P3.1.1 Inadequate raw water supply. Provide sufficient raw water storage to cover seasonal variations in source water availability, periods of untreatable raw water quality, maximum limits on consent for abstraction from the source, and losses through evaporation. Refer also to Guide S1.1 (Contingency Plan). Develop alternative sources that can be used when demand cannot be met. Encourage water conservation during periods when demand is likely to be high. Pre-treatment storage levels. Water consumption. Raw water storage levels unacceptably low. Need for water-use restrictions. No back-up water source available. Construct additional storage. Plan development of new sources. Water use restrictions. P3.1.2 Inability to transmit water from source to storage. See Guides P2 and P10. P3.1.3 Leak in storage. Carry out routine testing of storage for leaks. Change in storage level. Change in storage level does not equal water input minus water output (including evaporation). Fix leak. Event: INTRODUCTION OF CONTAMINATING MATERIAL INTO TANK OR RESERVOIR Possible hazards: Germs, arsenic, copper, chromium, iron; other health-significant determinands depending on the contaminant that has entered the water. Level of risk: Moderate P3.2.1 Access by humans (see also P3.2.2), animals or birds. Produce site inspection plans and reports For lakes/open reservoirs: ensure the storage is fenced restrict recreational use around and on lake/ reservoir. Site inspection plans and reports. Erect fence. treatment
animal or bird ingress. For tanks: ensure the storage is covered install mesh, grills, vents, etc undertake regular tank inspections document condition of mesh, grills, vents, tank liner (for gaps) etc and take action. storage. Replace damaged screens, etc. Instigate inspections. For wooden tanks: install metal band around wooden tanks to prevent access from ground level remove vegetation near install internal liner for tank roof. Prune or remove trees. P3.2.2 access, vandalism, or sabotage. Locked perimeter fence. Locked access towers and ladders. Locked hatches on tanks. Intruder alarm. Produce site inspection plans and reports. Site inspection and reports. Evidence of or damage. Determine how access was obtained and rectify shortcoming in security. P3.2.3 Leaching from, or corrosion of, construction materials. Specify materials certified for potable water use in tenders, and audit during construction, and during subsequent maintenance, against changes in standards. Use accredited contractors. For tanks using treated timber, install roof liner. Regular inspection of tanks. If roof is unlined – copper, chromium, or arsenic (especially heavy rain). Deterioration of water quality following new installation. Deterioration of water quality after rain. of copper, chromium or arsenic are more than 50% of their MAV. Replace substandard materials. Replace lid with more suitable material. Event: INTRODUCTION OF CONTAMINATING MATERIAL INTO TANK OR RESERVOIR cont’d P3.2.4 Entry of roof drainage. Specify and audit roof design: to drain from (not into) tank restrict access to roof top. Installation design. Annual roof inspection. Deterioration of water quality following rain. Repair leaky joints, cracks, or hatches promptly.