The Oak Grove Hydroelectric Project is a 44 megawatt hydroelectric plant operated by Portland General Electric (PGE) on the Oak Grove Fork Clackamas River. Water for this project is held by three lakes, built between 1923 and 1956.[1] The dam creates the impoundment Lake Harriet.
In 1907, the Southern Pacific Company began to acquire water rights for the Oak Grove fork.[2] These rights were transferred in 1911 to the Portland Railway, Light and Power Company,[2] which later became PGE.
In 1923, the concrete diversion dam at Lake Harriet was completed. This lake holds [3] with a surface area of 150acres.[4] A 9feet pipeline goes downstream from Lake Harriet to the powerhouse.[3] Power generation from the Oak Grove fork began in August 1924.[5]
In 1953, Frog Lake was completed, adding of storage with 13acres of surface, which was later reduced to on 6acres in 1997.[3] Finally, in 1956,[2] the compacted-earth dam for Timothy Lake was completed, creating the largest lake in the system at 1430acres and . The Oak Grove Powerhouse contains two Francis turbines.