Owners typically retain a geotechnical consultant, either directly, or indirectly through the designer. Either way, the number of borings the geotechnical consultant will take is often dependent on the funding available. It should be noted that the fewer the number of soil borings taken, the less likely that those taken will indicate properly the site conditions.
Deficient Site Investigation.
One common example of deficient site investigation is the failure to discover a conflicting underground utility in planning the location of new utilities. In some instances, the designer has not been given accurate utility locations by the owner. When utility conflicts are discovered during construction, they result in extra costs—either for redesigning the proposed utility or relocating the existing utility—depending on which option seems more feasible at the time of discovery.
Another example of deficient site investigation is the excessive moisture content of the excavated soil. Soil that contains excessive moisture will require additional compaction effort and drying time. Those efforts and the time associated with them are usually not considered in the contract time limits. Absent an extensive subsurface investigation, such soil conditions may not be known until the contractor starts its excavation work. A designer could have forewarned the contractor about the problems or could have incorporated lime or some other soil treatment in the design to facilitate the drying process.
In some roadway rehabilitation projects, the designer bases his or her design on original as-built drawings. Several renovations and piecemeal changes may have occurred since the completion of the previous project, and the as-built drawings may not reflect those changes. Lacking the funds to verify the accuracy of the as-built drawings, the designer designs the project from out-of-date drawings only to discover the deviations when construction begins.
An inadequate subsurface investigation may fail to identify hazardous materials which require special handling for removal and disposal. A contractor may discover materials unknown to it at the designated excavation area and determine they are hazardous. Because it had no prior knowledge of the presence of contaminated material, it will not have contemplated acquiring a special permit for its disposal, or the special handling necessary. Consequently, the contractor’s work may be delayed while it obtains approval of a disposal site and the disposal method.