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Qualitative Risk Assessment of Coal Combustion Residue Impoundment Closure, Rebecca LORDAN

  1. 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
  2. Agenda Page 2 • Motivation & Contribution • Introductions:  Coal Combustion Residue (CCR)  Coal Mine Tailings  Waste disposal methods • Method for assessing risks Tailings & CCR • Results • Conclusions
  3. Why are we researching this? Page 3
  4. 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?
  5. Page 5 Coal Waste Credit: tailinginfo Mining Combustion Credit: consumerssenergy
  6. CCR Storage & Disposal Impoundments Page 6 Source: EPA RIA
  7. Tailings Storage & Disposal Impoundments Page 7
  8. 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
  9. • 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
  10. 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
  11. 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
  12. 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
  13. 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
  14. 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.
  15. Page 15 Cover Closure Methods Unlined Cap in Place Closure Lined Cap in Place Closure
  16. Page 16 Closure Methods (Continued) Kingston Coal Ash Impoundment Dry Remediation Enåsen Copper Tailings Impoundment Wet Remediation
  17. 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..
  18. • 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
  19. 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
  20. Page 20 Wir schaffen Wissen – heute für morgen Paul Scherrer Institut (PSI) Technology Assessment Group (TAG) ta University of Chicago Thank you for your attention! Any Questions?

Hinweis der Redaktion

  1. Bankruptcy in the coal mining sector is leaving many waste facilities to be cared for by government – liabilities discharged in bankruptcy court – slows down care and closure Situation and incentives of coal electricity utilities eerily similar with decline of coal to mining incidents – want to understand liability might have to take on as well as how closure can reduce risks
  2. Give examples of non-newtonian fluids: ketchup
  3. Three main different raising techniques: upstream, downstream, centerline
  4. So, what we’re doing is looking at the existing sites and the data about incidents they have had
  5. Explain difference between tailings and CCR
  6. Technique, costs, benefits, risks Explain each type of closure
  7. Say self-generated, and based on literature review
  8. Result from combustion of coal – all coal CCRs: fly ash, bottom ash, boiler slag, flue gas desulphurization gypsum Different coals have different contents of ash and sulfur – ash content can range from 3-49 % Sulphur content can range from <1% to >3% -- more sulfur means more gypsum waste