Cost Estimating for Underground Transit: Too Dangerous to “Guesstimate”
Abstract
Traditional construction cost estimating methods that rely on historical cost data are not well suited for underground transit feasibility studies, because not only do construction costs vary widely because of subsurface, geographic, and other project-specific parameters, but also because such construction costs are not generally available in cost databases. Furthermore, the inherently expensive and unknown nature of underground construction often leads to inaccurate cost estimates, which in turn can lead to a significant budget shortfall as the project moves from planning and design to construction. What does this mean for the planner producing an EIS/EIR or the engineer involved in conceptual design? It means that tunnels and other associated underground work cannot be estimated on a “per foot basis” as is customarily done during the early stages of an above-ground transportation project. Labor factors and geologic conditions will often dictate tunnel construction costs; tunnels in Boston have different labor factors than tunnels in Los Angeles, and tunnels in downtown San Francisco through soft-ground will have very different costs than tunnels through weak rock on the west side of San Francisco. This paper summarizes the unique aspects of underground construction relating to cost and concludes that while production-type estimates are crucial for developing realistic project budgets, such estimates do not require a high degree of project definition.
2002
The Capital Projects Process
Victor S. Romero
Jacobs Associates
John M. Stolz
Jacobs Associates
