Washington State Patrol officials say Michael A. Robertson, 25, was driving his SUV west in the eastbound lanes of the freeway when he slammed head-on into the woman's Mazda near the Montlake exit at about 5:25 a.m. on April 4.
The victim, Morgan F. Williams, 58, of Seattle, was a 32-year employee of Eddie Bauer, and her ex-husband says she was on her way to work when the crash happened.
Robertson was charged with vehicular homicide in the case and pleaded guilty in King County Superior Court on June 21.
At that hearing, Robertson wiped away tears as the judge read from his signed confession that said: "I was impaired with the alcohol I consumed when I drove the wrong way on 520."
Investigators say Robertson was driving home after drinking with his friends in Seattle. He originally entered the freeway heading east toward Bellevue but apparently made a U-turn on the freeway and accelerated back toward Seattle, prosecutors said.
After the collision, firefighters had to cut the roof off of Williams' Mazda to rescue her after she was trapped in the mangled wreck. She was taken to Harborview Medical Center in critical condition, and later died of her injuries. Investigators say they found an empty bottle of whiskey in Robertson's front seat.
Robertson's sentence also includes a guilty plea to a DUI committed in Pierce County in December 2012.