Barangaroo Headland Park

01 Barangaroo Reserve

Barangaroo Headland Park

The Barangaroo Headland Park landscape uses almost completely recycled resources to make the soils suitable for the sensitive Sydney sandstone flora and the public park turf areas. The concept was first used at Sydney’s Olympic Parklands where crushed sandstone, an abundant natural recycled resource in Sydney, was successfully used to create soil profiles for bushland regeneration.

Building on that experience the SESL Australia soil scientists on the early detailed design phase for Barangaroo came up with a concept design for the completely reconstructed soils needed for the Headland Park. This original concept is given in Figure 1.

Project Details

 In this concept the three main materials to be used were:

  • Crushed sandstone originating from building excavations in Barangaroo South commercial developments
  • Recycled sand from building excavations
  • Recycled green garden waste compost (produced from “green bin” and council drop off garden waste collections)
  • Composted wood mulch screened from green garden waste collections.

These commonly available recycled resources could be used to make

  • The mulch layer or “O” (for organic) horizon analogous to the forest litter layer.
  • The topsoil or A horizon, a well drained sandy soil containing nutrients, organic matter and biological life.
  • The Subsoil or B horizon, a well drained water holding layer for root anchorage and moisture reserve.

The landscape below ground or the soil landscape at Barangaroo was carefully worked out to mimic the natural soil profile and thus support a vegetation type with unique requirements for healthy growth using almost 100% recycled resources sourced from in and around Sydney, from building sites, excavations, sand and glass recyclers (yes, “Glass sand” made from crushed recycled glass made up some of the sand requirement) and, of course, the very garden and green waste produced by Sydney householders.

The research performed by the BDA and its contractors resulted in two published scientific papers on the nutrition of native plants making the Headland Park very much a “Headland” project not just producing a beautiful place and displaying our unique flora but extending the knowledge of how to restore and rebuild a vegetation type that is part of the character of Sydney and its harbour.

The thing we did not know is how much compost and fertilizer to put in to the A horizon or topsoil layer. We knew that Sydney sandstone soils were so poor that the early settlers failed to grow adequate crops at the original Farm Cove gardens. We also know that if sandstone flora is fertilized or is affected by nutrient laden urban storm water runoff it suffers dieback and disease problems.

To answer this question we did some field research in areas of intact sandstone flora looking at the natural “Kandosol” or “Yellow Earth” soil characteristic of sandstone country. We examined the profile and measured the levels of nutrients and general soil chemistry. We found strongly acidic pH’s of 4.5 to 5.5, astoundingly low levels of phosphorus, around 25 mg/kg of total P in sandstone rock and around 60-80 mg/kg in the “biolayer” or topsoil horizon. Calculations showed that only around 10% by volume of green waste compost would be required to achieve this.

In a series of pot trials growing a range of sandstone flora we determined that the best range was, by volume 5% for the very sensitive sandstone heath areas, 10% for the Eucalyptus and woodland areas and 20% for the turf and fig trees in the recreational areas. The final soil specifications going out to tender were pictured in Figure 5.
Note: Fe2(SO4)3 is iron sulphate and is used to acidify the soil to obtain the correct pH range. IBDU and Methylene Urea are a slow release form of nitrogen, the only fertilizer needed.

Note that the compost provides all the nutrients, apart from nitrogen, that is needed. Just 5% by volume of compost is sufficient to establish a sandstone heath and scrub with no other fertilizers needed! Subsoil, of course, needs no organic matter and is even lower in nutrients.

We now had the soil profile concept and had calibrated and measured how much nutrition each planting area needed. All we now had to do was finalise the cross sections. An early diagram of the sandstone terrace facsimile illustrates how this was done so contractors tendering on the project could see how it was to be constructed. See picture 2.4*

The landscape below ground or the soil landscape at Barangaroo was carefully worked out to mimic the natural soil profile and thus support a vegetation type with unique requirements for healthy growth using almost 100% recycled resources sourced from in and around Sydney, from building sites, excavations, sand and glass recyclers (yes, “Glass sand” made from crushed recycled glass made up some of the sand requirement) and, of course, the very garden and green waste produced by Sydney householders.

The research performed by the BDA and its contractors resulted in two published scientific papers on the nutrition of native plants making the Headland Park very much a “Headland” project not just producing a beautiful place and displaying our unique flora but extending the knowledge of how to restore and rebuild a vegetation type that is part of the character of Sydney and its harbour.

Figure 1 Figure 2.4 Table 5

Accreditations / Affiliations