Portland General Electric agreed to sell stakes in its hydroelectric system over four decades to American Indian tribes that now lease the dam properties to the utility. It plans to sell a third of the 408 MW Pelton Round Butte system to the Confederated Tribes of the Warm Springs next year, up to 49.9 percent by 2021 and an option for a controlling stake in 2037. The tribes would pay for the system over 50 years by selling their share of the electricity to Portland General or other utilities at