Author(s): C. M. Johnson; R. T. Indri; F. G. Snider; S. M. Planck; K. F. De Lapp

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Keywords: Maintenance closure structure; Hydraulic loadings; Bulkhead; Cofferdam; Dewater; Gate rehabilitation

Abstract: Maintenance, remediation, and inspection of large spillway gates are best performed in a dry, dewatered state due to reduced overall cost, worker safety, and improved work quality. Provision for gate dewatering has become a key design consideration for new spillways. Unfortunately, many existing spillways were not originally constructed with gate dewatering capabilities. Therefore, maintenance and inspection work has often been scheduled during planned drawdowns or seasonally low reservoir levels. However, for operators of hydroelectric, flood control, water supply, and multi-purpose dams, artificial drawdowns can significantly impact operations, flood protection, downstream habitat, and revenue generation. Aging gates deteriorate and require significant maintenance, rehabilitation, and increased inspection. As dams age and gates deteriorate and require maintenance and rehabilitation, owners are increasingly seeking methods to dewater gate bays while maintaining operational pool levels using maintenance closure structures, such as bulkheads, stoplogs, cofferdams, and caissons. Designing these structures is challenging. This paper summarizes the findings from a worldwide review of the current state-of-the-practice for various types of maintenance closure structures in use for dewatering large spillway gates. Examples are provided for each maintenance closure type identified. The information, presented in this paper will be of benefit to those involved with spillways and dams, especially owners, engineers, and researchers seeking better, safer, inexpensive, and more durable maintenance closure structures that can be installed quickly.

DOI: https://doi.org/10.15142/T3400628160853

Year: 2016