Drainage Strategy in line with SuDS:
Onn Point were instructed by a local developer to assist lifting conditions relating to drainage on a 4-house development based in Stourport. Our drainage strategy seamlessly integrated SuDS report principles, ensuring that the development aligned with the latest environmental standards and regulations.
Onn Point delivered a full detailed drainage design, suitable for construction along with associated soakaway calculations and construction details. Our drainage design specialist team prioritised sustainability, flood risk using flood risk assessments, and environmental preservation.
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Tell us about your site
Send us the site address and the condition wording, or the planning reference, and we will tell you exactly what is needed. If you do not need us, we will say so.
The engineering behind it
Four dwellings on a site where the ground ruled out the obvious answer before the design started.
Why a soakaway was never an option
The Phase 1 ground report found made ground and a high water table, which took infiltration off the table entirely. That put the scheme straight to a restricted discharge and meant the storage had to be found in the pipework rather than in the ground.
Controlling the discharge
Surface water discharges to the existing public surface water sewer through a 1500mm Hydro-Brake manhole limited to 5 l/s at 1.574m head, with the oversized manhole and pipework providing the attenuation. The connection is fitted with a non-return valve so the public sewer cannot back up into the site, and is subject to Section 106 approval.
Foul drainage
Foul water runs separately to the existing public foul sewer, also under Section 106, across a fifteen-manhole network serving all four plots.
The numbers
| Development | Four dwellings |
| Infiltration | Ruled out: made ground and high water table |
| Flow control | 1500mm Hydro-Brake, 5 l/s at 1.574m head |
| Attenuation | Within oversized manhole and pipework |
| Design event | 1 in 100 year plus 40% for climate change |
| Surface water outfall | Existing public surface water sewer, S106 |
| Protection | Non-return valve on the connection |
| Foul | Separate connection to public foul sewer, S106 |
Taken from the drawing set for this job. The scheme was approved at planning. Site named by town only; the client’s name and the full address are not published.