WaterFix Hearing: Tunnels not being designed to withstand maximum earthquake in the Delta

Since this blog post was published on March 20, 2018, the Department of Water Resources and Metropolitan Water District committed to designing the Delta tunnel(s) to withstand a maximum earthquake in the Delta.  However, the new analysis that the Delta tunnel lining will withstand a maximum earthquake assumes that the Delta soils are very dense and that ground motions attenuate by 66% with depth.  The validity of the new seismic analysis is addressed in a July 8, 2019 blog post.

Sacramento — Part 2 of the State Water Resources Control Board’s Hearing on the WaterFix Water Right Change Petition (aka Delta tunnels) has been ongoing since February 22, 2018.  On March 14,15, and 16, 2018, the County of San Joaquin, the San Joaquin County Flood Control and Water Conservation District, Local Agencies of the North Delta, and the South and Central Delta Water Agencies presented testimony by a geotechnical engineer and the principal engineer for many of the Reclamation Districts in the Delta. The engineers testified on the inadequacy of the preliminary engineering for the Delta tunnels, and the resulting risks to the project, and to people and property in the Delta.

The engineers’ testimony showed that MWD and DWR have been dissembling about the Delta tunnels being a “fix” for a maximum earthquake in the Delta, as analyzed in the 2008 Delta Risk Management Strategy report. The Delta tunnels are not currently being designed to withstand a maximum earthquake in the Delta, as defined by the American Society of Civil Engineers and required by the California Building Code for above ground buildings and structures.  The expert testimony also raised very real concerns that inadequate structural design of the Delta tunnel lining could not only result in the Delta tunnel lining leaking in an earthquake, but actually increase the risks of the levees failing, if the problems with the current Conceptual Design of the Delta tunnels are not addressed.

1Effects of Maximum Considered Earthquake on blind fault in the Delta, according to Delta Risk Management Strategy

Fail to plan, plan to fail

Josef Tootle is the Principal Geotechnical Engineer with ENGEO Incorporated, and has 20 years of experience with projects in the Delta.  Tootle testified that the geotechnical borings done to date for the Delta tunnels are completely inadequate, even for the preliminary engineering. Tootle also testified that failing to have adequate geotechnical exploration could lead to delays in the project, needing to relocate the tunnel alignment, or, if the errors weren’t dealt with in the preliminary design, potential injury to life or property in the Delta if the tunnel lining failed due to seismic or structural stresses.

Josef Tootle’s concern about the impacts of the tunnel lining leaking under critical structures was corroborated by testimony of Chris Neudeck, principal at Kjelsen, Sinnock and Nuedeck. Neudeck is the the District engineer and Local Agency Representative for 26 of the Reclamation Districts in the Delta. Neudeck expressed concern not only for the impacts of tunnel lining leakage on the Delta levees, but also about risks of tunnel boring under the levees. Neudeck testified that the tunneling under the levees would need to be done very carefully and monitored very closely. But MWD and DWR have not set any standards for tunnel boring, deferring determination of allowable settlement and monitoring procedures to future engineering. Neudeck testified that DWR has never discussed risk management while tunneling under the levees with the Reclamation Districts.

Tom Williams, a PhD geologist who has consulted on tunnel and pipeline projects all over the world, raised similar concerns about the feasibility of the Delta tunnel conceptual design, and the risk to levees from the tunnel construction and operation in testimony in Part 1 of the WaterFix hearing.

Why DWR’s proposed mitigation may be meaningless

The “Avoidance and Mitigation Measures” in the WaterFix Final EIS/EIS state that DWR has committed to designing the Delta tunnels according to applicable codes and standards.   Chapter 9 of the WaterFix Final EIR/EIS, on Geology and Seismicity states: Regulatory Design Codes and Standards for Project Structures

State and federal design codes and standards will regulate construction of the many structures that are part of the proposed project. These codes and standards establish minimum design and construction requirements, including design and construction of concrete and steel structures, levees, tunnels, pipelines, canals, buildings, bridges and pumping stations. (p. 31.)

But cross-examination in the WaterFix Hearing showed that above ground building codes don’t necessarily apply to deep underground structures, and DWR’s own adopted standards include no objective criteria. Josef Tootle affirmed the following on cross-examination by California Water Research:

  1. Above ground buildings and structures in California are designed to withstand a “Maximum Considered Earthquake,” without collapsing.   A Maximum Considered Earthquake is defined by the American Society of Civil Engineers (ASCE) as an earthquake with a probability of 2% in 50 years, or 1 in 2,475 years.
  2. The ASCE standards may not apply to the tunnels.  (DWR’s attorneys previously claimed they do not.)
  3. DWR’s 2015 WaterFix Final Draft Conceptual Engineering Report shows the Delta tunnels are being designed to withstand a 5% in 50 year earthquake (1 in 1,000 years), which has weaker ground shaking than the Maximum Considered Earthquake.
  4. DWR’s 2010 internal, unreleased preliminary engineering report showed that the tunnel lining joints could “de-stress” in a 5% in 50 year earthquake, causing a temporary increase in leakage.

California Water Research asked Mr. Tootle if he was the Geotechnical engineer on a tunnel project, and the preliminary seismic structural analysis showed that tunnel joints could “de-stress” and leak in an earthquake, would he want to see further analysis?   He said yes. (The Delta tunnel Final Draft Conceptual Engineering Report does not disclose any seismic structural analysis, but states that MWD’s and DWR’s engineers are now assuming that seismic forces would fall off by 50% with depth. The assumption was contradicted by seismic data.)

DWR is promising to address the seismic issues with the Delta tunnels in future preliminary design, but is not proposing to release the future preliminary design documents for review by stakeholders. Instead, DWR is proposing to rely on “applicable codes and standards” to ensure that the tunnel lining has an adequate design.

But the standards listed in section include DWR’s Seismic Loading Criteria Report, issued by DWR in 2012.   The standards in DWR’s 2012 Seismic Loading Criteria report are no standards at all.  This is what the Seismic Loading Report has to say about pipelines and tunnels:

Section 3.2.2 Pipelines

Similar to SWP canals, little documentation exists regarding the seismic loading criteria used in the design of existing pipelines including the recently designed pipelines. DWR does not currently use any analytical model to predict the behavior of buried pipelines during earthquake occurrences. This is partly because earthquake loads may not be a concern for pipelines below the ground surface. Furthermore, AWWA manuals do not explicitly include seismic loading criteria for water pipelines. (p. 16.)

[note – Water supply pipelines DO fail in earthquakes.]

Section 3.2.3 Tunnels

The seismic loading criteria that were used in the design of existing SWP tunnels also have not been found. Many references, including the “Seismic Design of Tunnels – A Simple State-of-the-Art Design Approach” monograph (Jaw-Nan Wang and Parson Brinckerhoff, 1993) discuss the seismic loading criteria that could be used for tunnels. (p. 18)

Josef Tootle confirmed that these sections of the SLC report indicate that DWR could not locate seismic design criteria for any of the existing SWP pipelines or tunnels, and that the sections did not appear to set any criteria for the design of pipelines or tunnels. California Water research also cross-examined Josef Tootle about the foreward to DWR’s Seismic Loading Criteria report.  It states:

These guidelines are a suggested starting point, but do not take the place of the design engineer’s judgment and additional information available for a particular project site. Each design engineer should have the knowledge, experience, and insight into the importance of their facility to select the appropriate seismic design load and subsequently to apply that load in an appropriate manner to the structure. Similarly, this report does not prescribe the procedure or process of analyzing the structure. Again, this is design engineer’s responsibility to select the method of analyses that best suit the complexity, criticality, and importance of the facility. (p. 3)

Josef Tootle thought that the Seismic Loading Criteria report should set minimum standards, which it does not.   It is unclear what DWR’s commitment to build the Delta tunnels to “applicable codes and standards” actually means.  Given the failure by DWR set any clear, objective engineering criteria for the Delta tunnels, there a very real risk that cost-cutting by the water contractors who are paying for the project could compromise both long-term performance and public safety.


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