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Panama Canal expansion:

a call for a change of plan

by Bert G. Shelton

The goal of expanding the Panama Canal is to create an integrated system that uses the available water most efficiently to allow more and larger ships to transit, thereby maximizing the canal’s cargo capacity while minimizing direct and indirect costs. That goal can be better met using new locks modeled after the existing ones, which contain more and better ways to save water than using side-tank locks.

A century ago minimizing water-use wasn’t a concern. The watershed had sufficient rainfall and water retention capacity to provide for maximum transits using the fastest, least water-efficient, mode of operation. So, to routinely operate the Panama Canal locks more slowly in order to save water wasn’t practical.

There are several methods by which to reduce the amount of water locks use, and using side-tanks is one way to apply one of those water-saving methods.

The three key methods for reducing water-use are:

1. Adding steps

2. Separating the steps

3. Transferring water laterally to “tanks” for re-use

All three methods are found in the lock units of today’s Panama Canal:

1. The Gatun Locks on the Atlantic Side have three steps. On the Pacific Side, the Miraflores Locks have two steps and Pedro Miguel has one. Consequently, the Panama Canal uses only one-third the water that a canal with single-step “tall” locks at each end would use.

2. Being a separated step, the Pedro Miguel Locks can first lift an inbound ship followed by lowering an outbound ship that takes the other's place in the chamber; thus, it uses half (50 percent) the water per ship. (That isn’t possible at the other two lock units, because their steps are contiguous.)

3. With two-lanes, all the Panama Canal Locks can transfer water laterally to re-use it. Water can be shared between adjacent chambers to lift and lower ships, each using half (50 percent) of the water.

Three steps continue to be considered a practical number of steps for the Panama Canal. The three-step, single-lane, triple-side-tank-per-step proposed locks were promoted as using 40 percent the water that same-size locks with three steps, but without side-tanks, would use. An equal basis is needed to compare that 40 percent to the previously noted 50 percent for separated-step single-lane locks.

When a single-lane separated-step lock set is operated most efficiently, transit direction switches with each ship. When a single-lane side-tank lock set operates most efficiently, several ships travel one way before the lane is reversed to give ships traveling the other way their turn. To compare those designs, it is necessary to account for the water released to reverse the side-tank locks, water that doesn’t directly lift or lower ships.

Adjusting for one reversal cycle per day, water used to operate the side-tank locks is 47 percent for each of the 12 daily transits planned. With more reversals, the water-use of those will exceed 50 percent. That’s a lot of side-tanks, large diameter piping, expensive valves and their operating mechanisms, long-term maintenance issues, plus the time required for three water transfers between each chamber and its three tanks, just to save an amount of water that can more easily be saved without lateral water-transfers using simpler, single-lane, separated-step locks that expose the lake to less salt.

Because of how they are arranged and operated, “Pedro-Miguel style” locks would expose Gatun Lake to less salt than the side-tank locks for two key reasons:

1. More lake water is used per chamber-load of seawater, which yields a lower chamber salt concentration.

2. Exiting several ships in a row, which pushes water containing the most salt into the lake, is avoided.

Beyond that, the simpler “Pedro-Miguel style” locks can be expanded to two lanes, which can double transits using the same water. With two-lane separated-step locks, both methods noted above to cut water-use in half can simultaneously be used to reduce per ship water-use to 25 percent, and that’s been demonstrated at Pedro Miguel.

Two-lane locks with lateral water-transfer capability are more effective than side-tanks because the adjacent chamber is not just a “water-recycling tank”; it’s a second lane. Both lanes operate sharing one water transfer. In the existing locks, this method applies whether lanes transit ships in the same or in opposite directions.

Very important and meriting serious consideration when deciding what lock type to use is that, not only will a single-lane separated-step lock set bring in a lot less salt to the lake, but the lake will be exposed to less salt when both lanes of “Pedro-Miguel style” locks are operated in contrast to the side-tank locks.

With properly integrated locks modeled after those of the Panama Canal increasing the operating range of the lake to obtain more usable water could be avoided. Modifying the lake negatively affects the operation of the new locks, the old locks and every facility in or along the shores of the lake, plus it detrimentally affects the environment. It affects equipment and routine work in the lake, as well. The marginal increase in useful water hardly warrants the cost of modifying the lake and the likelihood of higher operating costs.

Furthermore, by applying an optimum combination of existing and new lock operating procedures, fully considering each unit’s abilities, water to allow for even larger new chambers is obtainable. That would not only increase the number of ships that could transit the Panama Canal, but also the variety.

It is unclear how many side-tank units exist. It is also unclear how successful those are despite the recent, highly marketed, rise from the relative obscurity the approach languished in since the 19th century.

Allegedly the original unit no longer is operated, and it is said that the long, large diameter, interconnecting pipes between the side-tanks and main chambers of another crack due to uneven settlement between those structures.

Panama’s own locks --- containing an better approach to re-use water by transferring it laterally plus other benefits --- have proven reliable through nearly a century of operation. So, why build locks with a questionable performance history, rather than locks based on Panama’s own that are simpler, expandable without needing more water, environmentally friendlier, and clearly reliable?

Other concerns with the proposed canal expansion plan, such as its undefined impact to the environment and issues with operating methods and ship-handling procedures, added to an impression that the capabilities of the Panama Canal’s existing locks were overlooked, create the perception that there are fundamental assessments and comparative evaluations that have been omitted in a politically driven rush to begin construction.

For a project of this magnitude and global importance, such deficiencies in planning --- which all too often cause irreparable damage and perpetuate the poor use of valuable resources --- are unacceptable and cannot be tolerated.

The world is already suffering ill effects from its resources being mismanaged globally. With proper attention given to design, the Panama Canal can continue its proud legacy for future generations rather than be transformed into a monument to bureaucratic ineptitude.

The author is an engineer and research scientist

Bernal, Where is Panama headed?
G. W. Bush, Progress in Iraq
Mikulski, Remove the gag on the Iraq War debate
Wayne, Guantanamo and the semantics of terror
N. Jackson, Read and weep
Human Rights Watch, A Chilean judge's bad decision on Fujimori's extradition
Silié, Peace with poverty isn't peace
Pilgrim, Sao Paulo air crash raises deadly questions

Sánchez, Hispaniola as a major drug smuggling hub

Hill, Free trade and immigration

Gutman, Hugo Chávez is a disgrace

Shelton, A better plan for the canal's expansion

E. Jackson, Troubles at the alma mater

Sirias, The price of perfection