Extra Credit $(15$ points$)$

For the subsurface conditions shown below, the sand and gravel layer is a pressurized aquifer

and the water level in a piezometer rises $10$ feet above the ground surface as shown. The upper

unconfined aquifer is located in the coarse sand layer. Calculate the effective vertical stress at

Point A located in the Lean Clay layer.

Assume that the Coarse Sand and Sand and Gravel layers are highly permeable compared to the

Lean Clay and Silty Clay layers.