Donnie says, "We now have an eerie addition to our nights.  Until the pipeline is buried, it is perched atop quite precarious-looking piles of railroad ties.  At night, when there are few other sounds out here, the steel pipes will occasionally generate a loud, echoing PING, like wind chimes.  The sound is rather pleasant, but it is so unnatural and unexpected that it's also rather creepy--puts us in the mind to look for space aliens.  I'm guess the rings are caused by the pipes settling on their supports, or the now-sudden and considerable temperature changes as the sun sets."