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 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 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 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 2000 not followed. (If supply is found to be treatment to ensure microbiological quality will be required). Initiate groundwater security determination.
protection area, so that submissions can be lodged, as appropriate. No alteration to proposed location of source abstraction when future developments are to present risks to water quality. Lack of awareness of land use changes. Planned management strategy of the not followed. 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. 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 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 of change of water quality how water quality is affected by season. Causes Preventive measures Checking preventive measures Corrective action What to check 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. 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 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.