Performance_Based Design Why Aren's We Leveraging it to its Full Potential?

Risk is inherent to work in the field of subsurface engineering, and many contract approaches have become so focused on shedding risk that they leave no room for one of the best tools in our industry, the observational method. Its development in subsurface engineering owes its foundation to Karl Terzaghi and Ralph Peck through their respective works dating back as early as Soil Mech- anics in Engineering Practice published in 1948 and "Advantages and Limitations of the Observational Method in Applied Soil Mechanics" in 1969. Throughout their fundamental works, a strong argu- ment for the observational method is made: "... the potential for savings of time and money without sacrifice of safety is so great that every engineer who deals with applied soil mechanics needs to be informed." (Peck 1969) Not every project will benefit from its use, but in today's risk management focused world, projects and contracts should be set up to allow for its use, while sharing the risk clearly and equitably between all parties. Without a proper contractual mechanism to leverage its use, perceived manage- ment of "risky unknowns" will over- ride substantive application of the method, and significant benefits may be lost as a result. As Terzaghi said, "A vast amount of labor goes into securing only roughly approx-imate values for the physical constants that appear in equations Therefore, the results of computations are not more than working hypotheses, subject to confirmation or modification during construction." It is our collective view that sub- surface engineers should take this task of confirmation and modification seriously. We should use the observa- tional method to derive performance- based designs that deliver design economy, constructability, cost and schedule advantages without sacrificing safety or quality. Collaborative style contracts provide a framework to approach shared risk and opportunity with appropriate incentives for the individual parties.