On completion of fabrication there was a requirement to store the STL sections above ground. This presented a problem with the limited space available and a system was developed to allow the sections to be lifted and rotated into the vertical. The sections were then positioned on "roller skates" and hauled into the storage area on steel footplates.

In addition to the Portal Crane, operating from the workshop to the Surge Shaft, a system of material handling temporary works and a 35te capacity main winch using a two fall rope configuration were set up to facilitate the installation of the 40 - 50te STL sections.

Each sections was lowered 120m down the Surge Shaft, rotated through 90 degree, attached to heavy duty bogies and lowered 450m down the inclined shaft, and for the first few sections, also lowered around the bottom bend and along the horizontal High Pressure headrace Tunnel.

Access to the workface was via a twin rope manriding winch and cage down the Surge Shaft and a similary configured manriding winch and car down the inclined shaft.

A multi level welding platform with independent winching capability was installed for use in the inclined shaft.

Intensive safety procedures were adhered to at every stage of the works to ensure safe working, as well as achieving an efficient productivity level.



In order to accommodate a change in geometry in the high pressure headrace tunnel a rail turnable was introduced to enable the sections to be moved into position.

At handover it was also indentified that the inclined shaft geometry deviated from the planned configuration which presented addtional problems with the installation of the STL sections and the winch rope management.

Mitres were incorporated at several in-situ weld seams to adjust the line of the STL in the relation to the shaft geometry and lobsterback bend at the bottom of the inclined shaft was rotated in-situ with the aid of hydraulic jacks.


After each section had been lowered into position the associated temporary works needed to be retrieved ready for use on the next section. The heavy load installation/ light load retrieval problem was solved by ballasting and moving the load points during retrieval and a simplified system of dismantling and re-building the temporary works was developed.

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