A mechanical breakdown at central Idaho's Dworshak Dam will limit fish and hydro managers' ability this summer to control the reservoir's cool waters to augment flows downriver and, more importantly, help hold down water temperatures for migrating salmon and steelhead.

That's the bad news. The good news is that is that the Snake River is running cooler, at least to this point, than it would normally be at this time of the year. The water temperature at the lower Snake's Lower Granite Dam was 65.5 degrees at midweek. The Dworshak reservoir's coldest water has been called on in the past even prior to July 4 to dampen temperatures downstream.

"They are staying low," the U.S Army Corps of Engineers' Jim Adams said during Wednesday's Technical Management Team meeting. "We're not expecting major issues at Lower Granite."

The TMT's federal, state and tribal salmon and hydro managers assemble to discuss day-to-day Federal Columbia River Power System operational adjustments that might be made to benefit salmon that are listed under the Endangered Species Act. A goal is to keep water temperatures, as measured at Lower Granite, below 68 degrees. Higher temperatures are unhealthy for the coldwater fish.

Dworshak's deep reservoir holds water that can be 40 degrees or colder. It is called on in late summer, flushing down the Clearwater River and into the tepid Snake. That water can be released through turbines, through spillways near the surface and through three "regulating outlet" gates. The spillway draws warmer water from near the surface; the ROs, located nearly 200 feet below the spillway crest, release the coldest water.

Those ROs are effectively out of commission. Officials at the dam last Thursday, July 24, discovered that RO2 was passing water and did not fully close during operations. Water from the malfunctioning gate began to leak water into a machinery room down a maintenance passageway and out the downstream face of the dam.

Maintenance crews worked late into the night to finish positioning a bulkhead and stopped the water flow at about 3:30 a.m. last Friday. The bulkhead is a device lowered by crane into position to stop water from entering the gate areas of the dam.

After the leak stopped, crews inspected the gate and noticed the pin connecting the cylinder to the top of the gate worked itself free, preventing workers from raising or lowering the gate.

"There's significant damage there. It will take several months to repair," the Corps' Steven Hall told TMT members. Meanwhile the facilities only bulkhead must stay in place at RO2 and can't be used for inspections of suspect pins in the other two gates.

"My understanding is that there is nothing they can do to lock that gate in place" so the bulkhead cannot be removed, Hall said. If the gate broke open, the reservoir would eventually be drawn down to 1,350 feet –250 feet below full pool.

At this point the Corps is weighing the risk of inspecting the other ROs without the safety provided by a bulkhead. If power to the other gates is lost and water forced its way through, the workers could be washed downstream. The ROs empty about halfway up the face of the spillway.

"We're going to have to get at least commander-level approval" for any inspection, Hall said. Because the gates are of identical design, they may also have the same weakness so need to be inspected.

The equipment failure may have resulted from excess wear and tear. Recent testing involved repeated opening and closing of RO2, Hall said.

If the other two gates prove to be in good condition, potentially they could be opened to some degree to allow a constant flow.

"We're not going to want to adjust them on a frequent basis," Hall said. That option is "still taking some amount of risk" of emptying the reservoir if the gates fail.

The Corps may use cameras to inspect the machinery remotely, he said. The Corps is also checking to see if its Libby Dam in northwest Montana might have a bulkhead that could be used at Dworshak.

The reservoir elevation at the end of the day Tuesday was 1,583.9 feet. The goal is to augment flows for fish, dropping the reservoir level to 1,535 by the end of August, and 1,520 by the end of September.

That will be more difficult with the ROs out of action. The spillway crest is at 1,345 so that option for releasing water is lost when the reservoir level falls to about 1,350, the Hall said. The dam's Corps operators are now running the dam at full powerhouse (about 10,000 cubic feet per second) and spilling about 4 kcfs.

The worst-case scenario is that all three ROs will have to remain closed through the summer. The Corps expects the reservoir level to drop to 1,350 by about Aug. 20 or Aug. 21 using the current turbine-spill operation.

"Beyond that we may have a difficult time drawing the reservoir down as fast as we'd like," Hall said.

Meanwhile the dam's turbine-spill output is 49 degrees and expected to slowly rise as the summer passes. Of concern is a U.S. Fish and Wildlife Service hatchery just downstream that draws water from the Clearwater to rear juvenile chinook and steelhead.

The USFWS's Dave Wills said temperatures rising above 52 degrees exacerbate disease control and prevention in the rearing ponds. The Corps' Jim Adams said the amount of spill could be ramped down if needed, reducing the amount of warmer water being released. Again that would reduce the chances of meeting the court-ordered end of August drawdown target.