Of all the unrealistic expectations before the war, the one I was most unrealistic about was the pace of improvements to Iraq’s infrastructure. The Army Corps of Engineers would upgrade all the big stuff in a year or two, I thought — the electrical grid, oil capabilities, you name it. The fact that they’re talking now about a 65-foot wall of water set to descend on Mosul has an almost Old Testament aspect to it as a rebuke to that belief.

It’s not the U.S.’s fault — Saddam very shrewdly built the structure on material that dissolves when it makes contact with water — but it is the U.S.’s problem. And grave enough that they went to some lengths to keep it secret.

“In terms of internal erosion potential of the foundation, Mosul Dam is the most dangerous dam in the world,” the Army Corps concluded in September 2006, according to the report to be released Tuesday. “If a small problem [at] Mosul Dam occurs, failure is likely.”

The effort to prevent a failure of the dam has been complicated by behind-the-scenes wrangling between Iraqi and U.S. officials over the severity of the problem and how much money should be allocated to fix it. The Army Corps has recommended building a second dam downstream as a fail-safe measure, but Iraqi officials have rejected the proposal, arguing that it is unnecessary and too expensive.

The debate has taken place largely out of public view because both Iraqi and U.S. Embassy officials have refused to discuss the details of safety studies — commissioned by the U.S. government for at least $6 million — so as not to frighten Iraqi citizens. Portions of the draft report were read to The Washington Post by an Army Corps official who spoke on condition of anonymity because of the sensitivity of the matter. The Post also reviewed an Army Corps PowerPoint presentation on the dam…

“Mosul Dam is ‘unsafe’ in any definition,” an [ACE] PowerPoint presentation said. It added: “Condition continually degrading” and “Failure mode is credible.” Under a section labeled “Consequences of Failure,” it says: “Mass civilian fatalities.”

Ayoub said U.S. officials spoke in person about the dam in even more apocalyptic terms. “They went to the Ministry of Water Resources and told them that the dam could collapse any day,” he said.

The contractors working on it have apparently done next to nothing to fix it. Lawhawk points to the fact that the ACE assessments were completed last September as evidence that this really isn’t “news,” that the media’s just rolling it out now to dim the recently brightening narrative. What’ll dim the narrative is if that thing cracks and a trillion gallons of proof of the Iraqi and U.S. governments’ incompetence comes bearing down on half a million people. The WaPo story explicitly says that the ACE assessments weren’t released until today; that’s why it’s being reported now. And in fact, there have been new warnings since last September. Petraeus and Crocker themselves warned Maliki in May of this year that he might want to either get to work on it or start relocating Iraqis in the dam’s path. The minor logistical problem with that, if you believe WaPo, is that the flood would race through Mosul and possibly end up in Baghdad itself — with 15 feet of water in some areas.

The open question is why no one who knew how dire the situation is leaked it to force the public’s attention to it. It could be because they’re not really that concerned, but that contradicts the ACE evidence. It’s more likely that they’re so worried that they didn’t want to tip their hand and make it a target for jihadists looking for another strike in the mold of the Samarra shrine bombing, but a thousand times more spectacular. How they’re going to deal with that problem now, only Petraeus knows.