Bridge engineers should be aware that marine pile driving has resulted in high underwater sound pressures that have been lethal to fish and have resulted in harassment of pinnipeds under the Marine Mammal Protection Act. Most waterways in the nation include fish and marine mammals that are protected by state or federal agencies. Impacts from pile driving have contributed to costly construction delays for some major bridge projects. Recent construction activities in the marine environments of northern California have provided the opportunity to characterize these sound pressures and evaluate control measures to protect fish and marine mammals. Sound attenuation measures evaluated include different pile-driving methods, cofferdams (with and without water), confined air bubble curtain systems, and unconfined bubble curtain systems. Some attenuation measures have achieved more than 30 dB of noise reduction. However, each situation can present difficulties in achieving targeted reduction goals. Use of appropriate attenuation systems has greatly reduced the impacts to the species of concern for those projects. In this study, recent experiences are summarized from many projects in measuring both attenuated and unattenuated underwater sound pulses from pile-driving activities.
Samenvatting