The City of Greater Geelong completed construction of an in-line Gross Pollutant Trap (GPT) on the foreshore of Corio Bay at Steampacket Quay in 2010. The GPT was specifically designed to be retrofitted into an existing underground concrete structure located in line with a major stormwater outfall. The structure originally housed a proprietary GPT that unfortunately failed following its first test with a major storm event.
The design of the newly constructed GPT was a collaborative effort between the City of Greater Geelong, Geelong Civil Fabricators and Bartlett’s Environmental (the contractors responsible for maintenance of the Cities GPT’s). It performs the function of collecting over 50 tonne of Gross Pollutants per year from one of the Cities major inner urban commercial catchments and is designed and constructed to ensure easy access during maintenance cleaning.
Waterfront Geelong is one of Australia’s best waterfront redevelopments. The transformation includes new restaurants, beautiful landscaped gardens, walking, cycling and skating paths, attractions and public art. Central features are Steampacket Quay and Steampacket Gardens where you can take a stroll beside the bay or enjoy a picnic on the lawns. An antique carousel beside the quay is a favourite with youngsters who can do laps on the 36 painted horses and two chariots to familiar melodies from a 19th century fairground organ.
To complete the picture, Waterfront Geelong has modern street lighting and street furniture to match the contemporary feel. Waterfront Geelong is also a major events venue, with its sweeping lawns and views providing backdrops for markets, sporting events and festivals.
Corio Bay provides the perfect venue for sailing and boating. Since Geelong’s founding more than 160 years ago, the bay’s waters have attracted people seeking recreation and fun.
A major stormwater drain discharges into Corio Bay at Steampacket Quay adjacent to Cunningham Pier collecting runoff from a 400 Ha catchment containing fully built up urban residential and commercial development including the Central Activity Area of Geelong. This catchment was identified as a major pollutant of Corio Bay and funds were sought for the installation of a Gross Pollutant Trap to enable the City to improve the quality of stormwater discharging to Corio Bay. The size of the inlet pipe is 2400 mm diameter.
An in-line litter trap was constructed adjacent to the main outlet pipe beside Cunningham Pier. A galvanized steel structure was installed inside a large concrete tank with flow dissipaters and baffles to allow high flows to by-pass the pit during major storm events. The original proprietary in-line litter trap had been successfully used at other sites. However its first test from a major 1 in 100 storm event “blew” the trap apart.
To build a litter trap that could survive the impact of major storm flows; could collect pollutants without impacting on the capacity of the drainage system; which had components that could be readily installed or replaced; and was accessible and simple to maintain was a challenge which the Project Team were prepared to tackle.
The final design is still an in-line trap with a flow dissipater at the inlet, flows are then directed under a floor of metal grills and concrete compartments that slow the flow and allow the pollutants to drop out, the pit fills to a point where the flows discharge via a restrictor at the end of the pit. Major flows directly bypass this grated structure to the main outlet pipe. Observation of the pollutants collected indicated that large items and floating litter is trapped in the first chamber with smaller and finer pollutants collecting in subsequent chambers.
During October / November 2010; and January / February 2011 the City experience a number of severe storm events which led to flash flooding across the City. The trap performed well during this time with minimal pollutants entering the Bay.
The pit chambers are accessed via a number of openings that when not required to be accessed have fitted covers that are covered with wood chips and form part of the foreshore passive recreation area. The pit is located off the main carriageway of Eastern Beach Road and is accessible from the Cunningham Pier car park.
The total cost of the project was $175,000. The contracted maintenance cost; including inspections, cleaning and waste disposal is approximately $21,000 per annum.
Bartlett’s Environmental manage all aspects of the inspection, cleaning and maintenance of the City of Greater Geelong’s (COGG) gross pollutant traps (GPT’s).
They inspect the Steampacket Quay GPT on a monthly basis, to check the level of pollutant build up and to ensure it is in good working order and not requiring further maintenance. Bartlett’s clean the GPT quarterly by means of an industrial vacuum unit. A host of materials including silt, litter and vegetation are captured and removed by their industrial vacuum unit. The sides of the GPT and the litter baskets are high pressure cleaned to remove any silt and debris that may accumulate.
All of Bartlett’s operators are trained in confined space entry ensuring the cleaning of the GPT is performed efficiently and safely.
Bartlett’s collect approximately 10-12m3 (or around 13 tonne) of waste from the Steampacket Quay GPT each quarter. The waste collected is disposed at an approved waste disposal and recycling site. The recent clean out following the major storm events of January and February (refer photos) collected over 28 tonne of waste material.
Following all inspections and cleans, the City of Greater Geelong receives an asset condition report detailing the condition of their GPT’s and informing them if further maintenance is required. The waste types and volumes collected are also recorded and reported to the City of Greater Geelong.
As the positioning of the Steampacket Quay GPT is in such close proximity to Corio Bay, attention needs to be taken when organising times for it to be cleaned. The Bay needs to be at low tide, to ensure the GPT is not full of water. To ensure traffic and parked cars do not obstruct Bartlett’s access, the GPT is cleaned early in the morning; and prior to Bartlett’s trucks arriving, the area is cordoned off.
In 2006, a time when the Victorian drought was severe, Bartlett’s recycled the collected water from the City’s GPT’s in their water treatment plant. This water was then used to water the council’s trees, sporting fields and community gardens. This initiative was resourceful at a time when water was in short supply and supported the local community. In 2007, Bartlett’s won a City of Greater Geelong ‘World Environment Day Award’ for this initiative.