Supply, installation and extraction of an eight sided cofferdam consisting of:-

• 113 SX18 steel sheet piles at 8m in length.
• 6 W90 wall profile corner clutches.

Steel Pile Installations were employed in August 2008 by SP Fields to design, install and extract a 'T' shaped cofferdam, along with associated welded steel framing, to allow excavation, up to 9.5 metres deep below the existing floor level within Sheffield Forgemasters to accommodate a new 'Press Base' within the existing foundry in Brightside, Sheffield.

Due to the limited headroom within the existing building, our Movax SP75 side grip vibratory hammer (handled by our 38 tonne tracked excavator) was utilised to initially pitch and drive the sheet piles within the 12 metres of headroom above the working area. The piles were installed to form the perimeter of the cofferdam for a main excavation of 15.0 x 15.0 metres with a further 6.0 x 6.0 metres base "tagged-on" to the side of the main  foundation.

Further driving through the thin coal seam and into the underlying  mudstone was carried out using our SL20 1.5 tonne hydraulic impact hammer to achieve the required pile toe levels. Due to the obvious restrictions on working room within the existing factory it was not possible to use a mobile crane to handle this equipment hence the impact hammer was successfully used in conjunction with the 75 tonne overhead crane already in use within the existing building.

Welded steel framing was then installed by welders as the upper level of support to the excavation. A further lower proprietary hydraulic frame (provided by Groundforce) was installed by the main contractor to allow full depth excavation. The lower hydraulic frame will be removed once a 500mm blinding strut has been cast. The rest of the base will then be poured and the upper framing removed.

Due to the ground conditions encountered during driving of the piles and difficult access conditions, it is intended that the sheet piles will be extracted using our Tosa WP150 "Still Worker", used in conjunction with the existing overhead crane. Extraction of the piles is currently scheduled from mid-November 2008.