If you’ve been by the site lately, then you’ve probably noticed the regular thrum, thrum, thrum of the rig pounding timber into the ground. No, it isn’t a crowd of Olympic enthusiasts stamping their feet in appreciation of the most recent gold medalist. Not special effect for a video set to Carole King’s ‘I Feel the Earth Move,’ nor a visit from King Kong. Just the regular, old business of construction. There’s no denying that pile driving is loud and causes the ground to shake, but the vibrations aren’t as bad as they might seem. According to a series of studies by the US Bureau of Mines, vibrations with a particle velocity below 0.5 inches per second are unlikely to cause damage to residential structures, regardless of the frequency character and duration of the vibration. Safe levels of ground vibration range from 0.5 inches per second to 2.0 inches per second peak particle velocity. (We don’t know what peak particle velocity means either but it is something like the maximum rate of change in a wave’s amplitude as a function of time.) Our vibration readings throughout pile driving have been within the allowable limit.

How do we know this? Find out below.

We have vibration monitoring at the site via multiple portable seismographs and a vibration consultant who calibrates, installs, watches, and reports on vibrations. The seismographs we are using are Instantel MiniMate Plus. According to the manufacturer, this seisomograph is useful for a wide variety of applications, from pile driving to underwater blasting. If we start approaching our trigger limit, the guy watching the seismograph alerts the site supervisor. So far we’ve not had high readings. If we did, then we might reconsider our use of timber piles. But back in May when we drove our first piles, we did vibration monitoring to see if the timber piles would result in significantly more vibration than the steel H piles. They did not, so we went with timber piles for the rest of the job which were significantly less expensive than the steel.

Our neighbors shouldn’t experience damage due to vibrations below the trigger, but we feel it’s wise to err on the side of caution. For example, we were a little concerned with the back patio of one neighbor. His patio walls and chimney used to rest on our structure, which we’ve demolished. It took some time but we finally secured his permission to add some temporary safeguards to this area (as pictured). At this point we have 91 piles in the ground and a little over half to go. With any luck, we’ll be finished before most people return from their August vacations. Or at least before the Michael Phelps DVDs hit the streets or has that already started?
Inside Third & Bond: Week 49 [Brownstoner]
Inside Third & Bond: Week 48 [Brownstoner]
Inside Third & Bond: Week 47 [Brownstoner]
Inside Third & Bond: Week 46 [Brownstoner]
Inside Third & Bond: Week 45 [Brownstoner]
Inside Third & Bond: Week 44 [Brownstoner]

From our lawyers: This is not an offering. No offering can be made until an offering plan is filed with the Department of Law of the State of New York.”