The site. Land at Lanchester Way, Solihull (B36 9LE), where a proposed development needed soakaway testing before the surface water drainage could be designed.
What we did. On 8 October 2018, in light showers, we dug three trial pits in natural ground and set out to test each in line with BRE 365 and BS 6297:
| Pit | Width | Length | Depth |
|---|---|---|---|
| A | 350 mm | 1,100 mm | 1.5 m |
| B | 350 mm | 1,200 mm | 1.5 m |
| C | 350 mm | 1,000 mm | 1.6 m |
What we found. None of the three pits drained the initial 25% needed to start the timed tests, so testing was abandoned in each one. The ground was a sandy silt, and it behaved as cohesive ground, holding the water rather than letting it soak away.
What it meant. Soakaways were not recommended for this site. Our report pointed the surface water strategy to the next option: further investigation of a connection to the local public sewer.
The lesson. Three pits that agree make a clear answer. Sandy ground isn’t always free-draining, and it’s the test, not the look of the soil, that tells the engineer and the council whether infiltration works.
Need a percolation test for your own site? See how we test and report.