The complexity of geological conditions and the type, length, and width of a structure determine the number of holes required for foundation exploration.

Locate the test holes in an accessible area. When determining the location of test holes, 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 them on the logs and obtain the correct surface elevation.

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

Test hole depth
Lowering of gradeline
Channel relocations and channel widenings
Scour
Foundation loads
Foundation type