While the total cost of the Alaskan Way Viaduct and Seawall Replacement Program is estimated at $4.24 billion, we estimate the proposed SR 99 bored tunnel itself, including vent buildings and north and south portals, will cost $1.9 billion. The design for the tunnel is currently at about five percent. There are some elements that we cannot completely quantify yet and, therefore, cannot estimate with certainty. To account for this, we use allowances and identify events that, if they occur, would result in costs above (risks) or below (opportunities) what we call the “base cost.” Our current estimate also accounts for seven years of inflation from now until the tunnel is complete in 2015.
| Current bored tunnel cost estimate |
Cost (millions) |
| Construction |
$944 |
| Right of way costs |
$149 |
| Preliminary and final design |
$118 |
| Construction management and administration |
$118 |
| Risk |
$418 |
| Escalation (per Global Insight) |
$166 |
| Total |
$1,913 |
This method of cost estimating is consistent with WSDOT’s
Cost Estimate Validation Process (CEVP®). A key difference between conventional estimating and CEVP® is the combination of a base cost (if all goes as planned) plus a risk cost (if risk events occur) and opportunity costs (if events go better than anticipated). This shows the effect of risks, if they occur, and helps us develop risk management plans to better control costs.
We are in the process of developing a full CEVP® for the bored tunnel cost estimate, including value engineering and risk management, with results scheduled for the end of 2009. This process involves participation by external subject matter experts in order to review and quantify the quantities, unit costs, risks and opportunities associated with the project. Updated cost estimates for construction of the bored tunnel are to be submitted to the Legislature and Governor by Jan. 1, 2010.
Independent cost review
The Washington State Legislature, in its legislation (pdf 17 kb) approving the bored tunnel and associated funding, required an independent review of the project’s cost estimate. WSDOT has asked three qualified cost and risk professionals to conduct this review. These individuals are familiar with large, complex tunnels and underground construction, but have not been associated with the tunnel project and have not participated in the definition of cost or risk for the project. They will review and advise during the CEVP® process and prepare their findings and recommendations by the end of 2009.
The members of the independent cost review panel are:
- Richard Sage, Sound Transit construction manager, is a professional who is familiar with local conditions and costs and has managed the tunnels and complex underground construction for the Link light rail project.
- Donald Hilton, independent consultant, is experienced in heavy civil and tunnel construction with responsibility for cost estimating on many projects.
- Robert Goodfellow, Black & Veatch director of tunneling, is experienced in management and risk management for major tunnel projects and underground structures.
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