Frequent Questions

A generator removed economizer tubes contaminated with fly ash from a boiler burning #6 fuel oil during routine maintenance. Are the economizer tubes excluded from the definition of hazardous waste under §261.4(b)(4)?

On May 22, 2000, EPA determined that the regulation of fossil fuel combustion (FFC) waste under Subtitle C of RCRA was not warranted. This determination included wastes from the combustion of oil (65 FR 32214, 32215). The fossil fuel combustion exclusion from the definition of hazardous waste is codified at §261.4(b)(4). There is no federal clarification on whether #6 fuel oil is specifically included under this exclusion. 

Wastes that come into contact with fossil fuel combustion waste during the course of generation or normal handling at the facility and take on at least some of the characteristics of the fuel or combustion waste are known as “uniquely associated'' wastes (65 FR 32214, 32219; May 22, 2000). If the fly ash is excluded, the economizer tubes may be considered uniquely associated waste. When uniquely associated wastes are co-managed with fossil fuel combustion wastes, they fall within the scope of the exclusion. When managed separately, uniquely associated wastes are subject to regulation as hazardous waste if they are listed wastes or exhibit a characteristic of a hazardous waste. Wastes that are not uniquely associated with fossil fuel combustion are subject to the RCRA characteristic standards and hazardous waste listings (65 FR 32214, 32219; May 22, 2000). 

Whether a waste is uniquely associated with fossil fuel combustion involves a site specific determination. Absent unusual site-specific circumstances, EPA generally considers uniquely associated wastes to include coal rile runoff, coal mill rejects and waste coal, air heater and precipitator washes, floor and yard drains and sumps, wastewater treatment sludges, and boiler fireside chemical cleaning wastes. Examples of wastes that are typically not uniquely associated include boiler blowdown, cooling tower blowdown and sludges, intake or makeup water treatment and regeneration wastes, boiler waterside cleaning wastes, laboratory wastes, general construction and demolition debris, and general maintenance wastes (65 FR 32214, 32220; May 22, 2000). 

Additional guidance regarding the hazardous waste exclusion for fossil fuel combustion wastes is available in the following documents: 

Memo, Cotsworth to Citizen; October 10, 2000 (RCRA Online #14494
Memo, Fields to Thomas; June 26, 2000 (RCRA Online #14456
Memo, Cotsworth to Condit; June 9, 2000 (RCRA Online #14452
Memo, Williams to Weinreich; April 21, 1986 (RCRA Online #11145
Monthly Call Center Report Question; February 1986 (RCRA Online #12552
Memo, Lehman to Teisler; August 16, 1984 (RCRA Online #12284
Monthly Call Center Report Question; June 1984 (RCRA Online #12240
Memo, Dietrich to Elmer; January 13, 1981 (RCRA Online #12021)

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