Timber bridges installed by Alaska Highway builders speeding through the subarctic region in the summer of 1942 survived their first winter. Well… some of them survived. The soldiers, forced to add building timber bridges to their rapidly expanding skill set, learned speed not quality.
North of Whitehorse, just forty soldiers built Jo-Jo River Bridge, forty five feet long, sixteen feet wide and about twelve feet above the river in ten hours.
The biggest rivers forced the soldiers to make do with barges. And they channeled thousands of small streams through culverts. But by the end of the summer hundreds of timber bridges spanned streams and rivers from Dawson Creek all the way to Big Delta.
The soldiers felled trees and sawed them into logs. They built enclosures, dragged them into the icy water and placed them to form two parallel lines across the river. In each container they placed a vertical timber, packing the container full of rocks to hold the timber upright.
Atop the vertical timbers they constructed a flat platform of logs, and when a D8 Dozer drove out onto the platform it groaned and shook a bit. But it carried the weight. Bridge builders turned back into road builders and moved on to the next river.
Then came winter—and mushroom ice.
Even the bitterest of bitter cold does not form ice in a swift moving current. Water continues to flow. But ice forms along the sides and the bottom of the flow, gradually compressing its channel, raising the water level. Ultimately water flows over and around a bridge. Great mounds of ice form and grow over the bridge and its approaches. In the spring, melting ice cracks and breaks up and moves. In 1943 moving mushroom ice often took its timber bridge along for the ride.
No matter. Civilians from the Public Roads Administration would be back in the summer of 1943 upgrading the bridges along with the Highway.
fascinating!
Thank you