Fish Protection Project
The goal of the Fish Protection Project was to test devices, including mercury lights and sonic devices, and then install them at SONGS Units 2 & 3 if they proved to be effective in reducing fish mortality.
SONGS was constructed with a highly effective fish protection system that included modifying the cooling water intake mechanism and an ingenious fish return system inside the plant.
The cooling water intake, which draws ocean water for plant cooling, minimizes capture of fish with a "velocity cap," which slows the flow of ocean water into the intake pipes, changes its direction from veritical to horizontal, and distributes the intake flow over a larger area. The result is lower flow velocities that most fish can easily detect and avoid.
Some fish are still drawn into the system, however. When these fish reach the onshore portion of the intake system, a complex arrangement of vanes and louvers attract the captured fish to a quiet corner of the intake structure.
In that corner, an elevator periodically lifts live fish out of the intake and dumps them into a flowing water return line to the ocean. The $200 million system reduces capture of fish by an estimated 90% (compared to an intake without a velocity cap) and returns approximately 75% of the fish that are captured back to the ocean.
The Fish Protection Project sought to reduce fish mortality even further by more effectively guiding fish away from hazards and increasing the number of fish returned unharmed by the system. SCE's goal was to save at least two additional tons of fish per year.
Over several years, SCE installed mercury vapor lights in the fish return elevators; developed a "fish chase" procedure to accelerate movement of fish out of the system; and tested various light and sonic stimuli to guide fish through the system.
Laboratory studies of light and sonic devices ultimately demonstrated that neither was effective in improving the fish return rate . The fish chase procedure's gradual adjustments in water temperature, however, has proven very successful, saving over 4 tons of fish per year, and has been adopted as standard procedure.
In October 2000, the California Coastal Commission affirmed that SONGS had satisfied the fish protection condition of its Coastal Development Permit.
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