Complete and absolute containment is the only acceptable standard for managing waste clearly identified as toxic. This includes mining waste, wastewater from heap leaching tanks, ash dumps, and tailings ponds. Washing tanks and sedimentation tanks are also directly exposed to toxic materials and water that comes in contact with those is considered contaminated as well. Water and other liquids collected or employed in petrochemical plants, refineries, and oil storage tanks are known to contain hazards ranging from heavy metals to naturally occurring radioactive material (NORM). RPE liners are popular in many of these applications since Storage facilities in chemical plants and chemical reaction tanks are often suited to RPE geomembrane liners, since they’re inert to many chemicals and highly resistant to degradation from many more.
Oil and Gas
For the oil and gas industry, including refineries and chemical plants, liner degradation from reactions with certain lining materials can be an enormous problem. It’s necessary to choose your liner materials based on the exact character of materials you plan to contain, but RPE composite liners are resistant to a wide variety of chemicals, including corrosive effects. This makes RPE an attractive and affordable solution for both primary and secondary containment systems in many applications.
Salt
Salt is a highly corrosive substance, particularly in high concentrations, which is a concern when salt solutions must be stored or evaporated. Evaporation ponds, salt field crystallization ponds, and brine ponds are all employed to store liquids with high (and increasing) concentrations of various salts. Evaporation through exposure to the sun, while highly energy efficient, isn’t particularly fast, and individual salt ponds may be in use for years or even decades. During their lifetime, evaporation pond liners must endure corrosive conditions, exposure to sunlight, and mechanical abrasion as salt crystals are harvested from the bottoms of the ponds. The right RPE liner material is ideally suited for this range of challenges, including direct UV exposure.
Secondary containment protocols are also required since concentrated salt is highly toxic, and RPE is both affordable and easy-to-work-with for this use.
Wet Contaminated Materials
When contamination has been detected in soil, sludge, or even in stormwater or other normally benign materials, that material must be stored and handled according to safety protocols defined for that toxin. Just like for ponds and landfills, it’s important that water is prevented from entering the impoundment to avoid leaks, flooding, or even increasing the amount of contaminated liquid. Lined in-ground ponds and lagoons, or above-ground storage structures are the first layer of protection, followed by impermeable covers that are designed to withstand winds, cold temperatures, and accumulated rain or snow. Then, a secondary containment system is necessary in case the primary system develops a leak or structural damage, or even if a major storm incident brings unprecedented rainfall and flooding.
Ore Processing
Heap Leach pads are permanent structures used for the extraction of metals or for the permanent storage of waste products produced during mining and processing ore. Waste materials left over after processing are known as tailings or slag. Because metal ores naturally include heavy metals, radioactive material and other toxic materials and are processed with a variety of acids, the leftover tailings must be permanently guarded against contact with the underlying soil and from exposure to rain. Any rain that does make it onto an ore processing or leach pad will pass through the ore and tailings, picking up (leaching) a variety of toxic contaminants, potentially carrying it into the local environment or passing through to groundwater.
To prevent this, heap leach pads are constructed with a base layer to separate the soil from the bottom most layer of tailings. When the ore is processed, leachate is collected in pipes, lined solution channels, or an adjacent collection ditch - also carefully lined - whence it is pumped into processing ponds where valuable components are removed.
Considering the multiple types of toxicity found in mining tailings, complete containment is critical. Liners chosen for this kind of application must be able to tolerate the extreme weight of ore stacked hundreds of feet high. Repeated exposure to acids and other highly corrosive materials cannot degrade or weaken the liner, and the liner must continue to perform under these conditions over time, even in the event of harsh weather and extreme temperatures.
Animal Waste
Large livestock operations produce enormous amounts of solid waste that includes, not only manure, but bedding waste, antibiotic residues, cleaning solutions and other chemicals, and even dead animals. Historically, this kind of waste has been managed by storing it in open ponds, called lagoons, where it’s expected to decompose over time. Ideally, once the waste has been thoroughly broken down, the nutrient-rich liquid is pumped out and applied to growing crops.
Animal waste lagoons are rarely lined with anything more than natural clay, and leaking is an endemic issue. In small farming operations with a dozen or so cattle or pigs, these waste lagoons may fail from time to time, but the impact is generally fairly local and doesn’t gather much attention. According to EPA definitions, however, large factory farms house at least 1000 cattle, 2500 hogs, or 125,000 chickens in a single operation. The thousands of tons of animal waste generated in these operations present real risks to the environment and public health. Across the country, events as unexceptional as a series of heavy storms have been known to trigger the failure of dozens of animal waste lagoons, leading to wholesale release of millions of gallons of untreated sewage.
Farmers who focus on their role as environmental stewards and others who want to ensure they’re taking all possible steps to limit any potential legal exposure (especially as awareness of the harm caused by the operation of uncovered animal waste lagoons has spread), realize that animal waste must be properly contained and treated, just as human waste or other hazardous materials. A robust, durable, and impervious liner like RPE can prevent both leaks and gradual seepage from a waste lagoon into soil and nearby groundwater. A well-designed secondary containment system can manage heavy rainfall and even eliminate flooding. This is accomplished by deploying geomembranes to cover active lagoons and diverting stormwater around the lagoon area with the use of lined berms and ditches.
