Storage Criteria for Polluting Materials

These storage criteria were established 2-19-1998 in accordance with Section 5.4 of the Washtenaw County Pollution Prevention Regulation, which provides that, "all parties who store toxic, hazardous, or polluting materials shall do so in a manner that will assuredly prevent contamination of the environment."

Due to the diversity of materials and packaging volumes covered by the Regulation, this document presents above ground storage requirements in terms of general standards.

Underground storage is governed by the Michigan Department of Environmental Quality. Storage of specific materials or container types may also be controlled by other state federal or local agencies.


  • Combustible Liquid - A liquid material with a flash point at or above 100 degrees Fahrenheit.
  • Compatible - Materials that will not react violently or produce dangerous gases or vapors when mixed.
  • Contamination - The presence or introduction of a substance into the environment above naturally occurring concentrations.
  • Environment - The air, water and land outside a workplace.
  • Flammable Liquid - A liquid material with a flash point below 100 degrees Fahrenheit.
  • Primary container - The container that is in immediate contact with a substance.
  • Secondary Containment - Spill control devices that are external to the primary container of a substance. The concept of secondary containment is to prevent environmental contamination or human exposure to chemicals when a primary container is damaged or spilled.
  • THP - Toxic, Hazardous, or Polluting acronym.

Design Considerations

The specific design of secondary containment systems involves a number of considerations, including function and practicality. Many prefabricated secondary containment units are available, however they are not universally suited. In some situations, the floor of a building will provide adequate secondary containment. The following issues should always be considered when designing or selecting a system:

  1. What are the types of materials to be stored? This will dictate limitations on construction material and may impact required capacity.
  2. How much will be stored, and what is the largest container? This will determine the storage capacity of secondary containment.
  3. What are the logistics involved?
    • Proximity to work areas.
    • Methods of transferring the substance.
    • Indoor verses outdoor storage. Precipitation must be controlled for outdoor storage. It may be necessary to dispose of accumulated water as hazardous or liquid industrial waste.
    • Above ground vs. underground storage.