The floor beams for Puente Rio Baba are steel pipes hanging from the suspension cables. Timber stringers are staggered from side to side so that both ends of the stringers can be supported on the floor beams.
I believe that the villagers were responsible for supplying the timber used on Walter's bridge. After he completes his survey, he provides the villagers with a list of what he needs and if it's not there when he returns, he just drives on to the next village and the next bridge project.
Building these bridges is a communal process. It is quite common for villagers to have heated debates about the pros and cons of building a bridge. A firm commitment from the villagers is needed before Walter will begin a project. Because, the river can become dangerous or impassable during the rainy season, the standard of living for most people in the village will improve once they are able to safely cross the river.
Ecuador's Bridges: Puente Rio Baba (4) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.