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A Primer on Secondary Containment

Secondary Containment
If you’re in the tank storage industry, using secondary containment just makes logical sense. It provides padded insurance by containing and preventing hazardous releases into the environment in case the tank was improperly installed or maintained. Below is a rundown on secondary containments
The conception
In the United States, secondary containment made its first appearance in the early 1980s when investigations started to pop up concerning serious tank leakage. The solution was to build a secondary containment to guard and store hazardous liquids. And California was one of the first states to implement secondary containment for tanks.
How much should a secondary containment hold?
Some professionals believe that the secondary containment must hold from the largest/primary tank. But initially, the design of the secondary containment was to hold 110 percent or the primary tank’s capacity or 10 percent of the total volume stored, whichever is greatest. But cost can add up, so some industry professionals felt that 100 percent containment was sufficient.
The rules
In July of 1986, the Environmental Protection Agency (EPA) required that double wall tanks:

  • be designed as an integral structure so that any release from the inner tank be contained by the outer shell,
  • protect the primary tank from corrosion,
  • and provide a built-in continuous leak detection system capable of detecting a release within 24 hours.

Most operations that store or process hazardous liquids must have a written Spill Prevention Control and Countermeasure (SPCC) plan in place that addresses how the facility will prevent leaks from the environment. The SPCC also requires facilities to be prepared for and have the ability to respond to oil discharges if the processes and/or devices put into place fail.
Types of secondary containment
According to the EPA, a secondary containment is either active or passive in design.

  • Proactively placing storm drain covers over drains prior to oil transfers
  • Reactively placing storm drain covers over drains before a spill reaches them
  • Using a spill kit in the event of an oil discharge
  • Using a spill response team (spill response capability) in the event of an oil discharge
  • Closing a gate valve prior to a discharge

Under passive containment measures, a person is not required to contain a spill. Examples include:

  • Containment pallets
  • Berms
  • Retaining walls
  • Drip pans
  • Spill diversion and retention ponds

Soil foundation
A tank is heavy. A tank with a concrete secondary containment is heavier, which means the foundation the tank is placed on must be stable and solid to ensure proper long-term strength of its structure and equipment.
Prior to construction of a new tank, all soil must be compacted and tested to guarantee proper specifications are met.
Inspection of secondary containment
If you use a concrete secondary containment, they typically have three levels of inspection. They are:

  1. Routine inspections (i.e., daily or weekly) are needed to ensure proper storm water management for outdoor facilities and check that new cracks, gaps, or other imperfections (e.g., damaged coating in sumps, or exposed aggregate or rebar) have not developed.
  2. Periodic (e.g., semiannual) detailed inspections by trained facility personnel are warranted to ensure that adequate conditions are maintained over the longer term
  3. Independent Professional Engineers are used if there are questions or concerns about the integrity of the secondary containment systems.

Inspection is an important precautionary step for secondary containment. It requires constant maintenance to ensure it remains impervious to leaks and spills.

Carol Carol Liu
Carol Liu is a Marketing Manager of Castagra Products, a storage tank and wastewater coatings manufacturing company that is highly acclaimed for its sustainable coatings, cold weather tank and secondary containment coating applications, and its durable frac tank coatings. Castagra is used by the world’s top oil and gas field services companies.