/ Water Safety Plan Guide
Worked Example of a Water Safety Plan for a Small Supply Using Rainwater
Version 1, Ref W1
January 2014

Citation: Ministry of Health. 2014. Water Safety Plan Guide: Worked Example of a Water Safety Plan for a Small Supply Using Rainwater, Version 1, ref W2. Wellington: Ministry of Health.

Published in January 2014
by the Ministry of Health
PO Box 5013, Wellington, New Zealand

ISBN: 978-0-478-42772-1 (print)
ISBN: 978-0-478-42773-8 (online)

Previously published in 2002 as Public Health Risk Management Plan Guide: Worked Example of a Public Health Risk Management Plan for a Small Supply Using Rainwater, Version 1, ref W2. This publication’s title and any reference within the text to ‘public health risk management plan’ were 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.

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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

Scenario

Water Safety Plan for Greendell School

Barriers to Contamination

Risk Information Table

Improvements

Regular Checks and Maintenance Schedules

Contingency Plans

Water Safety Plan Performance Assessment

Reporting

Ref W1Water Safety Plan Guide: 1

Version 1, January 2014Small Rainwater Supply

Ref W1Water Safety Plan Guide: 1

Version 1, January 2014Small Rainwater Supply

Introduction

This is one of two worked samples of a water safety plan (formerly known as a Public Health Risk Management Plan, PHRMP) to help small water suppliers (those with fewer then 500 people) prepare their water safety plans. Notes to help you understand how parts of this plan were prepared are printed in italics, and are headed as “Notes”.

The key processes in preparing water safety plans are:

  • Risk assessment

–Make a flow chart of the supply.

–Identify the elements in the supply so you can select the Guides you need.

–Make a check list of the four “barriers to contamination” your supply has, so that any that are missing can be identified.

–Prepare a Risk Information Table for your supply that lists the preventive measures, and checks what you should have in place to reduce risk.

–Prepare a list of improvements you need to make by comparing what you should have (Step 4) and what you actually have.

–For each improvement needed, estimate the level of public health risk if the improvement is not made.

–Rank the risks for the whole supply according to their size (take into account the seriousness of the health risk from each event, the likelihood of the event occurring, and sum up all the risks from the various process elements).

  • Risk management

–Work out the resources (dollars, staff, expertise, equipment) needed for each improvement.

–Work out a final overall priority for each improvement taking account of the level of health risk and the resources needed (Step 8) (use a cost-benefit approach).

–Develop a three-year programme for managing each risk.

–Prepare a summary of regular checks and maintenance that needs to be carried out.

–Prepare contingency plans that might be needed for your supply.

  • Plan evaluation and communication

–Prepare a list of instructions for reviewing the performance of the plan.

–Prepare a list of instructions for reporting.

Scenario

This example uses the imaginary Greendell School, which is a small cluster of buildings on the edge of Greendell village (also imaginery). The village is situated in a valley, about 20km from an active volcano. Native bush surrounds the village and many trees grow in the school grounds and near the buildings. Rainwater is collected from the roofs of the school buildings to provide a source of water. There is a high rainfall in the area and as a result the school never experiences water shortages.

The rainwater from the roofs is collected in three concrete storage tanks. From there it is pumped to a header tank on the hillside to provide gravity feed for the supply. After the header tank, the water passes through a cartridge filter, and is then disinfected by a ultra-violet disinfection system before being reticulated to the school buildings.

Greendale Rural School has four teachers, and a part-time caretaker who also looks after the water supply.

Water Safety Plan for Greendell School

Diagram of the water supply

The individual Guides used in the preparation of this Plan were:

  • S1.2Roof catchments
  • P6.3Cartridge filtration
  • P7.4Ultra-violet irradiation
  • P10Pump operation
  • D2.3Operation (reticulation network)
  • D2.4Backflow prevention
  • G1Staff training
  • G2Monitoring

Barriers to Contamination

The barriers to contamination in place in the Greendell School supply, and the concerns about how well they work, are summarised in the following table:

Barriers to: / Comment
Stop contamination of raw water / There are a number of ways in which the raw water could be contaminated. The improvements needed to stop contamination are listed.
Remove particles from the water / Cartridge filter
Kill germs / Ultra-violet disinfection – the UV unit is old and does not have a light sensor. This is listed in the needed improvements.
Prevent recontamination after treatment / The important steps to stopping contamination after treatment have been or are being taken:
  • The water supply is totally enclosed after treatment and not open to external contamination.
  • There are no places where water could be sucked back into the supply.
  • A qualified plumber is always called when work on the water supply is needed.

Notes on the barriers to contamination

Look through the Risk Information Table (next section) to determine which barriers to contamination your supply has, and how effective they are likely to be. Preparing a table like that above will help you to identify barriers your supply is missing.

Risk Information Table

Checking water quality

Checks for germs are the most important checks on water quality you can do. As a result, these checks could be listed many times in the following table. To keep the table as simple as possible, the checks for germs are not included, but remember that the Drinking-water Standards for New Zealand require that:

Checks for germs (the test is usually for a germ called E. coli) should be made at least once a month in the water:

  • directly after treatment
  • and in the reticulation network.

If E. coli is found in either case, there is a problem that needs to be investigated. You may also wish to take a sample of water before treatment from time to time, to check on the quality of water entering your supply.

If something happens to make you think animal or human excrement may have got into the water, you should immediately take samples to check whether there are germs in the water. Where you take the samples will depend on what has happened.

If you are unsure about what you have to do when checking for germs, contact a health protection officer with your local District Health Board.

Where possible, the checks listed in the risk information table are those that can be made without having to test the water, but you can do checks to test the water if you are worried about the water quality.

Abbreviations: DWSNZ – Drinking-Water Standards for New Zealand; MAV – Maximum acceptable value – see DWSNZ:2000; Council – regional/district council or unitary authority.

Causes / Preventive measures / Checking preventive measures / Corrective action
What to check / Signs that action is needed
The roof catchment and water storage
Event: ANIMAL DROPPINGS AND CHEMICAL CONTAMINANTS CARRIED ONTO ROOF OR INTO GUTTERING
Possible hazards: Germs, pesticides, other chemical contaminants that may be airborne.
Level of risk: High1
C1.1.1
Overgrown trees:
–may allow animals and birds to contaminate the roof
–water dripping off branches onto the roof may carry contaminants
–dead animals may fall into the guttering. /
  • Cut back trees.
  • Clean out guttering.
  • Put wire or plastic mesh over the top of the downpipe, or over the whole guttering, to stop leaves getting into the tank.
/
  • Check tree growth at least annually.
  • Check guttering at least annually.
/
  • Overgrown trees.
  • Dirty guttering.
/
  • Cut back trees.
  • Disconnect downpipe from tank and clean guttering.
  • Disinfect the water.

C1.1.2
Droppings from birds or animals on roof or in guttering. /
  • Keep roof and guttering clean and use first flush diverter.
  • String wire along the ridgeline to stop birds roosting.
  • Take actions to avoid attracting birds, eg. don’t feed them and tidy away rubbish.
/
  • Quarterly inspection of roof and guttering for droppings.
/
  • Droppings on roof or in guttering.
/
  • Disconnect downpipe from tank and clean roof and guttering.
  • Disinfect the water.

1The germs create a ‘high’ risk, not the chemicals.

Causes / Preventive measures / Checking preventive measures / Corrective action
What to check / Signs that action is needed
Event: ANIMAL DROPPINGS AND CHEMICAL CONTAMINANTS CARRIED ONTO ROOF OR INTO GUTTERING – cont’d
C1.1.3
Chemical contaminants from the air (including aerial spraying) settle on roof. /
  • Ask the council for help to reduce air pollution in the area (using discharge consents). Keeping notes on contamination incidents may help.
  • Consider using a water source less affected by air pollution.
  • After possible contamination disconnect downpipe before the next rain (or use a first-flush diverter).
  • Check your chimney is long enough that material from the fire will not settle on the roof.
/
  • Find out which chemical sprays are in use nearby.
  • Appearance of roof.
/
  • Noticeable taste in the water.
  • Algal growths in water tank if fertilisers have contaminated the roof.
  • Visible deposits of ash/soot on the roof.
/
  • Ask for council help to reduce sources of air pollution.
  • Use a new source unaffected by air pollution (eg, groundwater).
  • Install a first-flush diverter.
  • Lengthen chimney.

C1.1.4
Chemical contamination by sprays used to protect roof timbers, or proof against spiders. /
  • Tell the contractor that the roof is used to collect drinking-water, and that there must be no overspraying.
  • Get a guarantee from the contractor that persistent organochlorine pesticides2 will not be used.
  • Use first-flush diverter or disconnect downpipe, before first rain after treatment of the roof.
/
  • List of pesticides used by contractors.
  • If you are worried that spray has got onto the roof, sample for pesticides in the water.
/
  • Use of persistent organochlorine insecticides2 by contractor.
  • Overspraying happened.
  • Water contains pesticides at concentrations more than 50% of their MAV.
/
  • Use different contractor.
  • Thoroughly wash down the roof – disconnect the downpipe.
  • Use an alternative water source until decontamination is complete.

C1.1.5
Vandalism/ sabotage. /
  • Make it as difficult as possible for people to get onto the roof, eg lock away ladders.
  • Check the roof regularly for signs of intentional contamination (eg, bags of chemicals).
/
  • Check the roof for unexpected objects.
  • Check the area around the building for things that may make getting onto the roof easier.
/
  • Signs that someone has got onto the roof without permission.
/
  • Remove things that might help people get onto the roof.
  • Remove contaminants from the roof, disconnect downpipe and wash down.

2This chemical group includes: aldrin, dieldrin, lindane chlordane, DDT, DDE, so check whether any of these chemicals are in the product being used by the contractor.

Causes / Preventive measures / Checking preventive measures / Corrective action
What to check / Signs that action is needed
Event: MATERIALS DISSOLVED FROM THE ROOF, FLASHING, GUTTERING OR DOWNPIPES BY RAINWATER
Possible hazards: Heavy metals (lead, copper, chromium, cadmium).
Level of risk: Moderate
C1.2.1
Roof materials containing lead, and guttering made from metals that can corrode. /
  • Use lead-free materials on the roof (paints, flashings, nails).
  • Keep roof surface in good repair.
  • Use plastic guttering.
/
  • Check condition of roof surface at least annually.
  • Building materials, or paint, used on the roof.
  • Test for heavy metals in roof paint.3
/
  • Roof surface in poor condition – needs repainting or replacing.
  • Leaded paint test on roof paint is positive.
  • Lead flashing used on the roof.
  • Cases of lead (or other heavy metal) poisoning, but be aware that such cases may have other causes.
/
  • Replace materials that contain heavy metals.
  • Repaint roof, or replace roof.
  • Replace guttering.

Event: CONTAMINATION OF WATER WHILE IN THE STORAGE/HEADER TANK
Possible hazards: Germs.
Level of risk: High
C1.3.1
Animals getting into storage tank. /
  • Ensure the tank is covered.
  • Put mesh on vents, overflow, etc.
  • Check inside of tank monthly.
  • Remove vegetation near tanks
  • Put a slippery metal band around wooden tanks to prevent animal access from ground level.
/
  • Monthly tank inspection.
/
  • Dead animals found in tank.
  • Mesh/grills disturbed by animals to get into the tank.
  • Unpleasant taste and odour.
  • Water cloudy.
/
  • Remove animal remains, and disinfect the water before use (eg, UV disinfection).
  • Replace or provide mesh where necessary.
  • Prepare a timetable for checking the tank.

C1.3.2
Accumulation of sediment in storage tank. /
  • Clean the tank each year.
  • Use two storage tanks, the first feeding into the second, and draw water from the second (this reduces sediment being carried through into the reticulation).
/
  • Monthly tank inspection.
/
  • Dead animals found in tank.
  • Mesh/grills disturbed by animals to get into the tank.
  • Unpleasant taste and odour.
  • Water cloudy.
/
  • Start inspection and cleaning programme.
  • Install a second tank.

C1.3.3
Vandalism/ sabotage. /
  • Take steps to stop people getting access to the tank (fences, locked hatches).
/
  • Regular inspection of tanks for signs of someone getting into the tank.
/
  • Signs that someone has got into the tank without permission.
/
  • Fence tank, or provide lockable hatches.

3Seek help from a health protection officer from the District Health Board. They should have a small kit that will allow a quick test of the paint.

Causes / Preventive measures / Checking preventive measures / Corrective action
What to check / Signs that action is needed
Event: NOT ENOUGH WATER
Possible hazards: Hazards associated with poor hygiene.
Level of risk: High
C1.4.1
Too little rainfall as well as too little storage, high use of water, or a leak in tank or guttering. /
  • Make sure tank is big enough.
  • Make sure guttering is strong enough for wind and snowfall conditions.
  • Check tank and guttering monthly for leaks.
  • Stop unnecessary use of water.
/
  • Water level in tank.
  • Rate of water use.
/
  • Water supply often runs out.
  • Water level is low.
  • Signs of water leaking from tank.
/
  • Get new tank.
  • Find a new or additional source of water.
  • Repair tank and/or guttering.
  • Take steps to save water.

C1.4.2
Mechanical failure of pump (header tank short of water). /
  • Do preventive maintenance on pump:
–daily visual inspections
–lubrication
–seal replacement
–leaks repaired
–corroded components replaced
–annual ammeter tests.
  • Planned maintenance programme for replacement of pump parts (follow per manufacturer’s recommendations).
/
  • Pump maintenance log.
/
  • Frequent pump breakdowns.
  • Pump maintenance not being done.
/
  • Revise, or put in place a pump maintenance schedule.

C1.4.3
Power failure to pump. /
  • Install an alarm that warns that the power has failed.
  • Install a stand-by generator.
  • Regularly maintain the power supply (if you have a diesel generator, for example).
/
  • Alarm.
  • Electricity supply.
  • Water flow.
/
  • Alarm is triggered.
  • No electricity reaching the pump.
  • No water flow to header tank when pump should be operating.
/
  • Make arrangements to get a more reliable power supply.

Cartridge filtration
Event: FILTER NOT REMOVING PARTICLES DOWN TO 2 µm IN SIZE
Possible hazards: Large germs (Giardia and Cryptosporidium not removed).
Level of risk: High4
C1.5.1
Wrong type of cartridge filter. /
  • Use filters that are certified to remove particles down to 2m in size.
  • Make sure filter cartridge is compatible with the filter housing and note the type of filter used.
/
  • National or international certificate of filter’s capabilities.5
  • Record of filter types used.
/
  • Cloudiness in the water following filtration.
  • Customer complaints.
  • Cases of diarrhoea in people drinking the water.
  • Wrong filter type used.
/
  • Change to a different type of filter.
  • Keep list of filters that match the housing in use.

C1.5.2
Damage to the seal between the cartridge and filter housing. /
  • Check the condition of the filter housing and the cartridge seal when changing filters.
  • Make sure the person replacing the cartridges knows the correct way to do it.
/
  • The state of the filter seal.
  • Filter maintenance log.
  • Appearance of the water.
/
  • Cloudiness in the water following filtration.
  • Customer complaints.
  • Cases of diarrhoea in people drinking the water.
  • Frequent damage to seal.
/
  • Decide whether the cartridge or housing is damaged, and replace damaged unit.
  • Train staff in replacing cartridges if necessary.
  • Read filter manufacturer’s instructions.

C1.5.3
Cartridge not properly seated in the mounting. /
  • Make sure the cartridge is fitted the correct way round (some only work one way).
  • Make sure base of filter housing is wiped clean before reseating filter cartridge.
  • Make sure cover is replaced properly.
  • Check, directly after re-seating it, that the filter is removing particles. (Checks are described in Sections 3.2.3.1 and 11 of DWSNZ: 2000).
  • Make sure the person replacing the cartridges knows the correct way to do it.
/
  • Results from particle removal checks.
  • Appearance of the water.
/
  • Cloudiness in the water following filtration.
  • Filter unable to remove more than 99.9% of particles greater than 2 µm in size entering it.
  • Customer complaints.
  • Cases of diarrhoea in people drinking the water.
  • Frequent incorrect seating of filter.
/
  • Read filter manufacturer’s instructions.
  • Train staff in replacing cartridges if necessary.

4The level of risk will depend on the type, and effectiveness, of any disinfection after cartridge filtration.