Regulatory Policy

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.

Policy and Regulation

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 develop the Operational National Mitigation Protocols which delineate 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.

ElementsTier 1Tier 2Tier 3 1Tier 4
Sources
  • Airgun arrays > 1,500 in3 or any array with > 12 airguns
  • Ultra Low Frequency Pneumatic Sources such as HarmonyTM
  • Airgun arrays ≤ 1,500 in3 or ≤ 12 airguns
  • Ultra Low Frequency Pneumatic Sources such as Gemini SourceTM and Tuned Pulse SourceTM✝
  • High-energy✝✝ Marine Vibroseis Sources
  • Sparkers
  • 1 and 2-plate boomers
  • Bubble guns
  • Medium-energy✝✝✝ Marine Vibroseis Sources
  • De minimis sources (see below)
Visual Protected Species Observers (PSO)2Minimum 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 periodMinimum 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 periodMinimum 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 NMFSNot required
Passive acoustic monitoring (PAM)Required3; 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 periodNot required
Shutdown zones
  • 500 m (all marine mammals)
  • 1,500 m (special circumstances*)
  • 150 m (sea turtles)
  • 100 m (all marine mammals and sea turtles)
  • 500 m (special circumstances*)
Not required
Pre-start clearance (additional buffer zone as applicable)

Required; 30 min clearance period of the following zones:

  • 1,000 m (all marine mammals)
  • 1,500 m (special circumstances*)
  • 150 m (sea turtles) Following detection within zone, animal must be observed exiting or additional period of 15 or 30 min

Required; 30 min clearance period of the following zones:

  • 200 m (all marine mammals)
  • 100 m (sea turtles)
  • 500 m (special circumstances*) Following detection within zone, animal must be observed exiting or additional period of 15 or 30 min

Required; 30 min clearance period of the following zones:

  • 100 m (all marine mammals and sea turtles)
  • 500 m (special circumstances*) Following detection within zone, animal must be observed exiting or additional period of 15 or 30 min
Not required
Ramp-upRequired; duration ≥ 20 minRequired for arrays only; duration dependent on number of elements; no minimum duration requiredRequired when technically feasible; ramp up sources to half power for 5 min and then to full powerNot required
ShutdownShutdown 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 Sources that involve near-simultaneous firing of multiple elements require additional evaluation and may fall into Tier 1. 
2 Those with a 60-second SEL comparable to that of Tier 2 airguns and airgun arrays. 60-second SEL is defined in Caplinger et al. 2026. 
3 Medium-energy is defined as sources with a 60-second SEL less than Tier 2 airguns and airgun arrays. Examples include single and dual element MV JIP IPN and dual element SAE Triton. 
4 A MMPA incidental take authorization is not required for Tier 3 surveys implementing these protocols. 
5 24-hr visual monitoring may be required as warranted by improvements in low-light detection capabilities. 
6 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 include endangered species like the North Atlantic Right Whale, whales with calves, and groups of large whales. 

Tier 1:
  • Airgun arrays with total volume greater than 1,500 in3 or any array with more than 12 airguns
  • Ultra Low Frequency pneumatic sources such as the 6,000 in3 HarmonyTM
Tier 2:
  • Airgun arrays with total volume less than or equal to 1,500 in3 and 12 airguns or fewer; single airgun
  • Ultra Low Frequency pneumatic sources such as the 8,000 in3 Gemini SourceTM and 28,000 in3 Tuned Pulse SourceTM; sources that involve near-simultaneous firing of multiple elements require additional evaluation and may fall into Tier 1
  • High-energy Marine Vibroseis sources; those with a 60-second SEL comparable to that of Tier 2 airguns and airgun arrays. 60-second SEL is defined in Caplinger et al. 2026.
Tier 3:
  • Sparkers
  • 1- and 2-plate boomers
  • Bubble guns
  • Medium-energy Marine Vibroseis sources. Medium-energy is defined as sources with a 60-second SEL less than Tier 2 airguns and airgun arrays. Examples include single and dual element MV JIP IPN and dual element SAE Triton.
  • Other sources not yet evaluated
Tier 4:
  • De minimis sources. Examples of de minimis sources include:
    • MV sources for which incidental take is unlikely
    • 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
    • Wolfspar
    • All instruments operated at 180 kHz or greater

References:

For analyses supporting the tier delineations above, see Ruppel et al 2022 and Caplinger et al 2026

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