Information for first time borehole clients - Borehole Exploration
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Information for first time borehole clients

The first step in successful borehole construction is knowing the purpose of the water you are extracting.

You need to consider following questions:

  • How much water do you need and what will you use it for?
  • Is it needed for irrigation?
  • Is it needed for domestic supply?
  • Stock watering?

If you need water for toilet flushing and sanitation, for example, a low-yielding borehole with saline water will be sufficient. But it will be of no use if you require high-quality water for crop irrigation.

​It is the customer’s responsibility to consult with a Ground Water Specialist to decide if and where a borehole must be drilled.

Important information about drilling a borehole:

Difference between Wellpoints and Boreholes.

Wellpoints are shallow boreholes that are effective only where the water is not too deep under the ground surface. (The water must not be deeper than 11 meters.)
Well points are much faster and easier to install and for this reason also the cheapest option to access groundwater.

Generally speaking, wellpoint water volumes are smaller than that of boreholes and the water quality could be lower. However, this can be rectified by combining multiple wellpoint and water purification equipment. A wellpoint work with an electrical water pump on the ground surface that sucks water out of the ground.

Bore Holes are required if the ground-water level is deeper than 11 meters or the ground is too hard and rocky for wellpoint construction.
The depth and cost of a borehole differ greatly in different locations. Boreholes work with a submersible electrical water pump that is lowered to the bottom of the borehole that pushes the water out from the bottom of the hole. This allows boreholes to be much deeper and also more versatile than a well point.

Advantages of a borehole compared to well points

  • Bigger water volumes
  • Better water quality
  • Less likely to run dry due to overuse or drought in the area.
  • Much less likely to be contaminated especially if the water is for household use and drinking.

How do you know where to drill for water?

Choosing a suitable place for a borehole is a highly specialised undertaking that requires specialised knowledge and years of experience by ground water specialists.

Even the best hydro-geologists and water diviners out there will be first to admit that it is not an exact science. It takes a combination of knowledge, luck, experience, instinct and hard work to find the most suitable spot and choice of borehole type.

This is a decision I leave to the experts. Before you commission me to install a borehole, I recommend that you approach a reputable company to recommend a suitable drilling spot.

Their knowledge of ground formations and water availability is crucial information required for the planning and installation of a successful borehole.

Understanding Pricing

What will it cost?

In the most ideal conditions where the ground is soft enough to drill a hole with the water-jet method and the groundwater is not deeper than 9 meters, the most basic borehole and pump set up will cost about R7500.

​A standard borehole with a submersible pump normally cost from about R30.000 to R100 000 and more. But because conditions have so many variables it is impossible to quote without a proper site inspection.

Why do I know someone who paid only a third of what I have been quoted for mine?

This is a valid question. And the answer is: “It depends on the circumstances.” That’s not being evasive. It’s a sign of just how the geology of South Africa varies, ranging from the sedimentary rocks of the Karoo basin to the metamorphosed rocks of the Northern Cape, to the granite intrusions of the Cape Granite Suite.

In addition, SA’s groundwater produces varying yields and quality.Therefore, it’s to be expected that boreholes will differ in depth, in their construction, and in how they are drilled.

Here are the main cost contributors:

Depth is invariably the main determining factor when it comes to cost. Most drill quotes are based on metres to be drilled. So whether you are drilling 10m, 100m or 300m will have a significant bearing on the price.The drill depth will depend on the depth of the aquifer you are targeting. So a good knowledge of the area’s hydrogeology is essential. A sure way to waste money is to drill on and on without knowing exactly what you are targeting. Different drilling methods are required for different formations, and this will affect the cost. In some settings, it’s possible to case off the top 6m of unconsolidated material. That is, using a pipe to protect the open hole – and then drill down using air percussion.

Air percussion is where the drill hammer breaks the rock, and the chips are blown up out of the borehole using compressed air. In alluvial aquifers, mud rotary drilling uses a drilling mud to keep the sand from collapsing and a rotating bit to bore through the sand.

Water Costs: The construction of a borehole contributes requires large volumes of water adding to the borehole drilling cost.

Drilling Method: Where there is deep weathering, or changes in formation competency, or lots of clays, Odex/SYMMETRIX drilling is necessary. This method involves pulling down borehole casing during the drilling process. This keeps the borehole from collapsing, and can also enable you to drill through hard formations.

Borehole Construction is a large contributor to cost. It is very important that a borehole is constructed appropriately. With an alluvial aquifer, you will need to choose your gravel pack and slot size correctly to avoid it silting up, while in a competent rock formation you will need to decide carefully whether there is a risk of borehole collapse.

‘Competent’ is relatively brittle, solid strata that deform by faulting, fracturing or folding, rather than flowing under stress, and are more likely to collapse, as noted.

‘Incompetent’ beds deform more readily under stress. As you can imagine, a 100m-deep borehole with just 6m of steel casing at the top will cost far less than a borehole that is fully encased; and steel casing will cost more than PVC.

If the driller needs to bring their drill rig some distance to get to you, the establishment cost may be higher.

Site access can also sometimes pose a problem, further complicating pricing the process.

 Some tips to help you understand drilling quotes

• Make sure you understand the items listed. If something isn’t clear – ask for advice.
• Seek out people in the area who have had boreholes drilled. What they tell you can be very valuable in determining borehole depth and cost.
• If you feel a quote is too high, get another one from a different company. Just make sure you’re comparing apples with apples. Check the quoted drill depth, the drill method, and the borehole construction to ensure the quotes are for the same things.

Finally, remember the cheapest option is not always the best option. You get what you pay for, and you want your borehole to last. Make sure you design, drill and construct it so that it does just that, even if it costs a bit more.

Considerations when constructing a borehole

A borehole is an costly investment. Good construction is therefore crucial. Here are some helpful tips from earth science and groundwater consultants.

The first step in successful borehole construction is knowing what you want.

How much water do you need and what will you use it for? Irrigation? Domestic supply? Stock watering? This will affect the water quality required.

If you need water for toilet flushing and sanitation, for example, a low-yielding borehole with saline water will be sufficient. But it will be of no use if you require high-quality water for crop irrigation.

GET IN TOUCH

The Process

Do your homework

Check with neighbors to see who has a borehole. If they do, what is the quality like and what is the yield? This will give you an idea of your chances of finding water. Also, consult a geologist or hydrogeologist (groundwater specialist) with experience in the region where you require water. He will be able to tell you immediately before any detailed assessment is done if you’re likely to get a high-yielding borehole of 5l/s or more, or a low-yielding borehole (less than 1l/s).
After this, he can assess the surrounding geology and subsurface conditions to see if the site is underlain by poor-yielding aquitards and aquicludes (rocks that retard water flow, usually forming barriers or seals above aquifers).

Understand the risk

While the driller should exercise care and diligence, he is not responsible for the water quantity or quality.

Groundwater assessment

This is a phased assessment, starting with a desktop study and followed by a field visit and borehole siting. The assessment should be divided into phases, each with its own costs so that you don’t have to pay a large amount of money upfront. The desktop assessment, for example, may indicate little chance of good quality, high-yielding groundwater (despite your neighbour’s experience). If it’s positive, you can proceed with the actual siting and drilling.

Be aware of costs

There could be additional costs for drilling through certain rock. The contractor might have to set up a base camp where staff are fed and housed. If a local community is involved, you will have to factor in visits and meetings. The driller should be able to provide a bill of quantities – that is, the cost per unit of drilling a certain diameter at a certain depth. Instead of a bill of quantities, though, many farmers might favor a lump sum instead, with a single price per borehole. A lump-sum contract may prevent over-drilling, but it can also encourage under-drilling, with boreholes not being drilled to the required depth.

Supervision

This should include witnessing and certifying critical milestones, as well as ensuring that boreholes are drilled and completed to specification. Supervision of drilling by a geologist/hydrogeologist can ensure that the correct data (depth, yield and quality of water strikes) is collected during drilling. This will assist in any future pumping tests or licensing requirements.

Site meetings

These meetings review the progress and quality of the work. At the meeting, the contractor should submit a progress report and detail any new challenges. Not all issues can be resolved on site and a consultant may have to be called in.

Payment structure

This should be based on actual work completed. When and how much must be stipulated in the pre-agreed contract.

Completion time

By the completion date, the contractor should have finished all the work, removed the material and returned the site to the pre-existing condition as much as possible.

Insurance

Insurance for damage should be taken out with a reputable company by the contractor.

Borehole completion

When drilling is finished, fit a lockable cap to protect the borehole from vandalism, such as people throwing stones down it. With an artesian borehole (where groundwater flows out under its own pressure) you will need a sealed wellhead. It is recommended that a borehole has a form of physical identification.

Handover

These tests, along with subsequent analysis by hydrogeologists, can determine the safe, sustainable rate at which a borehole should be pumped, as well as what depth to install the pumping equipment. They will also help to ensure that the borehole does not dry up over time.

Pumping tests

These tests, along with subsequent analysis by hydrogeologists, can determine the safe, sustainable rate at which a borehole should be pumped, as well as what depth to install the pumping equipment. They will also help to ensure that the borehole does not dry up over time.

Solar powered boreholes

Solar-powered pumps are an energy-efficient, environmentally friendly way to pump water for a variety of domestic and commercial purposes, including agricultural and residential irrigation and cattle or livestock watering. Solar pumps are easy to install and require virtually no maintenance, and they can have a lifespan of roughly 20 years, so after the initial set up costs their servicing requirements are virtually nil.

Wind powered electrical borehole pumps

Probably the most environmentally friendly way to access your groundwater is to install a wind-powered electrical borehole pump. These are most suitable for domestic water in remote locations.