The Preliminary Design stage initiates the process of converting concepts to a more detailed design whereby more detailed and reliable cost and schedule estimates are developed. This stage of the design is complete when it provides sufficient information to support development of the PB. The appropriate completion percentage is dependent upon the type of project. For basic facilities, such as administrative buildings, general purpose laboratories, and utilities, the design does not have to be as mature as for a complex accelerator facility or scientific instrument. The design is mature when a point estimate can be developed and is ready for an independent review. The determination of a construction project design completion percentage for reporting purposes will be made by the Architect-Engineer as well as by subsystem designers contracted to do the work, and/or other IPT members. 

Final Design is the last stage of development prior to implementation. The purpose of the Final Design stage is to prepare final drawings, technical specifications and contract documents required to obtain bids and quotes for procurement and construction. The Final Design should include clear statements of testing requirements and acceptance criteria for the safety and functionality of all subsystems. The project scope should be finalized and changes (coordinated through a documented and approved change control process and Change Control Board (CCB)) should be permitted only for compelling reasons (i.e., substantial economies achieved through value engineering, accommodation of changed conditions in construction, or reduction in funds or changes in requirements). In any case, construction should not be allowed to proceed until the design is sufficiently mature to minimize change orders. In addition, the preliminary/final design needs to incorporate the Guiding Principles for Federal Leadership in High Performance and Sustainable Buildings per EO 13423, Section 2(f), EO 13514, Section 2. (Refer to DOE G 413.3-6.)

Scientific systems, such as accelerators and detectors, may not follow a linear design process in which all subsystems reach the same maturity at the same time. Concurrency in these types of projects increases the risk because each subsystem design is dependent upon the design maturity of other subsystems. Projects that have several subsystems may have separate preliminary and final design stages. Consequently, final designs may be completed at various points in time in the system development process. Regardless, design reviews should be conducted for all projects and should involve a formalized, structured approach to ensure the reviews are comprehensive, objective, professional and documented.