Life-Cycle Uncertainty Management
The relative burden of uncertainty management shifts between regulators and responsible parties as the cleanup process proceeds.
The process of moving from characterization through remediation and closure involves collecting information with the ultimate goal of verifying that a site has been remediated to meet cleanup standards. Problem definition is often focused on determining whether unacceptable risk exists and determining the nature and extent of the contamination leading to the excess risk. Remediation is focused on cost effectively reducing the risk to acceptable levels. Verification is the process of confirming that the solution was effectively implemented.
Throughout the process, the cost of collecting information must be balanced against the value that information provides. Project managers and regulators must constantly assess the type, timing, quality, quantity, and cost of data needed to make decisions confidently (i.e., to manage decision-making uncertainty). The relative burden associated with managing uncertainty shifts back and forth between the project manager and regulator over the course of a project. Neither is ever fully relieved of this burden, but there are clear times when the bulk of it falls either to the project manager or to the regulator.
In the early stages of a project, the burden is shared equally between the project manager and regulator. The primary sources of uncertainty requiring management are associated with bounding the geographic limits of the site and defining the risk drivers. Regulatory agencies must be sure that all areas, media, and structures that may pose unacceptable risks are included in the scope of the project. Responsible parties are subject to jurisdictional requirements and must attempt to constrain the project to only those areas, media, and structures that pose a significant potential threat to human health and/or environmental quality.
During the characterization phase, the burden of managing uncertainty begins to shift towards the project manager as resources are expended on the process of data gathering. Ideally, the project manager would like to maximize the degree to which uncertainty is reduced for every dollar spent on characterization. Regulators must continue to make sure that new potential threats are addressed, and that "no further action" decisions are technically defensible. Both must be certain that adequate information is carried into the alternatives analysis so that an appropriate remedy, if necessary, can be developed for the site.
As remediation commences, the burden for managing uncertainty falls heavily on the project manager. Typically, the vast majority of project resources are expended during this phase. Project costs and schedules must be closely managed in an effort to most cost-effectively remediate the risk posed by the contamination. Project managers should explicitly recognize the type and amount of information they require and state it as quantitatively as possible in terms of expected uncertainty reduction relative to the key decisions that must be made.
During the remediation phase, particularly for soil excavation, there is constantly a tradeoff between the extent of remediation and data collection. Ideally, the project manager's goal is to remediate only those soils exceeding cleanup requirements, no more and no less. As with any decision, there is always uncertainty as to whether the cleanup goals have been attained. As the remediation is actively progressing, a balance must be achieved between the collection of data and continued remedial activity. When remediation is "complete," the project manager needs data that provide sufficient confidence that the site will pass any verification data collection that is done post-remediation.
Once the project manager decides that the area under remediation is clean and ready for verification surveying, the burden of uncertainty management shifts quickly and heavily to the regulator. The regulator is obligated to confirm that the remediation has met the legal requirements established for the project. For CERCLA (Comprehensive Environmental Response, Compensation, and Liability Act (Superfund)) projects, this means that the ARARs (Applicable or Relevant and Appropriate Requirements) have been met. For cleanups regulated by state agencies, this means compliance with state regulations.