Iraq’s Most Dangerous Dam Still Operating, Under ISIS Control

— -- Employees at the Mosul Dam in Iraq, which is under the control of a brutal group of Islamist fighters, are still producing electricity and carrying out vital daily grouting operations, temporarily mitigating fears of a breach that could launch a 65-foot wall of water into the country's largest cities and send flood waters all the way to Baghdad.

The lead dam engineer and his team, along with their families, are still on site and continuing to operate the country’s largest dam, an Iraqi government official told ABC News. Though communications with the engineers have been difficult, the Iraqi Ministry of Water Resources is still in contact with the operating team.

The level of the water at the dam is being kept lower than normal in order to reduce the threat of a breach, even after taking into account evaporation from summer heat, officials said.

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The extremist group the Islamic State, or ISIS, released a video this week on YouTube showing its black banner flying above the dam. It wrested control of the dam away from the well-respected Kurdish Peshmerga troops last week, raising concerns among American officials.

“We are extremely concerned by this development,” State Department spokesman Michael Lavallee told ABC News at the time, “and we are coordinating with the Iraqi security forces and Kurdish Peshmerga commanders to develop options to mitigate the threat that this poses.”

Concerns remain about continued access to cement needed for the grouting process, but Iraqi government officials told ABC News that there should be three months-worth of cement stockpiles left on site.

Since ISIS took control of the dam and started closing in on Erbil, the capital of the Kurdish autonomous region where some American diplomats and military advisers are stationed, the United States military launched air strikes against the militants in support of Iraqi and Kurdish forces. The U.S. also air dropped relief aid to thousands of stranded members of the Yazidi minority who had fled ISIS persecution and sought refuge in the surrounding, arid mountains of Sinjar.

The threat posed by ISIS’ control over the dam is a severe one, according to U.S. government reports, U.S. officials and outside experts.

The Mosul Dam was constructed in the mid-1980s on what reports indicate was a terrible spot to build a two-mile-wide dam.

“Mosul Dam, the largest dam in Iraq, was constructed on a foundation of soluble soils that are continuously dissolving, resulting in the formation of cavities and voids underground that place the dam at risk for failure,” said an urgent letter sent from David Petraeus, then commanding general of the U.S. Army, and Ryan Crocker, then U.S. Ambassador to Iraq, to Iraqi Prime Minister Nouri al-Maliki in 2007.

The dam requires “extraordinary engineering measures” -- namely constant grouting operations -- to fill in the holes and “maintain the structural integrity and operating capability of the dam,” according to a U.S. Army Corps of Engineers (USACE) report from the same year.

For 30 years –- and through several periods of violent conflict -- the Iraqi government has managed to keep the dam upright by continuously pumping in literally tons of grout like an industrial version of the little Dutch boy, as a geotechnical expert who worked on the dam put it.

But the U.S. says any failure of the dam could be “catastrophic.”

“[T]he most severe impact of a dam failure would be [for] the City of Mosul, located 50 kilometers [31 miles] downstream of the dam,” Petraeus’ and Crocker’s 2007 letter said. “Assuming a worse [sic] case scenario, an instantaneous failure of Mosul Dam filled to its maximum operating level could result in a flood wave over 20 meters [65 feet] deep at the city of Mosul, which would result in a significant loss of life and property.”

Mosul is estimated to be home to more than 1.5 million people. Flood waters, albeit at a lower level, could reach all the way to Baghdad, more than 200 miles further down the Tigris, depending on the performance of another smaller dam further downriver.

A 2011 report written by a USACE official and published in Water Power magazine estimated failure “could lead to as many as 500,000 civilian deaths.”

State Department spokesperson Jen Psaki told reporters last week that the Mosul Dam “has been in the sights of [ISIS] since its offensive began in June to further threaten and terrorize the Iraqi people.”

In addition to flooding concerns, the dam is also a “key source” of power and water for the surrounding area -- making it a vital piece of infrastructure either way, another State Department official told ABC News last week. An American intelligence source agreed and said that ISIS's potential control over and exploitation of power and water is a focus of U.S. intelligence community.

So far though, Iraqi officials tell ABC News the workers at the dam have been able to pump water and produce electricity from one of two hydro-electric plants on site.

Prior to the ISIS takeover, a U.S. government official long-familiar with the dam said the possibility of the Iraqi government losing control of the structure was a scary one. ISIS may not want the dam to fail, considering it controls territory that would be flooded and the group could leverage its control over the water and power source, but the U.S. official said it would still be up to the jihadist group to keep the grouting going.