The dam of the Fort Peck hydroelectric project in Montana is the highest of six major dam facilities on the Missouri River. Flooding in 2011 caused a record release through the spillway, resulting in significant damage to the plunge pool and requiring emergency repairs and spillway rehabilitation. The Big Bend hydroelectric project in South Dakota, also on the Missouri River, experienced similar conditions during the flooding. As a subcontractor to J.F. Brennan, Barr provided inspections, structural and mechanical analysis, and design for gate repairs at both sites.
We performed visual structural inspections and nondestructive weld inspections for each gate as well as visual inspections of associated concrete surfaces and counterweights. Barr also conducted a finite-element analysis and designed a rehabilitation plan for each gate. To avoid budget overruns, Barr developed a gate-repair approach involving a tiered ranking system that included work such as crack repairs on fracture-critical members in upper tiers and weld undercut and underrun repairs on non-fracture-critical members in lower tiers. We recommended performing only the highest priority repairs initially and re-evaluating remaining tiers after half of the gates underwent repair. Ultimately, the approach was successful and resulted in a more appropriate use of funds.
In addition, Barr generated final repair plans and specifications for structural weld repairs, concrete surface repairs, ultrafine grout injection, and gate painting as well as replacement of structural steel sections, cathodic protection anodes, and gate seals.