Water from rain swollen Chena River flooded Fairbanks 50 years ago this week, displacing thousands and causing $80 million in damage. The epic flood also had broader implications. It inspired creation of the national flood insurance program, and prompted federal construction of the Chena Flood Control project. The dam and levy system in North Pole regulate flow of the Chena during high water, to prevent another catastrophic flood.
One thing is very clear driving along the top of the Chena Flood control project Moose Creek dam and looking out its 3,000-acre impoundment basin: a lot of work when into it.
“This floodway alone, they had to clear timber with big CATs and dozers out there moving that material,” Chena Flood Control Project manager Tim Faevel said.
Faevel has been working at the Army Corps of Engineers project for the past 26 years. Largely completed in 1980, the system employs an 8-mile long gravel dam connected to a levy system that, during very high water, can channel the Chena’s flow water another 20 miles to the Tanana River by passing the cities of Fairbanks and North Pole. Faevel said that happened in the spring of 1992, the first real test of the system.
“The ’92 flood event really, I think, sealed the deal for a lot of these engineers that were involved at this,” Faevel said. “It worked. Everything, all the components worked.”
Faevel said avoided flood damage from that event and others have easily paid for the $200 million project. Looking down on the Chena River today it’s hard to imagine so much water.
“Probably only two or three feet deep right now,” Faevel said. “Doesn’t look like a lot. Salmon migrating upstream.”
Atop the central component of the dam, the “flood works” is a concrete structure spanning the 140 foot width of the Chena. There are large gates below us that can be incrementally closed to regulate the river’s flow toward Fairbanks.
“30-ton flood gates, there’s four of them. 25 by eight feet in size and so those are hydraulically lowered down into the bed of the river if we do have a flood event,” Faevel said as he waked through heavily secured doors to show the system. “So this is the outlet works control structure. It’s down in the gallery — we call this the gallery. And these numbers on the walls are the stations for operating each one of those four gates.”
Faevel described a carefully engineered process, employing numerous river gauges up and down stream, monitored during high water to precisely adjust the flood gates to keep the flow toward Fairbanks at 8,000 cubic feet per second.
”We’re operating 24 hours a day. During a flood event we’re making gate settings hourly, and it might be only three of four inches at a time, or something like that. Just to try to keep right there at that 8,000 mark.”
Faevel underscored that Chena Flood Control Project, which costs about $3 million a year to maintain and operate is simple.
“It’s durable. It’s lasted the test of time,” Faevel said. “And we continue to make improvements, small improvements along the way and change operations slightly. But for the most prat, we’ve done this the same way since 1980.”
That’s assuring even today, with the Chena flowing quietly through the open flood gates at under a thousand cubic feet per second, given that 50 years ago this month, the Chena’s flow peaked at an estimated at 74,000 CFS, enough to put most of Fairbanks underwater.