While geomembranes are practically required by many of today’s modern mining projects, they’re not without installation considerations. Certain challenges can pop up during the installation process and slow down the work or halt it altogether. With the high cost of labor and equipment rental, delays can add up quickly for the mine owner. Preparing for common installation challenges will help you avoid these issues, or at least have solutions on hand for dealing with them.
Rocky and Uneven Soil
Rocky, stone-filled soil is one of the most challenging installation conditions. Even the best geomembranes and reinforced liners can tear during installation or wear punctures that develop after a few years of use. The stones in the soil may seem small or somewhat smooth, but the rough surfaces of the rock do a lot of invisible damage to the geomembrane as it’s dragged over them. Improper grading and poor leveling practices also create uneven support for the liner. Trying to remove large or sharp rocks without re-grading the soil often leaves voids just the surface. Even a small void of a few inches in depth allows the liner to bulge out, creating a stress point that can become a leak over time. Taking extra steps to smooth and grade the soil and installing a cushioning geotextile underlayment are two options for preventing this kind of damage.
Collapsing and Shifting Soils
Some projects achieve smooth and perfectly graded pond forms only to watch the liner dip and tear as voids form below the surface. Adding the high weight of the water or waste material to the liner quickly shifts loose or wet soils that aren’t ready to bear the stress. Collapses that occur around banks can release the wastewater or other contained material to create an environmental or health hazard. Even small collapses under the middle of the pond structure pose the problem of creating new leaks. Testing the compaction and composition of the soil before installing anything is essential to ensure it can bear the weight of the finished pond, tank, or leaching pad.
Individual and Total Storage Volume
The sheer size and high-volume requirements of the mining industry make it hard to plan and build leak-proof ponds. It’s hard to keep track of every inch of liner-covered base and bank, especially when dealing with multiple ponds covering dozens of acres altogether. Spreading the liner over so much area reduces the amount of attention paid to any one spot that might be damaged or have a weak seam. Increase labor, enlist expert help on the project from BTL’s experienced team or turn to technology like drones to keep track of the installation process over a large area. A little more time and labor put into quality control during installation will pay off for the lifespan of the pond in reduced repairs and maintenance.
Chemical and Mineral Mixtures
The combinations of corrosive chemicals and abrasive minerals commonly found in mining ponds and basins are tough on the liners used to contain them. Even the best materials, such as ArmorPro from BTL Liners, face higher wear and tear when used in the mining industry. When renovating older mine process and storage ponds, the new liners will often come in contact with existing residues of chemicals or sediments. Taking the time to remove these residues can increase the lifespan of the new liner by reducing both chemical and mechanical wear. A sacrificial layer of an inexpensive geotextile in between the old and new liners can also help and usually takes less time to install than a thorough cleaning would require.
High Weight Loads
Between the weight of the water, mixed in waste products, and any deposited sediment or ore, the liners in mining ponds are constantly under a heavy weight load. This leads to tearing, splitting, stretching, and increased seepage as tiny pores open up in the surface. Reinforced liners, especially those made from a combined polyethylene formula, are best at resisting the long-term effects of this pressure. Reinforcement grids work in all directions to distribute the force rather than letting it build up at one point that tears or stretches.
Leak Detection Equipment
Since mining waste and active processing material are both highly hazardous to the environment and human health, it’s essential to catch leaks in containment systems as early as possible. This means that many states require passive or active leak detection equipment built into each holding tank, pond, or other structure. Double layered geomembrane is commonly used for this system with drain tile or a textured geotextile in the middle to keep the gap open. Test wells are added at certain intervals to capture any water. This is also where the sensors are to trigger alarms that alert you to the leaks. The bottom layer in this system must be reliable enough to trap any accumulated liquid and act as secondary containment. For good results, consider using the same RPE material for both the upper and lower layers of the leak detection system.
Secondary containment requirements are strict across most of the mining industry due to the hazards of the waste produced by the facilities. Whether the mine is producing metals, salt, minerals, fertilizer, or even uranium, the resulting runoff and processing water can’t escape into the surrounding environment. This means that secondary containment methods are often larger and more advanced than those used in other industries. These containment methods often have to link together in some way to meet the volume requirements set by the state or federal regulations as well. Make sure to choose a liner that can handle deep burying if you plan to use one as your secondary containment method. Weight and rough soil can tear weaker materials when they’re used for this kind of buried installation, but RPE products can handle the challenge.
Heavy Equipment Use
With the sheer size of most mining ponds calling for liners that weigh hundreds to thousands of pounds, heavy equipment is often required for some or all of the installation process. Yet the very use of this equipment to carry and spread out the material also increases the chances of damage before the pond is ever filled. Planning out heavy equipment use and coordinating access paths is essential to avoid driving tracks and tires over the geomembranes. Even foot traffic can create punctures when the material is stretched against a rock or void by the person’s weight. Limit traffic over the surface once its covered by planning to work from the center outward in multiple teams.
Seam Sealing on the Job Site
Trying to seal hundreds of linear feet of seams between pieces of pond liner can double the installation time alone. It’s always best to reduce the number of seams that need sealing on site, regardless of the type of pond or containment area you’re building. Custom fabrication from the manufacturer is the best way to do this. Larger sheets of continuous material are heavier and turn into larger folded stacks, but they’re worth the extra work to transport and unfold. Reducing seams as much as possible on a project also reduces testing and maintenance work for the lifespan of the structure, in addition to streamlining the installation process.
Many engineering specifications for large scale holding ponds and tanks require concrete for its stability and strength. Yet concrete alone isn’t a good liner for any kind of mining application. First, concrete is naturally porous due to the formation of tiny holes that create a capillary effect through the material. This means that seepage is a major problem with uncoated concrete liners. Second, concrete is also reactive to many chemicals and ingredients found in various mining fluids and waste products. Spalling quickly leads to cracking that weakens the entire concrete structure. Adding a combination of protective coatings on the surface and geomembranes under the concrete can solve both problems at once.
Don’t let the challenges of mining geomembrane installation hold you back from using it on multiple parts of your project. It’s a great lining choice for everything from small channels to full-sized storage ponds. If you need to know more about proper installation practices for RPE geomembranes, contact us here at BTL Liners.