Westminster School, London

gj-westminster-school-001Ground suffers from poor drainage

This private school in the heart of London has a single sports ground surrounded by residential dwellings.  With no drainage outfall the ground suffers from water logging as there is scarcely a fall of 1:100 in one direction being level in the other.

In a soil study it was found that the sandy loam topsoil in the playing area lay above filled material of brick and concrete fragments.

In assessing the potential for drainage to lower layers soakage tests were undertaken at eight borehole sites and found to be satisfactory.

In order to distribute the surface water evenly over the site it was envisaged that if a network of boreholes were drilled in a 20m grid over the entire plateau, a lattice of 35mm wide slit drains installed with 25mm perforated plastic piping could despatch surface water adequately to underground layers.

Furthermore, by confining drainage excavation to 35mm width the period needed to enable grass to cover the drain lines could be reduced significantly enabling use of the pitches as soon as possible.

Drilling bore holes gj-westminster-school-003Typical rock and waste fill

Drilling bore holes
Typical rock and waste fill