Water Safety Plan
Guide
Development of New Supplies
Version 3, Ref S2
January 2014
Citation: Ministry of Health. 2014. Water Safety Plan Guide:
Development of new supplies, version 3, ref S2. Wellington: Ministry
of Health.
Published in January 2014 by
Ministry of Health
PO Box 5013, Wellington, New Zealand
ISBN: 978-0-478-42778-3 (online)
Previously published in 2001 as Public Health Risk Management
Plan Guide: Development of new supplies, version 3, ref S2. This
publication’s title and any reference within the text to ‘public health
risk management plan’ was changed in January 2014 to reflect
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
2
Risk Information Table
3
Ref S2
Version 3, January 2014
Water Safety Plan Guide:
Development of New Supplies
iii
Introduction
New drinking-water supplies are needed to service new developments, or to meet the changed
needs of existing supplies. This Guide deals with the considerations needed at the planning
stage of new supply development to minimise risk to public health when the supply is
completed.
If the planning of a new supply is poor, the following could happen:





If there is not enough water to meet demand, low pressure in the water supply system
may allow entry of germs and chemicals and poor hygiene may cause sickness.
If the quality of the raw water is poor, changeable or deteriorates, germs and chemicals
may cause sickness.
If the treatment is inadequate, germs and chemicals may cause sickness.
If contamination gets into the water during distribution, germs or chemicals may cause
sickness.
If the supply is not properly managed, sickness may come from germs and chemicals
getting into the supply.
Once a new supply is established, you will need to make use of other Guides that dealing
with other supply elements.
Risks created by new supplies can come from:




the source, or sources, of raw water (See S1 series of Guides)
the treatment plant processes (See P1 – P8 series of Guides and Guides P9, P10 and P11)
the distribution system (See D2 series of Guides and Guides D1 and D3)
the management of the supply (monitoring and maintenance) (See Guides D2.3 and G2).
As well as the public health considerations, thought will need to be given to resource consent
procedures and economics of operation when establishing a new supply. A water safety plan
(formerly known as a Public Health Risk Management Plan, PHRMP) from this Guide could
be used as part of the “Assessment of Effects on the Environment” required by the Resource
Management Act.
Ref S2
Version 3, January 2014
Water Safety Plan Guide:
Development of New Supplies
1
Risk Summary
The event creating the greatest risk involved in the development of a new supply is selecting
a water source of poor or changeable quality that cannot be treated to produce a safe and
acceptable water (S2.2, S2.3.)
The most important preventive measure is to make sure you do enough monitoring to give
you all the information you need about source water quality. (S2.2.1.)
(References in parentheses are to the Risk Information Table.)
2
Water Safety Plan Guide:
Development of New Supplies
Ref S2
Version 3, January 2014
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:2000
Causes
Preventive measures
Checking preventive measures
What to check
Corrective action
Signs that action is
needed
Event: NOT ENOUGH WATER
Hazards: Low pressure in the water supply system may allow entry of germs and chemical determinands; hazards associated
with poor hygiene
Level of risk: High
S2.1.1
Groundwater


Source
characteristics
are unknown
Obtain data to
establish annual
variation in water
quality and
quantity.
Suggested tests
(quantity):
– Constant
discharge
– Step drawdown
– Specific
capacity
Surface water

S2.1.2



Choose source
with manageable
changes in unusual
weather events.

Ensure that a backup supply will be
available for
emergencies.
Unusual
weather
conditions
S2.1.3
Power failure
Obtain data to
establish annual
variation in water
quality and
quantity.
Suggested data
(quantity):
– river flow
– catchment
rainfall
– probabilistic
analysis to
determine
likelihood of low
flows and
supply
shortfalls given
alternative
demand
patterns

Generator for use
in situation of
power failure.
Ref S2
Version 3, January 2014

Constant
discharge aquifer
test data.

Step drawdown
aquifer test data.

Specific capacity
test summary.

5 year low flow
data.

Mean annual
rainfall in
catchment.

Results of
probabilistic
analysis.

Turbidity and
colour
measurements
after heavy
rainfall.

5 year low flow
data

Unsatisfactory
results for the
expected and
predicted long
term demand.

Sustainable
supply for
meteorological
conditions and
demands on
resource from
other users.

Back-up supply is
likely to be
frequently
required.

No back up
supply available.

Unreliable power
supply.

No generator
available.

Choose alternative or
additional source.

Consider options for
management of
demand.

Choose alternative or
additional source.

Plan to have generator
available.
Water Safety Plan Guide:
Development of New Supplies
3
Causes
Preventive measures
Checking preventive measures
What to check

Causes
Signs that action is
needed

Adequate storage.
Preventive measures
Corrective action
No storage
available, either
pre- or post
treatment.

Checking preventive measures
What to check
Include storage
facilities in design
specifications.
Corrective action
Signs that action is
needed
Event: POOR, CHANGEABLE OR DETERIORATING WATER QUALITY
Possible hazards: Germs; chemical determinands
Level of Risk: High1
S2.2.1

S2.2.2


Sampling of source
water as follows
(minimum number
of samples):
– During wet
weather
– During summer
– During winter

As determined by
assessment
through use of
water safety plan
S1.1

Sample results
not available.

Initiate appropriate
sampling.

For groundwaters,
initiate
determination of
groundwater
security.

As defined in
DWSNZ:2000.


Initiate groundwater
security determination.

See water safety
plan P1.3
Methodology
described in
DWSNZ: 2000
not followed. (If
supply is found to
be non-secure,
treatment to
ensure
microbiological
quality will be
required).

“Desk top” study of
risks, or confirmed
contamination of
aquifer or surface
water. To do this
the following have
to be done:
– identification of
source
protection area
– production of
list of healthsignificant
contaminants
detected in
source water
– production of a
an inventory of
possible
contaminants in
the protection
area.

Source water
quality data

Source protection
area not identified


Information about
activities or sites
in the source
protection area
that may lead to
contamination of
the source water.

Determinands of
health
significance
detected in the
source water at
more than 50% of
the MAV.

Contaminant
sources in the
source protection
area are
considered to be
significant.
Evaluate risks to
source water quality
by:
– determining the
source protection
area
– identifying key
contaminants
known to be in the
water
– listing
contaminants or
activities in the
area that could
affect water quality.

Reconsider the chosen
source.
Adequate water
quality data not
available
(microbiological
, chemical,
radiological).
Available water
quality data not
properly
assessed.

4
See Guide S1.1
Water Safety Plan Guide:
Development of New Supplies
Ref S2
Version 3, January 2014
Causes
Preventive measures
Checking preventive measures
What to check
S2.2.3


Inappropriate
location and
construction of
abstraction
system
For groundwaters,
location in high
ground, away (or
up-gradient) from
known sources of
pollution. Water is
abstracted from
below the water
table. See Guide
P1.3

For surface waters,
location is away
from stagnant
areas, and pretreatment storage
is considered to
dampen the effects
of weather
extremes.

See Guides P1.1,
P1.2
Corrective action
Signs that action is
needed

Well not
constructed in
accordance with
Guide P1.3.

Abstraction point
not constructed in
accordance with
Guides P1.1 and
P1.2.

Reconsider source
abstraction location.
Notes:
1 – The risk presented by this event can be changed by the treatment options chosen. The risk may be low if the
proposed treatment is satisfactory.
Causes
Preventive measures
Checking preventive measures
What to check
Corrective action
Signs that action is
needed
Event: POOR, CHANGEABLE OR DETERIORATING WATER QUALITY cont’d
S2.2.4


Future
development
and land use
changes that
may
compromise
water quality.
Investigate future
developments
listed in local
authority plan.
Alter or protect
location of source
abstraction point,
as appropriate.

Investigate land
use changes as
they occur.

(See Guide S1.1)

Developments
that may affect
water quality not
researched.

Lack of requests
for details of new
developments in
source protection
area, so that
submissions can
be lodged, as
appropriate.

No alteration to
proposed location
of source
abstraction when
future
developments are
shown to present
significant risks to
water quality.

Lack of
awareness of
land use
changes.

Planned
management
strategy of the
areas not
followed.

Obtain and analyse a
copy of the local
authority plan.

Keep track of land use
changes and evaluate
how they are likely to
affect water quality.
Event: INADEQUATE TREATMENT
Possible hazards: Germs; chemical determinands
Level of risk: High
Ref S2
Version 3, January 2014
Water Safety Plan Guide:
Development of New Supplies
5
Causes
Preventive measures
Checking preventive measures
What to check

S2.3.1

Incorrect
choice of
treatment
S2.3.2

6
Monitor chemical
and physical
parameters of
source water to
identify range of
water quality and
its variability.

Pilot studies of
treatment to
determine optimal
set-up.

Monitor chemical
and physical
parameters of
source water to
identify range of
water quality and
its variability.

Determine:
– maximum and
minimum
demand for
water
– rates of change
of water quality
– how water
quality is
affected by
season.
Incorrect
choice of
treatment
technology
Water Safety Plan Guide:
Development of New Supplies
Corrective action
Signs that action is
needed

Compliance with
DWSNZ:2000 is
unlikely to be
achieved.

Problems with
aesthetic quality

Technology
selected to treat
the water will be
unable to function
within
specifications.

Technology
selected will be
unable to treat
the source water
to the required
level (considering
future increases
in demand).

Start monitoring of
potential source water.

Start monitoring of
potential source water.
Ref S2
Version 3, January 2014
Causes
Preventive measures
Checking preventive measures
What to check
Corrective action
Signs that action is
needed
Event: WATER MAY BECOME CONTAMINATED DURING DISTRIBUTION
Possible hazards: Germs; chemical determinands
Level of risk: Moderate
S2.4.1

S2.4.2

Materials used
in distribution
system
contaminate
the water
S2.4.3


Backflow
prevention devices
at all locations
where backflow
can occur and
hazards to public
health exist.

(See water safety
plan D2.4)

Specify the use of
suitable materials
in construction of
the distribution
system

(See water safety
plan D2.1)

Distribution system
analysis designed
to limit areas of low
flow, and therefore
stagnation of the
water.
Backflow
prevention
inadequate
Dead ends in
the distribution
system

Inadequate
specifications for
backflow
prevention.

Distribution
system plans do
not meet the
requirements of
AS/NZS 3500.1:
National
plumbing and
drainage: Water
supply.

Map of intended
distribution
network is
unsatisfactory,
and/or does not
allow for future
growth.
Event: POORLY MANAGED SUPPLY
Possible hazards: Germs; chemical determinands
Level of risk: High
S2.5.1

S2.5.2


Sampling ports
not agreed with
HPOs as part of
design
specifications.

Determine
monitoring
requirements for
compliance with
DWSNZ:2000, plus
any additional
measurements.

Compliance with
the DWSNZ:2000
will not be
achieved.

Train someone to
assess results to
determine when
action is required.

Compliance with
the DWSNZ:2000
will not be
achieved.

Develop
maintenance plan
appropriate to the
supply


(See water safety
plan 2.3)
Water safety plan
contingency
plans are likely to
be used
frequently.
No assessment
of results
S2.5.4

Inadequate or no
sampling ports
No monitoring
plan
S2.5.3


Inability to take
samples from
certain
locations
No
maintenance
plan
Ref S2
Version 3, January 2014
Water Safety Plan Guide:
Development of New Supplies
7