How are the safety radii established and enforced?
The safety radii are based upon underwater sound contours, or isopleths. Approximate isopleths have been established at 190, 180, and 160 decibels from nearby pile driving activities. These isopleths were established during a test program of similar, but not exact, type of piles in a nearby location. These isopleths will be re-evaluated and adjusted during construction based upon actual measurements during construction. Safety zones will then be empirically determined and implemented. This safety zone is monitored during pile driving for the presence of marine mammals before, during, and after any noise generating activity. If the safety radius is obscured by fog or poor lighting conditions, the construction subcontractor is committed to cease all pile driving until the entire safety radius is visible.
