Posted by: Deirdre Des Jardins | July 28, 2020

Delta tunnel: DWR rejects consideration of No Tunnel alternatives in EIR

The Delta Conveyance Design and Construction Authority convened the 10th meeting of the Stakeholder Engagement Committee on Wednesday, July 22, 2020. Carrie Buckman, the Environmental Manager for the Department of Water Resources, gave a presentation on DWR’s screening of alternatives suggested in the scoping process.

Buckman summarized the Delta tunnel project objectives as follows:

  • CLIMATE RESILIENCY –Addresses climate change, extreme weather, and rising sea levels in the Delta for the SWP
  • SEISMIC RESILIENCY –Minimizes health/safety risk to public from earthquake-caused reductions in water delivery quality and quantity from the SWP
  • WATER SUPPLY RELIABILITY –Restores and protects ability to deliver SWP water in compliance with regulatory and contractual constraints
  • OPERATIONAL RESILIENCY –Provides SWP operational flexibility to improve aquatic conditions and manage risks of additional future constraints

Buckman described the No Tunnel and Through-Delta alternatives as including some combination of:

  • Increase water recycling and conservation efforts
  • Desalination facilities
  • Continued through-Delta conveyance (use of existing facilities) with improvement to Delta levees

Buckman then showed a slide which stated that the alternatives which continued to use through-Delta conveyance did not meet the project objectives of climate resiliency, seismic resiliency, and water supply reliability.

Through Delta

But the Department of Water Resources has not defined “climate resiliency” or “seismic resiliency,” so this assessment is qualitative.  And the single tunnel project that the Delta Conveyance Design and Construction Authority has been developing for the last year may not perform well with salinity intrusion from high sea level rise at 2100, as we pointed out last year.  There is no report of any analysis of the performance of the DCA’s selected intake locations with high sea level rise.

The single tunnel may also not be designed to withstand a maximum earthquake in the Delta.  DWR rescinded seismic engineering standards for the single tunnel project in June of 2019. The DCA has developed draft Conceptual Seismic Design and Geohazard Evaluation Criteria and submitted them to DWR, but has not disclosed the drafts to the Stakeholder Engagement Committee or the public.

Buckman also stated that DWR has rejected alternative local water supplies as not meeting fundamental objectives of “enabling the SWP to continue to function through challenges such as climate change, sea level rise, and earthquake risk.”

No tunnel

But local water supplies are the only supplies that are truly resilient to long term sea level rise, and may also be the only supplies that would continue to be available after a maximum earthquake in the Delta.

The Governor’s Water Resilience Portfolio should have considered the distinction between local water supply reliability and State Water Project delivery reliability, but the Water Portfolio relied on DWR’s definition of “sustainability” as reliability of Delta exports.

DWR’s exclusion of consideration of local water supplies is also contrary to the 2009 Delta Reform Act, according to scoping comments by the Natural Resources Defense Council et al NRDC et. al. commented that the “stated purpose of increased SWP water diversions from the Delta, without any investment in local and regional water supplies to reduce reliance on the Delta, is inconsistent with state law. The Delta Reform Act established state policy to reduce reliance on the Delta and to meet state water needs through investments in sustainable local and regional water supply projects, such as improved water use efficiency and water recycling. Cal. Water Code § 85022.”

This post was updated on July 28, 2020.



  1. Those are VERY good points: (1) Local water supplies are the only supplies that are truly resilient to long term sea level rise, and may also be the only supplies that would continue to be available after a maximum earthquake in the Delta. Whereas (2) DWR’s definition of “sustainability” is narrowly focused on the reliability of Delta exports.

    In addition, local water supplies are the only supplies that meet the Delta Reform Act/Delta Plan goals of “Reduction of reliance on the Delta through regional self-sufficiency.”

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