As you may know, modern port infrastructure is of the most dynamic markets in which we operate. Benefitting from our in-house engineering office, we carry many different projects, mostly on a design & build basis, in several parts of the world, from coastal marine works, to breakwaters, jetties, quay walls, to marinas, water intakes, and shore protection activities.
Amongst the numerous mitigation measures that we consider fro reducing underwater noise and protect marine life when we are performing construction activities in water environment, is the known “bubble curtain” that you can see on this picture.
How it works
A bubble curtain is a marine engineering technique that uses a curtain of bubbles created by compressed air to reduce underwater propagation of noise and vibrations. Imagine blowing bubbles through a straw into a glass of water. Now, picture thousands of tiny bubbles rising from the seabed until the surface, forming a wall or curtain, creating a barrier of air in the water.
What it’s used for
Bubble curtains are used in various circumstances, mainly to protect marine life from the negative effects of underwater noise or vibration pollution caused by activities, such as:
- Underwater construction: When building bridges, ports, or jetties, the noise from machinery can harm aquatic animals like fish, dolphins, and whales.
- Dredging operations: Dredging involves removing sediment from the seabed, which can be noisy and disruptive to underwater ecosystems.
- Pile driving: Installing large structures like bridge or jetty foundations can produce loud noise that disturbs marine life.
Benefits
Bubble curtains offer several benefits to marine life:
- Noise reduction: By creating a barrier of bubbles, they absorb and scatter sound waves, reducing the impact of loud noises on marine animals. For example, during pile driving, without a bubble curtain, the noise from hammering piles into the seabed can strongly disturb and sometimes be harmful to fish and marine mammals. The recommendations are to maximize the noise reduction at a frequency of 400 Hz (the most sensitive for low frequency marine mammals). With a bubble curtain, the noise is significantly reduced. A noise reduction of 20 dB can be expected at 400 Hz.
- Protection of fish eggs: In some cases, bubble curtains can protect fish eggs by preventing them from being carried away by strong underwater currents created by construction activities.
- Preservation of natural habitats: By minimizing noise disruption, bubble curtains help protect sensitive underwater environments and ecosystems, including coral reefs and seagrass beds.
- Compliance with regulations: Many countries have regulations in place that require the use of bubble curtains to minimize the impact of underwater noise on marine life. Using bubble curtains helps us comply with these environmental regulations.
In essence, bubble curtains act like a noise-cancelling shield for marine life, allowing them to go about their business without being disturbed by the often-loud activities taking place in their underwater homes.
At BESIX, we’ve been using this technique for decades. Most recently we have applied or will apply it in Denmark (Crown Princess Mary bridge in Roskilde), in Poland (Vistula Spit), Ras Laffan (Qatar), Tanga jetty (Tanzania), Kitimat marine terminal (Canada), etc.
