Mosul Dam is built atop multiple layers of karstic limestone and gypsum that dissolves when exposed to water. This dissolution of the geologic formations under Mosul Dam has the potential to decrease the stability of the dam. Therefore, the dam’s designers included a 2.2 km gallery at the base of the dam to continuously inject grout (a mixture of cement, water and other materials) to fill voids created by the dissolution of gypsum. This grouting gallery is very unique feature in Mosul Dam’s design.
Over the past 30 years as part of the dam’s operations the Government of Iraq’s Ministry of Water Resources has been conducting grouting operations from this gallery to maintain Mosul Dam’s stability. Without effective, continuous grouting, there is an extremely high risk of failure. A large, uncontrolled release of the reservoir down the Tigris River Valley could lead to catastrophic loss of life, economic impact, and infrastructure damage.
For several weeks in July and August 2014, during the Battle of Mosul, Islamic State of Iraq (ISIS) terrorists held Mosul Dam and maintenance on the dam was deferred due to security concerns. Erosion and destabilization of the dam’s foundation caused by the stoppage of the grouting operations led the Government of Iraq (GoI) to sign a contract in March 2016 with Italian Company Trevi S.p.A. to provide maintenance grouting and rehabilitation of the bottom outlet of the Mosul Dam. The Italian government sent in troops from the Italian army’s Task Force Praesidium to provide security at the dam site.
The U.S. Army Corps of Engineers was hired by the GoI to act as “The Engineer” for the Mosul Dam project. Men and women of the USACE Mosul Dam Task Force began arriving at Mosul Dam in September 2016 to provide construction management, quality assurance, engineering and technical oversight and project management services in connection with the contract between Iraq and Trevi
USACE’s efforts were completely financed by the U.S. Government (USG) with a combination of Department of State (DoS) and Department of Defense (DoD) funds. USACE has had personnel on site to perform its Engineering function, augmented by a team of geotechnical engineers and geologists via a contract with AECOM and a team of engineers and construction quality assurance representatives via a contract with Versar, a local Iraqi engineering firm. In addition to the onsite presence USACE established a cadre of professionals to support the project from multiple USACE districts.
The stabilization and repair operation for the Mosul Dam has truly been a collaboration; a multinational partnership among the USG, GoI, and Italy. The overall partnership between the U.S. Government, the Italian Government, and the Government of Iraq was the backbone for the overall success. Without all three diplomatic teams working together to outline the scope of the project, secure the appropriate agreements for the timelines, and lay out the funding, this project would have taken much longer and not been nearly as successful.
The work performed on the dam stretched across three lines of effort:
- Improving the stability of Mosul Dam’s geologic foundation.
- Improving [or providing] the infrastructure needed to operate and maintain the dam– grout mixing plants, IT networks, modern drilling and pressurized grouting equipment, and warehouses stocked with repair parts and grout mix.
- Developing capacity by providing a trained and able workforce integrated across the spectrum of requirements, from dam safety, to technology, to maintenance.
Over 40,000 cubic meters of grout have been pumped into the geology under the dam during the past three years. In the previous 30+ years the MoWR has placed 63,000 cubic meters of grout. Additionally, more than 500 instruments have been installed/replaced on the dam. These instruments are automated so near real time measurements of the dam can be monitored for changes.
Operating and maintaining Mosul Dam has and continues to be the responsibility of the MoWR. The MoWR has a strong team of dedicated and capable professionals who have maintained the dam for more than 30 years with the equipment, technology and resources they had available. Through the MoWR-Trevi contract and USACE’s Engineering oversight, the MoWR has modern equipment and methods that allow its trained staff to identify and mitigate problems faster and more efficiently than in the past.
Through its partnership with the U.S. Government and Trevi, the Ministry of Water Resources has received an instrumentation-informed, well-equipped and highly trained MoWR team, capable of maintaining a more stable Mosul Dam for the people of Iraq.