The £20-million ($24,088,000) remediation, marine and civil project for South Tyneside Council at East Holborn—at the mouth of the River Tyne in northeast England, UK—needed a radical solution to protect migrating Atlantic salmon from acoustic trauma and possible death on their journey through the River Tyne.
John F Hunt was appointed as principal contractor in December 2021 for site preparation, remediation, marine and civil works to the 22-acre former dockland which included four dry docks, pumping chambers and dilapidated dock gates.
Subject to stringent local planning and marine licensing conditions, work on this high-profile development includes demolition, earthworks, ground remediation, land drainage, and the creation of five new river walls and dock closure structures. However, the Marine Management Organisation (MMO) limits operations generating intrusive noise—at levels capable of harming marine life— to within three hours of low tide from March to September and four hours after high tide in May.
The Tyne has become a principal salmon river in the UK over the years, and the MMO was concerned about the impact that underwater transmission of noise generated by the work could have on the fish. John F Hunt, therefore, needed to restrict any work that could transmit noise through the water, but even with careful planning, this meant massive downtime, resulting in major additional costs and delays to the programme.
Safeguarding the Atlantic salmon on their passage through the Tyne during their breeding season and the subsequent return of their young to the sea required an effective and innovative sound protection measure.
David McLaren, site manager at John F Hunt Regeneration said, “In conjunction with Frog Environmental, Canadian Pond, Rocksalt and Subacoustech, we embarked upon an extensive design review. The research, using verifiable data from the river including flow rates and background acoustic measurements, was rigorously tested and resulted in the installation of a simple but effective wall of bubbles.”
(Air bubble curtains are also referred to as air barriers, air curtains, bubble barrier, bubble curtain, pneumatic barrier, pneumatic boom and bubble wall. They are wide use to protect marine mammals during the construction of offshore wind turbine farms.)
A 90-meter-long vertical curtain of bubbles was created from a perforated, weighted tube laying on the riverbed, through which compressed air was forced,” McLaren continued. “The uniform wall of bubbles reduced our sound impact in the river by an amazing 20db, to an MM-approved level, effectively satisfying the Marine license condition to allow us unrestricted, continuous working. This was the first time this had ever been granted in the UK. It is also the first time the Bubble Curtain system, which originated in Canada, has been tested as an acoustic barrier in Europe, although it has been used in several other countries around the world.”
Regardless of the design, procurement and deployment costs, John F Hunt still expects to see the Bubble Curtain system provide them with significant contract savings. The most important outcome, however, is that of program certainty and the safe passage of Atlantic salmon through the River Tyne.
More information on John F Hunt Regeneration can be found www.johnfhuntregeneration.co.uk/.
Reprinted from Marine Construction Magazine Issue I, 2023
