Put simply it’s a drainage system for stormwater in the ground.
Many sites in Australia have a clay based soil making drainage after a heavy rain near on inpossible. Some lucky people have sandy sites where any rain quickly seeps into the soil and disappears. These folks rarely have to worry about when a heavy storm hits. The worst that happens is their soakwells fill up and the water over flows and spreads to the lawn.This can be seen here in a video clip I took of the Perth storm of March 2010. We were quite lucky and didn’t suffer any hailstone damage, but many are still getting over the damage left behind.
Those who live on a clay site know that the rain water doesn’t go away. It leaves lots of puddles for the kids to get muddy in for weeks to come.
In some new areas the developers have taken this in to consideration when preparing the block.Below is what sub-soil drainage looks like.
The site has been excavated and the drain laid. The idea is that the rain will seep through the top layer of soil and when it hits the clay it will flow into the drain and off to the nearest lake or park.
Speaking of parks being used for stormwater check these out…
This is a sale plan for some new development.
Here is what the site looks like during development in winter
This is the built park in March (end of summer) mostly dry...
And July (end of winter) soil saturated
It’s not that subsoil drainage is bad. It is really a good thing. The thing to watch out for, is if the subsoil drain falls within your property. There are requirements for how far away from it you can build. What you bought thinking was a 20metre wide block could turn out to be 17metres of actual buildable space, even though you’ve found the best house design for a block 20m wide and paid the full price for the land, you can’t actually build on it all.
