Noise Mitigation Systems for Offshore Wind Monopile Installation

 

​Noise Mitigation Systems for Offshore Wind Monopile Installation
The installation of monopiles for offshore wind turbines involves driving large steel piles into the seabed, a process that generates significant underwater noise. This noise can adversely affect marine life, particularly species sensitive to sound, such as marine mammals and fish. To address these concerns, several noise mitigation systems have been developed and implemented to minimize the impact on the marine environment.
Bubble Curtains: One of the most commonly used noise mitigation techniques is the bubble curtain. This system involves releasing a continuous stream of air bubbles around the monopile during installation. The bubbles create a barrier that disrupts and attenuates the sound waves, significantly reducing the noise levels that reach the surrounding waters. Bubble curtains can achieve a noise reduction of up to 20 decibels, providing a substantial decrease in the potential impact on marine life.
Acoustic Deterrent Devices (ADDs): ADDs are employed to temporarily deter marine mammals from the vicinity of the construction site. These devices emit sounds that encourage animals to move away from the area, thereby reducing their exposure to harmful noise levels.
Hydro Sound Dampers (HSDs): HSDs are specially designed to absorb and dissipate underwater noise. These systems consist of foam and plastic elements that are attached to the monopile, acting as a dampening layer to reduce sound transmission.
Cushioning Material: Using various types of cushioning materials between the hammer and the monopile can also help reduce noise. Materials such as synthetic mats or wooden blocks are placed at the contact point to absorb some of the impact energy, thereby lowering the noise produced.
Vibratory Hammers: In some cases, vibratory hammers are used instead of traditional impact hammers. Vibratory hammers install the monopiles by vibrating them into place, which generally produces lower noise levels compared to the percussive action of impact hammers.
Passive Acoustic Monitoring (PAM): PAM systems involve using hydrophones to monitor underwater noise levels and the presence of marine animals in real-time. These systems can detect and identify marine mammals and other species in the vicinity of the construction site, allowing for the adjustment of activities to minimize impacts. PAM is particularly useful for ensuring compliance with environmental regulations and for guiding the implementation of additional mitigation measures if needed.
Protected Species Observers (PSOs): PSOs are trained professionals stationed on construction vessels to monitor for the presence of protected marine species, such as whales, dolphins, and sea turtles. They are equipped with the authority to call for a temporary work stoppage if these animals are sighted within a designated exclusion zone. This immediate response capability ensures that marine life is not exposed to harmful noise levels, enhancing the overall effectiveness of the mitigation measures.
Rutgers Glider Program: An innovative approach to environmental monitoring, the Rutgers Glider Program utilizes autonomous underwater gliders equipped with sensors to collect data on oceanographic conditions and marine life. These gliders can provide valuable information on the presence and behavior of marine species, as well as the effectiveness of noise mitigation measures. By deploying gliders in areas of offshore wind development, researchers can gain insights into the environmental impacts of construction activities and adjust strategies accordingly to protect marine ecosystems.
Time and Area Restrictions: Implementing temporal and spatial restrictions on pile driving activities can also mitigate noise impacts. By avoiding construction during sensitive periods, such as breeding seasons, and in areas with high concentrations of marine life, the disturbance to the ecosystem can be minimized.
Offshore wind developers may choose to employ one or more of these methods during installation to effectively reduce noise impacts.
The integration of these noise mitigation systems into offshore wind monopile installations is essential for balancing the development of renewable energy with the protection of marine ecosystems. By continuing to innovate and refine these technologies, the offshore wind industry can sustainably expand while minimizing its environmental footprint.

NJDEP| Offshore Wind | Research and Monitoring Initiative (RMI)

NOAA Recommendations for Use of Passive Acoustic Listening Systems | NOAA Fisheries

---