Delta tunnel: Independent Technical Review Panel finds main tunnel route “impractical”

The Department of Water Resources’ Notice of Preparation for the Delta Conveyance Project shows two potential alignments for the main tunnel.   The “Central Corridor” is the route of the former WaterFix / twin tunnels project.  The “Eastern Corridor” is closer to I-5.

Single tunnel NOP map

The Department of Water Resources did not disclose that an Independent Technical Review Panel, consisting of engineers from major tunneling contractors, found that the Central Corridor route (the WaterFix project route) is impractical due to access problems.  The January 31, 2020 report of the Independent Technical Review Panel was disclosed in the February 20 meeting packet for the Delta Conveyance Design and Construction Authority Board.  The report stated:

The consensus among the ITR was that the Central Corridor is logistically impractical and the ITR does not recommend this corridor be further studied. The shaft locations are located a significant distance from Interstate 5, accessible by only farm roads with hindrances such as narrow weight-restricted bridges and single lanes. This makes supporting large operations, which requires a constant transfer of materials and people in and out, impractical and expensive as well as difficult to price. In addition, addressing safety, including hospital access and tunnel safety duplication, creates a costly layer or redundancy without definitive costs.

The Independent Technical Review Panel instead recommended that a “far eastern” route be studied.   The ITR recommended that one of the shafts be shifted closer to industrialized Stockton, stating, “[t]his site allows for segment production if desired and barge facilities to be developed. It is also adjacent to rail.”

Far Eastern tunnel route

The Department of Water Resources did not include the proposed Far East Alignment Corridor in the Notice of Preparation.

Ironically, in February 2010, the Independent Technical Review Panel for the twin tunnels project made the same recommendation, namely “a realignment of the tunnel conveyance to the east would yield better conditions both for constructing tunnel shafts (portals) and for boring the tunnels.”  But DWR’s Engineers rejected the Eastern Route, stating:

Relocating the tunnel to the eastern side of the Delta would put it outside the Conveyance Planning Area and would in all probability cause a delay in the environmental process.  An eastern alignment for the tunnel would also be much longer and would cost between $1 billion and $1.5 billion more than the current alignment.

Ironically, the 2020 Independent Technical Review Panel for the single tunnel found that the Central Corridor route would likely cost more than the Eastern Route, stating:

While it was recognized that extensive roadway, levee, and likely barge improvements could be constructed as part of the project for the Central Corridor, the ITR offered:

    • The cost of improvements to provide reliable and safe access and egress at each site would exceed the cost of additional length of tunnel required for the East alignment. […]
    • Labor and construction safety costs, regardless of improvements, are too uncertain to price due to the location and distance from any shaft on the Central Alignment to developed land/communities.

DWR’s deferral of consideration of mitigation for transportation impacts and safety costs in the twin tunnels environmental documents delayed accurate comparison of the costs and difficulties of the central and eastern tunnel routes for a decade.

One thought on “Delta tunnel: Independent Technical Review Panel finds main tunnel route “impractical”

  1. I remember, after February 17, 2017’s emergency epilepsy failure, the CAR committing to openness and transparency, or were the just kidding?

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