The Sierra Leone mining industry is over 90 years old, so there is a historical legacy of environmental deterioration in places. Mining inherently generates large volumes of waste and impacts the natural environment physically, chemically, and biologically. Unprotected mineral residue stockpiles pollute the environment and are potentially hazardous. Water systems are impacted by damming, discharge of pollutants into watercourses, sedimentation, seepage of contaminants into groundwater, and storm runoff from waste rock and tailings piles. There is more qualitative data to support this and some specific studies have quantified environmental change. Satellite imagery, tailings piles, polluted water bodies, flooding, siltation in streams and rivers, potholes, and waterborne diseases such as bilharzia, onchocerciasis, or “river blindness” and schistosomiasis (Worley Parsons Ltd. 2010).

ESHIA are standard requirements for implementing mining projects in Sierra Leone, today. Environmental laws mandate continuous monitoring for environmental and health impacts in populations around mine sites, but this is not routinely done. The early mining industry and colonial government were primarily concerned about how poor environmental management might impact economic efficiency and supply to the mineral commodity chain. The Mines Department underscored that:

Methods of mineral extraction and processing, data from exploratory surveys, geology, geomorphology, weathering, and erosion can indicate areas where potentially hazardous materials may be present in the environment. The reports of the SLGS, mining company ESHIA reports, research studies, and historical narratives on the mining industry are useful sources of information, also. There are naturally occurring contaminants associated with minerals present in the environment that are released and concentrated by extractive methods.