SURTASS LFA

Q-1: Why is the Navy considering a new sonar system?

A: The new Surveillance Towed Array Sensor System (SURTASS) Low Frequency Active (LFA) system is essential to the Navy’s anti-submarine warfare efforts. The passive part of the system (SURTASS) uses a string of underwater hydrophones that are towed behind a ship to listen for sounds in the ocean produced by submarines. The system also uses active low frequency (LFA) transmissions to listen for reflections of sounds off submarines that are too quiet to hear with a passive system alone. By using specialized signals and echo detection, the system increases the distance at which submarines can be detected and tracked. Only low frequency active sonar can provide this kind of long-range submarine detection.

Q-2: What is the Navy doing to protect marine life?

A: The Navy has made a tremendous effort to ensure that the low frequency active (LFA) system does not pose a risk to marine life. Here are some of the steps that have been taken to mitigate biological risk and keep the potential for harmful effects at a negligible level:

The system is being developed in compliance with the National Environmental Policy Act and Presidential Executive Order 12114.
An independent Scientific Working Group was established in 1997 to recommend research priorities and to assess the research for environmental implications.
A $10 million, three-phase Scientific Research Program (SRP) studied behavioral responses to low frequency sound (LFS) by baleen whales off California and Hawaii. The principal investigators had two decades of experience with this kind of research, and had published authoritative studies documenting whale responses to noise.
Quantitative modeling of animal movements and acoustical exposure was conducted to estimate the environmental impact of deployment of the low frequency active system.
Concurrent studies and research were conducted to ensure that the system would not harm humans who were diving in the ocean.
An independent scientific team reviewed and edited the Environmental Impact Statement.
Monitoring and mitigation programs have been put in place to minimize the risk of harm to any marine mammal from the proposed low frequency active system.

Q-3: How did the Navy decide that the deployment of SURTASS LFA sonar will not significantly affect the marine environment?

A: This question addresses two issues. What facts and logical deductions were used to reach this conclusion (see Question 11), and what was the public process that led to the decision.

Under the National Environmental Policy Act (NEPA) the Navy is required to prepare an environmental impact statement (EIS) for actions that may significantly affect the quality of the human and natural environment.

The EIS must provide full disclosure of significant environmental impacts and inform decision-makers and the public of reasonable alternatives, including the No Action Alternative. The EIS must identify all potential direct and indirect effects that are known, and make a good faith effort to explain the effects that are not known but are “reasonably foreseeable.” This includes the Navy’s responsibility to make informed judgments, and to estimate the potential for future impacts on that basis, especially if trends are ascertainable. However, the Navy is not required to engage in speculation or contemplation about future plans that could influence the EIS’s analysis of potential direct and indirect effects.

The Navy’s Draft and Final Environmental Impact Statements (EIS) for Surveillance Towed Array Sensor System Low Frequency Active (SURTASS LFA) Sonar were filed with the US Environmental Protection Agency and made available to the public in July 1999 and January 2001, respectively.

On 23 July 2002, the Navy published the notice of Record of Decision (ROD) for Surveillance Towed Array Sensor System Low Frequency Active (SURTASS LFA) Sonar in the Federal Register (Vol. 67, No. 141) (Click Here to link to the ROD in the Federal Register). The ROD is a concise public record in which the Navy states what the decision is, identifies the alternatives considered, specifies the most environmentally preferable alternative, and states whether all practical means were adopted to avoid or minimize environmental harm. Based upon review of the comparative analysis of the potential for environmental and socioeconomic effects from the three alternatives presented in the Final OEIS/EIS and public comments received during the NEPA process, the Deputy Assistant Secretary of the Navy (Environment) decided to implement Alternative 1 of the Final OEIS/EIS, which requires certain geographical restrictions and monitoring mitigation designed to reduce potential adverse effects on the marine environment. This decision completed the NEPA process.

Q-4: Has the Navy responded to concerns of citizens that SURTASS LFA sonar may be harmful to marine life?

A: The Navy organized nine public outreach meetings and ensured that experts on Navy operations, marine mammals, and diver safety were present to answer questions. The Navy also participated in three public hearings on the National Marine Fisheries Service (NMFS) Proposed Rule and participated in three public scoping meetings and three public hearings on the EIS.

Every public comment was scrutinized by a group of scientists to determine if it raised an issue that had not been considered in the development of the EIS. One citizen’s comment precipitated the development of the High Frequency Marine Mammal Monitoring (HF/M3) sonar to detect marine mammals before they got close enough to the LFA array to risk injury. Concerns raised by scuba divers were addressed by an extensive study of human reactions to the LFA signal.

Q-5: Is the Navy proposing to waive environmental laws in order to deploy this new sonar system?

A: On the contrary, under the National Environmental Policy Act (NEPA) the Navy undertook a five-year Environmental Impact Statement (EIS) process (the first for a sea-based operational system). It included an at-sea Scientific Research Program (SRP) to fill data gaps on how low frequency sound (LFS) affected free-ranging marine mammals. Some of the country's top marine mammalogists and bioacousticians planned and executed this $10 million, three-phase SRP off California and Hawaii. The Navy will operate the SURTASS LFA system under a permit issued by the National Marine Fisheries Service (NMFS), and will regularly consult with NMFS to review the data collected as part of the mitigation protocol and Long Term Monitoring Program.

Q-6: What about the deaths of whales in the Bahamas in March 2000?

A: The SURTASS LFA sonar has not been used since April 1998, and no other low frequency sources were in use in the Bahamas in March 2000. An extensive review of the Smithsonian marine mammal stranding database has shown that no stranding can be associated with any of the early development or training exercises in which LFA was used.

NOAA Fisheries and the Navy are continuing to investigate the cause of this stranding. This response will be updated as soon as those investigations are completed.

Click HERE to read the Joint Interim Report - Bahamas Marine Mammal Stranding Event of 15-16 March 2000.

Q-7: What about reports that this system will affect 80 percent of the world’s ocean area?

A: The total ocean area that would be available for LFA training operations includes about 75 percent of the world's oceans. But this does not mean that 75 percent of the world's ocean area will be affected. The current plan is for two vessels to have this sonar system, one in the Atlantic, the other in the Pacific. Each vessel would be underway at sea for up to 270 days per year, each moving at only 3 knots, transmitting less than 20 percent of the time.

The EIS covers up to four systems, but even if all four were operational, rarely would more than two be at sea at once. If the Navy were to deploy more than four systems, another EIS process would be required.

Q-8: Are there still “secret” aspects to the proposed system?

A: Almost all technical aspects of the SURTASS LFA sonar system have been declassified. The Navy is striving to comply with all environmental laws and make the EIS process as open as possible within the bounds of national security.

Q-9: Is it true that the proposed system will generate sound in the range of 235 dB, which could cause hearing loss, serious injury, or even death to whales and other marine mammals?

A: The LFA system has 18 projectors, or sound sources, each capable of transmitting sound at a level of approximately 215 dB between 100 and 500 Hz. Because it is an array, if one looks at LFA from a distance, it will appear to have an “effective source level” on the order of 230 to 240 dB. However, in the actual water column, no portion of the ocean will experience sound levels greater than 215 dB.

Q-10: What are the potential effects that low frequency sound may have on marine mammals?

A: Marine mammals may change their behavior whenever they perceive any type of underwater low frequency sound and injury can occur at very high levels. Some changes in behavior may be too short or subtle for our best observations to detect. Other changes can be detected, but they may have no significant impact on the behavior of the animals. For the purposes of the EIS, behavioral risk was assessed in terms of its likely impact on survival or reproduction. The potential for injury exists at very high received levels. This risk is confined to a relatively small area very close to the LFA vessel.

Q-11: What has been done to evaluate the potential effects that the proposed sonar system will have on marine mammals?

A: To determine the potential effects of the system, the Navy funded several projects:

A thorough review of the scientific literature to summarize present knowledge and identify gaps in the data
Scientific screening of marine animal species for potential sensitivity to low frequency sound
Scientific research into the effects of low frequency sound on the species of marine mammals believed to be most at risk
Development of a model that relates acoustic exposure to risk of biologically significant impacts
Quantitative acoustic modeling of acoustic propagation and animal movements in relation to plausible deployments of SURTASS LFA sonar
Estimation of marine mammal stocks potentially affected
Establishment of mitigation to minimize impact and monitoring to measure the potential effects of operations.

Q-12: What operational restrictions (mitigation measures) will be implemented to protect marine animals?

A: The Navy has developed complex and costly measures to minimize risks to marine mammals. These measures are intended to detect animals within a range of approximately two kilometers of the source vessel. These reduce the chances that any animal would experience received levels greater than 180 dB to close to zero. The mitigation measures include:

Visual monitoring - daytime observations for marine mammals and other protected species, such as sea turtles, from the vessel by personnel trained in detecting and identifying these species
Passive acoustic monitoring - the SURTASS towed horizontal line array (the passive or “listening” part of the system) will be used whenever the low frequency active system is transmitting to detect vocalizing marine mammals
Use of a high frequency (HF) active sonar - operating like a “fish finder.” This high frequency sonar will help detect marine mammals that approach the system prior to and during operating periods.

Additionally, geographic restrictions to operations apply to areas within 22 kilometers (12 nautical miles) of any coastline, designated offshore biologically important areas, and known recreational and commercial dive sites.

Q-13: Is it true that the Scientific Research Program (SRP) was not a representative scientific study of the impact on marine mammals because the sound levels of testing were below those of actual planned system use?

A: A guiding principle for the SRP was that no experimental animal would be exposed to sounds in excess of 155 dB. This was agreed upon after consultation with the National Marine Fisheries Service, which issued the permits for the experiments.

In practice, it proved difficult to realize a received level of 155 dB for the experimental animals, even when the full source power of the LFA system was used (as it was during portions of Phase I). Subsequent modeling has proven that the overwhelming majority of animals would never be exposed to LFA received levels in excess of 155 dB even during full-power operations.

Q-14: Is it true that the SRP did not study impacts from received levels from 155 to 180 dB?

A: None of the experiments with free-ranging animals during the SRP generated exposure levels in excess of 155 dB. In order to account for this data gap, the Navy has assumed that risk increases quite rapidly at exposed levels above 155 dB, reaching a value near 100% at 180 dB.

Q-15: Why did the SRP only study four species of whales?

A: It is impossible to conduct studies on all marine animal species. Four mysticete species of whales (blue, fin, gray, and humpback whales) were selected for study because:

They are considered to have the best hearing in the low frequency band of all marine mammals
These species have protected status under the law
There is prior evidence that these species react to low frequency sounds

The SRP was designed such that responses of these representative species to low frequency sound signals would serve as indicators for responses of other potentially low frequency-sensitive species, which should be less vulnerable to low frequency active system signals.

During SRP Phases I and III, all other marine mammal species in the study area were observed from the LFA vessel. During Phase I, aerial surveys were also used to monitor all marine mammal species. Protocols were in place to suspend the experiments if any dramatic responses were detected. These data have been analyzed to look for changes in the numbers and distribution of these species during the course of the experiments.

Q-16: Is it true that during Phase III of the SRP conducted off Hawaii, whale-watch boat captains reported humpback whales disappearing from the testing area as soon as the broadcast began?

A: Some whale watch captains did assert that they observed a premature decrease in the number of humpback whales. This assertion was tested by comparing the quantitative measures of abundance from the SRP shore station with identical measures made during previous years of study. The pattern of abundance observed during LFA Phase III was completely consistent with the historical record. The decline in humpback numbers reflected the normal seasonal pattern of migration.

Q-17: What about theories that the new sonar system will affect migration of whales?

A: SRP Phase II and prior studies of migrating gray whales indicate that whales avoid a low frequency sound source that is in their path, and resume migrating on their historical route within a few kilometers.

During SRP Phase II, a significant new result was that this deviation only occurred when the source was located in the middle of their migration route (source at 2 km from shore). Gray whales in the same migration corridor did not appear to react to the LFA source transmission when it was outside the corridor (4 km from shore), even though the source level was adjusted so that the migrating whales’ received sound levels were the same.

Whales tend to swim closer to the surface during migration than during other activities. This diminishes their exposure to LFA, because low frequency sounds are attenuated near the ocean surface. These facts suggest that whales migrating in the open ocean would not be adversely affected by LFA operations. LFA will never be operated within 22 km of the coast and, therefore, not in the path of whales that migrate near shore.

Q-18: Are there potential long-term impacts from the Navy’s SURTASS LFA sonar system that could affect the behavior and viability of entire populations of marine mammals and push endangered species into extinction?

A: Exposure to LFA is intermittent because of the short duration of each mission and the low duty cycle of the transmissions. It is unlikely that many LFA missions would be scheduled in exactly the same place. Therefore, the potential for cumulative impact seems modest.

The SRP analyses looked for cumulative effects during the three phases of experiments, which were approximately the same duration as a normal LFA operation. No evidence of cumulative effects was found. Nonetheless, the Navy and NMFS have agreed on monitoring protocols and have planned long-term research to investigate this issue further.

Q-19: What will be done to protect human divers?

A: The Navy has conducted a comprehensive, scientifically-based research program on the potential effects of low frequency sound on human divers. Medical doctors and clinical researchers have carried out extensive computer modeling and testing of human and animal subjects. (All testing was done within the guidelines for the protection of human subjects and standard ethical procedures for animal experiments).

Based on the data obtained from these studies, the Navy Bureau of Medicine and Surgery (BUMED) incorporated a safety margin and established a conservative limit of 145 dB for low frequency received sound level for recreational and commercial divers. The mitigation measures proposed in the EIS will ensure that no recreational or commercial diver, or known dive site, will be exposed to levels of sound above 145 dB.

Q-20: Will the Navy’s new sonar system create additional noise in the ocean?

A: When deployed and transmitting, SURTASS LFA sonar will add to the ambient noise levels of the ocean, but the benefit to national security that SURTASS LFA sonar provides far outweighs the infinitesimal and intermittent addition of oceanic sound from the system’s operation.

Currently, commercial shipping is the dominant source of man-made, low frequency noise in the sea. If two LFA systems were fully deployed, maximum transmission time would be 864 hours, or 36 ship-days per year, compared with 22 million ship-days per year for commercial shipping.

Seismic survey efforts also contribute more noise to the ocean than LFA, as do many natural sources of low frequency sound, including lightning strikes, earthquakes, volcanic eruptions, and baleen whales.

Q-21: Won’t whales be at risk from this new form of low frequency sound?

A: It is unlikely that the LFA sounds will ever be the loudest low frequency sounds any whale will experience in its lifetime. Each year the earth’s oceans experience numerous lightning strikes at levels up to 260 dB. There are billions of lightning strikes hitting the ocean per year. Seafloor volcanic eruptions have source levels of 255 dB. Many baleen whales can create sounds at levels above 180 dB. These low frequency sounds have been present during the entire evolutionary history of marine mammals, and their physiological and behavioral systems have adapted to function in this environment.

The Scientific Research Program (SRP) investigated the possibility that there could be something in the structure of the LFA signal that posed a special risk for behavioral disruption in marine mammals. Although some responses were measured, none of the responses indicated a potential for the disruption of biologically important activities.

Q-22: Is the Navy working on another system of submarine detection, other than the use of low frequency active sonar?

A: As analyzed in the EIS, the only technology (acoustic or non-acoustic) capable of providing reliable, long-range detection of today’s quieter, harder-to-find submarines is low frequency active sonar. The Navy is developing new passive sonar technology, such as Advanced Deployable System (ADS) and Twin Line SURTASS; but even with these upgrades, passive sonar systems will not be sufficient to meet the needed long-range detection requirements that only LFA can provide.

When the Navy is attempting to locate submarines, the priority is to detect the target passively at distances far enough away so that the submarine is outside of its effective weapons range. When a ship uses active sonar, the active “ping” gives away the ship's position, which can be lethal if an enemy submarine is lurking within its weapon's range when it hears the ping. So, the Navy will only use active sonar when passive alone will not meet its ASW needs. This can occur when the acoustic “signature” of the target cannot be heard over the din of the surrounding noise in the ocean. In this circumstance, the use of active sonar is the only viable alternative.

Q-23: Can air space resonance produced by SURTASS LFA sonar cause tissue damage and inflict injury on marine mammals?

A: The concept that resonance will increase stress on tissue to the point of damage is in reality two separate concepts: resonance and tissue damage. Cudahy and Ellison (2002) (Click HERE to read the paper) state that resonance does not equal damage and damage is not always linked to resonance. So the issue is not resonance in air/gas cavities, but tissue damage, whether it is caused by resonance or by other means. The potential for in vivo tissue damage to marine mammals from exposure to underwater LF sound will not occur at a level less than 180 to 190 dB (Cudahy and Ellison, 2002). This includes: (1) Transluminal (hydraulic) damage to tissues at intensities on the order of 190 dB or greater; (2) Vascular damage thresholds from cavitation at intensities in the 240-dB regime; (3) Tissue shear damage at intensities on the order of 190 dB or greater; and (4) Tissue damage in air-filled spaces at intensities above 180 dB.

Therefore, unless an animal is within the 180-dB SURTASS LFA sonar mitigation zone, there should be no physical damage to body systems or tissues, either with or without resonance. Because of the mitigation measures, the probability that a marine mammal will be detected in the 180-dB LFA mitigation zone is close to 100 percent. Consequently, the potential impact to any marine mammal stock from injury is considered negligible.