Metro overpass collapse in Mexico City kills 24

A collapse of a subway overpass in Mexico City resulted in a least 24 deaths and more than 70 injuries.

The accident occurred around 10:25 p.m. on Monday, May 3rd, along Line 12 of the metro system, near the Olivos station in the working-class neighborhood of Tláhuac. Line 12, which opened to the public in 2012, extends from Mixcoac, in the west of Mexico City, to Tláhuac, in the southeast. It runs underground through the city center while it is elevated on concrete structures at the suburbs. The Mexico City metro system is considered to be among the world’s busiest, with around 4.6 million people using it, before the COVID-19 pandemic.

Rescue crews, including emergency workers, police and local citizens immediately started the efforts to free people trapped within the steel and concrete wreckage. Later in the same night, rescue efforts were temporarily suspended earlier due to concerns over the stability of the subway car, which was still hanging over the road, since the overpass was positioned about 5 meters above the road. Finally, on Tuesday, a crane lowered the train car to the ground, and four bodies were recovered.

Quickly after the accident, questions started amassing about the structural integrity of the transit system. Mexico City’s Mayor, Claudia Sheinbaum, stated that an initial analysis pointed to a “presumed structural failure,” while she indicated that a thorough and independent inquiry, involving a Norwegian consulting firm, will take place.

Nonetheless, reports have surfaced regarding the fact that the M7.1 2017 Puebla earthquake had already exposed structural defects in the elevated potion of Line 12, near the accident’s location. A 2017 report issued by the metro transit system showed that the base of one vertical column supporting the tracks had cracked, with spalling layers of concrete, due to lack of steel rebar stirrups. In 2017, authorities made some repairs to the columns by injecting resins, using carbon fiber, building a jacket of additional rebar around the base and pouring concrete around the collar. Authorities also found that one of the horizontal beams had come loose from its support at the top of a vertical. Authorities at the time added steel diagonal braces to the bottom of the beam.

Allegations of poor design and construction on the subway Line 12 had emerged soon after its completion. Pablo Montes, anti-corruption coordinator at the Mexican Institute for Competitiveness stated “all this history speaks to a lack of capacity from the moment of construction, and negligence in maintenance and supervision”.

source: BBC News