RIASSUNTO
ABSTRACT
Westmar Consultants designed a mooring system for a large floating fish passage facility subject to 18.5 m water level fluctuations in the forebay of a deep-water reservoir in northwest Washington State, using OrcaFlex software developed for offshore oil rigs. The design included extensive numerical modeling to accommodate the large water level fluctuations and high wind and current loads on the floating structures and nets. This system replaced the original, which was installed during dam construction in 1959. The paper will describe this environmental project that uses state-of-the-art mooring design technology to enable salmon migration past dams and other river obstructions that do not otherwise allow for fish passage.
INTRODUCTION
This paper describes the need for and the design and implementation of a system for improving salmon migration on the Baker River. Baker Lake''s high water level variations, the close proximity of the structure to the dam, and the need to restrict the movement of the system under 1 in 50 year windstorm and flood flow conditions adds a high level of complexity to the design of the mooring system. For these reasons, the mooring system design utilized OrcaFlex, a state-of-the-art computer program from the offshore oil industry, and the mooring lines were manufactured from high-strength synthetic materials (Dyneema®) with low elasticity, combined with standard chains, anchors and winches.
Historical Perspective of Fish Capture at Upper Baker Dam
The Baker River Hydroelectric project is located near the town of Concrete in northwest Washington and is owned by Puget Sound Energy (PSE). The site location is shown in Fig. 1. The project consists of two dams: Upper Baker Dam and Lower Baker Dam.