Storing hazardous waste in tanks

• Tanks are often the first choice for the storage and accumulation of hazardous waste because they hold large volumes and can be used for the treatment of hazardous waste.
• Where hazardous waste is continuously fed into a tank, the tank must be equipped with a means to stop this inflow.

For storage of hazardous waste in tanks, a facility must follow some common-sense rules:

• Do not store hazardous waste in a tank if it may cause rupture, leaks, corrosion, or otherwise cause the tank to fail.
• Keep a tank covered or provide at least two feet of freeboard (space at the top of the tank) in uncovered tanks.
• If tanks have equipment that allow the waste to flow into them continuously, provide waste feed cutoff or bypass systems to stop the flow in case of problems.
• Inspect any monitoring or gauging systems on each operating day and inspect the tanks themselves for leaks or corrosion every week.
• Ignitable or reactive wastes must not be placed in a tank unless the waste is stored or treated in such a way that it is protected from any materials or conditions that would cause it to ignite or react.
• Use the National Fire Protection Association’s (NFPA) buffer zone requirements for tanks containing ignitable or reactive wastes. These requirements specify distances considered as safe buffer zones for various liquids based on the characteristics of all combustible and flammable liquids. Call the local fire department or Environmental Protection Agency (EPA) regional office if help is needed.
• Hazardous waste must not be placed in an unwashed tank which previously held an incompatible waste or material unless the facility is sure that the storage will not result in the creation of extreme heat, toxic gases, flammable fumes, or any threat to human health or the environment.
• Conduct weekly inspections of the tanks and surrounding area.
• Conduct daily inspections of overflow control, monitoring equipment data, level of waste in the tank.
• Again, make sure that the stored waste is taken offsite or treated within 180 (or 270) days.

Note that for labeling tanks, EPA allows a company to use an inventory form or other method of determining that the company is meeting the 180- or 90-day accumulation time limit.

Secondary containment for hazardous waste tank systems

Tanks are often the first choice for the storage and accumulation of hazardous waste because they hold large volumes and can be used for the treatment of hazardous waste. If a facility generates or manages hazardous waste in tanks the facility will be required to provide secondary containment.

Secondary containment is required for the following:

• Hazardous waste treatment, storage, and disposal facilities (TSDFs) (40 CFR 264 and 265 Subpart J);
• Hazardous waste generators that use tanks as primary management units for accumulating hazardous wastes. This includes large quantity generators (262.17 and 265.17) and small quantity generators (262.16 and 265.17); and
• Facility owners or operators who store or treat hazardous waste in containment buildings.

Note: If a tank system does not have secondary containment and has not been granted a variance, it is considered to be less protective against a release to the environment. Therefore, EPA requires the facility to develop plans for closing the tank system and closing the unit as if it were a landfill. The facility must also show that it has sufficient funds to close the tank in either instance.

The regulations for small and large quantity generators call for uncovered tanks to be operated to ensure at least 60 centimeters (two feet) of freeboard, unless the tank is equipped with a containment structure (e.g., dike or trench), a drainage control system, or a diversion structure (e.g., standby tank) with a capacity that equals or exceeds the volume of the top 60 centimeters (two feet) of the tank.

Where hazardous waste is continuously fed into a tank, the tank must be equipped with a means to stop this inflow (e.g., waste feed cutoff system or by-pass system to a stand-by tank).

Underground storage

Note that when hazardous wastes are stored in underground storage tanks, the tanks are subject to 40 CFR Parts 264 and 265 (Resource Conservation and Recovery Act (RCRA) Subtitle C) rather than the regulations for underground storage tanks storing petroleum products at 40 CFR 280-281 (Subtitle I).