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A borehole is a great way to
ensure that you have enough water for your farm – whether you are pursuing crop
or livestock production. Still, boreholes don’t come cheap and should be
considered a long-term investment for your farm. Thus, ensuring that you get a
good one in the first place is crucial.
Here are some tips;
To make a success of your
borehole investment, first decide how much water you need and whether it will
be for irrigation, livestock or for use in the farmhouse. This often affects the
water quality required.
For example, should not be
worried about high quality water when the water will be used for irrigation and
why invest in a borehole that produces low water quality, when you will want to
drink the water?
Research your area or neighbouring farms
Just visit the neighbouring farms
and see what kind of water they are getting from their own boreholes and see if
you like the quality of the water that they are getting and the quantities.
Then consult a geologist or
hydrogeologist with experience in the region where you farm – he/she should be
able to tell you if you will get a good borehole – even before you invest in a
detailed survey.
A detailed assessment can then
follow to verify the surrounding geology and subsurface conditions for poor-yielding
aquitards and aquicludes (rocks that retard water flow, usually forming
barriers or seals above aquifers).
Warning
While your borehole driller
should aim to get you good return for your investment, he is not responsible
for the water quantity or quality that you will get.
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 up front.
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
favour 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 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
This should be based on actual
work completed. Usually, 5% to 10% of each stage valuation sum is held back.
Half of this retention fee is released after completion of the work. The
balance is paid after the defects liability period.
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.
Defects liability period
This is usually six to 12 months
after completion and handing over of each borehole. During this period, the
contractor is obliged to correct defects at his own expense.
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/well (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. The
borehole number should be stamped into a metal plate on the pump stand or
borehole plinth, along with other information such as depth and completion
date.
Handover
Check that the driller has met
all the contract requirements, the installation is functioning properly (if
pumping equipment is installed) and all the required data has been collected
and submitted. Also, make sure that the site has been restored to the
pre-existing condition as much as possible.
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. Pumping tests are also a requirement of any groundwater use
licence application.
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