Seattle SR-99 Tunnel: construction difficulties

The Alaskan Way Viaduct replacement tunnel, also known as the SR 99 Tunnel, is a bored highway tunnel in the city of Seattle.. The 2-mile (3.2 km), double-decker tunnel carries a section of State Route 99 under Downtown Seattle.

Construction began in July 2013 using "Bertha", at the time the world's largest-diameter tunnel boring machine. After several delays, tunnel boring was completed in April 2017, and the tunnel opened to traffic on February 4, 2019.


I find it ironic that in the 21st century it took us 5 years to complete, and 7 years to launch a 2 mile (3.2 km) tunnel. This construction time is comparable to that of:
  • Box (2.95 km, 1838-1841) - straight, and descends on a 1 in 100 gradient from its eastern end.
  • Mersey (1.2 km, 1881-1886) - Oldest and first longest underwater rail tunnels in the world, Crossing the Mersey in Liverpool
  • Severn (7.01 km, 1873-1886) - One of the oldest underwater tunnels in the world
The below two facts (pertaining to two major construction halts) could be even more ironic:
  1. Three days prior to stopping (in 2013), the machine mined through an 8-inch-steel well-casing used to help measure groundwater in 2002 around Alaskan Way, drilled as part of the planning phases of the project. Whether this pipe had anything to do with the machine's failure is at the center of legal dispute between WSDOT and the contractor, Seattle Tunnel Partners. This delay lasted for more than two years as the workers had to dig a 120-foot (37 m) vertical shaft down to Bertha's cutting head to repair it. Settling was discovered in Pioneer Square that may be related to this additional excavation.
  2. Tunnel boring had resumed on December 22, 2015. The tunnel boring was halted 23 days later on January 14, 2016, after a 30-foot-wide (9.1 m) sinkhole developed on the ground in front of the machine, causing Governor Jay Inslee to halt drilling until the contractors can perform a root cause analysis to show that the machine can be run safely. Even though contractors filled the hole with 250 cubic yards (190 m3) of material, the ground above the tunnel-boring machine continued to sink, according to the Washington State Department of Transportation.
We all can speculate on what those sinkholes could mean in a city like Seattle.


Additionally that 8 inch steel pipe mysteriously disappeared:

KD: Curious if this Seattle Tunnel saga had anything to do with possible buried buildings they had to drill through.

Funny that Brunel's 1843 tunnel looked so much cooler when completed. Sure enough it allegedly took him 18 years to build it, but he started in 1825, and built it under the Thames River.

1843_brunel Tunnel.jpg

The buried building is in blue. I have no idea what the Diller hotel has to do with it, or why it would be under the roadway in 1960s.



Goin back to the 1884 Aerial View, we get this. Our "under-roadway" structure (in 1960s) is between University and Seneca, and directly underneath the 1st Ave. The 1st Av used to be the Front Street, as far as I understand.

Whatever that thing below is, I don’t know, could be a bunch of piles, but that is the area we are questioning.


1889 Aerial View does not really have anything useful on it.


On the below 1904 Aerial View, our "under-road" structure could be one of the buildings between Seneca and University.
  • #3 - Arcade Building
    • Built in 1901-1903, the mammoth Arcade Building, with its extensions, occupied all of the 2nd Avenue westside street frontage between Union Street and Seneca Street.
      • On the below map #3 is between Union and University,
    • It stood on the northwest corner of 2nd Avenue and Seneca Street and southwest corner of 2nd Avenue and University Street.
  • Question: where is the Diller Hotel in 1904?

This is #3 - the Arcade Building

The wealth these 19th century chaps encountered and amassed is astounding. To pull it off they needed able-bodied men to produce goods, food and services-- thus the allure of fantasy-advertising and mass European immigration. Undesirable, misbehaving men, went to the Klondike for gold and later to war. Women and churches had civilizing missions. And their great-great... grandchildren, raised never to question the crimes of the day or admire too inquisitively the truth, sit in denial about the sordid corruption into which their virtuous institutions of culture have lately decayed.

And now, numbers must be reduced under civil missionary duress. Hurray! Everyone still has a part to play! Some will manage the fraud; some will be lost; and few straggly others scratch their beards and wonder.
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I actually drove there. That red older building is our Diller Hotel. The red line is going across the roadway built over the building we see on the OP photograph.


This here is the 1st Av and Seneca, which is one block south from 1st Av and University.


What you see above is the same area you see below... photographed some 50+ years prior.


Looking up at the intersection of the 1st Av and University. In front of me, behind these steps is where that "under-the road" building was (or is) at.


For whatever reason I did not snap a photo from farther West. Ended up getting a screenshot from G-Maps. That's the same older red building aka the Diller Hotel up on top.


One more time.


The Diller Hotel (red squared) opened to the public exactly one year after the fire on June 6, 1890.
  • Questions: why is there a building under the 1st Av roadway next to this Diller Hotel?
  • If the Diller Hotel was built in 1890, when was the building below the roadway built?

I think this here could be the building we see under the roadway.

But then again, if this here is our Hotel Diller on the right, where did the building under the roadway come from?

From above: 1891 Birds-eye-view


Going back to the 1904 Bird's Eye View of Seattle... the structure should be somewhere within the red square.


It looks like there was some structure underneath the roadway.


Some photo links:
The wall at 1st Avenue and Seneca is a retaining wall. Built to prevent the ground supporting the roadway from sliding down the hill towards the sea as it is want to do once the trees and their roots that were anchoring the ground were removed.
This whole area is filled with retaining walls. They are the only way to get buildings to rub up against the steep inclines.
I'm not au fait with the drawing tools in gimp but these grey dots are examples of the same walls.


These grey lines show where the retaining walls run.


The slope below the dot on the right is much steeper than the slope above it as evidenced by the trees position. This means that in that image the hill is running down right to left as we look at it and from back to front as we look at it. The steepness of the right to left is shallow compared with the steepness running back to front.
Whatever that thing below is, I don’t know, could be a bunch of piles
Been here before as I recall in this thread.
The area illustrates the problems and the probable reason for the retaining walls being so massive.
First is your positioning of the diller in the blue box and the lower one is my clumsy paint by numbers effort which illustrates what I mean,


The red line shows a natural cut or edge in the land. It has no man made supports it is just the natural 'cliff edge'.
The yellow line shows a wooden jetty made of tree trunk piles sunk into the shallows to create a level running bed for a railway.
The blue line shows a wooden piled jetty that has been back filled to create flat solid land within it.
The green line shows the Front street regrading at the point where it crosses what used to be a ravine. It is either wooden piling or brick walling.
The sloping land on the upside is a way to prevent further slippage of the upper land onto the new street,
This week’s feature on First Avenue, like last week’s on Third, looks north from Seneca Street, here a few yards south of Seneca. Imagine, if you will, in place of Seneca, a ravine. Following the 1852-3 pioneer settlement on the east side of Elliott Bay, a bridge was eventually needed to cross this gully that broke through the waterfront bluff. The Native Americans had favored the eroded cut as suitable for burials, and during pioneer days bodies were still exposed during heavy rains. In 1876 the bridge over the ravine was reinforced with a log retaining wall during the regrading of Front Street (First Avenue) from Mill Street (Yesler Way) to Pike Street. It was Seattle’s first oversized public work.
So they went from natural to log piling to brick in that area.

I do not know the veracity of the content quoted here but I include the photograph as it shows the underlying ground and the problems of building on such ground.
The intersection of Seneca and Front Street (no.5) photographed from a waterfront rebuilding after the Great Fire of June 6, 1889. The 1888 map shows a few fire-destroyed subjects including the Cracker factory (3) and the electric generating plant (4) to either side of Seneca and just west of Front/First.
Again no way to establish the veracity of the content quoted.
The best survivor here is the most distant one, the Diller Hotel at the southeast corner of University and First. A heavy cornice, since removed as an earthquake precaution, tops its four floors. The Diller developed into a popular hangout for political and fraternal huddling. Named for its builder’s family – the family home had been on the corner – the Diller was conceived before the Great Fire and built soon after of Japanese bricks. Understandably, bricks were then hard to come by.
So the hotel was up by 1890. Here it is in about 1909 with the building that would become Herbs store. The wall in the op photo is off to the right just out of shot. However I include this image as it shows the two slopes of the streets and their differing steepness. I really struggle with this grid street layout system so if I butcher it come in and correct me, please. First avenue is running right to left in the photograph ans is at a much shallower angle than University Street which is at right angles to it. The Diller is actually built on flat land as in a terrace created by the construction of the Front Street/First Avenue regrading as we see quote clearly in the photograph.


My suggestion is the roadway that is first Avenue today and Front Street back then and the land the Diller and all the buildings on the up side of the road are only there thanks to the hidden brick retaining wall.

I suggest these railings likely

Became this

railings 1926.jpg

Then became this.


Here is a photo of the Seneca Hotel from 19266 which I feel answers the op photo conundrum. I stress this is MY feeling!

Hotel Seneca 1926.jpg


As we see below above the footpath changes from concrete/paving to boardwalk right at the point of the lamppost. This suggests to me the actual retaining wall for the roadway is right underneath the gutter of the road and its kerb. The reason for the change in materials is the boardwalk is in mid air with nothing underneath it as we can see though the railings the hotel building carries on down and the railings sequence above shows the overhanging footpath extending beyond the retaining wall.
We also see the footpath is at an angle in relation to the hotel front so to accommodate the inclined footpath the hotel builders stepped their entrances up/down accordingly.
The wall of the hotel facing the street but below street level was used along with the hidden retaining wall to provide a solid 'tray' or support for a more substantial and durable footpath hence the change in material being right where the lamppost stands and most importantly the hotel building ends.

What we see in the op colour photograph is the remains of the hotel building left up to support the footpath. The cutouts in the walls are openings to allow the operators of the stores and or the hotel to have cellar facilities or 'free storage rooms' or even unlicensed accommodation or given the times of prohibition hidden liquor storage (speculation obviously) between the two walls.

Once the blue painted wall is removed I feel pretty certain we would see a brick retaining wall behind it that holds the First Avenue roadway in place.


The pale blue car is abutting the kerb of the road. Between it and the security fencing there is enough room on the footpath for the car door to open and people to get in and out as evidenced by the height of the ground the man in front of the beige car is standing on. Between the fencing and where we see where the joists/supports are resting on the wall is the remainder of the footpath. The wall we see bearing the remains of blue paint/plaster and holding the joists is the remains of the Hotel Seneca.

I went looking for the demolition date for the Hotel Seneca as its clear from the content of the colour photo that it is ongoing at the time the photo was taken. Sadly neither tineye or google reverse image search was any use and asking multiple search engines the question simply brings up loads of links that are unrelated.

This however did turn up which gives some idea of what is normally hidden from view. I cannot go direct to the linked page, legla reason in my region apparently, but you American folks can!
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@jd755, that's some great research as always. I should have been closer attention to the OP image, and can go with no building under the roadway. It does look like an external wall of a building, which in this case had to be the Seneca Hotel. I tried to find some info on it, but failed miserably.
  • Assuming the retaining wall came first, it kind of makes sense, I guess, to build a structure (Hotel Seneca) up against it.


On the above image we can clearly see that there is no space between the hotel, and the presumed retaining wall. Having that space would have justified (barely) the below windows. Some of those (in blue) appear to have been bricked in.


So, what came first, 20 feet of dirt requiring a retaining wall or the building?

P.S. As far as I remember we did not come to any conclusion on where the buildings buried underneath the Pioneer Square came from, considering that everything was destroyed by fire.
The building. In Oregon as a teen, I went to Seaside often. Right on the coast, was this building at the turn of the 20th century:


It was torn down and replaced by a cheap hotel before I ever got there.

My point is the prior people built, without undue fear of global warming or tides, right on the beach. Seattle seems to have been hit by mud. Structures like this, once encased in mud, could serve as restraining infrastructure.
Seattle seems to have been hit by mud. Structures like this, once encased in mud, could serve as restraining infrastructure.
Unfortunately we have only pictures to play with. I do share your opinion though.
My point is the prior people built, without undue fear of global warming or tides, right on the beach.
Or in the tide flats in (allegedly) 1915, like all the dry land was occupied and they had to fight for every square foot of land.


There is space between the retaining which we cannot see in the colour photo but do see in your photo of the black and white photo of the same site. The width of the pavement is the distance between the retaining wall and the hotel wall. Evidence being the change in pavement material and the presence of joists/supports in the op colour photo of the Hotel Seneca's remains.
Incidentally I too have been looking again for anything relating to the Hotel Seneca but the use of Seneca for street name buggers things up in the search engines. I wonder if it had a different name when it was first built. It was beyond the limit of the great fire but was missing on the earliest panoramic street map. Tis a conundrum to be sure.

I did find this image which shows the construction going on in Pioneer Square in 1906 which we have covered before in other threads but including it here to show the similarity with the street front in the 60s/70s and it again shows the boardwalk and gives a better idea of how far apart the hotels external wall and the retaining wall were.


Also this snippet shows that at least one of the retaining walls was built 1876. No idea if it refers to the log or brick version.

Screenshot 2021-07-11 at 17-38-39 yclip-gf-ruins-lk-se-univ-western-web-copy jpg (WEBP Image, ...jpg
There is space between the retaining which we cannot see in the colour photo but do see in your photo of the black and white photo of the same site.
Which photograph are you talking about? I'd like to see that space.
Do you have any idea where the real records are kept?
I don't think there are any records, or ever were any, unless you are talking about some special sets of data Jesuits, CIA curators and Smithsonian guardians might have.
This is the stupid story in Seaside:

In 1912, Alexandre Gilbert (1843–1932) was elected Mayor of Seaside. Gilbert was a French immigrant, a veteran of the Franco Prussian War (1870-1871). After living in San Francisco, California and Astoria, Oregon, Gilbert moved to Seaside where he had a beach cottage (built in 1885). Gilbert was a real estate developer who donated land to the City of Seaside for its one-and-a-half-mile-long Promenade, or "Prom," along the Pacific beach.

Population, 1890: 87.

No need for local records... only propaganda, connections, and payoffs?
No need for local records...
Well, methinks images like this do explain why no records exist. If there was noone to tell the story, the story will be told by those who caused all this.

While dealing with isolated incidents and occurrences, we need to remember the global picture. Individual events and occurrences can be explained. At the same time, once we get too many of those, we start running into patterns. If our history was semi-transparent, we wouldn't have enough individual incidents to start noticing patterns.
Perhaps screengrabs will help show you what my words fail to get over.

The overhang from the retaining wall is the same width as the boardwalk/pavement.
The gap between the retaining wall and the wooden uprights is the same width as the boardwalk/pavement.

Screenshot 2021-07-11 at 18-03-27 Seattle SR-99 Tunnel construction difficulties.jpg

Screenshot 2021-07-11 at 18-04-09 Seattle SR-99 Tunnel construction difficulties.jpg

This is how extra rooms were created and seemingly used as evidenced by the multiple openings in the remains of the hotel wall. The retaining wall I feel predates the hotel.
I think what you are seeing there are legit contemporary construction, concrete, and civil workers/engineers, who have created a cement surface over the windows of prior infrastructure to complete their project according to specs.
The overhang from the retaining wall is the same width as the boardwalk/pavement.
I see what you are saying, but I am not sure that overlap is an extension covering the gap. I plan on visiting the underground tour today. Will try to swing by this spot again and see what we have in that corner these days.
I think what you are seeing there are legit contemporary construction, concrete, and civil workers/engineers, who have created a cement surface over the windows of prior infrastructure to complete their project according to specs.
To each their own. Please present your evidence.

KD. If you ever get the chance have a look at this document in the flesh.
Screenshot 2021-07-11 at 18-27-32 Archives West Robert Roblee Collection of William N Bell fam...png
Will try to swing by this spot again and see what we have in that corner today.
When did the building that replaced the Hotel Seneca go up?
KD. If you ever get the chance have a look at this document in the flesh.
Will try to ask the city where this doc is kept, and whether it can be looked at.
When did the building that replaced the Hotel Seneca go up?
The question makes sense. There have to be buildings contemporary to the hotel on the same street. They couldn't take down every single one. Naturally, gotta be something to take a look at there.

As it stands, I do not see the purpose of windows covered by a sidewalk above.

We do not really know when the overlap (#1) was installed, and if it had anything to do with the gap between the old Seneca Hotel and the retaining wall. As far as I understand, that's the width of an overlap you are referring to here.

If we take the entire width of the sidewalk (#2) as a gap, I don't see such a gap anywhere in the photographs.


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