Channel drains, soakaways and clay soil...

[Voidcomp]

OK, this one may just prove I'm a hopeless optimist/newb....again, I'm a relative novice builder with experience of drives, walls, but no experience buildings/drainage (other than a French drain I put in once).

I'm planning to build a garage at back of garden onto a shared drive. Because I'm on a hill with a 3% gradient, running downhill towards the garage entrance, I would like to fit a channel drain the width of the garage entrance, to stop the water flooding into the garage when we get downpours.

Problem: I've got clay soil and there's no storm drain/sewer even close (this is a rear shared driveway at back of house).

I'm aware there may be limitations with soakaways in clay soil, but is there anyway this can be made to work? If not, what (if anything) is the best solution?

Finally, I suspect this is a non-starter, but have just got to ask: am I right in assuming that it would be completely insane to site a soakaway deep under the garage floor? Reason is that garage will be the entire width of garden, so any soakaway will either need to be there, or 15 meters away from the channel (nearest distance after clearing garage building and proposed patio).

Again, thanks for help with my questions, all comments and criticism welcome.

 

[Voidcomp]

Don't all rush at once guys and gals....

 

[r896neo]

You can not have a soakaway under a garage. You could should you so desire have a rainwater harvesting system tank under there with associated gubbins, but you need an overflow for that which would need to discharge to a soakaway or sewer anyway.

A soakaway may well be pointless in heavy clay and therefore your only other option would be to run the water off the surface and round a corner to a bed or lawn etc, depending on the surface area being drained this may not be suitable but for a small drive it would probably be ok.

Probably worth digging a test pit/hole to check water dispersal in the ground.

 

[Voidcomp]

Thanks, yes I was fairly sure it couldn't be done, but it doesn't cost much to ask. I know what's under the soil, and the "bedrock" on the Geological map is clay, so no point in test drilling (unless I'm going to drill for oil).

Looks like I'm running a long pipe to the inspection pit. Thank goodness it's downhill.

 

[Mrdjc]

Like mentioned above, it really depends on what exactly is below your feet!

Dig a test pit about 1 to 1.5M down and see what you find. If its solid clay there's not much you can do.

If you find sand and water perculates from the bottom up, again, not much you can do.

Otherwise only two real options I can think of, one is to have a storage tank, the other is to find a lower spot than the drain to have it discharge to.