• New-build affordable housing: 92 houses on 1.1 hectares
• Flood plain development
• Severe design issues:
  • Discharge limited to 9.5 litres/second
  • Generated site discharge 154 litres/second
  • Existing ground levels to be maintained
  • Virtually flat site
  • Source control required
  • No raised traffic calming measures
• Final solution brings together both ‘hard’ and sustainable drainage techniques within an overall site strategy

Site and design constraints

• Site considered as a whole entity
  • all adoptable areas
  • all non-adoptable areas
• Drainage no deeper than 400mm
• On-line storage of 130m³
• Easily maintainable
• Restricted discharge

Principal Innovation: Hard / soft systems linking

Traditional drainage	Sustainable drainage
Pipes Combined kerb drains Channel drains Roof drainage	Storage Swales Filter beds

Learning points

• Sites such as Henry Box are likely to become increasingly common
• Drainage is always a critical issue
• Solutions can be found by integrating apparently disparate methods
• Positive and sustainable methodologies can complement one another
• Establishing multi-party dialogue early in the design process contributes enormously to success