Differing Site Conditions—Engineering and Legal Perspectives

Site characterization data is provided to a contractor or designer for the bidding and potential implementation of a contract. The data is developed through various techniques and is meant to assess the stratigraphy, composition, and properties of subsurface materials which are inherently variable. From a geotechnical engineer’s perspective there is uncertainty in the subsurface. If a contractor encounters subsurface materials which are different or not identified in the site characterization data, a differing site condition clam is filed. From a contractor’s perspective there is risk in constructing in the subsurface. Although uncertainty and risk are related, the processes of site characterization and subsurface design and construction must not be entangled. Contractors and designers utilize uncertain subsurface data developed through geotechnical site characterization processes to design construction sequences and structural components in the subsurface. Risk can only be realized through design and construction. Suggestions for updating the site characterization process to reduce uncertainty and thus minimize risk are discussed.