How did they do that? Part II Replacing water mains by excavation

UPDATE May 18, 2020 – Three weeks ago we began to reveal what's going on behind the scenes of New Rockford's water main replacement project.

For Part II of our series, we caught up with Jeff Douty of Interstate Engineering, who helped break down the current progress of the project and explain how they unearth the old water lines and install new ones using excavation.

First they have to indicate where they are going to start digging by marking it in between two white lines. In these white lines is where they will begin the Milling Process. Initially you might think that they begin digging straight into the asphalt, but this would be difficult as it would come out in chunks and would make the process a lot more complicated and messy. To avoid this they use a milling machine, which essentially has a drum with teeth that grinds up the asphalt. This gives them a cleaner cut on the asphalt and makes a corridor in which construction can safely take place.

Next an excavator is used to begin the Digging Process. The ground up asphalt and gravel is taken from the marked construction corridor and dumped on the side parallel to it. This creates an 8 foot trench from which the workers can locate the old pipelines.

Once everything is dug up, they begin the Removal Process. A safety trench box is aligned over the pipe. This allows workers to safely enter the trench and detach the old rusted pipes from their connection. It also prevents any collapse of the ground for the workers' safety. The workers then exit the trench, and the safety trench box is moved to allow the excavator to remove the pipe.

After this in the Replacement Process, the new blue PVC pipe is prepared and attached to the excavator before being safely lowered into the trench. The trench box is again moved over the new pipe and connected by the workers, ensuring that everything is in its place.

Next, two Wackers, or jumping jacks, are used to smooth the ground beneath the pipe and create a flatbed. A Wacker is a term used in construction that refers to equipment used to compact the soil underneath the pipe using vibrating plates. Once the ground is compacted underneath, the excavator then takes pea rock from the sandbox and begins to pour it on top of the pipe.

Lastly, while the workers are continuing the pipe replacements, another worker then packs gravel from the spoil pile on top of the pea rock in the Restoration Process. During this process they slowly implement material back into the trench. They then use a Sheepsfoot. No not an actual sheep's foot, but rather a machine with a drum covered in metal squares that helps compact the soil. The drum vibrates like the Wacker but has a more powerful effect that helps compact the soil at more intense levels. The worker transfers from one machine to the other, placing soil one foot at a time and using the sheepsfoot until the trench is completely covered.

As of press time, crews were installing pipe on Central Avenue from Eighth Street to 11th Street. Next they will move one block over to First Avenue North. Once the pipe is in place on Central Avenue, they will conduct pressure tests and bacterial tests to ensure the new main is ready to put into service. Then they will go back and connect the service lines for all the homes and businesses onto the new main.

New asphalt is said to come in during the summer to be placed upon the finished roads. Until then it might be a little bumpy, so make sure to drive slowly through these areas.

For up to date information on where crews are working and what you might encounter on those streets, please go to http://www.interstateeng.com/newrockford/. The interactive map highlights the progress throughout the city and alerts residents and travelers as to where activity is imminent or already underway.