The design-build project delivery method presents unique challenges to the preparation of an engineer’s estimate and schedule, which are not encountered with traditional design-bid-build projects. This paper will present an overview of how a true bottom-up cost estimate with an integral schedule was developed as a tool to overcome the many estimating and scheduling obstacles presented by the District of Columbia Water and Sewer Authority’s (DC Water) Blue Plains Tunnel Project. The project consists of five shafts and approximately 7,300 m (24,000 ft) of tunnel. This bottom-up estimating method has served to validate the existing budget and schedule, and because of its adaptability to the changing scope and design refinements, it has acted as an aid in setting realistic milestone dates, updating budget needs, and performing risk and sensitivity analyses.
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