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, AAquifer
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 and 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.