An Overview of the Reclamation Process
Since 1975, the State of Florida requires the phosphate industry to return every acre it mines back to productive use through a process called mine reclamation. Mined lands have been successfully reclaimed into valuable wetlands, agricultural land, wildlife habitats, parks and neighborhoods.
Before mining may begin, Mosaic must develop and obtain regulatory approval of comprehensive mining and reclamation plans. These plans outline the mining and reclamation schedules and detail how and when both will be conducted. Once mining commences, state law requires mining parcels to be recontoured and planted with initial vegetation within two years of the completion of mining activities.
Methods for Reclamation
Once mining of an area is complete, the reclamation process begins. There are three primary methods used to reclaim mined land:
Sand tailings fill reclamation
Sand separated from the phosphate ore – referred to as sand tailings – is returned to the mined area and used to fill the mine cuts to a specific elevation. Once pumping is complete, the soil that was moved during the mining process is placed over the sand tailings to match the elevations in the reclamation plan. These areas are then graded to varying elevations and planted with native species to become upland or wetland areas. In many cases, stream systems are constructed to connect reclaimed wetlands to preservation wetland systems.
Land and lakes reclamation
When phosphate is mined, phosphate rock is removed from the site as a matrix of sand, clay and phosphate ore. The sand is sent to areas designated as sand tailings fill areas, and clay is relocated to settling areas, which leaves a void in the landscape. To account for the reduction in materials at the site, lake systems are incorporated into the reclamation plan. During the land and lakes reclamation process, excavation equipment contours the mined land to create a mix of uplands, wetlands and lakes with gentle outer slopes. The shallows of the lake are then planted with herbaceous wetland plant species to enhance water quality and encourage wildlife use. Reclaimed lakes are designed with “pop-off” features allowing water to flow from the lake during significant rain events. These features are specially designed to provide properly timed hydration of connected wetland systems. Upland forested buffers are typically constructed around the lake’s edge to create additional wildlife enhancements. Central Florida’s reclaimed lakes are known for their excellent fish habitats and boast some of the best freshwater fishing environments in the Southeast.
Clay settling area reclamation
The clays that are split apart at the mine’s separation facility are stored in reservoirs known as clay settling areas (CSA), which also are used by a wide variety of wildlife like birds and alligators for food and shelter. Once a CSA has reached its clay storage capacity and is ready for reclamation, specialized equipment is used to facilitate the consolidation and drying of the clay. Channels are cut through the clay to promote dewatering. Once a crust has developed on the surface of the clay, the dam walls are re-graded to create a gentle slope. While active clay settling areas can be quite visible in the landscape, under today’s standards, once they are reclaimed, CSAs typically appear as a subtle hill in the landscape. Reclaimed CSAs are put to productive use as cattle pastures and are suitable for row crop farming. Mosaic maintains ongoing agricultural research on the use of CSAs to grow a number of row crops like cabbage and collards. The clay contained beneath the surface of a reclaimed CSA continues to settle for many years, which limits their potential for development. In addition to agriculture, however, reclaimed CSAs also may provide green space containing lake and wetland systems that provide valuable wildlife habitat.
Reclamation plans consider far more than aesthetics.
One of the most commonly asked questions about mining is how the activity will affect hydrology. Here, the term hydrology is used to refer to how water flows above and below the surface of the land. Florida law requires that the overall hydrology of the reclaimed site closely resemble the surface and groundwater functions of the pre-mined site.
Mining moves large volumes of subsurface materials, with a significant amount of backfill being clean sand washed out of the phosphate ore. Because changes below the surface can affect groundwater hydrology, mining and reclamation plans are developed to address surface and groundwater hydrology at the site from a holistic perspective.
Ground and surface water flows are interconnected and, as such, receive equal consideration. Through decades of data collection and research, the industry has identified mining and reclamation techniques that consider and compensate for alterations in ground water flows after mining. As we design our mining plans, restoring the hydrology helps drive the sequence in which we mine a site as well as the direction of mining. The direction of mining, in relation to groundwater flows can also play an important role in how water will move below the surface once reclamation is put in place.
While the surface and groundwater hydrology may differ at the reclaimed site on an acre-for-acre basis, plans are designed to ensure that, once reclaimed, the hydrologic function of the watershed will be similar to that provided by the site prior to mining. This is achieved through a team of professional scientists and engineers developing reclamation plans using sophisticated modeling.
Clay settling areas, where present, are also taken into consideration. While these have been described by laypersons as a “plug” in the landscape, clay settling areas do not act as a “plug”, but rather—because they continually consolidate and dewater—release water into the surficial aquifer. As a result, in the vicinity of a reclaimed clay settling area, baseflow frequently exhibits a slight increased flow amount in the dry season and a slight decrease in the rainy season.
Advancements in Reclamation
Since reclamation became mandatory in 1975, the body of reclamation science has grown exponentially. Advances in ecology, geology, hydrology and plant sciences all contributed to the phosphate industry’s ability to reclaim complex connected ecosystems and habitats.
In addition to scientific advancements, the industry identified ways to better utilize our existing resources. Modern mine reclamation effectively utilizes resources from pre-mined sites to enhance the quality of our post-mining reclamation projects.
As we prepare to mine wetland systems, reclamation crews often harvest the muck layer from the surface of the wetland. The muck is either stored on site or transported to another reclamation site for immediate use. This muck contains a valuable seed bank. After the reclaimed wetland is properly contoured, the muck is redistributed on the surface. Once distributed, the muck layer will begin to sprout wetland vegetation. The placement of muck also helps expedite the establishment of proper wetland hydrology.
The same practice is instituted for higher quality upland habitats. When practical, crews will harvest the top soil prior to mining. Harvested top soil is transported to another reclamation site for immediate use. Not only does the receiving site benefit from the organic matter found in the top soil, but the soil also contains a valuable seed bank. Once properly distributed, the seeds contained within the soil will begin to sprout and produce a diverse plant population. This diversity can be achieved through direct planting, but due to individual plant characteristics, direct planting often requires a longer establishment period.
In the past decade, reclamation of stream systems became a priority for regulators and the industry. Stream systems Mosaic is permitted to mine are often intermittent and the majority of them were previously impacted by human activity. While a stream may appear simple to anyone who has not studied the science, their function in a watershed is actually quite complex. They drain and deliver water to the wetland habitats they connect. Those wetland systems are highly dependent on how much water they receive and retain. If the streams that connect those systems do not function properly, those habitats will not thrive.
In Mosaic’s reclamation projects, stream systems connect wetlands and lake systems, provide wildlife corridors and aquatic habitat. Just like native wetlands, these reclaimed systems, depending on their type, have different requirements for water timing and quantity. When a stream is reclaimed, it must be designed to deliver and drain the appropriate amounts of water to support the connected wetland systems.
Mosaic employs sophisticated Rosgen stream modeling techniques and/or simulated floodflows, to design reclaimed stream systems. Both methods are based on proven scientific methods to restore proper hydrological function and valuable wildlife habitat.
To create proper wildlife corridors, we have to consider more than just the stream channel. Our reclamation experts create buffers around the stream by planting wetland plant species along the banks to develop wetland floodplain systems that connect to adjacent uplands areas. These buffer areas are vital to developing effective wildlife corridors and a proper canopy over the stream.
What happens after reclamation is completed?
People are often confused by how reclamation is defined as complete. Regulators consider the physical reclamation process complete once the land has been contoured and appropriate vegetation has been planted. However, mining companies are still responsible for maintaining the habitats on the land until they reach maturity and achieve the success criteria set forth by the state and county regulatory agencies.
After the initial reclamation process, sites remain contained within the ditch and berm system of the mine to prevent water from being released into surrounding ecosystems. Once mining companies demonstrate that water quality standards have been met at the site, it is reconnected to and becomes a functional part of the watershed.
Even after reconnection, mining companies must continue maintaining the habitats on the site until they reach maturity. Once the habitats reach maturity, regulators evaluate the property for release. Release means that the mining company has met its obligations for reclamation. Criteria that must be met for a site to be released are stringent and designed to ensure that habitats are well established and will effectively resist invasive species. Minimum establishment periods are required by the Florida Department of Environmental Protection:
- FDEP minimum vegetation establishment periods (post initial planting):
- Uplands: 1 year
- Herbaceous wetlands: 3 years
- Forested wetlands: 5 years
Some plant species, such as bay trees or palmettos, have much longer establishment periods than the minimum establishment periods. Those specific species have individual criteria in the requirements, which, in most cases, extends the establishment period significantly beyond the minimum. While those parcels take longer to release, they are typically reconnected to the watershed years before release and provide similar function to fully mature systems.
Mosaic Reclamation PhotoBook
Re-establishing, Reconnecting, Restoring. Advancing the science and practice of mined-land reclamation.