Engineering and Construction

a. Fills include conventional compacted fills; hydraulic fills; and uncontrolled fills of soils or industrial and domestic wastes, such as ashes, slag, chemical wastes, building rubble, and refuse.  Properly placed compacted fill will be more rigid and uniform and have greater strength than most natural soils.  Hydraulic fills
may be compacted or uncompacted and are an economical means of providing fill over large areas.

Except when cohesionless materials, i.e., clean sands and gravels, are placed under controlled conditions so
silty pockets are avoided and are compacted as they are placed, hydraulic fills will generally require some type of stabilization to ensure adequate foundations.

b. Uncontrolled fills are likely to provide a variable bearing capacity and result in a nonuniform
settlement.  They may contain injurious chemicals and, in some instances,  may be chemically active and
generate gases that must be conducted away from the structure.  Foundations on fills of the second and third groups (and the first group if not adequately compacted) should be subjected to detailed investigations to determine their suitability for supporting a structure, or else they should be avoided.  Unsuitable fills often can be adequately stabilized.