A series of alerts on Line 12 existed long before a section collapsed, leaving 26 dead and a hundred injured. The investigation folder of the Mexico City Prosecutor’s Office, to which EL PAÍS has had access, is a record of the path that this part of the metro took from its planning until its fall on May 3, 2021. In at least a dozen of reports, the errors that were made when the work was erected were recorded. The construction and supervision logs included in the documents indicated some failures that were later pointed out by some experts as the causes of the tragedy.
The work was built by a consortium made up of Civil Engineers and Associates (ICA), Alstom and Carso Infrastructure and Construction (CICSA), owned by magnate Carlos Slim. Grupo Carso has assured this newspaper that “each and every one of the observations that were recorded during the construction process were solved and received in accordance by the Metro Project.” This was the name given to the semi-autonomous body created to expand the transportation system and that came from the Ministry of Works of the Government of the capital. “When the observations were resolved, the process of delivery and reception of the work proceeded to the satisfaction of the Government of Mexico City,” added Carso.
One of the reports included in the investigation dates from December 3, 2010. On that date, an external supervision team reported errors in the design of Line 12 in a work log that had to be addressed at the construction site: “ It was detected that in the work of placing precast concrete tablets in the Zapotitlan-Nopalera intersection, the holes are being roughed up to widen them from 20 centimeters to 30 centimeters, this is due to the fact that the existing holes do not coincide with the metal beam to be able to fix the Nelson bolts,” the document reads. It also states: “You are told that all work is done at the expense and risk of the consortium until the required authorization is obtained.”
The expert opinion carried out by the Norwegian company Det Norske Veritas (DNV) pointed out as one of the faults that the construction had not respected the original design: “The logs showed various areas in which the work was carried out outside the approved designs.” This was recorded in a log dated December 20, 2010. “In the intersection Olivos-San Lorenzo [sección que colapsó] differences to the authorized project were observed in the beams of the Y track. Non-aligned girders are observed as marked by the aforementioned project, likewise adjustments are being made to the fixed and mobile supports”.
A supervisory team reported on June 24, 2010 that they had carried out laboratory tests on different materials and processes used in construction, and determined that they did not meet “the standard of comparison.” “Supervision is ordered to control and intervene on its part, in order to achieve the correction of deviations by the contractor consortium.” The statement also establishes that this measure will apply to all other deviations “that occur on a daily basis.” A month later, on July 28, 2010, the city’s Civil Works Construction Department indicated that there were “non-compliances related to the verification process of the metal beams of the elevated viaduct.”
In an inspection on December 18, 2009 at the Baysa plant, in charge of manufacturing the metal beams for Line 12, Proyecto Metro reported that “undermining in the manufacture of the 30-meter metal beams” was observed, “defective cuts in plates and an excess of welds in union of plates”. The document indicates that the manufacture of the structure requires greater attention from the construction company: “The Metro Project requires the consortium to take greater care in the manufacture of metal beams for the elevated section.”
On January 20, 2010, another visit was made to the Baysa plant in Lerma, State of Mexico, and given several irregularities detected in the welds of the beams, Proyecto Metro asked the consortium to “adjust” and “respect the authorized project” . Carso replies that it will conform to the tolerances determined by the United States bridge welding code. The welds ended up being one of the critical points in the construction indicated by the expert reports carried out by the Prosecutor’s Office. Grupo Carso has not recognized its responsibility for what happened, but has agreed to pay million-dollar reparation agreements and the complete rehabilitation of Line 12. Regarding the problems in the construction, the company has assured that its expert reports do not indicate that “it is a determining failure ”.
In another visit to the Baysa plant on February 25, 2010, more irregularities were detected in the webs and stiffeners of the beams, two elements that were later classified as part of the construction faults. The supervisory company IACSA visited the same plant on March 17, 2010 and reported that the inspection plan for the metal beams determined that it was not compatible with the one that had been delivered by the construction consortium. “The IACSA supervision indicates to the L-12 Consortium that it must adhere to the inspection and testing plan issued,” says the minutes of the visit. This newspaper consulted IACSA, but the company decided not to comment on the matter.
The lack of bolts, which was later pointed out as one of the causes, was also recorded in the logs. IACSA urged Carso on January 26, 2011 to place the corresponding number of bolts. “The consortium is required to place the missing bolts in the holes of the tablet as indicated in the project,” says the document. According to the minutes, they had already requested it before. Almost a month later, on February 21, 2011, the supervisor made a tour between the Olivos and Tezonco stations, the section that collapsed, and observed defects in the structure and lack of welding. “The consortium is required to make the corrections as soon as possible.”
In another document, dated February 4, 2011, the Subdirectorate of Civil Works C records that “it was observed that the three bolts were not being placed in each hole”, something that had been recorded in January. “Because the same anomaly continued, the personnel of the Carso consortium were once again informed by means of a minute of the observation, reiterating the placement of the three bolts in each hole”, since it was observed that in those holes there had been “placed two or one bolt. Grupo Carso has explained that it proved “that it bought all the bolts that were required for the work, that it received that number of bolts, the same amount was delivered to the specialized subcontractor for their installation, which finally charged for the installation of each one of those bolts. ”. Asked about the name of the company subcontracted for the work, the company spokesperson decided not to give details.
The videos before the collapse
A group of subway workers recorded in 2019, two years before the collapse, parts of the collapsed structure. They did it to complain about an excess of vibration in that area. In the images, which this newspaper accessed, you can see a metal column with the number 1027. In the background you can see a poster of the Cinemex movie theater chain. The employees of the transport system presented the videos to the authorities in order to carry out an inspection for security reasons.
At the end of that year, shortly before the covid-19 pandemic began, the Government hired a company to analyze the status of Line 12. There were no findings then, but the contracted company argued that its results were not correct. inconclusive due to a reduced sampling and a too short evaluation period, according to the latest DNV report. The metal column filmed by subway workers was right on the section that finally collapsed in 2021. Its remains can be seen in the images taken after the tragedy.
“That was expected”: the calls that night
The investigation folder also contains a series of transcripts of the calls made by subway workers the night Line 12 collapsed. The documents record the bewilderment of the employees of the Metro Collective System, who were slow to realize what had happened. Once they began to see the shocking images of the train split in half on a motorway, the calls registered comments that indicate that the failures of that section was a topic that they had previously discussed. In a conversation at 10:46 p.m., half an hour after the train crashed, one worker asks another if he knew what happened:
“Did you see what happened, bastard?” And one day we talked about it and well it happened wey, right?
—Yes, don’t suck.
—The problem is that, well, there are a lot of wounded
In another call, in this case recorded a few minutes after the previous one, at 10:51 p.m., two employees, one of them with a position as chief inspector of the station, comment:
—He fell, wow
—Yes, he came
-He went downstairs
—That was expected, remember that for a long time
“The fucking whale, right?”
-They were already in that fart and that’s why they were (it is not understood)
—No, but now it would be a lot of blowjob not to run to the fucking director [del metro, Florencia Serranía] Yet the [jefa de Gobierno, Claudia] Sheinbaum
-This is totally your responsibility, they say there are many dead
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