It is always interesting to glimpse the Metropolitan Water District’s (MWD’s) internal communications about Delta processes. The MWD general manager’s Bay-Delta Management Report to a board committee this week manages not to mention that the planned “decision tree” for operation of the Bay Delta Conservation Plan (BDCP) includes a possible reduction of exports to 4.5 million acre feet a year. That’s not what exporters wanted from this process. (The “decision tree” is the strategy now on the table for restoring habitat.)
The report also mentions emergency preparedness: “Staff is continuing to coordinate with other agencies and consultants to evaluate the levee improvements along the emergency freshwater pathway.” This is a reminder that the Department of Water Resources and MWD have a plan in place to convey freshwater through channels that may be surrounded by islands flooded with salt water in the event of an earthquake. The pathway generally follows the Delta Cross Channel, Lower Mokelumne River, Middle River and the Victoria Canal.
But in comments on the Draft Delta Risk Management Strategy (DRMS) Phase 2 Report last year, MWD reported that “Under direction of MWD, Washington Group International and later URS has performed levee stability analyses along freshwater emergency pathway reaches of Middle River and Victoria Canal to assess levee slumping under 100-year, 200-year and 500-year probabilistic ground accelerations provided in the DRMS Phase 1 report. Results vary from a few feet of slumping up to ten feet of slumping under existing conditions, in many cases without levee failure” (emphasis added).
So levee failures are not inevitable in the event of an earthquake. That’s what Delta engineers keep saying.
