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Bolivian Footbridge Wins 2013 Innovation in Sustainable Civil Engineering Award

2013 Innovation in Sustainable Civil Engineering Award

Chari Chari, Bolivia, Cable Supported Footbridge

 Chari Chari Bridge, Bolivia

Bolivia Chari Chari MapA new cable-supported pedestrian bridge in a remote area of the Andes in South America, built with local labor and materials, has been selected by ASCE as the winner of the 2013 Innovation in Sustainable Civil Engineering Award. The Chari Chari, Bolivia, Cable Supported Footbridge has vastly improved safety and enhanced the economy in a region where children and adults once had to walk miles out of their way each day to find a safe point to cross a dangerous, frequently flooded river.
 
The span was built with the assistance of Bridges to Prosperity, a group of engineers and other partners, many of whom are ASCE members, which seeks to open up impoverished regions in nearly impassable parts of the world by helping to construct pedestrian bridges. At nearly 520 feet long, the Chari Chari span is the longest bridge undertaken by B2P to date (as of fall 2013.)

The project was nominated by Richard Schrader, P.E., M.ASCE, president of RASchraderConsulting LLC, and a past chairman of Parsons Brinckerhoff Inc. In his nomination letter, here is how Schrader described the benefits achieved by the Bolivian bridge project:

Both furnishing the resources and creating an effective local organization comprised the goal of Bridges to Prosperity and its partners in constructing the Chari Chari Bolivia Cable-Supported Pedestrian Bridge. By providing safe access across the Rio Mizque, the bridge enables local communities in multiple ways. It opens up routes for trade and other economic purposes. It improves access to education and participation in social and governing activities. By constructing the bridge using a community contract, local labor and locally available materials B2P’s project utilized inherently sustainable resources. Maintenance will be accomplished by the Chari Chari community using local labor and materials, again representing a sustainable approach. This construction model can be replicated in other locations with similar conditions through B2P’s global footbridge training program.

The Rio Mizque runs through Chari Chari which is located within the Andes in the central Bolivian region of Omereque. Approximately 6,000 people inhabit the area in several surrounding communities. Located on steep hillsides, these communities were completely isolated for three to four months every year until the completion of the bridge. The Rio Mizque divides several communities from one another and from access to the main road and the larger regional town, and thereby limits local villagers’ access to essential needs.

On the Chari Chari side of the river is the primary school and a small room that functions as a clinic. The medical clinic, secondary school, markets and government offices are all located on the opposite side of the river from the town (and many miles away). The new bridge saves several hours of walking to make these trips when the water level is high. During the rainy season it is virtually impossible to cross the river, and even during the dry season the water runs as high as a child’s torso. There is no other crossing along the River Mizque for many miles in either direction. B2P, along with its local partner organization Mano a Mano Nuevo Mundo, offered to assist the communities with constructing a safe, reliable, year round crossing of the river in the form of a footbridge. B2P consulted with staff at Parsons Brinckerhoff to help identify the most feasible location for the crossing and to develop a design that was based on similarly designed, but here-to-fore shorter span, cable-supported bridges. Due to the challenging terrain, the optimum crossing location resulted in a bridge span of about 520 ft (160m).

While construction of cable-supported pedestrian bridges of shorter span lengths (in the 30m to 120m range) had been accomplished by B2P in over 100 communities in 16 countries around the world, the proposed Chari Chari span of 160m presented technical challenges that required support from PB engineers. The first innovation in sustainability at Chari Chari was to re-design the cable anchorages to better utilize existing subsurface conditions. The second innovation was to integrate the masonry towers into the anchorage design, thereby significantly reducing the excavation and concrete required for anchoring the structure while providing a high level of confidence in the anchorage design and construction. This change was intended to improve constructability allowing the use of common manual labor skills and thereby engaging more members of the community. The use of local labor makes the project replicable at other locations, a critical design criterion for B2P’s global vision and mission. Furthermore, as the span exceeded any previous B2P-constructed project, this design expanded the organization’s capacity to build and teach longer-span bridge construction, both locally and around the world.

What is also innovative is B2P’s community contract model. Rather than parachuting in an expatriate construction team and materials, B2P requires all benefiting and governing bodies to execute a contract to support and provide necessary labor and local materials. Thus B2P creates a local organizational model which is sustainable and replicable for additional bridges or other purposes. The need for cutting stone, placing concrete and furnishing wood for decking also creates local employment or micro business opportunities.

Before the Chari Chari bridge was completed, other nearby communities were also requesting to have a bridge constructed to benefit their villages. B2P’s approach to community development employs a replicable design that can be modified to use whatever local materials are available at these other sites. The innovation in the anchorage design will allow these other bridges to be constructed with less material and will allow for other longer span structures to be built where necessary in a safe and sustainable manner.

The Chari Chari Cable Supported Pedestrian Bridge now provides safe access across the Rio Mizque throughout the year, allowing children up and down the valley to come to school without attempting to wade through the river. It also provides safe access for people to take produce and other goods across the river to markets in nearby communities. By constructing the bridge with locally available labor and materials the approach to the project provides for a bridge in which the local community has ownership, pride and the knowledge that they can develop other similar projects.