POWER October 2011 - 80

COAL ASH MANAGEMENT
At this time the MDE announced that
" Additional controls are needed to ensure
that we protect the public health and
the environment. While the U.S. Environmental
Protection Agency (EPA) has
been developing a proposal to regulate the
disposal and use of coal combustion byproducts
since 2000, no federal program
currently exists. Therefore MDE believes
it is necessary to move forward with our
own regulatory program (1). "
In February 2008, both Charah and
CPSGI submitted comments and recommendations
to the MDE on the proposed
regulations. The MDE's CCB regulations
were published on November 21, 2008, in
the Maryland Register, and they took effect
on December 1, 2008. The regulations
provide a regulatory framework for the
disposal of CCBs and the use of CCBs for
mine reclamation. Disposal facilities now
need to meet all the standards required for
industrial solid waste landfills, including
a leachate collection system, groundwater
monitoring, the use of liners, and routine
analysis of CCBs. Requirements were also
specified for CCB transportation and air
quality controls.
To comply with the new MDE regulations,
Charah navigated the site design and
engineering, permitting, and construction
process with the State of Maryland and
City of Baltimore over a period of over two
years. Throughout the process, Charah and
CPSGI actively included the participation
of the public and environmental groups,
allowing all parties' concerns to be voiced
and addressed. Multiple community association
meetings, public hearings, and collaboration
meetings with nongovernmental
environmental groups were held.
" There was never any question that the
site design was outstanding, " CPSGI Project
Manager Beth Pittaway said. " MDE
was ahead of other agencies, including
EPA, when they implemented the regu1.
The final act. Layout of a typical landfill
used for the disposal of coal combustion
by-products (CCB). Courtesy: Constellation
Power Source Generation Inc. (CPSGI)
Leachate
collection
system
CCBs
Liner
system
Existing clay base
(over 100 feet deep)
Groundwater
monitoring
well (typ)
80
Final cover
system
lation. Even after design and operations
plans were accepted by MDE, CPSGI
met with national and local environmental
group representatives to address their
concerns. The project gained their support
with some minor operational changes and
increased bonding on the site for long-term
care and closure. "
The project resulted in Maryland's first
permitted CCB landfill following enactment
of the state regulations. " This project
serves as a model of how industry and state
regulators worked together to implement
practical, safe, and environmentally conscious
CCB regulations, " stated Charles
Price, Charah's president and CEO. " Additionally,
the design conforms to the EPA's
proposed approach [to coal ash disposal]
under Subtitles C or D [of the Resource
Conservation and Recovery Act]. "
" Coal will continue to be a viable part
of the country's generation mix. This site
is a great example of how the by-products
of coal-fired generation can be addressed
in an environmentally responsible way, "
said John Long, president of Constellation
Power Generation, the Constellation Energy
affiliate that oversees the company's
Maryland-based coal plants. He added,
" we've always been keenly aware of the
need to manage coal combustion byproducts
in a manner that ensures the health,
safety and welfare of our community. For a
lot of reasons this site was one that allowed
us to meet our own high expectations. "
Property Characteristics and
Engineering Design
The property presented a unique and natural
environmental buffer, as it is situated
over a 100-foot-thick clay base at a permeability
of 1 x 10-7
cm/sec or less. This
buffer allowed Charah to place 60-mil
high-density polyethylene (HDPE) liner
directly on the graded subbase (Figure
1). The liner preceded installation of the
leachate collection system, which consists
of a network of 8-inch perforated HDPE
pipes surrounded by coarse aggregate, all
encased in filter fabric.
The leachate system also includes a 12inch
drainage layer and 12-inch protection
layer. Both specify a minimum hydraulic
conductivity of 4 x 10-3
cm/sec. The
leachate collection system was designed to
maintain the leachate depth over the bottom
liner to no more than one foot. The
pipe network drains to a leachate sump
that discharges into a double-lined collection
basin on site. The leachate collection
system is equipped with a telemetered and
audiovisual alarm system to provide continuous
monitoring. Once collected, the
leachate will be transported to an approved
wastewater treatment facility.
Long-Term Design and Permitting
Upon reaching fill capacity, the cells will
be closed by placing a 24-in clay cover layer
on top of the CCBs and a 40-mil HDPE
liner system over top of the cover layer
(Figure 2). A geocomposite drainage layer
will be installed above the 40-mil liner,
followed by 18 inches of protective soil, 6
inches of topsoil, and vegetation. This will
provide a fully encapsulated system and
will promote stormwater flow across and
off of the landfill to the designed stormwater
conveyance infrastructure.
A permanent stormwater management
(SWM) system will be implemented to
closely maintain the predevelopment runoff
characteristics after site development
and to enhance water quality at permitted
discharge points, as designated according
to the National Pollutant Discharge Elimination
System (NPDES) under the Clean
Water Act. Design parameters will provide
2. Topping it off. Upon reaching fill capacity, the cells of the CCB landfill will be closed by
placing a 24-inch clay cover layer on top of the CCBs and a 40-mil HDPE liner system over top
of the cover layer. Courtesy: CPSGI
Vegetation
6 " topsoil
18 " protective soil layer
Final intermediate cover
CCBs
24 " compacted clay
(k=1x10-7 cm/sec)
Prepared subgrade surface
Existing clay base
(over 100 feet deep)
(k10-7 cm/sec)
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Groundwater (Patapsco aquifer)
POWER | October 2011
Geocomposite drainage layer
Geomembrane
12 " protective layer
12 " drainage layer
Geomembrane
Patapsco aquifer

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POWER October 2011

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