Wastewater Pipeline Installation Process

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For Charlotte Water to provide wastewater treatment services for the Cities of Mount Holly and Belmont, wastewater from these cities must be transported to local pump stations and then pumped through wastewater pipes (also called force main pipes) that connect to the Charlotte Water collection and treatment system.

Force Main Labeled

The future Mount Holly and Belmont pump stations will be connected to the Charlotte Water collection and treatment system by wastewater pipelines that will be located deep underground in bedrock that is approximately 65 to 75 feet below the Catawba River and Long Creek, which is approximately the height of a 6-story building.

The Stowe Project is installing wastewater pipelines under the Catawba River and Long Creek in three locations to provide system connectivity. To install these wastewater pipelines, we are using a construction technique called horizontal directional drilling or HDD.

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We are using an industrial plastic pipe called High-Density Polyethylene (HDPE) Pipe for the Stowe Project. The HDPE Pipe will be transported to the construction site in sections and heat will be used to fuse the sections together to form one long continuous pipe. After the HDPE pipe is fused together, it will go through a rigorous inspection and be pressure tested for leaks before installation begins. Once the HDPE pipe has passed this rigorous inspection, it will be inserted at one end and pulled through the underground tunnel until it reaches the tunnel’s exit site.

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After installation, the wastewater pipelines will be inspected, and pressure tested again before it is put into use. Once in use, the wastewater pipelines will be continuously monitored by Charlotte Water. We are using horizontal directional drilling to install the wastewater pipelines, because HDD is a safe, industry-preferred way to install pipelines under water because there is minimal ground disturbance.

The Stowe Project is installing wastewater pipelines under the Catawba River and Long Creek in three locations to provide system connectivity. To install these wastewater pipelines, we are using a construction technique called horizontal directional drilling or HDD.

Frequently Asked Questions

Where are we in the wastewater pipeline installation process?

  1. Pilot Hole Drilling: an electric drill controlled by highly skilled technicians bores a tunnel along a predetermined path from the entry site to the exit site.
  2. Reaming: Once the pilot hole tunnel has been bored, the reaming process begins. During this step, reamers that have successively larger diameters are pulled through the bored tunnel to further evacuate it. Multiple passes with reamers of increasing diameters are completed until the bored tunnel is approximately 12 inches wider than the wastewater pipe that will go through it.
  3. Pipe Assembly & Pull Back: Once the bored tunnel is approximately 12 inches wider than the HDPE pipe that will go through it, the pipeline assembly and pull back process will begin. The HDPE Pipe is transported in section to the construction site and then the sections are welded together by specifically-trained and certified contractors to form one long continuous pipe. After the HDPE pipe is assembled, it goes through a rigorous inspection and be pressure tested for leaks before installation begins. Once the inspection is completed, the pipe pull back process begins. During this step, the fabricated HDPE pipe is inserted at entry point and pulled through the bored tunnel to the exit site. After the pipe pull back is complete, additional testing and inspections will be completed before the pipe is put into use and continuously monitored by Charlotte Water.

Currently, we have completed the pilot hole drilling phase and when are in the reaming phase of the installation phase as you can see from the interactive tracker above.