«GUIDELINES FOR MINIMISING ACOUSTIC DISTURBANCE TO MARINE MAMMALS FROM SEISMIC SURVEYS April 2004 These guidelines are aimed at minimising the risk of ...»
JOINT NATURE CONSERVATION COMMITTEE
7 Thistle Place
Tel: 01224 655716
GUIDELINES FOR MINIMISING ACOUSTIC DISTURBANCE TO MARINE MAMMALS FROM
These guidelines are aimed at minimising the risk of acoustic disturbance to marine mammals including seals, whales, dolphins and porpoises from seismic surveys. In addition to keeping noise levels at lowest practicable levels the recommendations contained in the guidelines should assist in ensuring that marine mammals in areas of proposed airgun activity are protected against possible injury. These guidelines reflect a precautionary approach that should be used by anyone planning marine operations that could cause acoustic or physical disturbance to marine mammals.
The guidelines have been written for use in the United Kingdom Continental Shelf (UKCS).
Whilst we do not object to these guidelines being used elsewhere we would encourage all operators to determine if any special or local circumstances pertain as we would not wish these guidelines to be used where a local management tool has already been adopted (for instance in the Gulf of Mexico OCS Region). We also note that other fauna, for example turtles, occur in waters where these guidelines may be used. We suggest that, whilst the appropriate mitigation may require further investigation, the soft start procedures similar to those followed for marine mammals should also be employed for other fauna.
In relation to oil and gas seismic surveys on the UKCS, it is a legal binding condition of the consent issued for seismic surveys under regulation 4 of the Petroleum Activities (Conservation of Habitats) Regulations 2001 by the Department of Trade and Industry (DTI) that the JNCC Guidelines must be followed at all times for all seismic surveys. It should be noted that it is the responsibility of the company issued consent by the DTI, referred to as ‘applicant’, to ensure that these guidelines are followed and the relevant marine mammal observer reports submitted to the JNCC. We recommend that a copy of the JNCC guidelines are available onboard all vessels undertaking seismic surveys on UKCS.
The guidelines are broken down in the following sections:
Section 1 - Precautions to reduce the disturbance caused by seismic surveys
1.1 The Planning Stage
1.2 During the Seismic Survey
1.3 Report after the survey Section 2 - Guidance when carrying out the soft start
2.1 Look and Listen
2.3 The Soft Start
2.4 Site survey/Vertical Seismic Profiling and soft starts
2.5 Line Changes
2.6 Undershoot Operations Section 3 - Marine Mammal Observers (MMOs)
3.1 Likely Requirements for MMOs Section 4 - Acoustic Monitoring
4.1 Use of PAM as a mitigation measure Section 5 - Background Information
5.1 Existing legislation Section 6 - Further information, comments on these guidelines and contacts Terminology High Resolution Seismic Site Survey is defined as those using an airgun array of 180 cubic inches or less.
Seismic Survey includes 2D/3D/4D and OBC (Ocean Bottom Cabling) surveys and any similar techniques Vertical Seismic Profiling or Borehole Seismic is defined as seismic used in connection with well operations typically with a source size of 500 cubic inches.
Consent is the consent issued by the DTI under regulation 4 of the Offshore Petroleum (Conservation of Habitats) Regulation 2001.
Applicant is defined as the company who has applied to the DTI for PON 14A consent. This could either be an oil and gas operator or a seismic survey company.
Section 1 – General precautions to reduce the disturbance caused by seismic surveys
1.1 The Planning Stage - When a seismic survey is being planned, operators should:
• Consult relevant literature and if necessary, contact the Joint Nature Conservation Committee (JNCC) to determine the likelihood that marine mammals will be
encountered. For instance:
• Plan surveys so that their timing will reduce the likelihood of encounters with marine mammals especially during the breeding and calving seasons. If an area is particularly sensitive due to the species present an assessment of this should be included within the PON 14 application
• Seek to provide the most appropriately qualified and experienced personnel to act as marine mammal observers (MMOs) on board the seismic survey vessel (see Section 4 for further information on MMOs).
• Plan to use the lowest practicable power levels throughout the survey.
• Seek methods to reduce and/or baffle unnecessary high frequency noise produced by airguns or other acoustic energy sources.
1.2 During the Seismic Survey - When conducting a seismic survey, operators should:
• Ensure that the correct ‘soft start’ procedure is followed. Soft starts are intended as a time period to allow marine mammals to move away from an area should they wish to do so. (See Section 2)
• There should be no shooting apart from that necessary for the normal operations of a seismic survey or for a ‘soft start’. Protracted shooting which is not part of a survey line is discouraged.
1.3 Report after the survey
A report detailing marine mammals sighted (standard forms are available from JNCC), the methods used to detect them, problems encountered, and any other comments helps to increase our knowledge and allow us to improve these guidelines. Reports should be sent to the JNCC ideally by e-mail to email@example.com or faxed/posted to the address at the face of these guidelines. Reports should include the following
• The Seismic Survey reference number provided to operators by the DTI
• Date and location of survey
• Number and volume of each airguns used also calculated as total volume.
• Nature of airgun array discharge frequency (in Hz), intensity (in dB re. 1µPa or bar metres) and firing interval (seconds), or details of other acoustic energy used
• Number and types of vessels involved in the survey
• A record of all occasions when the airguns were used, including the watch beforehand and the duration of the soft-start (using standard forms)
• Details of any problems encountered during marine mammal detection procedures, or during the survey
• Marine mammal sightings (using standard forms)
• Details of watches made for marine mammals and the seismic activity during watches (using standard forms)
• Reports from any observers on board
Section 2 – Guidance when carrying out a soft start
If dedicated MMOs are requested to be on board a seismic vessel they should make certain that their efforts are concentrated on keeping a watch prior to the soft start. At no time are these guidelines meant to imply that MMOs should keep a watch during all daylight hours. JNCC strongly encourage all MMOs to manage their time to ensure that they are available and at the best of their ability when carrying out a watch during the crucial time – the 30 minutes before commencement of the use of a seismic source.
However, JNCC does appreciate the efforts of MMOs to collect data at other times than prior to the soft start but this should be managed to ensure these observations are not detrimental to the ability of the MMO to watch prior to a soft start. The JNCC will request that two marine mammal observers be used when daylight hours exceed approximately 12 hours per day. Where two MMO’s are onboard a seismic vessel we would encourage them to collaborate to ensure cetacean monitoring is undertaken during all daylight hours and to ensure that an observer is always available to undertake a pre-start up search for the required 30 minute.
2.1 Look and Listen
Beginning at least 30 minutes before commencement of any use of the seismic sources, the dedicated MMO or if a dedicated MMO has not been requested by the DTI, a nominated member of the ships company should carefully make a visual check from a suitable high observation platform to see if there are any marine mammals within 500 metres (measured from the centre of the array).
If marine mammals are seen within 500 metres of the centre of the array the start of the seismic sources should be delayed until they have moved away, allowing adequate time after the last sighting for the animals to move away (at least 20 minutes). In situations where seal(s) are congregating immediately around a drilling or production platform, it is recommended that commencement of the seismic sources begin at least 500 m from the platform.
2.3 The Soft Start
Power should be built up slowly from a low energy start-up (e.g. starting with the smallest airgun in the array and gradually adding in others) over at least 20 minutes to give adequate time for marine mammals to leave the vicinity. This build up of power should occur in uniform stages to provide a constant increase in output. There should be a ‘soft start’ every time the airguns are used, even if no marine mammals have been seen.
• We encourage all seismic survey operators to ensure that, as far as possible, soft starts occur during daylight hours when MMO’s or the nominated crew member can carry out the required 30 minute watch. If visual observations can not be made we continue to encourage the use of PAM for acoustic monitoring during this time.
• To minimise additional noise in the marine environment, a ‘soft start’ (from commencement of soft start to commencement of the line) should take no longer than 40 minutes.
• The ‘soft start’ procedure should be followed at all times including before test firing of the airguns.
• If, for any reason, firing of the airguns has stopped and not restarted for at least 5 minutes a full 20 minute ‘soft start’ should be carried out. After any break in firing of any duration a visual check should be made for marine mammals within 500 metres of the centre of the array. If a marine mammal is present then recommencement of shooting should be delayed as per the Look & Listen, Delay and Soft Start instructions above.
• When time-sharing, where two or more vessels operate in adjacent areas and take turns to shoot to avoid causing seismic interference to each other, all vessels shooting should follow the full ‘soft start’ procedure for each line start.
2.4 Site Survey / Vertical Seismic Profiling (VSP) and Soft Starts
Whilst we appreciate that high resolution site surveys / VSP operation may produce lower acoustic output than 2D or 3D surveys and that firing of individual airguns may not be possible for technical reasons, we believe it is still necessary to undertake some form of a soft start to allow time for marine mammals to move away from an airgun.
We understand there are a number of options as to how a soft start may be undertaken.
For reasons of flexibility we are content for high resolution seismic site surveys and VSP
operations to use any of the methods below for a soft start:
A. The standard method, where power is built up slowly from a low energy start-up (e.g. starting with the smallest airgun in the array and gradually adding in others) over at least 20 minutes to give adequate time for marine mammals to leave the vicinity.
B. As the relationship between acoustic output and pressure of the air contained in the airgun is close to linear and most site surveys / VSP operations use only a small number of airguns a soft start can be achieved by slowly increasing the air pressure in 500 psi steps. From our understanding the minimum air pressure which the airgun array can be set to will vary, as this is dependent on the make and model of the airgun being used. The time from initial airgun start up to full power should be at least 20 minutes.
C. If neither of the above techniques (A or B) can be used, over a minimum time period of 20 minutes the airguns should be fired with an increasing frequency until the desired firing frequency is reached.
If an operator of an airgun array is unable to undertake a soft start using the methods above a waiver must be granted in the DTI consent. This must be applied for with the JNCC prior to the actual operation occurring ideally as part of the PON 14A submission or for VSP the PON14A or PON15B. If a waiver has not been agreed by the JNCC, and consented to by the DTI and a soft start is not implemented applicants will be in breach of their consent.
When submitting the MMO report to the JNCC for high resolution seismic site surveys operators should indicated which of the above methods was used to achieve the soft start.
2.5 Line Change
Seismic data is usually collected in lines. Line change is the term used to describe the time it takes for a vessel to turn from the end of one line to the start of the next.
Depending upon the type of seismic survey being undertaken, the time for a line change can vary between five and ten minutes for site surveys to two to three hours for 3D exploration surveys. In the past this has caused some confusion as to when a soft start
will be required. In order to standardise approaches the following guidance is provided:
A. For line change times greater than the time required to undertake a soft start, airguns should cease firing at the end of each line and commence a full soft start at the appropriate time before commencing the next line (i.e. a soft start of at least 20 minutes prior to commencement of the next line).
B. For line change which take less time than that required to undertake a soft start, airguns should continue firing the full array during the line turn (i.e. for a site survey line turn of 5 minutes continue firing at full power).