The challenges and mitigational measures undertaken by BRO during the construction of world’s highest pass at 19,300 feet on the Chisumle-Demchok road.One look at the mighty Ladakh ranges and it feels a poetic connect with them. The mountains and especially the passes do seem to beckon the patriotic spirit in the hearts, as one is naturally drawn to the warriors’ call of protecting the motherland with help from these majestic peaks. The Indus valley separates the Kailash and Ladakh ranges and also runs along LAC in the Demchok sector. The passes atop the Ladakh ranges are gateways to the Indus valley and onwards into China.World’s highest passOne such pass, which is strategically important, as it provides direct link between forward posts of Demchok, overlooking Indus valley and beyond to Chisumle, is Umling-La. Located at a distance of 15 km from the LAC and at an altitude of 19,300 feet, Umling-La is the highest motorable pass in the world. The pass witnesses winds with very high speeds throughout the year and the working conditions are extremely tough due to the wind chill and lack of oxygen. The 52 km long Chisumle-Demchok road traverses this pass.Testimony of BRO’s gritBRO was entrusted with the task of converting an existing mule track along this alignment to single lane enhanced specification road with a formation width of 12 metres. It was a challenging task indeed, as approximately 20 km of the total stretch passes through areas with hard rock profile. The road today bears testimony to the resourcefulness, grit and untiring devotion to duty of Border Roads personnel.Any construction activity at such an altitude is bound to be fraught with numerous challenges. The challenges encountered were met with equally strong resolve and innovative means. These are enumerated in the succeeding paras.Challenges encounteredIn India, several cold weather zones exist in Northern and North-Eastern regions of the country where extreme temperatures vary from acute winter temperatures of nearly -25oC to moderate summer temperatures of +20oC. This significantly alters the thermal regime within the pavement and the ground below it, thereby, bringing changes in the particle state of the ground. This results in deformations and excessive thermal stress, which have a detrimental influence on the pavement.Prevailing climatic conditionsThe Changthang valley and its higher reaches experience extreme climatic conditions ranging from severe winters between November and March. The annual temperature variation could range from as low as -35oC in some places during winters, to as high as +25oC during peak summers. On an average, the temperatures within a region may vary from -25oC to +20oC. Undertaking pavement surfacing activity in the cold climate is challenging which demands adoption of special precautions and understanding of the factors like frost heaving and thaw heaving, highly permeable soil, round the year availability of water and extreme temperatures that contribute to the peculiarity of cold weather pavement works.Restriction of time and spaceDue to the super high altitude and climate prevalent in the general area of Chisumle-Umling La-Demchok, the period available for construction activities is extremely less, only between May to September. However, this being a single lane road and with no other roads or tracks available, the deployment of resources itself became a challenge.Effects of altitude on human and machinesThe harsh climate with approx 60 per cent lesser oxygen than MSL and extremely low temperatures takes its toll on human body as the workers suffer from frequent nose bleeds, high BP and high altitude sickness. Even the machines are not left untouched as low oxygen in the atmosphere forces tippers and dumpers to work at 50-60 per cent efficiency. Moreover, 4 x 2 tippers/dumpers are unable to ply at such altitudes with full load.Surmounting ChallengesThe non frost susceptible sub base (NFSSB) and base layers were a big challenge. In order to ensure that the road remains strong and retains its smooth driveability throughout its design life, it had to be ensured that the pavement is free of the effects of heaving and thawing. Accordingly, layer composition was chosen as non frost susceptible sub base layer provides larger particles with no sand rather than granular sub base (GSB) layer which is normally used at lesser altitudes. This has prevented the uneven settlement on Chisumle-Demchok road due to frost heaving and freeze thawing.Multiple attack pointsTo exploit the short working window or season, multiple attack points were selected. These stretches were identified as 20-23 km, 25-27 km and 28-30 km. For doing this an existing foot track was improved so that it could be accessed by own vehicles.Man and equipment managementThe effects of adverse climatic conditions on human body were obviated by a smart rotation scheme especially for the labourers where in a 2-1 working cycle was devised incorporating two days of working at altitudes more than 18,000 feet followed by one day of relative rest by employing them on crushers / HMP operations at altitudes less than 15,000 feet. Similarly, intensive equipment management with the help of an experienced team from dependent workshop was carried out in order to keep the down time of vehicles and plants to a minimum during the brief working season.As one stands at Umling-La, one is met with strong gusts of wind from the west and the gusts are so strong that one is pushed back for a while. It seems that Umling-La acknowledges the efforts of the BRO and works in unison to thwart any malafide intentions of our adversaries. Despite several setbacks in the form of disruptions caused due to Corona outbreak, non availability of labour and the ongoing faceoff with China, BRO successfully completed the work on this road within the stipulated timeframe and with the highest quality standards.(Contributed by: Border Roads Organisation)