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Dworshak Oil Spill Into North Fork Clearwater Slows Turbine Overhaul, Cleanup Continues by Staff Columbia Basin Bulletin, September 23, 2016

The contractor was to first remove the oil from a chamber
containing the bearings and they instead removed the bearings first.

As a U.S. Army Corps of Engineers contractor began disassembling generator unit-3 for overhaul at Dworshak Dam in Idaho Monday, about 291 gallons of oil spilled from the units' guide ball bearings at 10:30 am.

Some 260 gallons of the light grade turbine oil was immediately retrieved and more was soaked up by absorbents, said Steve Hall of the Corps' Walla Walla District at Wednesday's interagency Technical Management Team meeting.

Overall, the Corps estimates about 10 to 20 gallons of the oil was released into the North Fork of the Clearwater River. It is determining the exact amount of oil as clean-up operations continue, according to Corps information.

Hall said there is some oil on the surface of the river as far downstream as the North Fork hatchery.

The contractor responsible for the turbine overhaul simply did not follow the procedures that the Corps had clearly outlined for them, Hall said. The contractor was to first remove the oil from a chamber containing the bearings and they instead removed the bearings first.

The Corps said of the oil spill that:

• Containment and recovery efforts began immediately after the oil spill was reported.

• Sump pumps were shut down to prevent further release into the river.

• Downstream fish hatcheries were quickly notified.

• Corps reservoir managers reduced outflows from Dworshak to slow downstream movement of any oil that made it into the river to potentially assist in containment and recovery.

• The Corps' spill-response team at Dworshak responded by boat and spill trailer to the Ahsahka bridge near the North Fork's confluence with the Clearwater River to attempt recovery.

• A spill-response team from Pasco assisted the contractor with oil-recovery efforts.

• The Corps ensured appropriate federal, state, community and tribal agencies were notified of the spill.

Still, the contractor will attempt to remain on schedule by removing the generator's rotor by October 11, the windings by October 29, the stator core by November 5 and then reverse that process December 8. The rotor assembly will be replaced by January 24, the windings installed by March 11 and the whole assembly is to be done April 15, with tests during May and June, and have the unit tested and running by July 1.

Unit-3 is the largest of Dworshak's three turbines, rated at about 220 megawatts. That limits the powerhouse capacity at the dam to about 45 percent of normal, but it will also limit the amount of discharge from the dam to about 4,800 cubic feet per second.

"With the large unit out of service, it may be necessary to spill more water than otherwise would be spilled to maintain flood protection," said the State of Idaho in a September 2, "Priorities for Operational Objectives – Dworshak Dam" white paper that TMT is currently reviewing.

The state laid out its priorities for operating the dam during the time that unit-3 will be out of service (www.nwd-wc.usace.army.mil/tmt/agendas/2016/0907_Dworshak_16-17_Idaho_recommended_operational_priorities.pdf):

• Maintain a 95 percent probability of refilling the project for cold water flow augmentation in summer 2017, as is required in NOAA Fisheries' 2014 Federal Columbia River Power System biological opinion.

• Avoid exceeding the Idaho water quality standard total concentration of dissolved gas of 110 percent.

• Operate to the early April flood control elevation with the large turbine out of service.

TMT has yet to adopt Idaho's operations recommendations and will continue to debate the recommendations over the next several weeks.