"We came across a document in a Freedom of Information Act that pointed out that the Corps of Engineers had changed the operating plan for Addicks and Barker reservoirs due to the highest level of risk," says Merz about the July 2010 internal memo.
In an attempt to get some answers, Merz wrote letters to Harris County officials, the mayor's office and the Corps of Engineers. She scored a meeting with a Corps staff member on a Tuesday, but three days before, the Corps' Galveston District Regulatory Branch okayed the building of Grand Parkway's $350 million Segment E.
Lisa Ramirez
After Evelyn Merz of the Houston Sierra Club stumbled upon the operational changes for Addicks and Barker, she scheduled a meeting with the Corps of Engineers. But before she could voice her concerns, the Corps gave approval to the continued construction of the Grand Parkway between Interstate 10 and Highway 290. Environmentalists say the future toll road, located west of Highway 6, will stress the shaky dams even more.
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Merz and Blackburn were appalled. They say that Segment E and the potential development will reduce Katy Prairie's ability to retain runoff during major storms. That's because water travels faster on a paved chunk of land than it does across the spongy soil of the Katy Prairie.
The Houston Sierra Club is trying to halt the construction of the Grand Parkway's Segment E, claiming that the prospective toll road might have a devastating impact nobody can imagine. "The long-term effects are significant of what we will face if we don't get the issue of runoff controlled and accounted for in those watersheds," says Merz.
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Because long-term improvements are at least five years away, the Corps' interim fix was to shave 975 years off of Addicks's and Barker's 1,000-year-flood capability. Currently, the reservoirs are permitted to hold only around 60,000 acre-feet of water, a level the reservoirs nearly reached during the April 2009 downpour.
Additionally, the Corps doubled the maximum amount of water that can be released downstream (from 2,000 cubic feet per second to 4,000 CFS). If reservoir water levels swell to 2,500 CFS, properties will start to flood. At 4,100 CFS, homes near West Beltway Bridge, North Wilcrest Drive and Chimney Rock Road could be marinating in floodwaters.
"In trying to protect the safety of the dams, which I have no problem with, they're saying better flooding a few homes than let the dams fail," says Dunbar. "They're pushing the envelope."
In the meantime, Dunbar believes that the Corps is crossing its fingers, hoping that a big storm doesn't sweep through the region.
"They or anybody can't tell you what the current risk of failure is because they don't know," says Dunbar. "They don't know if, during a ten-year event, if the water level rises to less than a 25-year event that it won't fail. They just don't know."
Dunbar says there's another issue to consider. During its risk analysis in 2009, the Corps discovered that the natural ground at the top of Addicks and Barker dams had subsided. If water started to spill over the top of the reservoirs — an unlikely but not impossible scenario — there might be hell to pay.
"When the reservoir fills up high enough, before it can spill over and out over the concrete part, it will start spilling out over the natural ground, which is dirt, which means it can start eroding right next to the concrete part of the dam," explains Dunbar. "It would create the same problem as if the concrete wasn't there."
If the reservoirs bubbled over with rainwater, Dunbar says, a 30-foot wall of craziness could be released.
"I've done a little bit of analysis and if the dam is full and it fails, you're getting flooding that's higher than a 500-year event. Depending upon where Barker dam fails — for example, on the north end — it's not going into Buffalo Bayou, it's going over land and maybe into White Oak." According to Dunbar, the Corps hasn't addressed the over-the-top spillage scenario.
While the Corps is scrambling to ink a deal so that they can start repairing Addicks and Barker dams, work is in progress to shore up Kentucky's Wolf Creek and Tennessee's Center Hill dams, which protect Nashville from Cumberland Lake's pent-up water. When it's complete, the project, which will help protect the Music City against a 200-mile flood, will cost an estimated $584 million. At press time, the Corps hadn't determined estimated repair costs to Addicks and Barker.
Along with filling the voids, Dunbar says that more needs to be done to prevent additional water from making its way to Addicks and Barker. One option would be to direct overflow to Cypress Creek, but that probably wouldn't work because the creek is plagued with its own flooding issues.
Instead, Dunbar says, "The best thing to do is to get more capacity within the reservoir and don't let more development occur upstream that would send more water to the watershed. Then let the water be retained in the Katy Prairie west of the Grand Parkway — you can almost use the Grand Parkway as a dam — and let it sit there and not let it get into the reservoir quickly."
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While Dunbar thinks that the Army Corps of Engineers is definitely addressing the complex situation from an engineering standpoint, he has an issue with the Corps' hush-hush strategy.
"I hear that the dams are not at risk of imminent failure and to an extent, I agree. 'Imminent' meaning it's about to fail. There's no water in the reservoir, so it's not going to fail if there's no water in the reservoir," says Dunbar before last week's storms. "The problem is that they're giving the public a false sense of 'Oh, don't worry, it's not a problem.' Well, it is a problem."