Three Waters Integration
- Strategic planning
- Recognises inter-relationships
- Integrates financial planning
Water Supply - Sources
- Groundwater bores
- Reservoirs
- Stream/river offtakes
- Lakes
- De-salination
- Roof water
- Process water reuse
Water Supply - Christchurch
- Water is delivered in water mains by electrically driven pumps
- Water pressure is maintained by continually supplying water to the level of the reservoirs on the hills
- Water is taken from wells and pumped into pipe network
- Water supply network is controlled by a central room
- Network of pipes ensures number of households affected by stopped water is minimal
Water Supply - Auckland
- Supplied from dams located in Hunua and Waitakere ranges
- Water flows by gravity in the city
Key Water Supply System Design Considerations
- Water quality: achieve minimum standard
- Hydraulic capacity - adequate for estimated use
- Structural strength of water system components to resist loads
- Fire supply: achieve standard
- Fit for purpose service life
- Seismic resistance
- Resist internal and external corrosion or degradation
- Optimal cost for asset life of 50yrs
- Capacity and ability to service future extensions and development
- Networking, redundancy and security of supply
Water Supply - Design Basis
The customer/user determines quantity and quality specification
- Domestic: well defined
User specific:
- Industrial, commercial, agricultural
Water Supply Rates - Residential NZ
- 30% baths and showers
- 30% toilet flushing
- 20% kitchen
- 20% laundry
- 180-250L per person per day (inside house)
- In summer average demand can be raised to 800L per day (inside and outside)
Commercial Water Use
Accommodation, multi-storey offices, and shopping centres were large commercial water consumers.
Major uses of water in these sub-sectors were:
- cooling
- bathrooms
- landscaping
Industrial Water Use
High water use:
- Food processing
- Beverages
- Textiles
- Semi-conductor
- Pulp and paper
Low water use:
- Warehouses
- Electrical goods manufacture
Institutional
The majority of large institution demands came from power stations, airports, and government accounts.
Hospital water uses generally include cooling, bathrooms and landscape irrigation
Design Flow and Pressures
Need to calculate
- Minimum water demand
- Peak Flow
- Fire water demand
Fire Supply
The provision of readily available sufficient water supply will affect the extent to which a firefighting resource and save life and property
Pipe Design - Hydraulic pressure/surge
Hydraulic pressure (transient flow) occurs when the flow of fluid in a pipeline is abruptly changed. Piping systems that use quick acting valves, or use pumps that start up or shut down rapidly, are susceptible to pressure transients (surges). These conditions can result in piping failure, damage to pumps, fittings, instrumentation, and other system components.
Network Design
- Commonly use models to assess combinations of pipe size, pressure and layouts
- Check ability to add future connections
- Looping to provide flow security
- Incorporate valves for maintenance/fault isolation
- Design pressures: check against proposed pipe type
- Rate pipes for 1.5 times operating pressure
Pipe Materials
- Ductile iron and steel
- PVC-U
- PE 80, PE 100
Typical Fittings
- Sluice Valves
- Backflow prevention
- Scour valves
- Air valves
- Thrust and anchor blocks
- meters
Two basic causes of backflow
1) A sudden drop in pipe pressure causing water to siphon back into system
2) Water supply is directly connected to equipment, such as a boiler or a private bore, which is at a higher pressure than the water supply system, forcing water into the supply system.
Construction Considerations
- Installation methods
- Minimum cover
- Backfill and bedding materials
- Crossings (roads, railways, waterways)
- Clearance to other services
- Future access
- Topographical and environmental considerations
Alernatives
- Grey-water reuse
- Rainwater tanks
(only for small scale)
Water Supply - Water Quality
- NZ Drinking Water Standards: requirements to be met in terms of raw and treated water
- Requirement for Water Supply Plan: needs to identify potential risks to supply
- Contains Maximum Allowable Values (MAV) for organic and inorganic contaminants within drinking water
Water Supply Considerations
Supply Risks:
- Climate effects
- Abstraction effects
- Water quality
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Consultation26
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Resource Management Act17
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Environment and Social Issues RMA16
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Environmental Effects and Assessment13
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Wastewater Collection Systems13
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Waste stabilisation Ponds or Oxidation Ponds9
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Energy Engineering17
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Water Supply21
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Stormwater21
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Project Scoping27
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Cost Estimation22
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A Contractor's Persepctive12
