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Residual risk following MNR and permanence for a MNR alternative frequently are related to the stability of the sediment bed, or the chance that clean sediment overlying buried contaminants may be eroded to such an extent that unacceptable risk is created. Residual risk for an MNR remedy may also be related to the chance that ground water flow, bioturbation, or other mechanisms may move buried contaminants to the surface where they could cause unacceptable human or ecological exposure, even in otherwise stable, non-erosional sediment. Whether erosion, ground water flow, or other processes cause unacceptable risk depends on the rate of exposure due to those processes. For example, erosion of some portions of a sediment bed, or some movement of contaminants through bioturbation, may not create an unacceptable risk; therefore, it is important to review such factors on a site-specific basis. Evaluating the adequacy of controls for these risks in an MNR remedy may include evaluating the ability of the monitoring plan to detect significant sediment erosion or contaminant movement, and evaluating the adequacy of any institutional controls that are relied upon to control erosion (e.g., dam or breakwater maintenance agreements).
For an in-situ capping remedy, risk due to direct exposure to contaminated sediment in the capped area generally decreases rapidly, although risks may remain from uncapped areas. The level of risk reduction associated with this remedy generally depends on the action level selected for capping (i.e., what level of contamination will remain outside the capped area) and the level of contamination that may continue to enter the system from any uncontrolled sources. Residual risk, after the cap is in place, usually is related to the following: 1) likelihood of cap erosion or disruption exposing contaminants; 2) likelihood of contaminants migrating through the cap; and 3) risks from contaminants remaining in uncapped areas. Like MNR, whether cap erosion or contaminant migration through a cap cause unacceptable risk depends on depends on the rate of exposure due to those processes. An evaluation of long-term effectiveness and permanence for capping also should include an evaluation of the ability to monitor the effectiveness of the cap and to replace or replenish components of the cap through time before any significant contaminant releases occur.
3-16 Chapter 3: Feasibility Study Considerations Dredging or Excavation For a dredging or excavation remedy, risks within the site itself may initially increase due to increased exposure to contaminants released into the surface water during sediment removal, but this increase should be temporary and localized. After this time, risk should decrease. The speed of the decrease and the level of long-term risk reduction associated with this remedy generally depends on the action level and/or cleanup levels selected for sediment removal (i.e., what level of contamination will remain outside of the dredged/excavated area), the level of residual contamination in the area after dredging, and the level of contamination that may continue to enter the system from any uncontrolled sources.
Residual risk, after the dredging or excavation is complete, is usually related to the following: 1) risk from contaminated sediment left behind outside of the dredged or excavated areas and from contaminated sediment resuspended and transported by dredging; 2) residual contamination left in place after dredging (an estimate of the likely post-dredging/post-backfilling surficial contamination levels should be developed); and 3) risk posed by untreated contaminants and treatment residuals at their disposal location. Similar to capping, the long-term effectiveness evaluation should include the need to replace technical components of the remedy after remedial action is completed. For dredging or excavation, this usually focuses on technical components of any on-site disposal units and the need to replenish backfill material in the dredged areas if backfill was used.
Project managers should recognize that all approaches for remediating sediment leave some contaminants in place after remedial actions are completed, whether buried beneath a natural sediment layer or engineered cap, left near the surface or mixed with backfill as residuals following dredging or excavation, or as low levels of contamination outside of areas that were capped or dredged. All of these residual contaminants are affected by a variety of natural processes that can disperse, contain or sequester them. As described above and in the three remedy-specific chapters of this guidance that follow, MNR, in-situ capping, and sediment removal, each may be capable of achieving acceptable levels of effectiveness and permanence. Site-specific site characteristics should be reviewed to ensure that the selected alternative will provide adequate short-term and long-term effectiveness at a particular site.
Developing accurate cost estimates generally is an essential part of evaluating alternatives. It is also appropriate at many sites, and can be especially useful at large sites, to include the relative cost of achieving different cleanup levels. This typically is an important part of evaluating the cost-effectiveness of a range of protective alternatives which may, for example, be associated with different fish consumption rates or different levels of ecological protection.
Guidance on preparing cost estimates and the general role of cost in remedial alternative selection is discussed in A Guide to Developing and Documenting Cost Estimates During the Feasibility Study (U.S. EPA and USACE 2000). The general elements of a cost estimate include capital costs, annual and periodic O&M costs, and net present value (U.S. EPA and USACE 2000). A cost estimate prepared as part of the CERCLA cleanup process should not include potential claims for natural resource damages or potential restoration credits, but may include costs for mitigation of habitat lost or impaired by the remedial action, where appropriate.
3.5.1 Capital Costs Capital costs generally are those expenditures needed to construct a remedial action (U.S. EPA and USACE 2000). Capital costs include only those expenditures initially incurred to implement a remedial alternative and major capital expenditures in future years. Capital cost elements that may be important at sediment sites include those listed in Highlight 3-3. As indicated in the Highlight, capital costs may include construction monitoring and environmental monitoring before, during and immediately following the remedial action. Monitoring beyond that point should be considered part of O&M.
General (may apply to • Mobilization/demobilization several or all remedial approaches) • Site preparation (e.g., fencing, roads, utilities)
The basis for a cost estimate may include a variety of sources, including cost curves, generic unit costs, vendor information, standard cost estimating guides, and similar estimates, as modified for the specific site. Where site-specific costs are available from pilot studies or removal actions, they are likely to be the best source of realistic cost information. Where this is not available, actual costs from similar projects implemented at other sites is frequently the next best source of costs.
Substantial amounts of historical cost data for some components of sediment remediation (e.g., removal, transport, disposal, and residue management) may be available from other project managers.
EPA’s Office of Superfund Remediation and Technology Innovation (OSRTI) can help project managers locate sites where a similar approach has been implemented. Additionally, the project manager may find it useful to refer to the ARCS program’s remediation guidance document (U.S. EPA 1994d) for a discussion on the general elements of cost estimates for sediment sites. This document provides examples of percentages for general costs and site-specific costs for both in-situ and ex-situ remedies. Also, many of the local district USACE offices have extensive experience with dredging and in-water construction and may be an additional source of good cost information.
3.5.2 Operation and Maintenance (O&M) Costs
O&M costs are generally those post-construction costs necessary to ensure or verify the continued effectiveness of a remedial action (U.S. EPA and USACE 2000). These costs may be annual or periodic (e.g., once only, or once every five years). It is important to note that short-term O&M costs generally are incurred as part of the remedial action phase of a project, while long-term O&M costs or long-term cap maintenance generally are part of the O&M phase of a project (U.S. EPA and USACE 2000). At Fund-lead sites, it can be very important to differentiate these two cost categories because CERCLA has specific requirements addressing payment for long-term O&M [CERCLA §104(c))(3)), see Section 3.5.4, State Cost Share]. Some examples of categories that are generally considered short-term
O&M at sediment sites include the following:
C Operation of sediment or water treatment facilities during the remedial action;
C Monitoring, sampling, testing, analysis, and reporting during the remedial action (some may be considered capital costs, see Section 3.5.1 above);
C Maintenance of engineering site controls during shake-down period (e.g., one year);
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Additional issues related to long-term monitoring and maintenance of all three remedial approaches (MNR, capping, and dredging or excavation) are discussed in Chapter 8 of this guidance.
3.5.3 Net Present Value The NCP also provides that an analysis of remedy net present value, or present worth, should be used [NCP §300.430(e)(9)(iii)(G)]. A net present value analysis should be used to compare expenditures occurring over different time periods. This standard methodology allows for a cost comparison of different alternatives having capital, O&M, and monitoring costs that would be incurred in different time periods on the basis of a single cost figure for each alternative. In general, the period of analysis should be equivalent to the project duration, resulting in a complete life cycle cost estimate for implementing the remedial alternative. Past EPA guidance recommended the general use of a 30-year period of analysis for estimating present value costs (U.S. EPA 1988a). Although this may be appropriate in some circumstances, the blanket use of a 30-year period is no longer recommended. Site-specific justification should be provided for the period of analysis selected, especially when the project duration (i.e., time period required for design, construction, O&M, and closeout) exceeds the selected period of analysis (U.S. EPA and USACE 2000).
For sediment approaches that leave significant quantities of contaminated sediment in place, such as in-situ capping or MNR based on natural burial, the actual monitoring period is likely to be longer than 30 years, although project managers are encouraged not to assume that monitoring in perpetuity will be necessary at every site. This is discussed further in Chapter 8, Remedial Action and Long-Term Monitoring.
The discount rate that should be used for this analysis is established by the Office of Management and Budget (OMB). Based on current Agency policy, as reflected in the NCP preamble (55 FR 8722) and the OSWER Directive 9355.3-20, Revisions to OMB Circular A-94 on Guidelines and Discount Rates for Benefit-Cost Analysis (U.S. EPA 1993b), a seven percent discount rate should be used in estimating the present worth value for potential alternatives. This figure could be revised in the future, and project managers should use the current figure contained in an update of the OMB Circular. Project managers should be aware that this rate may not be the same as rates that various potentially responsible parties (PRPs) or federal facilities use for similar analyses. The project manager should refer to A Guide to
Developing and Documenting Cost Estimates for the Feasibility Study (U.S. EPA and USACE 2000) for more information.
3.5.4 State Cost Share At Fund-lead sites, generally the state is responsible under CERCLA for ten percent of remedial action costs and 100 percent of long-term O&M costs (see also 40 CFR §300.510(b) and (c)). Other requirements may apply if the facility was publicly operated at the time of disposal of hazardous substances and for federal facilities. Where O&M costs are significantly different between alternatives, this may add to differences of opinion about preferred alternatives. For the discussion to be based on the best available information, it is especially important that cost estimates be as accurate as possible, including costs of long-term O&M.
After a joint EPA/state inspection of an implemented Fund-financed remedial action, EPA may share, for a period of up to one year, in the cost of the operation of the remedial action to ensure that the remedy is operational and functional (40 CFR §300.510(c)(2)). For sediment sites, this may arise at sites involving in-situ caps and on-site disposal facilities.
The RAOs at sediment sites typically address sediment and biota, but remedies may also include surface water restoration as a goal of the remedial action. The NCP specifies the following in 40 CFR
In the case of the restoration of ground or surface water, EPA shall share in the cost of the state’s operation of ground or surface water restoration remedial actions as specified in 40 CFR §300.435(f)(3).
The NCP at 40 CFR §300.435(f)(3) specifies that:
For Fund-financed remedial actions involving treatment or other measures to restore ground- or surface-water quality to the level that assures protection of human health and the environment, the operation of such treatment or other measures for a period of up to 10 years after the remedy becomes operational and functional will be considered part of the remedial action. Activities required to maintain the effectiveness of such treatment or other measures following the 10-year period, or after remedial action is complete, whichever is earlier, shall be considered O&M.
In 40 CFR §300.435(f)(3) and (4), the NCP also addresses when a restoration activity can be considered administratively “complete” for purposes of federal funding and discusses several actions that are excluded from consideration under this provision.
Where a sediment site includes surface water restoration as a goal, the project manager should consult with their Office of Regional Counsel to determine how these provisions may apply to their site.
3.6 INSTITUTIONAL CONTROLSThe term “institutional control” (IC) generally refers to non-engineering measures intended to affect human activities in such a way as to prevent or reduce exposure to hazardous substances, often by 3-22 Chapter 3: Feasibility Study Considerations limiting land or resource use. ICs can be used at all stages of the remedial process to reduce exposure to contamination. Chapter 7, Remedy Selection Considerations, offers guidance on when it may be appropriate to select a remedy that includes institutional controls at sediment sites and considerations regarding their effectiveness and enforceability. For more detailed information on ICs in general, refer to OSWER Directive 9355.0-74FS-P, Institutional Controls: A Site Manager’s Guide to Identifying, Evaluating, and Selecting Institutional Controls at Superfund and RCRA Corrective Action Cleanups (U.S. EPA 2000f) and Federal Facilities Restoration and Reuse Office (FFRRO) guidance, Institutional Controls and Transfer of Real Property under CERCLA Section 120 (h)(3)(A), (B), or (C) (U.S. EPA 2000g).
As explained in the site managers guide cited above (U.S. EPA 2000f), the following are the four
general categories of ICs: