Pipeline construction projects undergo a litany of research, planning, outreach and regulatory approvals. Before the first shovel of dirt is dug, a wide range of federal and state regulations impose requirements on pipeline construction operators to ensure safe design, construction and pre-operation testing for all new pipelines. The Mariner East pipeline system meets, and often exceeds, all regulations in its construction and design for safety.
Pipeline construction looks a lot like a moving assembly line, with a variety of specialized crews working along various segments of the project — referred to as spreads — simultaneously and moving across the project throughout its stages to complete each piece of the construction process.
Horizontal directional drilling
What is horizontal directional drilling?
Horizontal directional drilling (HDD) is a steerable, trenchless method of installing underground pipe in an arc along a prescribed bore path. This construction method is used to install pipelines underneath waterways, wetlands, culturally sensitive areas, congested neighborhoods and roads. The use of this method greatly minimizes surface disturbance and reduces environmental impact during construction.
Dual-pipeline pullbacks have been safely and effectively used for decades in a wide-range of infrastructure projects, including water, sewer and energy pipelines, and other underground utilities. Dual-pipeline pullbacks are used to safely install multiple pipelines at once by joining them on a common pulling head and installing them as a bundle.
Using HDD to install pipelines
Installation of a pipeline by HDD is generally accomplished in three stages. The first consists of directionally drilling a small-diameter pilot hole along a designed directional path. The second involves enlarging this pilot hole to a diameter suitable for installation of the pipeline. While the pilot hole is being drilled and enlarged to the appropriate diameter, skilled and trained pipeliners string, or lay out, the pipe to weld the pipe sections together. Once the hole is drilled to the appropriate size, the welded pipeline is installed by connecting to a swivel and pulling the pipe back through the enlarged hole.
Mariner East construction:
Environmental benefits of HDD
The use of HDD allows us to minimize impacts to the environment. In fact, of the 307 miles the Mariner East 2 project traverses in Pennsylvania, less than half an acre of wetlands, spread over 19 locations across 12 counties, will require mitigation due to our use of HDDs. Per the requirements in our permit, for every square foot of those wetlands, we have enhanced five more in existing wetland areas elsewhere, which equals more than two acres. In addition, HDD allows the pipeline to bypass culturally sensitive areas and avoid traffic disruption, and it further protects the pipeline from third-party damage.
HDD is a safe, commonly used technology; however, there are challenges associated with this construction method because of varying geology along the project footprint.
When using HDD, there is the possibility of having what is commonly referred to as an inadvertent return. An inadvertent return occurs when drilling mud finds its way to the surface through natural crevices in the geology and soil.
Drilling mud is used to lubricate the drill and prevent damage to the drill head. It consists of a mixture of natural bentonite clay and potable water. Bentonite clay is a common ingredient in many applications in our everyday lives — from cat litter and fabric softener to many skin care and beauty products.
How do we respond to an inadvertent return?
In accordance with Pennsylvania Department of Environmental Protection (DEP) regulations, Energy Transfer is required to have response plans in place at all designated HDD locations to contain the drilling mud that flows to the surface in the event of an inadvertent return. Under this comprehensive plan, we contain, remove and recycle any drilling mud that escapes during HDD activities, in close coordination with the DEP.