Tidal Water flooding on drive due to soakaway.

[Daveyp1471]

I live near the sea and up until recently when it rained I had terrible flooding on my drive way which is slightly slopped towards the house. There is a drain cut out into the drive which goes nowhere. Any way to prevent the water flooding on my drive I asked a builder to help install a soakaway. We laid the guttering and pipes to around 6 metres from the house and dug down just over 1 meter for the soakaway crate. The problem then started the following day, the hole that was dug filled up with water, it pushed water up the pipe and flooded worse than before.
Later that day the water in the hole dropped but around high tide time the following day filled up again, I could hear the water filling up as if a tap had been opened. The builder was puzzled and removed the crates and filled the hole with the mainly clay substances that we had dug out. The plan being we would move over and start to dig again but not so deep.
However the area where the hole was still keeps flooding and spreading across the front garden at high tide times, it didnt do this until i dug the hole.

How can i stop this from happeneing?
Thanks

 

[noseall]

You've hit a water pipe mate.

 

[JohnD]

it might still be a drain.

Where I sometimes live, there are lots of springs, streams and culverts running towards the sea. My neighbour's cellar floods at some high tides and in storms. It is with fresh water, not salt. I suppose it just can't flow away so it backs up.

I see from the tide table that high water was unusually high.


....today

 

[Daveyp1471]

No water pipe that i can see, was hand dug and only happens after high tide.
I need to know how to seal it up as before. Is it a case of just compressing the clay back?

John D it maybe an underground stream from the downs to the sea, i have not tasted it but it is pretty clear. Maybe I can bottle it

 

[Ian H]

Now you have dug it the water has an easy way up.

Compact it at low tide and if you try another soak away it should be minimum 5mtrs from the house.

 

[Daveyp1471]

Sorry it was 6 meters away, not sure why i wrote 3.
Any tips on compacting 1990 and should i add anything else like soil or sand?

 

[Doggit]

If it fills with the high tide, and drops afterwards, then it can't be a water pipe. But if you've dug down a metre, and it then fills and comes up to the house at high tide, then it would only be tidal water if the house were below sea level. It could be a stream that goes down t the sea, and it just below the surface of the hole, and it's now found the point of least resistance, but if that's the case, then you might find it difficult to dig elsewhere.

As 1990 says, you need to compact the earth at low tide, but I suspect you'd still have a problem, so you may need a Cu Mtr of concrete, except if it's stream f some sort, that could divert it and cause other problems. You may need to redig the hole a little deeper, and then watch the hole as the tide come in - and taste it.

 

[Ian H]

Defiantly a trench foot, I'm not sure of the proper name. We call them a McDermotts Motorcycle at work, named after one of the lads.


Your best off compacting it in 250mm layers really and once the ground has been broken it may never be the same again but you have a good chance with it being clay.

 

[Daveyp1471]

Thanks all, 1990 would you use a whacker plate or will good old boot suffice?

 

[Ian H]

Not a wacker, I'll try and find a pic of the thing I mean.

 

[Ian H]

Googled trench foot. Definitely don't want that!!!

This is the one:

There are manual ones too, basically a metal shaft with square lump on the end.

 

[Daveyp1471]

how deep will that work. My metre deep hole is full now so how much would i need to remove to effectively compact?

 

[Blagard]

To be honest if you try to compact material you need to work in much thinner layers 250mm is far to much. On major sites using really heavy plant the thickness is usually around 150mm so for what you plan to use no more than 100mm. I don't reckon much on your chance of getting it back as it was. If you can find the impervious layer in the pit walls then you should try and follow that with impervious materials like clay then backfill on that the rest. Then keep your fingers crossed!

 

[Ian H]

I'd go 250mm but that's just my opinion.

 

[Blagard]

I'd go 250mm but that's just my opinion.

Thats OK but if the OP is looking to get as near to the original impervious layer as possible then the most likely layer will be any clay. Unfortunately it is also a most difficult material to compact and you certainly won't even give yourself a chance if you try to do it in a thick layer. Backfilling in places where there is either no traffic or other need for a high level of compaction will probably be fine with your 250mm. It really comes down to the materials being used and end purpose when considering layer thickness.