As the U.S. Army Corps of Engineers team at Ice Harbor Lock and Dam performs repairs of power transformer heat exchangers or “cooling units” that recently leaked oil into the river, the Corps says it is taking precautions to protect Endangered Species Act-listed fish.
Generator main unit #3 had been out of service since Feb. 14 to repair its transformer cooling units. Prior to re-starting it this week in order to remove water in the turbine area, the Ice Harbor team was required by the federal Fish Passage Plan to “spin” or run water through the turbine because there likely would be fish remaining in the turbine’s draft tube. However, a small amount of oil had likely accumulated in the turbine area, so the team created a plan to remove that oil without harming fish and simultaneously minimize the risk of oil leaking into the river when the turbine was spun.
The plan was reviewed in advance by the Washington Department of Ecology and U.S. Environmental Protection Agency during their Ice Harbor inspection on March 13.
The plan was to inject air into the unit prior to “spin” to help oil move to a high point in the turbine area, where oil could more easily be removed. Also, as the turbine was spun, the Ice Harbor team would position boats with oil absorption booms below the dam to capture remaining oil that might leak into the river.
The team began implementing the plan on March 13 and completed it March 14. While some oil was captured from the turbine-area high point, a silver sheen was observed downstream, and oil-absorbent-boom-equipped boats converged on that area to collect oil. An estimated 5 to 10 gallons of oil entered the river.
Previously, oil cooling units had been traced as the likely source of an oil sheen observed by Corps staff and reported to state officials in December and January.
The transformers and cooling units are being repaired; part of the repair process is to replace clean oil into the transformers and cooling units.
During a Feb. 27 cooling unit oil-flushing operation, oil escaped from an open transfer connection, onto a concrete floor in the powerhouse and into a drain running to the powerhouse drainage sump. An estimated 44 gallons of oil leaked into the river at this time, and Corps clean-up efforts were made by crews from Ice Harbor and Lower Monumental Lock and Dam.
For more information see CBB, Feb. 3, 2012, “Corps Identifies Source Of Oil Leaks At Ice Harbor Dam; Testing Other Dams For PCBs In Oil” http://www.cbbulletin.com/416159.aspx