Questions for the DMN on that Lewisville Dam Story


Finally got to the big dam story everyone is talking about. Good read! Lotsa drama. You can almost hear the scary music playing in the background, foretelling much damage and destruction. Highly enjoyed reading it.

Well, I enjoyed it the first time. The second time I looked it through, a few questions started to form. I wanted some supporting evidence and context that I suspect was not included because it would interrupt the excellent #longform #narrative. Especially after some light Googling. Those questions:

1. The only named Army Corps person in the story who supports its thesis — basically, that we’re all gonna die in a 65-foot wall of water if we don’t do something pronto — is a former employee. Did any current employees, even on deep background, support this theory?

2. The discovery of a sand boil leads the story. The story says, “[S]uch a ‘sand boil’ indicates that increasing seepage has created a passage under the base of the dam. If not stopped, it could lead to a rupture of the dam.” But that’s not true of all sand boils, is it? This Corps document suggests they’re very common, especially after area flooding. The story says there were rainstorms and flooding. Shouldn’t we note that sand boils are common in those conditions? And the document draws distinctions between sand boils that are common and mean very little and those that indicate seepage. And although the story says that a sand boil “indicates that excessive seepage is starting to erode soil material from the downstream slope or foundation of the dam through to the upstream side to form a pipe, or cavity, to the reservoir” (or “piping,” as it’s known), that’s not always true, right? For the reasons stated above. And a Corps official yesterday said the type of sand boil in Lewisville wasn’t the dangerous kind. From a story in yesterday’s Denton Record-Chronicle, we learn:

[FW Corps chief engineer guy Tim] MacAllister said sand boils and piping are two different issues. A sand boil is just water bubbling up out of the the ground like a spring, he said. Piping, on the other hand, is similar to a sand boil, but the water that bubbles up out of the ground is muddy and loaded with material from the dam, he explained. A dam safety training document used by the Corps of Engineers says, “Sand boils could indicate piping is occurring.”

But MacAllister said piping has not occurred at Lewisville Lake Dam.

“If we had piping taking place, that’s when I call these guys [the emergency response teams] and start evacuating,” he said.

3. The story also addressed another thing that bugged me. The lead photograph is very dramatic. But my light Googling, plus MacAllister himself in that document, says that it’s only a “surface slide,” which is very common. In fact, he says the Corps repairs “hundreds” of such slides a year. Was that context not important?

4. The story says the Corps lists the Lewisville Dam as “the eighth-most hazardous in the country.” That sounds very bad. Just wondering where that list is, since my Google-Fu was not strong enough to find it.

5. At first, I suspected that information was contained in one of the “internal documents” that the story mentions. But then I easily found this online, which seems to have a lot of the information discussed here. Information that the Corps didn’t want anyone to know — at least that’s what the DMN story suggests. And yet it’s online. In fact, the Corps guy in that Denton Record-Chronicle says that all of the information mentioned in the story has been posted online since said reports were finalized. Is that true? Then should that be made clear? Should the dramatic language be scaled back? Because the story plainly says, “The public hasn’t been told the full story about the Lewisville Dam.” But I’m trying to figure out what has been kept from the public. Little help?

6. The dam’s “high-hazard” status certainly hasn’t been kept from the public. Because although it seems as though this story exposes the dam’s classification — “Internal documents make clear the Corps has known about its ‘high risk of failure under an extreme event’ for many years” — that’s been part of the public record. This 2010 WFAA story says the Corps calls the dam “very high risk” and says they’re working on repair options. This DMN story from 2013 says the dam was one of 94 marked “very high risk” of failure, but that it was only then being looked at for repairs because the Corps first had to fix 13 dams classified as “urgent.” So, again, what was being hidden exactly? That Fort Worth is considering moving Lewisville Dam to the “urgent” category? Given that the 2013 story said repairs were slated to start in 2017-18, that would seem to be as much an accounting/priority/budgeting move as anything. Or maybe it’s nefarious evildoing? Just curious.

7. And why was your source (the ex-employee, not the fisherman) so surprised at how many people were in the path of water in the case of a catastrophic event? Dams are classified specifically by this: how many people would be in the water’s path in a worse-case scenario. That’s why this is a “high-hazard dam.” It has nothing to do with the structural integrity of the dam; the 1,600 or so dams in United States that are “high-hazard” are so designated only based on how many people are in the water’s path if the dam goes poof. (Scroll down to the chart that explains this.) So, downtown skyscrapers would all be classified “high-hazard” under such a policy, because if they collapsed a lot of people would die. Seems relevant, but maybe I’m wrong.

Those are just some questions I had after a second read. Still read great. Don’t want to suggest it isn’t. Just wondered if those questions could be answered. Thanks in advance.

UPDATE (12/18/15) You’ll find responses to these questions here.