The following precautions against accident are to be observed:
First. All vessels must stop some distance from the gates.
Second. The lock operators here take the vessel in charge and control its passage through the locks.
Third. If a vessel breaks away from the operators or fails to stop at the proper place, it comes against the heavy chains stretched across the locks and is either brought to a full stop or is greatly retarded.
Fourth. In case a chain breaks, the vessel has two sets of gates to break, if at the upper level, where an accident would be most serious. Should all these barriers fail the emergency dam can be swung into place in a very short time.
The floors of the Miraflores and Pedro Miguel locks will have 1 foot thickness of concrete on top of the rock as a wearing surface. At Gatun, however the rock is of a character susceptible to the weather. It has therefore been considered necessary, in constructing the floor here, to leave the rock above grade until just before the concrete is to be placed and then to scrape and wash the surface to be covered. The floor in the lower portion of the upper chamber is to be of concrete 3 feet thick. The rock here is considered thick enough to withstand the pressure from the water-bearing stratum below. Above the middle gate, however, this stratum is too thin, and a floor 13 feet thick of concrete is provided and anchored by rails set in holes and surrounded by concrete.
The main floor level will be about 2 feet below the sills, in order that small objects dropped from vessels may be passed without being struck.
The sills for the gates are designed as concrete arches in a horizontal plane, 31 feet thick throughout and of 100 feet radius at the extrados.
The filling system is designed so that, with all valves opened the chamber can be filled in 8 minutes, but to prevent possible damage to vessels in the lock the maximum rate will probably not be allowed to exceed 3 feet a minute which would correspond to less than 15 minutes for filling.
Most of the foregoing discussion is taken from the Engineering Record of February 26, 1910.