What specific regulation governs the permissible noise levels emitted by a tidal energy plant during pile driving operations to protect marine mammals?

In the United States, the specific regulation governing the permissible noise levels emitted by a tidal energy plant during pile driving operations to protect marine mammals is primarily dictated by the Marine Mammal Protection Act (MMPA) and its implementing regulations, along with guidance and permits issued by the National Marine Fisheries Service (NMFS). Pile driving generates high levels of underwater noise, which can harm marine mammals. The Marine Mammal Protection Act (MMPA) prohibits the "take" of marine mammals, which includes harassing, harming, injuring, or killing them. NMFS, a division of the National Oceanic and Atmospheric Administration (NOAA), is responsible for implementing the MMPA. NMFS issues regulations and guidance on how to minimize the impact of underwater noise on marine mammals. These regulations typically establish noise thresholds, known as acoustic thresholds, that must not be exceeded during pile driving operations. There are different acoustic thresholds for different types of marine mammals and for different types of noise. NMFS also requires tidal energy plants to obtain Incidental Harassment Authorizations (IHAs) or Letters of Authorization (LOAs) before conducting pile driving operations. To obtain an IHA or LOA, the tidal energy plant must submit a detailed application to NMFS that includes information about the project, the pile driving methods, the expected noise levels, and the mitigation measures that will be implemented to protect marine mammals. Mitigation measures may include the use of noise attenuation devices, such as bubble curtains or cofferdams, which reduce the amount of noise that is transmitted into the water. They may also include monitoring the area for marine mammals and halting pile driving operations if marine mammals are detected within a certain distance of the project. Other regulations such as the Endangered Species Act (ESA) may also apply if endangered or threatened marine mammal species are present in the area. Therefore, compliance with the MMPA, NMFS regulations and guidance, and the terms and conditions of any IHAs or LOAs is essential for ensuring that pile driving operations at tidal energy plants do not harm marine mammals.