Construction of the bridge was a far different story. While other bridges in the Dakota that are built across reservoirs were built before the reservoirs were full. This allowed the stream to be dammed and moved as needed to keep a majority of the construction on dry land. The Platte-Winner Bridge, however, was built several years after Lake Francis Case was full. This meant that piers would need to be built in water as deep as 180 feet.
The pier design was based on hallow concrete caissons. These caissons were cast on site. They were 4 feet in diameter and 5 inches thick, with lengths of up to 200 feet. Two were sunk for each pier. The caissons were filled with sand up to the river bottom level, then different types of concrete up to a level about 15 feet below the water line. From there to just above waterline, they were filled with rebar and concrete. A large concrete cap was then built across each pair of caissons. This would serve as ice protection. Two smaller columns were then built on top of the concrete caps. These columns would support the roadway, which would be about 30 feet above the concrete caps.
The pier construction was about half-finished when a problem was noticed. Several of the caissons split open. The reason was water inside the caissons froze, and pressure from the resulting ice split the concrete caissons. The problem is that there was not supposed to be any water in these caissons. The flaw was traced to the pier contractor improperly pouring the concrete. The contractor brought the concrete to the top of the caisson, and then let it drop to the bottom, which was as deep as 180 feet in places. What they did not realize is that concrete cannot be dropped in this manner. If wet concrete is dropped more than a few feet, it separates into its base materials. In the caissons, the concrete separated, with the sand and rock going to the bottom, and the water floating on top. The water turned to ice during the first cold snap.
A new contractor had to be brought in to fix the mess. The state started the process to recover funds from the old contractor. This ultimately lead to a nearly decade long lawsuit. The rest of the construction went as planned, though it was several years behind schedule. The bridge finally opened in 1966.
A powerful winter storm in 1997 pushed massive amounts of ice against the bridge piers, leading to damage to two of the piers. The state had to close the bridge for several months. Emergency repairs were made to stabilize the piers while a long term fix was designed. The long term fix was to build new caps on the piers that were bigger and stronger. At the same time, the existing caps were prepared by drilling holes in the caps and injecting a concrete grout that contained traces of Lithium. This was to fill any cracks and prevent any future damage from salts that may have gotten into the concrete.
The bridge was partly closed again in 2007 for inspection. The results of that inspection was that the deck needed some repairs. To do these repairs, a rubber material used as a seal coat would have to be removed. That work occupied much of the fall of 2007. Work was done to allow one lane of the bridge to remain open as much as possible. The photos below show the cones blocking the eastbound lane. The third photo shows one of the work crews, while the final photo shows a vehicle on the west end of the bridge waiting for the flagger to signal them that it is OK to cross.
The Platte-Winner Bridge was closed again starting July 2, 2008. This time, the bridge was OK, but the approach road on the west end of the bridge suffered a landslide during heavy rains in May. Heavy equipment had to be brought in to remove the unstable ground and built a new roadbed. The road was open to one-way travel over a gravel roadbed on July 18, 2008, after crews worked around the clock to fix the slide area. It will still take several weeks after the road is reopened to complete the grading and pave the highway.
