Spillway Gates and Dewatering Systems: Lessons Learned and Practical Solutions

Many spillway gates in the U.S. are now near or beyond the end of their original design life – requiring owners to re-evaluate the condition of their existing gates and find practical solutions to enhance their safety. Many owners of large, high-hazard dams choose to implement a gate replacement program and/or construct a dewatering system. Drawing upon recent gate replacement and dewatering system projects, this paper will share lessons learned and practical solutions for an efficient and proficient approach to the design and construction of new gates and dewatering systems.
These items will include:
•Enhanced gate detailing to prevent ponding and reduce member corrosion,
•A practical approach to fracture critical member and weld design,
•Lessons learned regarding material specifications and galvanic corrosion,
•Improved coating system solutions, and
•The evaluation of gate anchorage.
This paper will also emphasize how gate design guidelines have changed significantly since their original construction, resulting in more robust structures. We will summarize the design methodology presented in the United States Army Corp of Engineers (USACE) new hydraulic steel structure engineering manual and the changes from the preceding manual. Additionally, the paper will discuss the need for different types of dewatering systems, including lessons learned from an award-winning emergency stoplog deployment system. Ultimately, the paper should provide practical solutions to dam owners and design engineers to improve the reliability of gate designs and extend their service life while lowering the Operations and Maintenance (O&M) life cycle cost.