Urban managers in Tehran, one of the most populated cities in the world, have been bending overbackwards to expand the city’s public transport networks, including the underground subway, to effectively meet the needs of the 13-million population.
The Tehran Urban and Suburban Railway Operation Company has plans to add another 100km to the overburdened subway system by September of next year.
However, the company’s negligence in efficiently implementing subway development projects over the years has raised concerns about project safety and possible subsidence risks. Some fatal accidents related to the metro company’s work in the ever-expanding city junctions have been reported in recent months, Fararu website reported.
A recent tunnel collapse in the southern Kianshahr district (district 15) last Thursday which killed four workers and a gas blast in a metro project site in the western Shahran (district 5) in June claiming the lives of two workers are two of the deadly mishaps.
Workers were excavating in the Shahran neighborhood when their drilling equipment hit an 18-inch gas pipeline leading to the huge explosion.
The exact cause of the Shahran accident is not yet known. However deputy mayor Seyed Jafar Tashakkori Hashemi claims that “the neighborhood’s old gas pipeline is largely to blame for the accident.”
However, two factors, namely hiring laborers (at less wages) and lack of proper attention to technical details, have been cited as the main causes of the recent incidents by urban development experts.
Land Subsidence
Land subsidence occurs frequently in the vicinity of metro project sites. While the bury-depth of metro tunnels in Tehran should be limited because of the special soil condition, it seems the metro projects are being implemented without enough attention to the technical details, says Mahdi Chamran, head of Tehran City Council (TCC). “The TCC will investigate the cause of the recent accidents and address the people’s concerns about the safety of the metro expansion projects.”
According to some experts, several subway tunnels in the capital pass through soft clay. “Such kind of clay has properties like large void ratio, high water content, poor permeability, high compressibility, and low shearing strength which lead to higher probability of land subsidence,” says Esmael Najjar, head of the Crisis Management Organization.
In the first week of September, a 3-meter-deep crater opened up in Payambar Street as a result of land subsidence. Residents say a drilling project underway near the street (for expansion of metro line 6) caused the accident. Three months before the accident, another land subsidence occurred in the same area.
While the TM claims that the accident was due to old, rusted and leaking water pipelines in the area, the managing director of Tehran Water and Wastewater Company Mohammad Parvaresh says, “There are two 500-meter-length and 150-meter-length water pipelines in the region and both are in good condition.”
In April 2015 a sinkhole opened up in the vicinity of the metro project site near Qiyam Square on the capital’s southern flank in District 12. Fifteen Afghan workers were injured.
Kianshahr Accident
Last Wednesday a tunnel collapsed in the southern Kianshahr district and killed 4 workers (3 Afghans and an Iranian) and six workers suffered severe injuries.
“We are waiting for courts to announce the causes behind the accident,” Abolfazl Qanaati, a Tehran councilor said on Saturday.
Deputy governor of Tehran, Qolamhossein Aram, says the accident(s) happen largely due to the negligence and carelessness of the contractors hired by the municipality. “Unfortunately, the contractors employ unqualified laborers for sensitive projects. Sensitive projects are projects where the human factor is as important as technical issues.”
Earlier, Maziar Hosseini, Tehran deputy mayor for traffic and transport said, “The Kianshahr accident was the result of human error.”
Work in Progress
Reports say 6,850 workers are working on Line 6 which has 27 stations along the 35km subway. It starts from Sulqan in northwest Tehran and ends at Dolat-Abad neighborhood in the southeast.
According to Habil Darvish, managing director of Tehran Metro Company construction of the 31km Line 7 also will be completed before the fiscal year is out in March 2017.
Extension of Line 1 to Imam Khomeini International Airport is also likely to be completed by that time.
Line 7 currently under construction connects the southeastern tip of Tehran to the northwestern districts and 14 trains will run on this line alone.
After completion of the projects, the subway system will have the capacity to carry up to 9 million passengers every day from the current 3 million.
The subway now comprises five operational lines (1, 2, 3, 4 and 5 – line 3 is not fully completed) with nearly 100 stations. Lines 6 and 7 are under construction.
