DECON
DECON Expert
DECON-Expert is an expert system for determining the best practice protocols for response and recovery operations in contaminated water systems.
Source: (2004). Remediation and Recovery Guide. (, Ed.).Module 6, .
Scope of Contamination
The extent to which additional treatment equipment is needed may depend on the location of the contaminated water. For example, when contamination is present in a water source or storage tank upstream of an existing treatment plant, the remedial response may be able to use existing treatment equipment. When contaminated water is present in a distribution system, some consideration should be given to the method which most effectively removes the water for treatment. In some cases, it may be best to avoid draining the system because of fire hazard and the possibility that some empty mains might collapse. In other cases, the contaminated part of the system might be hydraulically isolated from the rest of the system. If system pressure cannot be used to remove the contaminated water, there may be a need to pump the water out. See flushing system for additional discussion of removing contaminated water.[1]
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Treatment Objective
Contaminated water may be present throughout the distribution system or may be isolated to specific areas such as a water source (e.g., reservoir), isolated area of the distribution system, or storage tank. In many cases, this contaminated water may need treatment. The objectives of treatment could be to make the water acceptable for direct use or sanitation or to pretreat the water prior to disposal (see potential disposal requirements).[1]
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No Additional Action Alternative
Under the “no additional action” alternative, no remedial activities would be implemented. Under this alternative, human health and environmental risks are reduced only through attenuation and/or degradation of the contaminant. This may be a realistic alternative in cases where these processes would proceed fast enough to reduce the contaminant concentration to acceptable levels within a reasonable period of time and where an alternate water supply is available during this period (see Section 6 of this module). Even if it is not feasible, the “no-additional-action” alternative provides a baseline for comparing other alternatives.[1]
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Community Acceptance
This assessment reflects the community's apparent preferences for various alternatives, or concerns.[1]
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State (Support Agency) Acceptance
This assessment reflects the state's (or support agency's) apparent preferences for various alternatives, or concerns.[1]
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Cost
This assessment evaluates the capital and O&M costs of each alternative. The level of detail needed to analyze each alternative against these evaluation criteria will depend on the type and complexity of the site, the technologies and alternatives being considered, and other project-specific considerations. The analysis should be conducted in sufficient detail so that decision-makers understand the significant aspects of each alternative and any uncertainties associated with the evaluation (e.g., a cost estimate developed on the basis of a volume of media that could not be defined precisely).[1]
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Generation of Residuals
This criterion involves assessment of the types of air, water, or solid waste impacts resulting from a treatment alternative. Optimally, no treatment residuals will be generated. Examples of treatment residuals for water remediation include spent filter media, regenerant solutions, and off-gas from air strippers. Examples of treatment residuals for water distribution include runoff, flushing solution, and discarded pipe. Treatment residuals may often contain the contaminant of concern. The type, volume, and ease of management of treatment residuals will affect how alternatives are ranked against this criterion.[1]
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Reduction of Toxicity/Infectivity and Mobility Through Treatment
The assessment against this criterion evaluates the reduction of toxicity (or infectivity for pathogens) and contaminant mobility in the water. Treatment processes with the highest reduction of toxicity/infectivity and contaminant mobility rank the highest under this criterion. This evaluation focuses on the remedy employed, the materials being treated, and the expected reduction in toxicity/infectivity and/or mobility.[1]
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Long-term Effectiveness and Permanence
Under this criterion, the evaluation must describe how the alternative provides long-term effectiveness in maintaining protection of human health and the environment after response objectives have been met. This factor assesses the residual risk remaining from untreated waste or treatment residuals at the conclusion of remedial activities and assesses the adequacy and suitability of controls, if any, that are used to manage treatment residuals or untreated wastes that remain at the site.[1]
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Implementability
This assessment evaluates the technical and administrative feasibility of alternatives and the availability of necessary goods and services. This includes consideration of technical difficulties and unknowns with construction and operation of the technology, reliability of the technology, the ability to monitor the effectiveness of the remedy, the need to coordinate with other offices or agencies (e.g., to obtain permits), availability of adequate hazardous waste treatment (if needed), storage and disposal services (if needed), availability of necessary equipment and specialists, availability of service and materials, and the commercial availability of the prospective technologies.[1]
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Compliance with Applicable Regulations
Under this criterion, the evaluation must describe how the alternative complies with applicable regulations, in particular those related to water. Regulatory requirements can be numerous and can include contaminant-based requirements (e.g., MCLs), location-specific requirements (e.g., preservation of historic sites), and action-specific requirements (e.g., for RCRA waste classification).[1]
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Short-term Effectiveness
Under this criterion, the assessment examines the short-term effectiveness of alternatives in protecting human health and the environment during the construction and implementation of a remedy until remediation objectives have been met. Consideration should be given to risks that result from implementation of the proposed remedial action and how these risks may impact the community, workers, and the environment. Risks could be generated, for example, from dust from excavation or from air emissions from stripping towers.[1]
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Overall Protection of Human Health and the Environment
Under this criterion, the evaluation must describe how the alternative achieves and maintains protection of human health and the environment. Assessments of human health and environmental protection are related to other evaluation criteria, especially long-term effectiveness and permanence, short-term effectiveness, and compliance with applicable regulations. Evaluation of the overall protectiveness of an alternative should focus on whether a specific alternative achieves adequate protection and should describe how risks posed through each exposure pathway are eliminated, reduced, or controlled through treatment, engineering, or institutional controls. This evaluation also allows for consideration of any unacceptable short-term or cross-media impacts of an alternative.[1]
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About DECON Expert
DECON-Expert is an expert system comprised of a Geographical Information System, Guidance Documents, Rule-Based Decision Support Tool, and Decontamination Network Model integrated within a Workflow Processor that guides the user through the planning, remediation and recovery process. Each component of Decon-Expert may be executed either independently or interactively within the workflow processor.
