Water Safety Plan Guide: Roof Water Sources · Web viewWater Safety Plan Guide:iii Version 1, January 2014 Roof Water Sources Ref S1.2 Water Safety Plan Guide:9 Version 1, January

Water Safety Plan Guide

Roof Water SourcesVersion 1, Ref S1.2

January 2014

Citation: Ministry of Health. 2014. Water Safety Plan Guide: Roof Water Sources, Version 1, ref s1.2. Wellington: Ministry

of Health.

Published in January 2014 by the Ministry of Health

PO Box 5013, Wellington, New Zealand

ISBN: 978-0-478-42702-8 (print)ISBN: 978-0-478-42703-5 (online)

Previously published in 2001 as Public Health Risk Management Plan Guide: Roof Water Sources, Version 1, ref

s1.2. 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

IntroductionRisk SummaryRisk Information TableContingency PlansWater Safety Plan Performance Assessment

iv [Title]

Ref S1.2 Water Safety Plan Guide: vVersion 1, January 2014 Roof Water Sources

IntroductionRainwater is used as raw water by supplies with roof catchment systems. This Guide is concerned with the collection of rainwater from the roof, its transfer to storage and its storage.

If an event occurs with a roof catchment (ie, contaminants get into the rainwater during collection or storage), the following could happen: If animal or bird excrement, or air-borne chemical contamination, is

carried onto the roof or guttering, germs or the chemicals can cause sickness

If material is dissolved from the roof, flashings, guttering or downpipes, heavy metals can cause sickness (rainwater is corrosive)

If animal or bird excrement or chemicals get into the storage tank, germs or chemicals can cause sickness

If volcanic ash falls on the roof, chemical contaminants can cause sickness

If the supply of water runs out, poor hygiene can cause sickness.

The maintenance of a roof catchment can present risks to health. These are acknowledged, but are not discussed further as such risks are the subject of health and safety in employment legislation.

The roof catchment and storage, and the risks associated with them, cannot be viewed in isolation. The quality of the water reaching the consumer could also be influenced by the following, if they are used: filtration, which can remove particles and some types of germs (see

the P6 series Guide for the filter used in your supply) disinfection, which will kill some types of germs (see the P7 series

Guide for the disinfection method used in your supply).

To make the document more self-contained for small water suppliers, this Guide includes information about water storage. Guide D1 discusses storage more fully and may help in understanding risks associated with storage.

Ref S1.2 Water Safety Plan Guide: 1Version 1, January 2014 Roof Water Sources

Risk SummaryThe event creating the greatest risk involved in operating a roof catchment is animal or bird excrement, or chemical contaminants, getting onto the roof (see S1.2.1).

The most important preventive measures are: keep the roof and guttering clear of overhanging branches

(S1.2.1.1) regularly inspect and clean the roof and guttering (S1.2.1.1–2) disinfect the water (S1.2.1.1–2).

(References in parentheses are to the Risk Information Table.)

2 Water Safety Plan Guide: Ref S1.2Roof Water Sources Version 1, January 2014

Risk Information TableReliable 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; council – regional/district council or unitary authority.

Causes Preventive measures

Checking preventive measures Corrective action

What to check Signs that action is needed

Event: EXCREMENT AND CHEMICAL CONTAMINANTS CARRIED ONTO ROOF OR INTO GUTTERINGPossible hazards: Germs; herbicides, pesticides, other chemical contaminants that may be airborne.Level of risk: High1

S1.2.1.1Overgrown trees May cause

bird life, possums or rotting vegetation to contaminate the roof catchment area.

Water dripping off branches onto the roof may carry contaminants.

Dead animals may fall into the guttering.

Tree surgery. Clean out

guttering. Provide a grate

over the downpipe-gutter connection, or over the whole guttering, to limit entry of vegetation into the tank.

Check tree growth at least annually.

Check guttering at least annually.

Microbiological quality directly after rain.

Overgrown trees.

Dirty guttering.

E. coli is detected in 100 ml sample.

Tree surgery. Disinfect water

in tank or treat with UV at point of use.

Disconnect downpipe from tank and clean guttering.

Disinfect water in tank (1 mg/L of chlorine for clean water,* possibly up to 5 mg/L if water is poor quality) or treat with UV at point of use.





S1.2.1.2Faecal contamination 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, such as not feeding them and ensuring that rubbish disposal is secure.

Microbiological quality.

Quarterly inspection of roof and guttering for faecal contamination.

Faecal contamination on roof or in guttering.


Disconnect downpipe from tank and clean roof and guttering.

Disinfect water in tank (1 mg/L of chlorine for clean water,* possibly up to 5 mg/L if water is poor quality) or treat with UV at point of use.

* About 1 teaspoon per 2L bucket.1 It is primarily the microbiological hazards introduced into the water by this event, rather than

the chemical, that give it a high level of risk. However, overspraying events will create a high risk due to chemical determinands.




Event: EXCREMENT AND CHEMICAL CONTAMINANTS CARRIED ONTO ROOF OR INTO GUTTERING cont’d

S1.2.1.3Industrial, agricultural or domestic discharges to air (including aerial spraying) settle out on roof.

Record incidents of roof contamination from the air, and seek assistance from the council to reduce these (discharge consents).

Consider using an alternative source (less affected by aerial discharges).

Use first-flush diverter or disconnect downpipe, before first rain after possible contamination episode.

Ensure your chimney stack is long enough that material from the fire will not settle on the roof.

Sample for possible contaminants from all nearby emissions – seek advice on likely contaminants.

Obtain details of all nearby agrichemical applications.

Water contains contaminants at concentrations more than 50% of their MAV.

Noticeable taste in the water.

Algal growths if fertilisers have contaminated the roof.

Visible deposits of ash/soot on the roof.

Seek action from the council to reduce discharges to air if from a small number of sources.

Make use of a new source unaffected by discharges to air (eg, groundwater).

Locate alternative source.

Install a first-flush diverter.

Lengthen chimney.

Phenols or lead in water.

Clean acid glaze from slow-burning fire smoke off chimney.





S1.2.1.4Contamination of roof and guttering during spraying to protect roof timbers against borer and other insects, or proofing against spiders.

Ensure that the contractor is aware that the roof is used to collect drinking-water, and that overspraying must be avoided.

Obtain a guarantee from the contractor that persistent organochlorine pesticides will not be used.

Nature of pesticides used by contractors.

Pesticides in water following treatment of roof timbers, if there is concern about the nature of the pesticides used, and the way in which they were used.

Use of persistent organochlorine insecticides by contractor.

Knowledge of overspraying events.

Water contains pesticides at concentrations more than 50% of their MAV.2

Use different contractor.

Use first-flush diverted or disconnect downpipe, before first rain after treatment of the roof.

Decontaminate the roof.

Use alternative supply until decontamination is complete.

2 The risk associated with this event will depend on location within the country.




Event: EXCREMENT AND CHEMICAL CONTAMINANTS CARRIED ONTO ROOF OR INTO GUTTERING cont’d

S1.2.1.5Vandalism/ sabotage.

Ensure access to the roof is made as difficult as possible, by removing such things as ladders.

Inspect the roof regularly for deliberately introduced contaminant sources (eg, bags of chemicals).

Check the roof for unexpected objects on it, and the area surrounding the building for objects that may make access to the roof easier.

Evidence of unauthorised access having been gained to the roof.

Eliminate means by which access to the roof was gained.

Remove contaminant source, disconnect downpipe and wash down.

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





S1.2.2.1Lead-containing materials (paint, nails or flashing) used in roof construction; guttering constructed from corrodible material (eg, copper).

Use lead-free materials on the roof (paints, flashings, nails).

Keep roof surface well maintained.

Use plastic guttering.

Inspect condition of the roof surface at least annually.

Test for heavy metals in roof paint (one-off test probably sufficient).

Heavy metals in the water if there is a likely source of them on the roof.

Roof surface in poor condition and needs repainting or replacing.

Leaded paint test on roof paint is positive.

Heavy metal concentrations in the water are more than 50% of their MAV.

Cases of lead (or other heavy metal) poisoning, but be aware that such cases may have other causes.

Replace inappropriate materials.

Repaint roof, or replace roof.

Replace guttering.

Event: CONTAMINATION OF THE WATER WHILE IN THE STORAGE TANKPossible hazards: Germs; plasticisers (di (2-ethylhexyl) phthalate), possible reduced disinfection efficacy by chlorine because of high pH.Level of risk: High

S1.2.3.1Animal or human access to storage tank (see S1.2.3.5).

Ensure the storage is covered.

Install mesh on vents, overflow, etc.

Undertake regular tank inspections (monthly).

For wooden tanks:– install metal

band around wooden tanks to prevent animal access from ground level– remove

vegetation near tanks– install internal

liner for tank roof.

Monthly tank inspection.



Dead animals found in tank.

Mesh/grills disturbed by animals to get access.

Unpleasant taste and odour.

Water turbid.

Disinfect tank (1 mg/L of chlorine for clean water, possibly up to 5 mg/L if water is poor quality) depending on water quality.

Replace or provide mesh where necessary.

Prepare tank inspection schedule.





S1.2.3.2Accumulation of sediment in tank.

Undertake regular (annual) cleaning of tank.

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 access.

Unpleasant taste and odour.

Water turbid.

Instigate inspection and cleaning programme.

Install a second tank.

S1.2.3.3Water stagnant in plastic tank for too long.

Ensure the material chosen for the tank is suitable for drinking-water purposes.

Locate tank in a shaded area.

Position inlet into the tank near the bottom to ensure good mixing and avoid stagnant zones near the tank bottom.

Taste. Sample for

phthalates (plasticisers).

Plastic taste. Di (2-

ethylhexyl) phthalate concentration is more then 50% of its MAV2.

Reduce tank size for faster turnaround of water.

Flush tank a number of times on first filling.

Relocate tank to area that is cooler.

Relocate inlet to tank.

S1.2.3.4Dissolution of lime from new concrete tank (this problem should reduce as the tank ages).

Line the tank. Increase

buffering capacity of the water (eg, addition of sodium bicarbonate).

pH. pH above the guideline range (7.0-8.5).

Add sodium bicarbonate until pH reaches an acceptable level.

Event: CONTAMINATION OF THE WATER WHILE IN THE STORAGE TANK cont’d

S1.2.3.5Vandalism/ sabotage.

Restrict access to tanks (fences, locked hatches).

Regular inspection of tanks for evidence of unauthorised access.

Evidence of unauthorised access having been gained to the tank.

Fence tank, or provide lockable hatches.





Event: VOLCANIC ASH FALL ON ROOF2

Possible hazards: Arsenic, fluoride, and metals.Level of risk: Low

S1.2.4.1Volcanic eruption results in ash fall (pyroclastic fall).

Disconnect downpipe into tank as soon as possible after eruption.

Use conductivity test to determine whether tank water is fit to drink.

If tank water is not fit to drink, empty and clean out tank when all ash falls have ceased.

Clean roof, guttering and downpipe.

Conductivity. Fluoride,

arsenic, other metals suspected of having elevated concentrations.

Chemical contaminants still present at concentrations greater than 50% of their MAV.

Conductivity of the water is5–10 mS/m higher than normal.

Tank and roof not cleaned sufficiently following ash fall to ensure contaminants are removed from the water.

Repeat cleaning procedure until analytical results for water demonstrate that contaminants are present at concentrations less than 50% of their MAV.

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

S1.2.5.1Lack of rainfall combined with insufficient storage, excessive use, leak in tank, or breach in guttering.

Ensure tank size is adequate. (Use information about annual rainfall levels and number of people using supply to determine size of tank required.)

Ensure strength of guttering is adequate for wind and snowfall conditions.

Establish an inspection programme to check guttering and tank.

Conservation of water.

Water level in tank.

Rate of water use.

Regular (monthly) inspection of tank and guttering.

Water runs out frequently.

Water levels low.

Evidence of water leaking from tank.

New tank. New or

additional source.

Repair tank and/or guttering.

Start water conservation measures.

2 The risk associated with this event will depend on location within the country.


Contingency PlansIf 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 – Roof contaminated by spraydrift or overspraying

Indicators: Spraydrift or overspraying reported, noticeable taste or odour or analytical results.

Reported illness in the community.

Required actions:

Identify sprayer and product used, and inform relevant authorities, including MOH.

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

Disconnect down pipe from tank. Clean roof and tank. Confirm absence of chemical from water, by

chemical testing, after next rain. Submit details to Driftnet (ESR). Record details of incident. Modify water safety plan (formerly known as a

public health risk management plan, PHRMP) if necessary.

Responsibility:

Manager designated responsible for the water supply.


Event – Volcanic activity leading to ash fall on the roof

Indicators: Media coverage of eruption. Ash fall in area.

Required actions:

Normal range of conductivity values need to be known.

Disconnect down-pipe from tank. 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 elevated (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.

Conduct confirmation test of water to ensure that no elevated concentrations of heavy metals are present.

Modify water safety plan if necessary.

Responsibility:


Event – Water shortage

Indicators: No water, or tank level 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.

Identify the reason for the lack of water. To avoid this happening regularly, install an

additional or bigger tank, or find a supplementary or new source.

Modify water safety plan if necessary.

Responsibility:



Water Safety Plan Performance AssessmentTo 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:

Corrosion metals E. coli.Follow the protocols set out in DWSNZ:2000.

How often: For the monitoring frequencies for corrosion metals and E. coli measurements see DWSNZ:2000.

What to do with the results:

Results need to be recorded to meet legislative requirements or to allow water safety plan performance assessment. The WINZ database is good for this.

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 roof catchments.

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 catchment system are recognised in the plan.

Responsibility: Manager designated responsible for the water supply.


Documents

Water Safety Plan Guide: Roof Water Sources · Web viewWater Safety Plan Guide:iii Version 1, January 2014 Roof Water Sources Ref S1.2 Water Safety Plan Guide:9 Version 1, January