Posted on 02/12/2017 4:26:47 PM PST by janetjanet998
Edited on 02/12/2017 9:33:58 PM PST by Admin Moderator. [history]
The Oroville Dam is the highest in the nation.
I agree with you on "head" reservoir levels and a corresponding "flow" rate. Essentially, there is much information that should be swiftly determined regarding this issue at the dam as there is likely more "internal" factors in the dam at play that may be "unseen" (per the prior discussion of the metric of Green Area surface observations).
I believe this issue will now become forefront with the public. Documents now establish that DWR (and indirectly FERC) are tied to a disaster potential liability that would be sustained in a court of law - if anything were to occur - from this form of "negligent" inaction (based on evidence of such a high potential risk factor).
Because of the "unknowns" (i.e. greater flows "unseen") and the resilience of the Wet area even in hot dry drought conditions, there is strong evidence there is something larger at play. This fact alone may force the question - Should the dam be only allowed to operate below this "wet area"? Or more harsh, Without the ability to assess the structural stability of the internal state of the dam with zero function safety device sensory Piezometers, should the dam be lowered to a level to "make safe" for the structural lower part of the dam to insure a safety margin?
There are other dams that are operating under these exact lower reservoir level limitations due to issues related to insuring a "safety margin".
Oroville dam's release capacity at the Hyatt power plant is the problem. The dam can't keep up with high levels of inflow. Thus, to insure that the dam does not exceed the "leakage area", does that mean the reservoir level has to be far lower to account for an inflow? (this could effectively force the dam to operate with extremely low levels in this case).
No easy answers right now.
The August 1, 1975 Oroville earthquake investigations
by California. Dept. of Water Resources
Published 1979
https://archive.org/details/august11975orovi20378cali
One thing you are asking is “where did the dirt come from?” I will hazard an answer from one who is used to thinking outside the box.
We know there is some weedy grass growing there and reappearing. It really does not take dirt.
As we know from football fields on drainage media and golf course greens over coarse sand, grass of the right type will grow anywhere. I have seen grass seed grown on a face of a course concrete block which is immersed in water.
We have already seen a mechanism to migrate silts, clay sands etc from the general dam fill and it takes very little of it’s kept wet with local wind blown seed to have started a turf. The turf is perineal as we see it fade with the winter season but it comes back. It comes back because the rhizomes give a media that the constant seeping moisture needs for the grass to come back each spring, self seeding and from laterals.
One of the reports recommended it be cut — perhaps it has been cut with weed eaters. If so the cuttings make more turf growing zone.
We don’t need dirt to grow grasses — JUST WATER.
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The green area with aprx elevations.
This photo also shows the "proto-lawn", areas which seem to be the core of the growth over many years.
These "depositions" came from "through the dam" flows, just as the Green Wet Area today is from a "through" the dam flow. Flowing water must pass through the "Silts" in two Zone 2 sections and the Clay-clayey soil base in the core. This water flow is maintaining a "bench" flow to get to the Zone 3 surface. In order to maintain an internal "bench" flow there needs to be a form of a non-pervious ratio of material - i.e. high silts, clay, clayey soils. As this water flow "rides" over the time generated formed silts, clay, clayey soils, it brings these fines to the surface at the Green Wet Area.
For the water to even get to the Zone 3 side from the Zone 2 Transition layer, the water has to cross the 20ft wide Drain Zone. Normally, this Drain Zone can handle all of the intended life of the gradual (normal) seepage. This includes the traces of sands and silts and clay clayey soil materials. They would Filter down through this Drain Zone for the life of the dam.
As designed & working correctly, there would be zero pore pressure past the Drain Zone. The normal Phreatic Surface would curve directly into the Drain Zone Chimney.
However, Oroville dam's Drain zone has been "clogged" at the differential settlement area above the Green Wet area. Just as this "clogging", by overwhelming the Drain with Transition zone materials, the "bridge" is a non-pervious rich clog. This same "clogging" effect continued to migrate in the Zone 3 internals. The original layered construction "guided" the early differential "clogged" flows at the sectional layer seams. The more the flow continued through the Core region, the more "clogging" material would deposit in a "flow" bench. So this chain reaction internal clogging effect is the same effect transporting "soil rich" materials to the Green Wet area. There likely is a curvature of this phreatic "guided" bench to where the inner flow disperses in percolation arcs. This forms the baseline estimate in the "stepped" guided layer illustration in the upstream thread. The "outer reach" of these bench guided percolation arcs is where the material + water reaches the Green Wet area. The differing concentrations of clogging material, formed at different arc conditions, creates the staggering of the thinner horizontal seams of concentrated growth within the large green region. IN addition to the arc's the original compaction strata of construction helped form and guide the deposition of thinner horizontal seam strips.
I fully agree that grasses will grow in minimal conditions. But in this case the water cannot reach the outer Zone 3 surface Green Wet area without flowing atop these extended "clogging" transport layers of silts, clays, clayey soils. The extent of the width of the subsurface saturation evacuation of granular "sands" deeper below the Zone 3 layer in the Erosion Zones is overspill from the "deposited" silts, clays, clayey soil material at the Green Wet area elevation and this remaining overspill saturation flow had high enough pore pressure to disassociate the deeper Zone 3 consolidation - thus enabling the formation of the mysterious "size growing" Erosion Channels.
The Erosion channels have been the key to guiding the evidence of "looking inside the dam". The next greatest key was what the dam demonstrated in the original twin differential settlement seams (saturation flows, deposition of high concentration of "fines" creating "dirt patches", clogging the drain zones in two areas to facilitate the Zone 3 penetration, the sectional seam layer preference of water flow, and the subsequent contrast of the "washing" away of the deposited "patches" where there are no Green Areas there today - but it left a "Clean Surface" in additional consolidation with the Zone 3 surface material).
Thanks Ray76.
Although it is hard to tell from from these thumbnail images alone, it does appear that the green spot was not as green in June 2011, when the lake stayed close to 900’, as it is in May 2017, when the lake is averaging closer to 850’. This appears to indicate that the greening of the green spot is not a direct function of lake level, even in the Spring, before it gets hot enough to potentially kill off the grass. It will be interesting to see how quickly the green spot browns out this year.
Haven't checked all of them regarding green spot, but saw this interesting blurb about instrumentation in the Jan. 20, 2004 report:
On the Nov. 18, 2002 report, the 1999 Dam Review Safety Board is said to have made the recommendation. The inconsistency is irrelevant but interesting nonetheless
Now, not only were only 51 of 56 Oroville Dam piezometers noted to not be working 13 years ago, but it was the actual Dam Safety Review Board that specifically recommended that they should be retired (and eventually were). This simply defies all logic, and I'm just some idiot on the internet watching this from a thousand miles away.
Is there any rational ENGINEERING reason for such a recommendation given the history of dam failures they might have prevented if used? It's like an airline's 'Safety Board' recommending a few panels of gauges be pulled out of a modern passenger aircraft because some are broken and the information can be gathered indirectly through other means (like 'high-speed disassembly at altitude' or 'contact with terrain').
here’s one
Robert Bea, a UC Berkeley professor emeritus and co-founder of the school’s Center for Catastrophic Risk Management, said replacing the spillway is not enough.
He said the gate structure that controls releases from the dam has cracks and broken anchor points. He also said the state needs to pay closer attention to wet spots on the face of the earthen dam to make sure it is not seepage through the structure.
http://www.latimes.com/local/california/la-me-oroville-dam-criticism-20170512-story.html
another with a little more info...about retired engineers.....
Bea concluded there were problems with the spillway at the design phase, which continued on through construction phase, and continued undetected through decades of maintenance and operation.
Part of his conclusions came from three retired DWR staff who he has promised not to name, he told the committee members.
When he looked through inspection reports he saw “cracks that have been painted over,” and broken anchors at the spillway gates, Bea said.
DWR has said the green spots on the dam are naturally occurring. Yet, Bea said there should be more investigation. “In my view, nothing like that is taken as natural until proven natural.”
If the Oroville Dam wet “green spot” is caused by lake water flowing through a leak or crack, that flow rate of water and/or particles through the dam must be a function of the driving head, measured by the lake elevation.
The observed phenomena:
1) greening or browning of various vegetative patches within the green spot area, and
2) creation of a high density of long vertical channels weeping out below the green spot area
must both be a function of this lake elevation generated flow.
The highest lake level in recent record was during the spring and summer of 2011, when the lake was within a few feet of topping out for months on end. The only time the green spot flow rate would have ever been higher is for just a few days in Feb 2017. The aggregate volume of green spot flow would have been greater in 2011 than (so far) in 2017.
It appears from the photographic evidence readily available so far that this year’s green spot has been greener than any year within recent photographic record, including 2011, when the aggregate flow to the green spot should been higher. However, DSOD reported wet moisture in February and May of 2011, and there is an unconfirmed report for October.
IMHO, if more evidence comes out that the green spot remained green or wet through the late 2011 summer , then that would be almost conclusive evidence that the water originates from the lake. However, if the green spot dries up as the lake rises this June, then this indicates the green spot is not sourced from reservoir water.
These news links you reference - I believe these are tied to yesterday's State legislative hearing on the dam. Seems DWR was hammered at the hearing.
Another new SacBee article reveals that DWR & California may not be federally compensated if this spillway failure was from improper maintenance. Only if the event is considered to be a natural disaster is the key consideration to federal assistance funding. There must be intense pressure on DWR given how events are progressing (i.e. people coming forward, more info & reports not looking so good, new subjects being discussed - like the leak, etc).
Prof Bea brought up the Anchor tendons that had failed at the Oroville flood control Radial Trunnion Gates. Speaking of which. I've been sidetracked on the anchor tendon postings. Here's one for you. It gives some engineering insight into how "numbers" can be shuffled in a pinch.
Failure analysis of failed tendons (steel bars stretched to near 160,000 psi tensile load) found that a cut or crack of 1/8 inch was the critical failure size.
So early on a number of 1/32 inch was chosen as "considered significant". Yet the 1/32 number reveals it was sort of a "let's choose something that is a round number of 4 times less than the failure size". Actually, the surface area (ignoring the "v" width) of an ultrasonically tested anchor rod crack is 783% decrease in area from 1/8" to 1/32". That was in 1999/2000. Fast forward to 2012 and magically the new number to be concerned about is 1/16 inch....but hang on....DWR renamed the crack of "considered significant" at 1/32 inch to a "minor flaw" at 1/16 inch.
There is more to this story... but you get the picture. (btw- for engineering lurkers... even the 1/16 inch swizzle didn't help them as 12 anchor tendons have cracks above 1/16 inch & even one close to 1/8 inch from back in the original 2000 test report data findings - yet DWR has done nothing to replace these identified cracked tendons).
Engineering swizzle games? Don't worry about the math, just peruse the marked up comments.
The green areas appear rather uniform in historic imagery and at some point (2009?) it takes on an odd, mottled appearance.
This reminds me of the appearance of railroad embankments in my neck of the woods. Being too steep to mow but very visible to the public in places, they would 'mow the weeds with a hose' in the 80's and 90's. When the sides of the embankments would grow back, they would take on the same kind of toxic waste dump mottled look from herbicide residue and stayed that way for a decade. These herbicides are suppose to be a one-time deal, i.e., they are generally not designed to be persistent.
Yeah, I'm sure they are not suppose to do that and, of course, the green areas serve as a sentinel marker of seepage. But who needs seepage detection anyway? Seepage means the FERC boys will get all riled up and who needs that kind of attention? It's just from a natural spring anyway - hose it down with RoundUp and make the problem disappear.
The source of the water for the green spot is obviously a critical issue. What happens this summer may shed some light on that.
IMHO opinion, however, the CRITICAL issue is the trend. If it is worsening we have a major problem that must be addressed as soon as possible.
The green spot provides a very crude measure of this. If it is worse this year than 2011, especially since the average lake elevation is likely to be less, then we may be looking at a worsening trend.
Worsening water flow will NOT be linear even if it appears to be in the early stages. Once it starts to worsen it will accelerate slowly at first, but the rate of acceleration will increase over time.
The head of water (only that above the leak) pushing water through the dam is variable, hence the volume of water is almost certainly variable as well. The volume of water and rate of flow of that water will impact the time it takes for some of that water to reach the green spot. Put those factors together and you have a very hard to estimate, but nevertheless non-linear, curve.
The acceleration will not follow an easily extrapolated exponential curve, but that is basically what it will be.
So a natural disaster cause is being used to attempt to make this Fed dollar eligible. Then, when the spillways are repaired they will go back to the Feds and say we discovered the Gates are bad. After that is paid for the monitoring will show settlement is going to allow a dam blow-out at the Christy Jones Memorial Lawn and Undermined Area and Fed dollars will be needed again.
All because California government and voters won’t do their jobs. I am sick of paying for this crap.
In my many years on the Earth I have learned one lesson that has served me well.
Government management and intervention in complex issues only insures that the event will reach epic disaster scale before it gets better or turns around.
In a sane world DWR would be, at this point, slowly barbequed by the Kalifornia Legislature. The misfeasance is breathtaking.
Sums it up nicely.
I think it is the objective, or at least the hope, of most on this forum that further elucidation of these issues will help lead to their effective remediation. We’ve already found that many of the issues identified in past months have made their way into the press, and thereby into the Legislature, and now DWR is being held accountable. Ideally DWR would be proactive, but it appears that the collective experience on this forum is that the only way DWR will react is via increased public scrutiny.
The key questions regarding the green spot are:
1) Where does the water come from?
2) Is the problem getting worse?
3) How can this be fixed?
The first 2 questions are correlated. If the water is coming from the lake, then the source is essentially unlimited. Once it starts to flow, there could be no mechanism to stop it other than lowering the lake in time.
If the source is rain induced groundwater, that will dry up every year. However, the flow channels could eventually merge with lake water, again yielding catastrophic results.
Right now, we (the public) have no quantitative knowledge on the green spot other than what is reported biannually via DSOD, and what time dated photos have sufficient resolution to make out the green spot. Quantitative data is needed.
IMHO, the quickest, cheapest, and easiest way to acquire this would be to place an array of wireless moisture sensors within the green spot area. If that moisture level (compensated for temperature, wind speed, humidity, and solar radiance) is correlated with lake level (assuming plausibly nonlinear delays), then the water is coming from the lake. Additionally, examining the mineral content can help determine if it is groundwater or from the lake.
Stepping up a notch on the cost/time/expertise needed, the dam could be thermally imaged with FLIR cameras, as ER333 has recommended. A high res 3D profile of the dam should be generated from terrestrial Lidar and/or satellite data, and this should be tied into the existing survey benchmarks to assess the long term settlement of different parts of the dam. Experts such as ER333, Scott Cahill, and Professor Bia would and have suggested additional nonintrusive diagnostics.
Based on this data, a new plan could be developed on where to install new piezos and other in-dam instrumentation. Being intrusive to the dam’s integrity, this would involve considerably more time, money, engineering expertise, equipment, and institutional approval.
Once a valid water migration map is developed for the dam, grouting or other remediation efforts can be initiated. This would be a long term effort, as it would take a year or more to determine if the remediation had been effective.
The best I think we can do here is to help bring this issue out in the open and hope that DWR sees fit, or gets told to see fit, to take action on it. If the green spot dries up over the next month or two, then it may be another year before these diagnostics can be effectively initiated.
Good post, with one quibble. IMHO you went way too easy on DWR.
Unfortunately, DWR has done a demonstrably terrible job at maintaining this dam. They have shown a great willingness to coverup, obfuscate, and outright lie in order to prevent the public from becoming aware of just how egregious this has been. They are covering for themselves, and for the politicians they serve.
To counteract this DWR requires IMMENSE public scrutiny. The news media does not have the expertise to do this.
This thread is one of the best on the net at providing the information and analysis needed for that purpose.
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