The Brew Cabin

Tony, Good Luck!
I have cut into the down gradient at the top of the garden for landscaping, which has lead to percolation of water looking for a route down the slope (heavy clay).
Could I install the 80mm perforated pipe at the appropriate depth to deal with that water, and then further down the garden, bury the pipe a few inches below the surface all the way down to the outfall (which will be the rainwater gulley)?
Would that have the effect of collecting the water and then as it makes its way down the pipe,soak into the dryer areas down the garden.
I am pretty sure it is my landscaping that has made the problem worse and if it had been left, the excess water would have drained away without the need for the land drainage.
Please, also I am remaking a sunken pond at the top of the garden, near where the water is showing. Before, I made a bit of a feature of allowing the ground water to trickle into the pond. The water brings the fine clay with it and clogs up the pond. That's why I am remaking the pond. Would there be any other issues as the shallow dug land drain will be passing the pond. Lower, of course, than the brim of the pond?
Regards.........Vince.

A perforated land drain will 're-distribute' the groundwater, Vince, but it's not as effective as you might be tempted to think. It's far more efficient at collecting excess than irrigating, but it will work to some extent. It's imperative that you keep a connection to a proper outfall, such as the gully you mentions, as, when it's really wet, the 'drier area' might not be all that thirsty!

To cut down on the amount of clays and silts washed out by the land drainage, use a separation membrane - Terram 1000 is fine - as this will filter out the smaller particles. In a year or so, as the ground settles after all your recent landscaping work, there will be much less clay/silt being carried by the system, so your pond should clear.

1) Can I assume then, that water collected in the pipe has more of a tendency to pass down it to the outfall, than pass out to the "drier" areas and cause saturation locally?
2) How would I overcome the problem of a terrace of two steps deep when running the pipe. would it be acceptable to have a short vertical run down the terrace (in the corner hidden with bushes). If I tried to maintain the run, I think I would be digging down about 6 feet. Not an option!
3) I had been trying to get my LA to take responsibility for this water for the last 2 years. There is a park across the back (higher elevation) and I know the surface water drainage system is not working properly. They had CCTV in the drains and reckoned tree roots had blocked them. They backed off though, saying that there will always be ground water to some degree. Tony, I was wondering how you have found LA's attitude to this sort of thing. I can't chase them anymore now. I've got to finish this garden!
Regards Vince........................

1 - water will always take the path of least resistance, which is, usually, an outfall to the sewers system rather than absorption by the surrounding ground.

2 - rather than a short vertical run, try to 'ease' the level change a couple of metres either side of the steps. So, from the vevel of the drain 2 metres from the steps on the uphill side, dig your trench to the required level at a point 2 metres downhill from the steps - do you understand that, or do you want a quick sketch?

3 - LAs are a law unto themselves and, if you get stroppy, they can always get stroppier still. If you could show, without a doubt, that the Park was draining into your property and causing damage, then you could compel the LA to install an interceptor drain at the boundary. However, they are right when they say that there will always be some groundwater, and it's only in cases where you can prove that some change they have made to the park, such as surfacing or digging out tree stumps, has caused a worsening of the problem on your property that you would have a viable case.

It's always a more productive policy to be as nice as ninepence to the LA. They can be very, very helpful and save you a small fortune, as long as you handle them correctly. If you can make a reasonable case for them to install an interceptpor drain, 9 out of 10 LAs would do so, but, if you start stamping your feet and threatening this, that and the other, they'll just drag the whole thing out for years.