It might seem like todays’ post should have come before yesterday’s, but I feel it’s easier to understand the pictures of the early stages of excavation at 15 Broad Street if you’ve already seen what the final result looked like. In any case, the picture above shows the beginning of excavation. Note that the site grade is already below street grade (the truck on the right is on a platform at street grade) but that’s because the buildings that had been demolished on the site had cellars.
The thing that jumps out in that picture is the triple line of piles bottom center. The group of pile sections lying on the ground at the lower left, next to the word “LOOKING”, suggests as one would expect that they were being cut off as they were exposed by, first, the removal of the masonry pile cap above and, second, by excavation. Pulling a pile out of the ground is as difficult as driving one in, and why bother? Also, on the building behind the site, note the ghost joist pockets.
Here’s another view of the same day, showing the stacks of timber that will become the support of excavation. The timbers are square – probably 12 inches by 12 inches, but many have one end cut round. I’m not sure if that’s part of how they were connected or something else. The new wood is quite a bit lighter in color than the old piles seen just to the right of the word “LOT.”
And here’s a view a week later, when excavation has proceeded far enough for the first level of support-of-excavation timbers to be installed. Construction logistics always impresses me; building the three-dimensional grid of heavy timber seen in yesterday’s photos from the top down, while working between old piles and new caissons, is more impressive than most.