Clarence Stanley Coe (December 24, 1865 – March 5, 1939) was an American master bridge builder and railroad civil engineer, who supervised the planning and building of the Florida East Coast Railway's Seven Mile Bridge, linking the Florida Keys to Marathon, Monroe County, which, when completed in January 1912, was acclaimed as the longest bridge in the world and an engineering marvel. Later, Coe was appointed the first city manager of Miami, Florida, and after that was appointed chief engineer of Duval County, Florida.
Early life and career Coe was born as one of the nine children of Sylvester Coe and his wife, Ann (née Rowlands), a native of Llangollen, Wales.
He was educated at the University of Minnesota, earning a degree in engineering in 1889. "Col. Clarence S. Coe," Iowa City Press Citizen, Iowa City, Iowa, March 11, 1939, p.4. After graduation, Coe held various engineering positions in the rapidly expanding railroad industry.
In 1905, he joined the Florida East Coast Railway, first as resident managing engineer of the Key West Extension, having charge of viaduct construction. As resident manager, he constructed viaducts totaling nearly 12 miles over open water. Coe had charge of the entire engineering and inspection departments, the labor force, and all floating equipment.
In 1910, Coe was promoted to division engineer with responsibility for overseeing construction of the Seven Mile Bridge over open ocean, a feat never before attempted.
Involvement with Florida East Coast Railway The railroad line south of West Palm Beach was constructed in phases by the Florida East Coast Railway and its predecessor systems. Founder and owner Henry Flagler began his railroad building in 1892. Under Florida's generous land-grant laws passed in 1893, could be claimed from the state for every mile (1.6 km) built. Flagler eventually claimed a total in excess of two million acres (8,000 km2) for building the FEC, and land development and trading along the line became one of his most profitable endeavors.
Before it became the FEC, the Jacksonville, St. Augustine and Indian River RailwayRoute May, circa 1893 was constructing a line southwards from Daytona Beach in 1894. Fort Pierce was reached on January 29, and West Palm Beach on March 22. Further extension southwards did not begin until June 1895, when a favorable deal was signed with Miami-area business interests. Fort Lauderdale was reached on March 3 of the following year. By April, the construction reached Biscayne Bay, the largest and most accessible harbor on Florida's east coast.
Key West Extension
Flagler next sought perhaps his greatest challenge: the extension of the Florida East Coast Railway to Key West, a city of almost 20,000 inhabitants located beyond the tip of the Florida peninsula.
One of the reasons Flagler wanted to build the Key West Extension was at the time Key West was a major coaling station for ship traffic between South America and New York. Flagler thought it would be profitable for coal to be brought by railroad to Key West for coaling those ships. But by the time the railroad was finished in 1912, range had been extended on the ships to such a degree that Key West was no longer a desirable stopover for coal.
Flagler also believed that linking Key West to the mainland after the United States announced in 1905 the construction of the Panama Canal, since the city was the United States' closest deep-water port to the canal, would be of advantage to Cuban and Latin America trade, as the opening of the canal would allow significant trade opportunities with the west.
The construction of the Overseas Railroad required many engineering innovations as well as vast amounts of labor and monetary resources. At one time during construction, 4,000 men were employed. During the seven-year construction, three hurricanes threatened to halt the project.
Despite the hardships, the final link of the Florida East Coast Railway was completed in 1912. On January 22 of that year, a proud Flagler rode the first passenger train into Key West, marking the completion of the railroad's overseas connection to Key West and the linkage by railway of the entire east coast of Florida.
Coe’s involvement in building the Seven Mile Bridge
Originally known as the Knights Key-Pigeon Key-Moser Channel-Pacet Channel Bridge, the Seven Mile Bridge was constructed from 1909 to 1912 under the direction of Coe as part of the Florida East Coast Railway's Key West Extension, also known as the Overseas Railroad. The logistics of assembling labor and materials and overcoming the difficulties presented by deep water, normal tides and hurricanes attest to the engineering and management skills of those connected with its construction, all under Coe’s leadership and supervision.
The prevalence of devastating hurricanes and heavy seas made it imperative that the structure be unusually strong. First, the positions of the piers were charted under Coe’s direction; then dredgers scooped the sand from the sea's bed, exposing the coral rock necessary for foundations. Next, tugs towed up coffer-dams, huge steel cylinders, which were lowered over the dredged positions. Floating pile-drivers then drove steel-pointed piles into the coral rock until they were securely fixed. Through this method of working there was less risk of the piles slipping owing to shifting of rock, for the constructors were able to determine if the rock was solid or unstable and crumbling.
After the sinking of the piles, concrete was dumped upon the sea bed to a depth of 5 ft., forming the real basis for the piers. Molds were used for the shaping of the reinforced concrete arches and great precautions taken to obviate cracks set up by expansion. The rubble for the concrete was blasted out of the coral, and lifted onto floating platforms, where it was flung into large mechanical mixers.
When the track passed over shallow water travelling excavators were utilized to form a solid embankment of debris. Pipe-lines were laid down in some places along the center of the permanent way, and the ballast pumped through these conduits was deposited where required, the water draining off. The drying and draining of these embankments took a long while owing to the saturated state of the soil.
Coe determined that the destructive force of the waves lay not in their impact against the bank, but in their retreat or undertow, which dragged away and undermined it. Experiment proved that a smooth surface, over which the heavy seas might glide and in their retreat find no hold, offered the best solution to the problem. Material for such a coating was discovered in the marine marl deposits along the line. This form of clay spread over the surface of the embankments, hardened on exposure to the air, and was capable of withstanding the heaviest seas.
The railhead approached Knight's Key itself in February, 1908. Operations then ceased temporarily while the builders considered how the seven miles of sea, varying from 18 to 22 ft. deep, should be overcome. Owing to the impossibility of dumping for an embankment, Coe decided to build a viaduct. This Knight's Key Bridge is the longest single structure in the whole Key West Extension, stretching seven miles across open sea. From one end of it the distant shore is barely visible. Due to the depth of the water, huge steel girders mounted on concrete piers were used. The bridge comprised 316 80-ft. spans, 19 60-ft. spans and 210 53-ft. concrete arches at the southern end where shallower water was found. The track itself lay 30 ft. above the low tide water mark. At the point where the lines ran across Moser Channel a swing bridge, approximately 250 ft. in length, was introduced to allow the passage of shipping.
At Bahia Honda, there was another strip of open sea, where depths of 30 ft. were encountered, and this presented an even greater obstacle than the Knight's Key section. Bahia Honda has a total length of just over a mile. Here Coe decided that another bridge had to be constructed, having 13 spans, each 128 ft. long, 13 spans of 186 ft., and one more of 247 ft. In addition there are nine arches of 80-foot span.
When the work on bridges began beyond Knight's Key, Coe outsourced the setting of the steel to various contractors. As this method proved unsuccessful, the operations were put exclusively in the hands of Coe's own men. The deck girder spans were brought to the piers on barges, and were then lifted and set in place by floating derricks. The railway gangers completed their tasks in less than half the time taken by the contractors. On one occasion, six spans were placed in position within four hours, while on another the laborers erected a span in twenty minutes. The Bahia Honda bridge was built by means of temporary timber framework and an overhead travelling crane. The precautions taken to ensure the workers' safety were such that not a life was lost during the erection of the 32,900 ft. of steel that went to the building of Knight's Key and Bahia Honda bridges.
But even these two great bridges did not suffice. Before the island of Key West could be reached by the railway, yet another 2,500 odd feet had to be traversed, and Coe decided that a viaduct would be best for this remaining part of the route.
Coe had yet another problem in the adequate protection of the vast quantities of steelwork in the bridges from the effects of oxidization caused by exposure to salt water. The excessively moist air of Florida also rusts metal within a short space of time. Experiments to discover the most suitable rust-proof paint had been numerous, based, for the most part, on the anti-fouling compositions of red-lead similar to that used on ships' keels. The rails are also exposed to the rapid corrosion set up by the saturated air and are treated with a special protective covering.
Despite the tropical storms and hurricanes which abound in this part of the world, the extension has successfully withstood the most violent attacks which the ruthless fury of nature can unloose. One of the worst hurricanes experienced beat down upon the works in 1906. Coe, who had been carefully observing atmospheric conditions, noted an approaching disturbance, and the governmental observatory also gave him due warning. The builders, however, had received a false alarm in 1905 and did not take sufficient heed The storm swept mercilessly upon the workings. The gangers scurried to the frail shelter of their floating quarters on the barges. The houseboats were torn loose from their moorings; some were driven out into the fury of the raging sea, while others were flung and shattered against the keys and reefs. Passing steamers rescued many survivors after days of exposure, but more than seventy men were lost.
In 1909, another hurricane reached a velocity of 125 miles an hour. This time, warning instructions were observed and the barges towed into safety beforehand. Although miles of embankment were washed away no real damage was done to the concrete work. Five girders on Knight's Key Bridge were blown from their piers due to the failure of the contractors to put in the necessary number of anchor bolts. A study of the destructive force of these storms was responsible for many radical changes in construction plans, and as a result the present work is practically storm proof.
Some remarkable figures give an idea of the vast amount of work involved in the construction of the Key West extension. The project from beginning to end meant the assembling of 38,000 tons of structural steel, 461,000 cubic yards of concrete; the transport and distribution of 800,000 barrels of cement, 96,000 tons of rock, 78,000 tons of gravel, and 300,000 cubic yards of coralline rock. In addition to this the constructors had to shift some 2,000 tons of reinforced steel, 70,000 pine piles, and approximately 100,000 tons of spoil for filling in shallows and making up embankments.