• In some cases, passive secondary containment may not be feasible; in those cases, active containment measures may be used.
• The efficacy of active containment measures to prevent a discharge depends on their technical effectiveness, placement and quantity, and how quickly they can be deployed to immediately contain a discharge.

In some situations, dikes and other permanent containment structures known as passive secondary containment may not be feasible. For example, they may cause pooling of liquids around electrical equipment which may present a hazard. Part 112.7(c) specifically allows for the use of active containment measures (countermeasures or spill response capability that require deployment or action) to prevent a discharge to navigable waters or adjoining shorelines.

The use of active containment as a strategy to address discharges should be carefully evaluated. The efficacy of active containment measures to prevent a discharge depends on their technical effectiveness (e.g., mode of operation, absorption rate), placement and quantity, and timely deployment prior to or following a discharge. For discharges that occur only during attended or observed activities, such as those occurring during transfers, an active measure (e.g., sock, mat, other portable barrier, or land-based response capability) may be appropriate, provided that the measure is capable of containing the most likely volume of an oil discharge from a typical failure mode and is timely and properly constructed and deployed. Ideally, in order to further reduce the potential for an oil discharge to reach navigable waters or adjoining shorelines, the active measure should be deployed prior to initiating the activity with potential for a discharge.

For certain active measures, however, such as the use of “kitty litter” or other sorbent material, it may be impractical to pre-deploy the measure. In such cases, the sorbent material should be readily available so that it can be used immediately after a spill occurs but before it can spread. Portable tanks can be equipped with a spill kit to be used in the event of a discharge during transfers. The spill kit should be sized to effectively contain the volume of oil that could be discharged. Most commercially available spill kits are intended for relatively small volumes (up to approximately 150 gallons of oil).

Active containment measures can be used to satisfy the general secondary containment requirement when they are capable of containing the most likely discharge volume identified in the Spill Prevention, Control, and Countermeasure (SPCC) Plan. Elements to consider may include the capacity of the containment measure, effectiveness, timely implementation, and the availability of facility personnel and equipment to implement the active measure effectively. For example, a discharge of 600 gallons would require deploying more than 900 “high-capacity” sorbent pads (20 inches by 20 inches) since each pad absorbs less than 0.7 gallons of oil. The same spill volume would require nine sorbent blankets, each measuring 38 inches by 144 feet and weighing approximately 40 pounds. The rapid deployment of such response equipment and material would be difficult to achieve under most circumstances, particularly if only a few individuals are present when the discharge occurs, or during adverse conditions (e.g., rainfall, fire).

Using an active measure to meet the specific secondary containment requirement for a bulk storage container may be difficult because the containment system must be sized for the entire capacity of the bulk oil storage container. Therefore, the use of active measures for larger oil containers may not be appropriate or in accordance with good engineering practice or sound industry standards.

In certain circumstances, sorbents, such as socks, booms, pads, or loose materials may be used to complement passive measures. For example, where berms around transfer areas are open on one side for access, and where the ground surface slopes away from the opening with no nearby drains, sorbent material may be effective in preventing small quantities of oil from escaping the bermed area in the event of a discharge.

The secondary containment approach implemented at a facility need not be one size fits all. Different approaches may be taken for the same activity at a given facility, depending on the material and location. For example, the SPCC Plan may specify that drain covers and sorbent material be pre-deployed prior to transfers of low viscosity oils in certain areas of a facility located in close proximity to drainage structures or navigable waters. For other areas and/or other products (e.g., highly viscous oils), the plan may specify that sufficient spill response capability (spill response teams) are available for use in the event of a discharge, so long as personnel and equipment are available at the facility and these measures can be effectively implemented in a timely manner to prevent oil from reaching navigable waters or adjoining shorelines.

Evaluating the ability of active secondary containment measures deployed after a discharge to prevent oil from reaching navigable waters or adjoining shorelines involves considering the time it would take to discover the discharge, the time for the discharge to reach navigable waters or adjoining shorelines, and the time necessary to deploy the active secondary containment measure. For some active containment measures such as the use of sorbent materials, the amount of oil the secondary containment measure can effectively contain, including the potential impact of precipitation on sorption capacity, is also a critical factor. Good engineering practice would indicate that active secondary containment measures may be used to satisfy the general secondary containment requirements of 112.7(c) only in certain circumstances.

The use of an active measure containment strategy can be risky if not properly designed, evaluated, and implemented. If an active measure fails to prevent an oil discharge from reaching navigable waters or adjoining shorelines, the owner or operator is liable for the discharge and cleanup and is responsible for properly reporting it to the National Response Center. Furthermore, even when used to comply with 112.7(c), active measures should be limited to those situations where a professional engineer (PE) has determined that the typical failure mode involves a small volume of oil. Generally, active containment measures are not appropriate for satisfying the specific containment requirements for a major container failure. Environmental Protection Agency (EPA) inspectors may closely review the SPCC Plan and evaluate the rationale, equipment, and implementation of such a strategy, as in most cases, this would not be considered good engineering practice.

The SPCC Plan must describe the procedures used to deploy the active measures, explain how the use of active measures is appropriate to the situation, and explain the methods for discharge discovery that will be used to determine when deployment of the active measures is appropriate (112.7(a)(3)(iii) and (iv)).