Any SPCC-regulated site or facility is obligated by EPA regulation to have robust enough secondary containment that any oil spilled from primary containment will not be able to reach navigable water.
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If you are planning a site or facilities secondary containment, you may have already run calculations and have plans for the amount secondary containment you will need, as well as the rough shape and dimensions of your secondary containment units. What you may still be uncertain about is the material your secondary containment should be constructed out of.
The materials you have access to — as well as what will work best — will depend on your facilities containment needs. Below, we will cover what materials are typically available for secondary containment units and when these materials will work best.
When Is Secondary Containment Necessary?
One of the most significant EPA rules is the SPCC rule, which defines most of the cases in which secondary containment will be necessary, as well as how much containment a given site will need. Sites that can store more than 1,320 gallons of above-ground oil, or more than 42,000 of completely submerged oil, are regulated by the SPCC.
Sufficient containment will vary from site to site. As a rule of thumb, a site should have a unit large enough to contain all the oil within the largest single container, plus rainwater from a 25-year, 24-hour storm. You may also be able to use one of the EPA's secondary containment calculators to determine how much containment your site will need.
The EPA does not define what secondary container units should be constructed out of, or what these units should look like. This lack of regulation can be both good and bad news for SPCC-regulated site operators, or for companies who plan on constructing secondary containment.
These organizations or individuals will have freedom in the materials and construction style of their secondary containment units, but also no significant guidance from the EPA rules.
What Materials Are Best for Secondary Containment?
The best material for a secondary container unit will depend on where and how your primary containers are stored, as well as the traffic surrounding these containers.
There is a decent market for ready-made secondary containment units. Most of these units are manufactured from a plastic-like polyethylene, as these plastics do not rust, are impervious to UV rays and resist corrosion, unlike metal.
Spill containment pallets and trays are two kinds of secondary containment units popular in situations where there are just a handful of relatively small primary containers, like oil drums, that need secondary containment. These units are almost always suitable for areas with even heavy foot traffic.
Also popular are collapsible or ready-made berms and barriers. These are typically made of similar plastic materials and are reinforced with lightweight metal or plastic beams or supports that give the berm structure.
Other secondary containment methods include oil-absorbent pads and mats, which are usually made of a synthetic material like polypropylene that absorbs oil but not water. These pads will not be effective in areas with high levels of foot or machinery traffic, as they are liable to tear or otherwise become damaged.
Larger primary containers — especially when grouped or spread out over a wide area, like in the case of tanker farms — present different challenges that cannot be solved with ready-made secondary containment units.
Depending on the area your primary containers are in, you may be able to create sufficient secondary containment with unlined barriers. The EPA, in table 4-2 of their guide to the SPCC rule, list earth embankments and concrete containment walls as two possible examples of suitable secondary containment.
However, if there is a chance that a spill may seep through one of these barriers into the environment — or if it becomes cracked or damaged — it may need to be lined with protective material. A polyethylene or spray-in liner can be effective in situations like these.
Unlined berms will also likely need to be rehabilitated and treated following a spill.
What Machinery Should Be Used to Construct Secondary Containment?
Ready-made secondary containment units typically will not need machinery to be constructed or set up but may need to be transported by forklift depending on their weight and construction.
Heavy machinery, primarily earthmovers, will be required for the construction of earthen berms. The exact machinery needed will vary from site to site — in general, however, you should be prepared to move, pack and excavate earth as necessary.
Once the construction of the earthen berms is complete, the installation of protective covers will require manual labor.
Depending on the size and shape of the berm demanded by the amount of oil in your primary containers, you may need additional equipment to construct structurally-sound berms.
Establishing Effective Secondary Containment
SPCC-regulated facilities need to have enough secondary containment to contain any possible spills from primary containment to prevent that oil from making its way into navigable waters. These facilities have a few different options when it comes to establishing effective secondary containment.
Ready-made, pre-fabricated solutions are typically manufactured out of a plastic-like polyethylene, due to the material's high resistance to corrosion and its inability to rust. Oil absorbent pads, made from hydrophobic materials like polypropylene, can also be effective in providing secondary containment for smaller primary containers.
Larger primary containers will require different containment units, like concrete barriers that can hold significant amounts of oil.
In any case, SPCC-regulated sites should be especially diligent in building and maintaining their containment structures — SPCC fines can be serious, and the environmental cost for not properly establishing proper secondary containment can be extreme and long-lasting.