Ask the Expert, Special Topics in Environmental Management, Transportation

SPCC Plans and Secondary Containment Options for Mobile Tanks

Q. If we have an independent contractor come to our facility for 60 days each year with a 4000-gallon diesel tank, will we need to add their tank to our plan or have them develop a plan? What options do we have for secondary containment for mobile tanks?

A. The 4000-gallon diesel tank must be included in an SPCC plan for your facility, and it is preferable that it be an addition to your plan. If the tank is a mobile refueler, general secondary containment requirements apply. If it is a mobile bulk storage container, specific secondary containment requirements apply too.

General secondary containment. The general secondary containment provision requires that these areas be designed with appropriate containment and/or diversionary structures to prevent a discharge the most likely quantity of oil that would be discharged from the primary containment system such that the discharge will not escape secondary containment before cleanup occurs. In determining the most likely quantity, you should consider factors such as the typical failure mode (e.g., overfill, fracture in container wall, etc.), resulting oil flow rate, facility personnel response time, and the duration of the discharge.

The general secondary containment provisions require that the entire containment system, including walls and floor, must be capable of containing oil and must be constructed so that any discharge from a primary containment system, such as a tank or pipe, will not escape the containment system before cleanup occurs (so not dirt floor allowed). In determining the method, design, and capacity for secondary containment, you need only to address the typical failure mode, and the most likely quantity of oil that would be discharged. Secondary containment may be either active or passive in design. In the regulations, the EPA recommends one of the following, although other containment methods may be used as long as they consistent with good engineering practice:

  • Dikes, berms, or retaining walls sufficiently impervious to contain oil;
  • Curbing or drip pans;
  • Sumps and collection systems;
  • Culverting, gutters, or other drainage systems;
  • Weirs, booms, or other barriers;
  • Spill diversion ponds;
  • Retention ponds; or
  • Sorbent materials.

Specific secondary containment. While all parts of a regulated facility with potential for a discharge are, at a minimum, subject to the general secondary containment requirements of 112.7(c) where certain types of containers, activities, or equipment are located may be subject to additional, more stringent containment requirements, including specifications for minimum capacity. Such containers, such as mobile bulk storage, must comply with the secondary containment requirements of §112.8(c)(11).

These specific secondary containment provisions require that mobile or portable oil storage containers be located to prevent a worst case discharge. Except for mobile refuelers and other non-transportation-related tank trucks, you must furnish a secondary means of containment, such as a dike or catchment basin, sufficient to contain the capacity of the largest single compartment or container with sufficient freeboard to contain precipitation.

Because this aboveground storage is temporary, you do not need to amend your entire SPCC Plan to discuss the temporary aboveground storage. However, you should place an addendum in your SPCC Plan that describes the storage, spill scenarios, and administrative and engineering controls employed at the facility for the temporary storage, including a description of secondary containment, loading/unloading containment, emergency procedures, inspection procedures, and security.

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