Smallwood Dam: Innovative Solutions for Phased Cofferdam Loading Challenges

A key issue arose from the phased cofferdam sequencing, which imposed additional loads on the existing center pier (which separates primary spillway bays 1 and 2) exceeding its original design capacities based on historical reinforcing drawings. While the center pier was adequate for original loading conditions, it was insufficient to withstand the increased forces during construction. Close collaboration between the contractor and engineering team led to an innovative, cost-effective solution: installing a 40’-0” (12.192m) tension anchor through the center pier down to the footings. This approach not only mitigated the load concerns but also avoided costly redesigns of the cofferdam bracing and prevented potential project delays. Additionally, to manage increased flow during phased construction, the contractor and design team worked together to also develop a siphon system capable of handling 70% of the historical flow capacity.