Contractor: Trainor Construction Company
Contract Amount: $3,117,436.70
Notice to Proceed: October 15, 2001
Contract Date July 3, 2001.
Duration: 330 calender days
Completion Date: September 10, 2002
This project will construct approx. 8,600 linear feet of various sized PVC sanitary sewer pipes, along with associated sewer appurtenances. The location of the project is from 35th Ave. and Gilpin St., to 21st Ave. and York St., generally along Gilpin Street, 29th Ave., Williams St., 26th Ave., Gaylord St. and 21st Avenue.
This project is an excellent example of the latest "trenchless" technologies being used for both storm and sanitary sewer construction and repairs. This particular project involved construction of a new sanitary sewer system that will eventually connect into an existing system in the city. The project will be completed with both open cut construction and boring technology, as detailed below. The project begins with the placement of new 45" pipe in Williams Street from 27th to 26th.
The street is completely closed during the construction, where 2-30 foot deep pits are dug at 27th and 26th streets, on Williams. Later, equipment will be placed into the pits and the 45" pipe will be pushed through the earth underground, exiting in the receiving pit at 26th street. A combination of 10 and 20 foot steel plates are used to shore up the sides of the pit.
The pit is 30 feet wide, by 50 feet long, by 30 feet deep. As the pit is dug, the 10 and 20 foot steel plates are lowered in place using the I-beam guides.
Precision caissons are drilled to insert I-beams, functioning to form the support framework of the pit perimeter walls. The caissons must form a nearly exact rectangle in the earth for the support structure to work
These beams will serve as guides for the steel plates, helping to support the earthen walls during construction. Importantly, this temporary support system is both highly functional and easy to removed As the project finishes, the plates are pulled and the pits refilled with earth.
The pits are massive and require a huge excavation effort to prepare them for the project.
Once the 30 foot depth is reached, concrete will be poured on the base to support the equipment.
The new 45" pipe that will be pushed from pit to pit is made of fiberglass/mortar. Typical cement piping corrodes from sewage, this new pipe will not.
The steel plate at the far end of the pit will serve as a guide for the round boring machine which will tunnel out the earth towards the receiving pit. The tracks on the bottom will help to guide and move the boring machine and the pipe as it is pushed into place as the excavation occurrs.
A set of trolley tracks will be laid inside the pipe up to the boring machine. These buckets will run along the tracks moving the excavated earth out of the pipe where it will be dumped by a crane, and put back on the track.
At this point, this completes the set up of the equipment, and the boring/tunneling work is ready to begin. The "sending" pit (near left corner of the picture) is where the boring machine will begin tunneling through the earth towards the "receiving" pit (upper right photo), a distance of 1 city block underground.
The boring head tunnels,30 feet below the street surface,through the earth towards the receiving pit. The excavated earth is removed from inside the pipe,one load at a time by the workers in the pipe itself. Inside, there is a small conveyor belt located behind the boring head that fills the bucket with dirt, which is trollied out to the end of the pipe to be removed. This worker has been working inside the pipe directly behind the excavation, helping to load the bucket, and when the load is ready to be removed, he climbs on top of the earth lying flat between the top of the bucket and the pipe.
Movie(384k)Come take a ride inside this pipe...
Directly on the front-left is the man who works all day inside the pipe, driving the tunneling-head on its precision course, and loading the excavated dirt into the bucket for removal. On the right is the worker who rides this bucket all day long.
Movie(576k)And enjoy :-) the ride back out. 
The heavy equipment that is used to dig both the sending and receiving pits, is used now to haul out the excavated dirt which will later be trucked to a landfill.
Once the bucket is empty, it is placed back on the trolley tracks and sent down the pipe to be filled with the next load. Notice that the worker rides the empty bucket down into the pipe to help reload another load of dirt.
Fresh air is blown into the pipe up to where the workers are located. On some projects, the workers in the pipe will be several hundred feet into the pipe, many feet underground.
Movie(688k)Section by section, hydraulic equipment slowly pushes the pipe into position following the boring/tunneling work.
While the boring slowly creates a tunnel into the earth, huge hydraulic equipment pushes the pipe, section by section, into place within the tunnel. Once one section is pushed completely into the tunnel, another one is added behind it until the new connected sections of pipe reach from the sending pit to the receiving pit.
This boring head shows the massive teeth/cutters that are needed to tunnel out the hole for the sewer pipe. Note that this piece of equipment is many feet in diameter.
This project requires constant communication between operators at both the sending and receiving pits. Here at the receiving pit an equipment operator uses the bucket to tap the shoring into a more secure position. At this point, everyone prepares for the boring head to push through the earth into the receiving pit, as this section of the project is complete.
Movie(280k) It is impressive to watch skilled operaters maneuver huge equipment with such precision.
Radio communication between the workers boring inside of the pipe and those waiting in the receiving pit is constant. Now, it is critical that nothing impedes a smooth and safe entry for the boring equipment into the receiving pit.
Movie(200k)Workers constantly groom the area, making is easier for the boring head to push through. 30 feet of extension ladders are used to climb down into the pit, while the other heavy equipment like this Bobcat is lowered via the massive crane on the street surface.
The tunneling head is just pushing through the earth into the receiving pit. Movie(800k) The moment of great expectation, this phase of the project is safely complete.
The boring head will now be turned from this position another 90 degrees. Therefore, this pit had to be big enough to turn this 20 foot piece of equipment to its new direction. Now the receiving pit becomes the sending pit, the hydraulic equipment will be installed, and the next section of boring work continues underground with the next section of this project.
With the boring equipment now in its new position, in the next sending pit (remember this was the receiving pit), the project will push forward along this next stretch of underground tunneling. The goal of this project is to connect this new system with an existing system near University Hopital. This will require many phases of work and funding, tunneling through many neighborhoods.
This is a sewer manhole that has been constructed into the pipe section that started the original sending pit. This manhole will allow human access for maintenance and repair. It will covered with a more than one hundred-pound manhole-cover, which will rest on the street surface. The remaining area around this manhole will be filled with dirt and the street surface paved over. The original sending pit will vanish under a new layer of asphalt. Like an inch-worm moves replacing the front step with the back, this project moves forward.
The original sending pit is filled and resurfaced, the receiving pit has now become the next sending pit, and now there needs to be a new receiving pit. Here you see the I-beams that have been placed in the precision caissons which will be used to support the walls of the next receiving pit after excavation.
The hydraulic equipment used to push the pipe through the ground in the new tunnel is enormous and sophisticated.
Behind this equipment, a laser is placed and aimed up through the pipe into the excavation. It is being constantly monitored by the operators inside the pipe to make sure the tunnelling work remains on its precision target.
A closer view of the laser.
The enormity of the equipment and pipe being pushed through the earth is impressive.
Now this section of the project pushes slowly towards City Park where the next phase of work is being performed. The critical issue with this next phase is that it must be complete before the Mayor's dedication of the Martin Luther King statue in June.
Once again, the enormous crane is moved to this new pit to turn the boring head. It will now be placed after a 45 degree turn positioned for the last stretch of boring work moving toward the west side of City Park.
With the boring head temporarily resting on the street surface, one can get a glimpse of the tiny work area inside this equipment, where the operator sits on the seat off of the left hand side, and drives the position of the tunneling head and excavation in front of him. Can you imagine spending all day in this? I lasted about 15 second on my trip underground.
The City of Denver's Parks and Recreation Department, in conjunction with Theaters and Arenas are building the new monument site for the Martin Luther King statue, with its impending dedication in June. One difficult aspect of the this tunneling project was that the work directly affected the area of the monument. Much coordination and effort from everyone involved was needed to get the sewer work done, so that monument could be built.
