Excavators are most commonly used for earthmoving and digging projects. When used at their full…
What happens after a mine is closed?
A mine’s window of usefulness may last a few years or a few decades. However, once the mineral resources are exhausted or operations no longer profitable, crews can’t just pack up and go home. State and federal agencies have regulations that dictate the correct way to shut down, decommission and remediate a mine.
After closure, a mine may be reclaimed for other uses or restored to its pre-mining condition. Most regulatory agencies require a mine closure plan before a mining permit will even be granted. Regulators might also need a financial guarantee that an operation can pay for the reclamation and dewatering processes involved in a successful mine and pit closure.
Note: Louisiana’s major “mined” products are petroleum and natural gas. We also extract sulfur, salt, coal, sand and gravel. So when we refer to “mining” in this article, we could be talking about the surface mining of materials used to build roads and produce concrete, or we could be referring to hydrocarbon extraction for the oil and gas industry. The fundamentals of mine and pit reclamation and dewatering remain the same.
Mine Closure Process
It typically takes years to shut down a mine properly but can take more time if long-term wetlands monitoring or water treatment is required. Mine closures involve the following steps:
- Shut-down: When production has ceased, some workers or contractors will stay at the site to shut down operations and remove equipment;
- Decommissioning: In this stage, pipelines are drained, equipment and parts cleaned and removed, buildings and other structures repurposed or demolished and waste removed from the site;
- Remediation/reclamation: This stage is a long process intended to return the land to an acceptable standard of productive use, and that nearby water sources have satisfactory water quality. Reclamation workers must remove hazardous materials from the site, restore topsoil and plant native grass and trees. Click here for Louisiana’s recommendations concerning high walls, spoils and embankments at abandoned mine sites (PDF);
- Post-closure: Ongoing monitoring programs will determine if reclamation measures were successful. Long-term maintenance processes might include treatment of mine discharge water, periodic monitoring of the effects of ore and other residue left behind, and the evaluation of the progress of coastal remediation efforts.
Mine and Pit Dewatering
Mines, quarries and pits can adversely affect groundwater and surface water in various ways.That’s why mining operations are responsible for capturing and treating contaminated water and mine sediment on-site.
Developing a mine below groundwater level can also present operational challenges, which dewatering can address. Mine dewatering means employing groundwater control techniques like in-pit pumping, perimeter dewatering wells to intercept lateral groundwater flow into the pit and to lower groundwater levels and cut-off walls (slurry walls that hold groundwater back from deposits). Mine dewatering can help by:
- Reducing downtime caused by pit flooding;
- Reducing blasting costs;
- Reducing haulage costs (dry ore and waste rock weigh less when they’re dry);
- Improving slope stability and safety (lower groundwater levels allow steeper slope angles to be used).
Mini-excavators and dredgers can work underwater and in shallow water to assist mining operations with dredging and dewatering efforts. Mechanical dredging by MSHA-certified operators keeps tailing ponds clear, while the same machines can build levees, dikes, embankments, floodbanks or stopbanks to control water flow and keep excavation operations dry.
For more information about reclaiming mined lands and protecting the environment, including initiatives to promote wildlife habitat and ecological remediation in Louisiana, contact these offices: