Massive land sliding occurred on 4th Jan 2010 near village Attabad, approx 109 Km North East of Gilgit and about 19 Km East of Hunza causing heavy loss to the life and property. The slide blocked Hunza River by covering 2 Km length of the river with debris of volume of 2.5 billion cft and created a dam with heights varying from 130 meters to 200 meters thus severing the only road link (KKH) with China.
Federal Govt approached GHQ for providing immediate assistance to tackle this calamity on war footing. In turn COAS tasked E-in-C for the needful, who immediately despatched a team of experts headed by Brigadier Nasarullah Abeer, PhD in Geotech Engineering, on 6th January2010. A plan was formulated on 13th January 2010 to make a 350 m long, 40 m wide and 20 m deep spillway cut to reduce the risk of dam bursting. After initial thought of assigning task to NHA being nullified, FWO, being most suitable organization to handle such challenging tasks was tasked on 20th January 2010 to develop the 20 meters deep spillway by cutting through the slide mass.
Execution of Work
FWO assisted by local Army formation (FCNA) mobilised with lightening speed and started this gigantic task on 22nd January 2010. Immediately FWO’s Crises Management Taskforce headed by Colonel Naseem Hassan not only mobilized 17 x plant pieces (8 x Dozers, 6 x Excavators, 3 x FE Loaders) and 2 x Compressors on site but also commenced the work despite the hazards of active slide. The first challenge was to reach the slide top by developing a 600 meters track for starting work on the spillway cut. The work, though simple became a challenge as the slide mass was slushy and loose having threat of further sliding, where the dozers / excavators tended to sink. However, despite all odds 600 meters approach track (on which we have travelled - figure-3) was constructed by 31 January and top of slide was reached despite slushy soil causing machines to sink at every step.
It needs to be highlighted that a team of experts from World Bank consisting of Dr. Richard Hughes, Dr David Petlay and Mr. Allessandro Palinieri visited the site on 11 March to conduct technical evaluation and suggest modalities to tackle the catastrophe. At site the team was taken aback to see the progress of response of FWO, they were full of praise for the speed of mobilization and the quantum of work executed by the FWO, in such a short span. The team fully endorsed the plan made by Army and NESPAK experts to tackle the catastrophe and appreciated the speed with which FWO was executing the work and commented that it was the best solution adopted under the prevailing circumstances.
While working under adverse climatic and hazardous environment FWO has completed the assigned task of spillway cut by 20 Mar 2010during which it made a 20 meters deep, 40 meters wide and 350 meters long spillway by excavating and moving over 5 million cft of slide mass. According to NESPAK experts, who were tasked by GB Govt and conducted dam burst study, this effort reduced the damage / risk by 35%. During this process, working under active slide a life was lost (volunteer scout), while another Dozer operator of FWO got seriously injured once hit by falling stones during work.
During a site visit on 11th March 2010, when the assigned cut of 20 m depth was near completion, it was felt that there was still 42 m free board left for water to rise which would take more time. Therefore, a decision was taken to further cut the spillway to a depth of 30 m so that risk of dam burst is reduced further (56% as per NESPAK study).
We have presently reached 24 m depth by excavating 7 million cft of earth debris. Further excavation has been stopped on the advise of experts (NESPAK) as there is a danger of spillway mass caving in. We are constantly monitoring the inflow, seepage and rise of water levels. Presently with seepage of approx 60 cuces there is no danger of dam bursting because as per experts, if seepage crosses 200 cuces then there is a danger.
At the request of NDMA, Army Engineers are also working hand in glove with FWO to reduce the plight of the locals struck by natural calamity by ferrying men and material across the 11 km long lake. To facilitate them Army Engineers have started a boat service since 14 Feb 2010 and are operating 17 boats for the purpose. So far they have transported over 7,500 persons and 80 tons of food supplies and fuel.
Problems / Hazards Encountered
Type of Slide Strata
The slide mass contained slushy and clayey soil which sticks and causes machines to sink.
Huge boulders of sizes more than 100 M3 were encountered during cut. These boulders slowed the pace of work as time and again blasting have to be done.
Weather in the slide area has been extreme (some times snowy and some times rainy), work continued even during snow.
The slide remains active most of the time and work has to proceed with caution. Due to active slide 2 x causalities were suffered as mentioned above.
Restricted Working Space. The slide cut is being made in restricted area / space environment. Hence more than optimum quantity of plant (maximum 17 x pieces) can not be employed.
Heaving & Sliding Effect
Progress of Work
Though FWO has completed the assigned task, and is presently doing additional task of increasing the depth of spillway cut etc So far FWO has excavated over 6.5 Million cubic feet of slide mass which has consumed 7,000 x Plant hours, 102,240 x Man hours & 167,290 x Ltrs Fuel.