 Because this would have required sinking an anchorage pier in the deepest area of the Straits, the practicality of this design may have been questionable.A concrete causeway, approximately , extending from the northern shore, was constructed in shallow water from 1939 to 1941.However, a unique engineering challenge was created by the tremendous forces that operate against the base of the bridge, because the lakes freeze during the winter, causing large icebergs to place enormous stress on the bridge.