St. Croix Crossing

St. Croix Crossing. . The St. Croix Crossing is an extradosed bridge design, described as a hybrid between a girder bridge and a cable- stayed bridge. The extradosed design was chosen because its signature qualities complement the natural attributes of the river valley. In an extradosed structure, the weight of the bridge and its users is supported by the piers and the external cables. , The foundations originate in sandstone up to 100 feet below the river bottom. The main river crossing has four equal spans of 600 feet, and the driving surface is about 110-150 feet above the river, shortest near the Minnesota shore and tallest near the Wisconsin shore. Each pier tower rises about 65 feet above the bridge deck. , The bridge deck was constructed using about 1,000 individual segments, each up to 18 feet tall and 48 feet wide. They were placed one at a time from each pier until they met at mid-span between the towers. The bridge opened to traffic in 2017.