Advancements in Managing Uncertainty in Remedial Options Analysis and Remedial Action Plan Development for Northern Sites RPIC Edmonton 2015

Transcription

1 Advancements in Managing Uncertainty in Remedial Options Analysis and Remedial Action Plan Development for Northern Sites RPIC Edmonton 2015 David Wilson, Stantec Consulting Ltd. June 4, 2015

2 Agenda 1 Uncertainty in ROA and RAP Development 2 Project Impacts due to Uncertainty 3 Identifying and Characterizing Uncertainty 4 Uncertainty and Risk: Mitigation and Management 5 Case Examples

3 1 Uncertainty in ROA and RAP Development We demand rigidly defined areas of doubt and uncertainty! - Douglas Adams, The Hitchhiker's Guide to the Galaxy

4 Definitions Risk Treasury Board (2010b): the effect of uncertainty on objectives or the expression of likelihood and impact of an event Uncertainty Treasury Board (2010a): the state, even partial, of deficiency of information related to understanding or knowledge of an event, its consequence, or likelihood Environment Canada (2012): the state of having limited knowledge where it is impossible to exactly describe an existing state or future outcome

5 Types of Uncertainty Aleatory or Exogenous Uncertainty statistical variability and heterogeneity of the system (e.g., standard deviation of sample results) Epistemic Uncertainty model and parameter uncertainty (e.g., infiltration rate) Deep Uncertainty (CDMU, 2013) uncertainty about fundamental processes or assumptions Often forgotten: also includes scenario and decision-rule uncertainty

6 ROA and RAP Development Federal 10-step process Step 7: Develop Remedial/ Risk Management Strategy Consider project approach (remediate or risk manage; generic or site-specific) Determine remedial/risk management objectives Then consider remedial/risk management options

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8 Sources of Uncertainty SOURCE e.g.s: Background conditions poorly defined CSM not fully developed Some COCs not identified Impacts not delineated Decision criteria not defined NORTHERN SITE MAGNIFIERS Limited time/samples Limited site-specific physical system data Limited historical data Risk assessment exposure scenarios not typical Identifying/engaging stakeholders challenging Uncertainty is generally identified within a phase but is often not carried to a subsequent phase (e.g., from ESA to ROA/RAP; from RA to ROA/RAP; from ROA to RAP; from ROA/RAP to Cost)

9 2 Project Impacts Due to Uncertainty "No matter how good the team or how efficient the methodology, if we re not solving the right problem, the project fails - Woody Williams

10 Impacts of Uncertainty Uncertainty in CSM Uncertainty in remedy performance/project risk of remedy failure Errors in identifying appropriate technologies for actual site conditions and fate and transport mechanisms Uncertainty in Project Objectives Inappropriate clean-up goals/drivers Northern/Remote Site Challenges Use/evaluation of emerging technologies difficult Impact of short field season and seasonal demob After ITRC, 2011

11 Impacts of Uncertainty Quality DQOs not met Range of impact (COCs, volumes, risk y/n) Schedule Range of task durations Ill-defined go/no go criteria Cost Range of task costs Schedule Quality Cost

12 Quantifying Project Impacts Quality, e.g. Significant risks not identified Remediation over-scoped Schedule, e.g. Assessment extended/ revisited Remediation extended Cost, e.g. Exceed estimates Not optimized Schedule Quality Cost Projects reside here Every uncertainty will impact all three project dimensions they are inextricably interlinked

13 3 Identifying and Characterizing Uncertainty Madness is the result not of uncertainty but of certainty - Friedrich Nietzsche

14 Identifying Uncertainty Phase I/II/III ESAs Site history known and documented? How mature is the CSM? Contaminant concentrations compared to background? RAs Model and parameter uncertainty (e.g., contaminant fate + transport; exposure factors) defined? COCs and pathways supported by CSM? Remediation/Risk Management Objectives Future use decided? R/RM scenario and decision-rule uncertainty defined?

15 Characterizing Uncertainty Aleatory or Exogenous Uncertainty Measures of statistical variability: o standard deviation (parametric and non-parametric)/ standard error; variogram Bayesian probabilities Epistemic Uncertainty Model sensitivity analysis Monte Carlo simulation Deep Uncertainty Expert judgment Pairwise comparison of significance

16 Quantifying Potential Impacts Source Soil impacts not fully delineated Background not characterized COCs not identified Model uncertainty Decision-rule uncertainty Characterization # samples/m 2 or m 3 # background samples by media Predict likelihood compare to analogy sites Range of results from family of models Objectives for site defined? Quantification Impacted soil volume range: x m 3 ± y m 3 Parameter inclusion as COC: Y/N/Unk. Parameter inclusion as COC: Y/N/Unk. Level of confidence in model result Identify reliance of decisions on site objectives

17 4 Uncertainty and Risk: Mitigation and Management Fail to plan, plan to fail

18 Project Risk Management ITRC, 2011

19 The Project Risk Register What is it? Tool for estimating the impact of project risk on project outcomes How should it be developed? List identified and characterized hazards (including uncertainties), determine likelihood of occurrence and consequence (i.e., risk score) How can it be used? Identify, implement and monitor risk mitigation and management measures

20 Methods: Mitigating Uncertainty Exogenous Uncertainty Variability is due to spatial, temporal, or individual randomness and cannot be decreased by further data collection: it s impact can only be (and should be) managed Epistemic and Deep Uncertainties Rank first by risk significance (e.g., hazardous vs. non-hazardous, COC HQs), then by magnitude Work down ranking, and answer the questions: Does the uncertainty span a decision threshold? [e.g., remediate or risk manage; on-site or off-site disposal] Worth investing in reduction of uncertainty (mitigate), or better to manage? [Cost-benefit analysis]

21 Decision Threshold Examples Ex1 - Risk Assessment Scenario: HHRA HQ for primary COC, based on UCLM, yields a value of 0.3, exceeding threshold of 0.2. Expected HQ is <0.2 Decision: to remediate or risk manage Options: 1) accept conservative case and remediate; 2) invest in additional analysis to reduce epistemic uncertainty Ex2 - CSM Scenario: discontinuous permafrost site, groundwater shows metals impacts, one season of sampling, nearest surface water body 25 m Decision: to include a gw-sw pathway Options: 1) accept conservative case of a pathway; 2) invest in additional field work to reduce uncertainty

22 Cost-Benefit Example Situation Phase III ESAs have been completed on several abandoned mine sites grouped into a project. Significant areas of PHC and metals-contaminated soils have been delineated to varying degrees of certainty there is high confidence that all COCs have been identified, but low confidence in quantity estimates. Is investment in additional delineation warranted? Analysis Scenarios Scenario 1: additional season of assessment, followed by remediation Scenario 2: remediation Analysis Method Comparison of expected costs including uncertainty impact

23 Cost-Benefit Example cont d Scenario 1 Cost of additional season of assessment Cost of remediation, using expected lower uncertainty impacted soil quantity Scenario 2 Cost of remediation, using higher uncertainty impacted soil quantity Investment not Warranted Cost ($M): Assessment $0.45 Remediation $25.0 Cost ($M): Remediation $23.5

24 References and Tools References Environment Canada Federal Contaminated Sites Action Plan (FCSAP) Environmental Risk Assessment Guidance. ISBN no Cat. no. En14-19/1-2013E-PDF. Committee on Decision Making Under Uncertainty (CDMU) Environmental Decisions in the Face of Uncertainty. Board on Population Health and Public Health Practice. National Academy of Sciences. ISBN Interstate Technology & Regulatory Council (ITRC) Project Risk Management for Site Remediation. RRM-1. Washington, D.C.: Interstate Technology & Regulatory Council, Remediation Risk Management Team. TBS. 2010a. Framework for the Management of Risk. TBS. 2010b. Guide to Integrated Risk Management. Distribution Fitting ProUCL. Visual Sample Plan (VSP). vsp.pnnl.gov. Monte Carlo Simulation Tools Oracle Crystal Ball.

25 Questions? David Wilson, M.A.Sc., P.Eng. Senior Associate Stantec Ottawa (613)