Anyone know about water tables / excess ground water? Please!!

[TommyKnocker]

1930's house, lived here for a few years. Aware the street is built on streams but there has never been any flooding, although the lowest area of the garden was always a little waterlogged but nothing major. We had an extension built last year to the higher side (house is on a slope with one side being higher than the other), when the builders knocked down the garage and dug down for the foundations they discovered lots of standing water. Bit of a discussion and builder suggested piping the water to a soakaway at the back of the house so they could get the foundation in. Fast forward and clearly the soakaway is failing, it's under a raised patio with lower ground around it and there is water ebbing out some towards the house, some towards the back corner where it is pooling and some out of our boundary into a wooded area.

I've tried talking to the builder who just said it's what is to be expected as there was so much water within the ground however I'm concerned about the water getting stuck next to the house and causing foundation issues. I feel like I maybe need to speak with the council or environment agency for advice as its probably caused by a high water table but I'm concerned what they may do in terms of the building work we've had done. It's been signed off by building regs who visited the site a few times. Obviously it needs dealing with but I'm worried about involving the council and wondered if anyone had any advice / suggestions?

I work for an environmental consultancy and our flood risk department would look into that kind of problem and advise on works required to remedy it. I don’t think the council or environment agency would be of help.

It might be worth getting the local water company out to check for leaks. Sometimes if they're not sure they can test it for chlorine content (mains water) and/or ammonia (generally found in waste water). If it doesn't contain either then it's usually from a natural source like a stream or spring.

What do you mean by the street being built on streams? Is there a culverted watercourse under/near the property? If so the culvert might have failed and that could be something the council would look at. Have you noticed of the water is seasonal or linked to rain? After winter groundwater is closest to the surface in many parts of the UK, so you might find it gradually dries from now.

I echo the previous posters. Environment Agency won't be concerned unless the course of a river has been altered or blocked, or there is pollution to the groundwater.

You could check with your buildings insurance and if they think it is a risk to the property they can get consultants to do an assessment of what the cause is and what is needed to resolve it.

Did the builders do a soakaway test to establish whether a soakaway would be feasible? Did they check the level of the water table at the proposed soakaway location at the time? Is the soakaway at least 5m from the property?

I would suggest contacting a civil engineering consultancy with knowledge of local ground conditions.

@TheAbbotOfUnreason I doubt they did a test to see if it was feasible. It's also not 5m, it's about 3.5m. TBH I'm not sure a soakaway is the right thing to have used anyway as from my research they are only really used for rain water run off rather than diverting underground water. At the time he told us the issue and how he was going to deal with it and I didn't really look into it - which is totally on me. I'd not actually heard of a soakaway before.

I think our main difficulty is that we don't know if the water that's been diverted is a set amount. If it was we can drain it and maybe set up some channels away from the house to an area set up to deal with water. But if its an ongoing stream that's more difficult. There is a constant stream of water up the road which just seems to appear out of the concrete at the side of the road and trickles into an open drain about 10 feet away. It never fully disappears even in high summer but doesn't seem to cause any issues because it's always got somewhere to go.

@DogDaysNeverEnd the whole area is old mining ground and is just said to have streams underneath. TBH I never really questioned that fact it's just been said by people in the area. There are no nearby overground streams or ponds. We boarder a large wooded parkland.

@TheAbbotOfUnreason I doubt they did a test to see if it was feasible. It's also not 5m, it's about 3.5m. TBH I'm not sure a soakaway is the right thing to have used anyway as from my research they are only really used for rain water run off rather than diverting underground water. At the time he told us the issue and how he was going to deal with it and I didn't really look into it - which is totally on me. I'd not actually heard of a soakaway before.

I think our main difficulty is that we don't know if the water that's been diverted is a set amount. If it was we can drain it and maybe set up some channels away from the house to an area set up to deal with water. But if its an ongoing stream that's more difficult. There is a constant stream of water up the road which just seems to appear out of the concrete at the side of the road and trickles into an open drain about 10 feet away. It never fully disappears even in high summer but doesn't seem to cause any issues because it's always got somewhere to go.

@DogDaysNeverEnd the whole area is old mining ground and is just said to have streams underneath. TBH I never really questioned that fact it's just been said by people in the area. There are no nearby overground streams or ponds. We boarder a large wooded parkland.

Hi! Did this ever get resolved? My friend is having an issue with her neighbour who is saying that her garden landscaping is causing flooding when it rains. But the water company have been and said there's no blockage or flooding from anywhere just a Ground Water issue. They live on a hill if that's relevant

@tryingsomethingnew we did get it sorted but from what your describing, it sounds quite different from your friend.

Our issue was an underground stream, which we've redirected. Your friends issue sounds like she may not have put in adequate drainage when she landscaped, there are loads of solutions for this, french drains, soakaways etc. The landscapers should have advised her of this, I think the neighbour is well within her rights to complain if your friends works have created a flooding issue.

I would get your friend to either get the original landscapers back out or someone new to advise of solutions and apologise to her neighbour and tell her she's working on it.