mile 23.5 (km 37.8). Its name derives from a nearby sawmill, and it has been generating hydroelectric energy without interruption since 1911, originally financed by the Portland Railway, Light and Power Company.
This dam was part of a quartet of interconnected developments along the Clackamas River, which also included the Oak Grove Hydroelectric Project (operational from 1923 to 1956), the North Fork dam (completed in 1958), and the Faraday Dam (constructed between 1907 and 1910), all situated upstream. Apart from the Faraday Dam, which was dismantled in 2018, the other projects continue to be owned and managed by Portland General Electric.
The design of the dam was created by Norwegian-born engineer Nils F. Ambursen (1876–1958) of the Ambursen Hydraulic Construction Company, recognized for building over one hundred dams across the United States between 1903 and 1917. Ambursen’s innovative concrete-slab-and-buttress structural system was pioneering at that time; River Mill stands as one of just three dams utilizing this Ambursen design located west of the Mississippi River.
This facility is officially registered on the National Register of Historic Places and is documented within the Oregon Historic Sites Database maintained by the Oregon State Historic Preservation Office.