Borehole construction

 

GENERIC

How much would my borehole cost?
The cost of any borehole is dependent upon the hydro-geology at the site which will dictate the depth to which the borehole is drilled, access to the site and the working area. In the first instance please contact us for a free quotation, or simply a general chat.

How do I get a hydro-geological report on my site?
A prognosis can be obtained from the British Geological Survey (BGS) at Wallingford, telephone 01491 838 800. The current cost of a BGS repost is about £250 and is available in about 6-8 weeks. Before going to this expense however, if we have the relevant records we will be able to advise upon the hydro-geology without charge.

What do I get in a BGS Prognosis?
The BGS report will give an appraisal of the likely geological formation underlying the site. It will also refer to boreholes in the area with an indication of borehole depth, water level, yield and the aquifer penetrated; plus suggest a recommended borehole depth and diameter.

What about borehole contamination?
To prevent contamination from above (i.e. anything entering the borehole from an opening at ground level) all of our installations are fitted with sealed bolt-on covers, usually situated within a chamber, with the permanent lining tubes grouted into place.
As long as a site investigation has been conducted and there has been no previous record of contaminants being used on the site, contamination is only likely to occur if a contaminant flows through the aquifer from another source. Due to the rigorous BGS and Environment Agency legislation regarding contamination, this event is highly unlikely. If contamination does occur (say dumping old diesel in a ditch by a water course) and the culprit responsible is found then the fines can be severe.
It should be noted, however, that very heavy and consistent rainfall can raise chemical and sediment levels in groundwater due to the increased amount of flow.
SEE ALSO: IS THE WATER POTABLE?

How long does the whole process take?
This again will depend upon the hydro-geology at the site. Including for installation of the borehole pump and pressurised water system, anything from 1 week to two months is usual.

What type of rig would be used?
We drill using percussive techniques, which is the method preferred by the Environment Agency when drilling the chalk aquifer. This is particularly suitable for water supply boreholes as no additives are used during the drilling process and the drilling action ‘swabs’ the borehole, helping to clean and develop the fissures.

How long will a borehole last?
New boreholes should last for decades. We use strong steel or plastic liners in the construction of our boreholes.

SPECIFIC – WATER SUPPLY BOREHOLES

Will the water supply well ever dry up?
It is unlikely that a well drilled into the chalk aquifer will dry up. However it is possible that the amount of flow will reduce over time if the aquifers are not protected and too much abstraction occurs. This is why the BGS and Environment Agency work to log and enforce legislation designed to protect the aquifers. For domestic water supply boreholes we usually drill 25 metres below the water table or through the full depth of the aquifer.

Is the quality and quantity of water guaranteed?
There is no guarantee on the quality of the abstracted water. Educated guesses can be made as some aquifers are better documented than others; the chalk, for example, will generally give plentiful supplies of ‘hard’ water whereas the river gravels along the Thames will generally give plentiful supplies of water that can be high in iron. Sand holes are less prolific and can provide softer water that is also high in iron.
If a potable supply is required, suitability can only be confirmed following testing of the abstracted water by a professional water testing laboratory. Some filtration will be required. It is the clients responsibility to ensure that the water is tested regularly and that the local authority are aware of the abstraction for human consumption.
H.D. Services Ltd. guarantee what we term a ‘domestic supply’ which is up to 20,000 litres per day available from the borehole. We term it a ‘domestic’ supply as anything over this abstraction rate is classed by the Environment Agency as commercial and requires an abstraction licence.

Do I need a licence for my own well?
Unless you intend to abstract more than 20,000 litres per day, the Water Act of 2003 states that no abstraction licence is required. A family of five will discharge around 1m per day into the foul drain runs and hence an abstraction rate in excess of 20m is highly unlikely to be required.
If your usage exceeds 20,000 litres per day – normally a commercial venture – you will require an abstraction licence. Further information regarding licences can be found here.

Is the water safe to drink (potable)?
All water can be made potable by treatment, however this will have a cost implication, which will depend upon the amount of treatment required. The local Environmental Health Office is likely to recommend ultra-violet filtration irrespective of the results of analyses, as contaminants could be introduced to any aquifer several miles away.
If the water is to be provided to the public, then a full filtration and UV system should always be installed to suit the analysis results.

Is mains water better?
Over half of mains water comes from recycled waste water. Mains water contains chemicals such as fluoride and chlorine to ensure that the water remains at a satisfactory quality throughout its journey through the miles of pipework. With a little filtration, it is possible that your borehole could provide high quality drinking water.

Should I keep my mains connection?
We strongly recommend that you maintain your connection to the mains in the event of issues arising, such as pump failure, to ensure that you are never without water. While you would still need to pay the standing charge, you would not have to pay for any mains water unless you use it.

How much can I save?
This is dependant on your water usage. A domestic property with 3 people living in it will not use as much as a dairy farm. It has been known that some farmers have reported recouping their installation costs within a year. Those with a smaller usage will find it takes longer to recoup their costs. It is worth remembering that a borehole can be very useful if you are having trouble with your mains connection or are experiencing issues becoming connected to the mains . Some mains connections can be very costly requiring large amounts of pipework.

Can a borehole feed more than one property?
Yes. One borehole is capable of feeding more than one property, but a permit may be required and the local environmental health officer contacted. It is worth remembering that if the total requirement exceeds 20,000 litres per day then an abstraction licence will be required. It is possible that a water supply borehole could feed existing developments and new developments.

Do I need a water storage tank?
It is not always necessary and will depend on the water available and your water usage. In normal usage situations, the borehole pump and pressure vessel should be enough to ensure an adequate water supply.
In high water usage periods, where the available water is not sufficient to meet your needs, then a storage tank could be a good option.

What sort of pump do I need?
This depends on a few things. How deep the borehole is; what volume of water you expect to require and the amount of lift required to get the water to the surface. The deeper the borehole, the more powerful the pump will need to be.

Do I need a pressure vessel?
In order to ensure that there is even pressure across the whole system, a pressure vessel is generally used as it helps to maintain even water pressure (BAR). A pressure vessel will also prolong the life of the pump as it will not be required to switch on and off as regularly.

Will this ruin my garden?
While some mess is inevitable due to the nature of the work, we ensure that we leave the site as we found it. Boards are used to protect turf or paving where necessary.

What does it look like when its done?
The borehole is secured and covered by a lockable manhole cover. This it to prevent contamination and also to ensure the safety of the client. Any electrical works connected to the borehole are protected by the manhole cover.