By Leia Toovey- Exclusive to Gold Investing News
Once the gold reserve at a mine has been exhausted, the owner of the mine must rehabilitate the site. Rehabilitation refers to the process of returning mined land its preexisting condition or to a predetermined post-mining use. Closure plans are devised prior to mine operation but are adjusted during the operational phase to account for various changes in mine operation, including mine lifespan and economics.Rehabilitation is a process that is required by governments and mine is contingent on the miner proposing a feasible rehabilitation program prior mining activities. In addition to proposing a proper rehabilitation plan, most governments require companies to provide financial assurance to cover some or all of the costs of the anticipated rehabilitation program.
A properly laid out rehabilitation program has clearly stated objectives. Broadly, these objectives are: the protecting ensuring public health and safety, minimizing environmental effects, removing wastes and hazardous materials, preserving water quality, stabilizing the land surface to protect against erosion, and establishing new landforms and vegetation. All of these factors will be addressed while at the same time reducing the requirement for long-term monitoring and maintenance.After a site has been reverted to its rehabilitated state, the miner is responsible for post-rehabilitation monitoring.Site monitoring is to ensure the new surface is stable, the new vegetation is healthy, and that there is no surface and/or groundwater contamination.
The significance of rehabilitation
While rehabilitation process may seem to be irrelevant to the investor, this phase of the life cycle of the mine is far from inconsequential, and can have a huge impact on the future success of a mining company. Rehabilitation is important because a poorly executed rehabilitation program can impact the share value of a public company. Companies that do not follow proper rehabilitation plans could face costly lawsuits. Furthermore, poorly rehabilitated mines leave a negative legacy for their operators. As permission to develop future mines becomes tied to a company's reputation, a company with a history of not following proper rehabilitation procedure may have difficulty obtaining this permission in the future. A poorly planned and executed rehabilitation plan has both negative implications in the future and in the present. Poorly executed rehabilitation can result in skyrocketed costs and eroded profit margins earned through running and operating the mine.
The rehabilitation program: the underground mine
Underground mining results in significantly less surface disturbance than open-pit mining. Even during mining operations the surface of an underground mine may simultaneously be used for other uses such as growing crops, grazing livestock, agriculture etc. Shaping and contouring of spoil piles, replacement of topsoil, seeding with grasses and planting of trees take place on the mined-out areas. Care is taken to relocate streams, wildlife, and other valuable resource. As mining operations are winding down, rehabilitation will be undertaken in tandem with the last phases of mine. When mining is ceases on one section of a surface mine, bulldozers and scrapers reshape the disturbed area. Drainage within and off the site is carefully designed to make the new land surface as stable and resistant to soil erosion as the local environment allows. Based on the soil requirements, the land is suitably fertilized and vegetated. Finally, the underground tunnels are stabilized, and the entrances sealed off.
The open-pit mine
An open-pit mine causes significant surface disruption; therefore, rehabilitation is a much more involved process compared to underground mining. The land's post mining end-use will determine what is done with the open pit. Rehabilitation of the pit may be as simple as fencing it off and allowing it to fill with water. Or it may be filled with rock and soil, and contoured into whatever platform is required for the land's post mining use. Often, material removed in the mining process is used for the backfill. Not all land is returned to resemble a natural state, sometimes mine sites are turned into recreational sites, farms, or garbage dumps.
Regardless of end-use of the land there are a few key procedures undertaken to ensure human/animal health and safety. Waste piles are flattened out and then stabilized to prevent erosion. Ore containing sulfides is covered with a layer of clay to prevent access of rain and oxygen which can turn the sulfides to toxic sulfuric acid. Tailings dams are left to evaporate, then covered with waste rock or clay. The land is covered with topsoil, and then landscaped into the predetermined surface form. Surface infrastructure may or may not be removed during the rehabilitation process. Some buildings will have a new use, and in some cases, old mine buildings remain for their historic and cultural value. Read the entire Life Cycle of a Gold Mine series:Part II: Regional ExplorationPart III: Resource Definition and the Feasibility StudyPart IV: Assessment and ApprovalPart V: Mine Construction Part VI: Operating the Mine