In November 2009, Equatica, in partnership with Marrickville Council, built a small stormwater treatment wetland for a house in Marrickville. Marrickville Council advertised and organised the project as part of their Environmental Workshop Series, which also includes "Water Sensitive Urban Design on Your Property" workshops. More information is on Marrickville Council's website. This page steps through the process with lots of pictures; it's intended as a basic guide for anyone interested in constructing their own small wetland.

The first step was planning and design. David put together a brief document to illustrate the design:

Backyard wetland design (PDF)

To complete the design, we also did some more detailed measurements for the inlet and outlet design. The plan was to divert water from an existing downpipe, retain it in the wetland, and allow treated flows to escape back into the downpipe near ground level.

Next we spent a couple of weeks gathering all the materials and equipment we would need. At the end of the project, we put together a list of all the materials we used, along with prices:

materials list will be uploaded here soon...

The key components were:

  • two large planter boxes (to house the wetland)
  • a piece of galvanised steel (to form the inlet)
  • PVC pipe and fittings (to form the outlet)
  • soil
  • plants
  • various screws, nails and sealants

We used simple household tools in the construction, including a paintbrush, drill, file, saw, hammer, tin snips and caulking gun. A tape measure and spirit level were also indispensible.

Construction was undertaken with the help of Marrickville Council and several willing volunteers.

David explained the design and got everyone started.

We constructed the wetland using two large fibreglass planter boxes. We chose boxes that were relatively deep (500 mm) to make sure there would be room for the soil, permanent water, extended detention and some extra headspace to prevent overflows. The dimensions were also important for the space available.

We sealed two holes in the base of each planter box with builder's putty ("plasti-bond"). We also sealed the inside of the planter boxes with a pond sealant ("pondtite").

We connected the two planter boxes with a short section of PVC pipe. To do this, we had to cut a hole out of each box. These boxes were made of fibreglass and we cut them using a masonry drill bit.

Once we had drilled a hole in each box, we filed the hole to the right size.

Then we checked that the two boxes would fit together, before putting them in place.

We sealed all the joins with silicone sealant (Selley's wet area silicone). We chose a sealant that could tolerate inundation with water.

Before putting the planter boxes in place, we prepared the surface to make sure it was level.

At the inlet, we cut off the existing downpipe at the right level.

We used a 90 degree bend at the end of the downpipe. This was a pre-made piece of PVC in the right dimensions.

To construct the inlet, we also used a piece of galvanised steel. The idea was to use this as a channel to spread flows from the downpipe throughout the wetland.

We bent the steel into shape so that it would fit neatly under the deck. We bent it around a piece of wood, using a hammer.

We cut the steel to the right length using tin snips, and folded the end up so that water wouldn't run straight off the end. We used a couple of rivets to secure it, but you could also try strong glue.

The piece of steel now fit neatly under the deck and above the planter boxes.

We secured the inlet channel to the deck with a few screws.

To construct the outlet, we used a few sections of 65 mm PVC pipe, including two elbows. We measured everything up to ensure the outlet would sit at the right height.

We also used an expander to connect the 65 mm PVC back into the existing 90 mm outlet.

We cut the old downpipe off and connected the new outlet just above the ground.

We cut one more hole in one of the planter boxes, where the outlet pipe would go through.

The final element of the outlet was two small holes which will drain the extended detention. Most flows which enter the wetland will escape slowly via these two holes. High flows will overtop the edge of the outlet pipe.

Once these holes were in place, the sections of pipe were fitted together and through the edge of the planter box.

Finally the key structures were in place.

We finished off by gluing the inlet channel to the top of the planter boxes, so water couldn't escape between the cracks.

As planting media within the wetland, we used 3 bags of brickies sand (20 kg each) and 1 bag of organic potting mix (10 L). We mixed the planting media before placing it in the planter boxes.

We filled the base of the planter boxes with soil, up to the base of the connection pipe (about 150 mm)

We planted several different plants in the wetland, they were:

  • Eleocharis acuta
  • Schoenoplectus mucronata
  • Myriophyllum papill
  • Juncus usitatus

We filled the wetland with tap water to keep the plants wet until the first rain event. In this picture the inlet is weighed down with bricks to help it set in place.