In order to promote safe and renewable energy hydroelectric dams throughout the United States require periodic inspections of their components and structures. Each season UCC is contracted by the power generation industry and/or independent consultant engineering firms to perform underwater investigations fulfilling FERC requirements. Dive inspections are performed utilizing the latest technology available and UCC inspection project managers work with the site engineers and owner/operators to develop a comprehensive report.
During the summer of 2014 UCC inspection crews reported a bulged area of sheet pile on a dam spillway apron during a scheduled inspection in the Northern Midwest. Following the report submittal UCC began working with the owner of the project to develop a repair plan. Repair methodologies, drawings and material specifications were created. UCC then developed a project budget and schedule. Mobilization commenced in November.
The project required divers to repair the existing spillway toe of the dam by first cutting down the sheet pile to specified elevations utilizing underwater burning equipment and techniques. Following the sheet pile cutting divers drilled a series of holes through the steel sheet pile into the existing concrete of the spillway for anchor installation. Threaded rod anchors were installed and epoxied into place to reinforce the sheet pile and prepare for the new grout to be placed underwater. Solid carbon steel bar stock was welded vertically into place at the sheet pile knuckles to reinforce the structure following AWS D3.6 standards. A geotextile membrane was installed at the base of the spillway toe and custom grout bags were filled and anchored into the riverbed for future scour protection. Grout was than pumped in the voided area between the existing sheet pile and spillway apron. Demobilization took place following a final inspection of the repair and a comprehensive construction report was created as a submittal for future reference.
Many challenges were successfully overcome including minimal water visibility, 32 ̊ water temperature, site location and outside air temperatures ranging from -10 to 20 degrees Fahrenheit. The project was completed the UCC way – excellent safety, on time and within budget. A multitude of cross talent from the Midwest Division was utilized from inspection, marine construction and welding diving crews.