Equatica has been working with Marrickville Council on the design of a raingarden at Thornley Street in Marrickville.

This project was designed to alleviate local flooding, remove stormwater pollutants entering Cooks River and provide an interesting landscape in a small pocket park.

Local residents had reported a flooding problem in Holts Crescent, upstream of the site, to Council’s engineers. This photo was sent to Marrickville Council by a local resident.

To reduce the flooding a new pit and pipe was installed underneath the road. The pipe discharges water into a rock lined channel which cascades down a series of sandstone rocks into the small pocket park on Thornley Street.

At the base of the rock lined channel, a small sediment basin has been constructed. Water ponds here during a rain event, allowing solid pollutants to settle. Water then flows into the raingarden.

The raingarden is shown here during construction. The inlet to the raingarden (foreground) is temporarily blocked to prevent water entering during construction.

The raingarden consists of a number of soil layers including a gravel drainage layer (grey layer) a recycled sand layer (yellowish layer shown being spread evenly) and a special soil filter layer (not yet installed in this picture).

At the base, slotted drainage pipes are installed within the gravel layer. The vertical pipe is a flushing point for maintenance.

The walls have been constructed to create a basin with a flat surface, to allow water to pond and filter through the raingarden.

This image shows some important components of the raingarden. The square openings in the wall on the right hand side allow low flows into the raingarden.

In the middle of this photo is a sewer pit. This had to be accomodated within the sediment basin. It could not be lowered as this would have caused sewer overflows to discharge out of the pit. Hence it was left in place and is screened by sandstone rocks.

The tiered wall (bottom middle of the photo) shows the overflow weir from the sediment basin – during large or intense rainfall events stormwater will flow over this weir and bypass the raingarden via an extension of the rock lined channel.

During large rainfall events when the raingarden is full, water will also flow out through the overflow weir from the basin (middle of photo). It flows into the rock lined channel which directs water to a stormwater pit on Thornley St.

In May 2010, more than 20 local residents took part in a community planting day. The plants were supplied by Marrickville Council’s Community Nursery which specialises in local provenance plants from the Cooks River Valley.

The plants were specially selected for their suitability in the raingarden (plants that like getting their feet wet, typically found growing alongside creeks and rivers).