Water Safety Plan Guide: Worked Example of a Water … · Web viewThe village is situated in a...

Water Safety Plan Guide

Worked Example of a Water Safety Plan for a Small Supply

Using RainwaterVersion 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 2014by 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.

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

IntroductionScenarioWater Safety Plan for Greendell SchoolBarriers to ContaminationRisk Information TableImprovementsRegular Checks and Maintenance SchedulesContingency PlansWater Safety Plan Performance AssessmentReporting

iv [Title]

Ref W1 Water Safety Plan Guide: vVersion 1, January 2014 Small Rainwater Supply

IntroductionThis 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.

Ref W1 Water Safety Plan Guide: 1Version 1, January 2014 Small Rainwater Supply

2 Water Safety Plan Guide: Ref W1Small Rainwater Supply Version 1, January 2014

ScenarioThis 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 SchoolDiagram of the water supply

Collection of waterfrom roof

Water storagetanks Pump

Headertank

Cartridgefiltration

UVdisinfection

Reticulationpipework around

the school buildings

The individual Guides used in the preparation of this Plan were: S1.2 Roof catchments P6.3 Cartridge filtration P7.4 Ultra-violet irradiation P10 Pump operation D2.3 Operation (reticulation network) D2.4 Backflow prevention G1 Staff training G2 Monitoring


Barriers to ContaminationThe 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 contaminationLook 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 TableChecking water qualityChecks 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 GUTTERINGPossible hazards: Germs, pesticides, other chemical contaminants that may be airborne.Level of risk: High1

C1.1.1Overgrown 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.

C1.1.2Droppings 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.

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





Event: ANIMAL DROPPINGS AND CHEMICAL CONTAMINANTS CARRIED ONTO ROOF OR INTO GUTTERING – cont’d

C1.1.3Chemical 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.

C1.1.4Chemical 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.





C1.1.5Vandalism/ 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.

2 This 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.




Event: MATERIALS DISSOLVED FROM THE ROOF, FLASHING, GUTTERING OR DOWNPIPES BY RAINWATERPossible hazards: Heavy metals (lead, copper, chromium, cadmium).Level of risk: Moderate

C1.2.1Roof 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 TANKPossible hazards: Germs.Level of risk: High

C1.3.1Animals 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.

C1.3.2Accumulation 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.

C1.3.3Vandalism/ 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.

3 Seek 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.




Event: NOT ENOUGH WATERPossible hazards: Hazards associated with poor hygiene.Level of risk: High





C1.4.1Too 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.

C1.4.2Mechanical 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.

C1.4.3Power 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 SIZEPossible hazards: Large germs (Giardia and Cryptosporidium not removed).Level of risk: High4

C1.5.1Wrong 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.

C1.5.2Damage 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.




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.

C1.5.3Cartridge 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.



Filter unable to remove more than 99.9% of particles greater than 2 µm in size entering it.



Frequent incorrect seating of filter.

Read filter manufacturer’s instructions.

Train staff in replacing cartridges if necessary.


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

5 For example, certification under NSF Standard 53 or AS/NZ 4348:1995.




Event: FILTER NOT REMOVING PARTICLES DOWN TO 2 m IN SIZE – cont’d

C1.5.4Cartridge failure.

Regularly replace filter cartridges, and wash pre-filters. Note the date and what is done.

Before buying new cartridges check they have certificates showing they meet specifications.

Flow rate. Difference

between the pressure before the filter and after the filter. (Sudden changes in flow or the pressure difference may indicate filter or pre-filter failure.)

Performance certificates.

Pressure difference is lower than usual, or flow is higher than usual.




Records not kept.

Wash the filter cartridge and flush to waste until checks show that particle removal is again effective.

Get another batch of cartridges.

Consider changing filter supplier.

C1.5.5Contamination of filter housing when changing the cartridge.

Disinfect filter housing when installing the cartridge, and flush to waste to remove residual disinfectant.

Make sure the person replacing the cartridges knows the correct way to do it to avoid contamination.

Test the water leaving the filter for the disinfectant.6

Disinfectant concentration not reduced to an acceptable level.



Continue flushing until the disinfectant cannot be detected.

Train staff if necessary.

C1.5.6Flow too high for cartridge design.

Keep flow rate less than the maximum the filter can handle.

Flow rate. Flow too high. Cloudiness in the

water following filtration.



Reduce flow to within specifications.

6 If household bleach (chlorine) is used to disinfect the filter housing, chlorine test tablets from a swimming pool test kit can be used for this. They turn pink when there is chlorine in the water. Use 1 tablet in 10ml of water; a slight pink colour indicates that the chlorine concentration is acceptable.





Event: GROWTH OF GERMS IN THE FILTERPossible hazards: Germs (released from filter into treated water).Level of risk: Moderate

C1.6.1Filter used in the wrong situation or beyond its capacity.

Disinfect7 the water before it goes through activated carbon cartridges used to reduce taste problems (including those claiming to stop the growth of bacteria).

Regularly replace filter cartridges (especially carbon filters). Note the replacement date.

Record filter type used.

Check recommended filter lifetime and installation date of cartridge in use.

Customer complaints and sickness.

Timetable for replacing filters not followed.

Avoid using a carbon filter or disinfect the water before it gets to the cartridge.

Disinfect water after the filter.

Plan when filters have to be replaced, and note replacement dates.

UV disinfection

Event: UV DOSE TOO LOWPossible hazards: Germs not killed.Level of risk: High8

C1.7.1Too little UV light passing through the water.

Regularly clean the lamp sleeves and light sensor lens.

Regularly replace lamp and record the date.

Make sure the light sensor is on the wall of the unit farthest from the lamp.

Lubricate the lamp seal each time the lamp is removed (use water-based lubricant).

Install an alarm that warns when the light intensity is too low and shuts off the water flow.

Light intensity. Alarm. Signs of scale

on the lamp sleeve and sensor lens.

Records of lamp replacement and when sleeves and sensor were cleaned.

Alarm triggered (light intensity too low).

Water flow shut off.

Water inside lamp sleeve (poor seal).

No maintenance records.

Clean lamp sleeve and sensor lens.

Replace lamp. Move sensor so

that it measures the light intensity at the wall farthest from the lamp, or buy a unit with a sensor in the right place.

Lubricate lamp seal with approved lubricant.

Add chlorine to the storage tank until satisfactory water quality can be restored, or close the supply down and arrange for another supply of water.

7 This is best done by adding chlorine to the holding tank. Use 1 teaspoon of bleach per 150L of water in the tank. This gives a chlorine concentration of about 1 mg/L.


8 The quality of the source water and how well other treatment processes before the UV unit work will affect the level of risk.




Event: UV DOSE TOO LOW – cont’d

C1.7.2Germs exposed to too little light because water flow is too fast or water is too cold.

Regularly check and record water flow to make sure it meets manufacturer’s requirements.

Follow manufacturer’s instructions about adjusting water flow if the water is cold.

Water flow records.

Minimum-maximum thermometer readings of water temperature.

Flows are low or very changeable.

Water temperature is low enough to affect lamp intensity.

Replace or repair the flow controller.

Reduce the water flow if the water temperature is too low.


C1.7.3Water discoloured or cloudy.

Install a filter before the UV disinfection unit and make sure it works (see C1.5.1–C1.6.1).

See C1.5.1–C1.6.1.

C1.7.4Power supply failure.

Install an alarm that warns that the power has failed, and shuts off the water flow.

Install a stand-by generator.

Regularly maintain the power supply (if you have a diesel generator, for example).

Alarm. Power to UV

disinfection unit.

Alarm is triggered

No electricity reaching the UV unit.

Make arrangements to get a more reliable power supply.



Causes Preventive measures Checking preventive measures

Corrective action

What to check

Signs that action is needed

Reticulation system

Event: CONTAMINATION ENTERS THE WATER AFTER TREATMENTPossible hazards: Germs, chemicals.Level of risk: High9

C1.8.1Breaks, leaks or damage to the pipes.

Where you can see pipes, check them for signs of damage or breaks every six months. If the pipes could be damaged by floods or slips, also check after heavy rain.

Reduce the corrosiveness of the water by placing marble chips in the holding tank, for example.

Where pipes are above ground, make sure they are protected from accidental damage.

Require subcontractors to report any damage to water supply pipes they cause.

Water pressure at taps.

Damage checks.

Signs of leaks found during checks.

Much more water used than expected.

Rust-coloured water, or water with a bitter “iron” taste.

Leaks appear often.

Start checking the pipes regularly.

Get advice on how to make the water less corrosive.

See if you can provide better protection for the pipes.

C1.8.2Contaminants enter the water during repairs to the reticulation.

Get a properly qualified person to make any repairs. This person must:– thoroughly wash their

hands before making the repair

– clean and disinfect with chlorine all tools (very important if they have also been used with wastewater)

– flush the repaired pipe to remove any dirt

– fill the repaired section of pipe with chlorinated water, allow it to sit, then thoroughly flush.

Record where the repair was made, and who made it.


Repair records.

Water is discoloured, or tastes or smells bad.

People who drink the water get sick.

Repair is not recorded.

Employ a registered plumber to make the repairs OR make sure the person making the repairs is properly trained.

C1.8.3Water pipes are laid too close to the sewer.

Use a properly qualified contractor to lay pipes.

Plans showing locations of sewers and drinking-water pipes.

Plans show the sewer and drinking-water systems run close together.

Get contractor to relocate pipes to make sure there is enough separation.

9 The level of risk will be high if UV disinfection takes place a long way from the point of use, or water is stored after treatment.


Causes Preventive measures Checking preventive measures Corrective action

What to check

Signs that action is needed

Event: CONTAMINATION ENTERS THE WATER AFTER TREATMENT – cont’d

C1.8.4Illegal cross-connection to the water supply.

Make sure only properly qualified people make connections to the supply.

Inspection of work.

Cross-connections found.



Employ a registered plumber to make connections OR make sure the person making the repairs is properly trained.

C1.8.5Contaminants are sucked into the reticulation (“backflow”).

Check the reticulation for places where water can be sucked back into the drinking water if the supply pressure drops.

Where backflow is possible, make sure that one of the following is installed:– backflow-

prevention device– double check valve– air gap.

(Some places were these devices may be needed are: swimming pools; stock troughs; boilers; tanks used for preparing agrichemicals; school laboratories.)

Check the supply for places where backflow prevention is needed.

Check shows there are places where backflow may occur, but there is no device to prevent it occurring.



Install devices to stop backflow where they are needed.

C1.8.6Vandalism or sabotage.

Regularly inspect backflow prevention devices, and exposed pipes or valves.

Where possible, provide lockable enclosures for parts of the supply that might be intentionally damaged.

Check for signs of damage.

Signs of damage to a part of the supply.



Repair or replace damaged components.

Provide protection to stop future damage.


Causes Preventive measures Checking preventive measures Corrective action


Monitoring

Event: WATER TEST RESULTS UNRELIABLE10

Possible hazards: Germs, chemicals.Level of risk: High

C1.9.1Samples taken wrongly.

Get advice from a health protection officer about the sampling you need to do to comply with the DWSNZ. You need to know:– where to take the

samples– how often samples

have to be taken– how to take the

samples so that there is no contamination of the sample

– what to do if a sample shows the water quality is poor. (This table will help with this.)

Prepare a sampling plan to record when and where samples need to be taken, and who is to take them.

Check that the sampling plan is being followed.

Sampling does not meet the requirements of the DWSNZ.

Buy a copy of the DWSNZ to help you understand the monitoring you have to do.

Get more advice from a health protection officer to discover why there are problems with the monitoring.

Staff training

Event: TREATMENT NOT OPERATED PROPERLYPossible hazards: Germs, chemicals.Level of risk: High

C1.8.1Operator not trained well enough.

Get experienced operators to pass on their knowledge to new operators.

Make sure the operator understands:– how the supply

operates– how it has to be

maintained– what to look for to

check it is operating properly

– who to contact if they need help.

Find out about operator training courses.11

Put some money aside to help pay for operator training.

How well the supply runs.

Things happen in the supply that result from poor staff skills and/or knowledge.

Check with the operator if there are things about the system they do not understand.

Make plans to get the operator the training they need.

Find enough money to train the operator.

10 The laboratory may also make mistakes, but the concerns here are mistakes that the water supplier can tackle.


11 New Zealand Water and Waste Association (NZWWA) can provide this information: PO Box 13-880, Onehunga, Auckland, Ph: 09 636 3636; Fax: 09 636 1234; Email: [email protected]; Website: http://www.nzwwa.org.nz.


ImprovementsComparison of the information in the Risk Information Table with the actual supply, shows the following problems:

Many of the roofs are over-hung by trees. The roof areas under the trees may be contaminated by the droppings of birds or animals.Action needed: The trees need to be pruned back, probably on a regular basis.

The ultra-violet disinfection system does not have a light sensor to show when the light intensity is too low to kill germs.Action needed: A new disinfection unit is needed, or the modification of old one.

The access openings in the roofs of the water storage tanks have not been designed properly. As a result, when it rains, water running from the roofs of the tanks can run directly into the stored water.Action needed: A lip needs to be built around the edge of the opening, and sealed so that water runs around and away from the opening.

The hatches for the tanks are presently unlocked. Vandals could get access to the water.Action needed: Buy padlocks and fit them to the hatches.

The caretaker is unsure of what to do when taking monitoring samples. Unless samples are taken properly, reliable information about water quality will not be available to help judge how well this plan is working. Also, the school will be unable to show that its water supply complies with the Drinking-Water Standards for New Zealand.Action needed: Contact the District Health Board and ask for assistance from an HPO to come and show what has to be done when samples are to be taken.

These problems show that in the Greendell School supply, two of the four key barriers needed to protect a water supply are incomplete. Some important steps that could be taken to protect the raw water from contamination have yet to be taken, and although there is disinfection, it may not be working properly because there is no check on the light intensity.

The order for these actions is listed in the following Improvements Schedule, and the actual timetabling is given in the Action Timetable.


Improvements schedule1 2 3 4 5 6 7 8 9

Costs

# Improvement needed

Level of risk (see

Risk Information Table)

Health priority

Can the improvement

be made within the next few weeks

Staff time

Equipment and any

installation costs

(estimated)

Overall priority for making the improveme

nt

Comments

1 Cut back trees. High 2 Yes Low $10 1 Cost – chainsaw petrol for working bee.

2 Install a UV unit with a light intensity sensor correctly positioned.

High 1 No, but work can start on it

soon.

Moderate

$5000(new UV

unit).

3 Cost of a new UV unit cannot be met by the school’s operating budget. A request for funding will have to be put to the Ministry of Education. The request can be made fairly quickly, but it will not be possible to schedule this improvement until we hear back from the Ministry.

3 Modify storage tank openings to keep rain from running off into the tanks.

High 3 Probably not Low $300 4 Cost – local engineering firm to make up new hatch mountings.

4 Provide locks for storage tank hatches.

High 5 #3 must be done first

Very low

$25 5 Cost – three padlocks.

5 Train the caretaker in how to take monitoring samples.

High 4 Yes Low $0 2

The school’s annual budget for operation of the water supply is $200. Improvements #1, #4 and #5 could therefore be afforded this year, but funds will have to be carried forward to next year to provide enough funding for Improvement #3. Improvement #2 is well outside what the school can afford, and funding assistance will need to be requested from the Ministry of Education.

Notes on the Improvements ScheduleColumn 3: These are the levels of risk given in the Risk Information Table for the event each Improvement is supposed to stop happening. The Ministry of Health’s “How to Prepare and Develop Public Health Risk Management Plans for Drinking-Water Supplies” booklet suggests listing these levels as a starting point for deciding on the health importance of each improvement. In this case, all the events have a “high” estimated level of risk, which doesn’t help in giving the improvements a Health Priority. Instead, you will have to compare the five improvements in the way discussed below in “Column 4” for the Greendell School example.

Column 4: In this column you give each improvement a ranking (from 1 to 5 in this case) based on its health importance only. Do not worry about the cost or whether you have the resources when deciding on the health priority. The reasons for the rankings given to the Greendell School improvements are as follows:


Even with all steps taken to protect the roof from contamination, there will always be the possibility of some contamination getting into the raw water. Fixing the problem with the disinfection system is therefore more important than the improvements that affect the raw water quality. Therefore Improvement #2 is ranked “1”.

Improvement #1 is considered more important that Improvement #3 because more contamination is likely to get into the water from the roof than into rain running into the tank through the hatches. Therefore Improvement #1 is ranked “2”.

Correct monitoring of water quality indicates when barriers to contamination are not working. But it is more important to have barriers in place to prevent contamination in the first place. In the case of Greendell School, Improvement #3 is therefore considered more important than Improvement #5, and Improvement #3 is ranked “3”.

Vandalism or sabotage of the Greendell School supply is considered very unlikely to happen, and having reliable information about the quality of the water is more important. Therefore Improvement #5 is ranked “4”, and Improvement #4 “5”.

Making decisions about the health importance of improvements can be difficult. If you have a long list of improvements, sorting them into categories such as “high importance”, “medium importance” and “low importance” provides a good start. Sorting out which improvements fall into each of these groups is probably more important than working out the detailed order within each group. If you are having difficulty, go to your local city or district council and get advice from an environmental health officer.

Column 5: One of the things you need to think about when deciding the order in which you should make improvements, is how easy each improvement is to make. Work on improvements that can be made easily and quickly should be a given high priority, even if they do not have a high health priority. This column lets you note down whether any of the improvements can be made quickly.

Column 6: Columns 6 and 7 collect estimates of costs for each Improvement. How well you can fit the improvement into your budget is likely to affect the overall priority for attention you are able to give it. In Column 6 you can note down whether you think this work is likely to take up much staff time. In the Greendale School example, a number of the improvements will probably take up only an hour or two of staff time. Getting a new UV system installed may take more time than the others for both the head teacher, who will have to prepare a case to the Ministry of Education for funding, and the caretaker who will need some training in how to use it. There is no need to know the exact time required, so long as it is possible to work out a rough level that will help in the final ranking of the improvements.


Column 7: Some idea of the cost of each improvement (including the equipment and installation) is needed here. Estimates in dollars will be helpful in deciding which improvements can be made within your budget.

Column 8: This column contains the order in which you think the improvements should/ can be made, after taking account of all the other factors in the improvements Schedule. The following process was used to reach the priorities given in Column 8: Are there any improvements with high health priority that can be

made easily and at little cost?Yes: #1 – give it top priority.

Are there any other improvements that can be made easily and at little cost?Yes: #5 – give it priority 2.

Are there other improvements of high health priority?Yes: #2 – this improvement cannot be made immediately because of its cost, but work can start on preparing the case for funding from the Ministry of Education. Give it priority 3.

Are there any remaining improvements?Yes: #3 and #4 – #3 is of higher health importance, and although #4 is easy to do and costs little, it cannot be done before #3. #3 and #4 therefore have priorities 4 and 5 respectively.

In situations where there is an Improvement of high health importance needed, it should be given a high priority and carried out as soon as possible, even if its cost is high. In the Greendell School example, although Improvement #2 (high health importance; high cost) is not given top overall priority, work can start on it at about the same time that work starts on the two higher ranked improvements.

Column 9: This column can be used to provide notes about an improvement where needed.


Action timetableAction Completion date Person

responsibleImproveme

nt completed

Meet with everybody who has a responsibility in this timetable to discuss and agree on what has to be done, and ensure they have a copy of the Action Timetable.

4 Feb 2002 Head Teacher

Contact public health service to arrange a visit by an HPO to train the caretaker in taking samples.

7 Feb 2002 Head Teacher

PTA meet to arrange working bee to cut back trees.

13 Feb 2002 PTA Chairperson

Working bee to cut back trees. 23 Feb 2002 PTA Chairperson 1

HPO visit to talk to caretaker and a teaching member of staff about sampling and to demonstrate how and where to sample.

4 Mar 2002 Head Teacher 5

Prepare a case to the Ministry of Education for funding for up-grade or purchase of a new UV disinfection unit.

29 Mar 2002 Head Teacher

Decide whether trees need to be pruned again, and if so ask the PTA to arrange a working bee. (This needs to be done each year.)

7 Feb 2003 Caretaker

Contact an engineering firm to arrange for them to visit the storage tanks, make measurements and manufacture new hatches to meet requirements.

15 Mar 2003 Caretaker

Have new hatches fitted. 17 May 2003 Caretaker 3

Purchase padlocks, fit to hatches, and lock.

20 May 2003 Caretaker 4

Obtain, and have installed new UV unit, or modification of existing unit.

Date cannot be fixed until reply from Ministry of

Education received.

Notes on the Action Timetable Actions in the timetable should include the smaller steps needed to

complete each improvement. This helps all those involved in their planning. (More detail may be required than given in the example.)

It is important that once the person with overall responsibility for the water supply has drawn up a draft timetable, there is a meeting to discuss what has to be done, how it should be done, and, if responsibility is not part of the job description, to check that those people who have been given responsibilities are prepared to accept them.


The last column in the table is included to help identify when each of the improvements contained in the Improvements Schedule has been completed.

All improvements from the Improvements Schedule should be included in the table, even if it is not possible to fix a completion date. This helps to ensure that these improvements are not overlooked.


Regular Checks and Maintenance SchedulesThe following table summarises checks that are carried out on the Greendell School water supply, how often they need to be made and who is responsible for them.

Regular checksCheck Details How often Responsibilit

y

1 Levels of germs (E. coli)

Take samples directly after treatment, and from the reticulation

Check the Drinking-Water Standards for New Zealand for details, or get advice from an HPO if needed

Monthly Caretaker

2 Tree growth Trees overhanging the roof Annually Caretaker

3 State of roof and guttering

Animal/bird droppings State of repair of roof Deposits (eg from chimneys) Unexpected objects (vandalism)

Quarterly (once every three months)

Caretaker

4 Tank (external and internal)

Mesh and grills displaced or missing so animals can get into the tank

Signs of vandalism Build up of sediment Water levels (warning of water

shortage)

MonthlyAnnually (sediment)

Caretaker

5 Appearance of the water

Cloudy or discoloured Daily All staff

6 Difference between the filter’s inlet and outlet pressures

Low difference means a filter problem

Daily Caretaker

7 Minimum water temperature

Poor UV disinfection at low temperature

Daily during winter

Caretaker

8 Parts of the reticulation that might be easily damaged

Signs of damage Daily (while moving around the school)

Caretaker

9 New situations that might lead to water being sucked back into the drinking-water supply

Annual Caretaker


Check Details How often Responsibility

10 Water pressure at taps

Lower pressure than usual Daily Caretaker

A number of the daily checks noted in the table can be made by any staff during their movements about the school each day, and any concerns passed on to the caretakers.

A log book is to be kept of all checks that are made (not necessary for the daily checks). This log should record any problems that are found (including those found during daily checks), and what corrective actions were taken.

The following table summarises maintenance schedules that need to be followed.

Maintenance schedulesSchedule Responsibility

1 Filter (including replacement) – follow manufacturer’s instructions

Caretaker

2 UV disinfection unit – follow manufacturer’s instructions Caretaker

A log book is to be kept to record any maintenance undertaken, including any work carried out on the reticulation system by a properly qualified plumber. The manufacturer’s maintenance instructions must be filed so that they can be easily found.

Notes on checks and maintenance schedules These checks and schedules are obtained from the Risk Information

Table. Summary of them in one section makes it clear to those using the

plan, and those assessing the plan, which checks and maintenance work need to be undertaken.


Contingency PlansThe following set of Contingency Plans are guides to what to do in case an event occurs despite preventive measures or corrective actions to stop it.

If there are difficulties in deciding how serious the event is, contact the local Medical Officer of Health (MOH).

Event – Roof contaminated by spraydrift or overspraying

Indicators: Spraydrift or overspraying reported. Noticeable taste or odour. Test results. Reported illness in the community.

Required actions:

Stop using the water. Find another source of drinking water until water of acceptable quality can again be supplied.

Identify the person or organisation doing the spraying, and if possible, the product used. Inform the MOH.

Drain contents of tank. Disconnect down pipe from tank. Clean roof and tank. Reconnect the down pipe to the tank. Check that no more chemical is getting into the

water by having the water tested again after the next rain, BEFORE using the water for drinking.

Record details of incident and provide ESR with this information for entry into its spray drift database – Driftnet.

Modify your water safety plan if necessary.

Responsibility:

Head teacher.


Event – Volcanic activity leading to ash fall on the roof

Indicators: Media reports of an eruption. Ash fall in area.

Required actions:

Disconnect down-pipe from tank. Normal range of conductivity values need to be

known before the event. Get help from a health protection officer from the district health board in getting these measurements (and for later measurements noted below).

Check quality of tank water through conductivity and pH tests.

If conductivity value is not elevated and pH is above 5, continue use of tank water. If conductivity has increased (estimated increase of 5–10 mS/m) or pH is depressed below 5, provide another source of potable water until water of acceptable quality can again be supplied.

When ash fall is complete, clean roof surface, guttering and down pipe, plus tank if necessary.

Have water samples taken to check for raised levels if heavy metals, and other chemicals of possible concern.

Modify water safety plan if necessary.

Responsibility:

Head teacher

Event – Water shortage

Indicators: No rain. Water level in the tank is low. Increased levels of turbidity as water is drawn from

lower levels of tank.


Required actions:

Provide another source of potable water until water of acceptable quality can again be supplied.

Find ways of reducing water usage. Identify the reason for the lack of water. The

obvious is lack of rain, but there may also be loss of water because of leaks.

If changes in weather patterns are likely to cause shortages of water often, install an additional or bigger tank, or find a supplementary or new source.

Modify water safety plan if necessary.

Responsibility:

Head teacher.

Event – Contamination enters the reticulation

Indicators: The water is cloudy, or the cloudiness is changeable.

In 100 ml samples of water from the reticulation, E. coli is continually found or is present at levels more than 10 per 100 mL.

People using the water complain of its taste and smell and of getting sick.

Required actions:

Follow the actions given in Figure 3.3 of the DWSNZ:2000.

Find out the cause of the contamination, and fix the problem.

Record what went wrong and why, and what you have done to overcome the problems.

Modify your water safety plan if necessary.

Responsibility:

Head teacher


Water Safety Plan Performance AssessmentEach year this plan is to be checked to make sure it is effective. This is done by: checking the water quality that has been shown by the monitoring

done for compliance with the Drinking-Water Standards for New Zealand

seeing whether any problems have been found during checks (these should be easily done by checking the log book that is kept).

If germs have been found in the water, or the checks have shown there to be problems, the plan needs to be changed to show: any new causes that have been found new preventive measures for existing causes, or to deal with any

new causes any changes to how often checks should be made (experience may

show the need for changes) any new Improvements needed.

Each year the Improvements Schedule and Action Timetable will need to be updated, because a number of improvements may have been made, and new ones may need to be added.

If there have been any changes to the supply, such as new treatment, changes to the roofs, new events should be added to the Risk Information Table.

If a Contingency Plan has been used, any improvements to the Contingency Plan should be made.

The head teacher has responsibility for reviewing how well the plan is working and making the changes necessary.


ReportingThe head teacher has responsibility for preparing a brief annual report on the water supply and the risk management of the supply to the Board of Trustees, the PTA and possibly the Ministry of Education if this is needed. This report should include the following information: Has the supply complied with the Drinking-Water Standards for

New Zealand (shown by the germ monitoring, and any chemical monitoring required by the Ministry of Health)?

If it has not complied, what was the reason and what is being done to overcome the problem?

How well is the timetable for making necessary improvements to the water supply being followed?

The District Health Board will also require a record of monitoring results to ensure the supply is complying with the Drinking-Water Standards for New Zealand.


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