Collinsville ash dam leachate modelling and monitoring

Specifications

• Client: Transfield Worley Power Services and RATCH Australia Corporation
• Scope:

  Verterra used heavy metal concentrations obtained from core samples taken within the ash dam to estimate the leaching potential and theoretical steady-state leachate concentration of heavy metals based on the Sorption Distribution coefficient for each metal.  Estimates from each core provided a mean and standard deviation which was compared to both ANZECC trigger values an observed groundwater values to determine if predicted and steady-state leachate values were likely to exceed acceptable environmental limits.  In addition, graphical techniques using Piper plots and Stiff Diagrams were used to determine any systematic influences of the ash dam on groundwater.

• Challenge:

  To support approval from EHP for relinquishment of an Environmental Authority associated with operation of an ash dam, it was necessary to provide confidence that groundwater would not be unaffected by heavy metals occurring within stored ash.  It is difficult to provide the required level of confidence by simple monitoring alone.

• Solution:

  Verterra adopted a process-based approach that provided an understanding of likely heavy metal leaching processes, and informed a hypothesis that could be tested statistically.

• Benefit to Client:

   

  The approach provided significantly greater confidence than simple empirical sampling alone, and significantly shortened the required monitoring period between dam closure and Environment Authority relinquishment.  This provided a sound, evidence-based rationale for the client’s negotiation with the regulator, and ultimately, what is believed to be the first approval for an ash dam closure in Queensland.

   

• Market Sector: Power and Energy
• Capabilities:
  • Leachate modelling
  • Leachate monitoring
• Location: Queensland
• Year: 2013 - 2014