Statement of Canadian Practice with respect to the Mitigation of Seismic Sound in the Marine Environment
Statement of Canadian Practice with respect to the Mitigation of Seismic Sound in the Marine Environment (PDF, 388 KB)
Recent years have seen a heightened interest in the potential impacts of seismic surveying on the marine environment. In 2004, federal and provincial government advisors, and national and international scientific experts met to review the body of scientific knowledge that exists in this area. A review of the most effective and appropriate mitigative measures used world-wide was also conducted. These reviews led to the identification of a set of mitigation measures, which can assist in minimizing the potential adverse impacts of marine seismic activity. Federal and provincial governments have compiled these mitigation measures into the Statement of Canadian Practice with respect to the Mitigation of Seismic Sound in the Marine Environment. The Statement sets out minimum standards which will apply in Canada’s non-ice covered marine waters to all seismic activities that use air source arrays. It will complement the existing environmental assessment processes, including those pursuant to settled land claims, and the existing regulatory requirements that currently govern marine seismic activities. Recognizing that the body of scientific knowledge is continually expanding, the Statement will be regularly reviewed. As new scientific information and improved mitigation technologies and practices emerge, these will be considered for incorporation into the Statement.
SOUND IN THE OCEANS is generated by a variety of natural sources, including vocalisation by marine life as well as wind and wave action, ice movements, and meteorological and oceanographic conditions.
Human activity also contributes to sound in the marine environment. Activities such as navigation, dredging, pile driving, ice breaking, whale watching and operating fishing gear each produce sound patterns with distinct characteristics. Resource exploration and production activities, including offshore drilling and marine seismic surveying, produce different types of sound. Active sonar which is used by security and defence operations produces a distinct type of sound.
There are fundamental differences between the type and intensity of sound generated by seismic air source arrays and sound associated with active sonar. These differences are mainly due to the emission of sounds of different intensity, frequency and direction of transmission.
Oceanographic characteristics such as the physiography of the sea bottom, the water depth, temperature, salinity and density differences can influence the transmission of sound as it travels through water. For example, sound levels are quickly reduced in shallow waters. In deeper waters, sound is likely to propagate further, especially where acoustic channels exist to conduct and focus sound energy.
In recent years, considerable international effort has been dedicated to a better understanding of the generation and transmission of sound in the marine environment and of the potential impacts of marine sound on life in the oceans. One area that has been of particular interest to the Canadian public is the sound associated with conducting marine seismic surveys.
SEISMIC SURVEYS use sound waves to gather information about geological structures lying beneath the surface of the earth, both on land and in the marine environment. A common purpose for conducting seismic surveys is to locate rock formations that could potentially contain hydrocarbons. Seismic surveys are also conducted by government and academic researchers for general scientific purposes, to understand the composition, structure and movement of the earth’s crust.
During marine seismic surveys, compressed air is released into the water column, creating a sound energy pulse. The pulse is “focused" to concentrate the sound energy toward the ocean bottom rather than horizontally. These surveys are carried out from a ship that tows a sound source or sources, referred to as “air source arrays", and one or more cables (“streamers") that contain sound receivers and other instruments.
The sea floor and the structures beneath it are mapped by measuring the time it takes for a sound energy pulse to leave the source, penetrate the earth, reflect off a subsurface layer, and return to a sound receiver. Reflections occur at each layer where there is a measurable change in the speed at which sound is transmitted. The data retrieved from these surveys provides information on depth, position and shape of underground geological formations.
Most seismic surveys conducted in Canadian marine waters fall into the category of two-dimensional (2D) surveys or three-dimensional (3D) surveys. The objective of a 2D survey is to provide a broad picture of the geological characteristics of an area, including type and size of structures present. In conducting a 2D survey, a seismic vessel typically tows a single air source array and a single set of receivers along a set of parallel and transverse lines, spaced up to five kilometres apart, to create a grid pattern. A 3D seismic survey is conducted over a smaller area, to obtain more detailed geological information and to identify potential targets for hydrocarbon drilling. 3D surveys also create a grid pattern, but generally use two or more air source arrays and multiple sets of receivers trailed closer together.
THE POTENTIAL IMPACTS OF SEISMIC SOUND ON MARINE LIFE have been studied internationally for decades. Biological impacts on marine life from seismic surveys are generally discussed in terms of:
- physical impacts, or changes in organisms’ physical state;
- physiological impacts, or changes in biological functions; and
- behavioural impacts, or changes in how organisms act.
In 2004, governments and academic researchers set out to take stock of our scientific knowledge in these areas. The process, which was led by Fisheries and Oceans Canada, culminated in a scientific peer review process involving national and international scientific experts. It considered the most current evidence of physical and physiological impacts of seismic sound on marine life, as well as potential behavioural impacts, and whether those impacts were direct, indirect, chronic or cumulative. The peer review process drew a number of conclusions using a risk-based approach that considered the likelihood of occurrence, the frequency and duration of the impact and the ecological significance or severity of the impactFootnote 1.
In general, studies have found that for key components of the ecosystem, including invertebrates, fish, marine mammals and sea turtles, biological impacts vary from species to species and according to the proximity to the sound source arrays. Impacts are greatest within a few metres of the seismic source arrays.
Some marine mammals rely heavily on the use of underwater sounds to communicate and to echo-locate and emit and can sense different sound frequencies. There is evidence that these species hear and react to many man-made sounds including those associated with seismic surveys. The available data suggests that for a seismic sound to result in auditory impairment or other direct physical impacts for marine mammals, animals must be located within a short distance from the sound source. Most marine mammals, including most baleen whales, some odontocetes (toothed whales) and some pinnipeds (seals), generally avoid the immediate vicinity of active seismic vessels. However, some marine mammals, such as dolphins and porpoises, have been observed to swim near sources of seismic sound, with no apparent impacts.
The findings of the peer review process concluded that there was evidence that at certain received sound levels, behavioural changes can be manifested by some marine fish, marine mammals and sea turtles. If seismic surveys were to occur in areas and at times when a large enough aggregation of these marine organisms were engaged in critical biological functions the behavioural impacts might have important ecological and population-level impacts. For example the impact may be important if it results in the displacement of breeding, feeding or nursing marine mammals, dispersion of spawning aggregations of fish in their spawning areas and diversion of aggregations of marine mammals and fish from their migration routes.
While there has recently been an increased interest in sea turtles because of the endangered or threatened status of some species, relatively little is known about the sensitivity of these species to sound. Studies do indicate that sea turtles are able to detect sound frequencies similar to those generated during seismic surveys. As a measure of precaution, given the limited knowledge on the sensitivity of sea turtles to sound and given the endangered status of a number of sea turtles, it was concluded that sea turtles should have the benefit of the same mitigative measures as marine mammals.
Building on existing scientific information, the peer review process concluded that mitigation should be used where detrimental population-scale impacts were considered likely to occur, or where adverse impacts including death, harm or harassment of individual marine mammals or turtles listed as endangered or threatened on Schedule 1 of the Species at Risk Act were likely to occur.
The peer review process identified a number of recognized measures for mitigating the potential impacts of seismic sound, consistent with a precautionary approach. A federal-provincial regulatory policy review further identified the most effective measures which would be appropriate for use in Canadian marine waters. Federal and provincial governments have agreed to incorporate these measures into theStatement of Canadian Practice with respect to the Mitigation of Seismic Sound in the Marine Environment.
THE STATEMENT OF CANADIAN PRACTICE WITH RESPECT TO THE MITIGATION OF SEISMIC SOUND IN THE MARINE ENVIRONMENT specifies the mitigation requirements that must be met during the planning and conduct of marine seismic surveys, in order to minimize impacts on life in the oceans. These requirements are set out as minimum standards, which will apply in all non-ice covered marine waters in Canada. The Statement complements existing environmental assessment processes, including those set out in settled land claims. The current regulatory system will continue to address protection of the health and safety of offshore workers and ensure that seismic activities are respectful of interactions with other ocean users.
The Statement was developed by federal and provincial authorities responsible for the regulation and management of seismic surveys, including representatives from the provincial governments of Nova Scotia, Newfoundland and Labrador, British Columbia and Quebec. Federally, representation included Natural Resources Canada, Indian and Northern Affairs Canada, and Fisheries and Oceans Canada. TheStatement was developed following a peer review process involving scientific and technical experts, acousticians, and experts in the design and effectiveness of mitigative measures. Public policy experts as well as experts from the National Energy Board, the Canada-Nova Scotia and the Canada-Newfoundland and Labrador Offshore Petroleum Boards were also consulted. Public input on theStatement was received during a 60-day web-based public consultation, and targeted discussions were held with representatives from the fishing and oil and gas sectors, academics and other interested parties.
The Statement will apply to all seismic activities in the marine environment that use air source arrays; as such it will not apply to activities conducted in ice covered waters. For seismic surveys conducted for the purpose of oil and gas exploration, the Statement will be administered by the existing oil and gas regulatory bodies – the National Energy Board, the Canada-Nova Scotia Offshore Petroleum Board, and the Canada-Newfoundland and Labrador Offshore Petroleum Board. For seismic surveys conducted for any other purposes, the Statement will be administered by Fisheries and Oceans Canada.
The Statement was drafted using the best available scientific information, current international best management practices and internationally recognized techniques to mitigate the impacts of seismic sound in the marine environment. However, it is recognized that the body of scientific knowledge is continually expanding. As new scientific information and improved mitigation technologies and practices emerge, these will be considered for incorporation into the Statement. The Statement will be reviewed on an annual basis, and interested parties will be consulted on any potential amendments.
The Statement of Canadian Practice with respect to the Mitigation of Seismic Sound in the Marine Environment sets out mitigation requirements for:
- Planning of seismic surveys;
- Establishment and monitoring of a safety zone;
- Prescribed marine mammal observation and detection measures.
- Prescribed start-up; and
- Prescribed shut-down.
The following sections briefly describe each of these areas, and the requirements contained in theStatement:
Planning of seismic surveys
The Statement requires that operators plan and design seismic survey programs according to certain conditions. As a precautionary measure and to minimize the unnecessary introduction of sound into the marine environment, surveys are to be designed to use the minimum energy needed to obtain the information sought, to reduce or baffle the horizontal spread of sound and reduce the generation of unnecessary high frequency sounds.
In order to further reduce the potential impacts of a seismic survey, there is an additional requirement to design programs which avoid areas where it is known that there are aggregations of marine mammals and marine fish at critical times in their life cycle and during critical biological functions such as spawning, breeding, feeding, nursing and migration times.
Establishment and monitoring of a safety zone
Recognizing that sound is most intense closest to the air source and that the potential impacts of seismic are greatest within short distances, the Statement requires that a “safety zone" be established and monitored around seismic air source arrays. As noted above, the propagation of sound and of specific frequencies varies according to many factors, including ocean depths, temperatures and salinity. This poses a challenge in establishing precise distance at which specific sound levels can be expected. Similarly, marine species respond differently to various frequencies of sound, depending on their biological characteristics, life history and their respective hearing thresholds. The use and testing of sound propagation models combined with active science research programs are increasing our understanding of potential impacts and relationships between sound levels/distance and those impacts.
The Statement contains a basic requirement for a minimum 500m safety zone, established around the air source array(s). Existing scientific evidence and the application of a precautionary approach revealed that beyond a 500m safety zone, sound energy from seismic activity is unlikely to cause adverse impacts on marine mammals and sea turtles, under many circumstances. However, the Statementrecognizes that in other circumstances, environmental assessment processes may identify the need for a safety zone of greater than 500m.
As is discussed below, the Statement requires seismic vessels to use a qualified marine mammal observer to watch the safety zone. If a whale, dolphin, porpoise or sea turtle is seen by a marine mammal observer to be within the safety zone, the air source array must not be started up until the area is clear. Similarly if a marine mammal listed as endangered or threatened in Schedule 1 of the Species at Risk Act is in the area of the safety zone, no activity can begin.
Most marine species will likely avoid a seismic vessel while survey activities are underway. Seismic operators are required to take advantage of this behaviour by using a start up technique whereby activation of the air source arrays begins with a pulse from the lowest energy source on the array. The remainder of the sound sources on the array are gradually activated over a fixed period of time. This procedure provides the time and the incentive for marine mammals and fish to leave the immediate area.
In certain circumstances, such as well site surveys and vertical seismic profiling, only one energy source is used. In this circumstance, where technically feasible, the start-up procedure should consist of a gradual increase of the intensity of the sound until it reaches the required intensity.
Once seismic survey activity is ongoing, if a marine mammal or a turtle listed as endangered or threatened on Schedule 1 of the Species at Risk Act enters the safety zone the operator must shut down and wait for them to leave. The Statement also requires shut down of the array if other species of marine mammals or sea turtles enter the safety zone. These species could be those identified by an environmental review process as possibly experiencing significantly-adverse population-level impacts if exposed to seismic sound.
Prescribed procedures when active surveying ceases
As a precautionary measure and to reduce the amount of unnecessary sound released into the marine environment, when active surveying ceases, operators are required to either shut down the energy source completely or shut down all but one source. Continued release of sound from a single source would serve to deter whale, dolphin, porpoises or turtles from entering the safety zone.
Prescribed marine mammal observation and detection measures
Marine mammal observer: The Statement requires the stationing of a qualified marine mammal observer on board seismic vessels. The marine mammal observer is required to verify that the safety zone is clear for at least 30 minutes before the seismic air source array (s) can be activated. A marine mammal observer is required to maintain a regular watch during the entire duration of the time that the air source arrays are active and that the safety zone is visible.
Use of Cetacean detection technology: Reduced visibility and storm conditions may require the use of different mitigative measures, such as Passive Acoustic Monitoring, to detect and track the sounds made by vocalizing marine mammals prior to start-up. Passive Acoustic Monitoring uses “listening" technology to detect animals that are below the sea surface, while having no adverse environmental impacts of its own. Passive Acoustic Monitoring’s usefulness presently is limited to those species that are known to vocalize and to spend much time below the water surface (e.g., dolphins, sperm whales, northern bottlenose whales). Additional approaches to marine mammal detection (including radar, infrared detection and adaptation of fishing industry “fish finder" technologies) are currently in the research and planning stages, and will likely be available in upcoming years.
The Statement requires the use of cetacean detection technology under certain circumstances and conditions. If all of the following conditions exist, then PAM, or equivalent technology, must be used:
- the survey’s sound sources array has been shut down for more than 30 minutes;
- the full extent of the safety zone is not visible;
- the survey is in an area where vocalizing cetaceans such as dolphins, porpoises and whales listed as endangered or threatened in Schedule 1 of the Species at Risk Act are likely to be encountered, or if the survey is conducted in an area where species identified in an environmental assessment process as likely to be negatively impacted at a population level by seismic sound are likely to be found.
Under these conditions, if the presence of a vocalizing whale, porpoise or dolphin is detected and it cannot be identified, the operator must assume that it is a whale listed as endangered or threatened in Schedule 1 of the Species at Risk Act, or one identified by an environmental assessment process, and the operation must shut down and remain shut down until the operator is able to determine that the whale, dolphin or porpoise is outside the safety zone, or has not been heard for at least 30 minutes.
Additional or modified mitigative measures
In some cases, environmental assessment processes will point to regional specificities, including oceanographic, geomorphologic and biological characteristics, and regulatory reviews may require modified or additional mitigative measures to be applied. Also, variations to the mitigative measures set out in the Statement may be allowed if persons wishing to conduct seismic surveys provide an equivalent or greater level of environmental protection.
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