Marmot Dam Rehabilitation Project

Marmot Dam is a diversion structure located on the Sandy River at the upper end of Portland General Electric's (PGE) Bull Run Hydroelectric Project. The project is located about 30 miles east of Portland, near the town of Sandy, Oregon. The original Marmot structure was a 195-foot long 45-foot high rock-filled timber crib dam that was used to divert water to the Bull Run powerhouse. That dam was replaced with a new dam in 1989 as part of the Marmot Dam Rehabilitation Project. Normal to the axis of Marmot Dam is an additional overflow wing dam section. This wing dam section is a 150-foot long 6.5-foot high concrete gravity structure which is constructed on top of a natural rock ledge along the right bank. An intake structure that diverts flow to the powerhouse is located along the right abutment and a fish ladder is located along the left abutment. The reservoir behind the dam is infilled with river sediment to such an extent that only a few feet of water is stored behind the dam.