GATUN LOCKS OPENING INTO THE LAKE
The skeleton structure on the left is the frame-work of the emergency dam which swings directly athwart the lock
Not very long ago there was a wide-spread apprehension in the United States, bred of a rather shallow newspaper criticism very widely republished, that the Gatun dam would prove inadequate to the pressure of the waters impounded behind it and might collapse, or “topple over”. If all who have been impressed by that gruesome prophecy could see the dam itself their apprehensions would be speedily quieted. One might as well talk of toppling over the pyramids, or Murray Hill, New York (not the structures on it, but the hill itself) or the Treasury Building at Washington. Elevations, natural or artificial, the base of which is eight to ten times their height, cannot topple over while the force of gravity continues to operate. Now the height of Gatun dam is 105 feet, and from its crest the filling of clay and rock slopes gently away on the landward side for nearly half a mile. There are more abrupt eminences on many of our rolling prairies. The face on the lake side descends somewhat more abruptly, but is still several hundred feet long before its slope ends with the bed of the lake. This face is covered with broken stone down to the “toe”—as they call the walls of rough rock between which the dirt dam was built.
Photo by Thompson
GATUN LAKE SEEN FROM THE DAM
Copyright, 1911, by Munn & Co. Inc. From Scientific American
BIRD’S EYE VIEW OF GATUN DAM
In the foreground the locks, only two of the three steps being fully shown. In the middle distance the spillway, through which surplus water flows into the Chagres and old French Canal
The method of building the dam was simple enough even though it sounds complicated in the telling. When Congress acquiesced in the minority report of the Board of International Engineers, approved by the President and recommending a lock type canal, it meant that instead of simply digging a ditch across the Isthmus we would create a great artificial lake 85 feet above sea level, confined by dams at either ends, with locks and two short canals to give communication with the oceans. To create this lake it was determined to impound the waters of the Chagres, and a site near the village of Gatun, through which the old French canal passed, was selected for this purpose. Conditions of topography of course determined this site. The Chagres valley here is 7,920 feet wide, but the determining fact was that about the center of the valley was a hill of rock which afforded solid foundation for a concrete dam for the spillway. Geologists assert that at one time the floor of the valley was 300 feet higher than now, and that in the ages the Chagres River cut away the shallow gorges on either side of the rocky hill. These, it was determined, could readily be obstructed by a broad earth dam of the type determined upon, but for the spillway with its powerhouse and flood gates a rock foundation was essential and this was furnished by the island.
