Technical

The objective of the site investigation is to gather information to determine the properties of the soil or rock formation and interpret how it will impact on a proposed development.

Carrying out the appropriate site investigation can in most circumstances provide project cost savings by enabling the contractors to foresee and be forewarned of any problems they may encounter.

The first decision once you have decided to drill a borehole is, where do you drill it? The drilling site has to be chosen and physically marked on the ground. This is usually done by a professional such as a Hydrogeologists or alternatively, a Water Diviner.

The Hydrogeologist uses various geophysical methods to survey the subsurface geology. Some of the problems with using a Hydrogeologist in an urban setting to probe beneath the surface, is limited space and all the pipelines, electrical cables, telephone cables and other structures interfere with an accurate results from the equipment used.

Water divining, also known as dowsing, is an age-old “art” and has been practiced throughout history. There are a variety of methods used like, forked sticks, copper wires, even fan belts and many other methods. There is no scientific evidence that it is any more effective than random chance.

The ultimate decision lies with the customer as to which method they choose. We will advise and guide you as the customer, however it is the customer’s choice as to which way to go. Ultra Drilling can arrange for the water surveying and will gladly give our opinion once the location has been visited.

Once the drilling target has been pegged the next task is the drilling of the borehole. Please note that the customer contracts the driller to drill the borehole to a required depth, based on the survey report – not until water is found. Ultra Drilling cannot be held responsible for the success of the borehole, the customer pays for the depth drilled at the agreed rate regardless of the amount of water or lack thereof.

Due to the geological structure and survey report, avoid the perception that you drill and suddenly there is water and that it is just depends on the depth reported. This is not always the case. There are a percentage of boreholes that are drilled to the depth reported that are “Dry”, meaning no water is found on that depth. The cost of drilling is according to the depth of the borehole and not for a successful “wet” borehole.

The drilling method used is air flush rotary percussion. A pneumatic hammer and drill bit operated at the end of the drill pipe rapidly strikes the rock while the drill pipe is slowly rotated. The shattered pieces of rock are removed from the borehole by compressed air which is used to drive the hammer. The drilling process is very noisy and very messy. The process can either be very dusty at first if it is a rocky area, or very muddy or both. Ultra Drilling however takes measures to limit the dust and control the mud that is produced during the drilling process.

In urban areas we only drill during normal working hours and it is advisable to notify your immediate neighbours to close their windows the day drilling is to commence. The drilling process time depends on the depth and underground structure.

Domestic boreholes are initially drilled through the topsoil and weathered overburden rock. This facilitates the installation of steel casing. The borehole casing effectively stabilizes that portion of the borehole sidewall, especially when sandy, which is unstable and prone to collapse. The average depth of overburden and hence casing required depends on the underground structure. Insufficient casing can result in borehole collapse with severe financial implications for the client (loss of pump, pipes and the entire borehole).

Usually, casing is only required through the unstable overburden however under severe geological circumstances may require that the borehole is cased from top to bottom. In this case perforated casing would be installed opposite the water bearing fractures. The amount of casing required is unique to each borehole and can only be deduced from the results of the drilling. Assuming that the borehole is successful the driller will perform a blow yield and ‘guestimate’ the yield of thereof.

The accurate yield of a borehole can only be determined by means of an aquifer test – pumping test. These tests involve installing a test pump and pumping the borehole for a period of time at a given rate (yield) whilst recording the drawdown (lowering of water level in the borehole as a result of abstraction). Simply put, the maximum yield of the borehole is achieved by increasing the abstraction rate to a yield which results in the maximum drawdown of water in the pumping borehole without resulting in pump suction air in a given period of time. Aquifer tests are valuable in determining optimum abstraction rates, which in turn allow for correct sizing of the pump to prevent over abstraction and pump burn out. To determine optimum pumping schedules, you need to stop pumping the borehole for the water level to rise to the initial level before testing.

An alternative and less accurate method for determining the yield of a borehole is to quantify the blow yield whilst drilling or air flushing. A blow yield usually realizes a conservative estimate, but has its limitations when small volumes of water are intersected. The reason for this being that the volume and pressure of compressed air being introduced into the borehole partially inhibits water entering the borehole.

We recommend that whilst conducting the water yield test, to take a water sample to a laboratory for quality testing. An analysis of the water drawn from the borehole will determine if the water needs to be treated in any way.

When we arrive at your property, we are going to make as little noise as possible – no shouting at each other and we do not permit our staff to play music onsite. We promise to be considerate.

We have well serviced equipment and vehicles which are in top condition and will not arrive with oil or diesel leaking.

The drill rig & compressor trucks are very big and heavy and are very difficult to manoeuvre in confined spaces and may also cause damage to lawns and paved areas. Ultra Drilling will make every effort to avoid any damage to your garden.

Our team is well-trained, dressed neatly and work safely. We ask that the space we need to work in, to be kept out of bounds for any children and pets. We work with heavy and very high-pressure equipment.

We’ll cover the area under the drill rig with a plastic liner in case of an oil leak developing during work in progress.