With oil sand mining facilities producing some of the largest volumes of overburden today, it represents a part of the industry that has a larger than usual impact on the environment. However, careful handling of the overburden is the key to reducing this impact as much as possible. Containment adds to the cost of the handling of the overburden, but it dramatically reduces the expenses for remediation after the fact. Since containment is implemented from the start of mining and actively protects the site, it is easier to budget for than remediation that could occur decades later. Here are the key steps to planning for overburden handling at the oil sands site, complete with containment recommendations from us here at BTL Liners.
Determining Depth
It is not enough to identify an oil sands deposit and begin excavation or blasting without planning for the volume of overburden. Aside from measuring the total square footage or acreage of the area that will be excavated, it is essential to perform depth testing to identify how deep the valuable deposits lie. Most oil sands include multiple layers of valuable oil-rich sand separated by rock or clay. These layers are known as interburden, and they require the same handling as the overburden. Measuring the depth of the overburden and interburden layers allows you to adequately set aside a lined area for temporary containment or a permanent pit capable of holding all of the excavated material.
Choosing Temporary Storage Sites
Both valuable oil sands and non-valuable overburden material is generally piled into tall heaps on the active mining site. Since today’s oil sands fields have evolved to rely on truck and shovel processes, rather than the draglines or conveyor belts used in traditional hard rock mining, it is possible to spread the placement of the heaps over a larger area. While there will be extra fuel costs associated with traveling farther from the active pit, those costs are small compared to the price of extending equipment like bucket systems. Look for natural depressions or areas that are easy to surround with berms to keep water contained. While durable geomembrane liners from BTL Liners are the key to containment under the overburden pile, grading and placement are also key. Grading to contain the runoff from the pile is essential to prevent environmental damage. Plan for stable roads for accessing the storage areas since the process of piling up the overburden is a gradual process rather than a one-time event.
Lining and Sealing the Area
Even compaction and the application of expansive clay materials won’t seal a storage area enough to contain the overburden. While the overburden material isn’t the most hazardous waste that comes from a mining operation, it still deserves an impermeable barrier to keep the trace amounts of petroleum products and heavy metals from leaching out into the environment. Geomembranes with a high impermeability are key to containing and sealing the storage area. BTL Liners has the industrial grade liner materials for this kind of high demand installation. Our reinforced liners can handle the abrasiveness and weight of the overburden heaps without stretching, tearing, or sliding out of place.
Avoiding Loss of Valuable Material
Taking care to handle the overburden correctly on an oil sands project prevents the loss of potential profit in multiple ways. First, proper identification of the overburden vs productive layers ensures there’s no loss of the actual oil-rich sands. It is possible to remove the first few feet of the productive layer if it is misidentifying as overburden. On the other end, mixing in low-grade overburden into the productive oil sands also increases production costs and eats into the profits. The more accurately the start of the oil sand is identified, the higher the profit to cost ratio will be for the mine.
Second, overburden material itself does have some value. Even if it is just needed to refill the mined area and restore the natural habitat, the material must be held in place and not lost through erosion or wind scouring. If the overburden material will be sold for construction use in other projects, losing any of it can eat into the bottom line of the operation. Either way, keeping it in place requires a lined basin or berm-surrounded storage zone. Temporary storage also allows for grading and reclamation of any valuable productive material that might be accidentally mixed into the overburden.
Water Removal Through the Overburden Layers
Water mixed into both the productive and overburden layers needs removal before the dry material is excavated. Multiple wells are usually drilled through the material to access the reservoirs of water or other liquids. Pumping may take weeks to months to dry out the underground layers enough to begin excavation. Without proper water removal, overburden often comes out as a slurry that is hard to handle and requires processing before it is valuable for site remediation or construction. Pumping the water up while it is still underground is generally less expensive and easier than above-ground dewatering operations for the oil sands and overburden.
Post Mining Recovery
Oil sands can struggle with post-mining recovery since large areas are excavated at once. Minimizing loss of the material removed during excavation ensures that there’s plenty of fill to cover up the depression. However, the missing oil sands still make it hard to restore the full surface of the area and make the signs of extraction disappear. Moving in fill material from other grading and construction sites can help speed up post mining recovery while making the most of the overburden that is available on-site.
Oil sand mining has a reputation for environmental damage that is not necessarily deserved. Due to the potential for site recovery and remediation with the help of overburden, it is often possible to restore an oil sands back to nearly its original condition. This allows for access to valuable sources of oil without the risks and environmental impact of deeper forms of mining. Make sure there are no issues with the huge volumes of overburden material created by the oil sands by building secure containment areas. Start with a layer of geomembrane from BTL Liners to prevent unexpected environmental impacts until it is time to close down the mine and restore the site.
