The Lumba bridge is wonderfully rebuilt thanks to the hard work of Tom Lawson, Clay Schwab, Kade Zongalinga and Kade’s team. This log bridge has been problematic for years and now there is a good stable, durable bridge in place thanks to these men and a donor in Tulsa, OK.
We first arrived on Saturday morning in time to see the team get the first beam across the gap using a temporary A frame in the middle of the stream. Manpower and smarts got it and all the rest of the beams across safely.
First beam going across the new bridge structure
Some explanations:
The bridge is a mass gravity structure. By design, it has large mass from which it gets its strength and stability. The base or foundations of the bridge are the gabions: wire mesh material making 1 cubic yard cubes that are filled with rock, which are in turn wired together. The mesh is made of galvanized wire, coated with PVC pipe. It is designed for salt water installations so will last a long time. Each support is made of 16 cubes – 2 layers of 8 – making the total dimensions 6′ wide x 12′ long x 6′ high.
The bridge beams, weighing up to a ton each, are cut from trees with a high density to resist deterioration. They are 12″ wide x 20″ high and 6 meters long. Four of the beams are bolted together with bolts 1-1/4″ diameter x 4′ long. The three sections of 4 beams were then tied together so the total width of the bridge is 12′. The gabions are also tied to the beams so that everything is tied together. Additional gabion screening was used on each side to make a flank and protect the sides from erosion. Very conservatively, Tom and Kade expect the bridge to last at least 10 years, most probably way over 20 years.
Completed bridge!
The pictures in this Facebook album tell the story.
