On the original alignment of the Transcontinental Railroad, about 4 miles NE of Promontory UT where the "golden spike" ceremony was held, there is a massive piece of earthwork known as the Big Fill. It is still clearly visible on aerial images at lat. 41.64115, lon. -112.47921.
The Big Fill was built in early 1869 by the Central Pacific. It took three months' work by 500 men with shovels and 250 horse-drawn carts.
Stephen Ambrose, in his excellent book about the Transcontinental Railroad, "Nothing Like It On Earth," gives the volume of the Big Fill as 10,000 cu. yd. The National Park Service, which operates the Golden Spike National Monument, uses the same figure. That yardage, according to Ambrose, was a pre-construction eyeball estimate by Leland Stanford, the president of the CP.
I got curious about the fill volume while looking at the aerial and thinking about Stanford's background. He was neither a surveyor nor an engineer. He began his career as a lawyer, and then was a wholesale grocer and a politician before going into the railroad business.
It turned out to be possible to make a rough check of the Big Fill's volume by scaling offsets from the centerline to the toe of slope on the aerial, making assumptions about the slope ratio, and synthesizing some cross sections. Here's a plan view--
Here's an example of how the sections were constructed--
This .pdf gives a larger plan view--?ÿ
I ran the calc with an assumed 1.5:1 slope and again with a 1:1 slope. I had no centerline profile, contours, or any other elevation data, so the height of the embankment was backed in from the slopes and the toe offsets as shown above. The elevations all remain unknown. But the areas of the fill sections should be reasonably accurate if the slope ratio is correct.
The 1.5:1 slope calc gives a fill volume of about 70,000 cu. yd. The 1:1 slope calc gives a fill volume of about 108,000 cu. yd.
The 1:1 slope, or something close to that, seems more likely. Both the Central Pacific and the Union Pacific built their lines as fast as they could, planning to upgrade them later as necessary. They were being paid by the mile. And backing in the 1:1 slope gives a maximum centerline fill of about 70 feet, which agrees with a figure given by the NPS, source unknown.
Of course a calc of this kind is not as accurate as a field survey, but it gives an order of magnitude. If anyone wanted to check it in the field, the embankment doesn't seem to have suffered much erosion in the past 150 years.
I would be interested in any information that others might have about the Big Fill.
Since you are a Stephen Ambrose fan have you read "Undaunted Courage"? If not, I think you would really enjoy it. I have read it twice, once by itself and the second time I read it I read the journals along with the book. There is quite a bit more information if you read their journal as you follow in the book.
I have also read "Nothing Like It in the World"?ÿand thought it was good but it had a little too much superfluous business information about the UP and the CP.?ÿ
The Ambrose book seems to me to paint a good overall picture of the Transcontinental project and politics, but if you google you can find a list of errors in the specifics that is almost shameful for someone of his background as a historian and professor.
http://cprr.org/Museum/Books/Comments-Ambrose.html
We were at the Golden Spike site on our recent trip, but didn't take the side trip to the big fill. Now I regret that.
but if you google you can find a list of errors in the specifics that is almost shameful for someone of his background as a historian and professor.
I've seen all sorts of stuff about Ambrose and his errors and agree with you. I look at his writings as "semi historical fiction", which paints the picture, or, in my case creates the movie in my mind. Once that's in place additional "boring" true historical facts can be ascertained through other means such as the Journal of L&C to substantiate/clearify errors. ???? ?ÿ
@flga-pls-2-2
Aren't all writings "semi-historical fiction"?
I like Ambrose's writing style - usually approachable enough that even someone who is not especially into history can enjoy his books. But the number of errors revealed in his books are incredible for someone who has the resources and clout to thoroughly fact-check content. As a defense, he actually made a statement to the effect that he is just telling stories in his writings...it was hard for me to take him seriously after that.
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I much prefer David McCullough for American history, even though his writing is denser. The Path Between the Seas (an entire history of the Panama Canal project) has some amazing surveying accounts, not to mention engineering marvels, and The Great Bridge is almost as good for a history of engineering feats.
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"The Path Between the Seas" Just looked at this on the nook site and bought it. $16 bucks for a ebook! Cripes. Looks like it will be worth it, thanks for the heads up. ????
We are slope staking a 10,000 yd3 dam today, that fill is much larger. I imagine math isn't Ambrose's thing.
So it looks like they were off by a factor of 10.?ÿ I read Undaunted Courage and found it to be a tough read but made it all the way through it.?ÿ I've read several other of Ambrose's books, mainly the ones about WW2 and found them to be a much better read than the one about Lewis and Clark.?ÿ
@flga-pls-2-2
You're welcome - I certainly found it worthwhile, but then again my first degree was in history.
I knew a bit about the U.S. era before reading it, but the French period was incredible to me. I had no idea how much it had blown up politics in France, or how so many of the citizens got hammered (and bankrupted) by the company's failure.
Of course, the best part was reading about the original exploratory surveys - including a level run across the entire isthmus to ensure that if the cut was made the Atlantic wouldn't drain all of its water into the Pacific, because no one was quite sure if the seas were at the same level... 😯
About 12 weeks, 60,000+ CY... so about 1000 CY a day/500 guys = 2 CY per laborer per day??ÿ I won't claim to be some great human trackhoe but I think even I could pretty easily beat those numbers.?ÿ In fact, 10,000 CY doesn't even make sense in light of this manpower and schedule.?ÿ My guess is the fill area is closer to that 100,000 CY end of things.
I drove by there last May and wish I would have gotten a photo.?ÿ Based solely on my observations, I would say your estimate is much more accurate than that historical one.
Ok help me understand- if the Height of the fill is the same in both the 1:1 model and the 1.5:1 model- wouldn??t it follow that the 1.5:1 fill contain more material? Did I not read something correctly? Not trying to be snarky or anything (I know TOTALLY out of character for me)
if the Height of the fill is the same in both
Height was NOT assumed the same.?ÿ He observed the widths, and backed in to estimated heights (profile not shown).?ÿ So a 1.5 width to 1.0 rise with a given width gives 2/3 the height of a 1:1, and therefore less material.?ÿ (Assuming he didn't use the carpenter's definition of rise/run).
@flga-pls-2-2
I haven't read "Undaunted Courage," but will check it out. Thanks for the recommendation.
It stands to reason that the journals would be of interest, and would contain background information that didn't fit neatly into the narrative. It's much the same with original PLSS notes.
That's right. If we knew for sure what slope ratio they used, we would know that both the height and the cross-section areas were correct, and that the resulting volume was also correct.
I found a railroad survey handbook dating from 1855. It mentioned 2:1 slopes, but it doesn't sound like they were used much except in very sandy soil. They also mentioned 5:4, which would be 1.25:1, and 6:5, which would be 1.20:1. Another book that I saw years ago, from the early 1900s, only mentioned 1.5:1 slopes.
I did some searching online and found the 2018 NAIP imagery (RGB at 60 cm) for Box Elder County.?ÿ I also found LIDAR data for Box Elder County and downloaded the 2 km x 2 km tile for the Big Fill as a GeoTiff file.?ÿ
I dusted off my fancy image processing software that I used to use for exploration geology projects.?ÿ I then subsetted the NAIP and LIDAR files and transformed them from UTM, Zone 12 North, meters to an LDP in U.S. Survey Ft. After checking the geo-referencing of the NAIP and LIDAR images I nudged the aerial to fit the top of the Big Fill.?ÿ After contouring the LIDAR data, I laid it over the NAIP imagery.
Using the easterly slope of the fill, I measured between contours and ended up with a 45 ft. drop in 67.5 ft.?ÿ From that the computed fill slope is 1:1.5 (rise over run).?ÿ The grade from north to south across the Big Fill is +1.8%.?ÿ My eyeball elevations at the beginning and end of the fill are 4623.2 ft. at the north end and 4637.2 ft. at the south end (YMMV).
NAIP imagery (2018) with 5-foot contours and 25-foot index contours.?ÿ The low distortion projection coordinates of the upper left of the image are 200601.25 North, 99300.25 East with pixel size of 1.5 (U.S. Survey Feet).?ÿ The LDP has an elevation scale factor of 1.000220 (using an elevation of 4600 ft.)?ÿ The first is a tiff file at the image resolution for those that want to download and geo-reference it to the upper left coordinates.?ÿ The second is a JPEG for viewing in this post.
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Here are three 3D views of the area.?ÿ Vertical exaggeration is 2.5 with first image looking from south to north, second image looking from north to south and third image is 2nd image with 5-foot contours.
~~~~~ NEVER MIND. Gene Posted the post above while I was putting this one together~~~~~
Perhaps Utah has LIDAR data available for this area. In Oregon the state Department of Geology and Mineral Industries ("DOGAMI") has gathered a lot of LIDAR data throughout the state and it's available for download free of charge.
DOGAMI Lidar page:
https://www.oregongeology.org/lidar/index.htm
The viewer zoomed to Mt Bachelor (the local ski area):
If I recall correctly,?ÿ the viewer horizontal cells are 3 feet by 3 feet and the elevations are rounded to even 1 foot increments. The download data is much more accurate and huge.?ÿ The download for this quadrangle is 1.7 gigs.
This shows how much of the state has been completed, the majority of the area being fed lands, done in conjunction with BLM/USFS:
If Utah has this information available it would solve your question if you have the software to handle LIDAR stuff
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All I can say is that if its just dirt it wont stand up on a 1:1 slope, at least around here. 1.5:1 is about as good as it gets, and thats with compaction equipment I doubt they had available when they built it.?ÿ
