Federal contaminated sites long term monitoring: developing a plan

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The FCSAP LTM Planning Guidance is based on the United States Environmental Protection Agency (US EPA) six-step framework for developing LTM plans that will support management decisions and site closure (US EPA, 2004). Within this framework, Steps 1 through 3 document the logic and rationale of the monitoring program by developing monitoring objectives that are related directly to the objectives of the site remediation or risk management activity and by developing decision rules that will support site management decisions. Steps 4 through 6 ensure that this logic is maintained by focusing data needs and data collection and analysis methods to provide direct support to the monitoring objectives, decision rules, and subsequent management decisions. The framework is iterative and allows for evaluation of the monitoring data as they are generated, thus supporting adaptive management of the site activity and the monitoring program.

The following is a summary of the US EPA six-step framework for developing LTM plans and the key points to consider at each step:

1. Identify monitoring plan objectives

Monitoring plan objectives are specific statements that clarify the scope and intent of the monitoring program. Identifying a clear set of quantifiable monitoring objectives is critical for developing an LTM plan that is capable of achieving site closure where possible.

Monitoring objectives are identified by examining the site activities (e.g., engineered and institutional controls) that are used as part of the R/RM strategy. This examination should focus on the anticipated outcomes of the site activities, the mode of action, the exposure pathways for the human and ecological receptors determined to be at risk at the site, and the contaminants of concern and associated remediation objectives. Key assumptions of the R/RM strategy that need confirmation or require on-going monitoring to ensure continued protectiveness should also be identified during this review. Stakeholder involvement in defining monitoring objectives is important to ensure that the monitoring plan considers stakeholder issues and concerns and to facilitate final acceptance of the completed R/RM and LTM activities.

2. Develop monitoring plan hypotheses

Monitoring plan hypotheses are statements and questions about the relationship between an R/RM activity and one or more expected outcomes for that activity. The development of monitoring objectives, monitoring hypotheses, and a monitoring conceptual model serves to focus the monitoring program on achieving a desired outcome (e.g., site closure) rather than facilitating the continuous collection of data for an undefined purpose.

Identification of monitoring hypotheses is assisted by the development of a comprehensive post-remediation/risk management conceptual site model (CSM). The CSM summarizes all available site-specific information related to contaminant sources and release mechanisms, affected media, contaminant transport and environmental fate, and receptor exposure, and it should be updated to reflect post-R/RM conditions.

Key questions to consider when developing monitoring hypotheses based on the CSM are as follows:

• Where was contamination left on site?
• What are the residual vulnerabilities/risks to human health and the environment?
• Are there areas with incomplete understanding regarding R/RM assumptions and residual risk?
• Are there sentinel species, specific environmental media or measurement points on which LTM should focus?
• Have the locations and frequency of monitoring activities been identified on the basis of vulnerability and current scientific and traditional knowledge?

3. Formulate monitoring decision rules

Monitoring decision rules are quantitative pass/fail statements that are used to evaluate monitoring data and decide on a course of action. Decision rules include an action level (also called a trigger or a target) against which the monitoring results are compared, as well as management actions to be considered when the action level has or has not been exceeded. The development of scientifically defensible decision criteria is essential for effective project management and decision-making.

The following questions are useful in developing monitoring decision rules:

• Why are we going to monitor this specific component?
• What is the vulnerability or risk that LTM is mitigating?
• How would we know that there was a problem?
• What would constitute a trigger for action?

Action levels for decision rules should be consistent with remedial objectives for the site and the outcomes of the site-specific risk assessment. The LTM plan should also detail alternative actions to be considered for implementation when an action level has not been met, including a contingency plan and emergency response procedures if required.

To assess progress toward site closure, it is critical to establish quantitative exit criteria that represent the successful completion of each monitoring objective where possible. When the exit criteria are met, monitoring for that objective may be concluded.

4. Design the monitoring plan

In this step, the data needs, data collection and analysis methods, quality assurance/quality control (QA/QC) requirements and final decision rules are developed. The method for developing monitoring plans relies heavily on the use of the US EPA data quality objective (DQO) process (US EPA, 2000). It consists of the following four stages:

1. Identify the data needs: This stage identifies which data are necessary to test the monitoring hypotheses, to answer the monitoring questions, to test the validity of key assumptions for the conceptual site model, and ultimately to support a management decision. The QA/QC requirements should also be identified and documented as part of the monitoring quality assurance project plan (QAPP).
2. Determine the monitoring boundaries: These boundaries represent the “what, where, and when” aspects of the monitoring plan. Spatial boundaries delineate the entire geographical area of the site subject to LTM and define monitoring sample locations, including reference sites if appropriate. Temporal boundaries include identifying the index period for monitoring activities, the monitoring frequency, and the anticipated timeframe required before monitoring activities can be terminated.
3. Identify the data collection methods: The available approaches for collecting the required data are reviewed in this stage and screened to select the approach that will best meet the data needs within required time and cost constraints. A list of screening criteria to aid in selection of monitoring tools is presented in Box 3 of the FCSAP LTM Planning Guidance.
4. Identify the data analysis methods: The statistical design and approach for analyzing the monitoring data are determined in this stage, including DQOs such as the level of significance and statistical power. A robust statistical design is critical to ensure that the study design and data analysis methods are able to distinguish between natural variability in the data and actual response in the parameter being evaluated.

Following integration of these steps, the monitoring plan is reviewed and optimized to select the most cost-effective approach for data collection and analytical measurement that will meet the monitoring objectives. The final choice of monitoring program design, as well as the main assumptions and rationale for its selection, should be documented at this stage. An LTM report template and associated reviewer checklist are provided in Appendices D and E, respectively, of the FCSAP LTM Planning Guidance.

5. Conduct monitoring analyses and characterize results

As the monitoring data are collected, the first stage in data review is to determine whether the data meet the DQOs for the monitoring plan design outlined in the monitoring QAPP. If the data do not meet the DQOs, the underlying reasons for the deviations should be assessed. Once the cause of the deviations is identified, either the remedial strategy or the monitoring plan may be revised. Any changes should be documented as revisions to the LTM plan and/or monitoring QAPP.

6. Establish the management decision

If the data do meet the DQOs, the data are evaluated in this step to identify recommended actions for each monitoring objective using the decision rules established in the LTM plan. Where appropriate, trend analysis should be carried out to compare monitoring data with results from previous monitoring events. If the monitoring results are not trending towards meeting the decision rule, causative factor and uncertainty analyses should be conducted and recommendations should be made for revising the R/RM strategy and/or LTM plan if needed. The monitoring data should also be used to evaluate assumptions and uncertainties within the post-remediation conceptual site model and to refine the model where necessary.

In addition to evaluating the data in relation to the monitoring decision rules, project managers should assess the continued effectiveness of the R/RM strategy for protecting human health and the environment. Three key questions are used to evaluate remedy protectiveness as follows (after US EPA, 2001):

• Is the remedy functioning as intended by the R/RM plan?
• Are the exposure assumptions, toxicity data, cleanup levels, and remedial action objectives used at the time of remedy selection still valid?
• Has any other information that could call into question the protectiveness of the remedy been identified?

Finally, recommendations for changes to the scope of the monitoring program should be identified and an evaluation of progress towards site closure should be made. As exit criteria are achieved for each monitoring objective, related monitoring activities can be concluded. Site closure is achieved when the exit criteria have been met for all of the monitoring objectives. At this point, the remedial strategy and the monitoring program for the site may be concluded. The monitoring program outcomes and the scientific rationale used to determine that the site no longer poses unacceptable human health and ecological risks should be documented in accordance with the site closure tool and reporting framework developed by Public Works and Government Services Canada (PWGSC).

Final site closure may not be attainable for those sites at which contaminants remain in place (e.g., capped sites and those with engineered containment facilities) and ongoing maintenance and performance monitoring are required. However, as confidence in the conceptual site model assumptions and remedy performance increases, the scope and frequency of associated monitoring activities may be greatly reduced. As new technologies (e.g., remote sensing) become more broadly available, alternative methods for data collection that could meet the monitoring objectives in a more cost-effective manner should be explored as part of an adaptive site management approach.