/ 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.

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Contents

Introduction

Risk Summary

Risk Information Table

Ref S2Water Safety Plan Guide: 1

Version 3, January 2014Development of New Supplies

Ref S2Water Safety Plan Guide: 1

Version 3, January 2014Development of New Supplies

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 andpoor 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.

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.)

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 / Corrective action
What to check / 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
  • Source characteristics are unknown
/ Groundwater
  • Obtain data to establish annual variation in water quality and quantity. Suggested tests (quantity):
–Constant discharge
–Step drawdown
–Specific capacity /
  • Constant discharge aquifer test data.
  • Step drawdown aquifer test data.
  • Specific capacity test summary.
/
  • Unsatisfactory results for the expected and predicted long term demand.
  • Sustainable supply for meteorological conditions and demands on resource from other users.
/
  • Choose alternative or additional source.
  • Consider options for management of demand.

Surface water
  • 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 /
  • 5 year low flow data.
  • Mean annual rainfall in catchment.
  • Results of probabilistic analysis.

S2.1.2
  • Unusual weather conditions
/
  • Choose source with manageable changes in unusual weather events.
/
  • Turbidity and colour measurements after heavy rainfall.
  • 5 year low flow data
/
  • Back-up supply is likely to be frequently required.
  • No back up supply available.
/
  • Choose alternative or additional source.

  • Ensure that a back-up supply will be available for emergencies.

S2.1.3
  • Power failure
/
  • Generator for use in situation of power failure.
/
  • Unreliable power supply.
  • No generator available.
/
  • Plan to have generator available.

  • Adequate storage.
/
  • No storage available, either pre- or post treatment.
/
  • Include storage facilities in design specifications.

Causes / Preventive measures / Checking preventive measures / Corrective action
What to check / Signs that action is needed
Event: POOR, CHANGEABLE OR DETERIORATING WATER QUALITY
Possible hazards:Germs; chemical determinands
Level of Risk: High1
S2.2.1
  • Adequate water quality data not available (microbiological, chemical, radiological).
/
  • 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.
  • See water safety plan P1.3
/
  • As defined in DWSNZ:2000.
/
  • Methodology described in DWSNZ: 2000 not followed. (If supply is found to be non-secure, treatment to ensure microbiological quality will be required).
/
  • Initiate groundwater security determination.

S2.2.2
  • Available water quality data not properly assessed.
/
  • “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 health-significant contaminants detected in source water
–production of a an inventory of possible contaminants in the protection area.
  • See Guide S1.1
/
  • Source water quality data
  • Information about activities or sites in the source protection area that may lead to contamination of the source water.
/
  • Source protection area not identified
  • 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.

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 pre-treatment storage is considered to dampen the effects of weather extremes.
  • See Guides P1.1, P1.2
/
  • 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 / Corrective action
What to check / 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.
/
  • 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.

  • Investigate land use changes as they occur.
  • (See Guide S1.1)
/
  • 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
S2.3.1
  • Incorrect choice of treatment
/
  • 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.
/
  • Compliance with DWSNZ:2000 is unlikely to be achieved.
  • Problems with aesthetic quality
/
  • Start monitoring of potential source water.

S2.3.2
  • Incorrect choice of treatment technology
/
  • Monitor chemical and physical parameters of source water to identify range of water quality and its variability.
/
  • 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.

  • Determine:
–maximum and minimum demand for water
–rates of change of water quality
–how water quality is affected by season.
Causes / Preventive measures / Checking preventive measures / Corrective action
What to check / Signs that action is needed
Event: WATER MAY BECOME CONTAMINATED DURING DISTRIBUTION
Possible hazards:Germs; chemical determinands
Level of risk: Moderate
S2.4.1
  • Backflow prevention inadequate
/
  • Backflow prevention devices at all locations where backflow can occur and hazards to public health exist.
  • (See water safety plan D2.4)
/
  • Inadequate specifications for backflow prevention.

S2.4.2
  • Materials used in distribution system contaminate the water
/
  • Specify the use of suitable materials in construction of the distribution system
  • (See water safety plan D2.1)
/
  • Distribution system plans do not meet the requirements of AS/NZS 3500.1: National plumbing and drainage: Water supply.

S2.4.3
  • Dead ends in the distribution system
/
  • Distribution system analysis designed to limit areas of low flow, and therefore stagnation of the water.
/
  • 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
  • Inability to take samples from certain locations
/
  • Inadequate or no sampling ports
/
  • Sampling ports not agreed with HPOs as part of design specifications.

S2.5.2
  • No monitoring plan
/
  • Determine monitoring requirements for compliance with DWSNZ:2000, plus any additional measurements.
/
  • Compliance with the DWSNZ:2000 will not be achieved.

S2.5.3
  • No assessment of results
/
  • Train someone to assess results to determine when action is required.
/
  • Compliance with the DWSNZ:2000 will not be achieved.

S2.5.4
  • No maintenance plan
/
  • Develop maintenance plan appropriate to the supply
  • (See water safety plan 2.3)
/
  • Water safety plan contingency plans are likely to be used frequently.

Ref S2Water Safety Plan Guide: 1

Version 3, January 2014Development of New Supplies