The CMA aims to strengthen BOEM’s role as a driving force within the regulatory community by making key policy and management improvements, both internally and externally. We do this by: driving best practices, research, and scientific rigor; encouraging innovation while championing consistency, standardization, and efficiency where needed; and partnering strategically with external organizations, both domestic and international, to achieve what cannot be done alone.
Tiering of Acoustic Sources
BOEM has worked with partner agencies to identify four tiers of acoustic sources based on their potential to affect marine life. BOEM, the Bureau of Safety and Environmental Enforcement, and the National Marine Fisheries Service worked together to recommend the appropriate level of mitigation required for each tier (list below).
BOEM employed a science-based approach to determine which sources belong in each tier. The bureau also worked with experts from industry, academia, and federal partners to compile information about the characteristics of each source.
| Elements | Tier 1 | Tier 2 | Tier 3 2 | Tier 4 |
|---|---|---|---|---|
| Sources | Airgun arrays > 1,500 in3 or any array with > 12 airguns | Airgun arrays ≤ 1,500 in3 or ≤ 12 airguns | Sparkers | De minimis sources (see below) |
| Visual Protected Species Observers (PSO)3 | Minimum of 2 NMFS- approved PSOs on duty during daylight hours (30 min before sunrise through 30 min after sunset); Limit of 4 consecutive hrs on watch followed by a break of at least 1 hr; Maximum of 12 hrs on watch per 24-hr period | Minimum of 2 NMFS- approved PSOs on duty during daylight hours (30 min before sunrise through 30 min after sunset); Limit of 4 consecutive hrs on watch followed by a break of at least 1 hr; Maximum of 12 hrs on watch per 24-hr period | Minimum of 1 PSO on duty during daylight hours (30 min before sunrise through 30 min after sunset); PSOs must be either designated by the Federal agency funding/conducting the survey or approved by NMFS | Not required |
| Passive acoustic monitoring (PAM) | Required4; minimum of 1 NMFS-approved PAM operator on duty from 30 min before start of source to 1 hr past the end of source use; Limit of 4 consecutive hrs on watch followed by a break of at least 1 hr; Maximum of 12 hrs on watch per 24-hr period | Not required | ||
| Shutdown zones |
|
| Not required | |
| Pre-start clearance (additional buffer zone as applicable) | Required; 30 min clearance period of the following zones:
mammals)
| Required; 30 min clearance period of the following zones:
mammals)
| Required; 30 min clearance period of the following zones:
mammals and sea turtles)
| Not required |
| Ramp-up | Required; duration ≥ 20 min | Required for arrays only; duration dependent on number of elements; no minimum duration required | Required when technically feasible; ramp up sources to half power for 5 min and then to full power | Not required |
| Shutdown | Shutdown required for marine mammal detected within defined shutdown zones; Shutdown (i.e., pause) not requiring ramp-up for sea turtles detected within defined shutdown zones (during Tier 3 surveys, shutdown [i.e., pause] for sea turtles is optional); Exception for certain delphinids and pinnipeds; Re-start allowed following clearance period of 15 or 30 min. | Not required | ||
1 Agencies responsible for the preparation of these protocols include NOAA’s NMFS, BOEM, and BSEE. The DOI’s U.S. Geological Survey and the National Science Foundation provided input. Requirements for notifications, reporting, etc. to BOEM and/or BSEE are limited to activities occurring pursuant to those agencies’ relevant statutory and regulatory authorities.
2 A MMPA incidental take authorization is not required for Tier 3 surveys implementing these protocols.
3 24-hr visual monitoring may be required as warranted by improvements in low-light detection capabilities.
4 PAM is not required for Tier 1 surveys occurring in Cook Inlet or in water depths < 100 m in the Gulf of America. Borehole seismic surveys (also referred to as vertical seismic profiles [VSP]) involving use of a stationary source position that is close to the well (e.g., deployed from a platform), such as zero-offset VSPs, are not required to use PAM.
*special circumstances includes highly endangered species like the North Atlantic Right Whale, whales with calves, and groups of large whales.
BOEM employed a science-based approach to determine which sources belong in each tier. The bureau also worked with experts from industry, academia, and federal partners to compile information about the characteristics of each source.
Tier 1:
Airgun arrays with total volume greater than 1,500 in3 or any array with more than 12 airguns
Tier 2:
Airgun arrays with total volume less than or equal to 1,500 in3 and 12 airguns or fewer; single airgun
Tier 3:
Sparkers, 1- and 2- plate boomers, bubble guns, and other sources not yet evaluated by Ruppel et al 2022.
Tier 4:
De minimis sources. Examples of de minimis sources include:
- Multibeam echosounders (hull-mounted or portable)
- Side-scan and sector-scanning sonars
- Hull-mounted non-parametric sub-bottom profilers (SBPs) (e.g., Knudsens)
- Parametric shallow penetration SBPs (e.g., Innomars)
- Fathometers for navigation
- Towed non-parametric SBPs/Compressed High-intensity Radiated Pulse (Chirp) systems (e.g., Edgetech 424, Edgetech 512i)
- EK60/EK80 split-beam echosounders
- 3-plate boomers
- Pingers (acoustic locators) for locating over the side wireline instrumentation in the water column
- Acoustic releases (brief duration pinging), e.g., for moorings, landers, OBS
- Ultra-short baseline (USBL) and long baseline (LBL) positioning equipment, e.g., for navigation of submersibles, remotely operated vehicles (ROVs), etc.
- All Acoustic Doppler Current Profiling (ADCP) equipment
- All instrumentation on human occupied vehicle (HOV), autonomous underwater vehicle (AUV), or ROV
- Pressure-equipped inverted echo sounders (PIES) and Pressure Monitoring Transducers (PMTs)
- Electromagnetic sources
- Wolfspar7
- All instruments operated at 180 kHz or greater
Any additional sources that have similar source level, directivity, or frequency characteristics as those already included here may be included in Tier 4.
References:
For the analysis of seismic airguns and high-resolution geophysical sources, see Ruppel et al 2022.
Other Topics the CMA is Advancing
- Establishing performance targets for quieting of several sound types
- Bringing new approaches for setting acoustic thresholds
- Improving sound field verification
- Integrating the risk assessment framework into the decision-making process
- Addressing complex noise issues
- Determining requirements for acoustic monitoring of critical minerals sites