The bridge does not have nuts and bolts, but was formed by riveting the whole structure. It consumed 26,500 tons of steel, out of which 23,000 tons of high-tensile alloy steel, known as Tiscrom, were supplied by Tata Steel. The main tower was constructed with single monolith caissons of dimensions 55.31 x 24.8 m with 21 shafts, each 6.25 metre square. The Chief Engineer of the Port Trust, Mr. J. McGlashan, wanted to replace the pontoon bridge, with a permanent structure, as the present bridge interfered with North/South river traffic. Work could not be started as World War I (1914–1918) broke out. Then in 1926 a commission under the chairmanship of Sir R. N. Mukherjee recommended a suspension bridge of a particular type to be built across the River Hoogly. The bridge was designed by one Mr. Walton of M/s Rendel, Palmer & Triton. The order for construction and erection was placed on M/s.Cleveland Bridge & Engineering Company in 1939. Again World War II (1939–1945 ) intervened. All the steel that was to come from England were diverted for war effort in Europe. Out of 26,000 tons of steel, that was required for the bridge, only 3000 tons were supplied from England. In spite of the Japanese threat, the then (British) government of India pressed on with the construction. Tata Steel were asked to supply the remaining 23,000 tons of high tension steel. The Tatas developed the quality of steel required for the bridge and called it Tiscom. The entire 23,000 tons was supplied in time. The fabrication and erection work was awarded to a local engineering firm of Howrah: the Braithwaite, Burn & Jessop Construction Co.. The two anchorage caissons were each 16.4 m by 8.2 m, with two wells 4.9 m square. The caissons were so designed that the working chambers within the shafts could be temporarily enclosed by steel diaphragms to allow work under compressed air if required. The caisson at Kolkata side was set at 31.41 m and that at Howrah side at 26.53 m below ground level.