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 (1) Trenholm 1986 (eight full-scale hazardous waste incinerators)
 (2) Dellinger 1988 (turbulent flame laboratory reactor)
 (3) Trenholm 1987 (full-scale rotary kiln incinerator)
 (4) Chang 1988 (turbulent flame laboratory reactor)
 (5) US EPA "PIC database" in US EPA 1989b (review of available data at varied units)
 (6) US EPA 1987c (two full-scale rotary kiln incinerators) Costner and Thornton 1990, page 25

ARAR = Applicable or relevant and appropriate requirements
TBC = To-be-considered

http://www.epa.gov

Table 6 - Conservative Estimates of Metals Partitioning to Flue Gas
as a Function of Solids Temperature and Chlorine Content*

Source of data: EPA 1989

* The remaining percentage of metal is contained in the bottom ash. Partitioning for liquids is estimated at 100% for all metals. The combustion gas temperature is expected to be 100°F - 1000°F higher than the solids temperature.
 †Cl = Chlorine.

 

Table 7 - Metal Volatility Temperatures

Source of data: Original data by Dr. Randy Seeker of EER Corporation,
under contract to EPA (used with permission).

 

Table 8 - Air Pollution Control Devices and their Conservatively Estimated
Efficiencies for Controlling Metals

* Wet scrubber includes Sieve Tray Tower, Packed Tower, and Bubble Cap Tower. EPA 1989
†It is assumed that flue gases have been pre-cooled in a quench before the PS. If gases are not cooled adequately,  mercury recoveries will diminish, as will cadmium and arsenic to a lesser extent. A number of proprietary wet  scrubbers have come on the market in recent years that are highly efficient on both particulates and corrosive gases.  Two such units are offered by Calvert Environmental Equipment Co. and by Hydro-Sonic Systems, Inc.
 ‡An IWS is nearly always used with an upstream quench and packed horizontal scrubber.
ATSDR Note: One commenter said a facility has reported 50-60% mercury removal by their ESP.

Table 9 - Design Considerations

Figure 1. Incineration Subsystems and Typical Process Components

Figure 2. Thermal Desorption Systems

The public health review process is covered extensively in the ATSDR Public Health Assessment Guidance Manual and other agency policies and procedures. This appendix briefly summarizes the public health review process for readers who might not be familiar with ATSDR policies and procedures. This document does not replace other ATSDR guidance or imply that matters not specifically covered in it are not important.

ATSDR's mission is to prevent harmful exposures and disease related to toxic substances associated with exposure to hazardous substances from waste sites, unplanned releases, and other sources of pollution present in the environment. Under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), also known as Superfund, ATSDR is charged with evaluating potential public health hazards resulting from exposure to toxic substances found at National Priorities List (NPL) sites, federal hazardous waste sites, sites of unplanned releases, and sites where ATSDR has been petitioned by concerned individuals or organizations, such as Tribal Nations or other federal, state, and local government agencies.

ATSDR's public health review process, also called the health assessment process, encompasses many key elements of the Agency's mission. The purpose of a public health assessment is to determine whether people have been, are being, or will be exposed to hazardous substances and, if so, whether that exposure is harmful and what actions need to occur to stop or reduce exposures. In conducting public health assessments, ATSDR obtains and evaluates information on the releases of toxic substances into the environment, the media contaminated, the concentration of contaminants, the routes of exposure, and the public health implications of those exposures. This initial step of data collection involves numerous organizations such as EPA, US Geological Survey, state health and environmental agencies, county and local health offices, and communities. ATSDR evaluates available health outcome data, and community health concerns in determining the threat caused by the site. After assessing the information available, ATSDR draws conclusions about the health concern posed by the site and makes recommendations for follow-up actions that address those concerns. The Agency strives to address health issues associated with all exposed populations, including those who might be uniquely vulnerable such as children, tribal populations, or those in compromised health conditions.

• Collecting site information, including environmental and health data and community concerns
  
  
• Identifying and evaluating exposures, based on environmental contamination data, exposure pathway (e.g., air, water, soil, food) information, and any available health outcome (e.g., health studies) data
  
  
• Determining public health implications for exposed populations
  
  
• Drawing conclusions and making recommendations
  
  
• Formulating a public health action plan

A public health assessment generally does not generate new information, but rather involves a review of already existing health and environmental data. However, based on the data needs, ATSDR sometimes recommends that an exposure investigation be conducted to fill the data needs. Exposure investigations might be environmental sampling, biological sampling, or dose-reconstruction activities. The results of an exposure investigation are incorporated into the public health assessment or health consultation document.

Community outreach is another important part of the public health review process, with three primary purposes:

ATSDR engages the public early and maintains communication throughout the public health assessment process. ATSDR community outreach activities include

• Holding public meetings and availability sessions.
  
  
• Distributing fact sheets.
  
  
• Establishing and maintaining information repositories.
  
  
• Issuing press releases.
  
  
• Conducting mailings.
  
  
• Posting information on its Web site.
  
  
• Responding to public comments.

The findings of the public health assessment process might be reported in a variety of different types of reports, including

• A health advisory is a statement from ATSDR Administrator to the Administrator of the EPA containing a finding that a release of a hazardous substance or physical conditions poses a significant risk to human health and recommending measures to be taken to reduce exposure and eliminate or substantially mitigate the significant risk to human health.
  
  
• A public health assessment provides an evaluation of data and information on the release of hazardous substances into the environment in order to assess any past, current, or future impact on public health, makes recommendations, and identify studies or actions needed to evaluate and mitigate or prevent human health effects. All public health assessments contain five essential elements. They are: 1) nature and extent of contamination, 2) pathways of human exposure, 3) demographics, 4) public health implications, and 5) comparison of morbidity and mortality statistics - if appropriate.
  
  
• A health consultation, which provides advice or addresses specific requests for information about site-specific health risks related to a particular exposure pathway or substance. These consultations are intended to focus on a specific issue and recommend specific actions as needed.

• Contains ATSDR policies and procedures for conducting health assessments,
  
  
• Provides detailed steps for conducting a comprehensive assessment of hazardous waste sites, and
  
  
• Contains guidance on preparing a report that documents the agency's actions, conclusions, and recommendations.

The guidance manual is available on the ATSDR web site at http://www.atsdr.cdc.gov.

Appendix E - Applicable or Relevant and Appropriate Requirements
(ARARs)

ARARs Selection Process

The RCRA, Superfund & EPCRA Hotline Training Module - Introduction to: Applicable or Relevant and Appropriate Requirements provides the following discussion of ARARs (EPA 1998a). Table 5 shows the ARAR identification process.

CERCLA §121(d) specifies that on-site Superfund remedial actions must attain federal standards, requirements, criteria, limitations, or more stringent state standards determined to be legally applicable or relevant and appropriate to the circumstances at a given site. Such ARARs are identified during the remedial investigation/feasibil-ity study (RI/FS) and at other stages in the remedy selection process. For removal actions, ARARs are identified whenever practicable depending upon site circumstances. To be applicable, a state or federal requirement must directly and fully address the hazardous substance, the action being taken, or other circumstance at a site. A requirement which is not applicable may be relevant and appropriate if it addresses problems or pertains to circumstances similar to those encountered at a Superfund site. While legally applicable requirements must be attained, compliance with relevant and appropriate requirements is based on the discretion of the Remedial Project Manager (RPM), On-Scene Coordinator (OSC), or state official responsible for planning the response action (p. 3)[emphasis in original]....

The scope and extent of ARARs that may apply to a Superfund response action will vary depending on where remedial activities take place. For on-site response activities, CERCLA does not require compliance with administrative requirements, of other laws. CERCLA requires compliance with only the substantive elements of other laws, such as chemical concentration limits, monitoring requirements, or design and operating standards for waste management units for on-site activities. Administrative requirements, such as permits, reports, and records, along with substantive requirements, apply only to hazardous substances sent off site for further management. The extent to which any type of ARAR will apply also depends upon where response activities take place. Applicable requirements are universally applicable, while relevant and appropriate requirements only affect on-site response activities (p. 3)....

During on-site response actions, ARARs may be waived under certain circumstances. In other cases, the response may incorporate environmental policies or proposals that are not applicable or relevant and appropriate, but do address site-specific concerns. Such to-be-considered (TBC) standards may be used in determining the cleanup levels necessary for protection of human health and the environment (p. 4)[emphasis in original]....

ARARs must be identified on a site-by-site basis. Features such as the chemicals present, the location, the physical features, and the actions being considered as remedies at a given site will determine which standards must be heeded (p. 4)....

ARARs are used in conjunction with risk-based goals to govern Superfund response activities and to establish cleanup goals. EPA used ARARs as the starting point for determining protectiveness. When ARARs are absent or are not sufficiently protective, EPA uses data collected from the baseline risk assessment to determine cleanup levels. ARARs thus lend structure to the Superfund response process, but do not supplant EPA's responsibility to reduce the risk posed by a Superfund site to an acceptable level (p. 4).

...[F]or on-site activities, CERCLA requires compliance with both directly applicable requirements (i.e., those that would apply to a given circumstance at any site or facility) and those that EPA deems to be relevant and appropriate (even though they do not apply directly), based on the unique conditions at a Superfund site (p. 4)....

Environmental laws and regulations fit (more or less) into three categories: 1) those that pertain to the management of certain chemicals; 2) those that restrict activities at a given location; and 3) those that control specific actions. There are therefore three primary types of ARARs. Chemical-specific ARARs are usually health- or risk-based restrictions on the amount or concentration of a chemical that may be found in or discharges to the environment. Examples include RCRA land disposal restrictions (LDR) treatment standards and SDWA [Safe Drinking Water Act] maximum contaminant levels (MCLs). Location-specific ARARs prevent damage to unique or sensitive areas, such as flood plains, historic places, wetlands, and fragile ecosystems, and restrict other activities that are potentially harmful because of where they take place.... Action-specific ARARs are activity or technology based. These ARARs control remedial activities involving the design or use of certain equipment, or regulate discrete actions (p. 5 - 6)....

The types of legal requirements applying to Superfund responses will differ to some extent depending upon whether the activity in question takes place on site or off site (the term "on site" includes not only the contaminated area at the site, but also all areas in very close proximity to the contamination necessary for implementation or the response action). Superfund responses must comply with all substantive requirements that are "applicable" or "relevant and appropriate." Off site, compliance is required only with applicable requirements, but both substantive and administrative compliance are necessary (p. 6)....

Congress limited the scope of EPA's obligation to attain administrative ARARs through CERCLA §121(e), which states that no federal, state, or local permits are required for on-site Superfund response actions. This permit exemption allows the response action to proceed in an expeditious manner, free from potentially lengthy delays associated with the permit process.... Only the substantive elements of other laws affect on-site responses. Examples of substantive requirements include concentration limits for chemical emissions or discharges and specifications for the design and operation of remediation equipment (p. 7)....

Removal actions must attain ARARs to the extent practicable, considering site-specific circumstances, including the urgency of the situation, the scope of the removal action, and the impact of ARARs on the cost and duration of the removal action (§300.415(j)). The OSC would not, for example, have to stop to identify ARARs prior to removing potentially explosive munitions discovered in a residential area, or comply with an ARAR that would cause the removal action to exceed the statutory 12 month, $2 million limits. OSCs must document why certain ARARs are not practicable for emergency removal actions, but should strive to implement those ARARs that are most crucial to the protection of human health and the environment (p. 8)....

Since conditions vary widely from Superfund site to Superfund site, ARARs alone may not adequately protect human health and the environment. When ARARs are not fully protective, EPA may implement other federal or state policies, guidelines, or proposed rules capable of reducing the risks posed by a site. Such TBC standards, while not legally binding (since they have not been promulgated), may be used in conjunction with ARARs to achieve an acceptable level of risk.... Because TBCs are not potential ARARs, their identification is not mandatory (p. 8)....

When ARARs and TBCs do not specify a particular remedy, EPA has the discretion to choose the best remedial alternatives. EPA prefers to use active control measures, such as treatment, to eliminate the principal threats posed by a Superfund site. If active measures are not practicable or cost-effective, institutional controls, such as restrictions on site use or access, or engineering controls, such as waste containment, may be used to prevent exposure to hazardous substances (§300.430(a)(iii)) (p. 8)....

Congress also identified certain circumstances under which a law or regulation that would normally be an ARAR may be waived in favor of another protective remedy (CERCLA §121(d)(4) and 40 CFR §300.430(f)(1)(ii)(B)). The following six types of "ARARs waivers" may be invoked during a remedial action (p. 19)....

An ARAR may be temporarily waived to implement a short-term alternative, or interim measure, provided that the final remedy will, within a reasonable time, attain all ARARs without causing additional releases, complicating the response process, presenting an immediate threat to public health or the environment, or interfering with the final remedy (p. 20)....

An ARAR may be waived if compliance with the requirement will result in greater risk to human health and the environment than noncompliance. It might, for example, be riskier to meet an ARAR calling for dredging of a riverbed to remove PCB-contaminated sediments, and in so doing release PCBs into the river, than to leave the contaminated sediments in place (p. 20).

An ARAR may be waived if it is technically impracticable from an engineering standpoint, based on the feasibility, reliability, and cost of the engineering methods required. It is, for example, often technically impracticable to remove from a drinking water aquifer dense, nonaqueous phase liquids (DNAPLs) trapped in deep bedrock fractures (p. 20)....

An ARAR may be waived if an alternative design or method of operation can produce equivalent or superior results, in terms of the degree of protection afforded, the level of performance achieved, long-term protectiveness, and the time required to achieve beneficial results (p. 20)....

A state ARAR may be waived if evidence exists that the requirement has not been applied to other sites (NPL or non-NPL) or has been applied variably or inconsistently. This waiver is intended to prevent unjustified or unreasonable state restrictions from being imposed at CERCLA sites (p. 20).

An ARAR may be waived if compliance would be costly relative to the degree of protection or risk reduction likely to be attained and the expenditure would jeopardize remedial actions at other sites. The lead Agency should consider the fund-balancing waiver when the cost of attaining an ARAR is 20 percent or more of the annual remedial action budget or $100 million, whichever is greater (p. 21)....

When an alternative that does not attain an ARAR is chosen, the basis for waiving the requirement must be fully documented and explained in the ROD [Record of Decision].... The lead Agency may therefore include a contingent ARAR waiver(s) in the ROD, by specifying specific contaminant levels or circumstances that will trigger the waiver (p. 21).

This page last updated on April 15, 2002

Lateefah A. Wooten / lpw1@cdc.gov

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