(Solved): 4. A site consists of a homogeneous dense silty sand layer of 10m thickness, which is underlain ...

4. A site consists of a homogeneous dense silty sand layer of $$10\mathrm{m}$$ thickness, which is underlain by an impervious stiff clay. The initial water table was at $$3.0\mathrm{m}$$ depth below the ground surface. A pumping test was carried out by pumping water at a rate of $$0.5{\mathrm{m}}^3/\min$$. Observation wells were dug into the ground at $$20\mathrm{m}$$ and $$30\mathrm{m}$$ distances from the centre of the pumping well. At steady state (when there was no more change in water levels in the observation wells), the water levels in the two wells dropped by $$500\mathrm{mm}$$ and $$150\mathrm{mm}$$, respectively. Determine the hydraulic conductivity of the silty sand layer.