An engineer has designed the foundation for column system (16 columns) of a 4 story residential building. preliminary excavation showed level of water below 3.5 m from ground level. the column loads were equal in all columns. each column carried 2500 kn of axial load. the design engineer came up with the foundation size of 3.0 m 2.0 m for all columns. the assumed depth of footing was 1.5 m below the ground. calculate the appropriate boring depth from ground level for detail site investigation. use asce procedure for your calculation.