Wednesday, February 21, 2024

Spill slated to end - finally

| June 28, 2006 12:00 AM

By mid-day Tuesday, the spill was scheduled to have ended at Libby Dam 19 days after it started to make room in Lake Koocanusa for rapidly rising runoff fed by an unusually wet month of weather.

"We expect to have no spill by 1 p.m. Tuesday," said Mick Shea, project manager for the U.S. Army Corps of Engineers.

The reservoir topped full pool more than a week ago by just a few inches before outflows from the dam were boosted to 55,000 cubic-feet per second including 31,000 cfs from the dam's spillway.

The 19 days of higher than usual flows took its toll on dikes protecting structures and agricultural fields in the Bonners Ferry area. Damage estimates to the dikes ran as high as $1 million a mile with 54 miles of earthen structure as in bad shape. In addition, ground water seepage has flooded fields causing at least $2.6 million in crop damage.

On the edge of downtown Bonners Ferry, there was water damage at Kootenai River Inn.

By late Monday, the river was a couple of feet below flood stage at the north Idaho city for the first time in weeks. The high flows in north Idaho were due to Libby Dam releasing so much water plus the high natural runoff boosting the downstream streams and rivers entering the Kootenai.

The biggest unknown may be the damage to the Kootenai River fishery, especially between Libby and the dam. Brian Marotz, fisheries projects manager for Montana Fish, Wildlife and Parks, told the Columbia River Bulletin, that the spill's volume and duration was unprecedented for the Kootenai River. And it is having an adverse effect on fish, he told the Internet newsletter.

Water rushing down the Libby Dam spillway in volumes higher than 1,700 cfs causes a high concentration of dissolved gas in the Kootenai River immediately downstream. The gas bubbles cause gas bubble trauma in fish.

"It will help with the spill reducing, but really it is the duration of spill that is biologically important because the symptoms in fish ramp up over time," Marotz said.

In 2002, the last time the corps was forced to spill water to make room in the reservoir, state fishery crews discovered that gas bubble trauma appeared seven days. This years fish were showing less impact during surveys conducted a week into the spill. That changed drastically after 12 days, Marotz said.

By Monday, June 19, every bull trout sampled by state Fish, Wildlife and Parks crews had gas bubble trauma, Marotz said. He reported seeing bubbles in eyes, in fins and fish had split fins, also believed to be caused by gas bubble trauma.

Also, FWP biologists observed the fish had little bloody pin pricks on their undersides. That was not seen in 2002 and Marotz said it was common last week with nearly every bull trout, a species listed as endangered. About 80 percent of last week's samples of rainbow and cutthroat trout had symptoms, and about 70 percent of mountain whitefish showed symptoms.

Two weeks ago, Marotz reported that symptoms were higher on fish caught along the left bank of the river immediately downstream of the dam since the gas bubbles seem to hug that riverbank. After a week of spill, he said the concentrations were almost even across the river.

State biologists are unsure how much gas bubble trauma the fishery can sustain because they've never dealt with it before. Marotz said it was possible fish were dying and settling to the bottom of the river. When flows are dropped to a safe level, divers will scour the subsurface for bodies, he said.

Additional surveys are expected as far downriver as the Libby bridge for Montana Highway 37.

Since the 2002 spill, river guides have claimed that the trophy-sized fish had all but disappeared from the river and were just making a comeback. FWP biologists had numerous fish tagged with devices that can be traced electronically to see if the fish moved downstream as claimed by the guides.