Preparing for the unthinkable

The chance of a catastrophic dam failure in the metro area is remote, but experts say officials should be ready. They aren't.

Jerd Smith, Rocky Mountain News

Published February 18, 2006 at midnight

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Emergency response officials would have only a few hours - and in some cases just a few minutes - to alert tens of thousands of metro-area residents if any one of several regional dams failed, an analysis by the Rocky Mountain News shows.

But Denver's Office of Emergency Management and other major agencies have yet to develop a strategy for moving people quickly in the face of an onrushing wall of water that could in places reach more than four stories tall.

"We don't have a mass evacuation plan in place yet," said Tracy Howard, Denver's director of emergency management.

The problem: Since Sept. 11, the metro area has spent most of its emergency preparedness money on equipment, medical care and manpower.

Planning for catastrophic floods or a dam break caused by a terrorist bomb hasn't been high on anyone's priority list, several officials said, because the chances of such an occurrence are slim.

However, because of the deadly problems with emergency response to hurricanes Katrina and Rita, cities nationwide are taking a new look at how they might respond if a variety of unthinkable events should happen.

In addition to terrorist attacks, there are rare natural scenarios under which a metro-area dam failure could occur:

• Some dams lie on inactive fault lines, including Barker Dam outside Nederland. But an earthquake could topple a dam.

• Heavy spring rains after ultra- deep mountain snowpacks - 150 percent of average - could fill reservoirs to capacity and threaten dams.

Jack Byers, head of the Colorado Office of Dam Safety, said the likelihood of failures at two of the largest metro-area dams - Chatfield and Cherry Creek - are extremely remote.

Both are flood control dams, which means that on any given day the amount of water they're holding back is just a fraction of the flood flows they're designed to contain.

And because they are earthen dams, they're not as vulnerable to a bomb attack as concrete dams are, Byers said.

"If a plane crashed into Cherry Creek (Dam), we would wind up with a burned spot on the dam. I suppose someone might try to drop a bunker-busting, 500-ton bomb on one of them, but the likelihood of being able to do that without the technical assistance of the U.S. Air Force is very far-removed," Byers said.

'A lot of work to do'

Nonetheless, because of the chaos, damage and death that resulted when New Orleans and a large segment of the Gulf Coast were caught ill-prepared by the hurricanes last fall, Colorado emergency response planners are trying to determine how to conduct mass evacuations for a number of different disasters, including torrents of water roaring down Cherry Creek or the South Platte River.

"We have a lot of work to do," said Denver's Tracy Howard.

Though the Colorado Office of Dam Safety requires that dam owners maintain emergency preparedness plans, a review of those plans shows that most include few details on what to do in the event of a disaster.

Most simply include phone numbers of people to call if problems develop; the physical warning signs of dam failures; and maps showing neighborhoods that could be inundated in the event of a flood or dam failure.

But the plans - the operating manuals local emergency officials are supposed to activate when disaster strikes - don't contain any information on how or where to evacuate people who are at risk, nor do the plans list safe havens.

Denver hopes to receive a Department of Homeland Security grant this year that will help it begin crafting a coordinated evacuation plan with other nearby cities. Last year, however, that request was rejected.

Howard said the repercussions from Katrina and Rita may mean better luck in getting money needed to formulate fast-acting evacuation strategies.

"Part of the problem is that it has to be coordinated with all the other communities or it won't work," Howard said.

And that's no small task. Nearly a dozen major dams lie within or above the metro area. All are owned by different agencies. Chatfield and Cherry Creek, for instance, are owned by the federal government. Barker Dam is owned by the city of Boulder, while Cheesman Dam is owned by Denver Water.

Who reports to whom in the event of an emergency isn't always clear, either. The state is responsible for keeping dams safe, but if a dam fails, it relies on local law enforcement agencies, and it has limited jurisdiction over federally owned dams.

The U.S. Army Corps of Engineers, which manages Chatfield, Cherry Creek and Bear Creek reservoirs in the south metro area, says it would report problems first to the Colorado Office of Emergency Management, which in turn would alert local law enforcement agencies, such as county sheriff's offices, to respond to disasters and begin moving people to safety.

But except in a multiday dam failure, there would be very little time to alert the public, a fact made evident in Colorado dozens of times with catastrophic flash floods.

A 1965 flood on the South Platte killed 28 people in a matter of hours, and, more recently, the 1997 Fort Collins flood killed five people and flooded the CSU campus, again in a matter of hours.

Boulder most vulnerable

If, to cite one scenario, Cherry Creek Dam failed suddenly, a wall of water would wash over I-225 almost immediately. Within an hour, water would race downstream (north) flooding the Cherry Creek Country Club.

Within four hours, the torrent would be 18 feet deep at Iliff Avenue, according to the Colorado Office of Dam Safety and inundation maps from the U.S. Army Corps of Engineers.

Warnings would have to be almost instantaneous, with evacuation plans activated within hours, and sometimes minutes, planners said.

Among metro-area cities, Boulder is considered the most vulnerable to a water-based disaster because its downtown sits at the confluence of two creeks and lies below a major water storage facility - Nederland's Barker Dam.

Barker sits at the top of Boulder Canyon. If the concrete structure failed, either because of a terrorist attack, extraordinary flooding or an earthquake, it would take about 35 minutes for a wall of water to race down the canyon and hit downtown Boulder, according to Larry Stern, the city's former manager of emergency response who now consults with the city and county.

"The chances of the whole dam going are minimal - probably 1 percent," Stern said.

Still, the speed of such a catastrophe renders traditional evacuation planning almost moot, said Justin Dombrowski, interim director of the Boulder Office of Emergency Management.

"We have to think tsunami, not Katrina," said Dombrowski, who was one of thousands of emergency officials who responded to Katrina and Rita last fall.

Until now, most dam emergency plans have centered on "phone trees," lists of phone numbers used by dam caretakers to alert emergency officials. That, in turn, is supposed to trigger a round of reverse 911 calls to residents within the flood inundation zone.

But reverse 911 calls take time to formulate and time to broadcast. Boulder County's system can send out 2,000 calls a minute. Dombrowski worries, however, that it could clog in a major disaster, and even if it did function properly, it could not give people enough detailed information, such as which evacuation routes to take.

Spreading the word

Last fall, a hazardous material spill outside Boulder triggered a reverse 911 alert, but residents later complained that they didn't know what to do or where to go.

As a result, Dombrowski is looking at posting evacuation routes on street signs and putting more flood safety information online in hopes of giving people more opportunities to help themselves quickly.

"Major dams occur above many communities in this state," Dombrowski said. "Giving people information can help them tie into what they should do to help themselves."

To date, information hasn't been widely available. Most residents have never seen flood inundation maps showing which areas would be covered with water and how quickly the surge would move in the event of a dam failure.

Increasingly, emergency response agencies are looking at whether such maps should be made widely available. One counterargument is that they might provide too much detail to terrorists and others intent on inflicting damage.

Since Katrina and Rita, however, experts say the public needs more information on the risks that exist, and that cash- strapped disaster agencies need to dust off their preparedness plans, rehearse them and empower residents to save themselves.

"The reality is that there's a presumption that our dams never fail, and because they don't fail, we become lackadaisical," said Larry Binder, a California law professor and expert on dam safety and emergency response.

Binder is among those who say that inundation maps should be made public and that evacuation routes be planned and posted.

"Because there has been no flooding for decades, a lot of homeowners have no idea what the inundation risks are," Binder said. "I would suggest that people who live in those zones need to know what the risks are.

"If a major dam bursts above a population area, the impact is huge. And if people don't know what to do they will all take the same highway and everyone will sit there for hours, just like they did during Rita."

smithj@RockyMountainNews.com or 303-892-5474

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