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.
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 design these wastewater pipelines, we must first survey the river. These surveys will collect information about the bottom of the river. Bathymetric surveys measure the riverbed elevations, or how high and low the bottom of the river and river banks are. We also take samples of the rock beneath the river. These surveys are called geotechnical investigations. The video below illustrates how these surveys work.
To install these wastewater pipelines, we are using a construction technique called horizontal directional drilling or HDD.
The video below illustrates the HDD process.
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.
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 video below provides a comprehensive overview of the HDD construction process.
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