Clay Soil Which Stays Damp & Doesn't Drain Water!
HHHamster
Posts: 2
HI All, First post so please go easy 
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I moved into a property last year where the rear garden is in a fairly low flat area adjacent to some allotments. The garden is south facing and there are some trees to the rear which cause some shadowing though we recently had these reduced to allow more light onto the garden.
The problem I am having is that the soil in the garden remains wet/soft for the duration of the year. Last summer when farmers were complaining the fields were cracking up and clay soil especially, my garden seemed to still be wet or even when the top soil was dry-ish after long periods without rain was still soft to the touch so we felt that we couldn't even sit on the grass.
I dug a hole at the bottom of the garden to test if there was any sub-surface which would allow water to drain better though after digging about 2 feet down I came across some sand. I filled the hole with water from the hose though to my surprise the water just sat there and did not drain away, I continued to dig down another 1-2 feet and the soil changed to a blue colour in parts though still didn't drain. The soil appears to be clay.
Does anyone have any advice as to how I could overcome the problem and give me a garden which I can actually sit on/use please as at present we feel we unable to use our grass even in the height of summer. Due to the damp we also have a large number of insects in the garden which makes it very difficult to stay out after 7pm or sunset.
I considered the following if you could share you thoughts please:
1) Build up the level of the garden with a walled section and add sand with new top soil. This would be an expensive option though I am concerned what would happen to water which drains through the top layers, would it cause any problems as the water would still not penetrate the clay soil underneath and could this lead to problems? What sort of depth would be required?
2) Add some water hungry plants like tall grass though these could only be placed around the perimeter and given the water does not seem to drain I wonder how effective these would be at draining the garden in the centre.
3) Dig a number of deep 600mm holes with an auger and fill with stones/sand to let the water drain into. Again though, not sure if these would likely just fill with water like a pond and leave puddles in the garden and how effect the water would feed into them. Would they dry out between rain/storms.
4) Dig up the entire garden and mix the soil with sand or other materials of your recommendation to give the soil some drainage though again I have the same concerns as above.
The grass area is small, about 6m x 8m, though I would really like to be able to use my garden so any help will be massively appreciated.
Many Thanks
Posts
Not easy as you already suspect none of the options will be particularly easy or cheap. You could try putting in land drains but the water needs somewhere to go to, a soakaway (a rubble filled pit) might work. A farmer faced with this would use a subsoiler- a torpedo shaped plough that is dragged through the soil at subsoil level to create drainage channels you will have to dig! Raised beds could be the way to go, but use grit not sand to keep soil open. The blue colour subsoil/ clay means there is no oxygen there probably due to the waterlogging. It sounds as though your garden was once a natural pond if you have layers of sand & clay, on option could be to try water gardening - make a big (ish ) pond let the water fill to that then raise the rest of the garden to compensate.
Thank Iain. Is it likely that if I add a soak away under the garden itself that it would cause water to build up or does it need to be away from the problem area? I don't want to pull water in from adjacent gardens. I could fill the entire garden almost with a soak away and then imrpove the top soil (so not clay) for drainage into the soak away. I have seen soakaways for extensions when they are open and it would be pretty much the entire garden as I don't have anywhere else to put it. Also no where really to drain any channels to so maybe this is the only solution if it is a possible solution. As a minimum i think i need to change the top soil but Id like to know if creating soakaway under the top soil is likely to help. Probably better than nothing! This solution along with improved top soil for drainage does seem like a good idea though I don't want to create another pond. Yes, I did some research to identify the above options though it was difficult to find a reasonable solution.
Last edited: 29 November 2017 13:01:53
This is not a silly question. Where is the water coming from? If the area had drought but your grass was still very wet, it may not just be natural rainfall because even clay dries up under 'normal' conditions. Water may come from land higher than yours, from natural springs running under your property, from leaky pipes under your garden, from a stream or pond close by. The answer to this question will affect the solution. I would talk to some of the allotment people and to neighbours to find out if they also have a problem and what they know about it. A soak away won't work if water is coming from underneath, it will just create a sump - a pool of water - so it is worth some investigation.
I see lots of digging in your future,
I would find out where the highest and lowest point of your garden is as that's the direction land drains are going to go.
also find out if any land around you on the high point is higher than you as you'll be getting their water as well. you can either link your land drains into a sump or if you are really lucky you'll find a drain you can link into. unless you want a pond in your low point
the more you incorporate sharp sand/gravel/organic matter into the soil the better it will drain. organic matter can be added to the surface and the worms will drag it down (did you find many worms when digging, if not you might want to buy some in as sometimes clay soil can be so compact that the worms die off)
if you have money to burn I remember a household on Monty dons big dreams small spaces programme digging the entire garden out down to 4 or 5 feet and replacing the soil!