Panamax is the name for the largest ship that could pass through the old locks of the Panama Canal, just under 1000 feet. That limited the size of the SS United States (“The Big U”) the largest superliner built in America. The navy insisted that it be able to transport troops through the Canal if needed. That’s why the “Big U” was under 1000 feet long while Queen Mary, Queen Elizabeth and the SS France were all over 1000, to the consternation of William Francis Gibbs, the Big U’s designer. Some American carriers had Panamax hulls but had flight decks that extended well beyond the locks. According to one of our table mates, whose son served on this carrier, the first time the ship went through the canal after lights has been installed for 24 hour operation the flight swept away the light stanchions as it passed through.
As international trade expanded ships grew larger than Panamax, container ships, super tankers, LNG carriers, and many of the newest, NeoPanamax, class of cruise ships. Panama decided to build a third lane of locks to increase the canal’s capacity and accommodate the newest ships.
The new locks are 427 meters long, as opposed 304.8 in the old locks and 55 meters wide compared with 32.5 meters in the old locks.
But there is a problem with water. The new locks use a lot of it and there is concern that in the dry season Gatun Lake which is both the main waterway of the canal and provides the water to operate the locks, may not replenish quickly enough to maintain navigation depth in the canal. So the new locks have a water saving design. Water enters the top lock from the lake. As the ship is lowered the water is sent to a series of three holding ponds, each a little lower than the one next to it. Only the lowest water in the lock flows to the lock below. The other water is reused to refill the lock, taking only enough water from the lake to replenish that water that went to the lock below. Each of the three locks has three holding ponds. They are controlled by gates. At the end only the water near the bottom of the lowest lock enters the ocean. This process reduces the amount of water spilled into the ocean by about 60%. It may be a little hard to explain so I have a graphic from the Panama Canal Authority posted below that shows the process.
There is a visitor’s center for the new locks on the Atlantic side with rows of walks from which you can watch the operation. It was an hour and a half “trans-continental” drive from Panama City to the center but it was worth it. We were fortunate enough to be able to watch an LNG carrier “Iberica Knutsen” transit the new locks. Unlike the old locks, where pleasing bells communicate what’s happening, in the new locks sirens, horns and loud beeps tell us what is going on. There are no “mule engines” holding the ships in place. Instead the ship moves with the help of tug boats and the ship is tied off to the side of the locks with winches and capstans on the ships keeping the cables tight.
Athough this is dry season, Panama has had a lot of unseasonal rain. The lake was full (see pics on the post before) so we did not see the holding ponds fill and drain and did not see the sluice gates in operation. However, taking the water directly from the lake does speed the process. While we stood at the visitor’s center (which also shows a movie and has a nature trail) we were not only able to watch the Iberica Knutsen transit the locks but follow a ship in the old Gatun Locks over the trees make its progress in the opposite direction.