Few other ponds have the stringent demands for liner durability and damage resistance of processing ponds. There’s consequences for improper liner selection, that leads to a leak, are also much higher. This is why it’s so important to get liner selection right the first time when building any kind of processing ponds. Here’s a quick guide to your options for flexible and rigid liner materials for use in the mining industry.
Clay and Natural Liners
The layers of compacted clay soil and bentonite clay used for many backyard, decorative and fish ponds are not appropriate for most industrial uses, including mining processing and refining. These materials are simply too easy to disturb, too likely to blend and mix with the sludge, and too permeable to work well in delicate environments like these ponds. There’s also expensive when you consider ponds need anywhere from 10 to 24 inches of clay to stay even marginally sealed against leaks. Clay liners simply aren’t reliable enough for something as important as gold or silver ore recovery.
Concrete may seem like the ideal material for sealing and finishing the ponds and ditches of the processing system. However, it’s not quite as durable and long lasting as many mine owners assume. It’s also a high maintenance material that is prone to algae growth and other issues. Concrete is particularly prone to developing small hairline cracks that are hard to find. Despite their small size, these cracks eventually contribute to sizable leaks that threaten the entire facility. Sealing concrete isn’t an easy solution when dealing with active processing ponds and a waste management cycle that needs to repeat regularly.
Flexible, polymer-based liners work best for most mining processing purposes, including leach pads, drainage ditches, and processing ponds. Of course, this is only true if you select the right material. Some flexible liners will perform less reliably than concrete if installed on their own. For a long lasting liner you can trust for reliable, leak free containment, stick with multi-layered, reinforced, quality liners.
Polyvinyl chloride, better known as PVC, is a slick and shiny material that is soft enough to fit into sharp angles and tight corners. Unfortunately, it’s not the toughest material for making flexible liners. It has to be twice as thick as RPE to offer the same wear and tear resistance. This extra thickness adds up quickly to dramatically increase the weight of the liner. When installing multiple acres worth of liner in a short timeframe, even a few extra ounces per square foot of liner make a big difference. Lighter liners allow you to work by hand rather than with machines, reducing leaks caused by the heavy machinery itself.
Ethylene Propylene Diene Monomer (EPDM) rubber is a thick material that is far less flexible than PVC or RPE liners. It requires this thickness to resist damage from chemicals and UV rays, and it’s still not particularly great at handling either. These heavy liners are expensive to ship and require heavy equipment for installation on a large scale. They’re also incompatible with heat welding, which is one of the most reliable ways to seal seams on site. In general, EPDM liners are rarely used for any applications in industrial settings unless there’s a specific chemical compatibility needed that only this rubber can provide.
A multi-layered reinforced polyethylene (RPE) product is the best fit for the demands of the processing pond. Whether you’re storing pregnant solution for treatment or barren fluid for reuse, the combination of multiple layers of both high-density polyethylene (HDPE) and low density polyethylene (LDPE) creates an unbeatable barrier against leaks. The reinforced material is also far more tear resistant, making it ideal for ditches and collection areas where machinery regularly operate. It offers the best combination of UV and chemical resistance, and some products are even designed for exposed installation. RPE is thinner and lighter than other flexible liners, allowing for accurate coverage of curves and edges during an easier and quicker installation process.
Cover for Liners in Processing Ponds
Many mining, processing ponds specify exposed liner installation in order to make it easier to remove residual sludge and silt as needed. However, you’ll need a liner capable of handling that amount of UV exposure before planning for this kind of installation. It’s far more common to install a ballast material. In a processing pond where it’s necessary to remove as much ore as possible, adding sharp gravel or uneven rock as ballast could interfere with flow rates and trap valuable material. Small pebbles and smooth river rock are better choices since the slick surfaces minimize flow loss. Sand is another good option for an easy to maintain ballast that is widely available.
Making a flexible liner selection takes more consideration than many assume. If you’re still not sure which material is right for your particular project, reach out to us here at BTL Liners. Our team is always ready to make recommendations for liners based on our years of experience in the industry.