The complexity and variability of geological conditions and the type, length, and width of a structure determine the number of borings required for foundation exploration. Except as noted here, follow AASHTO LRFD Bridge Design Specifications Article 10.4.2 as a starting point to determine the locations and depths of borings.

When developing boring location plan, consider structure type, estimated loading, and foundation geometry. Locate the borings in a feasible and accessible area. When determining the location of borings, always avoid overhead power lines and underground utilities. If possible, avoid steep slopes and standing or flowing water. Deviations within a 20-ft. radius of the staked location are not usually excessive but note these deviations on the logs and obtain the correct surface elevation.

When determining the location and depth of borings, carefully consider the following factors: