PUD's diesel generators net additional megawatts, profit

EPHRATA — Grant County Public Utility District has increased power generation at Priest Rapids and Wanapum dams this summer by using the utility's 32-megawatt diesel generator farm near the Grant County International Airport for reserve power production.

The utility installed the 20 diesel generators, which are located along Randolph Road, in the spring of 2001 because of anticipated power shortages in the northwest and due to low-water conditions on the Columbia River.

So far this summer, without turning the diesel generators on, the utility district has been able to use the facility as its standby capacity and then generate more than 11,000 megawatt-hours of electricity at the dams, realizing a net value of more than $200,000.

By utilizing the diesel facility as reserve generation capacity for Priest Rapids and Wanapum dams, the utility is able to generate additional power through the two hydroelectric projects.

Power generating utilities are required to hold a certain amount of power generation back as reserve capacity. If a major power plant in the Northwest suddenly shut down, the reserve capacity at other power plants would quickly be called on to make up the shortfall.

In the past, the district has reserved capacity at the projects, resulting in lost generation from water spilling over the dams instead of traveling through the turbines.

"This year, elevated river flows have increased the level of total dissolved gas in the Columbia River and increased the amount of water spilled over both Priest Rapids and Wanapum dams for fish passage and reservoir control," said Joe Lukas, the district's assistant general manager. "The additional capacity realized at the Grant PUD diesel site partially mitigates for both of these issues in addition to providing a cost benefit to the utility."

Water plunging during spill events at seven dams along the Mid-Columbia River, along with sources upstream of the U.S. and Canada border, produce elevated levels of total dissolved gas in the water. Fish exposed to these elevated levels of gas may suffer "gas bubble trauma," which could increase mortality.

Grant County PUD spills water over Priest Rapids and Wanapum dams to meet juvenile fish passage goals established in a biological opinion by the National Oceanic and Atmospheric Administration Fisheries Service for the Priest Rapids Hydroelectric Project.

Additionally, the utility district increased spills in 2006 due to lack of powerhouse capacity to meet high river flows caused by rapidly melting snow pack.

"We operate with the belief that power generation and fish protection are compatible and sustainable," Lukas said. "In this instance, we were able to find a creative solution to solve two issues in the river while achieving a favorable outcome for Grant PUD and our ratepayer-owners."