Fort Smith, Ark. –
The 86th Engineer Dive Detachment, Special Troops Battalion, 7th Sustainment Brigade, received an initial inquiry in March from the U.S. Army Corps of Engineers, Little Rock District, requesting support to service one of its hydroelectric dams on the Arkansas River.
The Army's engineer divers jump at training opportunities such as this and strive to support USACE sites all over the United States. Utilizing jobs from USACE as a resource to train on unit capabilities provides the equally beneficial aspect of a threatening environment that no artificial training evolution can imitate. Fresh off a five-week mobilization to the USACE Portland District, a mission involving extensive underwater construction support to eight hydroelectric dams throughout Oregon and Washington, the engineer divers of the 86th embraced another opportunity to support USACE.
In early June after months of preparation, the 86th mobilized 13 divers and three equipment containers to Fort Smith, Ark.., for three weeks in support of the USACE Little Rock District. The scope of work required pumping more than 300 cubic yards of mud out of a hydroelectric turbine intake 70 feet below the surface. In order to accomplish the mission, divers would have to conduct an initial engineer reconnaissance of both the upstream and downstream sides of the dam.
The intake and outtake are massive shafts that, when open, move millions of gallons of water per second in order to spin the turbine and produce power. In order to begin repairs, the hydroelectric unit's shaft needed to be dewatered by lowering gates on both sides of the turbine with the ultimate goal of sealing and dewatering the unit.
Upon arrival at the job site, initial underwater inspections revealed that much more debris filled the shaft than initially suggested. These initial inspections served as a challenging deterrent to the mission's desired end state. However, in the spirit of the Engineer branch motto, "Essayons!" (Let us try) the 86th elected to drive on with the mission.
The team conducted numerous daily dives averaging 100-minute dives 60 to 80 feet below the surface. The unit's dive supervisors benefited from the experience of supervising in-water decompression dives which require careful management of the diver's time and decompression schedules. Equally important to the training value of the mission were the lessons learned by the divers in operating and staging a large pump underwater.
In order to clear the gate slot areas of the shaft, the 86th utilized the largest possible pump that could be safely operated by a pair of working divers. Normally this pump is used in the Gulf of Mexico with the purpose of salvaging sunken drilling equipment. The pump had to be positioned with a crane and then inspected by the divers.
After the divers confirmed the pump was properly staged on the riverbed, they proceeded to hoist extremely heavy hose out to the mouth of the shaft. Once properly positioned with the end of the hose buried in the debris, the divers notified the dive station to switch the pump on and began the arduous process of dragging the pump back and forth, sucking up as much debris as possible in their allotted dive time. At 3,700 gallons per minute of suction power, the pump proved to be an extremely effective tool for clearing the shaft.
After three long weeks and more than 2,000 minutes of working dive time, the 86th safely returned to Fort Eustis. A substantial amount of material was successfully pumped out of the turbine shaft and the way ahead for the USACE Little Rock District's refurbishment project remains clear. The training value offered by projects such as these cannot be overemphasized in its importance of professionally developing the next generation of the Army's underwater engineers.