One of the permit conditions was that the piles were to be driven using a vibratory pile driver.
Driving a steel pile with a vibratory driver using a crane on a barge
This permit condition is the result of studies on water noise impacts to fish and sea mammals. The more typical hammer pile driving can generate intense noise pulses in the water that are intense enough to tear fish bladders and destroy the hearing of fish (Laughlin WSDOT, 2005 and 2010). Lots of piles are driven into water for docks and bridges. Hence, this issue is posing a challenge for in water works - think ferry docks, bridges, and marinas. Washington State Department of Transportation has studies using bubble curtains around piles to dampen noise with some success, but as always "more study" is needed. Lots of physics, biology and acoustics; reading the studies is a good brain work out and certainly a regulatory challenge.
Studies on hammer driving which is basically dropping a big weight on top of the pile to drive the pile versus vibratory driving indicate that the sound intensity and pulses are substantially lower for vibratory pile driving. Hence, the condition my client had on pile driving. The vibratory pile driving basically shakes the pile through the sediment. I was surprised how well it worked, but we were unable to drive through the old log road that had been constructed along the shoreline without moving the pile locations slightly.
Steel piles prior to dock and landing reconstruction. The two sheds are 100+ year old structures from old fishing days. Grassy area at the base of the slope was an old road bed as tide lands were the first "highways".