Independent Auditor Says Loss Of Bolts And Welding Quality Affected Metro 12 Accident In Mexico City

Kecelakaan Metro 12 di Mexico City, Meksiko. (Wikimedia Commons / Government of Mexico City)

JAKARTA - The deadly accident caused by the collapse of the Metro Mexico City flyover on May 3 was also influenced by the loss of a number of bolts on the flyover rail and the poor quality of the welding carried out, according to an independent auditor report released by the city government, Tuesday.

Twenty-six people died in the collapse of an overpass on the Metro Line 12, as the road below was filled with cars near Olivos Station, southeast of Mexico City on May 3.

In a second phase analysis report conducted by independent Norwegian auditors DNV, 180 pages thick, it was found that the loss of functional bolts in the beam span of the flyover caused the fatal incident.

This causes the bridge structure to 'do the job' as two independent girders to support the load, while the structure is not designed to be girders.

"This creates conditions that lead to distortion of the central transverse truss and the initiation and spread of fatigue cracks, which further reduces the capacity of the structure to support loads," the report said.

Not only that, the section of the overpass that collapsed was also in a 'destroyed condition' prior to the big 2017 earthquake, causing damage to the metro section, the report continued, citing poor welding practices as well as being observed by auditors.

The city government has begun work on rehabilitation of the track, and the report's findings will be shared with a technical advisory committee, said Jesus Esteva, head of Mexico City's public works department.

"In the next few days we will sign an agreement with the company. They will do the work," Esteva said, without adding further details.

The Metro was built by a consortium of Mexican ICA, Grupo Carso, a company controlled by the family of Mexican tycoon Carlos Slim, and French railroad maker Alstom SA.

Grupo Carso did not immediately comment on the report. Meanwhile, an ICA spokesperson did not immediately respond to a request for comment and a representative for Alstom could not immediately be reached

The collapse of the flyover put pressure on a close ally of Mexican President Andres Manuel Lopez Obrador, as well as on Slim, Latin America's richest man whose construction company was responsible for building part of the collapsed track.

"Carso will repair the channel at no cost to the government so it can reopen within a year," Mexican President Lopez Obrador said in June.

DNV was supposed to present a follow-up report on August 23, but asked for a two-week extension to complete its investigation. In a preliminary report, DNV found six flaws in the construction process, which contributed to the crash and noted inadequate bolts and defective structural support.