Eco-restoration of mine overburden (OB) or abandoned mine sites is a major environmental concern. In the present investigation, an integrated approach was used to rejuvenate a high-sulphur mine OB dumping site in the Tirap Collieries, Assam, India, which is situated in the Indo-Burma mega-biodiversity hotspot. A mine OB is devoid of true soil character with poor macro and micronutrient content and contains elevated concentrations of trace and heavy metals. Planting of herbs, shrubs, cover crops and tree species at close proximity leads to primary and secondary sere state succession within a period of 3 to 5 years. A variety of plant species were screened for potential use in restoration: herbs, including Sccharum spontaneum, Cymbopogon winterianus Jowitt (citronella), and Cymbopogon flexuosus (lemon grass) cover plants, including Mimosa strigillosa, M. striata, and M. pigra; shrubs, including Sesbania rostrata (dhaincha) and Cassia streata (cassia); and tree species, including Gmelina arborea (gomari) and Dalbergia sissoo (sissoo). Amendment with unmined soil and bio-organic matter was required for primary establishment of some plant species. Management of these plant species at the site will ensure long term sustainable eco-restoration of the coal mine-degraded land.

The high-sulfur containing coalmine overburden (OB) dumping ground of the Tirap colliery under the northeastern coalfields in Assam, India, was reclaimed by phytoremediation techniques. Native plant species were planted with line and field methods and by amending with cow dung and unmined soil. In this study, the changes in microbial activity of the reclaimed mine OB wasteland of the Tirap colliery are examined. The enzyme activities of urease, dehydrogenase, and phosphatase were compared over time. Improvements in soil pH, bulk density, and water-holding capacity in the mine OB were found. After four years of reclamation, 1.01% of particles were soil sized (=0.255 mm grain size) with the maximum degradation in the mine OB grain sizes of −20 mm to +12 mm and of +25 mm. A 1,000-fold increase in microbial colony forming units (CFU) in the four years at the remediated site along with an increase in total DNA were evident for the mine OB reclaimed sites. The increase of microbial CFUs in the mine OB was related to a 100-to 2,000-fold increase in enzyme activity for the reclaimed areas. From this investigation, it can be concluded that the improvement of enzyme activities and the increase in microbial populations of reclaimed mine OB will yield information pertaining to the reclamation index of mine OB.