Using a collaborative approach between Alpha’s environmental managers and an agronomic team from Pennington Steel, a more efficient reclamation model emerged. Mine site operators began to coordinate soil tests and analyses with Pennington prior to seeding to allow for site-specific reclamation plans that addressed soil fertility, pH, erodibility factors, seed selection, and erosion control-measures. This increased the establishment success rate of permanent vegetation that complemented post-reclamation land uses.
Soil Testing Establishes Solid Foundation for Growth
Soil testing prior to seeding is critical on mine sites to help insure the establishment of permanent vegetation. Depending on the geological profile from which material is mined, the surface soils can vary greatly in composition. Soil organic matter, nutrient availability and pH can range widely, even within a close proximity on the surface. Acidic conditions can also arise in post-mining operations due to the presence of certain elements and Acid Mine Drainage.
The majority of the sites tested had extremely low levels of organic matter (0.2%-1.4%), since the seed bed was largely comprised of crushed bedrock and shale. Desiring a minimum of 4% organic matter to sustain long-term vegetation success, mycorrhiza soil fungi, beneficial bacteria and multiple bio-stimulants—the building blocks to healthy soil—were applied to the prepared slopes at the time of seeding to address organic matter deficiencies.
Most soil analyses indicated acidic pH levels with differing inherent nutrient values. Large amounts of lime were required to raise the pH to an ideal range between 6.0-6.5, where soil nutrients become plant available. Customized fertility plans also increased reclamation efficiency by eliminating excess fertilizer and the potential for water quality impairment compared to standardized applications.
Selecting the Right Seed & Seeding Method
Much of the seed that Alpha’s legacy sites in West Virginia and Kentucky had previously used was not properly labeled and yielded inconsistent results. Third-party seed laboratory tests determined that temporary, annual grasses, such as wheat and rye, dominated the mixes; while permanent perennial legumes, such as birdsfoot trefoil or yellow blossom clover, were lacking under permit requirements. Vegetation establishment efforts were greatly enhanced by selecting properly labeled seed mixes with guaranteed analysis that complemented permit species requirements.
Due to the steep terrain of the basin and large tracks of land needed to be reclaimed, hydraulic seeding or hydro-seeding was the preferred seeding method. Hydroseeding offered a distinct advantage over other seeding methods in that the ingredients in the tank mix recipe could be easily adjusted based on soil test results and site requirements. This allowed for the implementation of site-specific revegetation plans that could accurately and efficiently address all major obstacles to vegetation establishment at the time of seeding.
Expanding the Model
Overburden materials (bi-products of coal processing) are often used to reclaim highwalls and valley-fill impoundments. These sites are a particular challenge to vegetate. The common practice for reclaiming these areas is to apply a minimum soil layer of 18-24 inches as a “cap” on top of the overburden material prior to seeding. Alpha was impressed with Pennington’s previous success record for establishing vegetation directly on fly ash, and as a result, opted to direct seed the overburden areas. By eliminating the need for a soil layer on top of the overburden material, the potential saving in time and money were enormous.
When analyzed, the overburden material and fly ash were quite similar. They both exhibited low pH and percent organic matter, along with a dark surface color that readily absorbed thermal radiation, making the surface at least 20˚F hotter than surrounding soils in the summer. To sustain vegetation, the acidic pH levels were raised with pulverized limestone and fast-acting dry lime. Nutrient deficiencies were resolved with the re-introduction of highly concentrated bio-stimulates, beneficial soil microbes and fertilizer.
When this approach was implemented at Alpha’s Grey Eagle processing site in Mingo County (W.Va.), the project team selected a cool-season Slopemaster seed mixture specifically designed for stressed environments and a Mohawk cold-tolerant bermudagrass. The seed mixture was treated with GermMax germination aid to increase seedling vigor during germination and establishment, as well as MYCO Advantage mycorrhiza inoculants to increase nutrient and water absorption and help mitigate drought and salt stress. Starting in March 2011, the seed was hydraulically applied along with soil amendments and 3,000 lb/acre of a high-performance, fiber-reinforced matrix that effectively stabilized the site from erosion, while also acting as a sunscreen over the dark material to reduce temperatures and evaporation rates.
By the one-year mark, the site had been converted from a 40 acre impoundment of exposed refuse and minimal vegetation to a lush and heavily vegetated site. The dense, permanent vegetation establishment across the site greatly exceeded Alpha’s expectations, with the site operator commenting that “the impoundment area looked as lush as a state park.”
The collaborative effort addressed the traditional challenges of vegetation establishment on rehabilitated surface mines, as well as value-enhanced seeding applications on coal refuse and overburden areas. The site-specific reclamation model provided improved BMPs for soil stabilization and erosion control, while dramatically improving permanent vegetation establishment. Starting with a soil test, corrective actions were taken to mitigate soil conditions at the time of seeding to create the right foundation for long-term, sustainable growth.
By using a comprehensive approach that encompassed soil science, agronomy and improved soil stabilization techniques, Alpha substantially increased vegetation establishment success rates from initial seeding applications. Alpha continues to use Pennington in the evaluation of their reclamation best management practices.
Free is a business development manager for Madison, Ga.-based Pennington Seed, Inc.