John A. Roebling Suspension Bridge - Construction

Construction

The digging of the foundation of the Covington tower commenced in September 1856 and went smoothly. A foundation was set consisting of 13 layers of oak beams, each layer set perpendicular to the one beneath it, bolted with iron hardware, and finally all cemented into place. On the Cincinnati side, work was delayed from the start. The construction crews could not pump water out of the excavating pit fast enough. They were attempting to dig to bedrock in the middle of a flowing river. After months of a virtual stand-still, Roebling decided against buying costly machinery or bigger engines for his pumps and, quite last minute, designed his own square positive displacement pumps from three-inch (76 mm) pine planks. He built them locally in about forty-eight hours and ran them off of one of Amos Shinkles’ tugboats, the Champion No.1. The homemade pumps displaced forty gallons of mud and clay in each cycle.

When the crews reached the compacted gravel bed of the Ohio River, Roebling decided this would be sufficient for the foundation of the Cincinnati tower. Oak timbers were laid, mirroring the foundation of the Covington tower, and within three months, masonry on both towers reached above the waterline (which, at this time, was at a record low for the fall). Work halted for the freezing temperatures and increased water level, a practice which continued seasonally until completion of the bridge. At this time, a revised contract was drawn up, stating work was to be completed by December 1858, barring "unavoidable calamities".

After a hard winter of 1856-57, and a wet spring, construction resumed in July 1857. Sandstone was used for the first twenty five vertical feet of each tower base. Limestone encased this sandstone, acting as an armor covering against the constant flow of water and the accidental collision with watercraft. The remaining height of each tower was to be constructed of sandstone, rough cut and with a large draft. Roebling said this gave the towers “a massive look, quite suitable to their function.”

Working from July to August 1857, the company was without liquid funds, a problem compounded by the Panic of 1857. Work halted due to the inability to pay for the project. In July 1858, operations resumed again, albeit with a smaller workforce. Only one tower was to be worked on at this time. President Ramson of the company would soon die, and no work would be done during the years 1859-60.

In November 1860, Abraham Lincoln was elected president of the United States, and Civil War would be declared in January 1861. Upon a threatened siege of Cincinnati from Confederate forces, a pontoon bridge would be built to span the Ohio River, allowing Union troops to cross and construct defenses. Soon after (it had become obvious that a permanent structure was vital), money from investors came pouring in. Bonds were sold, and in January 1863 materials began arriving. In the interest of building more quickly, the requirement for the height of the main span was lowered to 100 feet (30 m). Preparations to resume construction were made. Machinery was ordered, new derricks were built—but a renewed threat of invasion again temporarily halted progress. Finally, in the spring of 1863, work commenced and continued until the end of the year.

In the spring of 1864, work resumed again. Although Roebling operated his own wire mill at Trenton, NJ, one million pounds of wire were bought from Richard Johnson at Manchester, England for the cables that would span the width of the river. Roebling had used Johnson's wire for one of his other bridges. He preferred it over wire made in the United States because it was of better quality and greater tensile strength. Anchorages on both shores were constructed of limestone base and a freestone finish. Eleven ton iron anchors were embedded in each block, securing cables with wrought iron chain links of Roebling’s patent. These links resembled almost exactly the ones his son, Washington Roebling, would use in the construction of the Brooklyn Bridge. The Civil War depleted the work force on the project, hindering speed and efficiency until its end. In November 1864, John Roebling’s wife died, and Washington arrived in Cincinnati to assist his father for the remainder of the project.

Work on the bridge proceeded steadily after the end of the war. In September 1865 the first two wire ropes were laid. They were unwound from a spool on a barge, allowed to sink to the bottom of the river, then raised in unison from the riverbed. Wooden crossbeams were laid at regular intervals from the wire ropes and a simple footbridge was constructed for the benefit of the workers. With the Ohio River “spanned,” there was a final push to complete the project even through floods and freezing temperatures. The cabling of the bridge went at a feverish pace, having about eighty wires taken across the river per day. Hundreds watched the spider-like process from both shores. And on June 23, 1866 the last wire was taken across, for a total of 10,360 wires. These were subsequently compressed together and wrapped with an outer covering of wire into two cables of 5,180 wires each. Suspenders were hung from the cables by the end of August and 600,000 feet (180,000 m) of oak lumber was laid as the floor across 300 wrought iron suspended beams. Two tracks for streetcars were laid. Diagonal stays were added to increase load capacity, strengthen the floor, and check vibration. Wrought iron trusses were added, running the length of the bridge.

On December 1, 1866 pedestrians walked upon the bridge, known locally only as “The Suspension Bridge,” for the first time. Over 166,000 people walked across in the first two days. Final touches were put on the bridge over the next few months, and construction would officially end in July 1867. Only two men died during construction. When the Roebling Bridge was formally opened on January 1, 1867, the driver of a horse and buggy was charged a toll of 15 cents to cross; the toll for three horses and a carriage was 25 cents. Pedestrians were charged a cent.