An assessment was conducted on behalf of the main contractor by Sika Engineers, a specialist in sealing and reinforcing, which determined that "there were no issues regarding the stability of the cofferdam
On October 17, Remotely Operated Vehicle (ROV) video inspection observed small, intermittent drops of oil coming from an opening at the top and another on one side of the cofferdam
. Samples of the droplets have been collected from the opening at the top, known as the stovepipe, and will be analyzed to confirm a match with the sheen.
A fish biologist with CH2M Hill will be on the site while work is done within the river, and during drawdown of the water within the cofferdam
to salvage any fish that become trapped.
A pipelay barge, operated by Petroleum Marine Services was anchored about a half mile offshore and a steel cable was passed along the axis of the cofferdam
to the winch.
Temporary watertight structures called cofferdams
are being built to allow foundations to be laid for the three pylons that will support the main bridge.
The firm has already taken delivery of steel piles to be used to build a cofferdam
at its Graythorp site, near Hartlepool.
He covers groundwater control, side slopes and soil retention in open excavation, vertical soil support, cofferdam
construction, basement construction and design, cut-and-cover construction, shafts and caissons, and soil movement due to deep excavations.
Special attention was given to the area where the third cofferdam
crossed the pipelines in order to protect the lines as well as maintain a seal against a 10-foot head pressure along the lines.
Main features: supply and implementation of a cofferdam
storage bridge, supply and implementation of a bracket and its rudder.
The north and south pylon foundations were completed in early August 2015 and the concrete pour for the central cofferdam
foundations will take place in autumn 2015.
The two other applications - relating to other options for the installation of a cofferdam
- were also rejected.
Rather than utilize an expensive cofferdam
system, Whitaker used a much more cost-effective system to dam the river--trench boxes manufactured by Efficiency Production Inc.