Environmental Engineering Aspects of Abandoned Mine Site Rehabilitation in Plateau State

This study examines the environmental engineering aspects of rehabilitating abandoned tin and columbite mine sites on the Jos Plateau in Plateau State, North Central Nigeria. The Jos Plateau hosts hundreds of abandoned mine workings from the colonial and early postcolonial mining era, many of which present ongoing environmental hazards including pit water with acid mine drainage characteristics, tailings containing elevated heavy metals, collapse hazards, and loss of agricultural land. The study combines environmental baseline characterisation of three representative abandoned mine sites with an engineering feasibility assessment of rehabilitation options. Site characterisation includes geotechnical survey of pit stability, water quality analysis of pit water and downstream seepage for pH, acidity, iron, manganese, lead, and arsenic, soil contamination assessment around tailings piles, and vegetation recovery survey. Engineering rehabilitation options assessed for each site include pit backfilling with overburden, water management by drainage and passive acid mine drainage treatment, tailings stabilisation and capping, and revegetation using locally adapted species. Capital and operating cost estimates are developed for each option. Results show that pit water at two sites exhibits severe acid mine drainage with pH below 3 and elevated iron concentrations requiring long-term passive treatment. Tailings contain lead at concentrations above agricultural soil screening values at all three sites. Passive treatment using a constructed alkalinity-generating system is technically feasible and cost-effective. The study recommends a Plateau State abandoned mine rehabilitation programme funded through the Solid Minerals Development Fund. Keywords: abandoned mines, mine rehabilitation, acid mine drainage, tailings, Plateau State.