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Bioretention Basin Gatton Correctional Centre

Recently our team completed a bio-retention basin rectification project at the Gatton Correctional Centre.

On initial inspection, the Basin had several major issues.

Basin Rectification

These are the elements that composed our rectification strategy:

Spray weeds or remove them by hand. 


Use forestry mulcher to create maintenance access down the batter to the bio-retention basin. This will involve:

  • Clearing any trees on access alignment (regrowth only)
  • Clearing vegetation and remove any sediment/debris from the surface of the bio-retention system including ground covers and dispose.
  • Removal of vegetation on the batters was required for the removal of lantana and other weedy material. On completion batters were mulched and replanted with jute netting to a high water level to protect the embankment during the establishment phase. 


bio retention basin before gatton


bio retention basion after gatton

The downstream end of the bio-retention basin has a wall of gabions, through which the under drainage has been placed. The gabions form the end of the bio-retention and a bentonite liner has been installed between the filter media and gabion. The design is poor and has resulted in the washout of the filter media through the gabions and the creation of a number of large holes.


Create a barrier upstream of the outlet gabions. A range of options is available with the potential cheapest solution as per below. The final solution to be resolved with Programmed Facility Management.

Excavate the area upstream of the gabions for a distance of 2m. Excavation to an extent 500mm into in-situ soils below filter media. Care to preserve under drainage pipes.

Place well grade suitable clay fill and compact including around underdrain pipes.

Line the upstream surface of the fill material with Geofabric (Bidim A24) and install bio-retention drainage layer, transition layer and filter media and compact.

Install 100- 230mm rock mattress to the surface of fill material over Geofabric (Bidim A24) and tie into existing gabions

Erosion around ends of gabion weir

The gabion weir has not been properly extended up the batter to the natural ground (the weir has not been properly keyed in). The result is an erosion scour around both ends of the gabion weir.


Repair scour at ends of gabion weir and place rock scour protection (100-230m rock mattress) to up batter to tie in with existing levels. Extend gabion wall to solid embankment then add additional gabion basket on top of the existing wall each end to control and divert water to center of the overflow of the gabion wall. Compact additional clay on the embankment, place Geofabric (Bidim A24) and rock guard with 100- 230mm rock mattress to surface to protect embankment.


gabion weir before


gabion weir after 2020


Following extensive storm damage in rain events in early 2020, there were large washouts in the basins drainage media that occurred, requiring the removal of all existing vegetation and the importing of 100 cubic meters of filter media to repair the basin.

We then undertook, mulching, jute netting, and re-planting  of the basin in accordance with the Construction and Establishment Guidelines for Vegetation Stormwater Systems including use of fertiliser and water crystals in planting holes Planting numbers based on plant 50% of an area of 1700 m2

The installation of temporary irrigation from the site irrigation system or directly from the pond. At the end of 3 months, a review will be undertaken to consider whether any further establishment is required. The bio-retention will need to achieve the requirements (i.e. plant coverage, maturity) outlined by the measured of success in the Construction and Establishment Guidelines for Vegetation Stormwater Systems

Flush all under drainage pipes to ensure they are clean and draining.

Past Projects Completed

  • Repair and Construct Bush access tracks Northern NSW
  • Relocate Xanthorrhoea johnsonii (Grass Tree) Brisbane
  • Pre-Slashing Development site Brisbane
  • Relocate Brachychiton rupestris (QLD Bottle Tree) Brisbane
  • Slashing for Re-vegetation Gold Coast Hinterland
  • Repair and Construct Bush access tracks Northern NSW
  • Pre-construction Pad for Pillions Northern NSW
  • Fire Trail Access Gold Coast Hinterland
  • Pre-Survey Slashing Lantana Brisbane
  • Fire Trail Access & Erosion Control Gold Coast Hinterland
  • Removal and disposal of dumped car bodies, tyres and water tanks
  • Mulch Bioretention Basins Brisbane
  • Turf prep, bulk mulch, street trees at Aspire, Griffin
  • Translocate Livistona decipiens Townsville
  • Fire Fuel Reduction Slashing Gold Coast Hinterland
  • Deep rip and Rotary Hoe for Wetland Planting Gold Coast
  • Bulk Mulch Wetlands Gold Coast
  • Relocate Livistona decipiens Wollongong
  • Major Creek Rehabilitation Works
  • Slash 70 Hectares for Aboriginal Cultural inspection prior to development
  • Slash Firebreaks
  • Clean and remove spoil from 3 Bioretention Basins Brisbane
  • Relocate 5 Brachychiton rupestris (QLD Bottle Tree) & Cycads
  • Turf Prep and Street Trees Roma
  • Relocate 4 Brachychiton rupestris (QLD Bottle Tree) Roma
  • Slash Creek Embankment Area for Re-vegetation Brisbane
  • Clean and remove spoil Bioretention Basin Brisbane
  • Construction Wallum Frog Habitat Sunshine Coast
  • Slash 3 km x 15 meters Boundary Fire Breaks Brisbane
  • Repair and Construct Bush access tracks Northern NSW
  • Construct Walking Track Northern NSW
  • Fire Reduction Slashing and Clearing Acres Gold Coast
  • Stick Rake Lantana Brisbane
  • Bulk Civils Park Areas Brisbane
  • Bulk Civils and Rock Basin Brisbane
  • Turf Prep, Bulk mulch, Street trees, Park and slashing Griffin
  • Stick Rake & Slash 15 meter x 4 Km Fire Break Brisbane
  • Gold Coast Light Rail Stage2
  • Relocate 1200 Grasstrees Yarrabilba Development
  • Relocate large Figs Yarrabilba Development
  • Storm Damage Granada Productions Northern NSW repair road infrastructure and landslides

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