UFC 3-220-04FA Backfill for Subsurface Structures  

This manual is for the guidance of designers, specification writers, and especially field personnel engaged in designing, planning, and conducting earthwork operations around major deep-seated or subsurface structures. The greatest deficiencies in earthwork operations around deep-seated or subsurface structures occur because of improper backfilling procedures and inadequate construction control during this phase of the work. Therefore, primary emphasis in this manual is on backfilling procedures. Design and planning considerations, evaluation and selection of materials, and other phases of earthwork construction are discussed where pertinent to successful backfill operations. Although the information in this manual is primarily applicable to backfilling around large and important deep-seated or buried structures, it is also applicable in varying degrees to backfilling operations around all structures, including conduits.