1.1 Background of Study

The sustenance of life depends greatly on water, therefore, the demand for potable water increases continually in line with world population growth. Recently, many African cities have undergone unprecedented growth in population through migration from rural areas which has led to the growth of cities into sprawling “mega-cities” with large areas of unplanned sub-standard housing with few services. The unplanned expansion of such cities leads to a serious pollution threat to the groundwater and uncontrolled industrial and commercial activity add to the pollution threat (UNEP, 2002). This has been a major problem in developing countries; provision of drinking water has become expensive and difficult. The main source of potable water in many of these cities is groundwater, commonly from shallow hand-dug wells and deeper water supply boreholes. In Nigeria, like many other developing countries, open waste dumping system has been the major management option of solid waste disposal. In previous years, management system has been based on collection and dumping out of the city boundaries in conformity with the concept of “out of sight out of mind” (Arukweet al, 2012). But in recent times, the siting and development of residential quarters near waste sites are common due to shortage of building land to cope with the increasing rate of migration and consequent population explosion (Ikemet al., 2002). 

Dumpsites have been identified as one of the major threats to soil and water resources, receiving a mixture of municipal, commercial and mixed industrial wastes. The depressions into which solid wastes are often dumped include valleys and excavations. Studies on the effects of unlined waste dumps on the host soil and underlying shallow aquifers have shown that soil and groundwater system can be polluted due to poorly designed waste disposal facilities (Amadiet al., 2012). Uncontrolled waste dumpsites threaten the groundwater supply as movement of leachates from dumpsites through the soil and the aquifers pose a risk to the environment and human health. Waste placed in dumpsites or open dumps are subjected to groundwater under flow or infiltration from precipitation (Moret al., 2006). The presence and potential exposures of the community to groundwater contaminants may contribute to the predilection of human health impacts, from simple poisoning to cancer, heart diseases and teratogenic abnormalities (Su, 2008). 

Release of pollutants through leachates from both functional and abandoned dumpsites pose a high risk to nearby soil and groundwater if not adequately managed (Ikemet al., 2002). Leachate percolating into the groundwater is a mixture of highly complex contaminants such as potentially toxic metals(lead, mercury, cadmium, chromium etc) ; persistent organic pollutants (POPs) (dioxins, furans, polycyclic aromatic hydrocarbons (PAHs), polybrominateddiphenyl ethers PBDEs); inorganiccompounds (such as ammonium, sulphates, chlorides) and as well as bacterial contamination – total coliform and feacal coliform (Moret al., 2006; Longe and Balogun, 2010; Oyeku and Eludoyin, 2010; Agrawaet al., 2011 and Galarpe and Parilla, 2012). Therefore considering possible impact to surrounding environment brought by dumpsites is inevitable.