A BRIDGE TOO FAR?
Behind Joburg’s broken bridges
The closure of the M2 freeway in Joburg is symptomatic of a wider problem: 94% of the city's bridges are in questionable condition
Joburg’s M2 motorway carries about 12,000 vehicles a day. At least, it did until February 28, when the city summarily shut the highway between the Crown Interchange and Maritzburg Street for urgent repairs, citing structural instability.
The chaos and confusion caused by the diversion of that traffic through the city is mirrored in the state of SA’s infrastructure — electricity, rail and roads. And bridges, it seems, have not escaped the general malaise.
According to the City of Joburg, only 6% of its 902 bridges are in good condition. That leaves 94% in a more questionable state — 16% in fair condition, 62% in poor condition and 16% in very poor condition, says city spokesperson Luyanda Mfeka. And mayor Herman Mashaba says 37 bridges in the city have collapsed in rainy seasons since 2013.
Those in the worst condition are in Soweto and areas such as Glenvista, Ormonde, City Deep, Benrose and Kensington, says Mfeka. But a recent Carte Blanche investigation also pointed to structural defects on the Queen Elizabeth and Harrison Street bridges in the inner city — ironically, bridges that are probably experiencing increased traffic volumes due to the M2 closure. "This is no longer bad, this is dangerous; this is emergency work," civil engineer Pieter Coetzee told the investigative journalism programme.
The city itself doesn’t explain what it means by "very poor" and "poor", and Chris Campbell, CEO of Consulting Engineers SA, says there is no definitive definition in engineering terms. However, "poor would mean the bridge condition is below acceptable limitations for guaranteed safety", he says. "Something needs to be done to remedy the situation before the condition gets to an unacceptable level where … [the bridge] would need to be closed permanently and replaced with a new structure."
How did the city find itself in this situation? According to Mfeka, it’s a combination of factors.
"Growth and development of the city has resulted in increased traffic, as well as increased flooding levels, resulting in bridges taking the strain of growth," he says.
Drastic measures had to be taken to mitigate the alarming state of our roads and bridgesLuyanda Mfeka
But the issue is also structural. He says most of the bridges have reached the end of their design life. This means major upgrades are required, which creates huge backlogs in bridge maintenance.
In the case of the M2, for example, Mfeka points to "concrete cancer", or alkali-silica reaction. Concrete is made up of cement and aggregate. The cement contains alkali, which may react with silica minerals in the aggregate, creating an alkali-silica gel that can take in water. When the pressure of the swelling gel is greater than the tensile pressure of the concrete, cracking occurs.
"The M2 bridge was inspected in 2014 as per scheduled inspection, and a resinous gel and white residue was identified which indicated that alkali-silica reaction had occurred," says Mfeka.
After continuous monitoring and assessment, the Joburg Roads Agency (JRA), which oversees the city’s bridges, realised that parts of the support structure had failed, affecting the stability of some bridges on the M2 motorway. The structural integrity of the concrete elements was severely reduced, so the city closed the highway.
As Campbell points out, though, it’s also an issue of maintenance — which is often deferred due to budget cuts. "There needs to be a full appreciation that [bridges are] not static structures that look after themselves. If you neglect to maintain them, they pose significant risk to public safety and would cost a lot of money to replace."
Bridges are affected by traffic wear and tear, weather and soil conditions. The concrete surface is also prone to damage, and exposed reinforcing steel may start corroding. "Much of Joburg is undermined," he says, "and though these structures are stable, there may be small settlement movements deep under the surface which affect the structures."
The city, too, picks up on the issue of maintenance. Mashaba, who took office after the local government elections in August 2016, says: "Since coming into office, I have been concerned about the huge infrastructure backlog which was allowed to accumulate in the city. Indeed, previous administrations allowed for a R6.5bn backlog in our bridge infrastructure."
However, former mayor Parks Tau accuses Mashaba’s administration of "peddling inaccurate information about the state of infrastructure, particularly bridges in the city".
Tau says that during his tenure the JRA had an infrastructure development programme that was responsible for all capital expenditure, including the rehabilitation, reconstruction, new construction and upgrades of various roads, bridges and storm-water infrastructure.
"In 2015/2016 alone the JRA had a total budget of R13bn to oversee the aforementioned concerns," he says. Though the entire budget was not used, he says the following projects were completed: 26km gravel-road upgrades in eight townships; resurfacing of 533km of lanes; rehabilitation and reconstruction of 16km of roads; under-bridge repairs, upgrades and rehabilitation; completion of the Naledi-Protea North bridge; upgrading of three bridges in Soweto; and the rehabilitation of the double-decker, Oxford and Federation bridges along the M1 freeway.
Tau says the JRA’s capital expenditure budget ran into billions of rands. With ongoing implementation of multiyear contracts, about R745m had been committed by 2016/2017. In addition, an implementation plan was developed to ensure that the balance of the budget was committed by December 31 2016.
"It is, therefore, important to note that planning for capital expenditure projects was done at least a year in advance to get projects ready for implementation at an appropriate time," says Tau. "This means that most, if not all, of the infrastructure work currently under way in the City of Joburg had already been provisioned for implementation before the new administration came into office."
Mfeka, for his part, says the city consistently allocates funds for the building and reconstruction of its road network.
"However, because of the service delivery backlog we inherited, drastic measures had to be taken to mitigate the alarming state of our roads and bridges."
Mashaba’s administration has set aside R1.2bn for the JRA from its capital budget, including R250m for road rehabilitation and reconstruction, says Mfeka. There’s an additional budget allocation of R181m specifically for bridge rehabilitation. And in its adjusted budget, the city allocated a further R135m for road reconstruction and rehabilitation.
"We are continually monitoring the state of all our assets, and when it is necessary for us to take the decision, such as the closure of the M2, we will do so in order to protect our infrastructure and our residents," Mfeka says.
He says the city also has a monitoring system in place, along with an infrastructure maintenance plan. This includes the Struman Bridge Management System, developed by the Council for Scientific & Industrial Research; a pavement management system; and Internet of Things sensors that collect data and use it to improve the management of the city’s resources. As part of its monitoring plan, the city’s bridges undergo visual inspection every five years, and more frequently if necessary.
Campbell, meanwhile, commends the city for its approach to the M2 problem.
"The current strategy being adopted is the correct one," he says. "First make sure the risk exposure to the public is limited. Then get competent technical advice on the remedial measures required and get experienced contractors to execute these remedial measures."
Thereafter, he says, the city needs to ensure that the remedial measures it has put in place are effective, and develop a long-term maintenance plan for these structures. And municipalities such as Joburg need to listen to their technical departments; their recommendations are meant to preserve the infrastructure for its design life span and, in doing so, protect the public.