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One of the main concerns in the piling industry has become environmental conservation and reducing the environmental footprint of a project as much as possible, whether that be the reduction of noise pollution, carbon dioxide emissions or wildlife habitat destruction.
Thankfully, there’s a way to prevent all that, especially if piling relatively close to a potential wildlife habitat, such as within a body of water, with a technology known as bubble curtains.
For those who thought bubble curtains were that mixture of suds and water seen streaming down the window during an automated car wash, get ready to have your mind blown.
Bubble curtains are made from a linear pipe laid at the bottom of a body of water that emits air bubbles through special punctures in the pipe at adjustable sizes and speeds to create a literal “bubble curtain” as the bubbles float to the surface.
Bubble curtains can be used for a variety of applications, including aerating canals, de-icing docks or ferry terminals, to deter wildlife from swimming into water intakes and near construction sites. The technology can also be used for sound attenuation, such as reducing the intensity of the noise generated while drilling or driving piles, which also protects the nearby marine life by ensuring they are undisturbed by the underwater construction.
“Air bubbles are little empty spaces, so when a sound wave arrives, this sound wave will be broken by the fact that it’s going through the equivalent of a cloud,” said Mario Paris, CEO of CanadianPond, inventors of a flexible tubing that’s perfect for delivering the necessary air to create the bubbles in any bubble curtain apparatus.
Prior to CanadianPond’s invention of what’s called Bubble Tubing® in 2005, there were only two pipe options for bubble curtains. These were either held at the seabed with lead, which is toxic, or weren’t very supple and instead were very harsh and stiff to work with.
Originally, CanadianPond invented Bubble Tubing® to aerate a canal, but quickly discovered many other applications for the invention. In one case, CanadianPond was approached by a scientist working on his engineering thesis in France as he wanted to evaluate the capacity for sound attenuation in marine environments.
“The sound reduction can be measured before and after the bubble curtain is run and depending on the size of the bubbles, the thickness that you’re putting into your bubble curtain, you will be able to reduce the sound and reduce its frequency,” said Paris.
The more layers of bubble curtain sound must travel through, the fainter the sound becomes. During tests of the effectiveness of their bubble curtain system, CanadianPond compared a single and a dual bubble curtain. They found that a single bubble curtain is most effective at reducing low frequency sounds, while higher frequency sounds need to pass through a double layer of bubble curtain to be sufficiently dulled.
“These discoveries lead into product development and further [research and development], so we can pinpoint or develop products that are targeting certain types of protection. For example, if you’re trying to protect whales, as opposed to fish, you may be better served with a certain size bubble or a certain combination of bubble curtains,” said Paris.
“Sound is becoming a new frontier that’s being looked at as something that needs to be reduced to protect marine mammals.”
– Mario Paris, CanadianPond
All of this highlights the fact that this is still a new field. Although bubble curtains are becoming required in more locations as environmental protection rules are enacted that call for the reduction of noise pollution on jobsites as a means of protecting surrounding wildlife, bubble curtains have not been fully adopted around the world for their sound dispersal capabilities.
“Sound is becoming a new frontier that’s being looked at as something that needs to be reduced to protect marine mammals,” said Paris.
So, how is a bubble curtain created and how far from the jobsite can it be placed to be effective at maintaining silence for the surrounding wildlife?
If a piling installation is in an area of approximately 300 metres by 600 metres with multiple piles being driven, the bubble curtain could be in a fixed location, 50 metres to 200 metres away from the source of the pile driving, for the duration of the project.
If only one pile is being driven, there’s no need to be very far from the pile, but Paris says to try not to be any closer than five metres from the pile.
Bubble curtains use onshore air compressors to feed an air diffuser, which pushes the bubbles through the specifically punctured tubing to the surface of the water.
“The further you go from the pile, the more curtain (and therefore, air flow) you will need because the bubble curtain will be longer. But the further you are from the pile, the more the sound will already be lessened a bit. If you are very close, you will need a very dense bubble curtain to be able to attenuate the sound,” said Paris.
Bubble curtains use onshore air compressors to feed an air diffuser, which pushes the bubbles through the specifically punctured tubing to the surface of the water. Some are permanent installations, but in the case of sound attenuation, they are always temporary as sounds must only be reduced if sound is being emitted. A good bubble curtain effectively puts earmuffs on a construction project, but it’s not the only protection for marine life in the area.
“The typical marine installation doesn’t do pile driving at night and they have whale spotters if there have been whales in the area. They are onsite and will halt a job for as long as it takes a whale to swim away if they are within one kilometre of the jobsite,” said Paris.
The one caveat to all this is that employing bubble curtains for sound attenuation on a jobsite is completely voluntary in North America, even though the need for a bubble curtain is starting to be regulated in Europe.
“We’ve had conversations with Fisheries and Oceans, as well as Environment Canada, and what they do right now is ask bidders on a construction project to reduce the noise level by 10 decibels. Since this is such a new field, they’re trying to give a reasonable target of a certain quantity of decibels, which is usually fairly easy to achieve if you use a bubble curtain,” said Paris.
“This is a growing field and we’re in a good position as a Canadian company to supply this market because we saw it coming from the start, we’ve done some third-party studies measuring effectiveness, and we have a very flexible, easy-to-use Canadian-made product.” 