Drainage Planning Services
Civilistix Consulting Engineers were appointed to prepare a Detailed Surface & Foul Water Drainage Strategy. This was to support a planning submission for a proposed extension to an existing care home, as well as associated external hardstanding areas.
A ground investigation was carried out and it was found that the use of infiltration to dispose of surface water was not possible due to the silty clay soil conditions and the site being located on London clay. There was no watercourse nearby the site. Due to this we proposed the discharge of surface water would be via the existing private surface water system, which discharged to the Anglian Water sewer within Sewardstone road.
It was proposed that all runoff from the proposed impermeable area was attenuated and controlled to 2.0 l/s for all storm events up to and including the critical 100 year plus 40% climate change event. It was proposed the full external hardstanding area would utilise tanked permeable paving construction. This would accommodate voided Type 3 sub-base material, allowing for the treatment of runoff and attenuation storage volume so that the control rate of 2 l/s could be ensured.