Vulnerability assessment of groundwater pollution in the vicinity of an active dumpsite (Olusosun), Lagos, Nigeria

The deleterious impacts of dumpsite activities and the associated risk on both the environment and human is consequential, hence this study assessed groundwater vulnerability to pollution from dumpsite using a modified DRASTIC model. Six hydrogeological factors: D- Depth to water, R- Net Recharge, A- Aquifer media, L- Distance of well to dumpsite, T- Topography, and C- Clay content were used in the modification (DRALTC) based on peculiarity of the study area. Cluster analysis of groundwater data and Water Quality Index (WQI) were also evaluated. The groundwater vulnerability index was characterized by two zones; forty five percent (45%) moderate and fifty five percent (55%) high zones. The dendogram showed three clusters of chemical dissimilarities. The WQI showed values between 61.8 and 205, indicating good–poor–very poor class of water. The analysis of the groundwater samples showed nitrate concentration ranging from 7.60 to 35.6 mg/L and from 8.56 to 32.4 mg/L in dry and rainy seasons, respectively. The DRALTC model was validated using nitrate concentration. Though, there appeared relative groundwater protection from contamination, there is still need for measures to mitigate further contamination and associated risk in the moderate vulnerability zones. DRALTC model is proved a good tool in groundwater management.