Water Safety Plan
Guide
Groundwater Abstraction –
Bores and Wells
Version 1, Ref P1.3
January 2014
Citation: Ministry of Health. 2014. Water Safety Plan Guide:
Groundwater Abstraction – Bores and Wells, Version 1, ref p1.3.
Wellington: Ministry of Health.
Published in January 2014 by
Ministry of Health
PO Box 5013, Wellington, New Zealand
ISBN: 978-0-478-42708-0 (print)
ISBN: 978-0-478-42709-7 (online)
Previously published in 2001 as Public Health Risk Management
Plan Guide: Groundwater Abstraction – Bores and Wells, Version 1,
ref p1.3. This publication’s title and any reference within the text to
‘public health risk management plan’ was changed in January 2014
to reflect the December 2013 legislation change of the term ‘public
health risk management plan’ to ‘water safety plan’. No other
changes have been made to this document.
This document is available at: www.health.govt.nz
This work is licensed under the Creative Commons Attribution 4.0 International
licence. In essence, you are free to: share ie, copy and redistribute the material in any medium or
format; adapt ie, remix, transform and build upon the material. You must give appropriate credit,
provide a link to the licence and indicate if changes were made.
Contents
Introduction
1
Risk Summary
3
Risk Information Table
4
Contingency Plans
10
Water Safety Plan Performance Assessment
12
Ref P1.3
Version 1, January 2014
iii
Water Safety Plan Guide:
Groundwater Abstraction – Bores and Wells
Introduction
Source water abstraction is the process of taking water from the source for transmission to
the treatment plant or pre-treatment storage. This Guide is concerned with the abstraction of
groundwater from bores or wells.
If an event occurs during abstraction (ie, the quantity or quality of water is affected during
the abstraction process), the following could happen:

If there is not enough source water available to meet demand, sickness can be caused
by poor hygiene and by low pressure enabling germs and chemicals to get into the
distribution system

If there is contamination of the bore or well during construction, germs and chemicals
can cause sickness

If contamination gets into the bore or well from shallower depths, germs and chemicals
can cause sickness

If contamination gets into the bore or well from the surface, germs and chemicals can
cause sickness

If contamination gets into the aquifer, germs and chemicals can cause sickness

If a problem with the bore/wellhead does not allow enough water to be drawn from the
aquifer, sickness can be caused by poor hygiene and by low pressure letting germs and
chemicals get into the distribution system.
Activities during the operation and construction of bores may present risks to the health of
staff. These are acknowledged, but are not discussed further as such risks are the subject of
health and safety in employment legislation.
When constructing a bore or well you need to be aware of the requirements of:

the Resource Management Act

specific requirements of local authorities and regional councils

the New Zealand Drilling Standard

the information on well head construction given in Chapter 3.4 of Guidelines for
Drinking-Water Quality Management for New Zealand Ministry of Health 1995.
Drawing water from the source, and the risks associated with it, cannot be viewed in isolation;
the process influences, and is influenced by, other water supply elements:

Land use and activities carried out in the area where water enters the aquifer may affect
the quality of the water being abstracted (see Guide S1.1)

The quality of the groundwater will influence the treatment it requires (see P5, P6, P7,
and P8 series of Guides).
Several factors influence the likelihood of groundwater contamination:

how close local pollution sources are:
–
septic tanks or other waste disposal systems
–
chemical or fertiliser stores
Ref P1.3
Version 1, January 2014
Water Safety Plan Guide:
Groundwater Abstraction – Bores and Wells
1
–
–
refuse dumps
underground fuel tanks

how easily the groundwater can be contaminated (influenced by, for example):
–
water table
–
abstraction depth
–
confining layers
–
hydraulic conductivity
–
soil characteristics
–
rainfall
–
use of irrigation

contamination of the aquifer due to:
–
back-siphoning
–
a poor seal between the casing and the ground
–
cracks in the wellhead or casing.
The risk to groundwater quality therefore depends on the quality of the water in the aquifer
and the design, construction and operation of the bore or well.
2
Water Safety Plan Guide:
Groundwater Abstraction – Bores and Wells
Ref P1.3
Version 1, January 2014
Risk Summary
The events creating the two greatest risks involved in abstracting water from the source are
not being able to draw enough water (see P1.3.1), and contaminated water getting into the
aquifer or the bore/well (see P1.3.3–5).
The most important preventive measures are:

take steps to conserve water when a water shortage looks likely (see P1.3.1.1)

draw water from a secure aquifer if possible (one in which the water quality is not
affected by water from the surface) (see P1.3.5.2)

construct the bore/well head so that contamination cannot get in (see P1.3.4.1)

install a device on the bore pump to stop backflow into the aquifer (see P1.3.4.5)

restrict activities in the aquifer recharge zone that might contaminate the water (see
P1.3.5.1).
(References in parentheses are to the Risk Information Table.)
Ref P1.3
Version 1, January 2014
Water Safety Plan Guide:
Groundwater Abstraction – Bores and Wells
3
Risk Information Table
Reliable information about water quality is essential for the proper management of a water
supply. Knowledgeable and skilled staff are also essential for minimising the public health
risks associated with water supplies. Please read the staff training (Guide G1) and the
monitoring guides (Guide G2). While we haven’t pointed out every detail of how these
documents are linked with the present document, the links are many and are important.
Abbreviations: DWSNZ – Drinking-Water Standards for New Zealand; MAV – Maximum acceptable value – see
DWSNZ; NZDS – New Zealand Drilling Standard.
Causes
Preventive measures
Checking preventive measures
Corrective action
Signs that action
is needed
What to check
Event: NOT ENOUGH SOURCE WATER AVAILABLE FOR ABSTRACTION
Hazards: Germs and chemicals that get into the water because of low system pressure; hazards associated
with poor hygiene.
Level of risk: High

P1.3.1.1
Drought.


P1.3.1.2
Resource
consent
limitations.
Start water conservation 
measures as soon as

water shortage
becomes likely.

Plan the development
and use of the water
source, and the need to
identify and develop
new sources, based on
the safe yield of the
bore/well.
Water demand.

Source usage
rate.
Drop in system
pressure.

Customer
complaints
about low
pressure.
Negotiate new resource 
consents and sink more

bores/wells.
Water demand.

Source usage
rate.


System
pressure.
System
pressure.

Prepare new
resource
consent
application.

Find new
sources.

Increase
storage
capacity.

Partially close
valves through
the network to
equalise
pressures.
Drop in system
pressure.

Find new
sources.
Customer
complaints
about low
pressure.

Increase
storage
capacity.
Event: CONTAMINATION OF BORE/WELL DURING CONSTRUCTION
Possible hazards: Germs and chemical determinands (eg, barium).
Level of risk: Low
P1.3.2.1
Crosscontamination
by drilling
equipment.
4

Ensure that drills are
cleaned and disinfected
before drilling starts.

Follow requirements of
the NZDS.
Water Safety Plan Guide:
Groundwater Abstraction – Bores and Wells


Development of
nuisance
organisms such
as iron bacteria.

Disinfect
bore/well.

Flush bore/
well.
Evidence of
NZDS not having
been followed.

Use a
different
contractor.
Ref P1.3
Version 1, January 2014
Causes
Preventive measures
Checking preventive measures
Corrective action
Signs that action
is needed
What to check
Event: CONTAMINATION OF BORE/WELL DURING CONSTRUCTION cont’d
P1.3.2.2

Residual
substances

used in drilling
releasing health
significant
determinands
(eg, barium
from baryte).
Follow requirements of
the NZDS.

Ensure the bore is well
flushed before being put
into use.
Healthsignificant
determinands
used in drilling.

Concentrations
of chemical
determinands
more than 50%
of their MAV.

Evidence of
NZDS not
having been
followed.

Flushing not
undertaken.

Flush well/bore
until chemical
determinand
concentrations
less than 50%
of their MAVs.
Event: CONTAMINATED WATER GETTING INTO THE BORE/WELL FROM SHALLOWER DEPTHS
Possible hazards: Germs and chemical determinands (eg, manganese, nitrate).
Level of risk: High
P1.3.3.1

Poor joints,
cracks or
corrosion, in the
bore casing.

P1.3.3.2
Drawdown
bringing
contaminants
from shallower
regions of the
aquifer.

Select appropriate
casing material from
knowledge of the water
chemistry.

Microbiological
quality.

High E. coli
counts.

Chemical
determinands
possible at
shallower
depths (eg,
nitrate,
manganese).

Evidence of
NZDS not
having been
followed.

Inappropriate
casing material
selected.

No system for
backflow
prevention.
Microbiological
quality.

High E. coli
counts.
Chemical
determinands
possible at
shallower
depths (eg,
nitrate,
manganese).

Evidence of
NZDS not
having been
followed.

Inappropriate
casing material
selected.

No system for
backflow
prevention.
Ensure bore
construction follows the
NZDS.
Carry out initial aquifer 
tests to determine a rate
at which water can be

abstracted without
excessive drawdown.
Ref P1.3
Version 1, January 2014

Withdraw
casing and
replace or
repair.

Implement
conservation
measures and
reduce pumping
rate.
Water Safety Plan Guide:
Groundwater Abstraction – Bores and Wells
5
Causes
Preventive measures
Checking preventive measures
Corrective action
Signs that action
is needed
What to check
Event: CONTAMINATED WATER GETTING INTO THE BORE/WELL FROM THE SURFACE
Possible hazards: Germs and chemical determinands appropriate to contamination sources.
Level of risk: High

P1.3.4.1
Inappropriate
bore/well head
design, or poor
construction.
Ensure bore
construction follows the
NZDS with particular
emphasis on the
following:
–
–
–
P1.3.4.2

Chemical
determinands
possible at
shallower
depths (eg,
nitrate,
manganese).

Microbiological
quality.

Chemical
determinands
possible at
shallower
depths (eg,
nitrate,
manganese).

Inspection of

bore/well head
shows noncompliance with
NZDS.
Make
necessary
changes to
bore/well head
to meet NZDS
requirements.

Inspection of

bore/well head
shows non
compliance with
NZDS.
Repair bore/
well head.
air vent openings are
screened, facing
downwards and are
0.5 m above
100 year flood level
bore/well head is
surrounded by a
cement apron (at
least 2 m in
diameter) sloping
away from the head.
Ensure well tops are
properly sealed.

Ensure pumps are
sealed or situated so
that wastewater cannot
re-enter the well.

Provide protection for
the bore/well head
against stock and
human damage.

Carry out regular visual
checks for damage.
P1.3.4.3

Contamination
sources (eg,
stock) too close
to the bore/well
head.
Identify potential
sources of
contamination when
well is being sited (see
Guide S1.1).

Ensure that changes in
land use (including
urban developments),
and the potential for
contamination they
create, are well
monitored after
construction of the bore/
well.

Provide a fence around
the bore/well head to
keep stock at a suitable
distance (at least 10 m).
6
Microbiological
quality.
the cement sanitary
seal is watertight or
is raised 0.5 m above
100-year flood level,
and extends at least
3 m down the casing

Bore/well head
or casing
damaged.

Water Safety Plan Guide:
Groundwater Abstraction – Bores and Wells

Remove casing
and replace or
repair.
Construct
fence.
Ref P1.3
Version 1, January 2014
Causes
Preventive measures
Checking preventive measures
Corrective action
Signs that action
is needed
What to check
Event: CONTAMINATED WATER GETTING INTO THE BORE/WELL FROM THE SURFACE cont’d
P1.3.4.4

Consider elevation of
bore/well head when
siting bore/well.

Ensure bore is
equipped with backflow
prevention.
Bore/well sited
in low ground.
P1.3.4.5
Back-siphoning.

Ensure site is
well drained to
avoid pooling of
water.
Event: CONTAMINATION OF THE AQUIFER (the source)
Possible hazards: Germs and chemical determinands appropriate to contamination sources.
Level of risk: High
P1.3.5.1
Contamination
sources (eg,
stock, septic
tanks, chemical
sources) too
close to the
bore/well head,
or bore/well too
shallow.
P1.3.5.2
Aquifer is not
secure.


Identify potential
sources of
contamination when
well is being sited (see
Guide S1.1).

Microbiological
quality.

Chemical
determinands
appropriate for
likely
contamination
source.
Ensure that changes in
land use (including
urban developments)
and the potential for
contamination they
create, are well
monitored after
construction of the bore/
well.

Restrict activities in the
aquifer recharge zone
that may contaminate
the water (see Guide
S1.1).

Gather information
about the vulnerability
of the aquifer before
undertaking
development.

Assess the security
status of the aquifer
before undertaking
development so that
treatment needs can be
identified, and the
importance of
restrictions on activities
in the recharge zone
evaluated (see
DWSNZ:2000 Section
3.2.4).
Ref P1.3
Version 1, January 2014

Isotope and
CFC
determinands,
and/or

Conductivity

Chloride

Nitrate
(See DWSNZ:2000
Section 3.2.4.)

No survey of
potential
sources of
contamination
undertaken.

No aquifer tests 
carried out.

No system for
obtaining
information
about changing
land use in
place.

Tests to
demonstrate
security do not
meet the
requirements of
DWSNZ:2000.

Changes in
turbidity and/or
colour of water
with weather
conditions.

Add treatment
processes to
remove
identified
contaminants.
Instigate system
for gathering
information
about land use
changes.

Take actions to
reduce possible
contamination
sources.

Ensure
treatment
processes are
in place to
compensate for
unsecure
source.
Water Safety Plan Guide:
Groundwater Abstraction – Bores and Wells
7
Causes
Preventive measures
Checking preventive measures
Corrective action
Signs that action
is needed
What to check
Event: TOO LITTLE WATER CAN BE DRAWN FROM THE BORE OR WELL TO MEET DEMAND
Possible hazards: Germs and chemicals that get into the water because of low system pressure; hazards
associated with poor hygiene.
Level of risk: High1

P1.3.6.1
Damage to the
pump or bore/
well head by
animals.
P1.3.6.2
Catastrophic
failure (eg,
flood, slips or
earthquakerelated
damage).
P1.3.6.3
Pump failure
(see Guide
P10).
P1.3.6.4
8


Early warning system
installed to indicate
change in flow.

Fence off bore/well
head to protect against
animal damage (stock
should be at least 10 m
away).

Provide protection

against flood damage,

and carry out
inspections after natural
disasters.


Bore/well head
inspections, regularly,
and directly after floods
etc, with follow-up
action if required for
existing protection (eg,
fences, vegetation and
soil instability).

Telemetric alarm for low
flows from the intake.

Maintenance according
to manufacturers’
recommendations.


Standby pump with
auto-switch to alternate
pumps.

Operate duty and
standby pumps using
an alternate ‘number of
days‘ cycle.

Telemetric alarm for low
flows.

Regular inspection of

cabling, power lines and
connectors.

Stand-by generator.

Alarm for power failure,
with battery back up.
Power failure.
1
Regular maintenance
and inspections of the
bore/well head and the
pump(s) (see Guide
P10).
Flow.
Flood levels.

Low or no flows. 

No inspections
or maintenance
records.

Review
maintenance
and inspection
procedures.

Consider
alternative
source.
Alarm activated.

Evaluate
existing
protection
system.

No water.

New pumps.

Alarm activated. 

No
maintenance
record.
Instigate
maintenance
programme.

No flow.

No protection
for bore/well
head.

No water.
Flows (from

bore/well head).

Inspection
records.
Telemetric
records.
Alarm to
indicate faults.
Redevelop well
area.
Reduced flow.

Consult with
power authority.

Obtain stand-by
generator.
The level of risk will probably increase the lower the flow of the water is.
Water Safety Plan Guide:
Groundwater Abstraction – Bores and Wells
Ref P1.3
Version 1, January 2014
Causes
Preventive measures
Checking preventive measures
Corrective action
Signs that action
is needed
What to check
Event: TOO LITTLE WATER CAN BE DRAWN FROM THE BORE OR WELL TO MEET DEMAND cont’d
P1.3.6.5

Vandalism/
sabotage.
P1.3.6.6
Screens
clogged.
Construct a security
fence around the bore/
well head, or place
inside a locked shed.

Install intruder alarm.

Develop a maintenance
plan to ensure debris is
regularly cleared from
the screens. The
frequency of the
clearing will depend,
amongst other things,
on the quality of the
water.
Ref P1.3
Version 1, January 2014

Aquifer tests.

Damage to the
intake.

Evidence of
attempts to gain
access to the
intake.

Reduced flow
from bore.

Clear screens.

Develop well.
Water Safety Plan Guide:
Groundwater Abstraction – Bores and Wells
9
Contingency Plans
If an event happens despite preventive and corrective actions you have taken, you may need
to consult with the Medical Officer of Health to assess how serious a problem is.
Event – Not enough water reaching the treatment plant
Indicators:
Required actions:
Responsibility:
10

Reduced, or no, flow reaching the treatment plant.

Unexpectedly high usage.

Structural failure of bore/wellhead, or pump failure.

Implement the water supplier’s emergency demand
management strategy.

Consider whether to switch to an alternative source of water
until adequate water of acceptable quality can again be
supplied, or to use storage. (Make sure that the history of any
tanker used to cart water has been investigated before it is
used and that the tanker will not contaminate the water.)

If inadequately-filtered water has entered the reticulation,
inform MOH of the transgression.

Put conservation measures in place.

Close valves at reservoirs to restrict supply if necessary.

Increase chlorine residual as an interim measure.

If appropriate, identify intake problem and rectify.

When restarting the treatment plant, consider doing this at a
slower rate.

Record cause of failure and corrective steps taken.

If shortages occur frequently because of too little water
available at the source, plan for finding and developing a new
source.

Modify water safety plan (formerly known as a public health
risk management plan, PHRMP) if necessary.
Manager designated responsible for water supplies.
Water Safety Plan Guide:
Groundwater Abstraction – Bores and Wells
Ref P1.3
Version 1, January 2014
Event – Contamination enters the aquifer or bore/well
Indicators:
Required actions:

Complaints of discoloured, tasting or smelling water coming
from taps.

Continued contamination of water supply: E coli detected or
Priority 2 chemical concentrations more than 50% of MAV.

Reports of illness in parts of the community that may be
linked to water quality.

Close intake.

Notify the MOH, and in consultation warn consumers in the
affected area not to draw water until further notice.

Identify the source of the contamination, and determine
whether it is likely to be a transient problem and whether
temporary treatment is available.

If problem is transient:
–
Drain and flush the affected part of the distribution
system, considering the need to flush with elevated
chlorine concentrations if the incident may have
involved microbiological contaminants. (Consultation
with the regional council will probably be required
with regard to disposal of the flushed water).
–
Responsibility:
Monitor an appropriate determinand in the affected
area to determine the success of the contingency
measures, and notify consumers, when the supply is
safe to use, that they will need to flush their taps until
good quality water an again be drawn.

If problem is likely to be long-lasting or permanent:
–
investigate and develop an alternative supply and/or
treatment
–
provide another source of potable water until water of
acceptable quality can again be supplied.

Record cause of system failure and steps taken to correct.

Modify water safety plan if necessary.
Manager designated responsible for the water supply.
Ref P1.3
Version 1, January 2014
Water Safety Plan Guide:
Groundwater Abstraction – Bores and Wells
11
Water Safety Plan Performance
Assessment
To make sure that your supply’s water safety plan is working properly, periodic checks are
needed. The overview document outlines what needs to be done. The following table
provides the detailed information for checking this particular supply element.
What to measure or
observe:
How often:

Flow records.

Turbidity.

State of intake.

Regular inspection of intake and records (frequency will
be site-dependent and should be based on previous
findings). The inspection should include, but not be
limited to, the following:
–
–
–
What to do with the
results:
Responsibility:
12
after natural or high risk events
chemical and microbiological analysis results
inspection reports.

Results need to be recorded to meet legislative
requirements or to allow water safety plan performance
assessment. The WINZ database is good for this.

The collected data need to be periodically reviewed to see
whether problems with this supply element are
developing. This should be done as frequently as the
manager responsible considers necessary to minimise risk
to public health arising from this supply element.

Should this review show any unusual incidents, indicate
that proper procedures are not being carried out, or
indicate that poor water quality is reaching customers,
then review the procedures managing the abstraction of
water.

Evaluate the monitoring results, and any actions taken as
the result of having to implement a contingency plan, to
see if the water safety plan needs modification – eg,
preventive measures are up-to-date; the contingency plan
steps are still adequate; and changes to the abstraction
system are recognised in the plan.
Manager designated responsible for water quality.
Water Safety Plan Guide:
Groundwater Abstraction – Bores and Wells
Ref P1.3
Version 1, January 2014