Event: NOT ENOUGH SOURCE WATER AVAILABLE FOR ABSTRACTION Hazards: Germs and chemicals that get into the water because of low system pressure; hazards associated with poor hygiene. Level of risk: High P1.4.1.1 Drought. Start water conservation measures as soon as water shortage becomes likely. Plan the development and use of the source, and the need to identify and develop new sources, based on flow records of the spring. Water demand. Source usage rate. System pressure. Drop in system pressure. Customer complaints about low pressure. Prepare new resource consent application. Find new sources. Increase storage capacity. Partially close valves through the network to equalise pressures. P1.4.1.2 Resource consent limitations. Negotiate new resource consents. Water demand. Source usage rate. System pressure. Drop in system pressure. Customer complaints about low pressure. Find new sources. Increase storage capacity. Event: CONTAMINATION GETS INTO THE SPRING BOX Possible hazards: Germs and chemicals. Level of risk: High P1.4.2.1 Heavy rain leading to high levels of turbidity and organic matter. Install upstream cut-off drains to minimise contamination from run-off. Ensure spring box is covered, and constructed so that water cannot enter through manholes. Raw water: turbidity, suspended solids, quality. Non-compliance with DWSNZ: 2000 particularly turbidity, and E. coli counts. Increased filter backwash frequency (if filtering). Difficulty in achieving free available chlorine residual in treated water (if chlorinating). Spring box not covered. Review options. Review alternative source options. P1.4.2.2 Observed or known contamination in area of spring. Fence off abstraction area, and undertake regular inspection and repair. Increase chlorine residual in treated water. Event: CONTAMINATION OF THE AQUIFER (the source) Possible hazards: Germs and chemical determinands appropriate to contamination sources. Level of risk: High
P1.4.3.1 Contamination sources (eg, septic tanks, chemical sources) in aquifer recharge zone. Identify potential sources of contamination when source is selected (see Guide S1.1). Monitor changes in land use (including urban developments) and the potential for contamination they create, once the source is in use. Restrict activities in the aquifer recharge zone that may contaminate the water (see S1 Guide series). Gather information about the vulnerability of the aquifer before undertaking development. quality. Chemicals that the potential contamination source is likely to produce. No survey of potential sources of contamination undertaken. No aquifer tests carried out. No system in place for obtaining information about changing land use. Add treatment processes to remove identified contaminants. Instigate system for gathering information land use changes. Event: TOO LITTLE WATER CAN BE DRAWN FROM THE SPRING TO MEET DEMAND Possible hazards: Germs and chemicals that get into the water because of low system pressure; hazards associated with poor hygiene. Level of risk: High1 P1.4.4.1 Screens damaged or clogged with organic matter. Regular inspection and cleaning of screens should be intensified during times of flood (sediment) and under low flow conditions (algae, weed slimes). Flow (from intake). Reduced flow. Biological growths on screens. Modify intake. P1.4.4.2 Screens clogged with iron or calcium deposits. Regular programme of inspection of screens. This should be intensified during times of low flow conditions. Flow (from intake). Reduced flow. Scale build-up on leaking couplings, pipe joints etc. Change screen pore or slot size. P1.4.4.3 Intake and screen clogged with debris – common problem with coffer dam type intakes. Regular programme of inspection and cleaning of dam with increased frequency during autumn. Ensure there is no vegetation overhanging the dam. Flow (from intake). Reduced flow. Vegetation floating in the water. Investigate covering the seepage area.