Compliance Corner.

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.

Unknown wastes

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.

Containers

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 [45 FR 76625];
• The waste is transferred from a 90/180/270-day container to an interim status or permitted treatment or disposal unit [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, 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.

Tanks

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.” [47 FR 1250]

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 LQGs and SQGs are required to remove all wastes from the drip pad at least once every 90 days. [§262.17(a)(3)(ii) and 262.16(b)(4)(ii), respectively] Owners/operators must maintain records describing the procedures used to ensure all wastes are removed at least once every 90 days. The quantity, date, and time of each removal must also be documented. Hazardous wastes 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), 57 FR 37212]

Accumulation time extensions

Both LQGs and SQGs 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 [47 FR 1249], as well as transporters and 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).

An extension, if granted, may also necessitate changes to waste management practices to ensure the protection of human health and the environment. These may include increased inspections, temporary secondary containment, and informing local emergency response committees. In some cases, consecutive extensions may be granted. While federal regulations do not limit the number of extensions, each request must meet the criteria in the regulations. [RO 14939]

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, it 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.

Accumulation time extensions are not available for hazardous waste pharmaceuticals managed under Part 266, Subpart P. [RO 14959]

Answers to frequently asked questions on accumulation time extensions, in particular within the context of the incinerator backlog of the early 2020s, are available at https://www.epa.gov/hw/backlog-containerized-hazardous-waste-needing-incineration.

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 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 LQGs or SQGs, 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.