The 2008 System Assessment found deficiencies in the Northern Mid-Columbia transmission system. The transmission system that delivers generation from Wells, Rocky Reach, and Rock Island dams is primarily 230-kV, with an underlying 115-kV system that provides load service. Contingencies that disrupt the 230-kV system at either Rocky Reach or Columbia substation, or the 115-kV system at Valhalla, McKenzie, or Columbia substations result in overloads. The underlying causes of these problems are a combination of load growth and the wide range of possible generation patterns. ColumbiaGrid has formed the Northern Mid-C Study Team to resolve these transmission issues.
A report was completed and the impacted utilities agreed on cost allocation of preferred plans. The plans are now being implemented.