A pipeline construction project looks like a moving assembly line. A large project typically is broken into manageable lengths called “spreads,” and utilizes highly specialized and qualified workgroups. Each spread is composed of various crews, each with its own responsibilities. As one crew completes its work, the next crew moves into position to complete its piece of the construction process.
After Great Basin Gas Transmission Company (Great Basin) has received authorization from the FERC, as well as all necessary permits and easements, construction would proceed as follows:
- Pre-construction survey
Before construction begins, utility lines and agricultural drainages are located and marked to prevent accidental damage during pipeline construction. Next, the pipeline’s centerline and the exterior right of way boundaries are staked. Any sensitive areas that require special procedures are also identified and clearly staked.
- Clearing and grading
The pipeline right of way is cleared of vegetation and smoothed. Temporary erosion control measures are installed prior to any earth-moving activities.
In agricultural and residential areas, topsoil is removed from the work area and stockpiled separately. Crews use backhoes or trenching machines to excavate a pipeline trench. The soil that is excavated during ditching operations is temporarily stockpiled on the non-working side of the trench.
- Pipe stringing
Individual joints of pipe are strung along the right of way adjacent to the excavated ditch and arranged so they are accessible to construction personnel. A mechanical pipe-bending machine bends individual joints of pipe to the desired angle at locations where there are significant changes in the natural ground contours or where the pipeline route changes direction.
- Welding and coating pipe
After the stringing and bending are complete, the pipe sections are aligned, welded together, and placed on temporary supports along the edge of the trench. All welds are then visually and radiographically inspected. Although pipeline joints are coated for corrosion protection prior to shipping to the construction site, the welded joint areas must be coated in the field after the weld has passed inspection. Prior to the final inspection, the entire pipeline coating is electronically inspected to locate and repair any coating faults or voids.
- Lowering pipe in and backfilling
The pipe assembly is carefully lowered into the trench by side-boom tractors. The pipeline is protected on top and bottom by sand or other approved bedding material. The trench is backfilled using a backfilling or bladed equipment; no large rocks or unnatural materials are permitted in the trench.
After backfilling, the pipeline is hydrostatically tested following federal regulations. Test water is obtained and disposed of in accordance with applicable federal, state and local regulations.
Great Basin's policy is to clean up and restore the work area as soon as possible. After the pipeline is backfilled and tested, disturbed areas are restored as close as possible to their original contours. The construction right-of-way is reseeded with the same mix of vegetation that existed before grading began (except for agricultural lands). Restoration measures are maintained until the area is restored, as closely as possible, to its original condition.
Special Land Considerations
Land disturbed during the construction period will be returned to as close to original condition as possible. Agricultural lands will be properly restored using approved, modern mitigation techniques designed to ensure full productive reuse of the agricultural lands. Landowners are encouraged to be active participants throughout all phases of the project.
All mitigation techniques used throughout the project will be completed by, and at the expense of, Great Basin. It will be the day-to-day job of the project’s assigned inspectors to monitor and supervise construction and restoration activity for compliance with approved agricultural right-of-way standards relative to the region, as well as all relevant FERC standards.
A right-of-way agreement allows for the use of a portion of your land for locating our pipeline. Landowners are offered financial compensation in exchange for granting a permanent easement to Great Basin. It is important for all landowners to know that the FERC will require compliance with a comprehensive mitigation plan for all land uses, particularly agricultural lands, and will enforce compliance with that plan as part of its ongoing inspection of the construction and restoration activities.
The first essential part of right-of-way “clearing” in farmland areas involves removing the topsoil from the right-of-way. If the topsoil is not fully removed prior to construction, it may be permanently damaged by the pipeline work, due to rutting, compaction, and the inversion and mixing of the soil layers. To avoid this, the topsoil is stripped and stored safely. It must be segregated and stockpiled away from the pipeline trench, the excavated spoil, the pipe assembly area and the traffic zone. The full thickness of the topsoil zone is typically twelve inches.
Decompaction & Rock Removal
Because the topsoil is removed and stockpiled for protection, the exposed subsoil serves as the surface of the construction roadway for the duration of the project. This traffic can heavily compact the subsoil. Great Basin’s environmental inspector will test the subsoil to measure compaction. Severely compacted areas will be plowed with a paraplow. In areas where the topsoil has been segregated, the subsoil will be plowed before replacing the segregated topsoil.
Crews will remove excess rock from at least the top 12 inches of soil in all agricultural areas. Once construction is complete, the size, density and distribution of rock within the pipeline work area will be restored to the same consistency as areas not affected by construction.
Coordinating with Appropriate Agencies
Great Basin will coordinate with appropriate local, state and federal agencies any construction and restoration. This will include working with local soil conservation authorities or land management agencies to address erosion control and revegetation. Great Basin will also work with appropriate agencies to create specific procedures to prevent the introduction or spread of noxious weeds or soil pests resulting from pipeline construction.
As soon as backfill operations are complete, crews will commence cleanup and restoration activities, including completion of final grading and topsoil replacement. The construction easement will be graded to restore preconstruction contours. The environmental inspector will oversee that the restoration of contours and topsoil are returned to their original condition.