If you’re looking at the cost of building multiple containment basins for your oil field, you may wonder why you need concrete or flexible polymer liners at all. It’s true that in the past many oil fields only had rammed earth basins and dikes to contain spills and leaks. This method is still used today in many parts of the country where the EPA has deemed it impractical for older facilities to upgrade. However, relying on raw earth alone is a big mistake when it comes to secondary containment. Even concrete basins and dikes alone aren’t a good choice when you need to keep oil and gas in. Find out why you can’t simply build a bund wall or some dikes around an oil field and call that satisfactory for secondary containment.
The Limits of Dikes and Bunds
Dikes, bunds, and berms are all raised structures designed with the sole purpose of holding back a liquid or sludge. It’s possible to dig and create depressed basins inside to hold liquids for secondary containment, but almost all oil and fuel fields will have such high volume that raised structures are also necessary. Yet, even an appropriately sized wall isn’t all that’s needed for containment. Almost all construction methods for berms, dikes, and bunds leave them porous in some way. Seams between concrete blocks or tiny cracks in poured concrete still allow oil and fuel to escape and seep into the soil or water around the containment area. All raised structures need secondary sealing, preferably in the form of a flexible polymer liner, to truly qualify as watertight and to meet the EPA’s main requirement for containment.
Risks of Overfilling
It’s hard to predict how much oil or fuel might escape during a leak. It’s impractical in almost all cases to build a containment basin large enough to contain 100% of the volume of an oil field’s production. This means you simply have to accept that berms and walls might end up oversized for the volume and overtopped by the flow. Lining the basin ensures that it’s possible to clean up and repair the raised structures after an overflow event. While unlined dikes and berms may hold up when overfilled, they also may shift and collapse without the extra reinforcement of a flexible liner. The sheet-like design of a liner helps spread the weight of a sudden flow of liquid so it’s not pressing just on one part of a wall or berm. While you should always design the containment system to prevent overfilling whenever possible, a liner is still worth the extra protection in case it’s inevitable.
Collapse and Access
Speaking of shifting and collapsing, earthen dikes and berms are always particularly at risk for this problem. They can become so unsafe that it’s hard to maintain the oil field equipment or properly transfer the crude oil to another facility. Earthen structures absolutely need flexible liners to hold them together and protect them from the constant erosion effects of rain and runoff. Spray-on polymer products have become popular in the last few years for holding compacted soil together when it’s used for compacted structures. However, these products can’t compare with a real RPE liner for the purposes of secondary oil and fuel containment.
The single biggest problem with relying on concrete or rammed earth alone, whether as a basin or as raised structures, is seepage. All of these materials lack true impermeability and allow liquids to seep through the tiny particles that make them up. Polymers are as impermeable as you can get in a real-world situation. When it comes to dealing with hazardous waste like oil, fuel, and their byproducts, you can’t rely on the somewhat porous materials of earth and concrete alone. Make sure you are adding at least one layer of impermeable liner to actually control and trap seepage. Seepage is different from leaking, which occurs when there’s a crack or other common issue. Concrete and earth will seep even when it’s performing as intended unless it is sealed or lined. Sealants wear off unevenly and are hard to reapply, so stick with liners from industry leading sources like BTL Liners instead.
Concrete vs Earthen Dikes
Earthen dike structures are popular for containment purposes like oil and fuel fields because they’re very inexpensive. They’re usually formed right from the dirt of the field itself, making good use of leftover piles created by drilling and clearing. They go up quickly and require common equipment for shaping and packing. Unfortunately, all these benefits are outweighed by a host of disadvantages. First, they’re highly unstable and prone to collapse. This is a safety hazard for workers on the oil field, especially those driving large vehicles that are hard on compacted earth structures. Second, the earth is always porous enough to allow leaks to seep through, even after being coated with various sprays. Lining fixes this problem but can’t address the other issues. Finally, earthen dikes aren’t allowed by most state regulations anymore. They’re simply not reliable enough when compared with concrete dikes, especially those that are properly lined with flexible RPE products.
You’ll definitely need dikes, bunds, and berms for a complete secondary containment system at your oil field. Just don’t assume that they’re the only structures you need to add. Make sure you integrate reliable liners from BTL Liners into their design to ensure they last for years to come through wear and tear.