Geology..may need some help here.

[Sutol]

Geology..
We live on top of a hill but there is a hollow which always floods after a wet spell.
I believe that the reason for this is a layer of undulating clay under the top soil which holds the water in a sort of bowl and prevents it draining away.

Am I making sense ?

We have dug down 18 feet and got through the clay (this in the hollow) and struck sandstone.

Now we have a large deep hole with a sandstone bottom which we intend to fill with rubble.

Question is will this stop the flooding ? will the water drain away through the sandstone and on down hill away from us

Thanks

 

[crash325]

Geology..
We live on top of a hill but there is a hollow which always floods after a wet spell.
I believe that the reason for this is a layer of undulating clay under the top soil which holds the water in a sort of bowl and prevents it draining away.

Am I making sense ?

We have dug down 18 feet and got through the clay (this in the hollow) and struck sandstone.

Now we have a large deep hole with a sandstone bottom which we intend to fill with rubble.

Question is will this stop the flooding ? will the water drain away through the sandstone and on down hill away from us

Thanks

Am pretty sure you are on the right track. Depending on how big the area that you want to drain, be sure to uncover enough of the sandstone for it to drain.

Around my place at about 4 to 5 feet I hit what I call a separation layer. Its an open type of coleche (spelling ??), once it is uncovered you can run a hose in it full blast and never fill.

About 1/2 mile away I had to go down around 10' for the same thing.

 

[Sutol]

Thanks for the reply, we only uncovered about 10 feet by 8 feet and the hole is approx 15 feet deep.
The floor is sandstone and the machine broke the surface of it chipping the top couple of inches off.
We dropped about three tons of old brick and conctete pieces in but need tons more.

 

[Artisan]

I am not a geologist but introducing water into stratum that is not use to
it could have undesirable effects, as in slippage or creating a sink hole over
time or if you are on a well, it could add run off full of pesticides etc
into your aquafir. I would take good pics and post up on a geologist forum w/ coords and get some pro input. What do I know? :confused2:

 

[Sutol]

I am not a geologist but introducing water into stratum that is not use to
it could have undesirable effects, as in slippage or creating a sink hole over
time or if you are on a well, it could add run off full of pesticides etc
into your aquafir. I would take good pics and post up on a geologist forum w/ coords and get some pro input. What do I know? :confused2:

You may be right,

eighteen foot hole now has six feet of water in the bottom (where else:laughing
I asume that the water is draining out of the surrounding land quicker than it can escape through the sandstone base.

Please tell me I'm right

 

[Sutol]

Just as a matter of interest and maybe help sort out why ect

The house is built on sandstone and is approx 100yds from the hole.

Sandstone is a few feet below the house.

A well has been dug (in 1800's) outside the house and I have been down it. The well is brick lined for about four feet then is cut out of sandstone down for thirty feet. The bottom has a few feet of pure clean water in it and is a bowl cut into sandstone. Its about four feet in diameter all the way down.

The land falls away from the house and is approx six feet lower at the hole but the sandstone there is eighteen feet down so the sandstone must be a shelf that drops twelve feet in 100 yds.


BUT.... how come the well only fills to about 25 feet or so below the house yet the water in the hole is up now around eeerrrr.+ divide by eerrrr take away 12.....just answered my own question aprox twenty five feet below the level of the house, that must be saturation level of the sandstone..

Make a geologist yet:laughing:

Could not see how a well would work on top of a hill but the sandstone must suck the water up, thats my guess anyways.

 

[Fossil Farm]

Not sure about England, but around here there are many types of
sandstone. Some is porous, some not. Some hard, some soft. Some
good for building foundations, some not.

But if you are now introducing surface water into a former ground water
area, you may inadvertently contaminate the drinking water if your well
is not very far away. That would be my main concern if I lived there.
Surface water can have many contaminants - fecal matter, oils, etc. that
now has less layers to filter through.

If it is a bowl area you truly need drained, you may just want to put in a
subsurface tile with gravel on top (we call it a french drain) and outlet it
outside the bowl if there is sufficient fall and not too big of a hill to cut
through. Most 4 inch plastic tile can only handle around 6 feet of cover
in most cases. Clay, concrete, etc. can handle much more cover. Won't
go into much more detail here, but there are several places to get further
information on subsurface drainage. Again, my main concern would be
a possible contamination of the groundwater for the well. Good luck.

 

[powerpace]

I am not a geologist but introducing water into stratum that is not use to
it could have undesirable effects, as in slippage or creating a sink hole over
time or if you are on a well, it could add run off full of pesticides etc
into your aquafir. I would take good pics and post up on a geologist forum w/ coords and get some pro input. What do I know? :confused2:

I agree with everything stated.

Is there a problem leaving the water in the depression?
Where is your drinking water obtained.
Sewer location?
What is downhill from you?

 

[Sutol]

I agree with everything stated.

Is there a problem leaving the water in the depression?
Where is your drinking water obtained.
Sewer location?
What is downhill from you?

Water in depression is a pond when the weather is wet and dry when the weather dry.
When depression has water in it the surrounding land is wet, wet enough for the tractor to sink in places and we live on top of a hill.

The well isn't used any more and we use mains sewerage

Downhill is farm land on all sides, not ours I might add.

Hoping the land will drain quickly now after a wet spell

 

[Sutol]

Water in depression is a pond when the weather is wet and dry when the weather dry.
When depression has water in it the surrounding land is wet, wet enough for the tractor to sink in places and we live on top of a hill.

The well isn't used any more and we use mains sewerage

Downhill is farm land on all sides, not ours I might add.

Hoping the land will drain quickly now after a wet spell

Well it has rained some and the water level has stayed the same, need more rain though to see what happens

 

[Fossil Farm]

If the sandstone is not fractured, it may drain somewhat slow,
with the water just moving laterally (horizontally) on top of the bedrock.
Many times limestone is more fractured and drains quicker through
the rock, but you are stuck with sandstone.
Hope it works out for you. Good luck.

 

[Sutol]

If the sandstone is not fractured, it may drain somewhat slow,
with the water just moving laterally (horizontally) on top of the bedrock.
Many times limestone is more fractured and drains quicker through
the rock, but you are stuck with sandstone.
Hope it works out for you. Good luck.

Water level only rose a couple of inches after some rain and then went back down slowly to its level again so i think we may be in luck.
Wont know properly until we have several inches of rain though.

 

[blunosr]

Maybe someone has already said this, but it sounds like you have a perched water table (perched aquifer). Look up images of this on Google, and it will be obvious to you what that is. They're quite common.

Yup, I'm a geologist.

Bye for now,

Troy