Case study
A drainage strategy for 2 dwellings in Albrighton, Shropshire, prepared for planning and approved.
The constraint
Infiltration testing on site confirmed the ground would not take water, so a soakaway was not an option. That ruled out the top of the drainage hierarchy and set the shape of everything that followed.
What we did
Attenuation storage of 11.46m³ was provided for the 1-in-100-year event including a climate change climate change allowance.
The numbers
| Discharge rate | 2 l/s |
| Attenuation storage | 11.46m³ |
| Attenuation tank | 2.5m x 6.0m x 0.8m deep |
The kind of condition this discharges
Wording differs between officers, but a scheme like this one is normally answering a condition along these lines:
No development shall commence until a detailed surface water drainage scheme, demonstrating that surface water will be restricted to greenfield run-off rates for all storm events up to and including the 1 in 100 year event plus an allowance for climate change, has been submitted to and approved in writing by the Local Planning Authority.
The greenfield run-off calculation and the attenuation volume are what answer this one. There is a fuller guide to discharging drainage planning conditions if you want to read up on the process.
Outcome
Hydraulic simulation showed no flooding in the 1-, 30- or 100-year storm events, including the climate change allowance. The scheme was approved at planning.
Every scheme in these case studies was approved — that is the point of the exercise. If you have a drainage condition to discharge, send us the wording and the site address and we will tell you exactly what is needed.
Browse the rest of our case studies, see what a drainage strategy involves, or find where we work.