b. As a Low Density Road Base

   Class F ash usually is hauled to the construction site in covered dump trucks with the water content adjusted by spraying water on the loading conveyor belt or in the case of lagoon ash by blending the ash with drier silo ash.  The ash is spread in lifts of 150 to 300 mm thick.  The lift is then compacted to obtain the required in-place density.  Depending on the ash quality, leachate is normally not a problem with compacted ash that is appropriately graded to impede infiltration when a properly seeded soil cover is used to control erosion. Before proceeding the local environmental regulations should be checked to see that proposed work meets with the regulations.
   Compacted fly ash has mechanical behavior and compaction characteristics similar to silt.  Where it can wick water from a shallow groundwater table it also can share some of the difficulties of silt, such as being susceptible to frost heave as a result of ice lenses. Fly ash should not be used as a fill without an impermeable cover to prevent infiltration, below the groundwater table or where a drainage layer is not used at the bottom of the fill to prevent water wicking.

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