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A framework for evaluation
The decision on how to clean-up a site can be divided into several successive phases. The first decision is that of whether a polluted site needs to be cleaned up. If remediation is not necessary, then the investigations can be stopped. Otherwise, the investigations should be focused on the screening of the suitable remedial strategies. The criteria which will influence this last decision are:
- the total impact of remediation strategy on the total risk for humans, ecosystem and infrastructures;
- the total impact of the remediation strategy on scarce commodities, such as soil, ground water, drinking water, space and energy, and on the quality of the environment as a whole;
- the total impact of the remediation strategy and method on the financial assets of the problem owner.
This perspective is the closest to the original evaluation framework aiming at multifunctionality. The environmental merit perspective, stemming from a Life Cycle Inventory approach, aims at minimizing the use of scarce commodities and the contamination of other compartments due to remedial activities. The costs perspective aims at minimizing the total costs in terms of net present value. The methodology aims at producing, for each cleaning-up option, a set of 3 indices: the amount of risk reduction achieved by the remediation; the environmental balance of the operations and the costs involved. Risk reduction is based on the computation of the overall exposure of people, ecosystems and other targets (e.g. workers on the site during remediation) and at the comparison of the exposure levels with acceptability standards. Risks are computed during all phases of the operations, leading to a time-dependent profile of the risk attenuation process. By compating this to the risk profile of the status quo, the amount of risk reduction can be computed. Environmental merit is based on the computation of an additive index for multiple environmental consequences of soil remediation. The non-local positive and negative outcomes of soil clean-up are weighted and summed up leading to an indication of the environmental performance of the operations. These are compared again to the status quo. The index is here measured in Environmental merit Units. Finally, the costs include all expenses involved in the operations, including asset costs. Costs are computed yearly for the full length of the operations. The Net Present Value is then used as an estimate of the total costs. Each cost item is the sum of the expected expenses in a given period plus a safety quantity to guarantee that the real costs will have only a limited probability of exceeding the computed costs.
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Issues in soil remediation
Multifunctionality has proven very difficult to achieve in practice. About 50 per cent of the clean-up soil does not meet the multifunctionaluity target and has to be used under additional constraints.
Achieving miltifunctionality may be hampered by the cost of the operations and by technical and feasibility constraints. Technology for soil remediation is developing very quickly with a shift from radical, hard solutions (such as excavate-pump-and- treat) to biological techniques which, for instance, exploit natural attenuation phenomena. However, the costs issues are still a mayor constraint to soil remediation. High costs have become both politically indefensible, and economically unfeasible. Facing sheer expenditures, companies have often applied a wait-and-see attitude, delaying the operations as much as possible often exploiting the ambiguities of the guideline and the possibility of some discretionary interpretation of the law. The main issue raised by the private sector is that the multifunctionality objective systematically disregards efficiency and effectiveness considerations. Most companies do know what the future use of contaminated sites will be, and thus question the general principle that all sites should be cleaned-up to the same extent. An industrial area may need less strict measures than a residential one. In addition, the application of soft, but long, remediation techniques may significantly cut costs, although may delay the soil usage and leave many sites polluted for a considerable time.
Although the cost-related matters are clear, the multifunctionality objective may also raise some environmental concerns. Scientists consider multifunctionality as the soil-related interpretation of sustainability. An implicit, and almost universal, assumption is that by cleaning-up a polluted site (or rehabilitating any degraded area) there is a net environmental benefit. Growing evidence has been provided that suggests that this assumption should be challenged and that the overall environmental balance of remediation may not be always positive. By considering the full cycle of the remediation process, it can be recognized that the process requires the use of natural resources like energy and clean water, and may result into a transfer of pollution to other environments, for instance by creating air pollution, water pollution and waste. The soil remediation thus raises two types of environmental concerns:
1. A local, site specific concern, related to the need of reducing contamination below some safe level. This is clearly the positive site of the coin, in the sense that soil remediation provides a net local benefit.
2. A regional or even global concern, related to the need of minimizing the use of scarce resources during the operations and the spread and transfer of pollution to other environments. These factors are the negative side of the remediation and cannot be disregarded in computing the full environmental balance of remediation.
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