Selecting the right liner material is important for every pond, impoundment, and other water-holding area. But it’s downright essential when you’re dealing with millions of gallons of potentially hazardous waste. Frac pits are exposed to more chemical and physical damage over time than the average pond, so they also require more durable liners. Using a liner that’s only rated for general pond use will result in quick failure, even for temporary frac pits only designed to operate for six months or less. Even the most temporary produced water storage pits and ponds need hydrocarbon resistant liners to prevent hard-to-detect leaks. Instead of settling for the first liner that claims to offer gas and oil compatibility, use these tips to make sure you’re choosing a product that will last for decades if necessary.
Clay Liners Are a No-Go
First, any product based on clay liquids or powders is unlikely to provide meaningful lining power for a frac pit or pond. It’s simply too easy for water to continue penetrating through these materials since they’re not actually impermeable. While 12 or more inches of bentonite clay can stop some amount of water from seeping and leaking through, it won’t entirely control water loss. This is a problem when you’re dealing with potentially hazardous waste like produced water. Even small amounts of seeped or leaked produced water can lead to costly fines from environmental agencies. Clay liners are also easily disturbed by water currents or equipment used for water treatment and sludge removal. Even products that combine natural clay with flexible fabric bases are too unreliable for use in the oil and gas industry.
Concrete and Frac Ponds
Concrete is sometimes used for stabilizing the banks or sides of frac pits and ponds, but it’s not actually intended as the liner material. This is due to its natural tendency to slowly lose water over time as it seeps out through capillary pores in the cured material. These tiny tunnels create a slow leak effect similar to a sponge sucking up water. Concrete is perfectly fine to use around the frac pit if it’s paired with a flexible liner with proper impermeability. The weight and strength of the concrete are great for supporting loose soils that might shift when just covered with a lightweight liner, but it’s not enough to use alone for lining a pit.
Why Flexible Liners?
There are dozens of reasons to choose flexible polymer liners for lining frac pits, including:
- Formulations with high UV resistance to allow for exposed installation that is common for these ponds
- Reinforced designs that can handle steep slopes and rough soils with reduced risks of tearing
- Chemical resistance against hydrocarbons, acids, fracturing chemical additives, and more, when the right material is selected
- Varying thicknesses to ensure the right window of longevity and durability depending on the need for temporary or permanent storage
- Ease of welding panels and sheets together on site for custom fabrication at any scale
- Affordable pricing per square foot when compared to other high-demand lining solutions.
Reinforced Materials
Even though most frac pits and pads are only in active use for six months or less, a lot of wear and tear can occur to the liner in such a short time frame. Some high demand pits may be emptied of sludge multiple times during that period to maintain the pond’s capacity to accept further flowback. Reinforced liners are recommended for frac pits for this reason in particular. Additionally, the reinforced design also helps during installation. Reinforced liners offer better lay-flat ability, which helps the material relax and spread on its own to release wrinkles that can damage the material. They’re just as easy to seal along the seams as other materials, especially when made from polyethylene. The heavy weight of settling solids and sludge won’t cause the liner to shift or distort as long as it’s properly reinforced.
Finding Hydrocarbon Resistance
Hydrocarbon resistance is perhaps the single most important feature to look for in a flexible liner for a frac pit. As mentioned before, even fresh water frac pits are at risk for exposure to oil or gas if there’s a substantial spill from the drilling pad. All of the liner materials used on a gas or oil site should feature good hydrocarbon resistance to prevent unexpected failures and leaks. Unfortunately, each polymer commonly used for manufacturing flexible liners varies in oil damage resistance, depending on the specific formulation. For example, one PVC liner may be somewhat hydrocarbon resistant while the next is completely susceptible to damage from it. Look for testing on the specific formulation from the manufacturer to verify the product you select can live up to the claims of hydrocarbon compatibility.
Which Polymer is Best?
Selecting the right polymer for a frac pit liner requires more than just selecting a broad category. However, you should start by narrowing down the options by material alone. Here are the most common pit liner materials and how they stack up when it comes to using them for hydraulic fracturing ponds.
- Reinforced polyethylene (RPE): RPE is the best choice for all frac pits, regardless of the composition of the fluid they’re designed to hold. This material offers the best hydrocarbon resistance, ensuring that even long-term storage won’t cause reactions that lead to broken and leaking liners. It’s available in thinner sheets, than other materials, because its reinforced design offers strength at a lower weight for easier installation and lower shipping costs. On large frac pit lining projects, this can make a significant reduction in project expenses.
- High- and low-density polyethylene (HDPE and LDPE): RPE liners are made with a combination of both HDPE and LDPE, but these two polyethylenes aren’t as durable when used alone. HDPE is stiffer and strong, but its lack of flexibility can lead to cracking as weight presses down on the material where it’s folded or bunched. LDPE is more flexible, but it doesn’t have as much chemical, UV, or stretch resistance. Neither HDPE nor LDPE can completely compete with RPE for lining frac pits.
- Polyvinyl chloride (PVC): PVC is commonly used for recreational and decorative ponds, but it’s not designed for the rigors of industrial use. Frac pits lined with PVC are prone to leaking because most formulations of this polymer are fairly reactive to hydrocarbons of all types. Even the PVC varieties that offer good hydrocarbon resistance tend to suffer from UV damage susceptibility, limiting their ability to be installed in an exposed way. PVC also lacks durability and strength, in general, when compared head-to-head with RPE.
- Reinforced polypropylene (RPP): RPP is commonly mistaken for RPE, but it’s a slightly less durable and much less chemical resistant product. It offers good puncture resistance and high durability thanks to the reinforced design, but the polypropylene isn’t as UV or chemical resistant as polyethylene. RPP can be used for the most temporary of frac pits and those designed for holding fresh water. However, RPE is a far better choice since it’s more likely to withstand the daily rigors of filling and emptying the pit with abrasive sands.
Any liner is better than no liner for a frac pit. However, putting in PVC or RPP will likely only be a temporary solution that leaves you dealing with expensive cleanup later. Start off right, with RPE from the beginning, by ordering all the frac pit liners you need from BTL Liners. We offer custom fabrication to help limit the number of seams in the sheet covering your pit or pond. This speeds up installation and reduces the chances of leaks at the same time.
