Site contamination generally results from leakage, spillage, or disposal of industrial wastes, and can arise from the past uncontrolled disposal of chemical wastes or any recent negligence. Contaminated sites are a threat to human beings by the following means of contamination:
1. Contact with contaminated soil
2. Inhalation of evaporated toxic gases
3. Drinking of contaminated groundwater
4. Consumption/intake of a secondary contaminant, for example, by eating contaminated crops or livestocks fed in the contaminated area
The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA)1-3 and the Superfund Amendments and Reauthorization Act (SARA)4 protect the public from the risks created by past and recent chemical disposal practices. Cleanup of contaminated sites is needed in order to protect human and natural resources, as defined by the Clean Air Act,5 the Clean Water Act,6 the Safe Drinking Water Act,7 and the Resource Conservation and Recovery Act (RCRA).8,9
This chapter presents a regulatory overview of on-site remediation, remedial investigations (RI), feasibility studies (FS), remedial technologies, and a simulated case study. The discussion of remedial investigations and feasibility studies also includes the development and selection of remedial technologies. The case study outlines a remedial investigation and feasibility study, as well as the selection of remedial technologies.
16.2 LEGISLATIVE AND REGULATORY OVERVIEW
16.2.1 Comprehensive Environmental Response, Compensation, and Liability Act
In 1980, the U.S. Congress enacted the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA), the first comprehensive federal law addressing the protection of the environment from the threat of hazardous substances. The primary goal of CERCLA is to establish an organized cost-effective mechanism for response to abandoned or uncontrolled hazardous waste sites that pose a serious threat to human health and the environment.8,9 To accomplish this goal, two types of response capabilities are mandated by CERCLA1-3:
1. An emergency response action for handling major chemical spills or incidents requiring immediate action, usually only at the surface of a site (e.g., to avert an explosion, to clean up a hazardous waste spill, or to stabilize a site until a permanent remedy can be found); these action are limited to 12 months or USD 2 million in expenditure, although in certain cases these limits may be extended.
2. A remedial response capability for undertaking the long-term cleanup of abandoned hazardous waste disposal sites. These remedial actions represent the final remedy for a site and are generally more expensive and of a longer duration than emergency removals. The U.S. Environmental Protection Agency (U.S. EPA) deals only with remedial actions for hazardous waste sites that are on the National Priorities List (NPL).
Both removal and remedial actions may be carried out at the same site. To accomplish these tasks, CERCLA has given cleanup authority to U.S. EPA, has established the Hazardous Substance Response Trust Fund (Superfund) to finance the remedial actions at CERCLA sites, has initiated a procedure for the emergency response to accidental spills, and has imposed cleanup liability on those responsible. The National Contingency Plan (NCP) was developed in 1982 and in 1985 as the regulatory framework to guide these responses.
Preliminary assessments have been conducted at more than 31,000 sites reported as possible sources of contamination. In 1990 there were over 1100 sites (presenting the greatest health risk and hence eligible for Superfund reimbursement) on the NPL.8,9 The NCP has outlined the level of cleanup necessary at Superfund sites and established the basic procedures that have to be followed for the discovery, notification, response, and remediation of the hazardous waste sites.10
16.2.2 Superfund Amendments and Reauthorization Act (SARA)
SARA has added several important new dimensions to CERCLA, including an increased emphasis on health assessments and the consideration of air releases.11
It should be noted that early remedial actions for contaminated soil consisted primarily of excavation and removal of the contaminated soil from the site and its disposal at a landfill. SARA strongly recommends on-site treatment that permanently and significantly reduces the volume, toxicity, or mobility of hazardous substances, and utilizes cost-effective permanent solutions. The legislation prohibits land disposal of hazardous wastes unless U.S. EPA determines otherwise (as in the Hazardous and Solid Waste Amendments, HSWA).
SARA requires that remedial actions meet all applicable or relevant federal standards or any more stringent state standards. Nine criteria that need to be met are set by CERCLA as amended by SARA for a complete assessment of treatment alternatives applicable for a site remedial action12:
1. The overall protection of human health and the environment by permanently and significantly reducing the volume, toxicity, or mobility of hazardous substance, pollutants, and contaminants
2. Compliance with applicable, relevant, and appropriate requirements (ARARs)
3. Long-term effectiveness and permanence
4. Reduction of toxicity, mobility, or volume
5. Short-term effectiveness
8. State acceptance
The CERCLA reauthorization regards off-site transport and disposal without treatment as the least favored alternative where practicable treatment technologies are available. It also favors the use of permanent solutions and alternative treatment technologies or resource recovery technologies and using them to the maximum extent practicable.
16.2.3 Resource Conservation and Recovery Act (RCRA)
RCRA has a regularity focus (in contrast to CERCLA, which has a response focus), and authorizes control over the management of wastes from the moment of generation until final disposal, including transportation, storage, and other processes.
16.3 OVERVIEW OF REMEDIAL STRATEGIES AND PHASES
The remedial strategies include the following:
1. Site selection from the NPL
3. Remedial investigation including site characterization and a treatability study
4. Feasibility study including analysis and selection of alternatives
5. Remedial design and action (see Figure 16.1)12
The remedial strategies of concern focus on how to select a remedial method and how to complete the remediation at the most effective cost.
Scoping is the prework for RI and FS study. The task of scoping consists mainly of site data collection. As this is required for the RI phase, some investigators have regarded scoping as an early subphase of RI. However, scoping also involves project planning and other prework for FS, so it is to be regarded as a separate phase that precedes both RI and FS.
16.3.2 Remedial Investigation/Feasibility Study (RI/FS)
In accordance with §105 of CERCLA, U.S. EPA has established a process for locating releases, evaluating remedies, determining the appropriate extent of response, and ensuring that the remedies selected are cost-effective. This process is commonly referred to as the RI/PS process. The overall purpose of the RI/PS process represents the methodology that the Superfund program has established for characterizing the nature and extent of the risks posed by uncontrolled hazardous waste sites and for evaluating their potential remedial options.
The NCP requires that a detailed RI/PS be conducted for every site that is targeted for remedial response action under §104 of CERCLA.
Figure 16.2 outlines the major tasks carried out in the RI/FS process under CERCLA guid-ance.13 The components of RI comprise the following:
1. Collecting data to characterize site conditions
2. Determining the nature of the waste
Remedial options Negotiations document
Site map Interim report
Side background Nature of problem Event of problem History of response
QA/QCplan Health and safety plan Management plan Sampling plan Community relations plan Data management plan
SOW for bench and pilot scale tests
Model statement of work for remedial investigations
Task # 1 Description of current situation Task #2 Plans to management
Task #3 Site investigation Task #4 Site investigation analysis
Task #5 Laboratory & bench scale studies Task #6 Reports
Task #7 Community relations support
FIGURE 16.2 RI/FS process.
Task #8 Description of proposed response Task #9 Preliminary remedial technologies Task #10 Development of alternatives Task #11 Initial screening of alternatives
Task #12 Evaluation of alternatives Task #13 Preliminary report Task #14 Final report Task #15 Additional requirements
Peal closure plan Compliance monitoring schedule Administrative reports Document content
3. Assessing risk to human health and the environment
4. Conducting treatability testing as necessary to evaluate the potential performance and cost of the treatment technologies that are being considered12,13
The components of FS comprise developing, screening, and evaluating alternative remedial actions.
RI and FS are interdependent processes and are generally performed concurrently rather than sequentially, although the FS uses the data provided by the RI. This approach should be viewed as a dynamic, flexible process that can and should be tailored to specific circumstances of individual sites. It is not a rigid step-by-step approach that must be conducted identically at every site. Figure 16.3 illustrates a generic timeline of the phasing of RI/PS activities.
16.4 SCOPING THE REMEDIAL INVESTIGATION AND
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