Water Safety Plan
Guide
Surface Water Abstraction –
Rivers, Streams and
Infiltration Galleries
Version 1, Ref P1.1
January 2014
Citation: Ministry of Health. 2014. Water Safety Plan Guide: Surface
Water Abstraction – Rivers, Streams and Infiltration Galleries,
Version 1, ref p1.1. Wellington: Ministry of Health.
Published in January 2014
by the Ministry of Health
PO Box 5013, Wellington, New Zealand
ISBN: 978-0-478-42704-2 (print)
ISBN: 978-0-478-42705-9 (online)
Previously published in 2001 as Public Health Risk Management
Plan Guide: Surface Water Abstraction – Rivers, Streams and
Infiltration Galleries, Version 1, ref p1.1. 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
13
Ref P1.1, Version 1, January 2014
Water Safety Plan Guide:
Surface Water Abstraction – Rivers, Streams and Infiltration Galleries
iii
Introduction
Source water abstraction is the process of taking water from the source to pipe to the
treatment plant or pre-treatment storage. This Guide is concerned with the abstraction of
water from flowing surface waters (rivers, streams) including the use of infiltration galleries.
If an event related to abstraction occurs (ie, the quantity or quality of water is affected by 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 letting germs and chemicals get into the
distribution system

If the water quality is so poor the treatment plant can’t treat it, germs and disinfection
by-products can cause sickness

If there is contamination of the river or stream, germs and chemicals can cause sickness

If the water quality is not improved enough by the infiltration gallery, germs and
disinfection by-products can cause sickness

If a problem with the intake, or infiltration gallery, does not allow enough water to be
drawn from the source, sickness can be caused by poor hygiene and by low pressure
letting germs and chemicals get into the distribution system.
Source water abstraction can present risks to the health and safety of the operators. These
are acknowledged, but are not discussed further as such risks are the subject of health and
safety in employment legislation.
When planning to draw water from a source you need to be aware of the requirements of:

the Resource Management Act

specific requirements of local authorities and regional councils.
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:


Which abstraction method is best for your situation will depend on the availability and
quality of the source water (see Guide S1.1):
–
impoundment may be considered if the water flow is low, intermittent, or
unlikely to meet demand under all conditions
–
an infiltration gallery or bankside storage can be used to improve poor raw water
quality, and reduce variability in quality.
Which treatment processes are used to treat the water can be affected by the abstraction
method chosen:
–
clarification/sedimentation may not be required if an infiltration gallery can
reduce the colour and turbidity of the raw water, and limit their variability (see
P5 series Guides)
–
filtration processes that need relatively good quality feed water can be
considered if the water can be improved by the abstraction method (see P6 series
Guides)
Ref P1.1, Version 1, January 2014
Water Safety Plan Guide:
Surface Water Abstraction – Rivers, Streams and Infiltration Galleries
1
–
2
the effectiveness of disinfection is improved if the abstraction method can help
reduce turbidity and colour (see P7 series Guides).
Water Safety Plan Guide:
Ref P1.1, Version 1, January 2014
Surface Water Abstraction – Rivers, Streams and Infiltration Galleries
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 P1.1.4, P1.1.5), and drawing water that cannot be
properly treated because the quality is too poor (see P1.1.3).
The most important preventive measures are:

regularly inspect the intake for damage or clogging (see P1.1.6.1, P1.1.7.1)

put an alarm on the flow from the intake to warn of an intake failure (see P1.1.7.1–4)

use an abstraction method that reduces water quality variability so periods of very poor
quality are avoided (see P1.1.2.1).
(References in parentheses are to the Risk Information Table.)
Ref P1.1, Version 1, January 2014
Water Safety Plan Guide:
Surface Water Abstraction – Rivers, Streams and Infiltration Galleries
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.
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

P1.1.1.1
Drought.


P1.1.1.2
Resource
consent
limitations.
4
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 river/stream’s safe
yield.
Water demand.

Source usage
rate.
Drop in system
pressure.

Customer
complaints
about low
pressure.
Negotiate new resource 
consents or emergency

provisions.
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.
Water Safety Plan Guide:
Ref P1.1, Version 1, January 2014
Surface Water Abstraction – Rivers, Streams and Infiltration Galleries
Causes
Preventive measures
Checking preventive measures
Corrective action
Signs that action
is needed
What to check
Event: RAW WATER QUALITY TOO POOR TO TREAT
Possible hazards: Germs and chemical determinands particularly disinfection by-products (trihalomethanes,
haloacetic acids, chloral hydrate).
Level of risk: High1
P1.1.2.1
Heavy rain
leading to high
levels of
turbidity and
organic matter
in water
entering the
plant.


Stabilise raw water

quality (using, eg,
infiltration gallery or raw
water reservoir) to avoid
periods of very poor
quality.
Take steps to allow
close down of intake
when river conditions
are such that water
cannot be adequately
treated:
–
–
–
–
1
establish levels of
raw water quality
that the plant
cannot treat
automatic
measurement of
raw water turbidity
and telemetric
warning
Raw water

quality (to
determine when
quality is
approaching the
limits of the
plant’s
treatment

capabilities).

River levels.

Storm warnings. 

Non-compliance 
with DWSNZ:
2000,
particularly

turbidity,
particle counts,
and E. coli.

Increased filter
backwash

frequency.
Unable to
achieve
effective
chemical
coagulation.
Review
alternative
source options.
Review pretreatment
options.
Slow the rate of
treatment.
Optimise
application of
coagulant
chemicals and
chlorine.
Difficulty in
achieving free
residual
chlorine in
treated water.
use regional council
upstream river
levels as an early
warning system
manage treated
reservoir levels to
maximise period
intake can be shut
down.

Turn off treatment.

Inspect catchment for
signs of erosion and
slips that will potentially
be ongoing problems.
Treatment plants are usually designed to be able to treat raw waters with a range of turbidity and colour (see
Guide P11). From time to time the raw water quality may exceed these limits, and the treated water quality may
not meet that required by DWSNZ.
Ref P1.1, Version 1, January 2014
Water Safety Plan Guide:
Surface Water Abstraction – Rivers, Streams and Infiltration Galleries
5
Causes
Preventive measures
Checking preventive measures
Corrective action
Signs that action
is needed
What to check
Event: CONTAMINATION OF THE RIVER OR STREAM
Possible hazards: Germs and chemical determinands appropriate to contamination sources.
Level of risk: Moderate2

P1.1.3.1
Contamination
sources (eg,
stock access to
river, septic
tanks, chemical
sources)
present in the
catchment.

Identify potential
sources of
contamination when
abstraction site is being
selected. (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
commissioning of the
source.

Restrict activities in the
catchment that may
contaminate the water.
(See Guide S1.1.)

Gather information
about the hydrology of
the catchment before
undertaking
development.

No survey of
potential
sources of
contamination
undertaken.

Add treatment
processes to
remove
identified
contaminants.

No hydrological
information
gathered.


No system for
obtaining
information
about changing
land use in
place.
Instigate system
to gather
information
about land use
changes.

High E. coli
counts in raw
water.
Event: WATER QUALITY NOT IMPROVED BY INFILTRATION GALLERY
Possible hazards: Germs and, if water is coloured, disinfection by-products (trihalomethanes, haloacetic acids,
chloral hydrate).
Level of risk: Low–high3

P1.1.4.1
Sediment load
in raw water too
high.
Establish levels of raw
water quality that the
gallery cannot handle,
and turn the gallery
pumps off when these
are exceeded.

Water quality

before and after
the gallery:
turbidity and
suspended
solids.
Turbidity
exceeds gallery
design
guidelines and
treatment
capability.

Review gallery
design.

Clean gravel
packs with
compressed air
lances.

Slow
abstraction rate
to reduce
filtration
velocities
through the
gravel packs.
2
The consequences of the event, and therefore the level of risk, will be influenced by the nature of the
contaminants and whether any treatment processes in use are capable of removing the contaminants.
3
The main consideration is to match the gallery design to the raw water quality.
6
Water Safety Plan Guide:
Ref P1.1, Version 1, January 2014
Surface Water Abstraction – Rivers, Streams and Infiltration Galleries
Causes
Preventive measures
Checking preventive measures
Corrective action
Signs that action
is needed
What to check
Event: WATER QUALITY NOT IMPROVED BY INFILTRATION GALLERY (cont’d)
P1.1.4.2

Poor infiltration
gallery design.
Take account of the
range of possible raw
water qualities when
designing the gallery.

Water quality

before and after
the gallery:
turbidity and
suspended
solids.
Insufficient
difference
between
turbidities of
raw water and
gallery outlet.

Review gallery
design and
modify if
necessary.

Consider
alternative
abstraction/
pre-treatment
system.

Slow
abstraction rate
to reduce
filtration
velocities
through the
gravel packs.

Clean gravel
packs with
compressed air
lances.
Event: INFILTRATION GALLERY PRODUCES LESS WATER THAN IT WAS DESIGNED TO
Possible hazards: Germs and chemicals that get into the water because of low system pressure; hazards
associated with poor hygiene.
Level of risk: Low–high4
P1.1.5.1

Clogged gravel
packs in the
infiltration
gallery.

P1.1.5.2
Turn off the gallery
under extreme
conditions to minimise
drawing sediment deep
into the gravel packs.
Flows.


Regular checks
on raw water
quality.
Reduction in
flow.

Abstraction
pump
cavitation.

Staining in
stream bed
gravels.

Determinands
of concern
found in gallery
filtered water.

Langelier
Saturation
Index is zero or
positive.
Regular programme to
scarify gravel pack with
tractor mounted unit.
(NB: If gallery is in the
stream bed a resource
consent will be
required.)

Regular programme of
cleaning gravel packs
using compressed air
lances.

Regular programme of
cleaning gravel packs
using compressed air
lances
Gravel packs
and/or screen
slots calcified or
clogged with

oxidised iron or
manganese.

Use raw water quality
data when planning the
abstraction process to
help decide whether a
gallery is appropriate
given the quality of
water.

In the raw
water:
– determinands
to calculate
the Langelier 
Saturation
Index
(hardness,
pH, alkalinity)
– iron and
manganese
Elevated levels
of iron and
manganese.

Scarify the
gravel packs, or
clean with
compressed air
lances.

Review extent
of problem and
consider
alternative pretreatment
options.

Scarify the
gravel packs, or
clean with
compressed air
lances.
– turbidity/
suspended
solids.
4
The high level of risk results when there is a severe lack of water. High sediment floods can cause problems
for a gallery because packed gravel beds become blocked.
Ref P1.1, Version 1, January 2014
Water Safety Plan Guide:
Surface Water Abstraction – Rivers, Streams and Infiltration Galleries
7
Causes
Preventive measures
Checking preventive measures
Corrective action
Signs that action
is needed
What to check
Event: INFILTRATION GALLERY PRODUCES LESS WATER THAN IT WAS DESIGNED TO (cont’d)

P1.1.5.3
Gallery clogged
by tree roots.

Avoid planting trees
near the gallery.
Remove trees
already present,
and determine
appropriate
method for
killing roots.
Event: TOO LITTLE WATER CAN BE DRAWN FROM THE INTAKE 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: High5

P1.1.6.1
Screens
damaged or
clogged.

P1.1.6.2
Booms and screens to
trap weed/algae.

Regular preventive
maintenance, as
required by the
conditions, and
manufacturers’
specifications:
lubrication, component
replacement, exercise
valves.

Regular inspections of
intake.

Telemetric alarm for low
flows from the intake.

Intake inspections,
regularly and directly
after floods etc, with
follow-up action if
required for existing
protection (eg, gabions,
piling, screens and
grates, etc).
Catastrophic
failure (eg,
flood, slips or
earthquakerelated
damage).

5
8
Limit nutrient input into
the raw water to reduce
clogging by algae and
weed under low-flow
conditions.

Failure of the
intake due to
mechanical or
structural
failure.
P1.1.6.3
Regular inspection and
cleaning of screens,
intensified during times
of flood.

State of intakes. 
Reduced flow.

Treatment plant 
flow meters.
Elevated algal
count.

Algal counts in
river.

Flows (from
intake).

Inspection
records.

Preventive
maintenance
log.




Failure of
significant
componentry.

No water.

Alarm activated.
Flood levels.

No water.
Flows (from
intake).

Reduced flow.

Alarm activated.
Inspection
records.
Telemetric alarm for low
flows from the intake.

Modify intake to
protect against
damage, and
reduce
likelihood of
clogging.

Implement plan
to reduce
nutrient input
into source.

Review
maintenance
and inspection
schedule.

Consider
alternative
source.

Review the
options for
bankside
storage.

Evaluate
existing
protection
system.
The level of risk will probably increase the lower the flow of the water is.
Water Safety Plan Guide:
Ref P1.1, Version 1, January 2014
Surface Water Abstraction – Rivers, Streams and Infiltration Galleries
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 INTAKE TO MEET DEMAND (cont’d)
P1.1.6.4

Pump failure
(see also Guide
P10).

Maintenance according
to manufacturers’
recommendations.
Standby pump with
auto-switch to alternate
pumps.


Telemetric
records

No water.

New pumps.

Alarm activated. 
Maintenance
records.

No
maintenance
record.
Instigate
maintenance
programme.

No water.

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.

Battery backed-up
alarms.
P1.1.6.6

Construct a fence
around the intake site.

Vandalism/
sabotage.
Damage to the
intake.

Install intruder alarm.

Evidence of
attempts to gain
access to the
intake.
P1.1.6.5
Power failure.

Consult with
power authority.

Obtain stand-by
generator.
Ref P1.1, Version 1, January 2014
Water Safety Plan Guide:
Surface Water Abstraction – Rivers, Streams and Infiltration Galleries
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 – Water quality too poor to treat
Indicators:
Required actions:
Responsibility:
10

Water too turbid or too coloured to treat.

Turbidity of water leaving plant consistently greater than
0.2 NTU‡ (See DWSNZ:2000).

Consider whether to cease abstraction and switch to an
alternative source of potable water until 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 the MOH.

Monitor particle counts, turbidity or colour levels until they
reach acceptable limits.

Increase chlorine residual as an interim measure.

Restart plant operation, perhaps at a slower rate.

If very poor raw water quality is likely to be a frequent
problem, consider an alternative source, or changes to
abstraction method or treatment.

Record cause of failure and corrective steps taken.

Plan and develop long term counter-measures if needed.

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:
Ref P1.1, Version 1, January 2014
Surface Water Abstraction – Rivers, Streams and Infiltration Galleries
Event – Not enough water reaching the treatment plant
Indicators:
Required actions:
Responsibility:

Reduced, or no, flow reaching the treatment plant.

Unexpectedly high usage.

Structural failure of intake, 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 if necessary.
Manager designated responsible for water supplies.
Ref P1.1, Version 1, January 2014
Water Safety Plan Guide:
Surface Water Abstraction – Rivers, Streams and Infiltration Galleries
11
Event – Contamination enters the river or stream
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.
Nephelometric turbidity units.
12
Water Safety Plan Guide:
Ref P1.1, Version 1, January 2014
Surface Water Abstraction – Rivers, Streams and Infiltration Galleries
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:
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 provides a useful tool for this purpose.

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, highlight
poor laboratory results or indicate that poor water quality is
reaching customers, then review the procedures for
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 the water supply.
Ref P1.1, Version 1, January 2014
Water Safety Plan Guide:
Surface Water Abstraction – Rivers, Streams and Infiltration Galleries
13