Laing O’Rourke

Project Overview

To enable construction of an Attenuation Tank and Pumping Station within a 33m x 5m trench support system excavation, with the deepest excavation at 5.5m BEGL and rest groundwater level ~2.0m. A perimeter vacuum wellpoint system was installed.

Project Detail

• Made Ground: 0.0m to 0.7m BGL.
• Terrace Gravels: Medium Dense, very gravelly, fine to coarse SAND. Gravel subangular is to subrounded, fine to coarse: 0.7m to upto 5.2m BGL.
• London Clay: 5.2m BGL onwards
• Groundwater Level: 2.0m BGL.

Scope of Works

Vacuum wellpoint system installed at nominal 1.5m centres Around the perimeter of the works to top of Clay using conventional water jetting installation method. Provision of gap to allow access into one end.

System divided into two parts each pumped By a silenced diesel piston pump (49 dB at 7m) with fuel usage of 1.1 lts/hour. Discharge via v- notch settlement tank with calibrated flowmeter into Thames Water MH.