Seals to be repelled from gas pipeline’s route before mine clearance

Ultrasound is used as deterrent for marine mammals

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The mine clearance operation on the planned route of the Nord Stream gas pipeline from Russia to Germany will commence today, Tuesday, outside of Helsinki, weather permitting.
      The destruction of the unexploded wartime ordnance lying at the bottom of the sea will start with an effort to drive away any possible seals and shoals of fish from the vicinity of the blast site. Seals will be chased away with underwater warning sounds that repel marine mammals.
      “There is an observer onboard, whose task is to ensure that there will be no seals in the area”, says Sebastian Sass, head of Nord Stream's EU representation. “Therefore, to ensure that the seals can be seen, work is carried out during the daytime and only in good weather.”
      “Before the blastings, ultrasound is used to repel seals from the area. The advantage of ultrasound as a dispersal is that it is not audible to humans”, Sass says. Seals flee the sound and stay clear of the blast zone.
     
Sonar, in turn, is used to detect the presence of possible shoals of fish.
      If fish shoals are not detected, before the actual mine clearance a small explosive charge is still detonated as a deterrent.
      The destruction of the mine will be delayed, if mammals, shoals of fish, or migrating birds are observed in the area.
     
The total number of mines to be blasted in the Finnish economic zone from the route of the planned gas pipeline is 36.
      The mines will be detonated in a normal mine clearing fashion at the bottom of the sea where they lie. A remote-controlled robot examines the bottom, sets the detonation charges, and verifies after the blasting that the mine has been destroyed. The Finnish Defence Forces conduct similar clearing work frequently.
      There is no shortage of sunken wartime ordnance at the bottom of the Baltic Sea. During the First and Second World Wars up to a hundred thousand sea mines were dropped into the sea.
      After the war, a large portion of the ordnance was sunk at the bottom, and chemical and conventional munitions were dumped into the Baltic Sea up until the 1960s.
      In the entire Baltic Sea area, apparently more than a thousand sea mines have been destroyed by detonation since 1996.
     
The British battle area clearance company BACTEC’s vessel John Lethbridge arrived in the Gulf of Finland last week.
      High winds and poor visibility, however, prevented the start of the clearance operation over the weekend, and on Monday the vessel moored at Helsinki’s Jätkänsaari.
      Before any detonation an exclusion area with a radius of two kilometres will be set up around the location of the blasting. The ships operating in the area will be warned four hours in advance.
     
In the first instance the mine clearing vessel will operate just south of Helsinki. After that it will move to a position south of Hanko.
      Next spring the mine clearing crew will operate in the middle of a busy shipping lane south of Porkkala.
      In the Russian waters the devices on the route of the pipeline will be detonated by the Russian Navy.
      The start of the construction of the undersea pipeline itself is scheduled for next summer.


Previously in HS International Edition:
  Nord Stream mine clearance operation delayed in Gulf of Finland (20.11.2009)
  Mine clearance vessel arrives in Gulf of Finland (19.11.2009)

Links:
  BACTEC

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