Microburst Software
Gross pollutant trap
Gross Pollutant Traps (GPT’s) capture litter and debris that is washed into the stormwater system. GPT’s vary in their form and function, ranging from trash racks to underground proprietary devices. The type of GPT will govern the litter that is being removed from the stormwater. For example, trash racks will only be effective at removing large litter and debris while modern centrifugal GPT’s can effectively remove litter, coarse sediment, floating litter and hydrocarbons as well as some finer particles and pollutants.
A GPT will usually consist of:
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A diversion chamber containing a weir to control inflows and allow bypass of high flows
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A screening mechanism
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Sediment storage sump or basket
Most proprietary GPTs will be supplied with a maintenance manual or program that specify required tasks and frequency. It is recommended to obtain the relevant program before undertaking any condition inspections or maintenance of a proprietary GPT system.
Some typical gross pollutant traps include the following (this is not a complete or exhaustive list):
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Standard GPT
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Ecosol RSF Filter
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AGLASS GPT
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HumeGuard
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Rocla CleansAll
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Q-Guard by James Hardie
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Vortex GPT
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Rocla CDS
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Rocla Downstream Defender
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Rocla First Defence
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Humeceptor
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SPEL Stormceptor
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Pit inserts
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Stormwater 360 Enviropod
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SPEL StormSack
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A centrifugal Rocla CDS GPT (Left) and a linear HumeGard GPT (Right) illustrating diversion, screen and sediment sump
Key monitoring considerations
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GPTs fill up with litter and sediment over time and need cleaning out. Hence, the pollutant storage area must be inspected to check how full the GPT is.
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GPTs are designed to trap litter in specified storage areas and any build-up/blockage of pollutants at the inlet or outlet can compromise the performance of the system.
Inspection tasks
Inspection items and monitoring methods are specified in the GPT inspection checklist table and are accompanied by an asset scoring chart defining the performance of assets. The following inspection checklist can be used by property owners and contractors.
Expertise required
It may be possible for property owners to undertake condition inspection of small litter baskets in pits and trash racks where they can be safely accessed for inspection. However, many larger proprietary GPTs (e.g. centrifugal systems) typically require specialised equipment to access for inspection and maintenance. For these systems, property owners or owners’ corporations will need to engage suitably qualified contractors to undertake the annual asset condition inspection and to carry out any required maintenance.