Compliance Corner.


In the United States, hazardous wastes are subject to regulations mandated by the Resource Conservation and Recovery Act (RCRA). Every month, we provide clear, in-depth guidance on a different aspect of the RCRA regulations. The information presented here is an excerpt from McCoy’s RCRA Unraveled, 2018 Edition.

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©2018 McCoy and Associates, Inc. All rights reserved.

Fossil Fuel Combustion Wastes Exclusion

Section 261.4(b)(4) of the federal RCRA regulations excludes fly ash waste, bottom ash waste, slag waste, and flue gas emission control waste from the definition of hazardous waste. These wastes are some of the so-called “Bevill wastes,” temporarily excluded from hazardous waste regulation under the October 1980 Bevill amendment [Section 3001(b)(3)(A)] to the RCRA statute (named after the representative who introduced the amendment in Congress). The three classes of excluded Bevill wastes are:

  1. Fly ash, bottom ash, slag, and flue gas emission control waste from the combustion of fossil fuels [§261.4(b)(4)];
  2. Wastes from the extraction, beneficiation, and processing of ores and minerals [§261.4(b)(7)]; and
  3. Cement kiln dust [§261.4(b)(8)].

Four large-volume fossil fuel combustion wastes

Fly ash, bottom ash, slag, and flue gas emission control waste generated primarily from the combustion of coal or other fossil fuels are what EPA calls the four large-volume fossil fuel combustion (FFC) wastes. These Bevill wastes are specifically excluded from hazardous waste regulation per §261.4(b)(4). Figure 1 illustrates the scope of this Bevill exclusion for these four wastes at a coal-fired power plant.

Figure 1

Although these four wastes were excluded from the definition of hazardous waste in the original May 19, 1980 RCRA regulations [45 FR 33120], Congress required EPA to evaluate whether the temporary Bevill exclusion included in the 1980 regs should continue. After extensively evaluating these waste streams, the agency issued its Report to Congress in February 1988. [EPA/530/SW-88/002, February 1988, available from by downloading the report numbered 530SW88002]

Several years after issuing its Report to Congress, the agency published a final regulatory determination for these wastes on August 9, 1993. [58 FR 42466] In the August 1993 determination, EPA concluded that hazardous waste regulation is inappropriate for these four large-volume FFC wastes. This determination was based on two qualifying criteria; these four wastes are excluded only if they are: 1) generated at coal-fired electric utilities or independent power producers, and 2) managed separately from other FFC wastes. These criteria are incorporated into Figure 2, which is a logic diagram for determining the regulatory status of FFC wastes.

Figure 2 Figure 3

EPA noted that smelter slag is not the same thing as boiler slag (molten bottom ash) and so would not be covered under the §261.4(b)(4) exclusion. Instead, smelter slag might be addressed in the mining and mineral processing waste exclusion at §261.4(b)(7). [RO 12259]

It is fairly clear from guidance [58 FR 42466, RO 11226, 12240] that wastes from a flue gas desulfurization (FGD) system are included in the term “flue gas emission control waste.” What’s less clear is whether spent catalyst and other wastes from a selective catalytic reduction (SCR) system used to control nitrogen oxide (NOx) emissions is included in that term. In limited guidance, EPA has determined that spent SCR catalysts enjoy the §261.4(b)(4) Bevill exclusion. [Performance of Selective Catalytic Reduction on Coal-Fired Steam Generating Units, Final Report, June 25, 1997, available at]

Water from quenching hot bottom ash from a utility boiler picks up the characteristic of corrosivity (pH >12.5). Is the resulting wastewater a hazardous waste subject to RCRA regulation?

No. The quench water becomes corrosive solely as a result of contact with the ash. Because the hazardous waste characteristic of the quench water is derived from an excluded Bevill waste, the resulting corrosive quench water retains the excluded status of that waste. In other words, whatever makes the water corrosive is already excluded, so the water is also excluded from regulation as a hazardous waste. [RO 11145, 11162, 12552]

2015 coal ash rule

From 2009 through 2014, EPA reconsidered its regulatory determination for FFC wastes from power plants. This was driven in part by the failure of a fly ash sludge surface impoundment retaining wall in Kingston, Tennessee in December 2008. On June 21, 2010 [75 FR 35128], EPA proposed two options for regulating FFC wastes from electric utilities and independent power producers under RCRA. The first option was to regulate FFC wastes as listed hazardous waste. The second option was to leave its previous Bevill decision in place. The agency eventually decided on the second option and announced its decision in a final rule published on April 17, 2015. [80 FR 21302]

The final rule established a comprehensive set of requirements for the disposal of FFC wastes from power plants under RCRA Subtitle D. The Subtitle D regulations for FFC disposal units are codified in 40 CFR Part 257 and include structural integrity requirements for surface impoundments, ground water monitoring and corrective action requirements, location restrictions, liner design criteria for new units and lateral expansions, operating requirements, and recordkeeping, notification, and internet posting requirements. A good summary of the Subtitle D requirements for FFC disposal units is given in EPA’s fact sheet on the new rule, available at

State permit programs allowed by RCRA law revisions

The latest action affecting FFC wastes was statutory—not regulatory. In the 2016 Water Infrastructure Improvements for the Nation Act (WIIN Act), Congress modified Section 4005 of the RCRA law so that states are now authorized to manage FFC wastes under their own permit programs. As long as EPA determines (i.e., approves) that the state’s requirements are at least as protective as the federal standards in Part 257, these state programs will operate in lieu of the federal regs.

This statutory change is noteworthy because the 2015 coal ash rule did not give EPA or the states the authority to directly regulate and permit FFC waste disposal, making citizen suits the primary enforcement mechanism. The WIIN Act includes language giving state agencies the authority to implement and enforce the coal ash rule through EPA-approved state permit programs, and it also gives EPA the authority to regulate FFC wastes in states that choose not to implement state permitting programs.

Fossil fuel combustion wastes from other sources

The February 1988 Report to Congress and August 1993 regulatory determination reviewed above did not address FFC wastes from sources other than coal-fired electric utilities or independent power producers. EPA addressed those other wastes in a second Report to Congress, issued in March 1999. [EPA/530/R-99/010, March 1999, available from by downloading the report numbered 530R99010]

In the regulatory determination that followed on May 22, 2000 [65 FR 32214], the agency determined that the following wastes are also Bevill wastes and, although not specifically excluded by the regulatory language in §261.4(b)(4), are excluded from the definition of hazardous waste:

  • Wastes from the combustion of coal at nonutilities (e.g., paper mills, food processing facilities, chemical plants);
  • Wastes from the combustion of coal in fluidized-bed boilers;
  • Wastes from the combustion of petroleum coke;
  • Wastes from the combustion of at least 50% coal with other fuels (e.g., petroleum coke, waste coal, tire-derived fuel) [RO 14452]; and
  • Wastes from the combustion of oil and natural gas.

The regulatory determination for the wastes noted in the above five bullets is consistent with previous EPA guidance. [RO 11007, 12021, 12284, 12884]

Other, low-volume fossil fuel combustion wastes

In addition to the four large-volume FFC wastes discussed above that are excluded from hazardous waste regulation by the specific wording in §261.4(b)(4), facilities that burn fossil fuels generate other wastes, in smaller quantities, from processes that are related to fuel combustion. Many of these low-volume FFC wastes are co-managed/co-disposed with the four large-volume FFC wastes, and so “their composition and character are ‘masked’ by the combustion [sic] and character of the combustion wastes; that is, they do not significantly alter the hazardous character, if any, of the combustion wastes.” [RO 12021] Thus, EPA believes that Congress intended that these low-volume wastes should also be excluded as Bevill wastes under §261.4(b)(4) when they are mixed and co-managed with the four large-volume FFC wastes.

In a 1981 guidance letter [RO 12021], signed by Gary Dietrich of the Office of Solid Waste (hereinafter called the “Dietrich letter”), EPA noted that this extension of the Bevill exclusion was limited to low-volume wastes that are generated in conjunction with the combustion of fossil fuels and that are mixed and co-managed with the four large-volume FFC wastes. Until the agency could complete a more thorough evaluation of the hazardous properties of these other, low-volume wastes or their mixtures with the large-volume wastes, the Dietrich letter stated that the Bevill exclusion was extended to include, but not be limited to, the following wastes:

  • Boiler cleaning solutions,
  • Boiler blowdown,
  • Demineralizer regenerant,
  • Pyrites (coal mill rejects), and
  • Cooling tower blowdown.

However, the Dietrich letter specifically said the following wastes are not excluded under §261.4(b)(4):

  • Pesticide or herbicide wastes,
  • Spent solvents,
  • Waste oils,
  • Other wastes that might be generated in construction or maintenance activities typically carried out at utility and industrial plants,
  • Any hazardous waste listed in §261.31 or 261.32, and
  • Any commercial chemicals listed in §261.33 that are discarded or intended to be discarded.

Years after the Dietrich letter was issued, EPA completed its evaluation of these other, low-volume FFC wastes and issued a March 1999 Report to Congress (cited previously). In a subsequent regulatory determination (May 22, 2000; 65 FR 32214), the agency distinguished between low-volume FFC wastes that were “uniquely associated” with fossil fuel combustion and those that weren’t. EPA defined “uniquely associated” to mean a waste that “during the course of generation or normal handling at the facility, comes into contact with either fossil fuel (e.g., coal, oil) or fossil fuel combustion waste (e.g., coal ash or oil ash) and it takes on at least some of the characteristics of the fuel or combustion waste.” [65 FR 32219] Furthermore, in the May 22, 2000 regulatory determination, EPA proposed a list of wastes that it thought were uniquely associated with the combustion of coal to generate electricity. The list proposed in 2000 did not include all of the wastes that EPA said were covered by the exclusion in the 1981 Dietrich letter.

This inconsistency was resolved in the final FFC rule issued on April 17, 2015. In that rule, EPA codified in §261.4(b)(4) a list of wastes generated from processes that support the combustion of coal or other fossil fuels that, when co-disposed with FFC wastes, are not subject to hazardous waste regulations. These wastes are also referred to as “uniquely associated wastes.” The uniquely associated wastes are:

  • Coal pile run-off,
  • Boiler cleaning solutions (both fire-side and water-side),
  • Boiler blowdown,
  • Process water treatment and demineralizer regeneration wastes,
  • Cooling tower blowdown,
  • Air heater and precipitator washes,
  • Effluents from floor and yard drains and sumps, and
  • Wastewater treatment sludges.

In codifying the above list of uniquely associated wastes, the agency essentially reverted to its position expressed in the 1981 Dietrich letter (RO 12021). Note that these uniquely associated wastes are subject to the hazardous waste regulations when they are not co-disposed with the high-volume FFC wastes. Based on the foregoing discussion, Table 1 summarizes the low-volume FFC wastes that EPA determined are uniquely associated with fossil fuel combustion versus those that aren’t.

Table 1

Low-volume wastes that are not uniquely associated with fossil fuel combustion get no breaks whatsoever. If one of these wastes is managed separately, it is also subject to regulation as hazardous waste if it exhibits a characteristic or is listed. If a nonexcluded waste is mixed and co-managed with one of the Bevill-excluded large-volume FFC wastes, the Bevill exclusion may be lost, depending on application of the Bevill mixture rule (see Figure 3). [65 FR 32220]

Boiler chemical cleaning wastes

Utility boilers are generally cleaned every three years. In a typical scenario, the boiler is cleaned using an acid wash followed by one or more water rinses. The acid wash stream exiting the boiler is often toxic for chromium and lead and also is corrosive. However, the water rinses are usually nonhazardous. The acid wash and water rinses are collected in the same large tank or in interconnected tanks (e.g., interconnected frac tanks). Do the acid wash and water rinses have to be characterized for hazardous waste management individually or after commingling? EPA provided the answer to this question in Federal Register preamble guidance:

“The agency is today clarifying that, specific to power plant boiler cleanout (and potentially, to other sporadic cleaning activities involving multiple rinses), generation is at the completion of the entire cleanout process…. The agency views the cleanout of the boilers as one process and therefore does not consider the mixing of acid rinse and water rinse as impermissible dilution but as a single water rinsate resulting from the single cleanout process. This waste is subject to regulation if it exhibits a characteristic, and subject to LDR prohibitions if it exhibits a characteristic and is going to be land disposed. Today’s clarification of the point of generation for boiler cleanout is limited to the situation in which the entire quantity of boiler cleanout rinses are contained in a single [tank] so that hazardous waste and LDR determinations can be made based upon the commingling of all the rinses together. If, for example, a temporary tank is brought onsite but does not have sufficient capacity to handle the estimated several hundred thousand gallons of rinsate at once, the waste will likely have to be managed in separate loads. In such instances, the generator will still be required to make hazardous waste and LDR determinations for each separate load.” [May 12, 1997; 62 FR 26006–7]

The agency later clarified that this point of generation guidance applies to both permanent and temporary tank systems used to collect boiler cleanout solutions. [May 26, 1998; 63 FR 28623] Note that the last couple of sentences in the above agency quotation imply that, if the rinses are collected in separate permanent or temporary tanks that are not interconnected, the contents of each tank will have to be evaluated to determine if the collected material is hazardous.

After a boiler is chemically cleaned, some unused cleaning fluids remain in the tank trucks. The trucks return to the service company’s facility where they are flushed out with water. Would the resulting washwater qualify as a Bevill waste?

No. The washwater containing unused cleaning fluids from the tank trucks is not excluded. The unused chemicals are not uniquely associated with fossil fuel combustion or steam generation. Thus, they are not excluded, regardless of the intent of their preparation. [65 FR 32220, RO 12021]

Effect of co-burning wastes in boilers

The language in §261.4(b)(4) notes that the Bevill exclusion does not apply to FFC wastes if hazardous waste is burned or processed in the boiler, unless the following criteria in §266.112 are met:

  1. The boiler must burn at least 50% coal on a total heat input or mass input basis; and
  2. The FFC wastes are not significantly affected by the hazardous waste, demonstrated by passing one of the two tests given in §266.112(b).

If these two requirements are satisfied, fly ash, bottom ash, etc. generated from the boiler while hazardous waste is burned or processed continues to be excluded from the Subtitle C program and does not have to meet LDR treatment standards. [58 FR 42469, 63 FR 28574, RO 11881, 12021, 13401, 14344]

EPA expects that there will be no impact on the Bevill status of FFC residues when used oil is co-fired with virgin fuel oil in utility boilers or furnaces. That assessment is based on the used oil comprising <1% of the total fuel mixture and meeting the used oil specification. Thus, the agency believes that the contamination levels in the residues will not be affected by the introduction of small quantities of used oil. [RO 11743]

Beneficial uses of FFC waste

Although significant quantities of FFC waste are disposed, these wastes are often beneficially used:

  • Fly ash is used to make cement/concrete, bricks, and other building products [58 FR 42475, 65 FR 32229, RO 14247];
  • Fly ash can also be used as a stabilizing medium for treatment of heavy metal-bearing wastes before they are landfilled [65 FR 32229, RO 13368];
  • FFC wastes have been used for acid neutralization (e.g., neutralizing wastewater) [65 FR 32229–30];
  • Flue gas desulfurization wastes are a source of synthetic gypsum used in manufacturing gypsum wall board [65 FR 32229, RO 14456];
  • FFC wastes have been used as road bed material, snow and ice control material, structural fill, and blasting grit [65 FR 32229];
  • FFC wastes have also been used as ingredients in insulation, paints, plastics, metals, and roofing materials [65 FR 32229];
  • FFC wastes may be used in agricultural applications (e.g., as a substitute for lime) [58 FR 42475, 65 FR 32229]; and
  • FFC wastes may also be used in the manufacture of absorbents and filter media. [65 FR 32229]

Generally speaking, EPA believes that these on- and offsite beneficial uses of FFC wastes can be conducted outside of the RCRA program. In the August 1993 regulatory determination, the agency noted that FFC waste utilization practices appear to be conducted in an environmentally safe manner. [58 FR 42468] In the May 2000 regulatory determination, EPA concluded that, except for placement of FFC wastes in mines, no RCRA regulation of the beneficial uses of these wastes is necessary. This determination included the use of FFC wastes as an agricultural soil amendment. [65 FR 32229–30, RO 14452, 14453]

The final FFC rule issued in April 2015 maintained the Bevill exclusion from the definition of hazardous waste for FFC wastes that are beneficially used and provided a definition of “beneficial use” to distinguish between beneficial use and disposal. Beneficial use of FFC wastes must meet the following four conditions, per new §257.53:

  1. The FFC wastes must provide a functional benefit;
  2. The FFC wastes must substitute for the use of a virgin material, conserving natural resources that would otherwise need to be obtained through practices such as extraction;
  3. The use of the FFC wastes must meet relevant product specifications, regulatory standards or design standards when available, and when such standards are not available, the FFC wastes are not used in excess quantities; and
  4. When unencapsulated use of FFC wastes involves placement on the land of 12,400 tons or more in non-roadway applications, the user must demonstrate and keep records showing that releases to the environment are comparable to or lower than those from analogous products made without FFC wastes, or that releases will be at or below relevant regulatory and health-based benchmarks for human and ecological receptors.

Under the 2015 final rule, placement of FFC wastes in sand and gravel pits or quarries is considered disposal, not beneficial use.

EPA has developed a website discussing the beneficial reuse of these materials, available at

Importing fossil fuel combustion wastes

Once it enters U.S. jurisdiction, imported FFC waste is excluded from the definition of hazardous waste in the same way as domestically generated FFC waste. This is true regardless of whether the material will be beneficially reused as a cement admixture or disposed in an industrial landfill. [RO 14247] U.S. importers may want to keep records of the foreign exporter and the origin of any imported FFC waste in case questions arise as to its regulatory status once it enters the United States.


Topic: NPDES Discharge Exclusion

©2018 McCoy and Associates, Inc. All rights reserved.


Considerable care has been exercised in preparing this document; however, McCoy and Associates, Inc. makes no representation, warranty, or guarantee in connection with the publication of this information. McCoy and Associates, Inc. expressly disclaims any liability or responsibility for loss or damage resulting from its use or for the violation of any federal, state, or municipal law or regulation with which this information may conflict. McCoy and Associates, Inc. does not undertake any duty to ensure the continued accuracy of this information.

This document addresses issues of a general nature related to the federal RCRA regulations. Persons evaluating specific circumstances dealing with the RCRA regulations should review state and local laws and regulations, which may be more stringent than federal requirements. In addition, the assistance of a qualified professional should be enlisted to address any site-specific circumstances.