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 Pipeline Construction — What to Expect

Questar Gas and our contractor, Northern Pipeline (NPL) of Phoenix, AZ, are committed to completing this project safely and on schedule while minimizing as much as possible any inconvenience to local businesses and residents. To accomplish this, some work may be performed at night and on weekends. This will reduce impacts on morning and evening commutes. We will adhere to all county noise-reduction ordinances.

NPL has more than 40 years experience in 39 states building pipelines in urban settings.

For pipe buried beneath streets or highways, construction may require intermittent closures of one or more lanes of traffic. Driveways also may be occasionally blocked by excavation work, otherwise they will be plated to maintain access during business hours and at night and on weekends.

Before construction starts in front of any home or business, a representative will contact the owner or resident to discuss options for maintaining driveway access. Signs notifying the public that businesses remain open during construction are available.

To finish construction on schedule and as quickly as possible, the project is divided into sections, or "spreads." This allows multiple crews to work simultaneously at different locations. Work zones can range from a single intersection to several blocks long. At any one location the amount of time to cut pavement, install new pipe and replace asphalt can range from several days to several weeks.

The public can do its part to ensure construction proceeds safely and on time by finding alternative routes, driving carefully in construction zones and keeping children away from construction sites.

Questar Gas works closely with city and state transportation officials to ensure safety and minimize inconvenience to drivers and pedestrians. However, for public safety it may be necessary to temporarily close streets and sidewalks or restrict vehicle and pedestrian traffic. As mentioned, driveways may occasionally be blocked by excavation work. We will make every effort to keep these inconveniences as brief as possible. Your patience is appreciated.

If you have questions or concerns, do not hesitate to contact us.

Following are brief descriptions of the steps involved in pipeline removal and construction:

Locate buried utilities - The area below city streets can be a maze of underground utilities. To avoid damaging these facilities, a procedure known as potholing is used prior to trenching to identify the exact vertical and horizontal location of existing infrastructure, including the pipeline to be replaced..

Move existing utilities - Before trenching (see next step), all water and natural gas service lines that cross the existing pipe will be moved to a lower depth. This will minimize the risk of interrupting water- or gas-service to individual homes or businesses once actual construction begins.

Dig trench - After the pipe has been located and purged of gas and service lines in the trench zone moved, the pavement above the existing pipe is cut and removed. Then equipment is brought in to dig the trench. The depth of the natural gas pipeline trench will be determined by the location of the existing pipe and other utilities. As the trench is dug, the soil is loaded into trucks and hauled away for disposal in a designated landfill.

Remove old pipe - Sections of pipe to be removed are cut into lengths, lifted from the trench, loaded onto trucks and hauled away for proper disposal.

Deliver and "string" new pipe - New pipe is manufactured and inspected to ensure it meets industry and federal safety standards. Pipe sections are then delivered by truck to the construction site where they are placed end-to-end (or "strung") on skids adjacent to the trench. If necessary, a hydraulic machine bends pipe sections to fit around obstacles or conform to the direction of the trench.

Weld new pipe together and coat - Welding crews join the sections of pipe together into a continuous length. Each welded joint is visually inspected, x-rayed and then coated for protection.

Lower pipe into trench - Using one or more tractors, crews lift and then carefully lower the welded sections of pipe into the trench. Final welds are made to "tie-in" any unconnected sections.

Backfill trench - Under streets, in place of the removed soil, a mixture known as "flowable fill" is used to backfill the trench. In other areas, the original soil is replaced.

Pressure test new pipe - After it's buried and before it's put into service, the entire length of new pipe is hydrostatically tested to ensure the integrity of the system. This is done by filling the pipe with water, pressurizing the system above its maximum operating conditions and holding the pressure for a specified time. The pipe is drained, cleaned and dried before put into service.

Clean-up and restore ROW - The final step is to repair the surface over the trench. If necessary, fences or sod may also be replaced.

Directional bore - At some busy intersections, most water crossings and under I-15, instead of trenching, crews will install pipe by boring horizontally underneath the road, stream or canal. The boring machine drills a hole from one side of the road or stream. Pipe is strung on the other side and then pulled back through hole.