Bowlin lost control at a right-hand bend, veering right then left and then leaving the road.
The summary said the van rolled violently over an open drain before smashing into a wall and coming to a stop upside-down.
Mr Gibbs, who was wearing a seatbelt, and Ms Walsh, who wasn't, died at the scene.
Bowlin's blood alcohol reading immediately following the crash was 113mg per 100 ml of blood. The legal limit is 80mg.
Bowlin's lawyer John Munro said he would appeal against the sentence.
Judge Bergseng said many of those who had provided references for Bowlin said the crash had left him a "significantly changed person".
He had stopped drinking and completed a defensive driving course and the Right Track driver behaviour programme.
Bowlin had no ongoing drug or alcohol issues, but had suffered ongoing post-traumatic stress disorder following the crash, he said.
However, Bowlin needed to be held accountable for his actions, Judge Bergseng said.
Victim impact statements provided by the families affected by the crash all spoke of the devastation that they had suffered, he said.
Given the fact two people had lost their lives as a result of his actions, a community-based sentence was not appropriate, Judge Bergseng said.