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Cabinet Gorge Dam. Photo by George Perks Cabinet Gorge Dam. Photo by George Perks

Avista is Proactive and Prepared for threats to the Lower Clark Fork

Though autumn in our region is a time of brilliant colors, the harvest of root vegetables, and the anticipation of an exciting ski season, this fall is also the time that local agencies and groups get together to prepare for the occurrence of a particular emergency. In the unlikely event of a dam failure on the Lower Clark Fork River, how would downstream communities be affected? How prepared could they be? Where would people go for information?

Every two or three years, Avista, a Washington-based utility company that holds license to two dams on the lower Clark Fork River at Noxon Rapids and Cabinet Gorge, hosts comprehensive, face-to-face emergency exercises for everyone involved to ensure that each entity understands their responsibilities and can act quickly.

“We have an excellent safety program—our dams are inspected by company, state, and federal personnel on a regular schedule,” says Dave Ayres, Emergency Action Plan Coordinator for Avista.

The Federal Energy Regulatory Commission conducted the most recent annual inspection of Cabinet Gorge Dam in May and

Noxon Rapids Dam in August. “Both dams were deemed structurally sound, well-maintained, and in satisfactory operating condition with no significant problems or discrepancies,” Ayres explains.

In June, Avista hosted a “Tabletop Emergency Action Plan Exercise” as well as a more in-depth Functional EAP Exercise, which was held in early September. The EAP, which is a step-by-step plan that involves many different entities, from dam operators to emergency responders and schools downstream, ensures that everyone who can respond to an emergency of this nature will be able to respond swiftly and appropriately. The EAPs for both Cabinet Gorge and Noxon Rapids dams were formally developed in the early 1980s and are updated, improved, and tested annually.

At the Tabletop EAP Exercise in June at the Heron Community Center, all of the pertinent entities participated in a sit-down dam breach scenario, utilizing a PowerPoint presentation. Tabletop exercises aim to improve the EAPs, response procedures, and agency coordination; they help participants become familiar with emergency roles, resources, and procedures of other agencies as well as preparing them for a more in-depth Functional Exercise. There are no time constraints.

“The Tabletop Exercise is basically a stress-free situation—we go through a scenario that follows the flood wave down to Lake Pend Oreille to practice how everyone will react,” says Ayres.

At the Functional Exercise in September, the same agencies and entities attended to act out the EAP through a more-involved series of real-life simulated emergency situations. The Functional Exercise is an action-packed, higher stress version of the Tabletop Exercise that encourages first responders to act out simulated dam failure situations. It allows each person involved to discover how they would react to emergency events, and is an opportunity to learn how players can more effectively work together to respond in the face of a crisis, whether it be Mother Nature’s doing or one of our own.

“The Functional Exercise is timed and when the simulated flood wave is moving towards downstream residents, recreation areas, bridges, and roadways, there is a lot more pressure on each of the individual participants, particularly dispatch personnel,” explains Ayres.

In addition to these two exercises that are conducted every couple of years, all dam operators undergo an annual training EAP session. An annual EAP drill is also conducted for each facility. The annual drills are less involved than the Tabletop and Functional exercises; they measure the state of readiness of key personnel and ensure that the contact information on the notification flowcharts for each dam are current. These annual drills are often conducted “off hours”— weekends, holidays, or after the work day has ended

All agencies listed on the emergency notification flowcharts (including Sanders and Bonner County dispatch and sheriffs’ offices, Idaho State Patrol, Montana Highway Patrol, National Weather Service, Montana Rail Link, and downstream schools and resorts) were contacted by Avista System Operators and Hydro Safety personnel for the annual exercise. These exercises were held in late August.

Depending on the situation, and whether it is a potential dam breach emergency or an imminent failure, dam operators at Noxon Rapids and Cabinet Gorge initiate one of two plant-specific flowcharts. Most of the notification flowchart calls are made by operators at Avista’s System Operations Center and Generation Control Center in Spokane, both of which are manned 24 hours a day, 365 days a year. In the event of an emergency, the dam operators at Cabinet Gorge and/or Noxon Rapids contact the System Operators and GCC operators because the dam operators will be busy controlling spillgates, checking security cameras, activating sirens, and securing the plant. This process enables the agencies on the flowcharts to be contacted in an efficient and timely manner. Also note that both Cabinet Gorge and Noxon Rapids Dam are physically manned by operations personnel at all times.

Cabinet Gorge Dam was built in 1952 in response to the energy shortages in the Northwest. This unique concrete arch dam was constructed in just 21 months; the reservoir is 20 miles long and stores up to 105,000 acre feet of water. In the event of a dam failure at Cabinet Gorge, just eleven miles from the confluence with Lake Pend Oreille, peak flood elevations would occur in just 3.5 hours. The water would reach Lake Pend Oreille in 35 minutes but would only increase the lake by a maximum of one foot. Most of the town of Clark Fork would not be flooded—the bridge would be blocked off, and some of the lower elevations flooded, but most of the town would be fine.

“We still have a lot of people that believe the town [of Clark Fork] would be completely inundated,” says Clark Fork Mayor Tom Shields. “That is simply not true.”

Because all communities downstream of Cabinet Gorge are in Bonner County, Idaho, the first responder in the event of an emergency there would be the Bonner County Sheriff aided by the Idaho State Police. The Bonner County Dispatch would page the Clark Fork Valley Fire Department to sound the evacuation siren, located at City Hall.

Bonner County Commissioner Lewis Rich attended both exercises and commented on the difficulty that such an emergency situation would pose to county resources. “We would just have to make the best of a bad situation and continue on,” he said. “These exercises help us to prepare for the worst.”

Noxon Rapids was constructed in 1959; it possesses the greatest generating capacity of any of Avista’s eight hydroelectric facilities. It is located 2.5 miles upstream of the town of Noxon; the reservoir is 38 miles long and stores up to 400,000 acre feet of water. In the event of a dam failure at Noxon Rapids, the flood wave would reach Cabinet Gorge Dam in one hour. A complete failure of the dam could increase Lake Pend Oreille by a maximum of two feet. The town of Noxon would be 10 to 15 feet underwater, but the town of Heron would not be flooded, so the townspeople could seek refuge there. Noxon school principal Kelly Moore reports that they can have all the kids evacuated from the school and on high ground within 4.5 minutes of the siren being activated—the school practices this regularly and has two teachers who are also EMTs. Cabinet Gorge Dam would not be expected to breach, as its spillway capacity is greater than peak flood inflows.

In the case of a Noxon Rapids Dam failure situation, Sanders County Sheriff’s Office would direct all evacuation, mitigation, and rescue activities. The Sheriff would receive assistance from the Sanders County Emergency Management, the Noxon and Heron Volunteer Fire Departments, the Noxon Ambulance Association, the Cabinet Ranger District, and Sanders County Search and Rescue.

“I watch TV a lot and there is always a big wave. [These exercises] give us a better idea—we don’t have to get all excited because we should have time to respond in most situations,” says Sanders County 911 Dispatch Mark Denke. “We have to get our local people notified and these exercises help to do that.”

Both towns of Noxon and Clark Fork have emergency sirens with public address systems that were donated by Avista. The sirens can also be activated for other emergencies besides a dam failure, such as forest fires, a train derailment, or a hazardous materials spill. Though the town of Heron would be safe from the flood waters and a refuge for many evacuees, the Heron Bridge to access the town might be a different story. The Cabinet Gorge fish hatchery is immediately downstream of the dam, so in the case of a failure they know to “get out of Dodge if the siren went off,” says Ayres.

All of the towns have delineated places where displaced citizens can go—in most cases higher ground structures such as community centers and schools, though each situation may be different. Avista’s customer service call center is usually supplied with current information during storms and other emergencies: (800) 227-9187.

In the event of a failure at Hungry Horse dam, a large structure on the south fork of the Flathead River, a major tributary to the Clark Fork River, things would be more serious. Hungry Horse has three times the storage capacity of Lake Pend Oreille; it would impact all downstream dams, including Kerr, Thompson Falls, Noxon Rapids, Cabinet Gorge, and Albeni Falls. The front of the flood wave would reach Thompson Falls in 30 hours and Noxon Rapids in 36 hours; peak flows would occur within 55 to 60 hours, and could reach as high as 36,000 cubic feet per second. Debris would no doubt have major impacts on the downstream dams, even though Noxon Rapids shouldn’t be overtopped. In Noxon, the water would reach 15 feet above the town, but there would be plenty of time to evacuate the citizens. Lake Pend Oreille could rise by as much as ten feet. A Tabletop Exercise will be held by the Bureau of Reclamation, the agency that operates Hungry Horse Dam, this fall—hopefully downstream concerns will be addressed at that time.

“It’s a large amount of water,” says Ayres. “We need to be aware of what would happen downstream.”

Albeni Falls Dam, operated by the U.S. Army Corps of Engineers at the outlet of Lake Pend Oreille would respond to all of these scenarios by opening their spill gates, as necessary, to maintain the lake level for flood control. Campground and recreation sites would be evacuated immediately.

“We study EAPs all the time,” said Noxon Rapids Dam Operator Eddie Sue Judy, “but it is good to work through these scenarios that you just don’t know about ahead of time.”

Though these dam breach scenarios are, in reality, not likely to happen anytime soon, the key to preparedness is being proactive, and that is why these exercises are so important to the protection and survival of our local communities. It helps knowing that someone has been thinking ahead, that there is a protocol to follow, that there is hope in the event of a crisis.

“We’re the folks that make Avista do the EAPs,” says Tom Bobal of FERC. “By far this [exercise] gets a passing grade; I’m pretty sure they’d even get an A.”

These plans can also be used in the event of a natural disaster, flood, or the failure of one or more spillgates, similar to what recently happened at PPL Montana’s Hebgen Dam. Though the presence of a plan doesn’t mean that there are no kinks, at least you may rest assured knowing that it is in a constant state of improvement and that the powers that be are communicating and collaborating on how best to protect our special places.

“Although periodic exercises are required by FERC, the real reason we conduct the EAP exercises is for the benefit of both our (Avista) personnel and local emergency responders,” says Ayres. “After each exercise, we always discover some way to improve the EAP, even after all these years–as the old saying goes, you can only get better if you practice, practice, practice!”

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Kate Wilson Kate Wilson was a Project Journalist for Avista's Clark Fork Project. She has been interested in environmental issues since she was a youngster.

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EAP meeting Noxon Rapids Dam

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