Geosynthetics October/November 2019 - 13

Case Study

Alternative coal ash
pond closure design
and construction
Lessons learned

By Anna M. Saindon

C

oal ash pond closures often face unique challenges due to location, available borrow
soils and construction constraints. These challenges can lead to alternative methods
of closure to comply with Resource Conservation and Recovery Act (RCRA) Subtitle D and
coal combustion residuals (CCR) regulations. This article summarizes the construction of
the first permitted structured geomembrane/turf component system cap used in Illinois
and briefly discusses the constructability benefits and challenges that should be evaluated
during the design process of CCR pond closures.

PROJECT HIGHLIGHTS
Design stage
At the beginning of the design stage, a site-specific feasibility analysis for alternative closure
methods is suggested. When evaluating the capping-in-place method, the traditional soil/
geomembrane cap should be evaluated against other methods such as turf products and
include potential reuse options such as solar power generation in the life cycle evaluation.
A typical RCRA Subtitle D cap includes a smooth subgrade, geomembrane (typically
40-to-60-mil [1.0-to-1.5-mm] high-density polyethylene [HDPE]), geonet (if required by
slope steepness and stormwater design), 2.5 feet (0.76 m) of cover soil, 0.5 feet (0.15 m) of
topsoil and a vegetative cover. Since these are the current industry standard covers, the design
and approval process is relatively straightforward. Typical Subtitle D covers have issues with
erosion, high total suspended solids (TSS) in stormwater runoff, and difficulties establishing
and maintaining vegetation. The availability of borrow soils, lost air space, difficulties in
building partial closures, impacts to the surrounding population centers and limited land
reuse options affect the cost-effectiveness of the typical Subtitle D cover option.
Turf products have advanced to meet the performance requirements of RCRA Subtitle
D regulations and provide flexibility in areas with poor-quality soils or low soil availability,
long-term maintenance at decommissioned facilities or economic challenges over the life
cycle of the project. Turf products require a high level of communication with regulators
in states where they have not yet been used, but may net a significant amount of time and

COAL ASH POND CLOSURE
GENERAL CONTRACTOR

Blankenship Construction
Company
DESIGN ENGINEERS

Anna Saindon, P.E., R.G., Ph.D.,
Geotechnology and Matthew
Voss, P.E., CDG Engineers
GEOSYNTHETICS PRODUCTS

ClosureTurf, ArmorFill designed
by Watershed Geo
GEOSYNTHETICS MANUFACTURER

Agru America (MicroSpike)

Anna M. Saindon, P.E., R.G., Ph.D., is
project manager with Geotechnology
Inc. in St. Louis, Mo.
All photographs courtesy of the author.

www.GeosyntheticsMagazine.com

13


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Geosynthetics October/November 2019

Table of Contents for the Digital Edition of Geosynthetics October/November 2019

Geosynthetics October/November 2019 - Cover1
Geosynthetics October/November 2019 - Cover2
Geosynthetics October/November 2019 - 1
Geosynthetics October/November 2019 - 2
Geosynthetics October/November 2019 - 3
Geosynthetics October/November 2019 - 4
Geosynthetics October/November 2019 - 5
Geosynthetics October/November 2019 - 6
Geosynthetics October/November 2019 - 7
Geosynthetics October/November 2019 - 8
Geosynthetics October/November 2019 - 9
Geosynthetics October/November 2019 - 10
Geosynthetics October/November 2019 - 11
Geosynthetics October/November 2019 - 12
Geosynthetics October/November 2019 - 13
Geosynthetics October/November 2019 - 14
Geosynthetics October/November 2019 - 15
Geosynthetics October/November 2019 - 16
Geosynthetics October/November 2019 - 17
Geosynthetics October/November 2019 - 18
Geosynthetics October/November 2019 - 19
Geosynthetics October/November 2019 - 20
Geosynthetics October/November 2019 - 21
Geosynthetics October/November 2019 - 22
Geosynthetics October/November 2019 - 23
Geosynthetics October/November 2019 - 24
Geosynthetics October/November 2019 - 25
Geosynthetics October/November 2019 - 26
Geosynthetics October/November 2019 - 27
Geosynthetics October/November 2019 - 28
Geosynthetics October/November 2019 - 29
Geosynthetics October/November 2019 - 30
Geosynthetics October/November 2019 - 31
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Geosynthetics October/November 2019 - 33
Geosynthetics October/November 2019 - 34
Geosynthetics October/November 2019 - 35
Geosynthetics October/November 2019 - 36
Geosynthetics October/November 2019 - 37
Geosynthetics October/November 2019 - 38
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Geosynthetics October/November 2019 - 40
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Geosynthetics October/November 2019 - 53
Geosynthetics October/November 2019 - 54
Geosynthetics October/November 2019 - 55
Geosynthetics October/November 2019 - 56
Geosynthetics October/November 2019 - Cover3
Geosynthetics October/November 2019 - Cover4
Geosynthetics October/November 2019 - Blank1
Geosynthetics October/November 2019 - GeoConf20_1
Geosynthetics October/November 2019 - GeoConf20_2
Geosynthetics October/November 2019 - GeoConf20_4
Geosynthetics October/November 2019 - GeoConf20_5
Geosynthetics October/November 2019 - GeoConf20_6
Geosynthetics October/November 2019 - GeoConf20_7
Geosynthetics October/November 2019 - GeoConf20_3
Geosynthetics October/November 2019 - GeoConf20_8
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