Soakaway problems in Kent.
We get many phone calls from people saying that someone has installed a soakaway for them but it isn't working. Quite often the soakaways are installed without any testing being carried out in soils that are not suitable and are therefore doomed to failure. It is vitally important that any potential excavation for a soakaway is tested prior to installation, if the ground is not permeable there is no point in installing it. You must make sure that your contractor carries out tests to prove the permeability of the geology before going through the additional expense of an installation.
Our solution is to drill a deep bore soakaway which will penetrate through the clay or impermeable strata and into a permeable geology which will disperse the water through an installed liner. We are based in Kent where there are mainly two types of geology. The first is Chalk, but in many areas it is covered by head deposits which are usually brown clays with occasional flints. The clay covering may only be a few centimetres, but in certain areas can extend to over 20 metres in thickness. Water cannot penetrate the clay and so the drain will eventually fill up. By drilling through the clay we can install a liner which is a direct link from the surface to the chalk. Chalk is actually an impermeable strata but it is very fractured particularly in the first few metres which will allow water to drain away at rates of in excess of 10 litres per second in some circumstances. No pumps are required and the installation is maintenance free.
The other main type of geology in Kent is "The Weald", this is in the West of Kent and generally speaking is an area where the upper geology such as the chalk has been eroded away and you are straight into a variety of underlying geologies dependant on where you live. There are certain areas where layers of Weald Clay are over 100 metres in thickness and are therefore not suitable. Many areas though have geology comprising layers of fractures rock such as Tunbridge Wells Sands which again are very permeable.
To find out what is beneath your property, send us an email with your contact details and postcode and we will commission a FREE Borehole prognosis using our extensive geological data. You will then be in a position to know whether this solution may be suitable at your property.
Many new housing developments are now not allowed to connect to already overloaded storm drains and this is the only solution that is acceptable to Building Control and The Environment Agency.
Take a look at our section on Deep Bore Soakaways for a more detailed description.
Case Studies of soakaway problems.
1: We were called to a clients property where he had a soakaway in the garden which was overflowing, the lawn was water logged. The soakaway was constructed using precast concrete rings. This soakaway had failed a couple of years before and he called in another drainage company whose solution was to dig a massive hole next to the soakaway and fill it with hardcore, this cost thousands of pounds and a year later the new soakaway was also full of water. We proposed to the client that we would drill a deep bore soakaway and then connect the overflow pipe from his existing soakaway to the new deep bore soakaway. We decided to drill the borehole 10 metres away from the existing soakaway to avoid the land drain. We started drilling and after only going down 0.50 metre we hit water and hardcore. The natural geology in the area was clay over chalk so we assumed that the previous contractor had indeed excavated a very large "soakaway". The hard core fill extended to over 4.00 metres in depth and was full of water. We cased off the excavation with temporary steel casing and drilled into the natural clay to seal the water off. We continued drilling and went through the clay at 10.90 metres and went into chalk, We then advanced the borehole to 20 metres into the chalk and tested the permeability. The permeability was excellent so now all we had to do was connect the existing soakaway to the deep bore soakaway and the job would be completed. However, there was still the problem of the water logged garden and the excavation which was full of water. So we decided to do something a little different to the normal installation. We installed the deep bore soakaway with a perforated section in the permeable chalk, and would normally have had plain casing in the impermeable layer, but this time we also put a perforated section from 1.20 metres to 4.20 metres with a 250 micron wrap to prevent the ingress of silt and sand into the deep bore soakaway but still allow the water to pass through freely. When the temporary steel casing was removed the deep bore soakaway drained the excavation and land drainage. There was no need to connect the overflow pipe from the existing soakaway as the excavation with hardcore fill could now readily accept vast quantities of water even in times of prolonged heavy rain. The client was delighted as we had not only solved his soakaway problem, his garden lawn was no longer water logged.
2: We do many deep bore soakaways for housing developments. Storm water drains in many areas of the country are already overloaded and new builds now have to make provision for storm water without connecting to the already overloaded infrastructure.
The storm water from the housing estate is directed to an attenuation chamber constructed of precast concrete rings (Milton Rings). A deep bore soakaway is then drilled and installed through the base of the chamber to allow the water to permeate away at depth.
3: Many Klargester or similar types of packaged sewage systems are so efficient that the water produced after processing is almost pure, but there is still the problem of disposing of it. A deep bore soakaway can be drilled next to the Klargester and an overflow pipe can be connected directly to the deep bore soakaway, this will again solve the problem of getting rid of unwanted water.
4: Existing soakaways built using precast concrete rings tend to fail due to a build up of silt and clay which is washed into the chamber over many years, the silt and clay eventually settles and forms a seal at the base of the chamber and eventually will not allow the water to pass through. You may be able to dig out the chamber but quite often the silt has sealed all of the fissures or porosity of the geology for a considerable distance from the base. One should also bear in mind that it is dangerous to enter a chamber as it is a confined space and could house harmful gases which may cause asphixiation.
A better idea is to drill a deep bore soakaway, this will not only get rid of the water without having to enter the chamber, but when installed the installation is left 1 metre proud of the base of the chamber. This allows silt to harmlessly accumulate at the bottom of the chamber and has no effect on the drainage of the water. The installation is also fitted with a syphon head which will prevent any debris which my float such as leaves entering the soakaway installation. We have a slide show of a precast chamber showing a before and after installation.