MOSUL, Iraq -- When a heavy downpour the morning of June 15, 2019, dumped even more water into the 32 billion gallons already in the reservoir of Iraq's Mosul Dam, it didn't faze the U.S. Army Corps of Engineers (USACE) staff, the Iraqi Ministry of Water Resources (MoWR) employees, or the Italian Contractors working inside and on top of the dam, because they knew that despite record rainfalls this past Winter, Mosul Dam was standing strong.In fact, the rain was a welcomed addition to the day because it cooled down the entire valley a few hours prior to the arrival of several dignitaries, including U.S. Ambassador to Iraq Matthew H. Tueller, Iraq Minister of Water Resources Jamal Abbas al-Adili, and Italian Ambassador to Iraq Bruno Pasquino, who were travelling to Mosul Dam to formally recognize the conclusion of the largest drilling and grouting project currently in the world, and to celebrate the full return of the drilling and grouting operations back to the Iraqis.Mosul Dam -- Iraq's largest dam and the fourth largest dam in the Middle East -- is located along the Tigris River some 250 miles from the country's capital of Baghdad. The dam is 371 feet tall and 2.1 miles long and throughout its 33-year history it has continued to provide water supply, irrigation, flood control, and hydropower for the people of Iraq. It is a well-designed and well-constructed dam that is unique in that it requires continuous maintenance grouting operations due to the water-soluble geology under the dam.According to Col. Philip M. Secrist III, USACE's Mosul Dam Task Force Commander, "Mosul Dam is effectively a construction project that never ends due to the scale of its maintenance drilling and grouting operations."In layman's terms, Mosul Dam was built on a geologic foundation with layers of gypsum, a water-soluble mineral that is widely mined and is used as the main ingredient in many forms of plaster, blackboard chalk and wallboard. Because the dam was constructed on a water-soluble foundation, it needs constant maintenance grouting so the dam doesn't collapse as the foundation erodes.The engineers building Mosul Dam recognized it would require a grout curtain (a mixture of cement, bentonite clay and water used to fill in the foundations' cracks and voids with a more stable material) to minimize the passage of water through the foundation. They constructed a grouting gallery at the base of the dam to reduce the challenges faced during the construction of the grout curtain and the required daily maintenance grouting.In 2014, when ISIS overran the dam, the maintenance grouting operations ceased. Operations at Mosul Dam were already suffering due to the instability in northern Iraq. The dam was quickly liberated and MoWR personnel return to work; however, ISIS had ransacked the dam, damaging valuable equipment, looting supplies, and leaving workers without the resources required to adequately conduct grouting operations. International concern for Mosul Dam's stability grew and the Government of Iraq (GoI) recognized the need for outside assistance. Speaking at the ceremony Ambassador Tueller said "A partnership was then formed between Iraq, the United States and Italy to initiate immediate repairs." USACE and Italian Contractor Trevi S.p.A. were brought onto what became the Mosul Dam Project.USACE, as a world leader in dam construction, operation, maintenance and repair, was requested to help with the stabilization and repair of the dam. The USACE Mosul Dam Task Force was formed and arrived in Iraq in September 2016 to serve as "the Engineer" for the Mosul Dam Project. Its job: Providing construction management, quality assurance, engineering and technical oversight and project management services in connection with a contract between the GoI and Trevi for maintenance grouting and rehabilitation of the bottom outlet of the Mosul Dam.Speaking about the joint endeavor and the work performed by the Mosul Dam Project Team, Col. Mark Quander, Commander of the Transatlantic District under which the MDTF fell, said "The U.S. Army Corps of Engineers Vision is 'Engineering solutions for our Nation's toughest challenges.' And sometimes that means helping other Nations solve their toughest challenges.That was case when USACE was called upon to assist Iraq with the technical and engineering challenges associated with Mosul Dam. But the project was bigger than just engineering and technical challenges. This project truly required the multinational collaboration among the Governments of Iraq, the United States and Italy. Without all three diplomatic teams working together to outline the project scope, secure the appropriate agreements, and lay out the funding requirements, this project would have taken much longer and not been nearly as successful."Quander said the engineering and technical complexities of Mosul Dam cannot be overstated. "The entire international team, to include USACE and our subcontractors, Trevi and their subcontractors, and the MoWR's staff skillfully navigated and achieved success on an unprecedented scale. We were able to complete our mission because we leveraged the talents of a broad array of subject matter experts combined with the MoWR's 30-plus years of experience working on Mosul Dam."Working together the team stabilized the dam's geologic foundation and improved the infrastructure needed to operate and maintain the dam. This three-year stabilization process included constructing three new grout mixing plants, installation of information technology networks -- including a state-of-the-art computerized grouting system called T-Grout, purchasing modern drilling and pressurized grouting equipment, and filling the warehouse to ensure it is properly stocked with repair parts and materials. The project also included an Integration Program whose purpose was building the capacity of MoWR staff. The program resulted in 250 MoWR workers being trained on the most recent technology/grouting processes, dam safety, GIS, Instrumentation, and Engineering. As a result, MoWR's Mosul Dam Project Office is now fully in the lead of improved maintenance grouting operations at Mosul Dam.Over 40,000 cubic meters of grout (enough to fill 40 Olympic size swimming pools) have been pumped into the foundation under the dam during the past three years. Since 1991, the MoWR had also placed 126,000 cubic meters of grout. Additionally, more than 700 instruments have been installed/replaced on the dam. Over 400 of these instruments are automated so near real-time measurements of the dam can be monitored for changes that inform the MoWR's dam safety professionals where to conduct future maintenance grouting.Through its partnership with the U.S. and Italian Governments, Iraq has received an instrumentation-informed, well-equipped and highly trained team, capable of maintaining a more stable Mosul Dam for the people of Iraq. "Mosul Dam will forever stand as an example of what nations working together for a common cause can accomplish to support Iraq's commitment to improving the lives of all its people," said Ambassador Tueller.