Flood Risk Assessment, SuDS drainage design, Thremhall Park
Oct 4, 2016

RAB Consultants have produced a detailed drainage scheme to manage surface water for a proposed new development in Bishops Stortford.

The proposal involved four business space buildings plus an extended car park. RAB Consultants therefore prepared a drainage design by:

  • Calculating the total permeable and impermeable area across the site, pre and post development.
  • Determining the sites existing rates and volumes for a range of rainfall events.
  • Providing a conceptual SuDS drainage design using microdrainage and proving detailed plans with a supporting report.

The design had to address the limitations of the site, including the unfavourable geology as it potential promoted low permeability and that rainwater harvesting is not sustainable at this site due to demand exceeding the yield. A SuDS treatment train was design using:

  • Storage systems in the form of an attenuation pond with pipe arrangements to control outflow
  • An oil interceptor to convey and treat the increased runoff as a result of the development

The scheme safely manages up to 1 in 100 annual probability rainfall, including an allowance for climate change and meets latest design best practice.