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In addition, the project manager should communicate data and results to the appropriate audiences. Frequently, the importance of communicating the results is underestimated. Because information is often provided to individuals with various levels of technical expertise, it should be comprehensible at multiple levels of understanding. Complex scientific data are not often easily understood by those without a technical background, and ineffective data communication often leads to skepticism about the conclusions. Therefore, it is important that the project manager consider the audience and present results in multiple formats. To those less familiar with the technical presentation of data, information can be presented in easily understood visual formats [e.g., geographic information system (GIS)]. This approach maximizes the effective dissemination of information to the greatest number of individuals, thus increasing the probability that the conclusions will be understood and believed.
Example: At this point, three years of fish tissue data have been collected, analyzed, and validated. The decision criterion for this monitoring objective was to reduce the PCB 8-8 Chapter 8: Remedial Action and Long-Term Monitoring concentrations in fish tissue to 0.8 ppm within five years. The data show that after the third year, fish tissue concentrations have decreased significantly but the averages are still above 0.8 ppm; however, the higher levels are restricted to a relatively small area and most fish are below 0.8 ppm. The results are summarized and presented to the stakeholders. Due to the declining trend, the decision is made that the monitoring objective is expected to be met within five years and the fourth year monitoring effort can be skipped.
Step 6. Establish the Management Decision
The final step of a monitoring plan should be an extension of Step 5, to evaluate monitoring results and uncertainties and come to a decision regarding any changes in site activities or changes in the monitoring plans that may be appropriate at this time. Developing contingency plans in advance for actions that may need to be taken in response to monitoring results is recommended.
Example: Due to the declining trend, the decision is made that the monitoring objective is expected to be met within five years and the fourth year monitoring effort can be skipped.
An outline of the six steps and suggested subparts is shown in Highlight 8-2. It should be noted that the following outline essentially follows EPA’s DQO process, with modification for ease of application to a contaminated sediment site. Project managers should refer to the DQO process guidance (U.S. EPA 2000a) to supplement this outline when preparing a sediment site monitoring program.
8.3 POTENTIAL MONITORING TECHNIQUES
This section provides a brief overview of the types of monitoring techniques and data endpoints that the project manager could consider when developing a monitoring plan. Selection of endpoints depends on the requirements in the decision and/or enforcement documents, as well as more general considerations related to the cleanup methods selected and the phase of the operation, as discussed in previous sections. For complex sites, frequently a combination of physical, chemical, and biological methods and a tiered monitoring plan (Highlight 8-3), is the best approach to determine whether a sediment remedy is meeting sediment cleanup levels, RAOs or goals, and associated performance criteria both during remedial action and in the long term. Monitoring, sampling, and analysis methods are being constantly improved based on research and increased field experience. Project managers should watch for new methods and, where they offer additional accuracy or lower cost but also allow for data to be compared to existing data, consider using them.
Generally, physical and chemical endpoints are easier to measure and interpret than biological endpoints. In the case of human health risk, chemical measurements are commonly used to assess risk.
In contrast, measurement of the biological community is a direct but often complex measurement for monitoring changes in ecological risk. Caged organisms (e.g., Macoma, or mussels) at the site over a defined time frame can identify changes in bioavailable concentrations of many contaminants. Collection of fish and tissue analysis can address both human health and ecological response of the system, if both needs are considered during design of the sampling and analysis plan. The project manager should refer to EPA’s Office of Water Methods for Collection, Storage, and Manipulation of Sediments for Chemical
and Toxicological Analyses (U.S. EPA 2001k) and Managing and Sampling and Analyzing Contaminants in Fish and Shellfish (U.S. EPA 2000h) for more detailed information.
Biological endpoints (e.g., toxicity tests) typically provide an integrated measurement of the cumulative effects of all contaminants. When using biological endpoints, it is important for the project manager to ensure the biological test employed fits the intended criteria. For example, acute toxicity tests are designed to quantify short-term effects on an organism; therefore, this type of test may be appropriate when monitoring for short-term impacts of a remedy. However, for toxicity tests to be useful, it is important to have demonstrated during site characterization a significant relationship between the contaminant and toxicity. Other biological endpoints, such as changes in species diversity, typically occur over long periods of time and may be more appropriate for use in a long-term monitoring program designed to look at ecological recovery. While no single endpoint can quantify all possible risks, project managers should consider a combination of physical, chemical, and biological endpoints to provide the best overall approach for assessing the long-term effectiveness of a remedial action in achieving the RAOs.
8.3.1 Physical Measurements
Physical testing at a site may include measurements of erosion and/or deposition of sediment, ground water advective flow, particle size, surface water flow rates, and sediment
homogeneity/heterogeneity. Potential types of physical data and their uses include the following:
• Sediment Geophysical Properties: Uses include fate and transport modeling, determination of contaminant bioavailability, and habitat characteristics of post-cleanup sediment surface;
• Water Column Physical Measurements (e.g., turbidity, total suspended solids): Uses include monitoring the amount of sediment resuspended during dredging and during placement of in-situ caps;
• Bathymetry Data: Uses include evaluating post-capping or post-dredging bottom elevations for comparison to design specifications, and evaluating sediment stability during natural recovery;
• Sediment Profile Camera Data: Uses include monitoring of changes in thin layering within sediment profiles, sediment grain sizes, bioturbation and oxidation depths, and the presence of gas bubbles; and
8-10 Chapter 8: Remedial Action and Long-Term Monitoring 8.3.2 Chemical Measurements Chemical testing may include sediment chemistry (both the upper biological surficial zone and/or deeper sediment), evaluating biodegradation, contaminant partitioning to the pore water, and concentrations of total organic carbon. Potential sampling tools and environmental monitoring methods
used in support of chemical measurements include the following:
• Coring Devices (e.g., vibracore, gravity piston, or drop tube samplers): Uses include obtaining a vertical profile of sediment chemistry, or detection of contaminant movement through a cap or through a layer of naturally deposited clean sediment;
• Direct Water Column Measurements (probes): Uses include measurement of parameters such as pH and dissolved oxygen in the water column;
• Surface Water Samplers: Uses include measurement of chemical concentrations (dissolved and particulate) in water or contaminant releases to the water column during construction;
• Semi-Permeable Membrane Devices: Uses include measurement of dissolved contaminants at the sediment-water interface; and • Seepage Meters: Uses include measurement of contaminant flux into the water column.
8.3.3 Biological Measurements Biological testing can include toxicity bioassays, examining changes in the biological assemblages at sites, either to document problems or evaluate restoration efforts, and/or determining toxicant bioaccumulation and food chain effects. Potential types of biological monitoring data and their
uses also include the following:
• Benthic Community Analysis: Uses include evaluation of population size and diversity, and monitoring of recovery following remediation;
• Tissue Sampling: Uses include measurement of bioaccumulation, modeling trophic transfer potential, and estimating food web effects;
• Sediment Profile Camera Studies: Uses include indirect measurement of macroinvertebrate recolonization, for example, measuring population density of polychaetes by counting the number of burrow tubes per linear centimeter along the sediment-water interface.
The interpretation of fish tissue results and their relationship to sediment contaminant levels can be especially complex. Potential complications may relate to questions of home range, lipid content, age, feeding regime, contaminant excretion rates, and other factors. Especially at low contaminant concentrations, these variabilities can make understanding the relationship between trends in sediment and biota concentrations especially difficult.
Fact sheets are under development at EPA concerning biological monitoring at sediment sites,
• An approach for using bioaccumulation information from biota sediment accumulation factors (BSAFs) and food chain models to assess ecological risks and to develop sediment remediation goals.
8.4 REMEDY-SPECIFIC MONITORING APPROACHESThe following sections discuss monitoring issues particular to MNR, in-situ capping, and dredging or excavation. Many sediment remedies involve a combination of cleanup methods, and for these remedies, the monitoring plan will likely include a combination of techniques to measure short- and long-term success. At many sediment sites, monitoring of source control actions is an important first step.
8.4.1 Monitoring Natural Recovery
Monitoring of natural recovery remedies often tests the hypothesis that natural processes are continuing to operate at a rate that is expected to reduce contaminant concentrations in appropriate media such as biota to an acceptable level in a reasonable time frame. Other measures of reduced risk may also be appropriate for a site. In most cases, monitoring involves measuring natural processes indirectly or measuring the effects of those processes. As a sound strategy for monitoring natural recovery the project
manager should consider the following:
• Monitoring direct or indirect measures of natural processes (e.g., sediment accumulation rates, degradation products, sediment and contaminant transport);
• Monitoring contaminant levels in surface sediment, surface water, and biota; and
8-12 Chapter 8: Remedial Action and Long-Term Monitoring When monitoring natural recovery, it is usually important to monitor sediment, surface water, and biota. The water column is typically important because it integrates the flux of contaminants from sediment and is not typically subject to as large a spatial variability as sediment. Biota monitoring is important because it is frequently directly related to risk.
Monitoring continued effectiveness of source control actions can be especially important at MNR sites. Depending on the quality of existing trend data, MNR remedies may require more intensive monitoring early in the recovery period, which may be relaxed if predicted recovery rates are being attained. Also, there may be a need to collect additional data after an intensive disturbance event.
EPA’s Science Advisory Board (SAB), in its May 2001 report, Monitored Natural Attenuation:
USEPA Research Program - An EPA Science Advisory Board Review (U.S. EPA 2001j), Section 3.4, Summary of Major Research Recommendations, indicates the need for the development of additional monitoring methods to quantify attenuation mechanisms, contaminated sediment transport processes, and bioaccumulation to support footprint documentation and analysis of permanence. EPA is aware of these research needs and plans to address some of these topics in ongoing and future work.
For areas that may be subject to sediment disruption, the project manager should conduct more extensive monitoring when specified disruptive events (e.g., storms or flow stages of a specified recurrence interval or magnitude) occur to evaluate whether buried contaminated sediment has been disturbed or transported and the extent of contaminant release contaminants and increased exposure. The project manager should design the monitoring plan to handle the relatively quick turnaround times needed to effectively monitor disruptive events. However, interpretation of these data in terms of increased risk should take into account the length of time organisms may be exposed to higher levels of contaminant concentrations.
The project manager should include periodic comparisons of monitoring data to rates of recovery expected for the site in an MNR monitoring program. Where predictions were based on modeling, the project manager should make monitoring results available to the modeling team or other researchers to conduct field validation of the model. Where contingency remedies or triggers for additional work are part of a remedy decision, the project manager should design the monitoring plan to help determine whether those triggers are met. For example, a contingency for additional evaluation or additional work may be triggered by an increasing or insufficiently decreasing trend in contaminant concentrations in sediment, surface water, or biota at specified locations. Where contingencies for additional work are triggered, the project manager may need to include measures such as additional source control, additional ICs, the placement of a thin layer of clean sediment to enhance natural recovery, or an active cleanup (i.e., dredging or capping).
Following attainment of cleanup levels and remedial action objectives, monitoring may still be needed at some MNR sites. For sites where natural recovery is based on burial with clean sediment, continued monitoring may be necessary to assess whether buried contaminants remain buried after an intensive disturbance event. This monitoring should continue until the project team has reasonable confidence in the continued effectiveness of the remedy.
8.4.2 Monitoring In-Situ Capping Remedial action monitoring for capping generally includes monitoring of construction and placement, and of cap performance during an initial period. It may also include monitoring of broader RAOs such as recovery of the benthic community or of contaminant levels in fish. Long-term monitoring for capping generally includes continued periodic monitoring of cap performance and maintenance activities, and continued monitoring of RAOs. In some cases (e.g., Fund-lead sites) it may be necessary to distinguish monitoring that is part of remedial action from monitoring that is part of O&M. This should be a site-specific decision. Highlight 8-4 lists sample elements of monitoring an in-situ cap. It is important to note that not all of these elements may be needed for every cap. In general, cap monitoring should be designed so that elements can be phased back or eliminated if the remedy is performing as expected and there has been no large-scale disturbance of the cap.