Diploma of Environmental Monitoring & Technology
Study module 3
Bore drilling & installation
MSS025006A
Groundwater sampling
& analysis
Completion Record
Student name
Type your name here
Available marks
20
Final mark
Marker to enter final mark
Completion date
Marker to enter date.
www.cffet.net/env
GSA Study module 2
Bore drilling & installation
INTRODUCTION
Establishment of wells and bores
Site & drilling inspection
Site examination
DRILLING & SAMPLING
2
3
4
4
6
Borehole construction
Well installation
Well development
Protecting the bore
Workplace Health & Safety
7
11
11
12
13
ASSESSMENT & SUBMISSION
14
Knowledge questions
Assessment & submission rules
References & resources
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Introduction
A quick recap of where we are up to is necessary. Let’s say we have a client who requires
the monitoring of contaminated groundwater. The location of the contaminant plume is
known already and what we need is a monitoring network in and around the plume to
monitor it and any future remediation effects.
The first step is to work out where the bore will be located. You won’t do this, that job
requires specialist knowledge from a variety of geo and engineering people. When that is
done, the next step is to install the bores, which is what this study module is about.
Consider the following image, which is a map of the groundwater monitoring bores for a
BHB Billiton Mitsubishi Alliance project;
Figure 3.1 – Example of a borehole monitoring network. It is networks such as these that you
need to understand how bores are installed. The boreholes are light blue diamonds.
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Establishment of wells and bores
This section deals with the quality of the practical installation of the bores themselves.
The Performance Criteria for this unit do not specify that you are to be competent in
installing the wells, just ensuring that the installation process is performed in accordance
with the sampling and analysis plan or other aspects of quality assurance and control.
Bore holes installed for environmental compliance monitoring or similar activities are
usually drilled and constructed by professional drilling services with a specific grade of
licence. The professional body in ‘charge’ of drillers in Australia is the Australian Drilling
Industry Association (ADIA), who work in conjunction with the NSW Office of Water (OoW)
to control and regulate the groundwater in NSW.
Currently, drillers need to gain permission (in the form of a licence) to drill into groundwater
of any type in NSW. There are six classes of driller’s licence, with Class 1 being the lowest
level, and also the class required for drilling simple environmental monitoring or piezometer
boreholes, so, the more complex the aquifer being drilled, the higher the number/class of
licence required by the driller.
The ADIA produce a variety of Codes of practice regarding drilling for environmental
monitoring. These CoP require drillers of environmental bores to ensure that their particular
drilling practice does not introduce contamination into the bore (or at least limits or
introduces a known type of contamination as to not interfere with the investigation
analyte(s) of interest).
Environmental projects can be classified as either investigation or remedial. Both of these
classifications can require a wide variety of drilling services including the obvious installation
of monitoring wells, but also the installation of a variety of probes and instrumentation, or
conduct soil investigation and testing. As mentioned, the types of aquifer being worked on
can require different types of drilling technique, all of which are specified in the licence
conditions issued by the OoW, including the following techniques;
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Auger
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auger
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jetting
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cable tool
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rotary air
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rotary mud
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down hole hammer drilling
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reverse circulation, conventional or wireline coring
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The ADIA industry standard also specifies that groundwater monitoring bores are
constructed to ensure there are no introduced contaminants during the drilling process. This
is achieved using many quality assurance and control techniques including using only the
best made PVC threaded screen and casing that has been acid washed and plastic bagged
and ensuring that the borehole is completely sealed which helps mitigate any cross
contamination.
Figure 3.2 – Example of a small drilling activity. In this case, the driller is collecting samples as
the drilling is occurring.
Site & drilling inspection
From study modules 1 & 2 we understood the project objectives and management, and we
developed a SAP to maintain quality throughout the project’s (or sampling event’s) timeline.
All of that work has been either desktop analysis or preparations in the lab or store room,
and now we are in the field with the drillers.
Site examination
When you arrive on site with the drillers, the exact location of the bore needs to determined
(if it hasn’t already been done by the senior engineers or geologists). This will typically be
performed using one of several methods;
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High accuracy GPS (for natural locations)
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Approximate navigation using maps, followed by precise survey
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Landmark navigation (if near roads and other measurable landmarks)
Note that regardless of the technique to locate the position, the location of bores is (usually)
precisely defined by a surveyor. This is especially true if the bores form part of a piezometer
network, as the bores need to height referenced against the Australian height Datum (AHD).
The location at which the bores will be installed need to be checked for accuracy against the
SAP (unless this will occur afterwards only, otherwise the location will be a compromise
between the needs of the driller and the needs of the field technician i.e. ease of continuous
access etc). This is a simple case of comparing the coordinate information from the field
with the required information from the SAP.
A note on coordinates
The coordinates of the sample point locations can be represented in many formats. Some of
these will be familiar to field technicians; others will be in GIS or surveying formats that are
very industry specific. All field staff should familiarise themselves with the spatial data
format that their organisation uses. This information is typically found from senior staff or
specialist.
Once the location of the sites is checked and approved, field staff should give a cursory
examination of the site to ensure that there are no obvious hazards.
Hazards can exist in forms that are dangerous to field staff, but also to the bore itself. This
could include situations such as the possibility of land slippage, tree fall, or nay of numerous
natural phenomena that can damage staff or plant.
Most organisations will have a specific borehole HIRAC form that must be used to ensure
compliance with the DQO and SAP.
Basically, staff should ensure that the installation of the bore be protected from any harm of
damage or contamination. We cannot possibly list the potential sources of damage and
contamination so you need to use your imagination at this point.
Drilling quality control
In the original discussions with the drilling contractor, agreements would have been made
whereby an industry ‘standard method’ for the installation of the bore would be used. As
the expertise lies with the drillers, all you need to do is check that the drillers are installing
the bore in accordance with the original contract.
Specific procedures to audit include ensuring the drill rig and equipment is clean or
otherwise ensuring that the drill technique does not introduce contamination.
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Drilling & sampling
The design and installation of permanent monitoring wells involves drilling into various
types of geologic formations that exhibit varying subsurface conditions. Designing and
installing permanent monitoring wells in these geologic environments may require several
different drilling methods and installation procedures. The selection of drilling methods and
installation procedures should be based on field data collected during a hydrogeologic site
investigation and/or a search of existing data. Each permanent monitoring well should be
designed and installed to function properly throughout the duration of the monitoring
program. When designing monitoring wells, the following should be considered:
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Short-and long-term objectives;
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Purpose of the well(s);
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Probable duration of the monitoring program;
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Contaminants likely to be monitored;
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Surface and subsurface geologic conditions;
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Properties of the aquifer(s) to be monitored;
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Well screen placement;
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General site conditions; and
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Potential site health and safety hazards.
In designing permanent monitoring wells, the most reliable, obtainable data should be
utilized. Once the data have been assembled and the well design(s) completed, a drilling
method(s) must be selected. The preferred drilling methods for installing monitoring wells
are those that temporarily case the borehole during drilling and the construction of the well,
e.g. hollow-stem augers and sonic methods. However, site conditions or project criteria may
not allow using these methods. When this occurs, alternate methods should be selected
that will achieve the project objectives. The following discussion of methods and procedures
for designing and installing monitoring wells will cover the different aspects of selecting
materials and methods, drilling boreholes, and installing monitoring devices.
Drilling methods
The following drilling methods may be used to install environmental monitoring wells or
collect samples under various subsurface conditions. In all cases the preferred methods are
those that case the hole during drilling and can include;
◗
Hollow stem auger
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Solid stem auger
◗
Rotary methods
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Borehole construction
The objectives of drilling and installing a borehole are simple enough conceptually; insert a
pipe with holes that allows representative samples of the groundwater to be collected.
Unfortunately, in practice, nature, as so often happens, tends to sabotage the ease of the
concept and make the process a lot more difficult than it needs to be, and keeping in mind
the key word of ‘representative’, the process can be a nightmare. This leads us to a
somewhat obvious and very simple point – a poorly designed and installed bore is useless!
Figure 3.3 – Generalised cross-section of an installed monitoring bore
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Size of the annular space
The borehole should be of sufficient diameter so that well construction can proceed without
major difficulties. For open boreholes, the annular space should be approximately 50 mm to
allow the uniform deposition of well materials around the screen and riser, and to allow the
passage of tremie pipes (pipes that deliver the packing slurries) and well materials without
disturbing the borehole wall too much. In our example, a 50 mm nominal diameter (nom.)
casing would require a 150 mm inside diameter (ID) borehole so that the bore has 50 mm of
space around it.
The borehole can sometimes require over-drilling which results in a ‘sump’. This need stems
from extraneous material from the wall of the drilled borehole falling down as a result of
the auger extraction. The depth of over-drill can range from half to a few meters depending
upon the risk of infill.
Another requirement for over-drilling is to allow for filter pack materials to be added to the
bottom of the borehole (if required). Typically, 150 mm of filter pack is placed to provide a
firm base for the monitoring well piping.
The pipe
The piping (which is the key part of the process) that collects the sample of water from the
groundwater system is generally ‘virgin’ Poly Vinyl Chloride (PVC) plastic, which is sort of
ironic considering PVC is considered a pollutant! The PVC must be clean of contaminants,
including colours and plasticiser materials as these could leach out of the plastic into the
groundwater thereby providing a source of contamination.
The piping is 50 mm in diameter, and consists of a variety of interchangeable parts to ensure
that the correct level of groundwater is collected. In general, the piping systems consist of
the following parts;
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Normal pipe (for getting to a depth and excluding waters)
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Slotted pipe (which allows sampled water to enter from desired aquifer)
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Coarse thread joins (these must be flush fitting)
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Rubber seals (nitrile to avoid contamination))
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Pointed bottom caps (for stability)
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Top caps or plugs(to avoid in-falling contaminants or collecting gas samples)
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Steel monument casings (for protection and security)
◗
Pre-packed versions of the above (direct push technology)
All of these parts can be assembled in a variety of ways 9i.e. with multiple screens etc) but
in general they following the design shown in the image below;
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Figure 3.4 – Example of how all the piping parts fit together to form a monitoring bore used in
groundwater assessments [source]. Note that in this case, the well is flush with the ground for
use in high traffic areas.
Filter Pack
To allow the water to enter the bore, the screened part of the pipe is surrounded by porous
material called a filter pack, which is usually sand of a known grain size to match the soil
characteristics of the immediate environment.
When placing the filter pack into the borehole, a minimum of 150 mm of the filter pack
material should be placed under the bottom of the well screen to provide a firm base. Also,
the filter pack should extend a minimum of half a meter above the top of the well screen to
allow for settling and to isolate the screened interval from the grouting material. In open
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boreholes, the filter pack should be placed by the tremie or positive displacement method.
Placing the filter pack by pouring the sand into an open drill stem is acceptable with the use
hollow stem augers, and other methods where the borehole is temporarily cased down to
the filter pack.
Filter pack plug
To make sure that unwanted waters from other aquifers or soil water does not infiltrate into
the studied aquifer, the screened section and filter pack is plugged with a sodium bentonite
clay or other forms of grout.
Bentonite pellets consist of ground, dried bentonite (which is a natural clay material)
compacted into pellets available in several sizes. Bentonite pellets are compressed to a bulk
density of 1.15 – 1.3 g/mL and hydrate to a 30% minimum solids material. Bentonite has the
interesting property of behaving like an impervious gel when wetted, and as such is
excellent at providing water seals against unwater infiltration.
Where neat cement grouts are to be used, the placement of a bentonite pellet seal above
the filter pack is mandatory to prevent the possibility of grout infiltration into the screened
interval prior to setting. Where bentonite grouts are to be used, the placement of a
bentonite pellet seal is optional, but desirable. In some cases, pellets are placed by tremie
pipe and flushed into place with potable water. A tamper can be used to ensure that the
material is being placed properly and to rapidly break up any pellet bridging that occurs.
Pellet seals should be designed for a two-foot thickness of dry pellets above the filter pack.
Grouting the Annular Space
The annular space between the casing and the borehole wall can be filled with a variety of
grout mixtures, including;
◗
either a 30% solids bentonite grout
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a neat cement grout
◗
a cement/bentonite grout
Bentonite grouts are preferred unless the application dictates the use of another material.
Bentonite grout shall be a 30% solids pure bentonite grout. Drilling muds are not acceptable
for grouting. The grout is usually placed into the borehole from the top of the bentonite seal
to within half a meter of the ground surface.
Bentonite grouts should have a minimum density of 1.2 kg/L to ensure proper gelling and
low permeability. The density of the first batch of grout should be measured while mixing to
verify proper measurement of ingredients.
Cement grouts are generally dictated where a high level of dissolved solids or a particular
dissolved constituent would prevent proper gelling of a bentonite grout.
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Neat cement grouts have a density of 1.8 kg/L. The addition of bentonite (5 to 10 percent)
to the cement grout can be used to slow the curing time and the density, although this may
not be needed in all applications.
Most field technicians involved in installing the bores will never calculate the required
densities or grout ratios as this will be calculated and determined by the senior geo staff.
Well installation
The borehole should be bored, drilled, or augured as close to vertical as possible, and
checked with a plumb bob or level. Deviation from vertical is usually with accuracies as close
as 1° per 20m of depth. The well casings should be secured to the well screen by flushjointed threads and placed into the borehole and plumbed by the use of centralizers and/or
a plumb bob and level.
Another method of placing the well screen and casings into the borehole and plumbing
them at the same time is to suspend the string of well screen and casings in the borehole by
means of a hoist on the drill rig. This wireline method is especially useful if the borehole is
deep and a long string of well screen and casings have to be set and plumbed.
Well development
The term well development refers to the need to effectively clean a newly constructed well
from all the debris and construction materials used to install it.
The main purpose of developing new monitoring wells is to remove the residual materials
remaining in the wells after installation has been completed, and to try to re-establish the
natural hydraulic flow conditions of the formations which may have been disturbed by well
construction, around the immediate vicinity of each well.
A new monitoring well should be developed until the column of water in the well is free of
visible sediment, and the pH, temperature, turbidity, and specific conductivity have
stabilized. Well development usually employs one of the following development
procedures;
◗
Bailing
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Pumping
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Surging
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Backwashing
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Jetting
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Compressed air blasting
◗
airlift pumping and air surging
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These development procedures can be used, individually or in combination, in order to
achieve the most effective well development. A newly completed monitoring well should
not be developed for at least 24 hours after the surface pad and outer protective casing are
installed. This will allow sufficient time for the well materials to cure before development
procedures are initiated, although procedures involving compressed air (or other high
energy development techniques) can require up to a week to stabilise before sampling is
allowed to occur.
Protecting the bore
In many instances of installation, the bore is protected, which simply means cementing a
steel case, called a monument, around it to protect it. The well casing, when installed and
grouted, will typically extend above the ground surface up to 70 cm.
The outer protective casing should be of steel construction with a hinged, locking cap.
Generally, outer protective casings used over 50 mm well casings are 100 mm square by 1.0
meter long.
All protective casings should have sufficient clearance around the inner well casings, so that
the outer protective casings will not come into contact with the inner well casings after
installation. The protective casings should have a weep hole to allow drainage of
accumulated rain or spilled purge water. At each site, all locks on the outer protective
casings should be keyed alike which saves valuable time for the sampler.
A concrete surface pad can sometimes be installed around each well at the same time as the
outer protective casing is being installed, although it is not common. If the monitoring wells
are located in a high traffic area, the monuments are sometimes painted to make them
more visible, and bumper guards consisting of steel pipes are sometimes installed for extra
protection against possible damage.
If the bore is in a high traffic area, the fitting of flush bolted caps (FB caps) is usually
employed as this allows traffic to run over the bores without causing damage. Another way
to protect bores is by way of signage, such as the figure below;
Figure 3.5 – Example of a warning sign to protect bores.
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Workplace Health & Safety
The Workplace Health & Safety requirements for a typical ‘indoors’ workplace also apply in
the field, so field technicians should have access to relevant documents from their
organisation prior to any drilling activities, and should be followed during all drilling
activities.
The driller or designated safety person should be responsible for the safety of the drilling
team performing the drilling activities. All personnel conducting drilling activities should be
qualified/licenced in proper drilling and safety procedures in accordance with the Australian
National Uniform Drillers Licencing Committee.
Before any drilling activity is initiated, utilities should be marked or cleared by the
appropriate state or municipal utility protection organization. In developed areas, additional
measures should be taken to locate utilities not covered by the utility protection program.
Before operating the drill rig, a pilot hole is usually dug to a depth of a meter or so to check
for undetected utilities or buried objects. The following safety requirements should be
adhered to while performing drilling activities;
◗
All personnel should wear safety hats, safety glasses, boots or other relevant PPE
◗
Drilling rig operators should know where the emergency switch(s) is located
◗
All personnel should stay clear of the drill rods or augers while in motion
◗
Rod wipers, rather than gloves, should be used to remove mud from equipment
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Do not lean or place hands against the drill rig or near moving parts of the rig
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Keep the drilling area clear of any excess debris, tools, or drilling equipment.
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Each drill rig should have a first-aid kit and a fire extinguisher
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Loose work clothes pose a risk as they might catch on some moving part of the drill rig
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Jewellery should not be worn while working around the drill rig equipment.
◗
Drillers and samplers should be mindful overhead and buried power lines
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Assessment & Submission
This section provides formative assessment of the theory. Answer all questions by typing
the answer in the boxes provided. Speak to your teacher if you are having technical
problems with this document.
Knowledge questions
◗
Type brief answers to each of the questions posed below.
◗
All answers should come from the theory found in this document only unless the
question specifies other.
◗
Marks shown next to the question should act as a guide as to the relative length or
complexity of your answer.
1. Which organisation is in charge of drilling requirements in Australia? 1mk
Click here to enter text.
Assessor feedback
2. What is the licencing system for drilling operations in NSW? 3mk
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Assessor feedback
3. Which NSW state government body looks after groundwater drilling? 1mk
Click here to enter text.
Assessor feedback
4. Identify three drilling techniques allowed in NSW. 1mk
Click here to enter text.
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Assessor feedback
5. Why is avoiding contamination during drilling so important? 2mk
Click here to enter text.
Assessor feedback
6. List the key parts of the piping system used in bore construction. 1mk
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Assessor feedback
7. What is meant by the term ‘well development’? 3mk
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Assessor feedback
8. What is bentonite, and why is it so effective? 3mk
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Assessor feedback
9. What two techniques are used to protect bores from damage or sabotage? 2mk
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Assessor feedback
10. Identify what you believe would be the three greatest hazards when performing a bore
installation. For each reason, briefly explain your choice. 3mk
Click here to enter text.
Assessor feedback
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Assessment & submission rules
◗
Attempt all questions and tasks
◗
Write answers in the text-fields provided
Submission
◗
Use the documents ‘Save As…’ function to save the document to your computer using
the file name format of;
Yourname-APM-SM1
◗
email the document back to your teacher
Penalties
◗
If this assessment task is received greater than seven (7) days after the due date, it may
not be considered for marking without justification.
Results
◗
Your submitted work will be returned to you within 3 weeks of submission by email fully
graded with feedback.
◗
You have the right to appeal your results within 3 weeks of receipt of the marked work.
Problems
If you are having study related or technical problems with this document, make sure you
contact your assessor at the earliest convenience to get the problem resolved. The contact
details can be found at;
◗
www.cffet.net/env/contacts
References & resources
Resources
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Video resource on bore installation can be found here.
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Free groundwater modelling software can be found here.
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National Centre for Groundwater Research & Training here.
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NSW office of Water drilling pages can be found here.
References
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Note that some of these resources might be available from your teacher or library
Bates, G. (2010). Environmental Law in Australia. Australia: LexisNexis-Butterworths.
Burden, F. E. (2002). Environmental Monitoring Handbook. McGraw-Hill Professional.
Corporation, B. A. (2013). Procedure for installation of ground monitoring wells. Brisbane:
Brisbane Airport Corporation.
DIPNR. (2004). Guideline for the preapration of Environmental Management Plans. Sydney:
DIPNR.
EPA, U. (2013). Design and Installation of Monitoring Wells. America: US EPA.
Grammeno, Gaby (Ed). (2009). Planning Occupational Health and Safety, 8th Ed. Melbourne:
McPherson's Printing Group.
National Uniform Drillers Licensing Committee. (2012). Minimum Construction Requirements
for Water bores in Australia. 3rd Ed. Canberra: National Water Commission.
Nielsen, D. M. (2007). The Essential Handbook of Groundwater Sampling. Boca Raton: CRC
Press.
Quevauviller, P. E. (2009). Water Quality Measurements Series: Groundwater Monitoring.
West Sussex: John Wiley & Sons.
StandardsAustralia. (2004). AS/NZS ISO 14001:2004 Environmental Management Systems:
Requirements with guidance for use. Australia: Standards Australia.
Sundaram, B. E. (2009). Groundwater Sampling and Analysis: A Field Guide. Canberra:
Commonwealth of Australia.
vanLoon, G. W. (2011). Environmental Chemistry: a global perspective. New York: Oxford
University Press.
Workplace Health and Safety Act 2011. (n.d.).
Workplace Health and Safety Regulation 2011. (n.d.).
Younger, P. (2007). Goundwater in the Environment. Carlton, Victoria, Australia: Blackwell
Publishing.
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