Building the railroad that Went to Sea with photos. Page 2 Fill railbed over open water      The photos below are of the Upper Keys, but the methods were repeated throughout the Keys. The length of the fill and the associated water depth varied the methods a little. The Hurricane of 1906, however, emphasized the change from marl on the inside and rock on the outside to the opposite. Clean ocean marl sets up almost like concrete when allowed to cure.      Lake Surprise and Indian Key Fill were examples of making a causeway across open water. Indian Key Fill was different as it had to withstand ocean waves, winds and tidal action. It was also effectively a group of short bridges connected by segments of causeway.      It appears that the first dredges were deployed to the Everglades and Lake Surprise areas. This supports the theory that they wanted to lay track as quickly as possible from Miami/Homestead as possible. The lack of a portable concrete mixer delayed the completion of the Jewfish Creek Bridge. Then it was discovered that the Lake Surprise causeway was not stable. Most of the special floating construction equipment was made from Mississippi River barges as a foundation. This will be shown later.      The lack of piling and side bulkheads combined with the different marl dredged up from Lake Surprise made a very weak railbed. The story has it that it took 15 months to stabilize the railbed to consistently support daily operation of a loaded construction train. Even years later it was a problem for the Department of Transportation for vehicle travel.      From the Indian Key Fill images below, it is clearly seen that lateral support was provided. The ocean marl also sets (hardens) much firmer than the humus riddled Lake Surprise marl.      In the above photo, the obviously flat railbed is actually the bridge portion across the Tea Table Channel. Regardless of the fill, very little rock was hauled in as fill, except for bridge approaches and low spots on the islands (Dove Creek and connecting the Umbrella Keys.)      A major supply depot called "Central Supply" was constructed on the sides of Indian Key Fill and a draw bridge installed for ocean and bay access. It is believed that this was the area referred to as "Ocean City" by newspapers.      Next, we will move on to the construction of railbeds on island hammock surfaces.