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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, 2020 Edition.

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90/180/270-Day Accumulation

The regulatory provisions that allow generators to accumulate wastes without a permit are codified in §262.16 for SQGs and §262.17 for LQGs. VSQG wastes are exempt from most RCRA requirements per §262.14.

EPA used the 2016 generator improvements rule to clarify which generator requirements have to be met for an SQG or LQG to be exempt from the requirement to obtain a storage permit versus those that are independent of that exemption. In the same rule, the agency clarified which requirements a VSQG has to meet to be exempt from most hazardous waste management regulations. EPA separated the conditions for an exemption from the independent requirements as follows:

  • Conditions for exemption—These are regulatory requirements primarily associated with satellite and 90/180/270-day accumulation areas that must be met for the generator to be exempt from the requirement to obtain a storage permit. Examples include hazardous waste container and tank standards, preparedness and prevention requirements, and personnel training provisions. Failure to comply with any of these conditions may result in the generator being charged with operating a non-exempt storage facility and potentially with noncompliance with the many permitting or interim status facility provisions in Parts 124, 264 through 268, and 270. Such noncompliance is subject to penalty (e.g., a notice of violation and/or civil or criminal penalty) and injunctive relief under RCRA Section 3008. The conditions for exemption are codified in §§262.14–17.

“It has been the agency’s long-standing position that generators that do not comply with a condition of a generator exemption fail to qualify for the exemption and (if they have not qualified for a larger generator exemption) they would be considered an operator of a non-exempt storage facility, in addition to being a generator.” [81 FR 85746]

  • Independent requirements—These are regulatory requirements that are applicable and enforceable and that are not legally tied to the accumulation of hazardous waste. They are “independent” of the conditions for exemption from regulation as a storage facility. Examples include determining the category (VSQG, SQG, LQG) into which the generator falls, using a manifest to ship hazardous waste offsite, and most recordkeeping. Failure to meet an independent requirement will likely result in some form of enforcement action for violating that particular requirement (e.g., a notice of violation, civil or criminal penalty, or injunctive relief under RCRA Section 3008). The independent requirements are codified in §262.10(a)(1). Table 1 lists the independent requirements for the three generator categories.
Table 1

Regulatory history

The provisions allowing LQGs to accumulate wastes for up to 90 days without a permit date back to the very beginning of the RCRA regulatory program. [May 19, 1980; 45 FR 33141] This so-called “90-day accumulation rule” originally provided manufacturers with a means to accumulate sufficient quantities of waste for onsite or offsite management without having to deal with burdensome permitting requirements. EPA justified this accumulation period as being necessary to ensure that the RCRA regulations did not interfere with industry’s production processes.

On March 24, 1986 [51 FR 10146], EPA issued regulations applicable to SQGs. Because it takes longer for generators in this category to accumulate enough wastes for efficient treatment or disposal, they are allowed up to 180 days to accumulate wastes without a permit. If the waste is transported 200 miles or more for offsite treatment, storage, or disposal, the accumulation period extends to 270 days.

Summary of accumulation standards

Table 2 summarizes the hazardous waste accumulation requirements for large and small quantity generators. Note that many minor, but important, differences exist between the requirements applicable to these two groups.

Table 2

Allowable facilities

The 90/180/270-day accumulation provisions apply to the original generator of the waste; hence, these units are typically located at generator sites.

A word of caution is in order regarding generator sites and the 90-day accumulation provisions. Let’s assume that a contractor is conducting remediation at a site that is not part of a treatment, storage, or disposal (TSD) facility or a RCRA generator’s site. Can the contractor put hazardous remediation wastes in roll-off boxes and store the wastes on the site for up to 90 days without a permit?

The answer is “Yes,” if all of the provisions of §262.17 are met. The problem arises with the need to comply with the requirements for preparedness and prevention, the standards for a contingency plan and emergency procedures, and the training provisions. Does the emergency equipment specified in §262.252 exist at the roll-off box accumulation area? Is a communication system per §262.254 available? Have arrangements with local emergency response authorities been made per §262.256? Is there a written contingency plan for the area (§262.260)? Is a copy of this plan maintained at the site, and has it been sent to local emergency response organizations (§262.262)? Is an emergency coordinator either at the site or on call at all times (§262.264)? Have all of the contractor’s field personnel been trained in accordance with §262.17(a)(7) requirements?

If a permitted or interim status TSD facility generates its own hazardous wastes (e.g., as treatment residues), they may also utilize the 90/180/270-day accumulation provisions. [December 31, 1980; 45 FR 86969, RO 12865] At permitted TSD facilities, these accumulation areas should appear on the facility map. [RO 12075] A sign or notice should be posted in a visible location to distinguish the 90/180/270-day area from permitted storage/treatment areas; construction of a 90/180/270-day accumulation area would not require modification of the facility’s storage permit. [RO 12471] TSD facilities cannot utilize the 90/180/270-day accumulation provisions for wastes that they do not generate at their site. [December 31, 1980; 45 FR 86969, RO 11163, 11358, 14466]

Transporters receive wastes from other parties but typically do not generate their own wastes. (Bulking like wastes together to facilitate shipment may change the properties of a waste, but this activity is not necessarily considered to be waste generation. [RO 13272]) Section 263.12 specifies that transporters may store wastes in containers at a transfer facility for up to 10 days. However, transporters who mix wastes of different DOT shipping descriptions must remanifest the waste to accurately reflect the composition of the new waste. This would occur, for example, when transporters combine two RCRA ignitable wastes—one a DOT combustible material and the other a DOT flammable waste. Such mixing requires transporters to comply with Part 262 generator standards [per §263.10(c)(2)]. In this situation:

“Although they may indicate on the manifest in Box [14] the name of the original generator(s) of the combined waste, they must represent themselves as the generator of the new waste. Although by creating or generating a new waste they have taken on some of the generator requirements, the transporter should continue to manifest the waste to the designated facility as indicated on the original manifest by the original generator.” [RO 11567]

Note that mixing different hazardous wastes at transfer facilities may require transporters to comply with some generator standards (as noted above). However, transporters cannot make use of the 90/180/270-day accumulation provisions but must comply with the 10-day clock of §263.12. [RO 13272]

Allowable units

Generators practicing 90/180/270-day accumulation are allowed to use only certain types of units (see Table 2). In most cases, the units of choice are tanks and containers. The peculiarities associated with each type of unit are discussed in this section.


When an LQG accumulates wastes in a tank, all of the Part 265, Subpart J tank standards apply, with the following exceptions [§262.17(a)(2)]:

  1. The generator does not need to prepare closure plans and contingent post-closure plans for the tanks that do not have secondary containment [see §265.197(c)]; and
  2. The generator does not need to conduct waste analyses and trial treatment tests per §265.200 when the waste properties change. [Note that if a waste is being treated in a 90-day tank for the purpose of meeting the land disposal treatment standards, a waste analysis plan is required per §268.7(a)(5).]

Probably the most important (and expensive) tank standards applicable to LQGs are the secondary containment and leak detection standards in §265.193. These standards make it clear that wastes can’t simply be stored for up to 90 days in just any old tank. If the tank doesn’t have impervious secondary containment, it can’t be used for hazardous waste accumulation.

The tank standards applicable to 180/270-day accumulation at SQG sites are greatly simplified. These units are subject only to the standards in §262.16(b)(3), which don’t require that tanks be equipped with secondary containment and leak detection. An SQG would comply with the reduced tank standards in §262.16(b)(3), even if it is treating hazardous waste onsite in a 180/270-day accumulation tank. [RO 14684]


Both large and small quantity generators may use containers for waste accumulation. These containers are subject to the standards in §262.17(a)(1) for LQGs and §262.16(b)(2) for SQGs. Note that SQG containers are not subject to the standards specifying that ignitable or reactive wastes be stored at least 50 feet from the property line. SQG containers are also not subject to the air emission standards of Part 265, Subparts AA, BB, or CC.

One important container standard is that containers must be closed except when adding or removing wastes. When EPA initially discussed the closed-container provision, their intent was that waste containers be vapor tight and spill proof. [45 FR 33199]

Drip pads

Although LQGs are allowed to accumulate wastes for up to 90 days on drip pads, this is only of practical significance to companies in the wood preserving business. These companies utilize pressurized systems to force wood preservatives into wood products. When the products are removed from the pressurized systems, some of the preservatives “kick back” or drip from the products onto collection areas known as drip pads. The standards applicable to drip pads used for 90-day accumulation are found in §262.17(a)(3) and Part 265, Subpart W.

SQGs may utilize drip pads if they comply with the requirements in §262.16(b)(4) for the management of wastes on drip pads, including a limit for onsite accumulation on the pad of 90 days. However, SQGs using drip pads may continue to accumulate hazardous waste removed from the pad in tanks and containers for up to 180 days.

Containment buildings

Containment buildings are engineered structures that EPA intended to be used for storing/treating bulky solids such as contaminated debris. The standards for these buildings are specified in Part 265, Subpart DD and §262.17(a)(4) for LQGs and §262.16(b)(5) for SQGs. LQGs may use containment buildings for 90-day accumulation. SQGs can also use a containment building for waste accumulation, but such units are limited to 90 days of onsite accumulation.

Some people mistakenly believe that “containment buildings” are container storage buildings that have secondary containment as specified in §264.175. Although such buildings might be able to meet the Subpart DD standards, this is typically not the case. For example, if a Subpart DD containment building is used to manage wastes containing free liquids, the building must have a primary barrier (e.g., a concrete floor), an underlying secondary barrier (e.g., an impermeable geomembrane), and a leak detection/collection system between the two barriers. [§265.1101(b)]

Allowable activities—accumulation and treatment

Although the 90/180/270-day accumulation provisions were originally developed to allow short-term accumulation of wastes, EPA has consistently maintained that wastes may also be treated without a permit in units that are in compliance with §§262.16–17. (Note, however, that thermal treatment is not allowed, as is discussed below.)

The preamble to the SQG rule originally spelled out the treatment-in-accumulation-units exemption. [March 24, 1986; 51 FR 10168] The rationale for this treatment exemption was that the RCRA standards for containers and tanks don’t distinguish between treatment and storage activities conducted in these units. Therefore, no justification existed for allowing storage, but not treatment, in accumulation units. Subsequent guidance extended the treatment exemption to LQGs and to activities in containment buildings. [RO 13553, 13782]

Treatment residues may get a new clock

Based on December 31, 1980 Federal Register preamble language [45 FR 86969], residues from treatment processes are new points of generation and are therefore eligible for a new 90-day clock. [RO 12865] For example, spent solvent stored in containers would be subject to the 90/180/270-day accumulation provisions. When the solvent is distilled onsite, the still bottoms are considered to be newly generated wastes, and are eligible for a new 90/180/270-day clock. [RO 11420, 12850, 12865, 13280] Note, however, that this guidance appears to be limited to residues from either interim status/permitted units or RCRA-exempt units (e.g., recycling units or wastewater treatment units).

Thermal treatment

Thermal treatment is regulated by: 1) thermal treatment unit standards (Part 265, Subpart P), 2) incinerator standards (Part 264/265, Subpart O), 3) boiler and industrial furnace standards (Part 266, Subpart H), or 4) miscellaneous unit standards (Part 264, Subpart X). Thus, if thermal treatment occurs in an accumulation unit, the permitting exemption of §§262.16–17 does not apply. [RO 13553, 14662] For example, open burning/open detonation is cited as a type of thermal treatment that is not eligible for the §262.16–17 exemption. [RO 11310]

The 90-day clock

Many issues arise with how the 90-day clock (180/270-day clock for SQGs) applies in different situations. The most common questions are answered below, and Case Study 1 illustrates numerous 90-day accumulation requirements under RCRA.

Case Study 1

Unknown wastes

How does the 90-day clock apply to an unknown waste placed in a drum that, after analysis, is found to be hazardous?

The 90-day clock starts when the waste is first generated and placed in the drum—not when the generator receives the waste analysis results. (EPA is concerned that if a waste isn’t hazardous until the results of an analysis are obtained, generators could put off getting analytical information.) According to EPA, “If the date on which accumulation began was not marked on the drum…or the drum was not marked ‘Hazardous Waste’ [and also marked with an indication of the hazards of the contents], then the generator has not met the pre-conditions for the exemption from the permitting requirements….” [RO 11424; see also 81 FR 85750–1, EPA/233/B-00/001]

In order to avoid confusion regarding the regulatory status of unknown wastes, a number of facilities use a label stating “Hazardous waste pending analysis.” This wording makes it clear to the generator’s personnel and to agency inspectors that the regulatory status of the waste is uncertain and may change. If analytical results indicate the waste isn’t hazardous, the label may be removed. If the waste does prove to be hazardous, the 90-day accumulation labeling requirement has been satisfied.

When does the clock start?

In general, the 90/180/270-day clock starts when the first drop of waste is placed into the accumulation unit. For wastes in satellite accumulation containers, the clock starts when 1) the containerized waste first enters the 90/180/270-day area, or 2) three days after the satellite unit is dated if it is not moved. [RO 13410, 14703]

Generators may transfer hazardous waste between containers in 90/180/270-day accumulation areas. However, the 90/180/270-day clock does not restart if the hazardous waste is transferred to another container. Additionally, the regulations do not prohibit the movement of hazardous waste from one 90/180/270-day area to another, as long as the waste remains onsite. However, the 90/180/270-day clock does not restart if the hazardous waste is moved to another 90/180/270-day area. [RO 14703]

For VSQGs, a 90-day clock starts when onsite accumulation exceeds 1 kg of acute hazardous waste or exceeds 100 kg of acute spill cleanup residue. [§262.14(a)(3)] Also, a 180/270-day clock starts when onsite accumulation equals or exceeds 1,000 kg of nonacute hazardous waste. [§262.14(a)(4)]

When does the clock stop?

The action that stops the 90/180/270-day clock depends on the type of accumulation unit being used, as discussed in the following subsections.


For containers, the clock stops when:

  • The container is moved from the 90/180/270-day accumulation area to an onsite interim status or permitted storage area [November 19, 1980; 45 FR 76625];
  • The waste is transferred from a 90/180/270-day container to an interim status or permitted treatment or disposal unit [November 19, 1980; 45 FR 76625];
  • The container is shipped offsite;
  • The waste is transferred to a unit that is exempt from RCRA (e.g., a recycling unit, a wastewater treatment unit, or an elementary neutralization unit); or
  • The waste is rendered nonhazardous via treatment in the container.

As noted earlier, transferring wastes from a 90/180/270-day container to another container (assuming the second container is not in an interim status or permitted storage area) does not stop the clock. The clock continues to run on the second container until one of the five events cited above occurs.


For tanks, the clock stops when the tank is “empty.” According to EPA, “A tank will be considered ‘empty’ when its contents have been drained to the fullest extent possible. Since many tank designs do not allow for complete drainage due to flanges, screens, or syphons, it is not expected that 100% of the wastes will always be removed. As general guidance, a tank should be considered empty when the generator has left the tank’s drainage system open until a steady, continuous flow has ceased.” [January 11, 1982; 47 FR 1250]

Note that more recent EPA guidance allows flow-through tanks to be used for accumulation purposes by using a “turnover” or “mass balance” approach to determine whether a tank is emptied within 90 days:

“EPA is interpreting [§262.17(a)(2)] to allow for the turnover approach…. In the case of hazardous wastes flowing through tanks continuously, there is a means of demonstrating when a tank is ‘emptied’ within 90 days under [§262.17(a)(2)] that would not require completely emptying the tank, and that may be more suitable for tanks with continuous flow. More specifically, a mass balance approach (i.e., the ‘turnover’ approach, as you referred to it, in your letter) can be used for continuous flow tanks rather than the approach described above for batch process tanks. The key parameters in this mass balance approach are the volume of the tank (e.g., 6,000 gallons), the daily throughput of hazardous waste (e.g., 300 gallons per day) and the time period the hazardous waste ‘resides’ in the tank. In this example, the hazardous waste entering the tank would have a residence time of 20 days ((6,000 gallons/300 gallons per day) = 20 days) and meet the requirements of [§262.17(a)(2)] since the hazardous waste has been in the tank for less than 90 days.” [RO 14763]

The guidance also discusses the kinds of records that a generator should maintain to demonstrate compliance with the 90-day time limit:

“Large quantity generators accumulating hazardous wastes through a continuous flow process must also demonstrate that the hazardous waste has not been stored for more than 90 days. This may be achieved by the use of inventory, or some form of accounting or monitoring data. For example, a generator could confirm that the volume of a tank has been emptied every 90 days by recording the results of monitoring equipment both entering and leaving a tank. This recordkeeping, in conjunction with the tank volume, would enable inspectors, as well as facility personnel to demonstrate compliance with [§262.17(a)(2)]. Likewise, in marking the tank, a generator could mark both the tank volume and estimated daily throughput to allow inspectors to determine the number of days that hazardous waste resides in a tank to determine compliance with [§262.17(a)(2)].”

The 90/180/270-day clock would also stop in tanks if the waste is rendered nonhazardous.

Drip pads

Both large and small quantity generators are required to remove all wastes from the drip pad at least once every 90 days. [§262.17(a)(3)(ii) or 262.16(b)(4)(ii), respectively] Owners/operators must maintain records describing the procedures that are used to ensure that all wastes are removed at least once every 90 days. The quantity, date, and time of each removal must also be documented. Hazardous wastes that are removed from the drip pad may then be managed in either satellite accumulation containers or 90- or 180/270-day accumulation units (for LQGs or SQGs, respectively).

Containment buildings

For containment buildings, the clock stops when each volume of waste is removed from the building. This requirement can be met by documenting that: 1) the containment building is emptied at least once every 90 days, or 2) procedures are in place to ensure that wastes are segregated by age and that no portion of the accumulated wastes remains in the containment building for more than 90 days. [§262.17(a)(4)(ii) or 262.16(b)(5)(ii), August 18, 1992; 57 FR 37212]

Accumulation time extensions

Both large and small quantity generators can apply for a 30-day extension to the accumulation period where unforeseen, temporary, and uncontrollable circumstances prevent them from complying with the 90/180/270-day time limits. [§§262.17(b) and 262.16(d)] Examples of such circumstances include refusals of waste shipments, transporter delays, and labor strikes [January 11, 1982; 47 FR 1249], as well as transporters and/or receiving facilities going out of business or otherwise closing. [RO 13013] Extensions are granted on a case-by-case basis by the authorized agency (EPA regional office or state RCRA agency).

After the 30-day extension expires, the facility must comply with interim status requirements or have a permit for continued storage.

If the generator is not granted an extension, he/she is the operator of a storage facility on the 91st or 181st day of storage, and the facility is subject to requirements in Parts 264, 265, and 270.

Generators get a new 90/180/270-day clock for returned shipments

To allow generators to receive shipments of non-RCRA-empty containers or rejected hazardous waste, EPA has amended the definition of “designated facility” in §260.10 to include generators receiving returned waste shipments. Generators receiving returned shipments have either 90 or 180/270 days (for large or small quantity generators, respectively) to send returned waste to an alternate facility. [§262.17(g) or 262.16(e)] This accumulation time limit is based on the generator’s status when the rejected waste is received by the generator (not when the waste originally left the generator’s site). If a generator was classified as an SQG when the waste was initially shipped offsite but is an LQG when the rejected waste is returned, the generator could accumulate the waste for no more than 90 days without a permit.


Topic: Burning Used Oil

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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.