POWER June 2016 - 43

REGULATORY COMPLIANCE
1. In-place closure/consolidation. There are definite cost advantages to closing coal
ash impoundments in place, but there may also be some added long-term risk. This diagram
shows the sequence of actions needed when choosing the in-place closure option. Source: TRC
Companies Inc.
Standing water
Current conditions
Perimeter ditch for
dewatering
Dewatering
Affected soil to
be removed
Erosion layer (topsoil)
Berm fill used
for cover
Ash
In-place closure/consolidation
tions (such as testing traditional dewatering
and mechanical excavation versus hydraulic
dredging), placement of bridge fills over soft
CCR materials, handling of effluent discharge
waters, and construction of treatment
wetlands can all provide valuable information
in advance of full implementation.
Site-specific considerations, such as geographic
setting, geologic conditions, CCR
characteristics, site layout, plant operations,
and community involvement, can all come
into play when deciding on a game plan. While
the " most effective " method will be unique to
each site, the ideal solution will usually result
in the following conditions being met:
■ It is fully compliant with the CCR rule.
■ It is protective of human health and the environment.
■
It is cost effective.
■ It allows beneficial use.
■ It requires minimal disruption to existing
operations.
Beneficial Use and Onsite Disposal
The final rule provides a definition of beneficial
use to distinguish between beneficial
use and disposal. The definition essentially
states that the CCR must provide a functional
benefit; must substitute for the use of a virgin
material; and must meet relevant product
specifications, regulatory standards, or design
standards. There are additional requirements
for unencapsulated use of CCR, but we won't
get into those here.
The reason that understanding beneficial
use is so important is that the rule does not
regulate CCR that are beneficially used.
However, Nilsson said beneficial reuse of
CCR materials removed from surface imCIRCLE
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41
poundments appears to be limited to a smaller
percentage of facilities now.
Haul distances, end-user markets, processing
facility capacities, and public sentiment
most often govern the feasibility of reuse.
Even though CCR material makes a competent
structural fill and has been used in mass
earthwork projects, such as airport runway
Infiltration layer (geomembrane or clay)
expansions and mine reclamations, the public
seems to be increasingly wary of such uses,
even when protective liners and leachate collection
systems are put into place.
Absent any mining of CCR materials from
existing disposal units for beneficial reuse,
Nilsson said generators' preferred solution
seems to be storage/disposal of CCR materials
on plant properties. For in-place closures,
some CCR material can be removed from existing
impoundments and used as a structural
fill for a portion of the unit's closure or to
close adjacent impoundments (Figure 1).
Wellpoints
Ash
(to be removed
Dispositional delta at
discharge location
Ash
To
wastewater
treatment
or NPDES
discharge
2. Liquefaction. Unconsolidated coal
combustion residuals can turn quickly from solids
into liquids. Courtesy: TRC Companies Inc.
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POWER June 2016

Table of Contents for the Digital Edition of POWER June 2016