Frequently Asked Questions for Class 1 bores in proclaimed & unproclaimed areas.
KARRAGULLEN WATER DRILLING
What's the difference between drilling in the hills & drilling in the flats?
There are two main methods of drilling for water in the Perth Metro area. Drilling in the Perth basin predominantly requires mud drilling due to the formations that are targeted. Most bores west of the Darling Scarp are constructed in sand, clay &/or limestone & can even be a mixture of all three. Mud drilling is the most preferred method to tackle these three types of formations.
Drilling along the foothills can require a mixture of mud & air drilling depending on the area.
Drilling in the hills often requires air as granite is inevitable however mud drilling can still be successful in some areas, particularly in locations situated at the base of valleys where small paleo type channels can be intercepted. However to have the highest chance of success in the Perth Hills a drill rig should have the air option as a means to penetrate granite. Without this option it can be very disappointing when granite bedrock is reached without finding any water.
What's the difference between air drilling & mud drilling?
Air drilling, as the name suggests, uses highly compressed air to blow down the inside of the drills rods as they are rotating & driving deeper into the ground. The air helps remove the cuttings from the bottom of the hole & then blows them straight up between the outside of the rods & the inside of the borehole. The benefits of using air is (in the Perth Hills) mainly for the purpose of running a Down The Hole (DTH) Hammer. This tool basically acts as a rotating jack hammer which is at the bottom of the rods. It is a heavy duty steel cylinder with a heavy piston inside that hits the cutting tool at around 1800 blows per minute.
If the soil formation is soft or unstable air will continue to erode at the borehole wall creating all sorts of problems. Mud drilling overcomes these problems by being a lot gentler on the borehole wall & is therefore the preferred option in softer soils.
Mud drilling uses water with an additive to thicken it, usually a bentonite clay or a polymer. Bentonite clay is usually preferred in sand based formations & polymers are often preferred in clay based formations. Bentonite is a natural formation (being clay) while there are several types of polymers, though put simply, several polymers used in the drilling fields are also used in food production as a thickener. This 'mud' is then pumped down the inside of the drill rods while drilling & when it comes up between the outside of the drill rods & the inside of the borehole it is channeled into a mud pit or tank where the soil (cuttings) settles out of the mud & is removed to leave the mud cleaner so it can be re pumped down the rods on a continuous cycle until the hole has reached it's maximum depth.
How do I know where to drill?
Depending on where you are located in the Perth Metropolitan area this can be extremely easy or extremely difficult. It is easy in the area's that have been mapped & are specifically clear in the Perth Groundwater Atlas, while at the other end of the spectrum it can be extraordinarily difficult in other areas not mapped in this atlas. This is not to say that water is not readily available in the unmapped area's, but it comes down to investing first in a good thorough investigation of your area to see what locals & neighbours have got. Karragullen Water Drilling is quite happy to drill on targets selected by water diviners but as we are unable to provide this service we prefer the customer to source their own diviner if this is the method they prefer. The method Karragullen Water Drilling has used in the past is through a geological approach, while this method has good merit it is still being developed & is something we firmly wish to invest a lot more in. There is still a lot more data to be aquired to perfect it, however divining has had many decades of trial & error while this scientific approach has only had a few years of trial & error with only had a handful of determined landowners wishing to use it to date.
Why does it cost so much to drill a bore?
There are obvious reasons for the costs of drilling a bore, but then there are the costs that are not so obvious. To replace the rig owned by Karragullen Water Drilling it would cost about the same as buying a brand new house in suburbia. This is a cost that is unseen & as every part of the rig has a finite life, at some point in time just about every part will get replaced, meaning constant repairs & replacement. This is an ongoing cost that is the reason for the drilling industry being labelled as a very high maintenance industry.
Why do I still have to pay if the bore is dry?
The simple answer to this is that the client is paying for the drilling contractor to construct a well, they are not getting paid to produce water. The very same costs & labour are involved whether the bore is wet or dry, however if it is dry & any or all of the casing is retrieved or not required then this reduces the consumable cost to the job. This cost reduction is averaged out to give a standard dry price which is approximately 15% lower than the wet price.
How deep do I have to go?
There are different depths for different areas. Many domestic bores in the sand plains around Perth range from 25m - 35m & are clearly mapped on the groundwater atlas, while other areas are considered hit & miss. These areas that are hit & miss will usually have a thick layer of clay (often black) which is generally considered the bottom of the water table. Many Class 2 bores need to penetrate this clay layer in order to get to a lower aquifer. The ADIA website has a list of Class 2 licensed drillers if this is your requirement. However for a domestic bore if this layer of clay has been intercepted without locating a suitable amount of water beforehand, it is necessary to stop drilling & the well will be considered dry.
When it comes to drilling in the Darling Range there are a few variables to determine the required depth, however there is no guarantee that greater depth equals greater water volume. Many trials have been undertaken to determine the optimum depth for bores in granite yet there is no consistency to go by. Some bores have a moderate to small flow of water on top of the bedrock that if managed correctly can supply a consistent amount of water, however with a drying climate many of these bores have reduced their yields to the point where they are no longer being used. This is not to say there is no water above the bedrock, as there are many examples of extraordinary flows in the Perth hills from shallow bores above the granite. There is though, quite a consistent trend of water being discovered in the bedrock itself where there's been previous shallow drilling attempts that have been terminated too early.
Karragullen Water Drilling does not believe older shallow attempts were wrong, as these holes were drilled with the knowledge known at the time. It was this knowledge which pioneered the drilling industry in this region & was an invaluable service to the hills residents, especially to those without scheme water. It was these very same drilling contractors that inspired Eric to also become a driller. Since coming home from school to help run the family orchard it was always the highlight of the year when they could afford to drill a bore in the hope of finding more water to expand the fruit plantation. At that time the predominant drillers were A. Levis and Sons from Carmel. Vic Levis still runs this business with his son Ben Levis.
In the end depth is a combination of listening to the driller & making an informed decision. The fact is, the water located above granite & below it are considered as being the one & the same system & are simply regarded as the water table. There are several structures specific to localised geological formations that can create what appears to be many different water levels in a known area.
Can I drill too deep & lose all my water?
This would have to be the most recurring question ever asked in regards to water drilling in the Perth Hills. Quite simply, the answer is no. There has been several instances where people have heard of someone who knew somebody else who'd said that this can happen. The simple fact is, it does not happen & has not happened to the knowledge of Karragullen Water Drilling taking in the experience of the hundreds of bores drilled throughout the Darling Scarp for the last four decades. There is of course stories of bores drying up or of other cases where the well drilled was in a large cavity that didn't maintain the flow estimated at the time of drilling. Though these wells are quite rare, they are unfortunately, just a fact of life & are very hard to determine until pumped properly.
Is it possible to drill too shallow?
Unfortunately, yes it is possible to drill to shallow. It has been Karragullen Water Drilling's misfortune to have been advised by the client that they wish to stop as early as possible against our advice. In some of these circumstances the customer has then requested a second well to try to get a bit more water after being disappointed with the first well. In the end this has then cost the customer double the amount when a 10% extra investment on the first well may well have been the wiser decision.
Can I hit salt water?
Yes you can, but depending on the area you are in the chances will vary greatly. The water will be tested on site to give an initial level & if higher than desired the bore can be either cased to be used under proper management or backfilled & classed as dry.
What is the best way to pump a bore?
There is no 'best way' to pump a bore, but there are many recommendations that are worth considering. Over pumping where air surges out of the pipe is not good for either the pump, the underground formation or the plumbing above the ground. While restricting the bore too much can cause problems, especially if there is a lot of iron bacteria blocking the screens or if the water is a bit dirty. Starting the bore for short periods on a timer several times an hour can be the only way to manage some very low flow bores yet this is not ideal as any small clay or sand particles don't get a chance to 'clear' & can end up building up in the impellers of the pump causing bearing problems & subsequent pump failure. Every time a bore is started or stopped there is a bit of disturbance. This doesn't necessarily present as a problem unless there is a bit of a dirt or silt coming in. If this is the case then there is a constant inflow of small particles. By pumping for a longer period it allows for the water to clear up & flush out the system. Of course if the formation isn't capable of pumping for longer periods the owner needs to accept that pump maintenance will be higher than average.
What is the best way to manage the bore water?
There are basically two ways to manage the water coming out of the bore. First is to pump it into a tank & from there a second pump can be used to irrigate on a suitable design. The other option is to pump directly from the bore into the irrigation, though to do this the owner needs to be very confident of the sustainable flow.
How do I work out how much water I can pump out of the bore?
This works in a bit of a process. Firstly the driller will give an estimate of the flow at the time of drilling or developing & at what depth the main supply is located at. This will give the customer an idea about the flow rate & the depth that the water needs to be pumped from. This information can then be provided to the pump installer who will select the most suitable pump that will do the job the most efficiently. If it is to be pumped directly into irrigation the pump installer will take this into consideration. As the customer you do have the option of going bigger or smaller than the recommended pump size however it is best to listen to the advice of the installer. Once the pump is installed & ready to go a pressure gauge on the pipe is a good idea to determine the sustainable flow of water that can be pumped. The pressure gauge should be fitted by the installer on the pump side of the main valve. This gauge will start to flicker up & down if air starts to enter the water flow, if this is observed then the main valve should be closed incrementally until the pressure stabilises. If a pressure gauge is not supplied it can be put on at a later date, or you can just observe the pumps performance, if you see or hear air surging then the main valve should be restricted incrementally until a steady flow is coming out.
Does it hurt the pump if I restrict the flow?
This is another common misconception. Submersible pumps are designed for pumping water out of bores & are 100% capable of being restricted to the allowable flow. However to ensure the pump is running within its desired scope it is recommended to install a pump that is specified as close as possible to the expected flow. As many bores can vary from the initial flow test it is impossible to always get the perfect pump, this is why they are designed with variable flows & pressure capabilities in mind.
Do I need a license to drill a bore?
Yes & no, depending on your area. The simplest method to find out is to contact the Dept of Water who will determine exactly what your requirements are.
Is there any chance of hitting gold & can I strike oil or lava if I go too deep?
As exciting (or scary) as this may sound, no you will never hit oil in the Metropolitan area especially on the shallow class 1 bores & although it may be obvious to geologists in the Darling Scarp, it is also another one of those frequently asked questions. Regarding lava, the earths crust is 30-50 kilometers thick before even reaching the mantle which in itself is almost exclusively solid & no, it is impossible for Karragullen Water Drilling to even think about drilling that far as our maximum rated depth is only 200m. The third element is a little bit different, but yes, it is actually possible to hit gold in the Darling Range but of course it is extremely rare. In fact Karragullen Water Drilling has never found gold in the any of the samples taken over countless holes however we have come across fools gold which is actually quite surprising in itself.
If I find gold who owns it?
If on the extremely unlikely event of finding gold, the samples belong to you the customer & then it is incumbent upon you the landowner to investigate further as to who exactly owns the mining rights over your property.
How much space is required to drill a bore?
Karragullen Water Drilling utilises the services of two trucks. The main truck which carry's the rig is an 8 wheel drive & is equivalent to a bus, so if you think you can get a bus to the site then there's a good chance we can get the rig there. If we can get the rig there then we should also be able to get the support truck there, however the support truck can be located up to 20m away if required. There is another obstacle to overcome though & that is overhead cables, trees or infrastructure which although may not appear to be in the way can still pose a safety risk when standing up the derrick (mast).
Will there be much mess?
Unfortunately there are some bores that cannot be drilled without making a bit of a mess. This is more common in the hills region where air drilling in unstable sloppy formations can be quite challenging. It is usually overcome by changing from air to mud drilling but it can suddenly happen upon a job where we have no other choice but to continue until the hole is completed. At the end of the job it is most important that the well has been constructed properly & completed satisfactorily so as the customer is getting a proper return for their investment. Therefore it is advisable to drill away from buildings if possible when using air. As most of the unstable ground is located above the granite a pre-collar is often inserted all the way to the bedrock to stabilise the hole, thus keeping the overburden from continually eroding away.
What is Bedrock?
Bedrock is the consolidated rock underlying the soil which we drill through. In the Darling Range it is usually Granite but can also be Dolerite. In the superficial aquifers of the Perth sand plains bedrock is often not intercepted.
What is a Dolerite Dyke?
Dolerite dykes are intrusions of solid black igneous rock injected through fault lines & fractures of the granite bedrock. Granite itself (in a very simple explanation) is made up of the same basic material - molten rock - which cooled over a long period of time while forming the earths crust. This slow cooling process enabled crystals to grow, this is why granite is often referred to as crystalline rock & makes up the bulk of continental plate composition. During different geological events & countless tectonic movements, many different stresses on these plates resulted in multiple fractures, faults & fissures. Geologists can interpret these different trends, linking them to specific events in the planets history. Many of these fractures were then injected with fresh molten rock from the earths core, cooling significantly faster in the surrounding bedrock formation resulting in a much finer grained crystal composition.
(While this extremely brief summary is not meant to be interpreted as pure, it helps with the general understanding of exploring for water using a geological approach & as these events happened over millions of years they are a lot more complicated than can be explained here.)
These target areas of injected molten rock are clearly visible as they are a different colour, grain & texture to granite & are referred to as Dolerite Dykes. Being quite distinguishable they are relatively easy for a geologist to find &, from an overall point of view, are very helpful when defining substantial fault lines. It is these fault lines that become the ideal conduit for water to accumulate & travel. Historically, it has always been fault lines & fractured zones that have been highly sought after when drilling for water, however where they were previously found by chance, we now have the tools to select them with science. These geological structures involving granite & dolerite are fairly common around the world though there are localised trends & variations specific to each region. The Perth Hills region has its own specific trend which then also has particular variables within these parameters. Added to this is the presence of quartz veins which can be associated with similar geological features but can also be just part of the process of the initial creation, as quartz is usually considered to have been the last part of the molten rock to solidify, thus was able to fill small fissures. To try to understand a lot of these complex structures & features it requires a lot of specific expertise, well beyond the grasp of the 'general knowledge' explanation offered here. Karragullen Water Drilling staff are not geologists but we do have a general grasp of geology. While a lot of modern tools & equipment developed around the world can & are used in the exploration & mapping of these & other similar rock formations, it still takes local geological understanding & experience to interpret the information collected.