Costa Rican bridges vulnerable to earthquakes
In 1991, Costa Rica suffered its strongest earthquake to date. It was a sunny and calm April afternoon when the earth started to shake. Panic ensued, and when things stopped moving, many buildings, roads and bridges were left with cracks and structural damage.
Since then, more than 300 kilometers of roads have been repaired, and the government spent nearly ₡22 billion ($43 million) to fix damages.
But the country’s bridges haven’t fared so well.
One bridge that remains damaged from the quake 20 years ago spans the Chirripó River on Route 32 to the Caribbean coast, between Siquirres and Limón. If the bridge were to fail, the port city of Limón would be disconnected from the rest of the country. Supports on the bridge fell out of alignment, it lacks paint, rust is eating away parts of it, and one of the expansion joints is making the pavement crack on the bridge’s surface.
The Chirripó River Bridge is one of many Costa Rican bridges in bad condition. The government still considers it safe, but its structure has so many problems that another strong earthquake could render it useless.
“Bridges should get inspected every two years, since only those inspections will determine the maintenance work they need,” said Rolando Castillo, an engineer and head of the bridge department at the University of Costa Rica’s National Laboratory of Materials and Structural Models (Lanamme).
According to Castillo, Costa Rica has very few bridges that have been built to resist the force of earthquakes. Before 1971, no proper set of standards existed to establish best practices in terms of bridge construction in seismic zones. It wasn’t until the 1971 San Fernando Earthquake, which led to major bridges malfunctions in
the U.S., that engineers started worrying about seismic-resistant bridge construction.
Costa Rica’s most infamous bridge, the Virilla River Bridge on the General Cañas Highway, known as the “Platina” bridge for its shoddy construction, was not seismically designed. It was built to support 24-ton trucks, while today’s bridges are designed for 40-ton trucks.
In 2005, the administration of then-President Abel Pacheco asked the Japanese International Cooperation Agency (JICA) to send engineers to study Costa Rican bridges and suggest a better system to deal with structural problems.
In 2007, JICA delivered a report on the problems with the national bridge network and suggestions to improve the National Bridge System, a government agency.
JICA engineers studied 29 bridges across the country. With officials from the Ministry of Public Works and Transportation (MOPT), they selected the “ten priority bridges to restore after a comprehensive evaluation, according to the degree of damage and functional importance of [bridges’] structural components,” the report said. The Chirripó River Bridge on Route 32 was one of the priority bridges.
However, it wasn’t until this year – four years after the JICA report – that repairs and planning have begun on eight of the country’s 10 bridges named in the JICA report. “Unfortunately, the bid for the Chirripó River Bridge was too expensive for the ministry and the National Roadway Council (CONAVI),” Public Works Vice Minister María Lorena López said. The ministry will once again put the bridge repair contract up for bidding.
Bridges across the country are continuously presenting problems. In some cases, like the Virilla Bridge, shoddy materials and badly planned repairs are causing more problems.
“I believe that one of the problems with the Virilla Bridge comes from the fact that the structure was not thoroughly studied and analyzed before the works started,” Castillo said, adding that a new bridge over the Virilla River will likely have to be built. “Meanwhile, we will have to do short-term maintenance work,” she said.
Last week, the daily La Nación reported that the two-year-old Alajuelita Tiribí River Bridge in the hills south of San José is already showing signs of wear at one of its expansion joints.
Vice Minister López said she would not comment on the Alajuelita Bridge until MOPT officials submit a damage report. But Marco Rojas, CONAVI’s road maintenance director, told La Nación that the bridge is showing a 20-centimeter gap instead of a 10-cm one, as it was designed.
The continuous structural deficiencies in Costa Rica’s bridge system lead back to the National Bridge System. A small division within MOPT, the system’s workers lack training, and the agency is well short of enough staff to monitor the country’s 1,400 bridges, according to the JICA report.
In 2007, JICA officials created a software system that improved the method of inspecting and evaluating much-needed repairs across the country. So far, that system has never been used.
“It has been difficult to adopt this method, since it demanded a big change in the way things were being done, starting with the translation of the system,” López said.
López said Costa Rica has had trouble adapting its bridges to the changes in its own society. According to MOPT officials, the number of drivers on the road has increased by 500 percent in the last 10 years. “Unfortunately CONAVI’s budget didn’t increase with time, and they only receive 29 percent of the fuel tax that is meant to finance roadways and bridges,” López said. This year, at a cost of ₡700 million ($1.4 million), MOPT plans to repair 70 bridges. MOPT will finance the repairs with new debt.
On Thursday, La Nación reported that work on 31 of the bridges would likely be delayed because of a legal dispute over the bidding process.
Another problem is the rapid urbanization of the country. New urban constructions affect local water management, and water levels from rivers are affecting many bridges’ structures. “Even if we have to go into debt to fix these issues, work on roadways and bridges is considered an investment in the country. We understand that these improvements are a way of bringing more investment and economic activity to the country,” said López.
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