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Hi EarthResarcher333.
Re post 3718:

You have a point and I rescind the claim that the concrete “chunk does appear to be from one of those extra thick sections”. I don’t know what part of the spillway it came from.

My point was that most smaller chucks of concrete got washed away, and that one didn’t, plausible due to it’s weight and thickness. It did certainly enter my mind that this thickness could be do to post construction “void filling”.

Hi EarthResearcher333.
Regarding issues you raised in post 3717:

LIDAR

The LIDAR used for the “Google car” and many other autonomous vehicles has a stated accuracy of 2cm http://velodynelidar.com/hdl-64e.html , although it does sample millions of times a second, yielding a point cloud resolution better than that for flat surfaces like roadways. Measurement of the large cobbles on the upstream slope of the dam would be noisy, but this could be partially mitigated by oversampling. As you say, the grassy downstream slope would be more of a issue, especially with the Green Spot grass at varying heights.

However, I think such a point cloud resolution should be sufficient to investigate if there are substantial settlement discontinuities across the dam. This would not have the resolution of InSAR, but would be faster/cheaper/more available for a preliminary investigation. Either measurement technique would have to tie into the same survey monuments used for the 1975 DWR Settlement Report cited in post 3624 (or others as available) to determine the past time rate of settlement.

Microprocessors

I suggested the use of an array of microprocessor based moisture sensors to determine if the Green Spot moisture is correlated with reservoir elevation. These are COTS items commonly used in California during the drought - simple and cheap enough that they can be quickly installed. To me, the most critical question is “Dose reservoir water seep through the face of the dam”, and these embedded micro controllers would help determine that question one way or another.

I also suggested that some type of access to instrumentation be embedded in the new spillway as it is being constructed so as to better diagnose problems before they manifest. In lieu of dragging chains over the spillway in the hope that a trained ear will pick up subtle changes over the years, perhaps it might be better to have embedded microphones detect any acoustic changes as a function of spillway flow? My post was more concerned with the types of detection that might be useful, rather than how to write C code to collect the data.

Lighting can fry any outdoor electronics, but that’s not real common in that area of California. However, critical instrumentation should be accessible and replaceable if it fails for any reason.

Hi EarthResearcher333.

I apologize if you have found some of my posts annoying. That’s not my objective. The most robust explanation for any phenomena is the one that can sustain the highest level of scrutiny. I have offered some alternate perspectives that may or may not be valid, and are certainly subject to scrutiny, as you have done here. I will attempt to refrain from euphemisms such as “sharpest crayon in the box” if that bothers you.

I agree with all 4 of your points in post 3714.

As to your last point, IMHO a key reason DWR doesn’t act upon recommendations of DSOD is based on the acronyms themselves. DSOD is the Division of Safety Of Dams, which is just one of many divisions of DWR, the Department of Water Resources. A Division of a Department cannot effectively regulate it’s parent organization. Engineering staff of both DWR and DSOD (within DWR) share the same job classifications and promotional opportunities. It is unrealistic for an engineer in DSOD to come down hard on DWR knowing that they may be promoted there next year.

DSOD and DWR need to be separated. I don’t think anyone on this forum would disagree with that, but there’s the question of what a more effective regulatory structure would be. Other states must do this differently.

ER333: you always have interesting, well researched, and thought-provoking posts. Again, many thanks.

Regarding the concrete chunk you reference, Bill Crowle from DWR did say that the spillway slab was 6 foot thick in sections, and that chunk does appear to be from one of those extra thick sections.

On one hand, I’ve worked enough construction to know that no contractor will lay down 6 feet of concrete if they can get away with a 1 foot slab on top of whatever type of (erodible) base material they were using. The contractor pays for every truck load of concrete, and that comes out of their profit margin, which they’re generally rather concerned about. This would be an argument for there being a 1 foot base slab, with the rest mud jacked in years later, as you suggest.

On the other hand, from the picture, the entire chunk of concrete appears monolithic with the same mix design, and I couldn’t see two lifts of concrete placed a couple decades apart tumbling 1000 feet downstream as a monolith. I think we’d need a closer examination of that chunk of concrete to make the call.

If they did mudjack the slabs, it seems plausible this could plug up some of the diagonal under-slab drains. However, I couldn’t see this plugging up the longitudinal side collector drains. This would be too easy to check for, even in the pre-borehole camera era. You just pour water down the upstream vent tube, and if it doesn’t come out the downstream sidewall port at the same rate, then you know you have a clog between the two. DWR may not be the sharpest crayon in the coloring box, but you’d have to be a total idiot to let a spillway contractor walk away from the job with a paycheck without checking for a clogged drain.

If a tree root was a contributing factor to the drain clog which precipitated the spillway failure, and we know the drains were under high pressure, then it seems plausible that the pressurized water could escape along the root pathway through the fill to the side of the spillway. This would provide a high-volume escape route for the water, taking more more base material with it. Some pictures appear to indicate the side of the spillway was blown out before the major slab failure.

If the pressurized water had no escape, it would push the slab up, “hydraulically jacking” it. If the water had an escape route, it would go longer be pressurized and spurting out the sidewall, but eroding underneath it, and the slab would fail downward. Up or down, the slab failed one way or the other.

A contributing factor to both the spillway failure and FCO structure problems which hasn’t been examined in this thread (to the best of my knowledge) is concrete shrinkage. Some old mix designs would shrink quite a bit. With the extra large slabs they were using on the spillway, the expansion joints could pull apart, letting more water under the slabs than could be caulked out. This could also contribute to why FCO is now 5 1/2 inches shy of the fixed foundation at the abutment, and cracking at the seams.

To build a R/C structure and that needs to function reliably for a 100 years or so, I’d go with an expansive mix design, using a type K cement. This has Ettringite (calcium aluminum sulfate) added. There are type K slabs which are approaching 50 years old, the same age as Oroville, that are still in almost perfect shape with no cracks or joint issues.

A plausible hypothesis as to why a tree root may have grown adjacent and then into the drain at the blowout failure location is that there was a natural “Water Percolation Seam” at this location. The native geology of the area appears to contain a great deal of fractured and erodible rock with many fissures that water could percolate through. It is also plausible that such a seasonal “Water Percolation Seam” could be injecting moisture into the side of the dam, creating the (apparently) seasonal “Green Spot”.

ER333:

Hope your ticker is doing OK. Please don’t get too stressed out. The world needs your experienced perspective and insight.

I have a couple of questions regarding your recent posts.

The painted red crack shown in post 3671 is from a Feb 2015 DSOD report, isn’t it?
If so, at that time the FCO gates hadn’t been used for years, and the reservoir was below the FCO inlet, so there was no head pressure at all on the gates or structure. If the crack was growing then, it had to be from concrete shrinkage or settlement and drying of the foundation. I think I recall Scott Cahill saying that he thought the back side of the FCO foundation was partially built on fill, so perhaps that could have something to do with it.

If the FCO structure was cracking in 2015, one can only wonder how it’s working now. The gates were recently under greater static head pressure loading then ever before, and they’ve been dynamically opened and closed more times this year than in the last decade. Also, that heavy truck traffic no doubt stressed the structure way more than the pickups with speed boat trailers that it was designed to carry.

Question: if 2 of the 384 anchor tendons “failed” in 2010, how did they determine that? Did they get no ultrasonic reflection at all? Were these rods completely fractured? Or did they rate 1/8” rather than just 1/16” on the ultrasonic test?

I too would very much like to see how they went about coring and replacing them.

It seems strange that 2 rods failed to the point that they needed to be replaced a decade or so ago, but none of the other 382 have structurally failed since then. Was there a QA issue with just those 2 rods, or were they somehow tweaked due to their position relative to the cracks in the FCO structure? Were they both adjacent rods from the same gate? One might think that other adjacent rods would have failed by now with all the recent high stress dynamic loading on the FCO.

There are many questions to be raised if and when DWR becomes more accountable. With Oroville’s DSOD “regulators” just being just another internal division of DWR, it appears that this accountability will have to come from outside independent scrutiny. Please keep up the good work as you are able, and the scrutiny will be applied.

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.

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.

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.

EarthResearcher333:

One thing that struck me regarding the DWR settlement report that you cite was that the date of the last survey was apparently mid July of 1975.  Wasn’t the Oroville earthquake on August 1 of 1975? Assuming that it took a few weeks to generate this report, then it would have come out right after the earthquake.  I would think they would have included at least one more survey to assess the pre-quake settlement to the post-quake settlement, which most plausibly was greater than 2”.  

DWR’s data collection, management, and reporting practices are a mystery to me.

I also find it amazing that DWR could just “loose” most of these survey monuments.   Them loosing functionality of piezos buried in the dam is at least fathomable, but loosing monuments on the surface?  I would think any decent survey crew armed with the original notes should be able to forensically find some or most of them.  As you indicate, knowing what that settlement is today would be quite a useful piece of this puzzle.  

You cite a July 2015 DSOD report that says there was still noticeable but “relatively low” seepage, even when the lake was at 700’.   Isn’t the elevation of the green spot around 660’?  If the wet spot has noticeable seepage with only 40’ of head, then it should be flowing a lot better at 900’, with 6 times that head, like it for had much of 2011.

In one of Scott Cahill’s latest videos https://www.youtube.com/watch?v=y-7DSoTlc_Y , at around 10:25, his wife quotes an October 2011 DSOD report that says the wet spot still had “lush vegetation that should be trimmed”.  She even remarks on how unusual this was for October.  

I haven’t been able to find this DSOD report.  However, 2011 was the highest the lake has been through the summer, so if the green spot still had lush vegetation at that date, then the water had to be coming from the lake.  I guess it could be that all my boating buddies were just too drunk to notice.

Do you have access to this Oct 2011 DSOD report?  If so, could you please post a link to it?  

It appears that most of the DSOD reports repeatedly call for DWR to actively monitor this wet spot, which they have repeatedly ignored. There are relatively cheap wireless moisture and temperature sensors which are used in agriculture that could be placed in this area. If that data were correlated with solar intensity, wind speed, humidity, rain fall, and lake level, then it should be possible to get a better handle on how much water is coming thorough. Hopefully, getting DWR to install better instrumentation will be a positive outcome of this effort.

However, in my mind, “lush vegetation” growing in October would be definitive proof that the wet spot water is seeping from the lake.  

Then there is still the question of how the vertical channels underneath formed, which I’m hoping you’ll elucidate further.

To EarthResearcher333: as always, I am amazed at the breath and depth of your posts.

However, I would appreciate a point of clarification:

I’m not sure I’m correctly interpreting the “differential settlement diagram” from DWR that you provided in post 3624.  
It appears that the scale on the right of this plot is in tenths of feet (of settlement, I assume).  If so, your small circled arrow on the right appears to indicate about .03’ settlement at around station 65, and the larger circled arrow to the left indicates around .18’ settlement at station 57.  That would be less than 2” differential settlement across that distance, which doesn’t seem sufficient to shear the dam and induce cracks that water could flow through.

Am I not interpreting this diagram correctly?  
What is the actual magnitude of differential strain in the dam that would cause the phenomenon that you describe?

Occam’s razor indicates that these erosion channels (and by inference, the “green spot”) are not formed by reservoir water because the channels are not flowing when the reservoir head is the highest. The simplest explanation would be a rainwater fed “seepage channel”, just as the dam builders had noted during construction. If this is a deep channel with a small catchment basin, analogous to the sink hole that almost opened up under the emergency spillway, then it might normally generate low flow seepage to keep the green area wet in the winter and spring. But during intense rain, it could gather enough water to generate the visible erosion.

It would be useful to include an assessment of current 2017 photos in this green spot erosion assessment. Did the erosion channel rock pattern change this year? If not, that wound’t necessarily be conclusive.

This year had the greatest aggregate precipitation, but not necessarily the most intense. The most intense precipitation in the Sierras is during short duration thunderstorms. It is plausible the (hypothesized) catchment basin only fills during intense thunder showers, which then flows down and into the dam with enough head to erode the surface channels as the flow perks out. This could explain why the (hypothesized hilltop) catchment basin is small enough to be unnoticed, and why no one (apparently) has seen these dam erosion channels being formed, because the rain was so intense that they were seeking shelter.

All speculation? No doubt. That’s largely what this forum is all about.

A Q&D diagnostic that could be done would be to place various size and colors of stones in the erosion channels that would move or get washed away at different flow rates. That way it would be relatively easy to do a remote assessment of if and when the erosion channels have been reactivated. My speculative hypothesis is this it would be after thundershowers.

In any case, if there are existing piping channels through the dam that can sustain enough flow to erode its surface, and those channels ever merge with the reservoir water, then this could quickly develop into an uncontrollable situation. We all need to put and keep the pressure on DWR to resolve this issue before it resolves itself.

Good tidings EarthResearcher333. Thanks for your many thoughtful and well documented posts.

In regard to my post 3574, you ask:

“Why are you making these inferred assumptions? (thousands driving over & no one registered much concern about it at the time) & (This (apparently wasn’t an issue at the time)?”

Admittedly, these are just assumptions. However, I’d classify them as more “informed” assumptions than “inferred” assumptions. Either descriptor applies.

I’ve done a lot of boating in California and have been on many lakes, although I avoided Oroville, partly because I’ve always heard it was too crowded. The day use boat ramp north of the dam is 13 lanes wide with hundreds of parking spaces. If they had just 20 boat launches a day during this 3 month period in 2011 when the lake was higher than its ever been, at 2 people per boat, that translates to “thousands” of potential dam observers. I don’t have the actual traffic counts though.

Northern California is generally green in February, drys out by May, and is universally brown by August. A wet or green spot would definitely stand out in August, but not so much in February or May. I have never known fellow boaters to take notice of a green area on any dam in August, or heard of it on social media. It is my assumption that they would have taken notice of this, and records of this would have come out by now. But that is a rather speculative assumption.

If the “green spot” water is originating from the reservoir, then the flow rate into it must be a function of the reservoir level. As Ray76 pointed out, this is key to assessing where this water originates.

The DSOD report from 2/2/11 you cited says “the area ranged from damp to wet”. On that date, the lake level was about 826’ according to DWR. The lake level didn’t get down that low again until January the following year, so the same flow rate or more should have been sustained across this period.

The DSOD report from 5/18/11 you cite says “the ground remains wet” with “lush grass and weeds”. At this time, the reservoir was about 887’, 60’ higher than the February report. The green spot would have had quite a bit more head on it, but significantly greater flow was not apparently observed.

Now if we had a report from August through October 2011, that still said this area remained wet and green, then it would be reasonable to conclude the only plausible source of water would be the lake.

Another key thing to assess is how the vertical channels below the wet spot got formed.

At some point in time, this wet spot must have been flowing sufficiently to generate these multiple erosion channels, many of which (I’m assuming) would be flowing concurrently rather than sequentially. It takes a lot of flow to push a steep cobble embankment aside rather than perk back into it. That peak flow event must have been at peak lake level, if the water originated from the lake. The longest sustained peak lake level (+890’) was the summer of 2011, when (I’m assuming) no one noticed these channels being formed.

Now it could be a plausible assumption that this peak wet spot flow, associated with peak lake level, might have evaporated away when perking out on to the hot SouthWest face of the dam in the summer. However, even in the summer, it can get kind of chilly at night. I find it hard to believe that a flow rate sufficient to erode multiple channels down the face of a cobble embankment would just evaporate away through the night every night for months on end. That doesn’t seem plausible to me, but I could be wrong.

If those erosion channels were initiated by high lake levels, then why would they stop eroding as long as the lake was high? Once there is sufficient pressure and flow to push the surface materials aside, wouldn’t that process cascade until the dam collapsed? Unless that flow originated from a much more limited source, like a rain fed groundwater channel.

Upthread, a thousand or so post ago, I thought it seemed plausible that the wet spot water was originating from the reservoir. However, upon reasoning this out, it now seems more reasonable to me that this water originates from some underground channel or other rain induced source. Obviously, no one, including DWR knows what that source is at this time. It is an issue that should be investigated, and then mitigated. But I think the imminent threat of a Teton Dam style failure seems minimal, at least until the next rainy season. I’m downstream of the dam, so I do care about these things.

There are two outwardly visible characteristics of the Oroville dam “wet spot”. First, it’s “green”, indicating it generates enough water sustain plant growth. Second, there are visible vertical streaks below it, indicating at some point there was enough water percolating out for multiple channels to flow down the surface of the dam for some distance.

One hypothesis is that this flowing water originates from within the reservoir. When the reservoir level drops below the elevation of the wet spot, the wet spot dries up. Conversely, when the reservoir rises, the wet spot must get wetter. Ultimately the flow rate to and through the wet spot would have to be a function of the driving head, or reservoir water level.

Six years ago, around this date, Oroville was running close to 890’. According to DWR’s online records, the reservoir stayed in this range through mid August. No one registered much concern about it at the time. Indeed, most would consider it prudent to max out the use of the reservoir, assuming its safety was assured.

During the 3 months in 2011 that lake was at this 890’(+) stage, thousands of people drove over the dam to get to the boat ramp. One might assume these individuals would be highly motivated to notice an unusual green spot, water percolating out of the dam, or any other visible sign that the reservoir they entrust their family’s lives to was in any way impaired. This (apparently) wasn’t an issue at the time.

Even if there is a delay in water getting to the wet spot due to some hysteresis effect of pressure migrating through the dam stratums, the pressure and flow would stabilize after 3 months of constant 890’(+) head. The maximum flow rate to the wet spot would be when the head was highest for the longest period, which would have been in the summer of 2011. Even if much of this water evaporated when percolating out the SW facing slope in the daytime, the vegetative green spot should have become and stayed greener longer than has been the case in 2017, when the average lake level has been 40’ lower.

Alternate hypothesis:

It appears that the local geology consists largely of weathered brown rock and harder blue rock fractured together so as to easily form erosion channels. There is a large hill at a high elevation on the left bank. It is plausible that rainwater flowing in a ravine above the left channel sinks down into a plunge pool, through a million year old erosion channel, and into a river bank somewhere under the area where the dam got built. This either wasn’t noticed or was’t patched correctly during dam construction.

This high pressure water, injected from the hill above, would flow through the various dam fill stratums and not necessarily come out at one place or one elevation. One might assume that if a 700’ earthen dam has a maximum settlement of less than a foot (0.1%), then all the various stratums were fairly well compacted, and pressurized water might migrate between the fill layers rather than through them.

If this hypothesis is viable, then DWR’s half assed explanations may be half assed valid. The green spot is due to a local ground water “spring” or pathway that is only active when it is raining. This could help explain why some water flowing in the galleries appears to have higher organic content than might be expected from dam fill material alone.

Now DWR may not want to outright admit that spring water from the adjacent hillside occasionally flows through their dam. However, this would be an order of magnitude better than having water from the reservoir flowing through the dam, because once started, that pathway might not stop.

I think that everyone reading this forum agrees that a more through examination of this “green spot” should take place. When examining “unseen unknowns”, no plausible hypothesis should be rejected without due cause.

To ER333:

I really like your 7 step plan for conducting more through diagnostics of the cause and extent of the dam “green spot” and associated settlement (post 3554). The only way to make sure that “unseen unknowns” don’t bite you in the ass is to make them seen and get to know them.

However, more extensive dam diagnostics are not in this year’s current work plan (that we know of). But putting in some or most of the spillway is in the current work plan.

I’d like to get your thoughts on what types of diagnostic instrumentation should be included in, under, and around the spillways. The contract specs for any such instrumentation are probably just now being drawn up, so it seems such focused speculation could be timely.

My preliminary thoughts:

Any modern embedded sensor should be wedded to a microcontroller to continuously check for threshold changes and to handle communication. Temperature and acceleration are basically builtin to many embedded controllers. Pizos could be added for pressure. Acoustic microphones are simple and cheap. Flow and turbidity sensors could be added to the drain pipes. Embedded strain gauges can be temperamental and break easily, so where possible, strain and settlement might best be measured externally via terrestrial scanning Lidar or perhaps inSAR satellite. The more critical instrumentation should be accessible and replaceable for upgrades, where access should be easier in a spillway than a dam. If someone were to put together such a extendable instrumentation package, now would be the time to prototype and test it.

Better diagnostics can lead to applying an once of prevention, rather than the current pound (or a ton) of cure. What types of diagnostics should be built in to the new spillway?

Ray76’s data shows there was a 3 month period ending in August 2011 when the lake level stayed above 891’, within 10’ of topping out. This contrasts with 2017, when the lake was above 891’ for just 4 days, and has averaged closer to 850’.

Hence, there was more elevation head on the dam for a longer period in 2011 than so far in 2017. Yet the green area (apparently, as assessed by locals) is larger now than in 2011. Had this green area had stayed “green” through August 2011, correlating with the high lake levels on the opposite side of the dam, someone would have noticed and taken pictures, as you don’t get green grass in California in the summer without irrigation.

This indicates that either the internal piping through the dam has gotten much worse recently, passing a higher flow rate now under less head; or this green area is not a function of lake level, but more of a function of the extent and duration of precipitation.

To EarthResearcher333:

Thanks again for the post cross referencing your radial gate anchor tendon diagrams and putting them together in one place. These really help in gaining a better understanding the scope and scale of the issues; but do generate fodder for further questions! I’m still way down on the learning curve, but trying to catch up.

Replacing the gate anchor tendons appears to be quite a significant endeavor, as you’ve been pointing out for a while now. Besides the problems you identified in accessing the internal “Tees” from the side of the columns, and spreading the grout out enough to eliminate air voids on both sides of the sleeve, I would think there might also be difficulties with the coring out of these 37’ long tendons in the first place. The bit would have to drill through a composite of steel, grout, concrete, and rust for 37’ consistently without clogging enough to bind or break. If the grout and rust hold the tendon in tension, the compressive force reaction would substantially increase the bit’s tendency to bind. A broken or non-recoverable bit could result in a tendon that couldn’t be replaced, so there would be little room for error across the thousands of feet of coring required.

Is it a common practice to core out and replace tendons this long? How long does this take per tendon? Does the hole size increase significantly? Do you have pictures showing how this is actually done for tendons of this size?

Are there other plausible alternates for restoring the full original design safety-factor gate tension? Assuming they could find the room, could they drill new holes and grout in additional new tendons to compensate for the strength loss from the existing corroded tendons? This might strengthen the gates sufficiently until proper diagnostics could determine which of the hundreds of tendons actually need replacing, as that may not be until later this year, on DWR’s schedule. I would think DWR would need a “Plan B”, if they don’t have time to replace the tendons this year, which seems likely.

You cited a year 2000 DWR report that said two of the Oroville anchor tendons had broken. Did they replace those tendons? How do you get a broken tendon out of 37 feet of concrete?

Wow, I think we all collectively owe a debt of gratitude to EarthResearcher and other members of this forum who have collectively brought these dam issues to light! With the mainstream media now openly publishing Professor Bea’s report, it looks like the cat’s finally out of the bag.

Prof Bea appears to use many of the same pictures, diagrams, and assessments that were brought up in this forum and at Metabunk. Perhaps great minds think alike, with the rest of us just in awe. Bea’s report is light on techno-babble and heavy on pictures, so it appears configured for direct public consumption.

I had a buddy who was a infamous EECS professor at Berkeley. He got offered 50% more to move east to the Ivy League, but didn’t take it. I asked him: what motivates UCB Professors? Not money, not fame, but “impact”. I think Bea’s report was written for maximum public impact.

His paper, like much of EarthReasercher’s assessments, calls heavily on DWR’s own dam reports. It will be difficult for DWR to publicly claim: “hey, we don’t know how this happened”, when their own (now openly published) reports say otherwise in a publicly consumable format. Their next press conference may not be so cordial. If the press catches on to FCO, Hyatt, and Dam issues as well - things could get testy.

Since there were dam field engineers who recently worked on the spillway repair, one must assume they were aware of the issues. How could you look at the volume of water spurting out those drains, and not wonder: is that healthy? But these issues were most probably grandfathered in when they got hired, and they were probably told that the politics were way too FUBAR to change them.

So, thinking back to when I was a Junior Civil Engineer, eager to change the world, how would one go about it? Assuming that GPR and bore-hole camera inspection were not included in the HQ configured contract, what Q&D field test could be done assess if the drains were actually repaired functionally?

A simple minded field test would be to just fill the upstream drain vent tube with water. If it immediately came down the sidewall nozzle, then the subsurface horizontal drain tube must be OK. If it half filled, and then slowed down, you’d know there was a clog, and approximately where. If you poured in huge volumes of water, you’d know that the side drains had large under-slab voids. If you plugged the output port, creating a backup head, the water would either migrate to an adjacent drain, or perk up as wet spots through cracks in the slab. This could help identify unknown slab fissures, and/or validate various sealing efforts. This doesn’t require any extensive technology, and could have been done 50 years ago.

Question to EarthReasercher and other informed experts: why not just do simple pressure tests of spillway drains? Couldn’t they do this for the remaining spillway and/or new construction? Wouldn’t the volume/flowrates they get help validate their GPR and borehole camera based subslab flow modeling?

For the new spillway construction, and even for the sections of the old spillway that they don’t have time to replace, it would seem useful to place pressure and flow meters in each output nozzle. These could sense relative changes in flow, and perhaps turbidity, before they became visually apparent. I’d go with bluetooth enabled adriunos, which could run for a year or so off batteries, and would be simpler, cheaper, and more real-time than monitoring by camera alone.

For the new sections of spillway, wouldn’t it be worthwhile to include a bunch of embedded sensors, say pressure, flow, turbidity, temperature, and perhaps others? Many would undoubtedly fail over 50-100 years, but one could either put in a lot of redundancy, or make them accessible via access tubes for upgrade/replacement.

Are new dam installations configured for the Internet of Things? The time to add something like would be before construction begins. Sensing problems before they happen is much easier/cheaper than repairing them afterword. DWR might soon be more susceptible to informed outside input.

Assemblyman James Gallagher: “The terrorist issue is irrelevant …”
Couldn’t disagree more.
Many US citizens have been, are, and continue to be in a state of terror.
Who enabled this terror? DWR and the terror-able way they’ve handled things.
Screw up things bad enough, and people become terrorized. Therefore, terrorist legislation comes into play.

Thanks for the pictures and the diagram of the radial gates. That really helps clear up the issues that you’re bringing to our attention.

Intuitively, I would think the trunnion pins would be more of an concern then the anchors that hold it in place being as it’s an exposed moving part where the stress is concentrated versus the anchors which are encapsulated, static, and where is the stress is distributed. However, your documentation shows otherwise. It is greatly appreciated that you’re willing to share your expertise within this forum.

Perhaps this is why DWR indicated that they would be upgrading the FCO.
They can bury this work in with everything else and hope that no one will notice, or be allowed to do to security reasons. I still don’t see how they can work on the FCO until they can use Hyatt alone to get and keep the water level down below the gates, unless they’re planning on building a cofferdam, which would be quite an undertaking and in itself.