Soakaway installation in Leicestershire

Leicestershire ground and infiltration

Much of Leicestershire is clay. Mercia Mudstone underlies Leicester and the west of the county, Lias clay runs through the east around Melton Mowbray and High Leicestershire, and glacial till covers large areas on top of both. Those soils take water slowly, if at all.

There are better pockets. The river gravels along the Soar and the Wreake, and the sand and gravel spreads left by the ice, can drain well. Two plots in the same village can give very different results, which is why a soakaway here is designed from a test on the actual site, never from a geology map.

Percolation testing and BRE 365

BRE Digest 365 is the standard method for testing infiltration and sizing a soakaway. A trial pit is dug to the depth the soakaway will sit, filled with water and timed as it drains, normally three times in a row. The time it takes to fall from 75% to 25% full gives the soil infiltration rate, and the engineer uses that rate and the design storm to size the structure.

The test and the calculation come from your engineer or site investigation, and we build to the results. If they look marginal, we'll say so before anything goes in the ground. A soakaway in tight clay just fills up and stays full.

When a soakaway is the right answer

Infiltration sits near the top of the SuDS hierarchy. The 2025 national SuDS standards, the NPPF and Approved Document H all expect surface water to go back into the ground where the ground allows it, before a watercourse or sewer is considered.

Where testing rules infiltration out, the usual answer is an attenuation tank with a controlled discharge. We install both, so the engineer's choice doesn't change who turns up on site.

What we do on a Leicestershire job

Crates and geotextile can come from us, matched to the design, or we'll fit materials you've sourced yourself. Either way, the work on site runs the same:

• Confirm the volume, depth and layout against your engineer's drawings before the dig
• Check the pit your groundworker has formed, so the crate structure sits true
• Line the pit with permeable geotextile to keep fines out while water passes through
• Build up the crate block to the volume and load rating the engineer has set
• Connect the inlet and silt management, close the wrap and hand over ready for your backfill
• Leave you inspection records and a handover file ready for building control