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Blackwater Creek diversion and levee, Curragh, Australia

THE PROJECT

A flow of approximately 50 L/s was observed, when the bellmouths were closed, indicating a leak had developed within the HLDC. To protect mining operations in Pits C and D of the Curragh Coal Mine, Blackwater Creek low flows and floodwaters needed to be diverted and a protection levee constructed.

PSM was engaged to propose solutions that would enable permanent sealing (grouting). These could not be achieved without halting or reducing water flow from Blackwater Creek.

OPPORTUNITIES

A catchment area greater than 700 km² and a seasonal (cyclonic) rainfall coupled with limited hydrological records were key challenges that required careful evaluation in line with the client’s risk profile.

Engineering and technical challenges included:

  • Levee construction materials limited to predominantly clay and sandy soils
  • Potential for sandy soils in alluvial channels underlying the levee increasing the risk of potential piping through the foundation
  • Predominantly stiff to hard clays of the dragline road subgrade raising the prospect of poor subgrade conditions and the potential of failure in wet conditions
  • Dominant role of vegetative roughness on the Backwater Creek floodplain and the very small main (low flow) channel precluded using HEC RAS Backwater program, a de facto world standard.

APPROACH AND INNOVATION

PSM’s tailored approach included:

  • Assessment of geological and geotechnical conditions along the alignment with limited site investigation coupled with resource drilling data
  • Revision of previous 1985 hydrological studies with additional data eliminating the need for a new study
  • Completion of hydraulic designs using PSM’s in-house model using a variable vegetative roughness resistance algorithm and automatic partitioning of flow at a cross section. HEC RAS Backwater requires the user’s manual input
  • Material sampling and assessment of potential construction materials and levee/road foundations to assess in-situ conditions
  • Provision of geotechnical design parameters for the levee and pavement
  • Mechanistic analysis (using FLEA/CIRCLY) of pavement and subgrade to assess pavement thickness. Development of dragline road and LV pavement design

OUTCOMES

Low flows and floodwaters were successfully diverted with dragline access on a road along the pit-side of the levee together with LV access along the bund crest.

Services: #blackwatercreek #floodprotection #geotechnicalstudies #hydrologicalstudies #levee

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    Locations

    Sydney

    G3, 56 Delhi Road
    North Ryde NSW 2113

    BRISBANE

    Level 6, 500 Queen St
    Brisbane Qld 4000

    PERTH

    Level 3, 22 Delhi St
    West Perth WA 6005

    Geelong

    Shop 4, Suite 4, 23-31 Gheringhap Street
    Geelong VIC 3220
    Contact us
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