According to the U.S. Army Corps of Engineers, the leak occurred while maintenance staff was replacing the oil in three of the dam’s six power transformer heat exchangers or “cooling units.” Oil escaped from an open transfer connection, onto a concrete floor in the powerhouse and into a drain running to the powerhouse drainage sump.
Maintenance crews immediately shut down oil-transfer operations and used absorbent pads to recover oil on floor. Of the 64 gallons of oil that leaked from the open transfer connection, approximately 15 gallons were recovered in the dam during Ice Harbor staffs’ spill-response actions, 5 gallons remained in the oil transfer hoses, leaving 44 gallons of oil unaccounted for and assumed to have eventually been discharged to the river.
Corps staff notified the National Response Center, Washington Emergency Management and the Washington Dept. of Ecology. A collection boom was deployed at the dam’s discharge point.
Two boat response crews were assembled to scout the river and deployed collection booms where a sheen was spotted. An additional spill-response team from Lower Monumental Lock and Dam joined Ice Harbor’s crew to accelerate cleanup and recovery operations continuing into Tuesday.