WIR SCHAFFEN WISSEN – HEUTE FÜR MORGEN
Risk Assessment of Coal Combustion
Residue Disposal Impoundment Closure
Rebecca Lordan :: Guest PhD Student :: Paul Scherrer Institut
International Disaster and Risk Conference, Davos Switzerland, August 2016

Agenda
Page 2
• Motivation & Contribution
• Introductions:
 Coal Combustion Residue (CCR)
 Coal Mine Tailings
 Waste disposal methods
• Method for assessing risks
Tailings & CCR
• Results
• Conclusions

Why are we researching this?
Page 3

Our Contribution
Page 4
• Combine CCR and Tailings facility data into one database
Assumption based on 3 major shared attributes:
1. Materials share property: non-Newtonian fluids –
affects stability, destructive power, etc.
2. Wastes not economically valuable to operating firm
3. Management/engineering practices and problems
similar: stabilizing water balance, closure, etc.
• Analyze active facility risks to help assess long-term risks
• Consider the influence of Social-Technical Nexus on risks
 What information are closure & liability policies decisions
based on?
 How do closure & liability policy decisions affect safety?

Page 5
Coal Waste
Credit: tailinginfo
Mining Combustion
Credit: consumerssenergy

CCR Storage & Disposal Impoundments
Page 6
Powermag.comnbcnews.com
Source: EPA RIA

Tailings Storage & Disposal Impoundments
Page 7

Coal Combustion Residue: where is it?
Page 8
• Mapping of coal plants by number of surface
impoundments:
• total = 952
• average number per site = 2-3
• total sites = 383
0-1 impoundments
2-4 impoundments
5-14 impoundments Lordan et al., 2016

• Considering U.S. data only
• Data come from tailings and
CCR incidents
• 185 incidents and counting...
55 CCR incidents
130 tailings incidents
Page 9
Results: Active Site Incidents
0
20
40
60
80
active
dam
failureactive
tailings
accident
groundwater
inactive
dam
failure
Type of Release/Incident
NumberofCCR/tailingsIncidents
0
10
20
30
40
50
1940 1950 1960 1970 1980 1990 2000 2010
Year
NumberofCCR/tailingsIncidents

Results (Continued)
Page 10
0
10
20
30
40
U
nknow
n
<
10
10
−
20
20
−
30
30
−
40
40
−
50
50
−
60
>
60
Height (meters)
NumberofU.S.TailingsAccidents
0
30
60
90
N
otR
eported
U
pstream
D
ow
nstream
C
enterline
Construction Method
NumberofU.S.TailingsAccidents
0
20
40
60
80
U
nknow
n
<
10
11
−
20
21
−
30
31
−
40
41
−
50
>
50
Volume to Height Ratio (million liters/ meters)
NumberofU.S.IncidentsbyRatioofCapacitytoHeight
0
10
20
30
40
foundation
otherrelease
overtopping
seepageslope
instability
spill
structural
subsidence
Type of Release/Incident
NumberofU.S.CCR/tailingsIncidents

Mapping active incidents to closure risk
Page 11
• In so much as closure mitigates active risks, it’s only partially effective…
must also have endurance and cope with long-term hazards!
• Must map the actions of closure to risks:
For example, for dry closure, the materials are “de-watered”:
 Improves stability, reduces risk of soil liquefaction, can make facility
less sensitive to weather cycles (e.g. freezing, thawing…).
• Must consider long-term risks: physical, chemical, biological, and social
• Can closure provide endurance and cope with long-term hazards?
• Industry Argues: “Walk-Away” Closure (i.e. no maintenance or monitoring)
• Facilities in process of being closed provide data that shows “walk-away”
closure not possible
 Continuing contamination of soil and water
 Cover systems not behaving as anticipated

Long-term
Reuse
Environmental
Safety
Physical
Safety
We still want to close these facilities!
Page 12
• Reduce risks of
structural failure
(e.g. dam breaches)
• Reduce exposure
of people to
potentially
harmful ash,
using cover
systems
• Reduce
contaminant air
transport of
materials (land
fills)
• Reduce
soil/water
transport and
contamination
(depending on
the closure
method chosen)
• Stabilizes land for remediation and alternative future uses

General Closure Methods
Page 13
Clean Closure Dry Closure Wet Closure
Costs $
Risks
(Tailings Impoundments)
Relationship between costs and risks not necessarily inverse or specific
to one type of closure…. dependent on many factors

What do the costs and risks depend on?
Page 14
Based on our research, we created this word cloud to highlight some of the
key factors in assessing risk and costs for closure.

Page 15
Cover Closure Methods
Unlined Cap in Place Closure Lined Cap in Place Closure
http://www.duke-energy.com/ash-management/

Page 16
Closure Methods (Continued)
http://www.knoxnews.com/ http://partner.boliden.com/www/en/bolidenen.nsf/
Kingston Coal Ash Impoundment
Dry Remediation
Enåsen Copper Tailings Impoundment
Wet Remediation

Conclusions
Page 17
• The most common cause of dam failure caused by water balance
(e.g. structural/slope instability, foundation)
• Common cause of releases was seepage and leaking to surrounding
media (e.g. “seepage,” “spill” and “other release” on graphs)
• Releases from surface impoundments inevitable, but may not
exceed background or “tolerable” limits
• Availability of data subject to both detection and reporting
• There are many “technical unknowns” in the management and
closure of CCR facilities – to both industry and the public
How heterogeneous ash materials will settle and compact over
time
How to dewater and stabilize extremely large impoundments
How to prevent infiltration of precipitation in ash
… etc..

• Investigating the social components of long-term coal waste
storage and closure
How do limited liability and financial assurance influence
closure?
• Estimating the potential liability of the facilities that are
currently open
If the U.S. Government ends up “holding the bag” because
the coal industry doesn’t close or properly manage the
facilities, how much will remediation cost?
Future Work – Linking Social with Technical
Page 18

Social & Political Factors
Page 19
• Mapping of coal plants over median income. What role
might location play in the social distribution of impacts?
Low High

Page 20
Wir schaffen Wissen – heute für morgen
Paul Scherrer Institut (PSI)
Technology
Assessment Group (TAG)
http://www.psi.ch/
ta
rebecca.lordan@psi.ch
University of Chicago
Thank you for
your attention!
Any Questions?