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June 20, 2013
EPA's proposed UST changes and wastewater treatment tanks

What is a wastewater treatment tank system?

A wastewater treatment tank system is designed to receive and treat influent wastewater through physical, chemical, or biological methods. That means if wastewater flows through a system and is treated in some way, then that system is considered a wastewater treatment tank system. For example, oil-water separators treat wastewater by separating the oil from the water and therefore are wastewater treatment tank systems.

When is a wastewater treatment tank system regulated under the UST regulations (40 CFR 280)?

To determine whether a wastewater treatment tank system is regulated, you need to determine whether the system meets the definition of an UST and whether the system is excluded from the regulations .

  1. Is the wastewater treatment tank system considered an UST system?

    Is 10 percent of the wastewater treatment tank system beneath the surface of the ground?
    To be considered an UST , the tank, including underground piping, must be 120 percent or more beneath the surface of the ground. The term UST does not include the following systems: septic tanks; surface impoundments, pits, ponds or lagoons; stormwater or wastewater collection systems; flow-through process tanks; or liquid traps or associated gathering lines directly related to oil or gas production and gathering operations.
    Does the wastewater treatment tank system contain an accumulation of substances covered under the UST regulation? To be considered a UST system, the system must contain an accumulation of regulated substances.
    Regulated substances are: petroleum that is liquid at standard temperature and pressure, and CERCLA listed hazardous substances. EPA considers petroleum to be a complex blend of hydrocarbons. Examples of petroleum include motor fuel, jet fuel, distillate fuel oils, residual fuel oils, lubricants, petroleum solvents, and used oils. The UST regulation does not apply to substances such as cooking grease or cooking oil because they are not complex blends of hydrocarbons.

  2. Is the UST system currently excluded? This means that none of the UST regulations will apply to the UST system. The current UST rule excludes:
    • Any UST system holding hazardous wastes listed or identified under RCRA Subtitle C, or a mixture of such hazardous waste and other regulated substances
    • Any wastewater treatment tank system that is part of a wastewater treatment facility regulated under the Clean Water Act ( CWA ) Section 307(b) or 402
    • Equipment or machinery that contains regulated substances for operational purposes such as hydraulic lift tanks and electrical equipment tanks
    • Any UST system with a capacity of 110 gallons or less
    • Any UST system that contains a de minimis concentration of regulated substances
    • Any emergency spill or overflow containment UST system that is expeditiously emptied after use

Note that a separate UST used to collect and store regulated substances discharged from the wastewater treatment tank system is currently regulated and will continued to be regulated under the proposed rules.

How is EPA proposing to regulate wastewater treatment tanks systems?

  • Wastewater treatment tank systems that are part of a wastewater treatment facility regulated under the CWA section 307(b) or 402 will continue to be excluded from the UST regulation
  • EPA is proposing to remove the deferral for all other wastewater treatment tank systems, which means those systems would be regulated the same as any other UST systems under the current requirements of 40 CFR 280. In addition to the current requirements, EPA 's proposal includes new secondary containment, operator training, and period operation and maintenance requirements.
wastewater flowchart

Stakeholder Comments

Many stakeholders believe additional clarity and guidance are needed to fully evaluate the possible impacts from the proposed removal of the deferral for wastewater treatment tank systems. Stakeholder comments include:

  • New York DEC commented that EPA should either keep the deferral for wastewater treatment tanks or provide a separate exemption for all oil-water separators.
  • Dow Chemical Company stated that there may be oil-water separators that are not exempted under the CWA sections 307 or 401. These systems are permitted in accordance with the Safe Drinking Water Act (SDWA) in some states but do not appear to be addressed under the CWA . Therefore under the current EPA proposal it appears that these systems would be regulated by the proposed UST regulations and the SDWA. Therefore, the regulatory exemption should be expanded to include systems that discharge to on-site septic systems that are permitted under the SDWA.  In addition, Dow commented that the UST program should not regulate wastewater treatment tanks and oil-water separators that act like ”flow-through tanks.”  Also, the oil pollution section of the CWA would regulate the oil collection and storage part of an oil water separator.
  • Michigan Manufacturers Association (MMA) members have expressed concerned that oil-water separators not permitted under the CWA or SDWA might become regulated under the proposed rule. MMA members report the installation of these types of systems on their storm sewers as a form of secondary containment, as recognized under SPCC, which help prevent the discharge of oil from spills or even such everyday sources as oil in parking lot runoff. Since the system is not required, it would be easier and cheaper to simply remove these systems than bring them into compliance with the proposed rule. In order to promote their continued use and environmental benefit, EPA should continue to defer these types of systems or provide a specific exemption in the proposed rule.



Although EPA downplays the burden and economic impact on owners and operators of systems that were previously deferred from UST regulations , many stakeholders believe these new regulated facilities will face significant financial burdens when the proposed UST rules become final.

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