High risk' dams not likely to fail

Ground-penetrating radar revealed

By KAREN HASTINGS
CHRONICLE CORRESPONDENT
Curiosity mixed with a helping of alarm drew several dozen Katy-area and west Houston residents to public meetings in February, where the U.S. Army Corps of Engineers explained a new extremely high risk" label for Barker and Addicks dams.
The message from corps officials is that the dams, located north and south of Interstate 10 on Buffalo Bayou and its tributaries, are quite safe and not likely" to fail. They said the extremely high risk" label which resulted from a recent evaluation of dams nationwide is based mainly on their location 17 miles upstream of the country's fourth largest urban area.
Col. David C. Weston, who commands the corps' Galveston District, said the February hearings were meant to inform the public about safety issues surrounding the 60-year-old structures, to describe the repairs of foundation problems discovered last spring and to announce plans to replace or redesign the dams over the next two or three years.
The extremely high risk label" is unnerving, but it moves Addicks and Barker to the top of the national dam safety maintenance list, Weston told residents. Now we know (about safety concerns) and now we're on the priority list to fix our issues."
Although one downstream resident asked if he should keep his kayak handy, most of the residents who turned out for the hearing Feb. 18 at Wolfe Elementary School said they were just looking for information.
We've lived here 38 years and nothing has been said about the dam," said Karen Palfreyman, who lives in the Thornwood subdivision, a mile or two from Barker.
I was kind of curious," agreed Charles Sandel, who lives in the Fleetwood neighborhood. We thought they might have some plans."
Noel Rando, president of the Barkers Landing Home Owners Association, said he was a little disturbed" to hear that the dams were considered high risk, especially after the 11-plus inches of rain that fell in the area last April.
Realtor Jana Malkasian-Wick, who also lives in Thornwood, took officials to task for scaring the public.
That's kind of inflammatory," she told Weston. How much thought went into that terminology? I would say that has just about lowered our property values."
Weston countered that most residents know Barker and Addicks, which are dry most of the year, more as soccer fields and dog parks than as dams and reservoirs. George Bush, Bear Creek and Cullen parks are all within the two reservoirs.
After the devastating losses in Hurricane Katrina, the colonel said his agency has a new commitment to inform the public. We're not holding information anymore. We're laying it out there."
The February public information campaign follows the corps' discovery via ground-penetrating radar that 2- to 3-foot voids" existed in porous soil beneath the dams' outlet structures, which control water flow from upstream in the Katy area down Buffalo Bayou.
Weston said the voids are the result of prolonged pooling behind the horseshoe-shaped dams, which has become more common over the years as west Houston prairies have been paved over for Katy area development. The dams were not designed to hold back water for months on end, he said.
Emergency repairs last spring consisted of pumping polyurethane into the voids to prevent structural collapse above. This month, the corps awarded another contract to assess whether seepage is under control, and will install movement monitors this summer to further guard against structural failures.
To date we don't have any evidence that we're getting any seepage underneath the dam since that corrective action was taken," Weston said, adding that the corps also is preparing to add filters to prevent future voids.
Another area of concern, Weston said, are the ends of the dams, which allow high water to safely flow around during times of high water, rather than overtop the structures. Those spillways were reinforced with concrete in the late 1980s, he said.
With temporary repairs complete, the probability of failure drops even lower, Weston said. But the fact that the dams serve to protect the downstream metropolis of Houston means they likely never will be classified below high risk," he said.
Over the next two or three years, in what Weston described as an accelerated schedule," the corps will explore either replacing or redesigning the dams.
Construction likely would begin in early fiscal year 2013, Weston said. The Barker and Addicks dams were constructed in the 1930s after a series of punishing floods hit Houston. They were built to control the flow of water down the Buffalo Bayou that drained from the open rice fields and grassy prairies west of town.