In part one of this series of posts, we covered the broadband launch, the start of construction in my neighborhood, the vaults and flowerpots, utility locates and dig ins, and conduit. In part two, we’re going to look at putting the conduit in the ground using horizontal directional drilling and then we’ll continue to document everything as construction moves forward. Read on to hear more about the process as the build in my neighborhood continues.
September 25 – Horizontal Directional Drilling
The bulk of the conduit installation was completed on my street last week. They still need to come back and install conduit under and across the street in a few places and install conduit in my cul-de-sac. To install the conduit, crews bored a hole through the ground then pulled the conduit back through the freshly drilled hole.
The drilling technique they’re using is known as horizontal directional drilling or simply directional boring. This technique lets crews dig a 300 to 600 foot long horizontal hole in the ground for the new conduit without having to dig trenches and tear up streets and sidewalks. This technique also lets crews minimize the damage to lawns and other landscaping. A horizontal directional drilling machine is shown in the above photo.
The word directional in the name of the technique refers to the fact that the drill head can be steered to change the direction of the hole as it’s being drilled. Crews start by planning a path for the hole. The goal is to bury the new conduit two to three feet below ground while staying at least one to two feet away from any existing utilities. While drilling the hole along the path, crews can steer the drill head up and down to avoid existing utilities or left and right to follow the contour of a sidewalk or street.
Critical to steering the drill bit around obstacles and staying on the planned path is knowing the location, depth, and orientation of the drill head during the drilling process. In the tip of the drill head is a beacon. The beacon broadcasts a radio signal which can be detected by a tracker like the one shown in the above photo.
While drilling, the drill operator sits at the controls on the drilling machine and controls the rotation and thrust of the drill bit. A tracker operator then walks along the drill path with the electronic tracker. Periodically drilling is stopped and the tracker operator locates the position, depth, and orientation of the bit. Any needed course corrections are relayed to the drill operator who steers the drill head to make the necessary corrections and drilling resumes.
The screen on the tracker is shown in the above photo. In this case, the tracker is located directly over the drill head and the depth is about five feet. The center circle in the display indicates the orientation of the drill head and consequently the direction the drill head is being steered. Like the hours on a clock, 12 is up, 3 is right, 6 is down, and 9 is left. In this case, the circular display indicates seven so the drill head is being steered down and to the left.
But what actually makes the drill head change direction? The drill operator only has three things under their control: the rotation of the drill head, the thrust or forward force of the drill head, and the amount of mud being pumped out of the tip of the drill head. None of those alone is enough to steer the drill head. The key lies in the shape of the drill head.
If you look at the photo above, you can see that the drill head is not symmetrical. It has an angled face on one side. If the operator uses thrust to push the drill head into the ground without rotating the drill head, the drill head will be deflected away from the angled face. If this bit were underground and the operator applied thrust without rotation, the drill head would be deflected up and away from the camera. Once the drill head is deflected to the desired direction, the operator applies thrust with rotation to drill the hole along the new direction.
The instructions above are from a Ditch Witch horizontal directional drilling machine’s operator’s manual. In the inset image, you can see the clock indicator from the tracker superimposed around the drill bit. You can also see the angled surface of the drill head. The dashed line arrow indicates the direction the drill head will deflect when thrust is applied without rotation.
The ability to steer the drill head and direction of the hole underground comes down to the ability to accurately determine the orientation of the drill head using the tracker, to rotate the drill head to the correct orientation, and to push the drill head forward through the ground without rotating it.
To help with the drilling process, there’s a high-pressure water jet just behind the tip of the drill head. It’s circled in blue in the above photo. High pressure water is pumped down the drill pipe and exits the drill head through this hole. The water helps to break up the soil around the drill head, serves as lubrication and coolant for the possibly hundreds of feet of rotating drill shaft in ground, and pushes the excavated material out of the drilled hole and back toward the machine operator.
After drilling is complete and the drill head emerges from the ground at its destination, it’s time to pull the conduit back through the freshly bored channel. One end of a chain with a freely rotating swivel joint is threaded through a hole in the drill head. The hole is about an inch back from the tip and is circled in red in the photo above.
The other end of the chain is connected to a fitting attached to the end of the conduit. The photo below shows the fitting mounted on the end of a piece of conduit. The drill pipe with the conduit attached is then rotated and pulled back through the bored channel toward the machine’s operator. This action pulls the conduit into the bored channel and the conduit is now buried underground with minimal disruption to surface activities.
I’ll continue to update the part two blog post with updates as work continues in my neighborhood. Lastly, I cannot thank the contractors at AEG and their subcontractors like RR Drilling LLC out of Brighton enough for explaining the process and letting me take these photos between drilling sessions. Part two continues soon!
September 26 – Even Moar Horizontal Directional Drilling
More directional boring occurred in my neighborhood today. They started pulling short runs of conduit from one side of the street to the other. They also installed conduit in the cul-de-sac on the opposite side of the street from me. Maybe they’ll install conduit in my cul-de-sac this week or the next.
October 1 – Some Boring Activity on My Cul-De-Sac!
Last Thursday I got excited! On my way out the door to leave for work, the construction crews with their horizontal directional drilling rig showed up in my cul-de-sac. While I was at work, they marked a few locations for keyholes like this one directly in front of my driveway.
They also pulled conduit a third of the way around the cul-de-sac but stopped one house over from me. They pulled two pieces of 1-1/4″ conduit and topped them off with an orange construction cone. The photo below shows the conduit. You can see the white pull tape that will be used to pull fiber through the conduit at a later point in time.
Then a surprise. I found this flowerpot directly across the street from me. It’s almost completely obscured by a neighbor’s sprinkler. It’s the first splice vault or flower pot on my street.
I’m hoping that maybe this week or the next they’ll finish pulling conduit the rest of the way around the cul-de-sac. Maybe they’ll bring in the smaller missile boring equipment to do it. We shall see. In the meantime, stay tuned!
This past week they started installing vaults and flower pots on our side of the street. Unfortunately there’s still been no progress on installing flower pots or pulling conduit the rest of the way around our cul-de-sac. It looks like they’ve skipped flower pots and conduit serving about eight houses on this side of the street.
Unlike installing the conduit, placing the fiber vaults is a manual, labor-intensive process involving good old picks and shovels. A two-person crew digs a big rectangular hole using picks and shovels as seen in the above photo.
Once the hole is dug, the splice vault is buried and the conduit previously placed in the area is pulled up through the bottom of the vault.
Finally a cover is placed on the vault (complete with the Connexion logo) and the landscaping around the vault is restored.
October 17 – Xcel Energy Locates Gas Lines
I got home last night to find that Xcel Energy located the gas lines in the cul-de-sac. I’m not sure why they didn’t do this when they did the rest of the street a few weeks ago but they’re done now. Maybe this means they’ll finish installing conduit in the cul-de-sac soon.