When the wind farm — which began in May 2010 — becomes fully operational next spring, PSE will be the US's second-largest utility producer of wind power.
Lower Snake River is the latest of three PSE wind projects. The turbine contract is the largest onshore deal to be won by Siemens.
Jay Takeman, PSE's Environment Co-ordinator, said installation of the final turbines at the site had been delayed by gusty winds. "But that's behind us now," he said. "From this point forward, we'll take all the strong winds we can get."
According to Windpower Monthly's Windicator for July, Washington had a wind capacity of 2,428MW.