Doing any kind of utility work in NYC is a nightmare. There's lots of stuff underground (power, telecom, water, steam, sewer) that has been built up over the years and is in various states of obsolescence and disrepair, and in many cases isn't really marked on any utility maps. It's not a trivial matter to just dig a new trench for fiber.
... dangit, I wish I knew more about electrical work. Why was that so dangerous? I mean, besides 250 volts and rotted-out insulation. The writer makes it sound like he just discovered an unexploded bomb.
Good question! AC voltage is relatively safer because it crosses the zero point 120 times a second. If it passes through your body, your muscles will spasm but you will have an opportunity to pull away. Also, AC voltage will probably not sustain an arc at such a low voltage, again, because it is constantly switching polarity.
On the other hand DC voltage, once a connection has been made, will continue to flow through that path to complete the circuit. You can think of it as the electrons on the hot wire want very badly to get back to the place where they were generated (the source transformer under that covered up manhole). If they find a path through your body, it will continue to flow through your blood vessels until either you or the wire burns up, or the upstream transform faults. You basically become a fuse. If you are part of the circuit, you'd better hope there is somebody nearby to hit you you with a pole, because otherwise you are pretty much stuck that way. Also, DC voltage is much better at sustaining an arc, even below 100 volts, so it can set off an explosion that can ignite whatever dust is lying around the equipment. Google "arc flash" to see what this looks like.
> Also, DC voltage is much better at sustaining an arc, even below 100 volts, so it can set off an explosion that can ignite whatever dust is lying around the equipment
Ahh, that's what I was missing. I assume the "painted black" part was to insulate the box and mitigate this risk when the box was closed?
Here's a interesting story of what happened when an electrician found a 250VDC feed that was supposed to be abandoned decades ago: http://www.electriciantalk.com/f5/fixture-tails-44009/#post8...