Unlike wastewater, stormwater isn't treated before flowing into creeks, rivers and oceans. We (and many councils) manage stormwater using stormwater quality improvement devices (SQIDs).

SQIDs are designed to catch solids so they can be removed from the water, such as:

• trash racks
• sediment traps
• litter booms
• constructed wetlands.

A gross pollutant trap is one of the devices used to trap litter and protect our  our waterways 

 

Stormwater Quality Improvement Devices, or SQIDs, are devices installed in our stormwater channels to catch pollutants. They come in various forms, including:

• Floating litter boom
• Gross pollutant trap
• Silt pit
• Trash rack

In the past 20 years, Sydney Water has installed over 70 SQIDs. These devices have helped remove over 35,000 cubic metres of litter and organic waste as well as 39,000 tonnes of sediment from stormwater before it reaches Sydney’s waterways.

Incorporating SQIDs into our stormwater network creates cleaner waterways, particularly downstream of the devices. This results in improved water quality and habitat for wildlife both in and around the waterways.

Floating Litter Boom

Floating litter booms fitted with buoyant polyethylene pipes are placed in waterways to gather floating debris, including litter and vegetation. Secured by chains connected to ground anchors or rider poles for canal setups, the booms often incorporate a one-way gate and a litter-catching basket to ensure pollutants stay trapped in the device. To extract the captured litter, our contractors use a grab truck with an outreach arm and clam shell attachment.

An example of a litter boom 

Underground SQUIDS

We use many types of underground SQIDS to capture pollutants these include:

• Gross Pollutant Traps

Continuous Deflection Separation (CDS) gross pollutant traps are designed to trap and retain various pollutants such as gross debris, litter, grit, sediments, and accompanying oils. Typically situated underground, stormwater from the channel is directed into the CDS unit before re-entering the channel. Our contractors use a vacuum truck or grab truck to clean the CDS and remove the captured pollutants.

• Silt Pits

Silt pits or sediment basins are designed to store sediment in a specific area rather than allowing it to travel through the channel. A low barrier allows stormwater to move downstream while blocking silt from travelling with it. Regular clearing of silt pits is required to ensure the silt does not overflow into the downstream channel.

Example of a Silt Pit

 

•  Trash Racks

Trash racks are barriers consisting of vertical or horizontal exclusion bars which catch litter and debris in stormwater channels while still allowing water to pass through. The litter is removed regularly by our contractors to avoid the channel being blocked by a build-up of debris.

Example of a Trash Rack

 

 

Stormwater transports items accumulated on solid surfaces such as roads, sidewalks, driveways, and roofs. As a result, the waste items and substances that end up being captured by our SQIDS include:

• Litter, such as plastic bottles, food packaging, and cigarette butts left on the streets.
• Oil and grease from vehicles.
• Soil, leaves, and twigs.
• Animal and bird droppings.
• Chemicals, including nutrients, resulting from activities like car washing.

In the last 5 years, Sydney Water has completed over 2000 cleans of the Gross Pollutant Traps and litter booms in our channels, removing roughly 10,000 cubic metres of rubbish and 5000 tonnes of sediment from the stormwater network.

The method used to clean SQIDs varies by type of device and access conditions. Litter booms are usually cleaned using a grab truck with an outreach arm. Trash racks are raked to remove litter and debris before transferring to a truck. Sediment basins and GPTs are usually cleaned using a truck fitted with vacuum equipment. During the vacuuming of GPTs and sediment basins, excess water is separated from the extracted solids and diverted into a nearby sewer. Pressure washing is undertaken during comprehensive cleaning to remove tough debris stuck to the SQIDs

SQIDs are cleaned and maintained at different frequencies based on factors such as the type of device, flow of the channel and land use of the area surrounding the channel. All of our SQIDs are placed on a cleaning routine with frequencies ranging from weekly to quarterly. In addition to routine cleans, some SQIDS undergo more comprehensive cleaning every 6 months to 2 years

The waste removed from our stormwater assets is sent to a recycling facility where it is separated into water content, recyclables, and general waste. The water is transferred to the wastewater network and the recyclable organic material is used in the farming and landscape industries. This process reduces landfill and extends the useful life of the processed materials, contributing to a circular economy.

Like all infrastructure, SQIDs have a limited service life. Along with regular wear and tear of the components that make up the devices, most SQIDs are subject to constant water pressure as they are situated directly in stormwater channels. Over time, parts will deteriorate and will require replacing. The volume of water and amount of debris flowing in stormwater channels can also vary over time due to changes in land use and other factors, and some SQIDs may need to be relocated, removed or replaced with a more suitable design as a result. It is also important to maintain the serviceability of our SQIDs to ensure our contractors are safe when cleaning the devices.

You can help us keep our waterways clean by:

• Throwing all rubbish in the bin.
• Washing cars on the grass instead of hard surfaces so detergents wash into the soil rather than stormwater drains.
• Sweeping leaves, dirt and rubbish away from gutters.
• Making sure your gardens have good borders so soil doesn’t wash into stormwater drains.
• Putting grass clippings in the compost bin or on the garden.
• Picking up your pet’s droppings and putting them in a bin.
• Disposing of chemicals, pesticides, paints and oils using your local council's chemical clean out services.

If you see something that could be hazardous to the community or environment, call 13 20 90 to report the concern.