Grand Coulee Dam and Washington's Largest Earthquake

On December 14, 1872, one of the largest earthquakes ever recorded in the state of Washington occurred. Since there were no seismic recording instruments in place in those days, there is no accurate record of the actual size of this large quake. Estimates for this quake currently run as high as M7.5.

Even though this earthquake was centered east of the Cascade Mountains, damage from it was noted even west of the Cascades. Regarding this quake, a webpage linked here states that "chimneys cracked in Olympia, trees toppled in Puyallup and fissures split the ground south of Seattle." The page notes further that "windows also shattered as far away as Victoria, B.C., and people were knocked off their feet at Snoqualmie Pass."

Looking toward the north and east, a page linked here states: "People in towns as far east as Henry House, Alberta [about 340 miles away, and on the other side of the Rocky Mountains], and Virginia City, Mont. [about 450 miles away, with the Bitterroot Range between], felt the quake as a succession of mild shocks." The page notes further that at Chilliwack in British Columbia, Canada, upstream on the Fraser River [about 130 miles away, with the Cascade Mountains between], "the houses commenced to oscillate; the earth rose like waves of the sea; the rivers splashed their banks."

From the things stated above, it is very obvious that this 1872 quake, which was centered somewhere in the eastern part of Washington state, was felt over quite a large area. But, there is yet more to this story, as we consider just some of those things which occurred in the region where Grand Coulee Dam is now located.

East of the Cascades, the shaking was so severe that a giant landslide temporarily dammed the Columbia River near what is now Entiat, Washington. Looking further to the east, a webpage linked here notes that big things were happening around the Whitestone area. The original site of Whitestone is "just downstream from the mouth of the Spokane River." As a note, the original site of Whitestone is now covered over by the waters in the reservoir behind Grand Coulee Dam. The dam itself is located not very far downstream from the original site of Whitestone. So, what was happening at Whitestone during the earthquake of 1872?

An eyewitness (who is spoken about in the previous link) stated that there were 142 distinct shocks over a period of 42 days. Near Whitestone, a large crack formed in the ground. Near this area, one bank of the Columbia River "caved off and settled down for two or three hundred yards." The mountains and cliffs in the area were shaken so severely that large masses of rock were "constantly falling, tumbling and sliding down" for quite a period of time afterward. It is obvious that this was an incredibly large quake in 1872, but there is more to this story.

In 1933, just 61 years after the major earthquake had greatly affected the Whitestone area, the construction of Grand Coulee Dam began. The original construction phase for the dam lasted for a period of about 9 years, until 1942. Grand Coulee Dam is the largest facility in the United States for producing electrical power. Because of all its uses, this facility is very important to the United States and its economy.

Now, it is time to consider what was dealt with during the construction of Grand Coulee Dam. During bedrock preparations for the dam, a Washington State University Libraries webpage (linked here) notes that a deep hole had to be excavated into the bedrock so they could attempt to seal up the deep fissures beneath the dam. The page clearly notes that these deep fissures are part of a fault zone or an ancient fault line. So, it is clear that those people who were heading the dam building project knew that it was being built in a fault zone. In other words, it is clear that the dam was knowingly built in a geologic zone of weakness.

To some, it appears that this fault zone at Grand Coulee Dam may be associated with the Lewis & Clark Fault Zone. But to the writer, it appears that this fault zone may be associated with a giant cross-nation rift which extends diagonally across North America, from Georgia (in the southeast) to Washington state (in the northwest). For those desiring additional information about this giant rift, more is written about it in the writer's webpage called 'Current Expectations for a Cascadia Mega-Quake.' The rift information is found in the right-hand margin, starting at the level linked here.

So, what could be the consequences of building Grand Coulee Dam directly in a major fault zone, where things clearly moved on a rather large scale in 1872? For starters, it appears that during a massive earthquake in the region, Grand Coulee Dam could potentially fail, possibly even catastrophically, producing devastating effects downstream. If Grand Coulee Dam were to fail, the wall of water and debris could blast out the dams below it on the Columbia River, plus cause an immense amount of other damage downstream. Information regarding this matter is found on PDF page 2 of 3, of the page linked here. And, in just a bit, we will again look at the information from the linked page, but in just a little more detail.

Now, there are some who may state that there is "no active fault, known or suspected at Grand Coulee Dam." Well, if it moved in 1872, there is reason to suspect that there are faults in that area which have the potential for moving again, possibly even in the not too distant future. Furthermore, when the "pros" say that there is no active fault, known or suspected, we really should look at the history of the "pros," where they have been utterly wrong and thoroughly blindsided in earthquake events in more recent times and people have needlessly died because of it, because things were different than the "pros" computer models showed. The history of some of this type of thing is presented in various other posts in this blog.

Looking at things further, regarding the predicament of Grand Coulee Dam, there are some who are proposing a "postulated seismic failure of Grand Coulee Dam," wherein the dam would not have a catastrophic failure, but only a part of the dam structure would fail and the remaining portion of the dam would "act as a restriction or weir and minimize the hydraulic failure." Well, again, we must consider how the "pros" have been wrong at what has happened in earthquake events in recent times.

The writer, for one, has no plans of gullibly hoping for the best in this highly questionable situation and then getting utterly devastated, by thinking that there would be just a postulated seismic failure of the dam and then finding out that things are actually much different in real life than the potentially flawed computer models showed. Furthermore, there is no genuine guarantee that an earthquake even larger than the 1872 quake could not happen in the region near the dam.

Now, when it comes to Grand Coulee Dam and its potential for experiencing a catastrophic failure, rather than simply a "postulated seismic failure," there is something to look at more closely. In 2013, as found in that page linked here, there was testimony given to the Nuclear Regulatory Commission (NRC) Petition Review Board which related to the nuclear power plant on the old Hanford Nuclear Reservation site. But, on PDF page 2 of 3 in this testimony, there is some information presented which relates directly to Grand Coulee Dam.

The page of testimony clearly states: "According to the NRC's own studies, a complete dam breach at Grand Coulee, whether through earthquake or terrorist act, would send a wall of water blasting out the seven dams below it on the Columbia River..." Well, as each dam on the Columbia River below Grand Coulee was blasted out, it appears that it would add to the size of the flash flood created by the initial Grand Coulee failure. Now, at this point, there is even more to consider. Let us seriously look at what the Nuclear Regulatory Commission (NRC) was concerned about in its own studies.

The NRC was concerned about the potential for a catastrophic flood being created on the Columbia River that could possibly even affect things at the Hanford Nuclear Reservation. The NRC was concerned that a complete dam breach at Grand Coulee Dam could then allow for flash flood waters to possibly even blast out the dams below it on the Columbia River. Now, it appears that the NRC felt that such a scenario was possible, so possibly a scenario like this is something which we should take seriously and not just hope for the best and plan for only some sort of a "postulated seismic failure" to occur at Grand Coulee Dam, should a massive earthquake seriously affect the region where the dam is located.

When it comes to Grand Coulee Dam, there is another thing to consider. The "pros" are not concerned about a Cascadia earthquake affecting Grand Coulee Dam, because they are basing things off of a belief that the next Cascadia earthquake will be located far offshore in the Pacific Ocean. Well, can they guarantee that they are absolutely accurate on this one?

For those with an interest, there is information contained in other posts on this blog which give reason to suspect that the next massive Cascadia earthquake could be centered somewhere much nearer to the Cascade Mountains, rather than far offshore in the Pacific Ocean. This could possibly radically change the picture for Grand Coulee Dam.

For additional information relating to the giant cross-nation rift and Grand Coulee Dam, plus information relating to Hanford Nuclear Reservation and a Cascadia mega-quake, just scan down through the information in the whole right-hand margin of the writer's Cascadia report, which is linked here. Then, for even further information which is specifically directed at the situation surrounding Grand Coulee Dam, check out a page linked here, which page is titled The Apparent Predicament of Grand Coulee Dam. And now, let us look at just some of the highlights which are found within the linked Grand Coulee Dam page.

When they were planning on building Grand Coulee Dam, some form of geologic testing was done. Those doing the testing declared that there was solid granite rock beneath the dam site, and that is what many people and agencies still "parrot" today about that dam site. But, once the excavation of the site was well under way, after the July 1933 start date, it was found that the bedrock was quite different beneath this site. Yes, possibly there was someone who wanted the dam project to be done so badly, that they may have done a little bit of "fudging" on the initial geologic testing reports.

Once the actual excavation for the dam site was well under way, it was found that there was a series of north-trending, geologic dikes. But, that is only part of the story. It was also found that there were "several shear zones and faults" in the rock beneath the dam site. So, let us look a bit closer at what actually was found to exist beneath Grand Coulee Dam.

A 1938 report declared that there were found "three major systems of joints [which] cut the foundation granites," with "closely fractured rock resembling weakly defined shear zones," which exists beneath the dam. A couple of these major systems of joints or faults even crossed each other at virtually right-angles beneath the dam site. Well, this tends to indicate that there may be a somewhat weak geologic structure beneath the dam. So, what did they do to hide or cover up this problem?

Well, they did a lot of "overexcavation, scaling, and bolting" in this fractured bedrock. Then, the chief design engineer for the dam project spoke of "the treatment of extensive shear zones at Grand Coulee Dam by unprecedented grouting..." That's right folks, just squirt a whole bunch of grout into those messed up shear zones and expect Nature to forever cooperate with you and not go ahead and get rowdy and just shake things loose!

Now, let's summarize what the Grand Coulee page, linked further above, found that there is beneath Grand Coulee Dam. It states that there was found "faults, joints, intrusions and intrusive contacts, plus extensive shear zones in the bedrock beneath Grand Coulee Dam." Then the linked page contains the following information from a source: "For concrete dams founded on rock, sliding on discontinuities (e.g. joints, fracture zones, intrusion contacts, faults, shears, bedding, foliation, etc...) within the foundation rock mass is the leading cause of historical failures." 

Well, so much for Grand Coulee Dam! And then, there is another problem to consider, especially with all of those faults, joints, and extensive shear zones in the bedrock beneath the dam. The linked page speaks of paths of seepage developing, which can work to erode or weaken the bedrock even further, which is beneath and is supposed to be supporting the dam. And then, in the midst of all this, there is that nasty "lift seam" which is located below the dam site, which "lift seam" is explained in the linked page.

At this point, there is one very important thing to note. The linked page states that a "lift seam" can present a hazard for the dam structure, plus can "destabilize the dam's foundation," especially in the event of an earthquake. Now, in the case of Grand Coulee Dam, it appears that this "lift seam" is a rather weak or unstable, 400-foot-wide zone which is filled with clay and disintegrated granites. So, what did they do about this rather large and hazardous "lift seam" which resides beneath Grand Coulee Dam?

Well, they cleaned out as much of the loose junk as they could. Then, they jammed the seam as full of grout as they could, and then they simply hoped for the best. Possibly they also hoped that they were all dead and gone before anything serious became of this situation and people realized what they had really done, when they built the foundation for Grand Coulee Dam. Yes, it appears that in this rather unstable "lift seam" beneath the dam is where they did some of that "unprecedented grouting." And, there is a lot more to the story about Grand Coulee Dam, plus what is beneath it, some of which is revealed in that page which is again linked here.

There is another thing which should be included in this post. There is actually more to the "lift seam" problem at the Grand Coulee Dam site than just the dam itself. In the page linked above is also found the following quote from a source: "When the excavation of the pumping plant was being performed, a so-called 'lift-seam' in the rock was noted. This extensive sloping joint structure in the bedrock in the back wall of the pumping plant was viewed as a potential hazard in the event of an earthquake." 

So, it appears that there is not only a huge and potentially dangerous "lift seam" under the dam itself, which could potentially create a catastrophic problem in the event of a huge earthquake, but there is also a potentially hazardous "lift seam" in the back wall area of the large pumping plant which is located at the west end of the dam. There is reason to suspect that both of these "lift seams" could create some serious or very dangerous problems, in the event of a huge earthquake which strongly affects this area.



For further reading:

Current Expectations for a Cascadia Mega-Quake
https://cascadian.neocities.org/cascadiaquake.htm