The cache is tiny - bring your own pen
This lovely location is possible because of the Bennet Rd drain system and treatment train on the other side of the wetland from ground zero.
The term ‘treatment train’ refers to the provision of sequential items of complimentary water treatment. At this site (just across the water from ground zero), permeable paving is used to collect and provide filtration of stormwater. The water is delivered to a bioretention swale underdrain. Additional water captured by the swale is infiltrated through the swale filtration media and also collected by the swale underdrain. All of this water is delivered via a conventional drain to the wetland at the end of the bioretention swale.
The bioretention swale at this site was deliberately large to investigate the performance of different plants in South Australian conditions. Existing guidelines for vegetated water sensitive urban design (WSUD) systems are all sourced from Eastern states where rainfall patterns are different to those in South Australia, where there are significant dry periods in Summer.
Stormwater Harvesting and Reuse
The site makes a contribution to a wetland system which runs adjacent to the eastern boundary of the UniSA campus. All stormwater in these wetlands are collected, in addition to upstream urban runoff, by the Bennet Road drain aquifer storage and recovery scheme managed by City of Salisbury (Salisbury Water). The scheme is part of a network of schemes around the City of Salisbury supplying recycled stormwater to the Salisbury Water customers.
The car park waypoint also contains a bioretention swale, between buildings H and F and is a great example of the hardiness of water sensitive urban design (WSUD) infrastructure. Constructed in 1998, the system was originally at the centre of a compacted soil car park.
The car park was paved in 2010 but there was no significant rehabilitation of the bioretention system.
Water from parts of the car park flows to the bioretention swale. Water infiltrates through the filtration media of the system to subsurface pipes. The design is similar to the rain gardens adjacent to the M2 except that in this case, high flows are able to proceed across the surface of the swale to the outlet.
The system is designed to slow stormwater runoff flow rates, reduce runoff volume and provide passive treatment of car park stormwater runoff before it reaches the outlet drain.