Case Study

Sediment Management at the Patawalonga lakes System

The Patawalonga Lake System (PLS) receives between 4,000m3 and 8,000m3 of sediment every year in its catchment basins, from the Sturt River and Brown Hill Creek. Sediment accumulation has been a significant issue at the PLS since it was commissioned in 2001. If sediment in the PLS is not properly managed, it poses a threat to Patawalonga Lake water quality and aesthetic quality also contributing to the sediment load at Gulf St Vincent.
Maritime Constructions was contracted to remove the build-up of sediment material from the PLS Basin A and Diversion basin, dewater, treat and dispose of it in a beneficial manner. Maritime Constructions also provided the DEWNR with a long term option for the management of the PLS.
This project involved the use of a cutter suction dredge “Calamity” to remove over 3260 dry tonnes from the Patawalonga Lakes System (PLS). Sediment removed was piped to an approved dewatering system consisting of geotextile bags/tubes that separated water from the dredge slurry. Upon completion of the dewatering process, the sediment is loaded into trucks for transport offsite to Integrated Waste Services (IWS) Northern Balefill site for remediation and reintroduction into the environment as treated fill.


Scope of work

  • Sediment dredging of Basin A and Diversion Basin in the Patawalonga Lake System of over 10,000 in-situ m3.
  • Floating pipeline for slurry transfer constructed onshore and fed into creek, connected to dredge and connected to dewatering site geotextile tubes.
  • Water quality and slurry monitoring performed pre, during and post dredging.
  • Treatment & Disposal of Sediment
  • Dewatering bund is constructed using civil plant and consists of a single bund wall with the base of the bund sloping down toward the creek.
  • Lined with an impervious plastic which is welded to form a single impervious liner. 
  • 150mm of sand and 150mm of 20mm aggregate base is then laid and compacted to form a solid floor for the geotextile tubes to be laid. The low side of the bund wall has a spillway to direct clean water back to the waterway. 
  • The geotextile tubes are laid and then connected to the slurry transfer line via a manifold such that valves are easily accessible to direct, redirect or stop flows to the individual geotextile tubes. 
  • Transport and disposal of the dewatered sediment offsite to Integrated Waste Services (IWS) for remediation and reintroduction into the environment.
  • Demobilisation and site clearance


Client Organisation

Department of Environment, Water and Natural Resources
 

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