Men at work on Saltash Site

Riverview Pumping Station, Saltash


Client: Saxton Drilling Ltd
Main Contractor: Alfred McAlpine Ltd
Engineer: Hyder

Temporary Works Retention and Permanent Works Anti-Flotation Designs

AGE carried out the design of the temporary works for a new stormwater storage tank built adjacent an existing pumping station. The new works were nominally 31 m x 9 m in plan and, due to the sloping ground level, called for excavation depths of around 8.5 m and 6.5 m. Ground conditions consisted mainly of made ground overlying slate bedrock. AGE suggested and provided a solution using 10 to 12 metre deep 152 x 152 UC king posts installed at between 0.8 and 1.2 metre centres, propped internally at two levels to suit both basement and floor slab construction.

In addition AGE designed permanent works rock anchors, installed vertically through the floor of the tank, to provide restraint to uplift flotation forces. Twenty seven such anchors were required, each with a design working load of 284kN. The anchors comprised a single 26.5mm diameter Dywidag double corrosion protected monobar anchor, and were some 12 metres in overall length, with a 4 metre fixed anchor length. The fixed anchor lengths were located within moderately weak to moderately strong slate bedrock. The anchors were installed through 200mm diameter ducts cast into the base slab of the tank, and were post-tensioned into pockets within the slab.

Overall view of Saltash site