Ground was broken May 1912, there is a photo set from insurance company Manning Brothers that resides in the Avery Collection at Columbia University NYC in the Warren and Wetmore Collection.

[Excavation had commenced at least by the spring of 1910. Below, headlines from May 16 and Oct. 17, 1910. Also, "circa 1910" does not necessarily mean "in 1910." - Dave]

Are the two fellows in the foreground "waterboys" (or perhaps more appropriately, watermen) for the crew? If so, it appears the fellow holding the ladle is an unhappy customer, who seems to be a little suspicious of the cleanliness of their wares. In 1910 I suppose they weren't as keen on hygienic issues and had no qualms about sharing the common cup with their fellow workmen.

Although the topic is "excavating," it appears these men are moving gravel or road base off the flatcars and spreading it as a foundation. There is a similar running pile alongside the tracks on the right that is being attacked. Regular Shorpy readers know about the evolution of the steam shovel, which is working its way along the distant bank, whose curvature reflects the swing of the shovel arm. Presumably the weather is brisk enough to dress warmly.

Forty four men working. Today: possibly two for the same job.

In the foreground, on the wooden planking there are two track jacks and a pair of "Texas Toothpicks" used to operate them. The ones I've encountered were rated at 100 tons, I on the other hand wasn't.

Here is a website showing the degradation of this once-magnificent structure.

http://www.seedetroit.com/pictures/mcsweb/

It looks like the building to the right just suffered a fire on the second floor.

The trick is to take small shovel-loads, quickly. Too often, one tries to make the job easier by taking big "bites." Harder work, and less effective in the long run! What my dad always referred to as "a lazy man's load."

This photo shows the past and the future of earthmoving: men shoveling the earth to the steam-powered shovel at the left of the photo.
But no bulldozers. Perhaps diesel/gas engines had not yet developed a power/weight ratio suitable for the needs of a bulldozer - but you had the idea on the front of locomotives: the cow catcher (and snow plow).
Everyone wore a hat, but no protective headgear. Why wear a vest during such strenuous activity?

Hated by laborers everywhere through the years. They appear in numerous folk and blues songs and the dislike is justified. I had to use one in a summer job as a kid and they are back breakers.