I'm on location to document the installation of a water transmission line below two railroad tracks.
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Huge thanks to our project partners!
Owner: Crystal Clear Special Utility District
General Contractor: ACP
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Practical Construction is a YouTube series dedicated to the built environment. The show builds on the success of Practical Engineering, one of the largest engineering channels on YouTube, with more than 3 million subscribers and monthly viewership in the millions. Hosted and produced by civil engineer Grady Hillhouse, Practical Construction videos provide thoughtful and engaging explanations of how the world is built (and maintained) around us.
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Created by Grady Hillhouse
Edited by Wesley Crump
Script Editing by Ralph Crewe
Graphics by Max Moser
Music by Donovan Bullen
Some music from Epidemic Sound: http://epidemicsound.com
This is the Union Pacific RailroadâsÂ
Austin Subdivision in central Texas. Itâs a busy corridor that moves both freightÂ
and passengers north and south between Austin and San Antonio⌠But itâs mostly freight.Â
Trains run twenty-four-seven here, carrying goods like rock from nearby quarries, cement,Â
vehicles, intermodal freight, and more. So, when Crystal Clear Special Utility District wasÂ
planning a new water transmission main that would connect a booster pumping station to a new waterÂ
tower
to meet the growing demand along I-35, the biggest question was this: how do you getÂ
the line across the tracks without shutting them down and trenching across? Itâs only aboutÂ
250 feet or 76 meters from one side to the other, but this small part of a large water transmissionÂ
project takes more planning, coordination, engineering, and innovative construction thanÂ
the rest of the project combined. Maybe youâve never even wondered what it takes to moveÂ
fresh water across the distances from wh
ere itâs stored to where itâs used. But, I reallyÂ
think youâre going to find this fascinating. Crystal Clear and their general contractor,Â
ACP, invited me on-site to see it happen in real-time and document the process for you! Most of the water lines are already installed, but getting this one across these tracksÂ
is going to be a different challenge. Iâm your host, Grady Hillhouse, andÂ
this is a Practical Construction. There are actually a lot of ways to installÂ
underground utilities withou
t disrupting things at the surface, collectively known asÂ
trenchless technologies. This project is using a method called horizontal earth boring, but really,Â
itâs pretty exciting. Before any dirt gets bored, thereâs a lot that has to happen first. SoÂ
much can go wrong if an operation like this isnât carried out thoughtfully and carefully.Â
One of those risks is hitting something thatâs already buried at the site, and just aboutÂ
every subsurface utility contractor can tell horror stories abou
t what happens if a water,Â
sewer, gas, fiber optic, or telephone line is severed during construction. The right-of-wayÂ
along a railroad track is a common place to install linear utilities, because theyÂ
can just run parallel to the tracks, avoiding the complexity of dealing with multipleÂ
property owners and obstacles. The owners of all the utilities that run along these tracks haveÂ
already been out to mark their location using spray paint on the ground and flags. But,Â
thatâs not enough to m
ake sure they are avoided. Before the drill can get started, aÂ
vacuum excavation crew comes to the site to confirm their location not just along theÂ
ground, but how far each one is below it. This truck has an enormous vacuum that sucksÂ
up soil as itâs blasted loose by a pressure washer. The benefit of a vacuum excavator isÂ
that, although the water is strong enough to dislodge and excavate soil, itâs not strongÂ
enough to damage the utility lines below. Compare that to using a hydraulic excav
atorÂ
with a bucket where one wrong move could rip a pipe or cable out like a wet noodle. It alsoÂ
disturbs a lot less of the area at the surface, so this process is often called potholing.Â
Itâs a crucial step if the margins are tight when avoiding existing utilities, likeÂ
they are on this site. For each utility, the vacuum excavator locates the exactÂ
position and depth of the line so that it can be marked by a surveyor and comparedÂ
to the proposed alignment of the bore. And thereâs hardly a
ny mess once the processÂ
is done. On this site, there are lines both above and below the proposed bore, so theÂ
drilling contractor will be threading a needle. Safety is also critical, especially whenÂ
working around railroads and trains. Since this job requires people on the tracks andÂ
construction below them, thereâs a specialized crew on site who coordinates between the UnionÂ
Pacific dispatchers, train engineers, and crews on site to make sure no one gets hurt. TheyâveÂ
established a speci
fic zone along the tracks, which requires the train engineers to check inÂ
with them first before any train gets near the work. When a train is on the way, the safetyÂ
crew sounds a horn, and everyone on site stops working and gets clear of the tracks. OnceÂ
the train is past, work starts right back up. The process of horizontal earth boring, alsoÂ
known as jack-and-bore, starts with an entrance pit. Unlike some trenchless methods that canÂ
curve down and back up again from the surface, this wat
erline needs to be as straight andÂ
precise as possible. So you have to start underground. This enormous excavation isÂ
where almost all the work will happen. And, because itâs so close both to aÂ
roadway and the railroad tracks, thereâs no room to slope the sides to avoidÂ
the risk of a collapse. Instead, huge steel trench boxes are installed in the pit to shoreÂ
it up and keep it from collapsing or affecting the adjacent structures. Once the trench boxesÂ
are installed, the boring machine can
be lowered into place. And before long, itâs up and running,Â
or I guess you could say itâs down and running. In practice, horizontal earth boring is relativelyÂ
straightforward. The boring machine really only has two jobs: excavating the soil and advancingÂ
the casing pipe. For the first job, it uses a string of augers that connect to a boring head.Â
Itâs just an oversized drill bit. As the auger turns, the boring head breaks up the soil ahead ofÂ
the casing pipe, and the flights draw the cutti
ngs back toward the pit. The cutting head has wingsÂ
that open when rotated in one direction. Those wings extend just slightly beyond the edges ofÂ
the casing pipe, over-excavating the bore hole to minimize the friction of pushing the casingÂ
pipe forward. The soil cuttings from the boring are discharged from the side of the machine intoÂ
a pile in the pit. Every so often, they have to be removed. The excavator at the surface uses aÂ
clamshell bucket to scoop the cuttings out of the pit and stoc
kpile them nearby. Theyâll eventuallyÂ
be disposed of off-site or used as backfill. The machineâs second job is to advance theÂ
casing pipe into the bore. This pipe provides support to the hole to keep it from collapsingÂ
and prevent the overlying soil from shifting or settling over time. The boring machine sits onÂ
tracks. The back of the machine uses a hydraulic ram attached to a locking system that affixesÂ
to the rails. The ram provides thrust, pushing both the machine and the casing pipe fo
rwardÂ
with the tremendous force required to advance it through the ground. Newtonâs third law is inÂ
play here. To provide that thrust to the casing, the machine needs something to react against.Â
So, those tracks have been firmly concreted into the bottom of the entrance pit to make sureÂ
itâs the machine that moves and not the tracks. Of course, every contractor knows as soon as youÂ
start making good progress, itâs going to rain. Water flows downhill, and this pit is the lowestÂ
spot of grou
nd on site. But the crew doesnât let it slow them down too much. The concrete bottomÂ
in the pit helps keep things from turning into a muddy mess, and an electric pump makes prettyÂ
quick work of the water that gets in. Tarps over the top of the pit also help keep it dry, if alsoÂ
making it a little tough to film the work inside. Railroad operators are rightly strict aboutÂ
the what, where, when, and why when it comes to construction on their rights-of-way. DisruptingÂ
the movement of freight an
d passengers is simply not an option. So an essential part of thisÂ
operation is continuous monitoring to make sure the boring is not affecting the tracksÂ
above. A surveying crew comes to the site every six hours to carefully measure for anyÂ
changes in elevation along the tracks. Theyâve installed these reflective markers and useÂ
a piece of equipment called a total station that can precisely pinpoint each length of theÂ
rail. They process the data as it comes in and compare it to the baseline
measurements.Â
If they notice any settling or movement, everything would have to stop (but,Â
spoiler alert, they never did). Another requirement from the railroad isÂ
that this work happens nonstop. They donât want an open excavation sitting idle belowÂ
the tracks, so they require that the boring happen continuously night and day. The longer itÂ
takes to get this casing pipe to the other side, the more opportunity for something to go wrong.Â
The boring contractor works in double shifts. When on
e crew leaves, thereâs already another one toÂ
take their place, so the site is never unattended. Once one segment of casing pipe is pushedÂ
as far as it can go, the boring machine is pulled to the back of the pit. A new segmentÂ
of pipe is collected from the stack. And, itâs lowered in. The next length of the augerÂ
is already inside. The auger is attached to the string. And then the casing segmentÂ
is welded to the end of the previous one. Segments go in faster at first, but each one takesÂ
a
little bit longer than the last. Thatâs because, every two or three segments, they have toÂ
check and make sure the bore is following the right path. There are utilities to avoid,Â
dimensional tolerances from the railroad, and location requirements from the engineer andÂ
property easements. So, having the alignment wander is not an option. Every so often, theÂ
crew has to remove the entire auger string from the bore to make sure itâs headed in the rightÂ
direction. The way they do it might unner
ve you, especially if youâre claustrophobic: they justÂ
send a worker on a skateboard to the end of the casing pipe. There are more sophisticated tools,Â
but some contractors prefer the old-school, reliable method, and they have a slew ofÂ
safety measures in place as required by OSHA, including ventilation, communication,Â
and safety spotters. The person inside the pipe uses a rule to check for anyÂ
deviations in grade from the precision laser installed in the bore pit. But, whatÂ
happens if the
bore gets off alignment? Horizontal earth boring is not a very âsteerableâÂ
operation, but there is some opportunity to make corrections if theyâre needed. Take a lookÂ
back at the first length of the casing pipe. Notice the shoes cut from each quadrant ofÂ
the pipe. If the bore starts to deviate, a hydraulic jack can be used to bend oneÂ
or more of the shoes outward and deflect the operation back into alignment. Youâre notÂ
going to turn a corner this way, but it gives some control over alignm
ent and grade. ItâsÂ
why itâs so critical that the first length of casing pipe be installed perfectly; all theÂ
rest of the casing will follow right behind it. The operation runs night and day. The machineÂ
bores and pushes each length of casing pipe. Soil is removed from the bore and then theÂ
pit. Alignment is checked. The auger string is re-inserted. A new length of casing isÂ
welded on. Rinse and repeat. All the while, trains are running constantly back and forthÂ
along this busy corridor. W
hen the drilling crew starts getting toward the end of the line, anÂ
excavator arrives to dig the receiving pit. And, after just about a week of boring 24/7, theÂ
cutter breaks through on the other side. Even the guys who do this every day gathered aroundÂ
to watch it happen. Itâs a perfect sight, especially for the fact that they brokeÂ
through in the exact spot they were aiming for. Only a few days later, it was time to pushÂ
the water pipe through. The casingâs job is just to hold the bore op
en, but the water willÂ
run in rated plastic pressure pipe. These pipes connect using a bell-and-spigot design; theyÂ
literally push together. A fiberglass rod is hammered into a groove around the inside of theÂ
spigot to lock each segment together. Spacers are installed to hold the line up off the casingÂ
to keep it from rubbing during installation or being damaged over time. Just like the boring, theÂ
pipes are lowered into the entrance pit, attached, and pushed through to the other side (alth
ough,Â
this operation goes quite a bit faster). In some projects, the annular space between the casingÂ
and pipe is grouted in, but in this job they opted to keep the space open. It was a ton of work andÂ
coordination to get this line under the railroad, so if it ever breaks or leaks, Crystal ClearÂ
will be able to pull it out and repair or replace it. This line will be tied into the pipesÂ
already installed on either side of the bore, leak-tested, and backfilled, but the hard partÂ
is over. It
wonât be long before itâs pressurized and put into service, moving fresh water toÂ
this quickly growing area in central Texas, quietly and invisibly meeting a crucial need. AndÂ
not a single train was delayed while it went in. One of the coolest parts of the project was theÂ
surveying involved. From the initial layout of the bore to the track monitoring surveys that happenedÂ
every six hours, there were so many surveyors involved in just this one part of the project.Â
Iâve said it before that su
rveying is such a cool engineering-adjacent career, especially if youÂ
donât like sitting behind a desk. But thereâs a barrier to entry that I think scares a lot ofÂ
people away from it, and thatâs trigonometry. But trig really isnât that scary, especially ifÂ
you approach it like todayâs sponsor, Brilliant. Brilliantâs been sponsoring PracticalÂ
Engineering videos for six years now. Itâs the longest partnership Iâve had. And IÂ
think the biggest reason for that is people watching this channel j
ust keep finding valueÂ
in learning new things in this interactive way. That and they keep adding new lessons everyÂ
month. I took a look at their trigonometry section for this video, and ended up finishing theÂ
entire thing, just from the joy of brushing up. We learn best not by readingÂ
or hearing but by doing, and thatâs why I love Brilliant. The lessonsÂ
just stick better when youâre actually using the information while you learn. You canÂ
try this completely free for 30 days and see if itâs
something that can help you getÂ
ahead in your career, get better at a hobby, or just enjoy the process of learningÂ
something new. The first 200 to sign up will get 20% off a premium subscription.Â
Go to brilliant.org/PracticalEngineering or just click the link in the descriptionÂ
below. I really like their website and their app and I think you will too. Thank youÂ
for watching, and let me know what you think. Huge thanks to Crystal ClearÂ
Special Utility District,  ACP, and their subcontracto
rsÂ
for having me on their site.
Comments
Thanks again, Crystal Clear SUD and AGP for having me on site. How are you liking the construction videos? đĄ Don't forget to give Brilliant a shot at https://brilliant.org/PracticalEngineering
I love the fact that you have achieved enough recognition that companies are coming to you for you to cover their project.
Watching that drill come out exactly where itâs supposed to has to be an incredible feeling for everyone working there!
"Of course every contractor knows as soon as he starts making good progress it's gonna rain!" Truer words have never been spoken... đ¤
5:26 "Horizontal Earth boring is relatively straight forward" đ
I hope more contractors reach out to you to have you do these types of videos. This is the type of stuff missing from our modern education system.
Iâm a Hydrovac operator, Iâm glad people get to see what we do in this video. I always have to explain to people not in the industry what I do and they always seem shocked that such a thing exists.
It's a good day when you get a new Practical Engineering video
As someone who manages the design of projects exactly like this for railroads across the country, I can say that this video is packed with a ton of information. This was such a good example to use to highlight all the considerations, systems, and techniques that make up a construction project like this.
I work at a power plant that used to be coal fired but switched to natural gas. Getting the pipe line there was amazing. It had to go under a subyard, under a river, up through a side of a mountain & pop up in a field a long way off. The drill bit came out within 1 ft of where they planned. I was amazed how they were able to do that! I get worried when I have to drill through a wall hoping I come out on the other side in the right spot.
I used to do this for a living and you did a good job of covering all of the tasks involved without over or under explaining it. Keep up the high quality videos.
The importance of coordination between construction workers and railroad operators can not be overstated. Last April in the Netherlands, a freight train and intercity crashed into a crane that was inexplicably crossing the tracks, killing the crane operator and injuring thirty people
OOH! Practical Construction AND Railroads?! Sweet. As always with your videos, I learned answers to questions I would never even have imagined. Also, even though I'm 63, big machines are always a pleasure to watch. It brings me back to when I was a small kid in the 1960s and Interstate 94 was slammed through the part of St. Paul where I lived. The corridor for the freeway ran parallel to the street I lived on and was only 4 blocks from my house. My many brothers and I spent loads of time watching the coordinated process over two years. (We were excited and fascinated, and of course were unaware of the controversy about building these blocks-wide barriers right through the poorest neighborhoods of cities across the whole country.) A few years later, Richard Scarry's 'Cars and Trucks and Things That Go' came out, and even though I was a bit old for it (I was nine at the time), I loved reading it to the boys I babysat on the other side of my block, and still loved it decades later when I'd read it with my own boy. Your videos give me the same sense of wonder -- and fun! -- at the design, engineering, and building of large things. And your camera work on these construction projects, from wide shots with a drone to cameras dropping into water-dug pits, is fantastic!
After getting my âPracticalâ fix, I have to admit I used to ask why there are so many people on sites like this. Not after Gradyâs last bunch of videos. Thanks to you Grady and Crystal Clear for making this happen
As a surveyor, Iâd love to see more videos promoting such a technological profession
I am a surveyor from Ukraine, currently working for a company from San Francisco. Very interesting video!
12:15 looks like some workers signed the water pipe before inserting. That's cute :) It's a fun thought, thinking that below earth, there are tons of signatures from workers installing critical infrastructure ^_^
I'm always excited to watch a boring video from Practical Engineering!
Those vacuum excavators are very cool. Last year we had a utility pole come down and need to be replaced. The ellectric company used a vacuum excavator to dig the hole for the new pole. Super fast and extremely tidy!
In my youth I did a lot of this for AT&T pushing pipe with a pneumatic driver. Rail roads were very controlled jobs. Thanks for bringing back the memories.