Bridge construction in extremely cold climate of Ladakh presents several challenges, including the need to withstand extreme temperatures ranging from 30 to -35 degrees, ice formation, as well as the potential for flooding, high winds, logistics and construction management issues. Also, special consideration has to be given to the materials used for the bridge as well as the design and construction methods employed.Environmental challengesSeveral challenges were faced by the execution team during the construction of Shyok Bridge in Ladakh starting from collection of hydraulic data till launching of the super structure. The use of advanced materials such as weathering steel and high-performance concrete was incorporated to ensure the structural integrity of the bridge under such harsh conditions. The construction of a bridge across the Shyok River in extreme cold climate required a thorough understanding of the unique environmental conditions and careful planning and execution to ensure the safety and durability of the structure.The union territory of Ladakh lies at the altitudes varying from approximately 9,000 to 18,000 feet. Due to extreme weather, a small working window of 5-6 months is available to execute all projects and after that, temperature drops down up to -35 degree followed by snowfall which leads to the closure of passes and roads. The Darbuk-Shyok-Daulat Beg Oldie (D-S-DBO) road in eastern Ladakh is a strategic road which crosses the Shyok River near Shyok village.BRO recently constructed an all-weather 120 m long, steel superstructure through type, Class 70, two span (30 m and 90 m) permanent bridge at 12,300 feet. The bridge has been constructed over the mighty river Shyok, a tributary of the Indus river that flows through northern Ladakh before entering Gilgit-Baltistan. Shyok river is also popularly known as the “river of death” because of its high current and sudden floods, and it is very difficult to ford through the river especially in summers when snow melting rate is higher.Importance of road & bridgeThe D-S-DBO road is a 256 km long road running almost parallel to LAC which connects foot hills of the Karakoram pass to the rest of the India. It is a strategically important axis and critical for the induction of our armed forces and equipment up to the Line of Actual Control (LAC) in eastern Ladakh. The road crosses water obstacles at a number of places, however, the first crossing on the mighty River Shyok is near the last Indian village of Shyok. The existing 320 feet Bailey suspension bridge (BSB) was of load class 18R and has also one of the world’s highest bailey suspension bridges. However, this bridge allowed passage of only light vehicles and the induction of heavier vehicles and equipment was done by fording across the river which posed great threat to troops and equipment during high flood conditions.The site selection for the bridge was done after taking into consideration numerous factors including geological survey, testing of soil conditions, study of hydraulic data flooding and water flow to reduce impact of scouring, width of stream, accessibility of site and environmental impact to ensure the safety and stability of the bridge. The approaches to the bridge were aligned in a way that bridge remains perpendicular to the flow of river. The bridge site was selected at place where minimum width of river at HFL was available, which ensured lesser span of the bridge reducing the time and cost of construction. The bridge was proposed towards downstream side of the existing Bailey suspension bridge.Overcoming multiple hurdlesExcavation: Excavation at this site was full of challenges due to permafrost conditions during winters and floods during summers. Selection of the right time was crucial and therefore excavation had to be completed between mid of March to end of May as water level increases rapidly after mid of June due to excessive snow melting. To address the issue of high seepage and percolation of water through river, four dewatering pumps each of capacity 75 Hp were employed for unhindered operations.Corrosion: Since the temperatures during the months of May to September range between 10°C to 30°C, all cementitious works were executed during this period ensuring rapid construction in the limited time available. Quick setting compounds were also used to speed up the pace of setting of cement. In order to avoid corrosion of steel, it was brought to site just before construction and coated with anti-rust paint and cement slurry to prevent further corrosion.Reinforcement: Due to excessive dryness in the air, curing of concrete was ensured thrice a day for 20 days from a drinking water source nearby and not from the river itself to prevent hard water related chemical reactions in the concrete. Since Ladakh lies in seismic zone IV, seismic arrestors were installed along with the pedestal. Moreover, importance was given to seismic arrestor reinforcement as per the design to ensure safeguards from earthquake.Logistics: Launching of the steel superstructure at this location was a massive challenge. Closure of passes and the road geometrics posed a lot of problems in induction of the long bridge members. However, optimally designed members and careful planning of induction routes assisted in speedy and smooth induction of the critical bridge members. Due to limited time available, heavy wind flow and large temperature variation, it was decided to use the temporarily constructed steel pillions as the water level between the months of October to May was lesser. Any further delay would have led to increased flood levels and could have damaged the bridge by flooding these temporary pillions. Therefore, timely launching of the bridge was very crucial. The span of 30 meter was completed in 2021. However, launching of 90m span started during peak of winters in Jan 2022 at minus 30oC degrees.Climatic conditions: Due to extreme cold temperature of -30oC, it was very dangerous to even touch the metallic members despite wearing extreme cold climate gloves. Therefore, a number of construction teams were employed on the project and were made to work in tandem to prevent cold climate injuries. Provision of hot water was also done for workers to place hands in hot water to prevent chill blains and frostbites. Medical teams were placed at the work site to constantly monitor the health of workers and to immediately act on any issues arising out of high altitude and extreme climatic conditions. The Karmyogis were constantly motivated amidst the hostile weather conditions. The leadership at all levels played an important role in motivating the Karmyogis for working tirelessly in such an environment.Timeline: The launching of the 90 m span was a calculated risk as the river started flooding in May 2022. Completion of the launch before the floods could wash away the temporary erection pillions became very critical. The launching was completed on 2nd May 2022 and simultaneously, preparation for fixing of bearing and deck slab started. The approaches were completed by the time launching of the bridge finished. Load testing was done with due deliberations and was handled with great care and the completed bridge was tested for static and dynamic loading. ConclusionThe construction of Shyok Setu was full of challenges posed due to terrain and weather. The construction of this bridge required detailed planning, time bound execution, continuous monitoring, motivated team and coordination at all levels. The bridge was completed in September 2022 and was dedicated to the nation by Honourable Raksha Mantri, Rajnath Singh on 28 October 2022. The Shyok bridge is a testimony of the resilience, perseverance and strong will of BRO and its Karmyogis. The bridge will play a pivotal role in not only  maintaining operational road infrastructure for the Armed Forces in such inhospitable and far-flung border areas, but will also contribute to the socio-economic development of the Ladakh region.Authors: (Contributed by: Lt. Colonel Durgesh Chandra Gaur, Borders Road Organisation)