Innovative Design for High Head Bulkhead Used in Slots With Multiple Openings

This paper describes the design process for bulkheads used for isolation at the San Francisco Public Utility Commission Hetch Hetchy Water & Power O’Shaughnessy Dam. Major design conditions included over 250 feet of head pressure at placement, one-of-a-kind positioning devices, uniquely designed and tested rubber seals to control leakage, and custom lifting beams. US Army Corps of Engineers manuals were the basis of design. 3D CAD Software was used for modeling of the geometry and to conduct motion studies and stress analysis of the components. The 3D modeling allowed the Owner’s engineering and operations staff to visualize the challenges of installation and to plan for their use of the bulkheads. The bulkheads were fabricated and tested at the facility in fall 2024, and the testing showed the lifting/retrieval and positioning devices were effective in placing the bulkheads accurately. Details will be described that can assist other engineers in the design of high-head bulkheads, positioning and lifting devices, seals, and other features which are not well described in available literature. A companion paper presented at the 2025 ASDSO Conference describes the seal design and testing in more detail.