At the moment I’m watching New York’s Mayor Michael Bloomberg conduct a press conference about a collapse in Upper Manhattan this afternoon.
A retaining wall holding back a steep hill gave way, allowing the hill to tumble onto the Henry Hudson Parkway and its access road. Debris was piled up at least 25 feet deep and you could see partially buried cars at the edge of the slide area. This all took place in the shadow of the George Washington Bridge.
I have driven by this particular spot dozens, maybe hundreds of times, over the years. It is a physically impressive part of Manhattan, because of the steep rise of the land adjacent to the Hudson River.
A little farther south of this site are buildings, seemingly perched on nothing but spindly columns. Their front entrances are at street level. The backs of the buildings are way above the ground. Underneath, the ground plunges away from the basement.
At the moment, it seems no one was injured. That’s pretty amazing considering the traffic this road handles (there’s actually significantly more traffic just south of the collapse where traffic can exit from the George Washington Bridge or Cross Bronx Expressway – I-95).
It’s possible the hill gave way slowly, or possibly in a few disjointed slides lead to the major crash at the end. It couldn’t be blind luck that no one was underneath.
From the photos I’ve seen, there are construction ‘canopies’ where the slide took place. Undoubtedly there was work going on – maybe trying to prevent what ended up happening.
In a situation like this, the most obvious culprit will be water. Unfortunately, there’s water seeping all over Manhattan. The water mains, some well over 100 years old, leak like crazy underneath the streets. No one really knows how much, but it’s substantial.
I heard the mayor say there might have been seepage from a park on the top of the hill. More will come out with time.
As a frequent driver in New York City I have seen other signs of water damage and seepage that have worried me in the past. Portions of the brickwork along the side of the Cross Bronx Expressway have eroded away. The mortar is still there, but much of the brick is gone.
Some underpasses show the same or similar problems. There looks to be water flowing and carrying away parts of the facade.
You always hope this damage is superficial, that New York City has a handle on it. Maybe not. Hopefully, this is a wake up call that the water has to be put under control and damage repaired.
One mile south, this same slide would have been a huge catastrophe. The potential would have been there for casualties in the hundreds, or more. Tonight it’s just a head scratcher.