Water Eats Away At Dam Wall
For 30+ years, workers have been pumping concrete into the ground on a daily basis to prevent the dam from collapsing.
The Mosul Dam was completed in 1986. It was constructed after 30 years of planning and geological studies, but the dam still ended up being located the first years following their completion, Mosul Dam is especially problematic. This is probably due to the fact that geologically, it is located in the worst possible place, and in spite of the massive and ongoing repair and shoring-up operations, the entire site has only become more vulnerable over time.
In 2004, American military engineers took a close look at the dam, and agreed with every other engineer: it was extremely in the wrong place. Some of the rock layers under the huge structure are watersoluble, threatening to undermine the foundations and make the dam collapse. unstable. This study finally made the Iraqi authorities accept that the dam could no longer be allowed to operate at full capacity.
So, the water level of the reservoir was lowered to 22 m under the edge of the dam wall. The advantage of lowering the water level of the lake is that the pressure on the dam and inside the rock is reduced.
When the rock pressure is reduced, the water-soluble minerals will disappear more slowly. But at the same time, power generation and the possibility of upholding a constant, agriculturally-vital water level in the Tigris River further south during the dry season are affected.
And although a lower water level reduces the risk of a collapse, it will only limit the damage slightly if the disaster strikes. The water level drop can only reduce the height of the death-wave from 26 to 23 m.
"FIRST AID"
Over the last 30 years, the team responsible for underground maintenance has pumped 95,000+ tonnes of concrete into the rock from a service tunnel located along the entire length of the base of the dam.
In 2014, the dam ran into severe problems, when ISIS rebels occupied it for 11 days. Engineers and workers were forced to escape, and some of the equipment was destroyed. So, the important maintenance which had been carried out 24/7 since the completion of the dam was halted, and although Iraqi military forces soon got the dam back, the maintenance was not resumed according to previous standards.
When US Army Engineers inspected the damage in 2015 following the US war and occupation, their message was alarming. In a report from 2016, they described the situation as time-critical, emphasising that the dam really could collapse at any time.
The authorities hired a firm of engineers to repair the damage right away, and the water level was lowered once again – this time to 26 m below the edge of the dam. Such a low water level means that more than half of the reservoir’s active volume – the volume of water which can pass through turbines to generate electricity – is missing.
THE BIG FIX
So, engineers began to take a closer look at more permanent solutions. One option involves closing the dam and constructing another one 30 km to the south, where the geology is much more suitable and safer, but in that case, the reservoir would be much smaller. Another option involves sealing the lake bed of the part of the reservoir which is located the closest to the dam using balls of clayey bentonite. The balls will slowly absorb water and expand, finally making up an almost waterproof armour. However, engineers are most likely to choose a third option - the construction of a waterproof, underground wall from the base of the dam and all the way to the massive rock 100 m into the ground. The wall would solve the problem once and for all, but it would also make up a huge technological challenge. Nevertheless, engineers have already completed the wall design, so there is still hope for the people of Mosul.