A Monte Carlo approach to determining marine mammal exposure risk to long term marine piling operations

Abstract

The expansion of offshore renewable developments, primarily offshore wind, has led to widespread use of large scale percussive piling for foundation construction. In UK waters alone, over 900 foundations installed up to 2013, mostly mono-piles with extensive up-scaling of developments planned for the next decade. Pile diameters range from a few meters to greater than 6 m and penetration depths of 20–30 m. These piles are typically percussively driven with several thousand hammer strikes over periods of several hours with individual strike hammer energies in excess of 1900 kJ occasionally used and reported per strike underwater Sound Exposure Level source levels of 215 dB re 1 μPa2s-m2. Potential exists for injury to occur from cumulative sound exposure to repetitive but lower level signals at greater range. If simple receptor behaviors are assumed (static, fleeing, etc.) exposure over time to an entire pile construction sequence can be estimated. These models have been extended using a Monte Carlo approach to model long term, entire wind farm construction scenarios with repetitive foundation construction periods of 24–36 h. The statistical distribution of exposure risk is modeled as well as analysis of the sensitivity of behavioral responses to potential impact effects such as habitat exclusion.