The driver, identified previously as Isaiah Moreno of Humble, Texas, had a blood alcohol content of 0.20, Idaho State Police said in a statement. The limit is 0.08.
“This tragedy should be a wake-up call,” police Capt. Chris Weadick said. “No one plans to cause a crash or take a life when they get behind the wheel, but choices have consequences.”
Investigators determined that the Dodge Ram driven by Moreno crossed the center line and collided with the Mercedes van, which was carrying 14 people, in the May 1 crash. Both vehicles caught fire.
Moreno and six people from China, Italy and California were killed. Survivors were taken to nearby hospitals with injuries.
The highway where the crash happened south of West Yellowstone, Montana, is a route between Yellowstone and the Grand Tetons that is open in the spring before a north-south route is plowed and the park fully opens for summer.
Yellowstone is one of the country's largest national parks and draws millions of visitors each year.