Drainage Impact Assessments
Drainage strategy reports for planning applications - existing assets mapped by CCTV, flood risk assessed, SuDS proposed and discharge rates calculated.
Planning authorities and water companies increasingly refuse to consider a development until someone shows, with evidence, how its foul and surface water will be managed without increasing flood risk. That document is a Drainage Impact Assessment (or drainage strategy report), and the reason ours hold up is that they are built on measured site data rather than desktop assumptions.
What goes into the assessment
- Existing infrastructure, mapped for real: chambers lifted, inverts measured and runs traced by CCTV survey - water company records are routinely wrong about private drainage, and a strategy built on them inherits the errors.
- Site levels: from a topographical survey where the project needs one, so flows and gradients are calculated on measured ground.
- Infiltration evidence: BRE365 testing to prove whether soakaways are viable, before the strategy commits to them.
- SuDS proposals and calculations: attenuation volumes, permissible discharge rates and the drainage hierarchy worked through in the order local authorities require.
One contractor, measured inputs, defensible report
Because we do the surveys, the testing and the reporting ourselves, the assessment is internally consistent - the levels, the infiltration rate and the drainage plan all come from the same visit and stand up to a planning officer's questions. Where the strategy leads to physical work, the same team prices and builds it, from soakaways to new connections.
Planning condition asking for a drainage strategy?
Call Clever Works on 01252 917235 or request a fixed quote - send the planning condition or the architect's brief and we will scope the assessment to satisfy it.
Need Expert Assistance?
At Clever Works, we provide comprehensive drainage solutions with transparent pricing and no hidden fees. Get in touch today for a free, no-obligation quote.
Frequently Asked Questions
When is a Drainage Impact Assessment required?
Typically for new builds, significant extensions and any development that increases impermeable area - either as a validation requirement or as a planning condition. The wording of the condition tells us the scope; send it over.
What makes your assessments different from a desktop report?
Measured inputs. We survey the existing drainage by CCTV, measure levels on site and test infiltration to BRE365, so the strategy is built on evidence rather than water company records and assumed rates.
Do you handle the SuDS calculations?
Yes - attenuation volumes, discharge rates and the drainage hierarchy are worked through and presented in the format local authorities and lead local flood authorities expect.
Can you also build what the strategy proposes?
Yes. Soakaways, attenuation, new connections and build-over evidence are all work we do ourselves, so the strategy is priced by the people who will deliver it.