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Reliability and effectiveness of ICs are of particular concern with sediment alternatives, whether they are used alone or in combination with MNR, in-situ capping, or sediment removal. Project managers should recognize that, generally, ICs cannot protect ecological receptors or prevent disruption of an insitu cap by bottom-dwelling organisms. In addition, in many cases ICs have been only partially effective in modifying human behavior, especially in the case of voluntary or advisory controls. Although fish consumption advisories can be an important component of a sediment remedy, it should be recognized that they are unlikely to be entirely effective in eliminating exposures. Where advisories or bans are relied upon to reduce human health risk for long periods, public education, and where applicable, enforcement by the appropriate agency, are critical. This point is emphasized in EPA’s risk management Principle 9, Maximize the Effectiveness of Institutional Controls and Recognize Their Limitations (U.S.
EPA 2002a; see Appendix A).
Implementing and overseeing ICs can often be more difficult at sediment sites where control of the water body may involve multiple entities and a single landowner is not present to provide oversight and enforcement. As for other types of sites, at sediment sites, project managers should review ICs during the five-year review. Where a water body is owned or controlled by local, state, or federal 7-15 Chapter 7: Remedy Selection Considerations government entities, their regulations and guidance should be consulted to determine what governmental controls can be used to restrict the use of the water body, and the regulatory or administrative process to enforce such a restriction. In complex situations, it may be useful to layer a number of different ICs as discussed in the ICs site manager’s guide (U.S. EPA 2000f). Additional guidance on other aspects of ICs is under development by EPA.
7.6 CONSIDERING NO-ACTION As presented in Section 8.1 of the ROD Guidance, a no-action decision may be appropriate in the
• When CERCLA does not provide the authority to take remedial action; or • When a previous response(s) has eliminated the need for further remedial response [often called a “no-further-action” alternative].
Generally, if ICs are necessary to control risks caused by a contaminant of concern at a site, a noaction decision is not appropriate. For example, if fish consumption advisories or fishing bans are necessary to control risks from contaminants of concern at a site, a no-action decision for sediment is not appropriate, even if the advisories or bans are already in place. Instead, a remedy should be considered that includes at least the institutional control (e.g., advisories or bans), and, if appropriate, other actions for sediment or other media.
A no-action decision; however, may include monitoring. For example, sediment may pose no unacceptable risk to human health or the environment; however, uncertainties concerning that evaluation may make it wise to continue some level of monitoring. In this case, a no-action decision that includes monitoring may be appropriate. It is important to note that this is different from a MNR remedy where current or expected future risk is unacceptable and natural processes are being relied upon to reduce that risk to an acceptable level within a reasonable time frame. Although a no-action decision may require long-term monitoring, a MNR remedy generally needs more intensive monitoring to show that contaminant concentrations are being reduced by anticipated mechanisms at the predicted rates.
The focus of remedy selection should be on selecting the alternative best representing the overall risk reduction strategy for the site according to the NCP nine remedy selection criteria. As discussed in the OSWER Directive 9285.6-08, Principles for Managing Contaminated Sediment Risks at Hazardous Waste Sites (U.S. EPA 2002a), EPA’s policy has been and continues to be that there is no presumptive remedy for any contaminated sediment site, regardless of the contaminant or level of risk. Generally, as discussed in Chapter 3, Feasibility Study Considerations, project managers should evaluate each of the three potential remedy approaches (i.e., MNR, in-situ capping, and removal through dredging or excavation) at every sediment site. Project managers should develop a conceptual site model that considers key site uncertainties. Such a model can be used within an adaptive management approach to 7-16 Chapter 7: Remedy Selection Considerations control sources and to implement a cost-effective remedy that will achieve long-term protection while minimizing short-term impacts (refer to Chapter 2, Section 2.2 on conceptual site models).
Controlling any continuing sources of contaminants is an important factor for any sediment remedy (U.S. EPA 2002a). Where source control is uncertain, cannot be achieved, or is outside the scope of the remedial action, project managers should consider the potential for recontamination and factor that potential into the remedy selection process and into the long-term monitoring plan for the site. However, project managers should note that delaying an action to complete source control may not always be wise.
Early actions in some areas may be appropriate as part of a phased approach to address site-wide contamination even if sources are not fully controlled initially; in such situations, careful consideration should be given as to whether the uncontrolled sources will cause the early action to be ineffective.
At many sites, but especially at large sites, the project manager should consider a combination of sediment approaches as the most effective way to manage the risk. This is because the characteristics of the contaminated sediment and the settings in which it exists are not usually homogeneous throughout a water body (NRC 2001). As discussed in the remedy-specific chapters of this document, when evaluating alternatives, project managers should include realistic assumptions concerning residuals and contaminant releases from in-situ and ex-situ remedies, the potential effects of those residuals and releases, and the length of time a risk may persist.
The project manager should include a scientific analysis of sediment stability in the remedy selection process for all sites where sediment erosion or contaminant transport is a potential concern.
Typically, it is not sufficient to assume that a site as a whole is depositional or erosional. Generally, as discussed in Chapter 2, Remedial Investigation Considerations, project managers should make use of available empirical and modeling methods for evaluating sediment stability and fate and transport, especially when there are significant differences between alternatives.
The project manager should include in the remedy selection process a clear analysis of the uncertainties involved, including uncertainties concerning the predicted effectiveness of various alternatives and the time frames for achieving cleanup levels and remedial action objectives. Project managers should quantify, as far as possible, the uncertainty of the factors that are most important to the remedy decision. Where it is not possible to quantify uncertainty, the project manager should use a sensitivity analysis to determine which apparent differences between alternatives are most likely to be significant.
The project manager should monitor all sediment remedies during and after implementation to determine if the actions are effective and if all cleanup levels and remedial action objectives are met.
Sediment remedies should not only include monitoring of surficial sediment immediately following implementation of the action, but also long-term monitoring of sediment to assess changes in residual contamination and possible recontamination, as well as monitoring of fish or other relevant biota recovery data. Without these data, an assessment of the long-term effectiveness of the remedy is difficult, and fiveyear reviews may be difficult to perform accurately. Additional monitoring data may help not only to assess the site but to help build a body of knowledge that will decrease uncertainties in decision making at future sites. Chapter 8, Remedial Action and Long-Term Monitoring, discusses these and other general monitoring considerations for contaminated sediment sites.
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Chapter 8: Remedial Action and Long-Term Monitoring
8.0 REMEDIAL ACTION AND LONG-TERM MONITORINGThis chapter provides a recommended approach to developing an effective monitoring plan at contaminated sediment sites. A monitoring plan is recommended for all types of sediment remedies, both during and after remedial action. Monitoring should be conducted at most contaminated sediment sites for a variety of reasons, including: 1) to assess compliance with design and performance standards; 2) to assess short-term remedy performance and effectiveness in meeting sediment cleanup levels; and/or 3) to evaluate long-term remedy effectiveness in achieving remedial action objectives (RAOs) and in reducing human health and/or environmental risk. In addition, monitoring data are usually needed to complete the five-year review process where a review is conducted.
A fully successful sediment remedy typically is one where the selected sediment chemical or biological cleanup levels have been met and maintained over time, and where all relevant risks have been reduced to acceptable levels based on the anticipated future uses of the water body and the goals and objectives stated in the record of decision (ROD). Due to the significant post-remedial residual contamination at some sites, or the inability to control all sources of contamination to the water body, reaching sediment or biota levels resulting in unlimited exposure and unrestricted use may take many years if not decades. Where appropriate, several interim measures of remedy effectiveness should be evaluated at most sites in addition to the key measure of long-term risk reduction. Highlight 8-1 presents four measures that should be considered for all Superfund sediment sites where the remedy includes active remediation such as dredging, excavation, and/or capping. At sites where achieving protection relies upon institutional controls (ICs) such as fish consumption advisories and/or on monitored natural recovery (MNR), only measures 2 and 4would typically apply. A monitoring plan that addresses the appropriate measures generally should be developed and implemented at every sediment site. The term “remedy effectiveness” as used in Highlight 8-1 of this guidance addresses the potential role of monitoring in measuring progress, not as one of the nine criteria provided in National Oil and Hazardous Substances Pollution Contingency Plan (NCP) to evaluate alternatives.
Highlight 8-1: Sample Measures of Sediment Remedy Effectiveness recovery been accomplished?) For Fund-lead sites subject to a state cost share, it may be necessary to distinguish monitoring that is part of the remedial action phase of the remedy from monitoring that is associated with the
operation and maintenance (O&M) phase of the remedy. Distinguishing these two monitoring activities is a site-specific decision. Project managers may find it useful to refer to Chapter 3, Section 3.5.2, Operation and Maintenance Costs, for suggestions about what types of activities are frequently associated with long-term O&M as compared to similar activities typically conducted during the remedial action.
This chapter is based in part on the framework presented in the U.S. Environmental Protection Agency’s (EPA’s) new “Monitoring Guidance,” Office of Solid Waste and Emergency Response (OSWER) Directive 9355.4-28, Guidance for Monitoring at Hazardous Waste Sites: Framework for Monitoring Plan Development and Implementation (U.S. EPA 2004c). This chapter presents more specific guidance for monitoring of sediment sites; however, many technical details are outside the scope of this chapter. More specific guidance on particular monitoring topics is under development by EPA to assist project managers. In addition, the “triad approach” to systematic planning, dynamic work plans and real-time measurement technologies may have strategies that can be fruitfully applied to sediment site monitoring (see http://www.epa.gov/tio/triad).
As described in EPA’s Monitoring Guidance (U.S. EPA 2004c), monitoring may be viewed as the collection and analysis of repeated observations or measurements to evaluate changes in condition and progress toward meeting a management objective. Monitoring should include the collection of field data (i.e., chemical, physical, and/or biological) over a sufficient period of time and frequency to determine the status at a particular point in time and/or trend over a period of time in a particular environmental parameter or characteristic, relative to clearly defined management objectives. The data, methods, and endpoints should be directly related to the RAOs and cleanup levels or remediation goals for the site.
Environmental sampling and analysis is typically conducted during all phases of the Superfund process to address various questions. By the time a project manager is implementing a remedial action or writing a monitoring plan, a considerable amount of baseline site data should have been collected during the remedial investigation or site characterization phase. In the site characterization phase, sampling is performed to determine the nature and extent of contamination, to develop the information necessary to assess risks to human health and the environment, and to assess the feasibility of remedial alternatives.
During site characterization, the project manager should anticipate expected post-remedy monitoring needs to ensure that adequate baseline data are collected to allow comparisons to future data sets.
Monitoring plans should also be designed to allow comparison of results with model predictions that supported remedy selection.
Project managers should ensure that agreements with contractors or responsible parties concerning remedial design and remedial action include requirements for development of an appropriate monitoring plan. The need for environmental monitoring and how the data will be used to measure performance against cleanup levels and RAOs should be considered in the ROD and discussed further early in the remedial design process. Where ICs are part of the remedy, this discussion should also include implementation and, where appropriate, monitoring plans for those controls. Having an early discussion of the monitoring needs as they relate to any engineering performance standards for the particular remedies should allow the project manager sufficient time to resolve logistical or other implementation issues long before the monitoring program is put in place. This discussion during remedial design is also important to determine whether sufficient baseline data have been collected so that both the remedial action and long-term monitoring data can be easily compared to pre-remedy conditions.
8-2 Chapter 8: Remedial Action and Long-Term Monitoring At sediment sites, it is also frequently necessary to continue collecting background data from upstream or other reference areas away from the direct influence of the site. This can be especially important where there are uncertainties or potentially changing conditions in background areas, for example, where upstream urban storm water runoff or other possible continuing sources of contamination could impact a remedy.
During the remedial design phase, it is also important to develop a clear understanding of how the monitoring data will be used in the post-remediation decision process, and to ensure that reviews of the monitoring results are conducted in a timely fashion so additional actions can be taken when necessary.
In this way, the monitoring data should become a key element of the decision process both in terms of whether the cleanup levels and RAOs are being met and whether additional management actions are warranted.
Highlight 8-2 lists some key questions the project manager should answer before developing a monitoring plan.
• Are detection limits adequate to meet the purpose of the monitoring?