Abstract

Enugu metropolis is within the Anambra basin, which comprises mainly sedimentary rocks of sandstone, siltstone, mudstone and shales in the Lower Benue trough and as the capital of Enugu state in Nigeria and also as one of the major municipal and industrial centers in southeastern Nigeria experiences much groundwater contamination due to coal mining activity. The Area is richly endowed with sub-bituminous three-coal seams within the Mamu Formation. It also lacks prolific and  potable  groundwater  due  to  the  thinning-out of the Ajali  sandstone  aquifer  through  Udi  town  and  Ninth-mile  into  Enugu  metropolis. Generally, the specific discharge of Ajali sandstone (17.5 m²/day) is higher than that of Mamu Formation (14.5 m²/day). This appraisal  becomes  necessary  to  acquaint the  Enugu  city  developers  on  the  need for the prediction and understanding  of  the  Environmental Impact Assessment (EIA) on the future development, management and maintenance of the mine water. The study also aims at identifying various contaminants, sources, level of concentrations, effects and control measures. Many springs, streams and seepages exist on the foot of most of the hills and ridges. The springs form the headwaters of the major streams and rivers like Ekulu, Iva and Nyaba at the base of the escarpment. Out of the streams and rivers in Enugu coal city, Ekulu River is the largest and thus very important for industrial and agricultural purposes. However, the coal mines discharge their effluents and waste waters directly into the Ekulu River with toxic heavy metals like As, Cd, Cr, Fe, Mn, Ni and Pb that contaminate the water and sediments. At the mines, most of the seepages, springs and streams rise directly from the perennial flood water from the mines. The water from the coal mines with special treatment for pH and iron contents can be employed in augmenting the present inadequate water supply that comes from the Ninth Mile borehole network and Ekulu River reservoir. The pH can be treated with hydrated lime, while iron (Fe²⁺) can be treated with aeration and filtration.

Key words: Groundwater, coal mine, Ajali sandstone, sub-bituminous, coal, rivers, seepage.