An event that develops over 4-5 days and that apparently is recurring in certain South American regions, could give place to following comments:
Knowledge of the local environment
The design of a bridge implies – we take this for granted – knowledge of the region’s hydrology including a list of the river’s tributaries and its flow rate, historical statistics of the maximum water levels, return period of river swellings etc. Taking into account that “riadas” is a known phenomenon in the region – like the “huaicos” in the Andean countries – a professional risk inspection before the rainy season could have pointed out at this special feature.
Design / Subcontractors
Those responsible for the design of the auxiliary bridge – made totally out of steel – did not consider the massive arrival of dragged material / logs while defining the span of the auxiliary bridge’s pillars. Here we have a noticeable planning error. The structure, like it was built, worked as a dam for the massive floating and size-increasing island approaching the bridge. What is surprising is that the project’s supervising entity – and again we take for granted that there was one – did not object the bridges spans.
Definitive Bridge Design
Noticing aforementioned inconsistencies, we should also question the design of the definitive bridge. The spans will be without any doubt much longer – apparently there will be three spans over an length of 480 meter – nevertheless the continuous action of the logs hitting the bridge’s concrete pillars every year during the rainy season, could debilitate the structure on the long term. The maintenance visits should be enforced strictly in this case.
Taking into account that this phenomenon is recurrent in the region, it rings the bells that in 5 days – from the first signals of a river swelling about to occur until the consummation of the collapse – the event could not have been avoided. The decision of dismantling a section of the auxiliary bridge came to late and apparently not as efficient as it should have been, if we observe the picture in this respect. We do not know how many people were working on the project and if an emergency task force was available.
We believe that loss prevention activities can be taken in order to avoid these types of losses, especially taking into account that this is a recurrent issue. The rivers can be monitored up-stream and also the precipitation intensity can be watched closely. Advanced alerts of the river’s behavior with a two day margin, consulting with local people about the historical behavior of the river at the construction site, the adoption of immediate action with machinery and equipment as well as human resources at the first sign of a “riada” and finally an adequate design of the auxiliary bridge, could without any doubt contribute avoiding or at least diminishing the loss.
We do not have any information about the project’s insurance matters, thus following comments are hypothetical and have more a pedagogical character. In an ideal world the engineering underwriter of the insurance company receives underwriting information and is aware of the local risk environment and will be doing a risk-commensurate underwriting with a fine-tuning of the deductibles or cover limits in case of special circumstances. In case of doubts of the projects details, or in case of incomplete u/w info, the insurance company would send out an inspector for a field visit where the risk can be assessed in a more detailed manner. A very important aspect during the inspection is the information about the project’s chain of responsibilities and the subject of the independent supervision of the project. We touched already this issue in one of our previous publications (News Clip 04 / 2016 Derrumbe de una Ciclovía, available only in Spanish). A critical and independent review of the project’s design is paramount. Unfortunately for financial constrictions, or due to the contractual relationship among the project owner, the main contractor and the project’s designer, the control instances can vanish.
Another subject is the risk inspection. The pictures of the case we are examining show that certain aspects of industrial safety are not being taken too seriously at the worksite. Compliance with OSHA is the first step for comprehensive loss prevention in a project and it is an important indicator of the worksite’s quality. We should mention that we did see in the past project contract wordings that force the contractor to follow strictly international safety norms like OSHA.
We were so fascinated by this event because during November 2015 in the same region a very similar event happened and with even worse consequences: can’t we learn from our past sins??? Shouldn’t we question working procedure that proofed to be deficient in the past? It is possible that there are no international norms or standards that define the forces that have to be considered in a river carrying massive amounts of wood and logs. The big question that arises is if the construction procedures are adequate: may be it would make more sense using barges for the building of the bridges pillars, instead of provisional structures exposed to the “riadas” for constructions site in those regions.