Construction Process

The purpose of these guidelines is to describe the process used by Vermont Gas in constructing a pipeline on both private property and established corridors. Our goal is to ensure we work closely with each landowner, explain our process clearly, answer any questions you may have, and minimize the impact on you and your land.

Step 1: Land Survey

• A crew of one or two qualified surveyors will conduct a survey of your land.
• As part of the survey, they’ll mark the outer limits of the pipeline construction corridor with stakes and flags using a GPS or transit to ensure they mark the precise boundaries of the project. The crew will also mark trees that need to be cleared.
• The team will also mark any additional temporary workspace needed for construction • TIMING: The land survey takes up to one day, depending on the size of the property.

Step 2: Environmental Survey

• Within a few days of your land survey, an environmental crew will come to the construction area.
• As part of the environmental survey, they’ll mark waterways, wetlands, and other areas that need to be protected using special flags. They’ll also survey for the presence of invasive and rare plant species.
• TIMING: The environmental survey takes one day. After the environmental survey, the corridor is ready for the construction team

Step 3: Work Space Clearing

• If necessary, a crew will come to the construction area to remove trees to clear the work corridor.
• In some wetland areas, the crew may lay down timber mats to protect underlying areas.
• The crew will return with a wood chipper several days later to remove downed trees, chip limbs, and clean the area.
• TIMING: The process of clearing the space and placing protective matting takes up to several days, depending on the size of the property. The wood chipping process takes about one day. After the workspace is cleared, there will likely be a several week window before trenching begins and the pipe arrives.

Step 4: Pipe Staging, Welding and Trenching

• The survey crew will return to the construction corridor and mark the centerline where the pipe will lay.
• The construction crew will then carefully strip the topsoil from the work area and store it on the edge of the corridor.
• Pipe is delivered to the construction site in 60-foot sections and staged along the corridor.
• After the pipe is staged along the corridor, the trench is excavated using either a back hoe or trenching machine. The trench is excavated to the required depth to allow for the correct cover over the pipe depth, typically 36 to 48 inches.
• The pipe is welded together. Pipe welds are visually inspected multiple times and then x-rayed to ensure the integrity of the welds.
• After the weld inspection process, the joint is treated with a coating to further protect the integrity of the pipe.
• TIMING: Up to 600 feet of pipe can be installed in a day, depending on weather like heavy rain and land conditions like encountering ledge.

Step 5: Replanting

• Once the pipe has been installed and inspected, the crew covers the pipe with dirt and tops it with the original preserved topsoil.
• The crew will also grade the dirt and hydro-seed the topsoil.
• The crew will return periodically to check on the progress of the grass recovery and reseed as necessary.

Step 6: Post Construction Safety Check

• After pipeline construction is complete, Vermont Gas personnel conduct regular safety checks.
• An in-line testing device is also sent down the pipe, moved along by the flow of the gas, to verify the internal condition of the pipe. This testing is typically done on a seven-year cycle.

Special Conditions

Blasting

• In areas where rock excavation is  required, removal of the rock may  require limited blasting. All blasting  will be in accordance with the approved plan, which requires notification to  nearby residents, businesses, and municipalities.
• Pre- and post-blast surveys are conducted for water wells, septic systems, and buildings within a 600’ radius of the site. A seismic recorder will be placed at the edge of the blasting perimeter or the nearest structure within the blasting zone.

Agricultural Settings

• 48 inches of cover is provided above the  pipe in agricultural fields.

Horizontal Directional Drilling

• Horizontal directional drilling (HDD) is a method of installing pipelines and is used specifically in environmentally sensitive areas or to cross bodies of water. The use of HDD technology allows for  installation through sensitive areas without  surface disturbance.
• A machine drills underneath the feature in an arc from one side to the other to create the bore path. The bore path is then cleaned by a back-reaming tool to the required diameter for the pipe.
• The pipe is placed on rollers and welded on the far side of the feature and then pulled into the borehole by the HDD device.