The design and construction contract was won by the Pipelines Division of J Murphy and Sons Limited.

The pipe

The choice of material from which the pipeline is constructed rested with Murphy, and they chose to utilise a steel pipe.

The pipe is 1200mm in diameter and its wall is 10mm thick.  The inside of the pipe is coated in a very thin epoxy resin to ensure water quality is maintained.  The exterior of the pipe features a three layer polythylene 'sandwich' which is a couple of millimetres thick and acts  to defend the steel pipe from damage.  Each section of pipe weighs between four and five tonnes, and measures approximately 13 metres in length meaning that we will need 4074 lengths of pipe to complete the pipeline.

Transporting the pipe

The steel core of the pipe is manufactured in Turkey and the Czech Republic before it's transported to Dunkerque in France to be coated and shipped to either Hull or Liverpool.  Four sections of pipe can be placed onto each lorry which then transports them either to the construction site or to one of four storage yards spread along the length of pipeline.

Installing the pipe

Murphy have already been out along the whole length to mark out the route of the pipeline; and in most places they have already stripped away the topsoil from the working area.  Because of the size of the pipe and the machinery needed to install it a working area with a width of 43 metres is needed where possible.  Once the working area has been fenced off a 2.5m wide trench is dug up to 3m deep.

The 13 metres long sections of pipe are delivered to the site and four are welded together so that they now measure 52 metres (4 x 13m = 52m).  Each of the 52 metre long lengths are then lowered by a line of cranes into the trench where they are welded onto the previous section.

At strategic points, sections of the completed pipeline will be pressure tested with water to ensure that the pipe has been correctly installed.  Pressure testing involves filling a section of the pipeline with water under pressure.  During testing the pressure in the pipeline will be raised to 1½ times the maximum operating pressure.  Testing the pipe as we progress along the route means that should we find any problems then only a small section will need to be replaced.  Once fully complete, the whole pipeline will again be pressure tested.

If we have been working in your area and are yet to put the land back as it was, don't worry.  We will not reinstate any land that we have been working in until the whole pipeline has been completed and pressure tested.  This prevents us having to reinstate land twice should there be a need for us to check the pipeline at any point.      

Constructing tunnels

The will be 21 tunnels along the route, these enable us to take the pipeline underneath busy motorways, roadways and rivers; as well as under protected woodland.

To construct a tunnel we must first construct two concrete lined shafts at either side of the obstacle we wish to cross.  One shaft is called the drive shaft and the other the reception shaft; these are typcially 6 metres in diametre and can be up to 25 metres deep.

A tunnelling machine which is a smaller version of the ones used on the Channel Tunnel is lowered by crane into the drive shaft.  The laser guided machine then begins to drill horizontally from the bottom of the shaft in the direction of the reception shaft.  Soil and debris is passed back into the shaft by a conveyor belt, from where it is lifted to the surface and disposed of.  As the machine progresses 1.8 metre concrete rings are put in place behind it, so that by the time it reaches the reception shaft the whole length of the tunnel has a reinforced concrete wall. 

When the pipeline approaches a tunnel site the pipe is fed vertically down the drive shaft and fed through the tunnel.  When this is complete, the space between the pipe wall and the tunnel wall is grouted with cement to form a protective layer.

The two shafts will be filled with a material similar to sand that would enable us to gain access to the pipe in the future if needed, and all that will be seen from the surface will be a manhole cover above both shafts.