In a combustion facility, a portion of the bottom ash (BA) is mixed with
substantially all of the fly ash (FA) as necessary to obtain a stabilized
material that prevents toxic metals solubility and achieves a desired
TCLP extraction pH value, preferably in the range of 8-11. The actual
quantities of BA to be mixed with FA will vary depending upon various
factors, so embodiments of the present invention include testing the ash
to determine the desired distribution to achieve sufficient alkalinity to
prevent the leaching of toxic metals in landfills. Because the resulting
ash has a desired alkalinity by design, minimal additional alkali reagent
amendment is necessary for safe disposal of the waste ash. The remaining
BA may be recycled or deposited in a landfill without additional
processing. Valuable materials in the waste ash may also be more easily
recovered and reused.