POWER May 2012 - 22

Partnership Develops Innovative
CCP Project
In 2009, the North Carolina Asheville Regional Airport Authority
(Airport), with partners Progress Energy Carolinas Inc. and
Charah Inc., began development of the Westside Development
Fill Project (Westside Project), a long-term infrastructure strategy
located in the southwest quadrant of the Airport's property.
The project included phased construction of a developable pad
for general aviation and commercial use, a new taxiway running
parallel to the existing runway, and a major expansion of the
existing runway.
The Airport's Westside Project encompasses over 53 acres of
partially wooded land. When the partners determined that it
would require nearly 2 million cubic yards of suitable engineered
fill material to construct a developable pad for both general aviation
and commercial use (Figure 1), coal combustion products
(CCPs) emerged as an appropriate solution because of the potential
cost savings over conventional fill materials.
Many Design Challenges
Charah began development of the Westside Project by completing an
environmental assessment and an environmental due diligence audit.
As part of this audit, Charah characterized the physical and engineering
properties of the proposed CCPs by referencing the American
Society for Testing and Materials (ASTM) Standard's Guide for Design
and Construction of Coal Ash Structural Fills E 2277-03.
Charah also investigated the geologic and hydrogeologic
conditions within the 53-acre area with borings and the installation
of groundwater wells and piezometers. Subsequently, it
obtained the information necessary to characterize the subterrain
and input data required by the Environmental Protection
Agency's (EPA's) Industrial Waste Management Evaluation
1. Coal byproducts get new life. Aerial view of Asheville Regional
Airport Authority's Westside Project, which made use of coal
combustion products. Courtesy: Charah Inc.
Model to model the groundwater. Additionally, the company
surveyed for and delineated any preexisting environmental resources
(including jurisdictional streams, wetlands, and cultural
resources).
As development of the project continued, Charah incorporated local,
state, and federal permitting procedures for project design and
construction; coordinated the design and implementation of erosion,
sediment, and pollution prevention controls and activities; and followed
the testing, engineering, and construction practices for CCP
engineered fill projects.
Layered Engineering
When the environmental assessment was completed, engineering
began on this state-of-the-art engineered fill project. The project
features environmentally conscious controls such as a comprehensive
liner and cap system, drainage collection system, and
storm water management system.
State regulations do not require use of a comprehensive liner
system or an high-density polyethylene (HDPE) cap liner when
using CCPs as an engineered fill; however, Charah and Progress
Energy considered the application of these design elements environmentally
responsible and the only method suitable for this
project. Progress Energy's project manager, Rob Reynolds, noted,
" As a group, Progress Energy, Charah, and the Asheville Airport
agreed to utilize only state-of-the-art designs, products, and materials
for this project. We worked hard to design and construct
the first-of-its-kind, next-generation facility utilizing the latest
in environmentally sound engineering. "
The Westside project was engineered with a layered bottom and
cap liner system. The bottom liner system includes a compacted
in situ soil subgrade overlain with a bentonite geocomposite clay
liner (GCL) and a 60-mil HPDE liner. Both the GCL and HDPE liners
act as a barrier layer preventing any CCP material or related
moisture to pass through the comprehensive liner system.
To convey any contact water generated on top of the HDPE
to the drainage collection system, Charah proposed the use of a
geocomposite drainage liner placed on top of the 60-mil HDPE
liner. The drainage collection and conveyance system consisted
of a perforated 8-inch HDPE pipe encapsulated by #57 washed
stone wrapped in geotextile fabric. This system will convey any
generated contact water from the CCP fill to grit chambers. Collected
water is recycled within the CCP active working area as
dust control or transported to and treated by an approved wastewater
treatment facility.
The engineered fill needed for the Westside Project was acquired
by excavating CCPs from the ash basin at Progress Energy's Asheville
Plant in Skyland, N.C., approximately 1.5 miles from the airport. CCPs
are carefully excavated using long-reach excavators and loaded into
tri-axle dump trucks. The CCPs are then placed in a decant stockpile
adjacent to the ash basin so that an acceptable level of moisture can
be achieved. When the moisture content drops to the desired level,
the CCPs are transported to the project site for placement and compaction
as an engineered fill.
Excavating ash from the Asheville power plant's ash storage
basin also provides additional wet ash storage volume for the
376-MW plant.
Upon completion of CCP placement, a 30-mil HDPE cap liner
is used to encapsulate the material. In addition to the HDPE cap
liner, a minimum of 6 feet of compacted soil is placed across
22
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POWER May 2012

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