Lessons not learnt
THE tumult generated by the collapse of Gate 47 of Sukkur Barrage in Sindh subsided after the irrigation department brought the situation under control by constructing a cofferdam. This was made possible by dextrously dumping over 3,000 sand-filled, one-tonne sacks amid a flow of over 100,000 cusecs. Department engineers and local fishermen worked round the clock to contain the crisis. A 9-by-18-metre sandbag platform was created to block the flow of water, thus enabling the fixing of a caisson in place of the collapsed gate. The authorities heaved a sigh of relief as water supply to the canals was restored partially.
Moreover, work to replace Gate 47 has commenced before the scheduled date. Local media, growers’ organisations and civil society forums are abuzz with all manner of speculation and apprehension. Meanwhile, four senior officials who were posted at the barrage have been removed.
Lowering the pond level by draining water downstream revealed more gates with cracks. Gates 46, 48, 52, 53 and 54 showed structural fatigue, which points to a lack of regular inspection and maintenance. It underscores the need for an urgent inspection of all gates to ensure structural safety before the monsoons trigger massive river flows. A crack in a gate or the masonry structure of the barrage is not something to be shrugged off, as it could result in devastating consequences if not addressed at an early stage.
Regular inspections of Sukkur Barrage gates are needed.
An incident from June 2018 should have served as a lesson for the authorities. On June 21, 2018, staff at the Sukkur Barrage noticed a crack on the outer flange of the upper girder of Gate 39 during a routine inspection. An in-depth technical study was conducted by Atkins, ACE & NDC Joint Venture in July 2018. The report revealed that the web plate of the girder showed high corrosion in almost all parts. The epoxy coating of horizontal surfaces of the components of the structure had either been totally eroded or badly damaged. This was on account of a leaking water jet that was directly impacting these horizontal surfaces.
Most of the bolts connecting the different components were badly rusted. The two horizontal stiffeners welded at the skin plates showed deterioration due to algae. Only 17 bolts were fixed in the two cover plates of the back flange, against a total of 24 holes available in the two plates. Two bolts were fastened without washers; while 15 washers were of different sizes.
Similar deterioration was noted in Gate 38, though the damage was less severe. The report also mentioned that Gates 15 to 23 had wooden plank extensions to raise the pond level. The tail channel gates were found to be leaking heavily, with water showers falling on the upper girder of most of the gates. Extensive accumulation of waste material was observed upstream in a few gates. Gate 39 especially had been exposed to a large accumulation of waste material extending to about 6m to 7m.
The original river sluice gates of the barrage were 5.6m in height so that a pond level of around 60m could be achieved. However, in 1966, the height of the gates was increased by approximately half a metre to achieve a higher pond level. New gates were installed during 1988-92 after the collapse of a gate in 1982. However, to further increase the pond level, these gates were increased in height by half a metre in 2008-10, with the use of wooden planks. Leakage from these planks caused rusting in different sections of the gates.
An inspection of the Sukkur Barrage gates was assigned to NED University in January 2019 under the Sindh Barrages Improvement Project. A team of experts inspected 20 gates. The report revealed that while the upper sections of the gates were in stable condition, the lower sections of most of the gates had been severely corroded. Fourteen gates showed a reduction in thickness in the lower portion. The reduction was estimated to be less than 10 per cent in the vertical girder flanges, the web plates and main skin plates of these gates. On the other hand, seven gates showed a reduction in thickness of below 20pc. The report recommended either repairing the lower sections of the gates or replacing them along with girders. Subsequently six gates were replaced.
A technical investigation into the damage done to Gate 39 in 2018 and the rupture of a gate in 1982 provides sufficient evidence of structural fatigue. Increased surveillance and regular maintenance of the barrage gates is absolutely essential to avert a dangerous situation. The authorities must not delay matters on this count.
The writer is a civil society professional.
Published in Dawn, July 16th, 2024