4 The high level of risk results when there is a severe lack of water. High sediment floods can cause problems for a gallery because packed gravel beds become blocked. Preventive measures Checking preventive measures Corrective action Causes What to check Signs that action is needed Event: INFILTRATION GALLERY PRODUCES LESS WATER THAN IT WAS DESIGNED TO (cont’d) P1.1.5.3 Avoid planting trees Remove trees near the gallery. already Gallery present, and clogged by determine tree roots. appropriate method for killing roots. Event: TOO LITTLE WATER CAN BE DRAWN FROM THE INTAKE 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: High5 P1.1.6.1 Regular inspection State of Reduced flow. Modify intake and cleaning of intakes. to protect Screens Elevated algal screens, intensified against damaged or Treatment count. during times of flood. damage, and clogged. plant flow reduce Limit nutrient input meters. likelihood of into the raw water to Algal counts in clogging. reduce clogging by river. algae and weed under Implement low-flow conditions. plan to reduce nutrient input Booms and screens to into source. trap weed/algae. P1.1.6.2 Regular preventive Flows (from Failure of Review maintenance, as intake). significant maintenance Failure of the required by the componentry. and inspection intake due to Inspection conditions, and schedule. mechanical or records. No water. manufacturers’ structural Preventive Alarm specifications: failure. maintenance activated. lubrication, log. component replacement, exercise valves. Regular inspections of intake. Telemetric alarm for low flows from the intake. P1.1.6.3 Intake inspections, Flood levels. No water. Consider regularly and directly alternative Catastrophic Flows (from Reduced flow. after floods etc, with source. failure (eg, intake). Alarm follow-up action if flood, slips or Review the Inspection activated. required for existing options for records. protection (eg, bankside gabions, piling, damage). storage. screens and grates, Evaluate etc). existing Telemetric alarm for protection low flows from the system. intake. 5 The level of risk will probably increase the lower the flow of the water is. Preventive measures Checking preventive measures Corrective action Causes What to check Signs that action is needed
4 The high level of risk results when there is a severe lack of water. High sediment floods can cause problems for a gallery because packed gravel beds become blocked. Causes Preventive measures Checking preventive measures Corrective action What to check Signs that action is needed Event: INFILTRATION GALLERY PRODUCES LESS WATER THAN IT WAS DESIGNED TO (cont’d) P1.1.5.3 Gallery clogged by tree roots. Avoid planting trees near the gallery. Remove trees already present, and determine appropriate method for killing roots. Event: TOO LITTLE WATER CAN BE DRAWN FROM THE INTAKE 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: High5 P1.1.6.1 Screens damaged or clogged. Regular inspection and cleaning of screens, intensified during times of flood. Limit nutrient input into the raw water to reduce clogging by algae and weed under low-flow conditions. Booms and screens to trap weed/algae. State of intakes. Treatment plant flow meters. Algal counts in river. Reduced flow. Elevated algal count. Modify intake to protect against damage, and reduce likelihood of clogging. Implement plan to reduce nutrient input into source. P1.1.6.2 Failure of the intake due to mechanical or structural failure. Regular preventive maintenance, as required by the conditions, and manufacturers’ specifications: lubrication, component replacement, exercise valves. Regular inspections of intake. Telemetric alarm for low flows from the intake. Flows (from intake). Inspection records. Preventive maintenance log. Failure of significant componentry. No water. Alarm activated. Review maintenance and inspection schedule. P1.1.6.3 Catastrophic failure (eg, flood, slips or damage). Intake inspections, regularly and directly after floods etc, with follow-up action if required for existing protection (eg, gabions, piling, screens and grates, etc). Telemetric alarm for low flows from the intake. Flood levels. Flows (from intake). Inspection records. No water. Reduced flow. Alarm activated. Consider alternative source. Review the options for bankside storage. Evaluate existing protection system. 5 The level of risk will probably increase the lower the flow of the water is. Causes Preventive measures Checking preventive measures Corrective action What to check Signs that action is needed