Discover how water creates a livable city Water capture and reuse

Self-guided walking tour Stormwater Harvesting at Queen and Alexandra Gardens

Corner of St Kilda Road and Linlithgow Avenue

This tour begins at the corner of St Kilda Road Tour details and Linlithgow Avenue in the Parklands, directly across from the entrance Walking time: to the National Gallery of Victoria. Up to one hour

To begin this tour, make your way from the corner of St Kilda Road Distance: and Linlithgow Avenue towards the Children’s Pond. Walk past the 1 kilometre floral clock in the direction of the central city until you see the pond on your right. Make your way to the footpath between the first and Warnings: second ponds. This is the Stop 1. There is a road crossing on this tour. Please use the pedestrian crossing. Self-guided walking tour – Stormwater Harvesting Case study at and Alexandra Gardens 01

Project Overview

Context

This stormwater harvesting system Key project outcomes • Contributed 1.19 per cent towards captures, treats and stores 20 million This project has: the City’s 30 per cent alternative litres of stormwater each year to be used water target under the Total for irrigation, reducing the potable water • Saved 20 million litres of drinking Watermark Strategy; consumption in the garden by 55 per water per year; cent. The innovative system makes use of • Reduced pollutant levels of nitrogen, existing ornamental ponds in a heritage • Provided a reliable alternative water phosphorus, heavy metals and listed garden by retrofitting them for source for irrigation, securing the sediment entering the stormwater harvesting. health of the gardens through drought and Port Phillip Bay. and water restrictions; • Ensures that the gardens continue to provide ecosystem services in a changing climate

How does the system work?

Water is diverted from the existing Victoria Gardens before being retrofitted soil and plant root systems. The clean drains beneath for stormwater harvesting. When the water is collected under the biofiltration into a gross pollutant trap where large water level in the ponds reaches a bed in a pump well and transferred to an items, such as leaves and litter, are certain threshold, it is pumped across above ground storage tank. 230 kilolitres removed from the water. Next, a long to Alexandra Gardens for treatment, of water is stored here to be used sedimentation chamber settles out small via a pipe under Alexandra Avenue. for irrigating the gardens, and any particulate matter, including finer sand. excess clean water is returned to the In Alexandra Gardens a biofiltration Yarra River via the stormwater drains. A pump transfers the water to a series garden bed naturally removes pollutants of three ponds, which existed in Queen from the water as it seeps through the

Flow diagram of the Alexandra and Queen Victoria Gardens harvesting system Trin Warren Tam-boore  Case study wetlands 02

Self-Guided Tour

Stop 1: Children’s Pond and Nymph separately. Each pond also has a allows overflow into the second pond. Pond, Queen Victoria Gardens maximum draw down level that ensures The weir is beneath the pavement there is always enough water to prevent where you are standing. You are standing between the algal growth, support healthy plants Children’s Pond and the Nymph Pond. and maintain the aesthetic value. The second pond, known as the Nymph Pond, is 1100m2 in size and is deeper Unlike other stormwater harvesting The water you can see in these ponds than the Children’s pond. This functions systems in the City of , the is stormwater that has been diverted as both storage and treatment, with existing ornamental ponds in Queen from the stormwater drain underneath wetland plants providing aesthetic Victoria Gardens are used as the primary the grass near St Kilda Road. After the value and removing nutrients from water storage for this system because water is diverted from the drain, it passes the water. Similar to a raingarden, the the Coode Island silt soil profile was through a litter trap and a sedimentation biofilm that forms on the plant stems too unstable to support an underground chamber, which removes some pollution takes up pollutants, such as nitrogen tank storage system. from the water, such as litter and debris, and phosphorus, cleaning the water. sand and oils. A pump system transfers There are three ornamental ponds the water into the Children’s Pond. The top water level of the Nymph Pond that have been retrofitted for stormwater These components are buried beneath is controlled by an overflow weir. The storage, providing a total capacity the grass and can’t be seen. drawdown of water from this pond is of 1.1 million litres. Water flows from generally set to 300mm from the top the diversion system to the first pond, The first pond, known as the Children’s level, so that there is always enough then to the second pond, before Pond (closest to St Kilda Road) is water to support the plants and keep entering the third pond. shallow and primarily used as additional the ponds looking nice. However it can sedimentation rather than high volume be varied as required and is controlled The ponds each have their own elevation, storage. The water level in this pond is by the central control system. so the water levels are controlled controlled by a permanent weir that

To proceed to the next stop, walk along the length of the Nymph Pond, in the opposite direction to St Kilda Road. Ahead, you will come to the large Lower Pond with the waterfall flowing into it. Walk around the lower pond by following the path either to the left or the right, until you come to the short peninsula jutting out into the pond. This is Stop 2. Trin Warren Tam-boore  Case study wetlands 03

Stop 2: Lower Pond, Plants are the main source of treatment for The Nymph Pond had a clay base liner Queen Victoria Gardens the stormwater in this system, taking which was rolled across the base. Rocks, pollutants from the water in the upper and clay and soil for planting were placed on You are standing at the third pond in lower ponds, as well as the biofiltration top. the stormwater harvesting system, with bed. Aquatic plants are used within the Alexandra Avenue behind you. ponds, as well as some floating in the The lower ponds held water well centre of the Lower Pond, with collective throughout the drought and were deemed This pond is known as the Lower Pond, the plant coverage of approximately 1600 m2. to be fairly water-tight. Only minimal largest and deepest at a depth of 1 metre. contouring was carried out to provide The primary function of this pond is for Retrofitting the existing ponds to be part more planting opportunities. storage, though water plants you can see of the stormwater harvesting system around the edge and clustered throughout involved draining and sealing them to To proceed to Stop 3, walk along will provide some nutrient stripping as prevent leaking. The base of each pond Alexandra Avenue to the pedestrian well. A pump transfers water from this was sealed differently due to their crossing and cross the road. Turn left pond to the biofiltration bed in Alexandra construction and known leakage: after the crossing and walk back along Gardens, maintaining a minimum water the path until you reach the Skate Park level of 300mm below top level. The The children’s pond had a concrete base and café. You are now at Stop 3. diversion pumps shut off automatically and was painted with waterproofing when the ponds are full. membrane.

Stop 3: Alexandra Avenue, Installing the pipes under this major road To move on to the next stop, walk Alexandra Gardens was one of the key challenges when away from Alexandra Avenue, past the constructing this system. In addition to café building and towards the skate At Stop 3, you are standing beside the heavy volume of traffic, a number of park. You will see a garden bed Alexandra Avenue, looking back across service lines run underneath the road, containing grasses within a retaining at the pond system in Queen Victoria including electrical, gas and wall. This is Stop 4. Gardens. communications cables.

At Stop 3, you are standing directly Creating this link was a collaborative above the pipes that transfer the process between a range of stormwater from the Lower Pond to the stakeholders, both within the City of treatment system in Alexandra Gardens. Melbourne and externally. With a careful Ideally, the treatment system and storage mapping of existing cables and a traffic tank would have been located management plan in place, a tunnel was underground within Queen Victoria bored under the road at night. Gardens, but the unstable soil profile made this impossible. Trin Warren Tam-boore  Case study wetlands 03

Stop 4: Biofilter, Alexandra Gardens

At stop 4, you are standing beside a The flooding and resting cycle is based The top layer of the biofiltration bed is garden bed containing grasses. on the detention time of the water, which planted with ephemeral wetland plants, is determined by the hydraulic Juncus gregiflorus and Juncus procerus. This garden bed is a biofiltration system, conductivity of the filter media. The These native Australian rushes were also known as a biofilter. The biofilter cycle time is pre-set, but will be planted as tube stock, rather than cleans pollution from the stormwater so monitored and adjusted over time as the pre-grown plant slabs. Although pre- that it can be used for irrigation. The filter medium clogs and slows the grown plants provide immediate water biofilter is constructed the same way as a detention time. Replacing the top of the quality, planting them at a younger age is typical raingarden, with a sand filtration filter media on an annual basis will renew cheaper and can allow them to fully layer, a transition and a drainage layer. the conductivity. establish on site. Once per year, when the filter medium is replenished, the grasses Water is pumped from the Lower Pond, The clean water drains naturally under are cut back to encourage vigour. under Alexandra Avenue and into this gravity to the 10,000 litre pump well biofilter, periodically filling it with water. before being pumped to the above To move on to the final stop, continue If you are visiting during a cleaning cycle, ground storage tank where it can be along the path until you reach Boathouse you might see stormwater flowing into used as required for irrigation. Drive and the Yarra River. You have the biofilter through the plastic fountains reached Stop 5. and slowly soaking down into the sand. Trin Warren Tam-boore  Case study wetlands 03

Stop 5: Storage tank, Alexandra Gardens

You are at the edge of Alexandra Storage tanks for stormwater harvesting Gardens, looking back in the direction are commonly located underground to of the Skate Park. minimise the impact of the system on open space. In this instance, the soil The large, oblong, concrete structure profile was considered to be unsuitable that you can see (adjacent to the public because of the high proportion of toilets) is the storage tank that hold the unstable soil. clean water from the stormwater harvesting system until it is need for The site where the tank stands used to irrigating the park. The tank holds about be a depot building, so no public open 230,000 litres. The UV disinfection, space was lost in the gardens as a result irrigation pumps and controls are of the tank. housed alongside the tank.

The tour is complete! Directly across the Yarra River is another stormwater harvesting system in Birrarung Marr. Take a tour of the Birrarung Marr stormwater harvesting system to learn more.

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