Soakaway/Infiltration Test

GEMCO are able to undertake soil infiltration tests (soakaway). These are completed in accordance with BRE Digest 365.

Soakaways have been the traditional way to dispose of stormwater from buildings and paved areas remote from a public sewers or watercourses. In recent years soakaways have been used increasingly within urban, fully sewered areas to limit the drainage impact of new buildings and to avoid costs of sewer upgrading outside a development. Soakaways are seen increasingly as a more widely applicable and sustainable option alongside other means of stormwater control and disposal.

  • Trial pits are excavated;
  • Vertical pipes are positioned in the pit so that water levels can be monitored with a dip tape;
  • Trial pits are filled with clean gravel (20mm) to ensure sidewall stability during the test;
  • A sufficient head of clean water is added from a rapid filling water tanker or bowser;
  • The soil infiltration rate is determined by measuring the length of time for 75% of the volume of water to drain away;
  • Three consecutive tests should be undertaken within each location (at least one full test is completed within saturated soil conditions);
  • The calculated soil infiltration rate is used to determine the feasibility of soakaway drainage, the design storage volume and the number of soakaways required.