Abstract

Boreholes within Lokoja and Patti formation, both unconformably overlying the Basement Complex, generally experience low water yeild and failure. Hydraulic conductivity, porosity and coefficient of uniformity of both Formations were determined using Hazen empirical formula and grain size distribution analysis then correlated to determine reasons for failure and low yields of boreholes in the area. Coefficient of uniformity (U) for Lokoja Formation ranged from 2.2 to 5.2 with a mean value of 3.65 while that of Patti Formation ranged from 2.7 to 4.4 with a mean value of 3.62. Soil porosity (n) for Lokoja Formation ranged from 35% to 42% with a mean value of 38.6% while that of Patti Formation ranged from 37% to 41% and mean value of 38.6%. Effective grain size (D10) ranged from 0.12mm – 0.25mm for Lokoja Formation and 0.14mm - 0.3mm for Patti Formation. Hydraulic conductivity (K) for Lokoja Formation ranged from 1.44 x 10-4m/s to 6.25 x 10-4m/s with a mean value of 3.17 x 10-4 m/s while that of Patti Formation ranged from 2.56 x10-4 m/s to 9 x10-4 m/s with a mean value of 4.63 x 10-4 m/s. Based on the results of the analysis, soils within the study area are well sorted, highly porous and made up of fine sands and fine to medium-grained sandstones. Comparison of hydraulic conductivity of both formations ip ndicated the fine to medium-grained sandstones of Patti Formation have higher hydraulic conductivity compared to those of Lokoja Formation. It also revealed that sandstones within the Patti Formation are highly porous, fairly permeable, and more aquiferous than those of the Lokoja Formation. Sandstone of Patti Formation have higher potential for groundwater exploration and exploitation compared to that of Lokoja Formation.