The Big Drift is the result of winter snows and blowing winds. Located east of the Continental Divide along the Going-to-the-Sun Road, this snowdrift can accumulate over 100 feet deep. Winds push snow up and over the Continental Divide onto a thin ridge of rock (that was formed by glaciers), which is known as the Garden Wall.
In the spring, a helicopter surveys the area in preparation for snow removal of Going-to-the-Sun Road. They use GPS and visual signs to identify potential avalanche risks and to help locate the road, which is completely hidden by snow.
Usually in early April, crews begin removing snow working from both ends of the 53 mile road. The Big Drift is typically reached sometime in late May, and it can take a month to clear that one mile stretch of road. The crews use explosives and front-end loaders to remove the snow by pushing it over the cliff or hauling it away in dump trucks. Plowing the entire stretch of road takes about ten weeks. Logan Pass can usually be accessed by passenger vehicles in early to mid June. In 2006, the road was not open to traffic until June 23rd.
Due to smaller crews during WWII, Sun Road was not opened until July 10th in 1943. In later years, the latest opening of Sun Road occurred on June 28, 2002, as a result of deep snows that fell through May and early June. The earliest opening ever was in 1987, when the road was opened on May 16.
* Picture compliments of Wikipedia