FP McCann’s back-bolted smoothbore shaft segments have been used to form a new pumping house at Claverdon sewage treatment works in Warwickshire. The upgrading of the treatment plant will facilitate the construction of a major development proposed for the area.

The shaft was constructed using the wet caisson method with FP McCann’s 6m ID back bolted precast concrete rings forming the shaft wall. The shaft was sunk to a depth of 8m a jacking system which guarantees a vertical structure upon completion.

The design of the structure included the use of a panelled choker ring, manufactured by FP McCann, which sat on top of a FP McCann concrete cutting edge, a combined choker/cutter incorporating recesses cast into the intrados, in order to provide shear interaction with the in-situ concrete base and to resist floatation.

FP McCann’s smoothbore shaft segments are all factory fitted with EPDM rubber gaskets which provide an immediate water-tight seal upon construction. Cross segment connections are made by passing a spear bolt through a pocket in one segment and screwing it into a threaded plastic socket in the adjacent segment. Circle joint connections are made using a ‘T’ bolt passing through a hole in one segment into a ‘T’ box in the adjacent segment. Bolts are designed to fully compress the gasket.