|They're coming from this (the pipeline, not the dog). Let me explain.|
Well, it's a black-coated pipe and during our hot summer days, it heats up considerably, expanding as it goes. Then at night, it cools down again and contracts. It weighs many tons, and is supported by oak dunnage pedestals spaced at regular intervals. In order to contract, the thing has to overcome a massive force of friction imposed by its own massive weight. As it shrinks bit by bit, the incrementally-released forces make a bizarre sound somewhere between a loud SNAP and a SPROING, and then the resulting shock wave proceeds to reverberate up and down the entire half-mile length of pipe. I can't say that I've heard anything quite like it before. It's a bit unnerving.
My husband did a back-of-envelope calculation and reckons that it probably needs to shorten itself at night and re-lengthen by day to the tune of 6 to 12 inches because of these temperature changes. Try sliding a half-mile heavy pipeline over structural supports by that amount of distance - it's going to make some noise.
Furthermore, the workers appear to be welding at break-neck speed such that, by this evening, it could be the better part of a mile long. Which probably means even more strange noise.
|That which was laid out in segments last night is now one continuous length, as they worked through Saturday on it.|