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Delta Flows: December 3, 2013

“All fantasy should have a solid base in reality.”

– Max Beerbohm

The Pole Barn and other earthquake fantasies

Those of you who listened to the entire November 18 presentation to the Redding City Council by Dr. Jerry Meral will have heard about the Pole Barn with the Floating Poles. Aha! you may have said to yourself. Proof of liquefaction after all!

Dr. Meral said . . . The truth is . . .
There are thousands of miles of levees protecting Delta islands. According to the Delta Protection Commission’s Economic Sustainability Plan, there are fewer than a thousand miles of Delta levees currently being maintained.
“Unfortunately, those levees are built on a very poor foundation.,They are built on,peat soils, and they were built mostly with clamshell dredges many years ago and in a casual way by the farmers who originally reclaimed the islands, although we’re trying to improve them.” Says Dr. Pyke, “Since 1982, the State of California has contributed significant funding to make significant improvements in the Delta levee system with the goal of achieving the Delta-specific PL 84-99 standard agreed to in 1982 by the State and federal governments. . . . The bulk of the levee system has been rebuilt in the last 30 years in accordance with modern engineering practices.”
“Some of you may remember in 1972 when Andrus-Brannan Island failed, it was in the middle of summer . . . . [The] ocean came in to fill this space and the Delta became salty, and it was very difficult to pump water to the 20 million people who rely on it from the southern Delta.” In 1972, the population of the State was just over 20 million, so even if two-thirds of Californians relied on water from the Delta (a figure often quoted), that would have been a bit over 13 million people. In fact, though, assertions about the number of Californians who get their water from the Delta greatly exaggerate the level of reliance on it. It may be the case that close to 25 million Californians get some portions of their water from the Delta, the vast majority of urban water districts have alternative sources of supply – certainly enough to get them through the short interruption in exports that would occur if a single island flooded.,In the Andrus-Brannan Island case, the breach was closed in a month, and salinity conditions in the Delta were back to pre-break levels in about 6 weeks.
“The USGS has said that there is a 60% chance of a major earthquake in the East Bay over the next 40 years…” What the USGS said is that there is a 63% chance of an earthquake of magnitude 6.7 or greater in the San Francisco Bay region in the next 30 years.,Dr. Pyke notes that only about a third of that hazard involves earthquakes generated in the East Bay on the Hayward fault.,”The other two-thirds of the hazard comes from faults on the Peninsula or in the North Bay.,Even the Hayward fault is 30 miles from the western edge of the Delta, and much further from most of the Delta.”
” . . . and if that happens, many people predict that there will be as many as 20 islands fail at once.,You’ve got to keep in mind that these island levees are based on very poor soils and we get liquefaction, just the same way they did in the Sunset District in the Loma Prieta earthquake . . .” Says Dr. Pyke: “The major example of liquefaction in the Loma Prieta earthquake was in the Marina, not the Sunset District. The Marina District is very susceptible to liquefaction because the outer portion of the district is built on recent hydraulically filled sands. To understand the susceptibility of soils in the Delta to liquefaction you have to read Appendix E of the Economic Sustainability Plan, but basically the likelihood of liquefaction is low and it is confined mostly to project levees that may have been constructed on recent alluvial foundations. The popular belief that peats perform badly in earthquakes is incorrect, as also discussed in Appendix E of theEconomic Sustainability Plan. This is confirmed by the testing of an embankment on Sherman Island by professors from UCLA, which was intended to replicate a nearby magnitude 7 earthquake, and did not result in a failure of the peat foundation.”
“. . . or other places, such as in Kobe, Japan.” “Even if levees suffer some distress during an earthquake they will not necessarily breach. For instance, the levees in Kobe, Japan that Dr. Meral refers to, actually continued to hold water even though they were quite badly damaged. With proper emergency preparedness and response, any levees in the Delta that suffer distortion in an earthquake could be repaired before the next incidence of high water. That is part of the reason the probability of actually seeing multiple flooded islands is so low.”
“The last earthquake we had of large size was the Loma Prieta earthquake, but the shaking in the Delta was very limited because the Loma Prieta earthquake was centered over in the Peninsula, so it was much further away than, for example, the Hayward fault. That was the only major earthquake we’ve had since we had the problem of the islands going below sea level – there hasn’t been a major earthquake to affect the Delta since that happened. The 1907 earthquake occurred of course, but at that time all the islands were still pretty much at sea level so we didn’t have this liquefaction problem.” “It is generally agreed that the 1906 San Francisco earthquake occurred in 1906, not in 1907. . . . Any liquefaction problem in the Delta is unrelated to whether or not the islands are subsided. Maybe Dr. Meral meant that we did not have the same potential salt water intrusion problem in 1906, but who knows?”In a 1985 article on Delta Earthquake Damage published in California Geology, Michael Finch of DWR said that “Much of the Delta was already below sea level during the April 1906 San Francisco earthquake.”
“A very interesting thing happened in the Loma Prieta earthquake, though. There was an old barn. It was a pole barn, and it had been demolished, but the poles were still in the ground, and the soil around that area liquefied enough so that the poles floated up, so when someone came out the next day, they saw these old poles sticking up out of the ground, which shows the liquefaction potential.” Says Dr. Pyke, “The pole barn story is apocryphal. The original report by Michael Finch was debunked in a 1992 DWR report that points out that Venice Island, where this allegedly occurred, was flooded at the time.”,The reported incident actually involved pilings of an abandoned horse barn – an unlikely structure to find on Venice Island, as those familiar with the Delta will realize.,The incident was purported to have occurred during the 1983 Coalinga earthquake, 150 miles from,its epicenter, not during the 1989 Loma Prieta earthquake.
“But we really haven’t had a big earthquake since the Winter’s Fault back in the 1890s when the Delta was mostly not even reclaimed . . . .” “The Winters-Vacaville earthquake sequence of 1892 occurred ‘within a zone of active crustal shortening accommodated by postulated blind thrust faults,’ not on Winter’s fault, which does not exist.”
If there is an earthquake and we have multiple island failures, then the sea water will come in and eventually the Delta becomes salty and you can’t export water, Dr. Meral said. “This is a serious consequence for the entire state of California. It would take a long time to repair the islands, pump them out and get fresh water going again. How long we don’t really know, we’ve never had a multi-island failure of this type. But certainly it would be more than 6 months and it could be up to three years. If enough failures occurred, it could be 10 years.” Says Dr. Pyke, “The latest studies for the DWR conducted by RMA and Jack R. Benjamin & Associates indicate that even in a worse than worst case event, an undefined earthquake causing 50 levees breaches and 20 flooded islands, a scenario that has an annual probability of occurrence somewhere between 0.1 and 0.01 percent, the Delta would likely flush out within several months or six months at the most. In the case of levee failures in a major flood, the Delta will already be awash with fresh water and the demand for exports would in any case be low.”,In a normal or wet year, reservoirs will likely be full and fields sodden.

Not so. And Dr. Meral got some other important things wrong as well, fueling the ongoing misinformation campaign about Delta levees and the earthquake threat to water supply. Here’s a list of the facts, courtesy of consulting engineer Dr. Robert Pyke. (Thank you to Chris Austin — Maven’s Notebook – for the transcription of Dr. Meral’s comments, indicated by quotation marks.) The entire state of California faces serious and ongoing threats from earthquakes. Dr. Meral and BDCP proponents continue to exaggerate earthquake threats in the Delta as an excuse to throw tens of billions of dollars of ratepayer and taxpayer money into building tunnels that will savage the Delta region without guaranteeing export supplies. This is stunningly irresponsible.

They aren’t crumbling, but they do need maintenance

DWR consultant Jim Watson told Westlands Water District directors in November that DWR engineers worry that tunneling 100 feet under aging and crumbling levees in the Delta could cause them to collapse. Tunneling under the San Joaquin River, he said, will also be a challenge.

The levees aren’t crumbling, but they do need regular maintenance. How will they get that during 9 years of tunnel construction?

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