Best Project Energy/Industrial: Wanapum Dam Spillway Project
In late February 2014, a 2-in.-wide crack was discovered at a horizontal lift joint spanning a 65-ft-wide monolith at the Wanapum Dam Spillway that had resulted in about 1 and 1∕2 in. of differential movement across the lift joint. Owner Grant County Public Utility District and the Federal Energy Regulatory Commission began lowering the water level by 26 ft and quickly assembled the construction team.
In order to determine the extent and orientation of the crack, the team drilled through the spillway to capture data, which was then inserted into computer models developed to assess the behavior of the monolith. The models also identified potential failure modes and evaluated the effectiveness of potential remedies. Several models were used during the design process to gain a better understanding of the structure’s behavior—including response to thermal load conditions and installation of a dewatering bulkhead.