Exercising Safety:Tri-Lakes dams catch floodwaters while reducing flood risks
November 26, 2013
A stalled front brings record rainfall to the Front Range of the Colorado Rocky Mountains. The runoff brings a surge of water through canyons and foothills and into major population centers of central Colorado.
A Virtual Flood
But, this surge of water happened only in a virtual environment.
During the week of Aug. 19, several employees from the U.S. Army Corps of Engineers, Omaha District participated in a safety exercise focused on Cherry Creek Dam and Reservoir near Denver, Colo. -- or more to the point, in the middle of the Denver metropolitan area.
The Omaha District maintains multiple projects within the South Platte River basin. Among them are the Tri-Lakes projects consisting of three dams, Bear Creek, Cherry Creek and Chatfield dams, located on tributaries to the South Platte River, which runs through downtown Denver flowing north and then east through Nebraska.
Cherry Creek Dam is on Cherry Creek at its confluence with Cottonwood Creek, at the southeast edge of Denver. It was the first of the Tri-Lakes dams built to lower the risks to the Denver region from catastrophic South Platte River flooding that had plagued the area for more than 100 years. Chatfield Dam was the second dam constructed and is located southwest of Denver on the South Platte River at its confluence with Plum Creek. Bear Creek Dam was the last of the three dams. It is located on the southwest edge of suburban Lakewood at the confluence of Bear Creek and Turkey Creek.
The safety exercise was focused on Cherry Creek Dam because it has a Dam Safety Action Class rating which identifies a high urgency for action due to the potential for risk to a large population in the event of high operational releases or dam failure, even though the possibility of these events occurring is extraordinarily low. More than 200,000 people live within an area that, if Cherry Creek dam did not exist, would be prone to regular flooding.
"There are a variety of projects (dams) within the Omaha District's area of responsibility. Safety ratings aren't just about cubic yards of concrete or rolled earth used to build a dam, or the hundreds or thousands of acre-feet of water in the reservoirs behind the dams," said Natural Disaster Program Manager, Ryan Buckley. "When we look at these projects from a safety perspective, it is about improving public safety through reducing flooding risks for the people living near these projects, and with more people living within the vicinity of the dam, the more that risk factor increases."
Working together and against each other, the Tri-Lakes dams reduce flooding risks while the reservoirs and surrounding parks are part of the appeal that brings people to the area.
Army Engineer Regulation ER1110-2-1156 requires the Dam Safety office to conduct annual exercises such as a tabletop exercise, a drill or a functional exercise for significant and high hazard dams to help communicate the risks associated with living in the flood plain and near the dam.
"Because the large downstream population increases the risk factor for Cherry Creek, we chose to conduct a more formal exercise focused on Cherry Creek as an interim risk reduction measure," said Dave Sobczyk, Omaha District Dam Safety Program Manager.
The Dam Safety office enlisted the help of the Omaha District Emergency Management office to prepare and conduct the exercise.
"We typically host table top exercises but wanted something that would help us communicate the real risks associated with a large population in close proximity to the dam," said Kim Thomas, Chief of Emergency Management. "We learned from the flooding along the Missouri River in 2011, that people who live near a dam can become complacent with the reduced risks and forget that flooding cannot be eliminated."
The exercise, held in Lakewood, Colo., at the U.S. Army Corps of Engineers Risk Management Center brought together representatives from The City of Denver, Denver County, Denver Fire Department, Denver Police Department, Arapahoe County, Arapahoe County Sheriff's Department, the City of Greenwood Village, Cherry Creek State Park, Federal Emergency Management Agency, the National Weather Service, the Urban Drainage and Flood Control District and the U.S. Army Corps of Engineers with representatives from the Omaha District, the Northwestern Division and several Districts across the country.
Participants were taken through a high water scenario at Cherry Creek Dam, which was developed through the collaboration of Omaha District personnel representing offices such as Dam Safety, Emergency Management, and Water Management and the U.S. Army Corps of Engineers Readiness Support Center located in Mobile, Ala.
From discussing who is responsible for communicating what information and activity, to how to notify the public of concerns and managing evacuations, participants drew on a variety of experiences to help move through the exercise. Agencies from the Denver metropolitan area have previously worked together when Denver hosted the Democratic National Convention in 2012, dealing with blizzards and conducting evacuations during recent wild fires.
Tapping the USACE Readiness Support Center
Thomas is in the midst of an advanced Emergency Management degree program managed by the Readiness Support Center through George Washington University and developed by Dr. Steven Diaz with the center. Through this class, she learned about the center and the resources available through them for preparing the exercise.
The Readiness Support Center is part of the Mobile District; however, it serves the entire Corps.
"The RSC enables contingency responders by designing, implementing and continuously improving an educational curriculum responsive to the many requirements brought on by natural and manmade disasters and emergencies," said Nadia Taylor, Training and Exercise Manager.
The RSC provides the contingency responder training, tools and programs designed to credential and field a professional workforce, whether it is in Emergency Management, Risk Management or in a civil or military contingency.
The RSC makes every effort to meet the unique needs of each individual customer and request.
"Multimedia development is just one of our specialties," said Taylor. "We create videos, craft scenarios and simulations, create custom graphics and print products, and provide facilitation for live exercises. We also provide academically-sound expertise and comprehensive development of several distance learning programs for a wide variety of subjects."
The RSC frequently works with other Federal agencies, such as the Federal Emergency Management Agency and the U.S. Chamber of Commerce, in creating and delivering training and exercises. The RSC has also worked with the private sector through collaborative research and design initiatives. For example, the RSC worked with Microsoft to create simulations for their international offices and internal and external response organizations. Multi-scenario exercises (earthquake, flood, fire, hurricane, pandemic, and terrorist attack) were prepared and facilitated for Microsoft in Mexico, Turkey and at their Seattle offices.
The Cherry Creek Dam exercise is the 11th exercise the RSC has supported this year. Previous 2013 exercises included a flood event, hurricane exercises, a terrorist event and dam safety exercises for several U.S. Army Corps of Engineers Divisions and Districts and a tropical cyclone exercise for the U.S. Navy and the Independent State of Samoa.
The Corps and the agencies participating with the Omaha District in the Cherry Creek Dam safety exercise, recognize that risks exist and complacency or presuming that dams protect or prevent all flooding can be dangerous to public safety.
"Through the course of the exercise, we saw first-responders treating the scenario as a real-world situation and an opportunity to learn," said Buckley. "The participants wanted to understand how we (the Corps) respond to dam safety issues and their increased awareness of these risks will be beneficial as they ensure the proper plans are in place to help protect public safety."
Unfortunately, some of the first-responder participants saw a real-world scenario unfold less than 30 days later.
Through the latter half of September and into October, Federal, State and Local officials in Colorado were responding to damages caused by flooding which followed heavy rains that fell Sept. 11 and continued into Sept. 12.
The Tri-Lakes projects are located to the south of and upstream from where much of the rain fell. However, a large amount of rain fell in the foothills of the Bear Creek basin. The pool elevation at the Bear Creek reservoir rose several feet over the following days. At 4 a.m., Sept. 15, the reservoir pool elevation surpassed its previous record elevation of 5587.1 feet, which occurred in 1995 and peaked at a pool elevation of 5607.9 ft on Sept. 22.
Bear Creek Dam Halts Floodwaters
At Bear Creek Lake Park, campground facilities and park infrastructure including trails, parking lots and picnic areas became inundated with floodwaters from Bear Creek and Turkey Creek.
"Bear Creek Dam did what it's designed to do," said Fred Rios, Operations Project Manager for the Tri-Lakes Projects talking about the flooding at Bear Creek Lake Park. "Nothing can prevent flooding but the Bear Creek Dam helped reduce that risk to hundreds of homes located downstream," he added.
As the floodwaters receded from Bear Creek Lake, park patrons and volunteers who came to help clean up debris were able to see how the dam worked to reduce those risks.
"Hopefully, it also serves as a reminder to the public to have a plan," said Rios. "I pay attention to Winter Storm Warnings and Severe Storm conditions to protect my family. We need people to keep that in mind when living near a dam." When living on a reservoir or downstream from a dam, residents should have a plan for potentially high pool elevations or high water releases.