Pump Emergency Storage Estimation¶
The 'Pump emergency storage estimation' simulations allow estimating the time and volume available prior to an overflow at a wastewater pump station asset in the event of system failure.
Sewer overflows from sewage treatment systems are considered critical. In the event of a failure at the pumping station, sufficient storage time and volume is required by the operations staff to respond and address the cause of failure, before an overflow actually occurs. Pump station failure may occur for a number of reasons including failure of power supply, switchboards, number of pumps or failure of the pump station pipework or rising main. Emergency storage is considered to include both wet well storage and storage in upstream gravity sewers.
This special analysis helps knowing the time available before overflow will occur to the environment, e.g. in order to develop a management and operations staff action plan.
For new pump stations, a minimum of 4 hours storage at Average Dry Weather Flow conditions shall usually be provided between Alarm Level and actual overflow level. Systems draining to waters deemed sensitive normally require more storage, e.g. up to 8 hours storage.
Options to be considered for emergency storage for new pump stations, in order of preference, may include:
- Use of larger diameter wet wells
- Online storage in larger diameter gravity sewers
- Use of larger diameter manholes.
Offline storage structures shall not be used for new pump stations.
Where an existing pump station is to be upgraded (including the construction of a new pump station wet well to replace part or all of an existing pump station), the amount of storage required will be the same as for new stations.
Options to be considered for designing emergency storage for existing pump stations, in order of preference, may include:
- Use of larger diameter wet wells
- Inline storage in larger diameter gravity sewers
- Use of larger diameter manholes
- Offline gravity sewers
- Offline storage tanks.