While the EPA mandates a wide range of different complementary oil containment methods, most of them work best when flexible liners are involved. Even the most durable berms and dikes deserve containment grade liners to ensure that not a single drop of oil seeps past the barriers and into the soil or groundwater. Yet, not all flexible liners used for pond lining or storm water containment work well for the much more challenging environment of the oil storage facility. Choosing the wrong flexible liner will only result in a large-scale leak that comes with costly fines and fees. Make sure you’re installing the right flexible liner for primary and secondary oil containment with these tips.
Sizing Containment for Oil
Check the sizing requirements set by the Environmental Protection Agency (EPA), state agencies, and any local authorities and then go with the largest volume set by any of the various regulations. Under sizing your containment area won’t just leave you facing fees from an agency, it could also increase your cleanup and remediation costs if there is a spill. The EPA tends to have the most generous sizing requirements for oil containment, but some states require even more holding space. If you’re working with the EPA’s guidelines as the sizing requirements for your containment area, they offer simplified calculations on their website to determine the total volume needed to meet the regulations. These calculations are based on basic containment basin designs with 90-degree walls/berms/dikes, so you’ll need an engineer’s help to calculate more unique and unusual designs.
The Power of Flexible Liners
Flexible liners are widely used as secondary containment for all kinds of hazardous and valuable liquids, including fresh water supplies, manure lagoons, and more. While liners are often just one part of a larger oil containment system, they provide the most valuable function; serving as the impermeable barrier to control liquid loss. Without an impermeable liner above or below the surface of a containment system, seepage will occur into the surrounding soil and water due to tiny openings in materials like concrete and asphalt. When selected to withstand the stresses of oil containment areas, these liners are tougher than spray-on sealants and provide longer years of reliable performance.
Which Liner Material Works Best for Oil Containment?
Oil and its byproducts are challenging liquids to contain, both at the primary and secondary stages. Hydrocarbons tend to react with petroleum-based polymers because of solvent effects from the similar chemical compositions. Some polymers are prone to this form of corrosion, while others are completely resistant to it. This means that picking the right material for all containment liners and layers is essential. A single misplaced material with poor oil or fuel resistance could lead to a leak that jeopardizes the entire containment system. Here are some of the most common options available for oil containment and how they stack up against each other.
Reinforced Polyethylene (RPE)
Reinforced polyethylene (RPE) is the best, flexible liner material to use for secondary containment. It can also work well when used to line or repair primary containment vessels as well. This material offers some of the highest levels of chemical resistance, including against hydrocarbons and oil, that is superseded only by ethylene interpolymer alloys (EIA). It’s far more affordable and widely available than EIA liners, making it easier to adapt a secondary containment system for remote oil refineries or refueling stations. The reinforced design makes it far more puncture and tear resistant than other flexible liner materials with good chemical resistance. With the right formulations, RPE liners also offer enough UV resistance to last 20 years or longer in an exposed installation. The material is easy to cut and seam on site to fit around dozens of protrusions, pipes, and tanks for a custom liner application with less work. This makes it an equally good fit for new oil storage systems and retrofitting of older areas.
High Density (HDPE) and Low Density (LDPE) Polyethylene
High density (HDPE) and low density (LDPE) polyethylene are both used in the creation of RPE liners, but they’re also sold separately as mono-polymer liners. It’s tempting to choose one of these polyethylene products over RPE because they’re often sold at a lower price point due to the ease of manufacturing. However, the lack of reinforcement will inevitably mean that even tough HDPE liners will tear and crack more readily than an RPE liner. In an oil containment system, a single crack or tear could result in thousands of dollars’ worth of fines after a spill. LDPE has good chemical resistance but lacks the strength and durability of RPE. It’s highly flexible, but so are many forms of RPE. In fact, RPE liners are often as thin or thinner than LDPE liners while offering greater strength due to the reinforced design. Thinner liners are easier to install and conform better to the dikes and walls built to hold oil and other liquids in.
Polypropylene (PP) offers good chemical resistance. It’s one of the most widely used polymers for small storage and transfer containers, along with temporary oil containment measures like boxes and mats. However, it’s not appropriate for use on a large scale like a flexible liner due to its relatively low strength and tear resistance. Many PP liners are available for other pond lining purposes, but they’re not generally recommended for commercial oil containment. You’ll find this material more commonly used for floating booms and other offshore oil containment measures used on open water when a platform or ship leaks into the sea.
Polyvinyl Chloride (PVC)
Next to EIA and RPE liners, polyvinyl chloride (PVC) is the third most widely used material for oil containment. It’s often found as an element of primary containment when flexible sheets of PVC are adhered or clipped to the interior of an aging metal or concrete storage tank. For secondary containment, especially in exposed installations, it’s not as versatile as RPE or as tough as EIA. The flexibility that makes PVC a good choice for lining the interiors of tanks can backfire and cause it to stretch or tear when used to line an exposed berm or dike. Many PVC liners are also far more susceptible to UV degradation than RPE products. Even for tank lining purposes to reinforce primary oil containment measures, you’re likely better off choosing RPE or EIA than PVC.
Ethylene Interpolymer Alloy (EIA or XR)
Ethylene interpolymer alloys (EIA) are also commonly known by the trade name XR. XR-5 in particular is the EIA liner material recommended for cold and hydrocarbon resistance. These liners are some of the only materials that can compete with RPE in terms of durability, chemical resistance, and UV resistance. However, they also tend to be much more expensive and less widely available than RPE. When working on a budget or with short deadlines for manufacturing, it’s generally much easier to stick with RPE than to try and source a custom EIA solution. You may need to combine both RPE and EIA in the same system to meet all of the regulations set by the EPA and relevant state agencies. This is especially likely in arctic environments where extremely low temperatures make it challenging to keep oil pits and ponds lined. In most cases, RPE will perform for almost all situations where EIA is recommended.
Basins, Ponds, and Other Containment Features
The shape and size of the basin, pond, or other containment feature plays a large role in selecting a liner. RPE is recommended for steep-sided and 90-degree angle walls since its combination of stiffness and flexibility is ideal for staying upright while still conforming to a tight curve. Consider the difficulty of cutting and joining seams on site when selecting a material as well. Even with custom manufacturing, it’s likely that many protrusions and corners will be cut and sealed during the installation. Materials that are easier to chemically bond with boots and other protective covers, such as RPE, result in reliable containment measures that pass inspection the first time.
Prefabricated vs Custom Liners
Even when dealing with a relatively small storage or loading area that needs secondary containment, finding a source for custom liner fabrication can make the process go much more smoothly. Trying to buy pre-made rolls of liner material and seaming them all together results in many more opportunities for leaks. Custom fabrication minimizes seams so that the entire containment area is covered by as few individual pieces of the liner as possible. Whenever it’s possible, a single sheet is recommended to create an impervious membrane below all tanks and storage containers. Of course, this is usually only achieved when building a new storage facility from the ground up. If it’s necessary to cut and fit the liners around dozens of tanks and other obstacles, it’s less important to have a single sheet manufactured. However, you’ll still want the widest possible rolls of liner material to limit seams and speed up installation. If you need strips of the liner that are more narrow than usual to fit between tanks, that’s another reason to choose a manufacturer offering sizing specific to your needs.
Preventing Damage from Foot and Vehicle Traffic
Buried and below grade liners are rarely at risk for damage from traffic, but exposed liners can easily become torn or worn by feet and vehicle tracks. If you can’t cover the liner with a layer of concrete or soil to protect it, ensure that you’re using a reinforced product that can handle the change in weight without ripping or tearing. Installing cover boards or platforms can also help with foot traffic, but they’re rarely available in sizes that allow vehicles to travel over a liner. If the containment area is also used as an access point for vehicles loading or unloading oil, consider a buried installation to keep constant traffic from wearing out the liner.
Don’t let the many considerations of containment liner selection overwhelm you. We’re happy to help with all your oil containment questions here at BTL Liners. Contact us today to find out why RPE is such a great material for protecting water and soil from the risks of accidental oil leaks and spills.