How to Calculate Secondary Oil Containment Capacity

If your facility stores a lot of oil, you likely must meet the demands of the Spill Prevention, Control and Countermeasure (SPCC) Rule. Calculating secondary containment is essential to staying compliant and mitigating environmental harm, but oil berm capacity depends on many factors. Thankfully, with the right information, you can determine how much secondary containment you need to comply and prevent a negative impact on the environment.

What’s Included in the Secondary Containment Oil Capacity Requirements?

Before calculating secondary containment needs, confirm your requirements under SPCC. While oil containment is always a good idea, government regulations require special attention to detail and understanding your oil storage capacity. Facilities are subject to the SPCC rule if they have aboveground oil storage capacity of over 1,320 US gallons or buried storage capacity of over 42,000 US gallons. Only consider containers with capacities of 55 gallons or more.

Some facilities that commonly fall under SPCC requirements include oil well drilling facilities, oil refineries, oil production facilities and industrial, commercial, agricultural or public facilities that store or use oil. Transportation-related activities and equipment, such as oil pipeline systems or oil transported in vessels, do not need to meet SPCC requirements.

Types of Oil

These amounts cover any type of oil, including:

  • Petroleum and fuel oil
  • Sludge
  • Synthetic and mineral oils
  • Fats, oils or greases from animals, fish or marine mammals
  • Oil refuse
  • Vegetable oils, including oil from seeds, fruits, nuts or kernels
  • Oil mixed with wastes other than dredged spoil

Oil Containers

Most oil containers will contribute to the total storage capacity, including bulk storage containers and oil-filled equipment. Here are some examples:

  • Aboveground, partially buried and some completely buried tanks
  • Tanks in vaults or bunkered tanks
  • Mobile or portable containers, such as totes, mobile refuelers and tank trunks unrelated to transportation activities
  • Electrical or operating equipment, like hydraulic pumps, lubricating systems, coolant systems and transformers
  • Manufacturing equipment, such as process vessels
  • Other equipment used in altering, processing or refining crude and other non-petroleum oils

You can use several types of secondary containment solutions for these varying applications. For instance, you might use an SPI Oil Containment Shield™ for a small transformer.

A larger area would require a solution like Petro-Barriers™ to accommodate significant volumes of water drainage. Petro-Barriers™ have a passive, gravity-fed system for filtering and discharging rainwater. Once the oil is released, the entire system seals so the oil cannot escape.

Risk of Oil Discharge

SPCC only applies to facilities with a risk of discharging oil into navigable waters or adjoining shorelines. If your facility sits near a coast or shoreline, you likely need to meet SPCC, but many other waterways also qualify. The Environmental Protection Agency (EPA) offers guidance on making this determination that you can access online.

Need for SPCC

What Affects Oil Berm Capacity?

Of course, the size of an oil storage tank will be the key factor in calculating an oil berm’s capacity, as it must accommodate that amount. You’ll base your calculation on the largest tank in the containment area. Other important components of secondary containment capacity include:

  • Precipitation displacement: If your dike or berm will collect rainfall, the SPCC rule requires extra capacity. While many engineers add an extra 10% to the tank’s capacity to account for rain and prevent spills, some states or jurisdictions ask for more specificity. In these cases, you may need to find the volume of precipitation produced during a 24-hour, 25-year storm event from sources like the National Oceanic and Atmospheric Administration (NOAA) and local water authorities.
  • Tank and structure displacement: While your calculations will start with the largest tank, you’ll also need to consider any smaller tanks or structures in the containment area, as they will displace fluids and reduce the available space. The sizes of these items will increase the space required for secondary containment.
  • Additional restrictions: Some facilities will have additional restrictions, such as local building codes or safety requirements from the Occupational Safety and Health Administration (OSHA). For example, you may need to keep your structure below a specific height or leave room around the perimeter.

How Much Secondary Containment Do I Need?

Calculating what size oil berm you require involves finding the maximum number of gallons you would need to contain in the event of oil discharge. Consider reviewing the EPA’s sample calculations and follow these steps:

1. Find the Largest Vessel and Freeboard

Start your secondary containment calculations by listing all the area’s containers and identifying the largest vessel. Take its capacity in gallons and add about 10% to the value for freeboard volume. If you will use storm data, skip adding 10% and move forward with your vessel capacity.

2. Find the Area of the Containment Space

Divide the gallons from Step 1 by 7.48. This step identifies how many cubic feet of secondary containment space you’ll need to accommodate the volume of the vessel and freeboard.

3. Find the Dimensions of the Containment Space

Divide the volume in cubic feet from the previous step by the height and width of a potential berm or containment wall. Try different lengths and widths to find a solution that fits your space. Use your width and length to find the surface area of the secondary containment in square feet. Naturally, you will require an area and volume that accommodates the capacity of your storage tank.

4. Account for Displacements

The last step is to account for rainfall and the size of other tanks within the dike or berm. Ideally, your tank manufacturer will provide a liquid height-to-gallons conversion chart, which you can use to find the displacement volume of the second tank in cubic feet. Divide this number by the surface area of the containment space to find the required wall height to contain the tank’s volume.

If you need to use actual precipitation values for rainfall, find the amount of rain expected in 24 hours during a 25-year storm event for your location. Then, follow these steps:

  1. Convert the amount to feet.
  2. Multiply this value by the area of the secondary containment space from Step 3. This calculation results in the volume of rain to be contained in cubic feet.
  3. Add this amount to the tank volume in cubic feet from Step 2.

Make sure the size of your containment area is larger than the value calculated, or size up.

Need Help Calculating Secondary Containment Needs? Contact the Experts

Contact Us

Secondary containment calculations can vary depending on factors like your needs and jurisdiction. If you’re unsure about your secondary containment requirements, reach out to an expert at Solidification Products International Inc. (SPI). Our knowledgeable team can help you find the right size and type of containment solution from our diverse catalog of products.

We’re well-versed in SPCC regulations and have been supporting clients for over 30 years. Contact us today to discuss your secondary containment oil capacity needs.

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