There are two separate types of “dependencies” in project scheduling. They are called “hard” and “discretionary” dependencies.
Hard dependencies can be defined as constraints that are embedded in the laws of nature: you can’t boil the egg until you boil the water, and you can’t boil the water until you apply heat. You may wish that such were not the order of things, but it is. And the time it takes to do each of those tasks determines how long you have to wait for your hard-boiled egg. Both projects and history are at the mercy of hard dependencies.
Conversely, discretionary dependencies are optional, applied by decision – of the project manager, or of the various actors in history. Sometimes such decisions are wise, sometimes they are disastrous, and sometimes we never know because the way things worked out is the only history we have.
T.R. and the Panama Canal
Theodore Roosevelt knew that to make the U.S. into a major sea power, its navy needed the ability to sail quickly between the Atlantic and Pacific Oceans. A predecessor for such mobility was the construction of a U.S.-controlled canal through Central America that would allow rapid transfer of Navy vessels between oceans. For a variety of reasons, including internal political ones1, the optimum location for such a canal seemed to be the isthmus of Panama, which at the time was part of the country of Colombia.
But the Colombian government was proving difficult to work with. Roosevelt’s administration, in Machiavellian manner, fomented and supported a revolution that placed the isthmus under the sovereignty of the new nation of Panama, a government obligated to the U.S. for its very existence.
With a project manager’s eye, Roosevelt chose a location where it would be possible to cannibalize work that had already been accomplished – the long-desired “path between the seas” would be created on the ruins of the French effort that had lost steam and foundered in the jungle two decades earlier. What had been the main cause of the French failure? Yellow fever, which along with malaria, had killed thousands of engineers and laborers brought to Panama to dig the canal.
Yellow fever would almost certainly have doomed the American effort as much as it did the French. But timing is everything! During the U.S. occupation of Cuba following the 1898 Spanish American War, Major Walter Reed had succeeded in confirming the theory of Cuban scientist Dr. Carlos Finlay – yellow fever was caused not by contact or aerial transmission, but by mosquitoes. And, with even more serendipitous timing, the India-born British doctor Ronald Ross had also tied malaria transmission to mosquitoes in 1897.
The discovery of yellow fever’s cause is sometimes viewed as a hard predecessor for the great American construction effort, one without which the American canal effort would have been as doomed as its French predecessor. But the fact that the mosquito danger was understood by the Americans did not necessarily mean that they had to address it! They could simply have accepted the risk instead of trying to mitigate it.
It would require great expense to eliminate the threat: time to clear the jungle around the working and living areas, to drain wetlands, to pour oil in stagnant pools, and to provide screens for worker domiciles. All this work (in project management terms, a fragnet) would likely delay, by months or years, the eventual opening of the canal. Decreasing or eliminating the yellow fever threat might be very advantageous, but it still was in fact a discretionary predecessor, to be performed or not on the basis of cost/benefit analysis.
Was such analysis performed? In project management terms, did Roosevelt and his planners determine all the work they were going to have to do in building the canal, assemble a critical path method (CPM) schedule, and determine both the end date and the number of lives that would be lost during those years of effort?
Did they then plan out the fragnet of work for resolving the disease threat, plug it into the rest of the schedule, see how much time it added, and compute the fragnet’s critical path drag, its drag cost in terms of the delay in the utility of using the canal, and the value-added from a value breakdown structure (VBS) in terms of reduced deaths? And did they then have a conference, shouting back and forth about whether or not the delay in America’s strategic advantage outweighed the cost of the unmitigated risk of greater mortality?
It seems highly unlikely that any of that analysis was performed. Yet the Americans made, perhaps through luck, what in hindsight we would regard as the correct management decision. With the failure of the French effort as a reminder, they took the time to deal with the mosquito threat. Whereas 22,000 lives were lost to yellow fever and malaria in thirteen years of the French effort (during which only about a quarter of the eventual distance was traversed), fewer than 6,000 lives were lost to all causes during the ten years of the American effort, and almost none to yellow fever after 1906. Instead of the pool of willing workers in the West Indies drying up out of fear of death in a faraway jungle (as happened with the French effort), laborers were eager for the comparatively good paying work. Almost half of the adult males of the island of Barbados, approximately 20,000, would ultimately work on the canal, sending money back to their families and acquiring new skills with a variety of machinery. And once they were there and trained, they didn’t die by the hundreds, requiring new workers and the expense of renewed training.
Whatever the reasoning, history has justified the American decision-making process. In Part 2 of this series, we will see how another decision regarding the inclusion of a delaying fragnet during the Second World War may have led to less satisfactory results.
1 This topic is wonderfully covered in David McCullough’s The Path between the Seas: The Creation of the Panama Canal (1870-1914), (Simon & Schuster, 1977).