Coal Ash Dewatering

Coal Combustible Residuals: Challenges and Solutions to Dewatering and Disposal

  • Fly ash has low/no compressibility
  • Stabilization of fly ash for dry excavation results from reduction of pore water pressure, thus increasing cohesion
  • Key success factors for excavation dewatering:
    • Field permeability testing of fly ash in situ
    • Proper engineering analysis of permeability, flow conditions and expected drawdown
    • High intensity of dewatering by using closely spaced wickpoints that operate without disruption
    • Preventing recharge from aquifers or runoff
    • Effective filtration/treatment of discharged water

Three Distinct Sources of Water

  1. Impounded/free water which lies on top of the ash and comes from precipitation and/or sluicing.
  2. Groundwater which may intrude into the bottom of the ash.
  3. Interstitial water which lies in the pore spaces of the ash.

Griffin’s Approach to Engineered Dewatering Solutions for Ash Pond Excavations

  • Groundwater Modeling
  • Engineering and Design
  • Dewatering Systems
  • Pumps and Equipment
  • Filtration and Treatment
  • Maintenance and Operation

Griffin's Three Part Solution

The primary methods of ash pond dewatering are:

  • Wickpoints
  • Deep Wells
  • Well Points
  • Eductors
  • Sumping

Lowering the water content of ash pond materials by pre-drainage increases coal ash cohesion and stability.

This allows for vertical cuts to be made for large scale excavation with conventional excavation equipment.

Griffin has extensive experience treating groundwater and offers field tested solutions and equipment for our client’s water treatment requirements.

Griffin offers systems to address standard groundwater issues such as:

  • Total suspended solids
  • Nuisance mineral removal (Iron, manganese, etc.)
  • Hardness
  • pH
  • Hydrogen sulfide
  • Heavy metal removal
  • Radium
  • Radon
  • Selenium
  • VOC contamination

Ash Recovery Project - Tennessee Valley Authority
Griffin was contracted to lower water in ash more than 10’, creating a stable working platform and allowing a barrier wall to be constructed.

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