Water Sensitive
Urban Design

Back
to map

Edwardes Lake Gross Pollutant Trap

Edwardes Lake Park. Cutting across the pathway on the west side of the lake.

The Edwardes Lake Gross Pollutant Trap acts like a big sieve, screening out large pieces of litter and debris from stormwater flowing into Edwardes Lake and Edgars Creek.

The Edwardes Lake Gross Pollutant Trap (GPT) is located within the stormwater drainage system between the upstream reach of Edgars Creek and Edwardes Lake, in the suburb of Reservoir. Stormwater is rainwater that flows over hard surfaces such as roofs, roads, carparks and gutters in urban areas and drains into our local waterways. It can pick up and carry litter, silt, oil, chemicals and other pollutants with it.

The Edwardes Lake GPT is a relatively large GPT unit that works like a giant sieve to filter stormwater from a fairly large catchment. It helps to capture large pollutants like plastic bottles, cans, plastic bags and packaging; and organic debris such as sticks and leaves. This improves the quality of stormwater that enters Edwardes Lake and flows on into the downstream reach of Edgars Creek, which is a tributary (smaller waterway that leads into a larger one) of the Merri Creek.

GPTs are not able to capture smaller pollutants such as heavy metals, oils, chemicals or silt from stormwater, so they are best used as part of a stormwater treatment train. The Edwardes Lake GPT is located to receive water that has already been partly-treated by bioretention (natural filtering processes) in the Leamington Wetland sediment basin. Water screened by the GPT is released into Edwardes Lake for further bioretention treatment, before flowing on into the downstream reaches of the Edgars Creek.

Outcomes

Cleaner stormwater water entering Edwardes Lake and Edgars Creek

Project Description
The Edwardes Lake Park Gross Pollutant Trap (GPT) acts like a big sieve to stop debris and large pieces of litter such as plastic bottles and bags and from entering the lake and flowing on into Edgars Creek.

Catchment
Edgars Creek Catchment – Edgars Creek – a tributary of Merri Creek

Project details

PROJECT DETAILS

How the System Works

The Edwardes Lake GPT unit is situated underground, within the stormwater drainage system, but has an above-ground metal grate-style lid that allows it to be pumped out and cleaned regularly. It is made of heavy concrete and steel.

Water flows into the GPT via gravity from a stormwater pipe, and passes through a metal screen that catches any larger pieces of litter or debris (> 5mm).

Litter and debris removed by the screen is held in an underground sump (wet pit), which has to be emptied out regularly to keep the GPT working properly.

Once the stormwater entering the GPT has been filtered, it flows out of the unit via gravity, and enters Edwardes Lake. Water from the lake then flows into Edgars Creek which is a tributary of the Merri Creek.

The GPT cannot filter out smaller pollutants, such as silt, heavy metals, oils or chemicals, so it forms just one part of a stormwater treatment train. The Edgars Creek stormwater treatment train also includes the Leamington Wetlands and Edwardes Lake which help to filter out smaller pollutants using bioretention processes.

System Components

The Edwardes Lake GPT is just one component of a stormwater treatment train that includes wetlands and an overflow systems.

Inlet pipe: The GPT it situated within the underground stormwater drainage system. Water flows into it via an inlet pipe from the local stormwater system.

GPT Unit: The GPT unit is made of heavy concrete, with a large gauge (5mm) metal screen to filter the stormwater, and a sump to store any litter or debris caught by the screen. The system works using gravity, with water flowing through it in one direction. No pumping or electricity is required for the system to operate.

Outlet pipe: Filtered stormwater flows out of the GPT into Edwardes Lake. From there it eventually re-enters Edgars Creek and flows on into the Merri Creek.

Project Timeline

2002-2004 – Installation of the GPT at Edwardes Lake

Maintenance and Monitoring

Darebin City Council currently has 30 GPTS in place. It is estimated that $80,000 is needed each year to pump out all the litter and debris caught by the GPTs.

GPTs require regular maintenance to keep them doing their job. How regularly they are pumped out depends on the size of the GPT, the size of the catchment it receives stormwater from, and the design of the GPT unit.

The Edwardes Lake GPT is a relative large unit, but still requires regular maintenance to reduce the risk of blockage and flooding.

PROJECT BENEFITS

Benefits to the Community

The Edwardes Lake GPT is an underground water sensitive urban design (WSUD) feature. It has been located beneath the walking path the circles the lake – out of sight of the community. The grate-style lid that covers it makes it easy to service without interfering with the aesthetics of the park.

Without the GPT, a lot more decaying debris and litter would enter Edwardes Lake and Edgars Creek, polluting these waterways and making the surrounding landscape unpleasant for the community and visitors.

The GPT helps protect the lake and creek environments and encourages biodiversity (the range of plants and animals) in these areas, creating recreational and educational activities for the local community, such as wildlife spotting and birdwatching. Studies have shown that public open spaces in urban areas can increase levels of physical activity in the community and have mental health benefits, which can help to reduce healthcare costs (Parks Victoria, 2017).

Environmental Benefits

The Edwardes Lake GPT is surrounded by the Leamington Wetland and Edwardes Lake Park. This means there is an abundance of wildlife present in the area. Many native animals call the creeks and lakes of Darebin home – such as platypus, rakali (native water rat), frogs, fish (such as the common galaxias) and birds (such as the sacred kingfisher).

These plants and animals rely on clean and healthy waterways for survival. The Edwardes Lake GPT is a screening device that helps protect water quality and wildlife not only in this area, but all wildlife downstream that depend on clean water for survival.

ACKNOWLEDGEMENTS

Darebin City Council acknowledges the Wurundjeri people as the traditional owners and custodians of this land and pays respect to their Elders past and present.

Artwork infographics developed and supplied by City of Melbourne. For other examples of WSUD Urban stormwater treatment projects visit the City of Melbourne Urban Water interactive map here.