Posted by: Deirdre Des Jardins | February 4, 2019

WaterFix project could have major changes, cost escalations with more geotechnical evaluation

Fugro announced on January 23, 2019 that they will be leading a consortium of 5 consultants and 35 specialty subcontractors to provide geotechnical investigations for the WaterFix project. The services will include geological assessment, geophysics, drilling, sampling and laboratory testing. The contract is valued at $75 million.

Dr. Clyde Thomas Williams is a PhD geologist with 30 years of experience with underground projects, including tunnel and pipeline projects around the world, who testified in the State Water Resources Control Board’s hearing on the WaterFix Change Petition.   Dr. Williams testified that a full geotechnical evaluation for the project could result in significant changes to the tunnel and shaft designs and likely significant increases in cost and time. Dr. Williams’ testimony stated in part,

Because the required geotechnical evaluation has not been done, I consider it likely that many aspects of the Project will change. Masoud Manzari did a study of managing geotechnical risks of tunnel projects in soft ground. Manzari’s presentation on the study was titled, Soft Ground Site Investigation & Managing Geotechnical Risks In Tunnelling. The presentation includes the graph on the following page, showing the number of change orders to the projects he studied as a function of the number of boreholes per linear feet of tunnel route. The number of change orders goes up almost exponentially as the number of boreholes decreases. The boreholes for the WaterFix project are on the extreme lower end of the X axis on Manzari’s graph.

In addition, while the leakage analysis done to validate the tunnel lining design (Exhibit DWR-659) looks competent, the analysis methodology is based on a 1994 paper by Fernandez, who derives his estimates from assumptions for rock tunnels. The assumptions almost certainly don’t apply to tunnel linings in soft alluvial deposits beneath the Delta and especially for the connecting tunnel/shaft portions. I would therefore expect that there will need to be significant changes to the tunnel design to ensure that the proposed segmented tunnel lining will not develop leaks under long-term operation. Due to cost escalation issues, an adequate design could require significant changes in the currently proposed tunnel alignment to move the segmented lining to better soils.

Based on my 30 years of experience with underground projects, I think it likely that there will be significant changes to the tunnel and shaft designs and likely significant increases in cost and time. I do not consider a project that is subject to a cost escalation of more than 30% to have a final/biddable/construction design, or even preliminary designs.


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