By the way, those dams only provide about half your power. While Hydro does provide the large majority of your power, the city doesn't own enough to supply the demand.
Seattle City Light's hydroelectric projects on the Skagit and Pend Oreille Rivers provide about half of the power customers need. The remainder comes from a mix of power sources, including long-term contracts with the Bonneville Power Administration (BPA) and others.
http://www.seattle.gov/light/FuelMix/
Bonneville Power Administration is a federal nonprofit agency.
I stand corrected on the secondary issue of whether most electric utilities are public or privately owned. I incorrectly extrapolated from the local to the national situation. But that is not the main issue here, that is NOT the point of the discussion. The issue is whether the electrical grid is vulnerable to human-generated EMP or solar flare degradation, and I will stand behind my opinion on that issue, which has been researched by panels of well-informed experts and has been deemed a potential threat to national security.