Week 77, Day 5:

• More work on the swale for the rainwater drainage, sorting out the western (outlet) end
  • The structural engineer who designed the swale wasn’t able to predict to what extent it would act as a soak-away hence they needed to specify an outlet
  • In theory an outlet is required because a swale is primarily a means to transport water, not to disperse it – the idea is that the grass growing in the swale will slow the flow of water but it will still travel the 50m to the far end and will then need somewhere to go
  • A 60mm orifice plate (not yet installed) will restrict the flow from the outlet, so in the event of a huge storm the water will back-up and then disperse gradually
  • There’s a flap valve on the far end of the pipe to prevent water flowing back into the swale in the event of the ditch getting blocked

Week 77, Day 5

Dam wall at western end of swale; orifice plate not yet installed on outlet

Swale outlet to field drainage ditch, with GRC head wall and flap valve

Week 77, Day 4:

• More work on the swale for the rainwater drainage, connecting up the inlet pipework
  • The swale inlet is a precast concrete unit from ACO, specifically designed to slow down the incoming flow and spread it out sideways to avoid eroding the soil to create a single narrow channel – more info at ACO SuDS Swale Inlet
  • This looks a bit odd – especially when it first turns up in a Google search – but it does the job very well and there aren’t many alternative precast units in such a small size (this takes a 160mm pipe but a lot of them are designed for large housing developments with much bigger flow volumes)

Week 77, Day 4

Underground pipe to swale inlet

Precast concrete swale inlet (ACO SuDS Swale Inlet)