Gated silt curtain for Sunderland River Wear crossing…
On holiday in Antigua in 2014 I was privileged to rescue about 30 newly hatched turtles from marauding frigate birds. The turtles had hatched on the beach the night before but had been swept back inshore due to unseasonal strong winds and rough seas. The following morning calm had returned and I was able to carefully return them to the water. As they swam away my email bleeped. I really should know better by now than to keep my phone with me on holiday, but I guess that is the reality of running a small emergency response company!
The enquiry wasn’t an emergency but it wasn’t going to be a straight forward job and actually, sitting on the beach, feeling that all was well with the world, I found that I was in exactly the right frame of mind for designing a silt curtain installation to cope with the tidal and shipping demands of the River Wear!
There has been talk about a new River Wear crossing in Sunderland for over ten years, with various projects falling by the wayside due to funding crises and contractor withdrawals. Finally in 2014 the project was resurrected with a cable design bridge. During the autumn of 2014 we worked with both Dragados and FCC Citizen Services on design concepts for the silt curtain that would protect water quality in the river during the construction works. The challenge for the design would be the monumental pressures that would be exerted on the silt curtain by the four daily North Sea tide changes. In January 2015, having put in many hours on the project in conjunction with Dragados we were told that they had been unsuccessful with the bid!
It was then officially reported and confirmed in May 2015 that the £117.6m project was to go ahead through a Farrans/Victor Buyck joint venture. Twice the height of Nelson’s Column, and bigger than Big Ben, Sunderland’s new bridge will be hard to miss. It was therefore with some professional pride that we were asked to further assist with this prestigious project by the Farrans/Victor Buyck JV.
I always like to visit site prior to any official contract, to see if the silt curtain solutions I have proposed on paper can be implemented on the ground. We don’t charge for this service as both site scoping, and the forging of a positive working relationship with the project management team, can be the make or break of a successful outcome for the silt curtain.
Once on site however we found we needed to revisit the design and make significant changes. There is no such thing as a straightforward silt curtain installation! Not only did we need to minimize mobilized silt in the water column, but the curtain required a 20m gate in the main channel for barges to gain access to the site! This would mean that the new design would require considerably more anchorage, and the curtain would need to be extra tough in its construction. Through discussion with the engineers we arrived at a mutually acceptable solution and fabrication and installation could begin.
Perseverance and adaptability won the day. The curtain was installed and is performing well with the bridge due to open in 2018. This photo, showing calm waters and a barge making its’ way through the curtain, belies both the strong tidal force beneath the water and the protracted design process! What I particularly like about this project though is that every time I have contact with it, it reminds me of the turtle hatchlings. Worlds apart but inextricably linked!
Glyn Onione – Senior Technical Consultant at Aquatic Engineering
Have a question about silt curtains? Aquatic Engineering have the answers. Email firstname.lastname@example.org or phone us on 01983 616668