Unexplained evidence: New York Times new take on Oroville dam
high springs on the right abutment
If you look closely and magnify the second of the excellent photographs in the Christopher Cox New York Times feature article on the peril of California dams, out today June 22, 2023 and written in the style reminiscent of John McPhee, you will see that the repaired spillway appears to be now, on it’s first fill after the spillway replacement in 2017, operating quite satisfactorily. Slightly to the left in that photo (the second photo in the NYT article) you will see a large white roughly rectangular area. That is the improved emergency spillway, now covered with light colored concrete to prevent erosion. The eastern part of this improved area exhibits black seepage lines from springs which break through the concrete (red circle).
“Well”, you might say, “nothing strange about that, after all the reservoir is now full, and the water level in the surrounding rock must be raised as well.” But now, if you head over to Google Earth and search “Oroville dam” and look at the same area, the satellite photo shown on Google Earth and reproduced above is from an earlier date when the reservoir was quite low. In that Google Earth photo, you can also magnify the emergency spillway to a higher level and see in fine detail how several significant springs flow persistently from topographical notches high on the hillside even when the reservoir is low. This is consistent with the “mystery spring” noted by the IFT.
I can tell you that the 2017 independent review panel, much quoted in Mr. Cox’s article, was concerned with springs on this side of the mountain as possibly related to the failure of the overloaded spillway underdrains, which they propose and which is generally accepted as the principal root of the failure. I have noted the presence of other springs in and around both spillways near the failures and confirmed that they existed even late in the 19th century, long before the construction of the reservoir. But on questioning by the investigation panel, DWR was unable to properly document the history or ongoing activity of these significant hydrogeological features, which left an important loose end to the safety review. The panel, pressured to produce a tightly scheduled report at the end of 2017, insisted that DWR should follow up with proper studies of this phenomenon apparently concerned about the role of springs in addition to the defects in the chute slabs that they theorized allowed jacking pressures leading to failure. There are indications in the record that some such studies were subsequently performed by DWR and may still be underway. I have requested access to this information. Although knowledgeable DWR staff have been directed not to discuss this with me on direction from the State lawyers, the DWR office facilitating public review of records has been most cooperative.
Figure 2: June 26, 2023 current spill and emergency spillway springs. Can be tracked from week to week. Field verification needed.
Why should this important information be secret? And what should members of the public or the engineering community concerned with dam safety do to assure that the DWR carries out its responsibility to keep the public and dam professionals informed of conditions related to the ongoing safety of the Oroville dam? I have a request to DWR for this information. Keep posted.
This posting is part of my series on Oroville Dam. The introduction can be found here.
