When I drove home yesterday afternoon, I was stopped just before reaching my driveway by an enormous crane in the road, which you can see to the left. The road was also covered with tree limbs, although workers quickly gathered them up and fed them into a large chipper, eventually allowing me to pass. I then took the pictures shown in this entry.
I asked the homeowner, my neighbor across the street, why the trees were being taken down. He said that one of the trees was threatening to fall on a nearby shed. It was the only one that really needed to be removed, but once all the equipment was brought in, it seemed reasonable to take down two additional trees which might become a problem in the future.
I've had trees taken down on my own property, but the operation was generally quite a bit simpler than this one. Previous tree removals I've witnessed used a "cherry picker" to carry a worker up into the tree with a chainsaw. He lopped off the limbs, leaving a bare trunk, which he then took down in pieces, starting from the top.
The operation I watched yesterday, however, involved quite a few more workers, and quite a few more pieces of equipment. There was indeed a "cherry picker", also called a "bucket truck". The operator of the crane lowered a cable to the worker in the bucket, who tied it to the top of the tree. He then moved the bucket down to cut the tree off at a lower point, leaving it dangling from the crane. I assume that the crane operator pulled up on his cable, so that the weight of the treetop would not bear down on the saw's chain.
Once cut off, there might be 10 meters or so of tree dangling from the crane. The crane operator swung it around to the road, and lowered it to the ground. There, a smaller piece of equipment called a "Bobcat" was used to move it into position. Bobcats are frequently used for earthmoving, using a large shovel blade.
But this Bobcat had an apparatus attached specifically designed for gripping logs. The operator was able to grip the bottom of the treetops being lowered, and pull them backwards towards the chipper. Simultaneously, the crane operator lowered the top of the cut section, leaving the treetop lying horizontally on the ground. Four workers on the ground with chainsaws then cut off the limbs, to be fed into the chipper.
The trunk of the treetop might also be fed into the chipper it was small enough. But as the process worked down the tree, larger and larger logs were produced. The Bobcat, with its grippers, was used to stack these (there's a photo below), presumably to be removed later (although as I write this a day later, they are still there).
All of this was done in fairly confined quarters. There was a house nearby, and the afore-mentioned shed. The wires that ran along the far side of the street included high-voltage lines carrying 7,900 Volts, and power and telephone lines ran nearby to the house. One false step could have done quite a bit of damage. But the equipment operators worked in coordination, placing long heavy tree sections exactly where they wanted them, with great precision.
The operation required five pieces of heavy equipment: the crane, the bucket truck, and the Bobcat (each with an operator), plus the chipper and a dump truck to remove the chips. The dump truck filled up at one point, drove off with its load, and a second dump truck arrived to replace it. An additional four men used chainsaws to cut up the trees once they were on the ground, and fed the lopped off branches into the chipper.
Here are some additional pictures of the operation: