The Tulsa area’s nearly 20-mile levee system is among the top 5 percent of levees in the nation that have drawn the concern of the U.S. Army Corps of Engineers because of the potential high risks associated with them, officials said last week.
To help address those concerns, the Corps has chosen the Tulsa levee system — along with eight others from around the nation — to be part of a risk-assessment pilot program to identify problems in the levees and prioritize rehabilitation projects.
“The idea is that we identify from a risk standpoint what we can expose to make the biggest impact,” said Jaime Watts, levee safety program manager for the Corps’ Tulsa District.
The Drainage District 12 levee stretches approximately 20 miles from Sand Springs into Tulsa and protects an estimated $2.2 billion worth of infrastructure.
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In 2008, it received an “unacceptable” rating from the Corps of Engineers. An unacceptable rating indicates that a levee has one or more deficiencies that could prevent it from functioning as designed. The finding was made after federal standards were changed in the wake of Hurricane Katrina. The rating did not mean the levee was unsafe, but it did leave the levee district ineligible for federal rehabilitation assistance should the levee be damaged in a flood or significant storm. The Corps of Engineers announced in 2011 that Drainage District 12 had been accepted into the System-Wide Improvement Framework program, which allowed the levee district to again receive federal rehabilitation assistance.
However, continued eligibility is contingent upon the district’s ability to bring the levees into full compliance with Corps standards. To be in full compliance, the drainage district must be able to show that the levee has the capacity to handle 350,000 cubic feet of water per second.
To be certified by the Federal Emergency Management Agency, the levee must be able to handle a 100-year flood. For the Arkansas River, that is 205,000 cubic feet of water per second.
“If your levee is not certified, they act as if it is not even there, and they map the flood plain all the way back” beyond the levee, said Paul Zachary, director of the city’s Engineering Services Department.
The drainage district is a separate government entity that maintains and operates the levee system.
The study is expected to begin this summer and take approximately a year.
Todd Kilpatrick, levee commissioner for Drainage District 12, said the fact that Tulsa’s levee system has been selected to be part of the pilot program “was basically affirmation from the Corps of how dangerous this levee is.”
Time has taken its toll on the levee system, Kilpatrick said, noting that the system of grass embankments and drains inside them is 70 years old.
“The relief wells and toe drains (inside the levees) — they are clay pipes,” Kilpatrick said, adding that “their useful life is over.”
When water rises on the levees, Kilpatrick said, water tries to push through to the other side.
“What the relief wells do is relieve the pressure by sending the water into the toe drains that release it to the pump stations that pump water back into the river,” Kilpatrick said.
Last year Tulsans approved $3.4 million in funding for the levees as part of the Improve Our Tulsa capital improvements package.
Approximately $300,000 has been designate to help fund a separate $1 million assessment of the structural integrity of the levee system. Tulsa County, Sand Springs and Drainage District 12 are also helping pay for the study.
Bill Robison, the city’s lead storm water engineer, said the Corps will be able to use the structural assessment in its risk assessment.
“We are going to look at it in a little more detail and come up with some actual projects to address the deficiencies,” he said.
The next step in the process will be to repair the levee to ensure that it can again be certified by the Federal Emergency Management Agency.
Kilpatrick and Zachary said that until the studies are done, it is impossible to estimate how much it will cost to bring the levee up to Corps, FEMA and USACE standards.
“Hopefully within a year we’ll have some kind of quantified estimate,” Kilpatrick said.
Kevin Canfield 918-581-8313
