CCR's, What Else? Timmons, Dale to: James Kohler 01/29/2013 11:18 AM

From: "Timmons, Dale" <Dale.Timmons@naes.com>

To: James Kohler/DC/USEPA/US@EPA

History: This message has been replied to and forwarded.



### Hi Jim:

After our discussion the other day, I went back to the Proposed Rule: Hazardous and Solid Waste Management System; Identification and Listing of Special Wastes; Disposal of Coal

Combustion Residuals From Electric Utilities and read the definition of CCR Surface Impoundment or Impoundment which appears on Page 35130 of the Proposed Rule. I reviewed this in the context of application of Dense Slurry System (DSS) technology on coal combustion

ash.

That definition is:

“CCR Surface Impoundment or impoundment means a facility or part of a facility which is a natural topographic depression, man-made excavation, or diked area formed primarily of earthen materials (although it may be lined with man-made materials), which is designed to hold an accumulation of CCRs containing free liquids, and which is not an injection well. Examples of

CCR surface impoundments are holding, storage, settling, and aeration pits, p onds, and lagoons. CCR surface impoundments are used to receive CCRs that have been sluiced (flushed or mixed with water to facilitate movement), or wastes from wet air pollution control devices, often in addition

to other solid wastes.”

The part of the definition that interests me is: “which is designed to hold an accumulation of CCRs containing free liquids”.

This part of the definition specifies a design but the spirit of the definition really is directed at impoundments that contain free liquids. Arguably, one could design an impoundment to contain free liquids but if free liquids were never stored in the impoundment, then it really would not

meet the intent of this definition.

An example provided as part of the definition includes: “CCR surface impoundments are used to receive CCRs that have been sluiced (flushed or mixed with water to facilitate movement)”.

Clearly, DSS technology uses water to facilitate movement of the ash. However, the water is also used to cause pozzolanic reactions designed to solidify the ash into a cement product. In addition, the water is consumed in these reactions stoichiometrically and thus is not free liquid for long; certainly not after 24-48 hours.

Dry ash systems also use water to facilitate movement; although partially for a different reason.

### Dry ash systems mix water with ash with as much as 15-20% water to suppress dust. This is done to facilitate movement with reduced risk of generating dust and to assist in compaction and solidification once the ash is placed in the impoundment (as with DSS).

One could argue that “dry ash management” mixes water to facilitate movement of the ash and thus, even dry systems, from one perspective, could be construed to incorporate mixing with water to facilitate movement. Further, “dry” ash is currently being placed into impoundments that were originally designed to accept ash containing free liquids. A literal interpretation of the definition of an impoundment would mean that impoundments that were designed to accept free liquids but which only contain dry ash would still have a questionable definition. These would not be attractive interpretations.

Both dry ash systems and dense slurry systems result in elimination of free liquids from ash impoundments. It seems clear that both dry ash management systems and DSS technology satisfy the intent of the rule to eliminate free liquids from surface impoundments. In fact, DSS results in a product with hydraulic conductivity that is lower than that resulting from dry ash management and exhibits reduced risk of dust generation. So, from the perspective of environmental protection, DSS is a superior process.

You had mentioned that you might be able to discuss this topic further internally. Any clarification that can be offered on the definition above and it’s applicability to ash management systems would be welcomed.

I appreciate your time an attention to this topic and I know that you have your work cut out for

you.

Best Regards,

Dale Timmons, R.G.| ESS Business Development| NAES Corporation

1180 NW Maple Street Suite 200 Issaquah, WA 98027

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dale.timmons@naes.com

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