Nine Tips for Storing Chemicals Outside

The recent hurricanes that devastated Texas and Florida and destroyed Puerto Rico give pause to environment, health, and safety (EHS) managers who sometimes need to store chemicals in outdoor areas. What can you do to mitigate potential releases when storing chemicals outside?

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When Is It a Good Idea to Store Chemicals Outside?

Well, actually never. According to the U.S. Environmental Protection Agency (EPA) you should reduce or eliminate outdoor storage of toxic materials to prevent loss and possible releases during a major storm event. In general, temporary outdoor sheltering of industrial materials should only occur during facility renovation or construction.

Nine Tips for Storing Chemicals Outside

If you have to store chemicals outside, there are some best management practices you can put in place to mitigate the potential for a spill or release.

Tip 1: Make sure you know the base flood elevation in your area. Identify which floodplains your facility is in. In areas of flood risk, store chemicals on higher ground above the high flood mark.

Tip 2: Review how past extreme weather events have threatened your facility. Use various sources, including facility records, newspapers, websites, and hazard mitigation experts, to collect previous extreme weather data.

Tip 3: Determine consequences based on replacement costs and impacts to facility operations from extreme weather events.

Tip 4: Prioritize the need for mitigation to improve resilience to extreme weather events. Evaluate which mitigation measures make sense to pursue. Mitigation measure to protect chemicals stored outside could include bolting down chemical tanks.

Tip 5: Designate an individual who will regularly conduct inspections of containers stored outside.

Tip 6: Ensure that you are using the proper container type (one that does not react with the toxic material).

Tip 7: Immediately close, replace, or shelter any external container that is open, deteriorating, or leaking.

Tip 8: Ensure that containers, racks, and other transport platforms (e.g., wooden pallets) used with the drums, barrels, etc., are contaminant-free.

Tip 9: When storing chemicals outside in aboveground storage tanks (ASTs), ensure that:

  • The ASTs are physically separated from and not associated with vehicle maintenance operations.
  • There are no piping, pumps, or other equipment leaking contaminants that could contact stormwater.
  • Surround the AST with some type of physical containment (e.g., an impervious dike, berm, or concrete retaining structure) to prevent runoff in the event of a structural failure or leaking transfer valve.

Note on ASTs: ASTs are primarily regulated by the states, which may have stricter regulations that require tank registration, installation permits, and fees. In addition, states may have stricter AST requirements for spill prevention planning, spill response, tank inspection, and notification requirements, as well as secondary containment standards.

Most ASTs need to meet state and local fire codes, which usually have some mix of construction, installation, and operation and maintenance requirements that are intended to prevent fires and other hazards that can come from mismanaged or substandard ASTs.

OSHA Requirements for Outside ASTs

The Occupational Safety and Health Administration (OSHA) has requirements for storing flammable liquids in outside ASTs. Make sure that ASTs storing flammable liquids:

  • Are spaced by at least 3 feet. The distance between adjacent tanks must be based on the tank diameter, the type of liquid, tank capacity, and/or tank operating pressure (and emergency venting capabilities).
  • Are adequately vented to prevent vacuum or pressure buildup. Vent size and whether the vent must be closed will be determined by a combination of factors, including tank capacity, category of liquid being stored, and the designed operating pressure of the tank.
  • Are provided with emergency relief venting capable of relieving excessive internal pressure caused by exposure to fires.
  • Have dikes or drainage designed to protect adjoining property or waterways. Dikes must be constructed to be liquid-tight and to withstand full hydrostatic head.

Check State and Local Requirements

Make sure to check your state and local requirements for storing chemicals in outdoor areas. For example, Louisiana has a requirement that applies, in part, to hazardous materials temporarily stored in portable containers during Category 3 or higher hurricanes. A report must be sent to the Louisiana Department of Public Safety within 12 hours of a mandatory evacuation order. Only hazardous materials that were not reported in the annual inventory report and those that are in excess of what is typically stored at the facility must be reported. The report must include:

  • The nature, type, location, and relative fullness of the containers;
  • Contact information for the primary and secondary responsible people; and
  • Whether the facility will be sufficiently staffed to perform postevent assessments.


You may not be able to avoid storing hazardous chemicals outside, but there are steps you can take to mitigate spills and releases during both normal times and extreme weather events.