Borehole Service Utilities Ltd drills water boreholes across Buckinghamshire, from the Chiltern chalk in the south of the county to the limestone and clay of the Vale of Aylesbury and the north. The company installs private water supply boreholes for houses, farms, estates and businesses, irrigation boreholes for gardens, sports grounds and nurseries, soakaway boreholes for surface water, and off grid solar-powered pumping systems. It also fits filtration and treatment, and services, tests and repairs boreholes that somebody else drilled.
Buckinghamshire is good borehole country, but it is not uniform country. Under the Chiltern plateau and the Misbourne, Chess and Wye valleys the bedrock is White Chalk, one of the strongest aquifers in England. At the foot of the scarp at Princes Risborough and Wendover it is the poorer Grey Chalk. In the south-east corner around Gerrards Cross, Iver and Denham the Chalk lies buried beneath London Clay and the Lambeth Group. Much of the floor of the Vale is mudstone. What a site will give depends on which of those you are standing on.
Private water supply boreholes for homes, farms and estates in Buckinghamshire
A private water supply borehole gives a property its own water, drawn from the rock under the site rather than from the mains. In Buckinghamshire that suits off-mains houses in the Chiltern valleys, working farms in the Vale of Aylesbury, country houses with large grounds, and businesses with a heavy daily demand. Mains water in the county comes from more than one company, with Thames Water, Affinity Water and Anglian Water all operating here depending on where you are, and Buckinghamshire Council defines a private supply simply as one that is not provided by a water company.
A borehole supply can run a whole house, livestock drinking water, yard washdown, glasshouses and irrigation, either on its own or alongside a mains connection. Once the borehole, pump and treatment are in, the running cost is the electricity to lift the water and the upkeep of the filtration. A temporary use ban applies to a water company's own customers rather than to a private supply, which is one reason farms and properties with a lot of ground under irrigation ask about boreholes first.
The honest part is that yield is decided by the rock, not by the wish. Borehole Service Utilities Ltd starts with a desk study of the geology under the site, drills, then develops and test pumps the borehole to establish what it will actually sustain before any pump is sized. Water is sampled and analysed, treatment is specified from the results, and the supply is registered with Buckinghamshire Council, which keeps a register of private water supplies and offers risk assessment and sampling.
What is under the Chilterns, and how deep is a borehole in south Buckinghamshire?
Across the south of the county the target is the White Chalk Subgroup, and it is a strong aquifer. BGS 1:50,000 mapping puts White Chalk beneath High Wycombe (HP11 to HP13), Amersham (HP6 and HP7), Chesham (HP5), Great Missenden (HP16), Chalfont St Giles (HP8), Marlow (SL7), Bourne End (SL8), Beaconsfield (HP9) and the high plateau at Stokenchurch (HP14), usually under a cap of Clay-with-flints. The Chess, the Misbourne and the Wye are chalk streams fed by the same groundwater, and a large part of southern Buckinghamshire sits inside the Chilterns National Landscape.
Depth is set by where the water table sits, not by the postcode. BGS sheet 255 puts the unconfined water table at roughly 130 metres above Ordnance Datum beneath the Chilterns, falling to about 20 metres above OD at the River Colne. Read against local ground levels, that points to something in the order of 60 to 150 metres on the high plateau around Stokenchurch and Naphill, and perhaps 30 to 80 metres in the incised Misbourne, Chess and Wye valleys. Those are planning figures only. No published table of domestic borehole depths exists for Buckinghamshire, and the survey sets the real number.
Position matters as much as depth. The BGS memoir for the Beaconsfield district records transmissivity of 500 to 2,000 square metres a day in the valleys against only 15 to 100 square metres a day beneath the interfluves, so a valley-floor site and a hilltop site a couple of miles apart are not the same job. Two parts of the south need particular care: the scarp-foot towns, where the Grey Chalk is a weaker aquifer than the plateau chalk, and the south-east corner, where the Chalk is confined under clay and has to be reached through it.
The formations Borehole Service Utilities Ltd expects to meet in south Buckinghamshire, as mapped by BGS at 1:50,000 scale:
- White Chalk Subgroup, the Lewes Nodular, Seaford and Newhaven Chalk formations, under Clay-with-flints at Amersham, Chalfont St Giles, Stokenchurch, Beaconsfield, Seer Green and Jordans.
- New Pit Chalk Formation at High Wycombe, Chesham, Great Missenden and Marlow, with alluvium along the valley floors.
- Grey Chalk Subgroup at the scarp foot: West Melbury Marly Chalk at Princes Risborough (HP27) and the Totternhoe Stone at Wendover (HP22), both poorer than the White Chalk above.
- London Clay Formation over confined Chalk at Gerrards Cross (SL9), Iver and Iver Heath (SL0) and Stoke Poges, so the drill passes through clay before it reaches water.
- Lambeth Group over confined Chalk at Denham (UB9), Burnham (SL1 and SL2), Farnham Common and Fulmer, where sandy horizons hold only small supplies.
- River terrace and plateau gravels: Taplow Gravel at Marlow and Denham, Beaconsfield Gravel at Beaconsfield, Lynch Hill Gravel at Iver and Shepperton Gravel at Bourne End.
The Vale of Aylesbury and north Buckinghamshire: limestone islands in a clay floor
Aylesbury is not the clay-vale town people assume. BGS mapping puts the town centre, Walton and Hartwell on an outlier of the Portland Stone Formation, with Kimmeridge Clay picking up immediately north of the town. A borehole in HP20 may find limestone while one a short distance north has to pass through mudstone. The same Portland limestone caps the higher ground at Haddenham (HP17), Long Crendon and Cuddington (HP18), Dinton and Whitchurch, with the Purbeck Group at Stone and capping the hilltop at Brill, where the village itself stands on the Whitchurch Sands Formation.
These limestone islands are thin, local and often perched, and they deserve honest treatment rather than a sales pitch. BGS notes for the Stone area record springs and seepage around the margin of the Portland outcrop, shallow wells that tapped the same water, and the plain statement that much of the area is underlain by mudstone and therefore has little groundwater potential. The same notes describe an exploratory borehole at Stone Hospital that was drilled more than 157 metres below the base of the Portland beds, reached the Great Oolite and still failed to yield useful quantities of water.
North of the Vale the picture changes again. Buckingham (MK18) sits on the Forest Marble Formation, part of the Great Oolite Group, which BGS names as the main aquifer of that district. Stowe is on the White Limestone Formation, recorded as giving high yields, while Maids Moreton and Tingewick sit on the Cornbrash, which gives low ones. At Winslow, Padbury, Steeple Claydon and Wing (LU7) the Great Oolite is confined beneath Kimmeridge, Ampthill and Oxford clay, so the clay has to be drilled through before the aquifer is reached and viability is site by site.
What that means for a borehole in the north and centre of the county:
- Limestone at or near outcrop around Buckingham, Stowe, Tingewick and Maids Moreton (MK18) is the most straightforward target in north Buckinghamshire.
- The Oxford, West Walton, Ampthill and Kimmeridge clays act together to confine the water in the Great Oolite beneath, so at Waddesdon, Quainton, Winslow, Mursley, Soulbury and Akeley the drill goes through clay first.
- Portland and Purbeck outliers at Aylesbury, Haddenham, Long Crendon, Dinton, Cuddington, Whitchurch, Stone and Brill can give a modest domestic supply where a real thickness of limestone is proven, and nothing where it is not.
- Glacial sand and gravel lenses across the north yield only small quantities and are affected by seasonal changes in water level, so they are not a target on their own.
- The Northampton Sand and Horsehay Sand formations are in hydraulic continuity in the far north and together form a good aquifer with water of good quality, but they sit deep and need a desk study before any depth is discussed.
What happens on site, from survey to commissioning
A borehole is a programme of work, not a single day with a rig. Borehole Service Utilities Ltd begins with a desk study of the published geology and any nearby borehole records, then a site visit to fix a position that has vehicle access, sensible distance from drains, tanks and boundaries, and a practical route for the pipe and cable back to the building. Drilling itself is usually a matter of days on a domestic borehole, with deeper or larger-diameter work taking longer. The whole programme runs over weeks, because testing, laboratory analysis and the pump and treatment work all follow.
On the drilling days the rig needs a working area, water and somewhere for cuttings. Chalk and limestone drilling brings up rock flour and water, and that has to be managed on site rather than allowed to run across a garden or a paddock. The upper section of the hole is cased and the annulus grouted so the borehole is sealed against surface water running down the outside of the casing, and screen or an open hole is set against the water-bearing section, depending on whether the rock stands up on its own.
After drilling comes the part that decides everything else. The borehole is developed to clear fines from the fissures, then test pumped, usually as a step test followed by a constant rate test, to measure yield and drawdown. Water samples go to a laboratory. Only then is the pump sized, set at the right depth and wired with its controls, with a storage tank where demand is peaky. Treatment is fitted to the analysis, the system is commissioned and flushed, and the borehole record and pumping data are handed over.
The normal sequence for a Buckinghamshire water borehole:
- Desk study of the geology, nearby records and expected depth.
- Site survey, siting of the borehole and access planning.
- Notifications and any permissions that apply to the site.
- Drilling, casing and grouting, with screen or open hole against the aquifer.
- Development and test pumping to establish yield and drawdown.
- Water sampling and laboratory analysis.
- Submersible pump, rising main, cabling, controls and storage, or a solar-powered pump where mains power is a long way off.
- Filtration and disinfection sized from the analysis, then commissioning and handover of the borehole record.
Filtration, treatment and looking after the borehole
Buckinghamshire borehole water is hard. The BGS memoir for the Beaconsfield district records carbonate hardness of 170 to 250 mg/l as calcium carbonate in the unconfined Chalk, rising to over 250 mg/l in the east and in the confined aquifer, with total dissolved solids generally 250 to 400 mg/l. Chloride is usually under 30 mg/l at outcrop and reaches over 50 mg/l where the Chalk is confined; sulphate is usually under 50 mg/l at outcrop and reaches 100 mg/l where confined. Limescale reduction and pH balancing are the routine ask, and they matter most in the south-east corner.
Two other things follow from the chalk itself. Nitrate at outcrop is generally 30 to 40 mg/l, which is high enough under arable land that nitrate testing is worth doing, while nitrate is minimal in the confined aquifer. And because the Chalk is fissured rather than porous alone, turbidity and bacteriological spikes can follow heavy rain, so sediment filtration and UV disinfection are the normal fit-out on a drinking supply here. Water taken from weathered London Clay itself, as opposed to the Chalk beneath it, is poor quality, and groundwater in the sandy Lambeth Group is frequently high in sulphate, calcium and magnesium.
An existing borehole needs looking after, and most of the calls Borehole Service Utilities Ltd takes about older boreholes are about falling yield, a pump that trips or a change in the taste or appearance of the water. Those have different causes: a worn or wrongly set pump, a screen or fissure network clogged with iron bacteria or fines, a dropping water table in a dry summer, or a fault in the treatment train. A downhole CCTV survey shows the condition of the casing and screen before anyone starts guessing, and rehabilitation is often cheaper than a new hole.
Treatment and maintenance work carried out on Buckinghamshire supplies:
- Sediment and cartridge filtration for turbidity after heavy rain.
- UV disinfection on drinking supplies.
- Limescale reduction and softening for hard chalk and limestone water.
- pH balancing where the analysis calls for it.
- Iron and manganese removal where testing shows it is needed.
- Pump servicing, replacement and correct setting depth.
- Downhole CCTV inspection and borehole rehabilitation.
- Yield testing and fault finding on supplies that have dropped off.
Irrigation boreholes and off grid water supply
An irrigation borehole supplies water for gardens, sports pitches, golf courses, nurseries and farm crops without drawing on the mains. Buckinghamshire has a genuine concentration of parkland and downland golf, with The Buckinghamshire Golf Club and Denham Golf Club both in Denham parish (UB9), Beaconsfield Golf Club at Seer Green (HP9) and Ellesborough Golf Club at Butlers Cross (HP17) on chalk downland, alongside large private grounds along the Thames at Marlow (SL7) and Bourne End (SL8), and working farms and nurseries in the Colne valley around Iver (SL0).
Irrigation changes the arithmetic in two ways. Volumes are far larger than household use, so the 20 cubic metres a day abstraction threshold becomes a real question rather than a formality, and the water does not have to be of drinking quality. That opens up the river terrace gravels, which BGS records as highly permeable when saturated, with yields sustained by induced river flow where they are developed close to a watercourse. They are also vulnerable to surface pollution, so they should be treated as an irrigation source rather than a drinking-water source unless testing proves otherwise.
Off grid supply is the other side of the same problem: water where there is no practical mains connection and often no convenient mains power either. Borehole Service Utilities Ltd installs solar-powered down-hole borehole pumps with their own controllers and storage, sized on the daily volume the property or the land needs rather than on peak flow, so the tank fills through the day and the demand is met from the tank. It suits remote cottages, farm buildings, field troughs and holdings on the Chiltern plateau and out across the Vale.
Soakaway boreholes for surface water on Buckinghamshire clay
A soakaway borehole disposes of surface water by carrying it down through ground that will not take it at shallow depth into a formation that will. It is the answer where a conventional shallow soakaway fails its percolation test, which in Buckinghamshire happens most often on the clay floor of the Vale of Aylesbury, where the Kimmeridge, Ampthill and Oxford clays and the Gault sit at surface, and on the Clay-with-flints capping the Chiltern plateau, where the ground drains poorly even though the Chalk beneath it is one of the best aquifers in the country.
The work is a drilling job, not a digging job. The hole is drilled through the low-permeability layer, cased through it, and finished so that water is delivered to the receiving formation rather than left to sit in the clay. Depth depends entirely on how thick the cover is at that point, which is why the same desk study used for a water supply borehole comes first. On sites in the south-east of the county, where London Clay and the Lambeth Group are thick, a soakaway borehole may be a deep piece of work or may not be viable at all.
Permissions matter here. Discharging surface water to ground can require an environmental permit or an exemption, so the position should be confirmed with the Environment Agency before work starts, and nothing should be put down a soakaway borehole that would carry pollution to groundwater. Deep soakaway boreholes are also caught by the Water Resources Act 1991 notification duty that applies to any drilling of 15 metres or more, so the drilling is notified before it starts and the record is deposited with the British Geological Survey afterwards.
Do you need a licence to drill a borehole in Buckinghamshire?
Most private water boreholes do not need an abstraction licence, because the threshold is 20 cubic metres a day. GOV.UK states that a full abstraction licence is needed for most types of water abstraction over 20 cubic metres a day, with a transfer licence for moving over 20 cubic metres a day from one source to another without intervening use, and a temporary licence for abstracting more than 20 cubic metres a day over a period of less than 28 days. The Environment Agency's own WR32 guidance confirms that at 20 cubic metres a day or less no abstraction licence is required.
There is a second permission that people miss. If you want to abstract groundwater you must check whether you need consent to investigate a groundwater source before you apply for a licence. It covers constructing a well, borehole or other work from which groundwater will be abstracted, and it also bites when machinery is installed or modified so that it takes additional groundwater, which includes fitting a larger pump to an existing borehole. It is applied for on form WR32, and the same guidance confirms that at or below 20 cubic metres a day it is not needed.
Two more duties apply whoever drills the hole. The Water Resources Act 1991 requires notification of any drilling operation of 15 metres or more in depth before drilling commences, and deposit of the resulting data with the British Geological Survey on completion, with section 198 requiring a journal of the programme of work including water levels and flow rates. Separately, if you own a private water supply you must register it with Buckinghamshire Council, which may then carry out a risk assessment depending on the type of supply, the number of people served and the volume.
The permissions checklist for a Buckinghamshire borehole:
- Abstraction licence from the Environment Agency for most abstraction over 20 cubic metres a day.
- Consent to investigate a groundwater source, on form WR32, before applying for a licence, and also when a larger pump will take additional groundwater.
- Notification to the British Geological Survey of any drilling 15 metres or more deep, before drilling starts, with the data deposited on completion.
- A journal of the programme of work, including water levels and flow rates, under section 198 of the Water Resources Act 1991.
- Registration of the private water supply with Buckinghamshire Council, which publishes its own charges for risk assessments, sampling and monitoring and can change them.
- A risk assessment by the council where one applies. A single domestic dwelling does not need one but may request one, and regulation 6 of the Private Water Supplies (England) Regulations 2016 requires the authority to review each risk assessment every five years.
Borehole drilling by town and postcode in Buckinghamshire
These are the 23 main towns and postcode districts Borehole Service Utilities Ltd covers in Buckinghamshire. The surrounding villages and outlying farms in each of these districts are covered too, so it is worth ringing even if your own village is not named here.
- Aylesbury – HP19, HP20, HP21
- High Wycombe – HP11, HP12, HP13
- Amersham – HP6, HP7
- Chesham – HP5
- Beaconsfield – HP9
- Marlow – SL7
- Buckingham – MK18
- Princes Risborough – HP27
- Wendover – HP22
- Great Missenden – HP16
- Gerrards Cross – SL9
- Chalfont St Giles – HP8
- Haddenham – HP17
- Waddesdon – HP18
- Winslow – MK18
- Stokenchurch – HP14
- Denham – UB9
- Iver – SL0
- Burnham – SL1, SL2
- Wing – LU7
- Long Crendon – HP18
- Brill – HP18
- Bourne End and Wooburn – SL8, HP10
Borehole Questions from Buckinghamshire Property Owners
Talk to Borehole Service Utilities Ltd about your Buckinghamshire site
If you are thinking about a water borehole, an irrigation supply, a soakaway borehole or an off grid solar pumping system anywhere in Buckinghamshire, ring Borehole Service Utilities Ltd on 01428 735013 and describe the site. Mobiles are 07970 573840 and 07517 151270, and the email address is info@boreholeservice.co.uk. Tell us the address, what the water is for and roughly how much you need a day, and the first step is a desk study of the geology under that particular plot. Company registration 11910668, VAT 320043076.