[8] Grant PUD's New Turbine Passes Fish Test

Grant County PUD has successfully tested fish passage through its new turbine, an advanced design that produces more electricity while letting nearly 98 percent of juvenile salmon survive the trip through the turbine bay. The PUD says survival rates "generally" exceed those of existing turbines at Wanapum Dam, while generating 14 percent more power and boosting water efficiency by 3 percent.

With 70 percent of the migrating fish using the turbines to pass the dam, the PUD had to prove to the Federal Energy Regulatory Commission that the new unit was at least as successful at passing fish as the older turbines before the feds would approve replacement of the other nine units at the dam.

The district expects to replace all 10 turbines over an eight-year period and boost power output by 900 to 1100 MW at a cost of about $150 million.

But fish survival in the old turbines wasn't that bad. According to the evaluation released in August by Columbia Basin Research and Normandeau Associates, survival actually averaged a little higher in the old turbine than in the new one, 97.5 percent versus 96.95 percent.

However, researchers said the survival of fish higher in the water column was a bit better in the new turbine. After weighting for vertical distribution, overall passage survival in the new turbine was 97.82 percent, compared to 97.71 percent in the old one. Survival of fish that entered the new turbine lower in the water column was actually a little worse than in the old turbine, but the report said, "passage survival through the new turbine was not significantly lower than through the existing unit."

Survival of yearling chinook through the Wanapum spillway has generally been found to be less than 90 percent. An agreement between the utility and federal, state and environmental agencies requires 43 percent of the spring flow at Wanapum and 61 percent at Priest Rapids be spilled during the smolt migration period.

Grant has to comply with a biological opinion that calls for reaching a 93-percent juvenile project (dam and reservoir) survival standard by 2010. A 2004 study found yearling chinook survived, on average about 86 percent through both dams and reservoirs. To improve juvenile fish survival, the utility has developed programs to reduce predation by northern pikeminnow and birds. -B. R.

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