3.2.1.2. Boring depth should be controlled by the characteristics andsequence of thesubsurface materials encountered.
Unsuitable foundation strata
Extend all borings through unsuitable foundation strata to reach hard or compact materials of suitable bearing capacity.
Compact soil
Where stiff or compact soils are encountered at shallow depths, extend borings through this material to a depth where the presence of an underlying weaker stratum cannot affect stability or settlement.
Bed rock
Where bedrock surface is encountered, extend one or twoborings 2.0 meter into sound rock.