Utility companies supply electricity through various types of transmission circuits, such as underground, overhead and undersea systems. While building out these connections, utilities face several challenges; identifying risks is essential to successful project completion. Laying cables underground comes with unique challenges and risks, but they can be mitigated by adopting a proactive approach toward risk management.

Although risks can arise at any stage of the project, the initial stages are the most influential time to mitigate these risks. Identifying potential risks during the design, engineering and planning phases can help reduce their impact during construction. It is important to consider the various stages of a project, activities undertaken during each stage, and opportunities for risk assessment and management within each.

Routing stage: At this stage of the project it is crucial to identify a route, or series of routes, that satisfy the project need, but also create a constructable and permittable route. During routing, many will favor a high-level or desktop approach. While this involves a lower initial investment in the project, there may still be looming challenges that are not captured as constraints or routing criteria. One of the most effective ways to identify these potential challenges is through thorough field investigations.

This generally involves a survey of the routes. While there are various levels of surveys that can be completed at these early stages, it is recommended that existing utility data is collected, along with parcel limits. This survey aids in identifying existing constraints such as crossings (roads, railroad tracks and water bodies), potential easements or land acquisition areas, subsurface utilities and available public rights-of-way. After this data is acquired, the routing process can proceed and risk mitigation through design begins.

Having this data helps in selecting a route that will reduce the likelihood of third-party utility relocations, as well as avoiding any fragile assets that would be at higher risk of damage during construction.

Design stage: As the project life cycle progresses to engineering and detailed design, again there are opportunities to mitigate risks. During this phase, several critical steps can help mitigate risks. Many of these steps involve continuing field investigations. Performing additional surveys, acquiring geotechnical data and performing site walk-downs will aid in this process. This data helps in selecting accurate cable and duct bank size, understanding of existing utilities that must be avoided, and the impacts the soil conditions might have on construction.

One key component of risk mitigation during detailed design is identifying appropriate splice vault locations along the route. Understanding the cable's limitations for pulling is crucial to managing the risk of cable damage during installation and the flexibility for splice vault locations. This can reduce construction impacts and avoid subsurface utility conflicts.

If the project incorporates both overhead and underground components, that can introduce seams in the design process. It is important to have continual coordination and experienced designers developing this structure. Understanding the electrical phasing, orientation and clearances for these structures is critical to the design process.

Procurement stage: It is important to identify any lingering project-specific risks, assess their likelihood, assign a responsible party and develop contingency plans. Identified risks can be eliminated, mitigated or assigned to other parties during this process. One example of a risk that is transferred may be dewatering. If the owner chooses to place that risk on the civil contractor, then the civil construction prices might be higher, but the owner has reduced its potential exposure to additional dewatering costs.

Additional steps besides risk transfer can be taken during the procurement process to mitigate risks. By appropriately identifying and assessing the potential risks, the project is now in a position to allocate funds for managing those risks. This planning and evaluation process is intended to not inflate the overall project cost, but to provide adequate funding to address the risk, should it occur.

Construction stage: Progressing to the construction phase does not mean that risk mitigation ends. During construction mechanisms can still be employed to mitigate risks. One cornerstone of risk mitigation during construction is quality assurance/quality control (QA/QC) during field operations. By employing a robust construction QA/QC program, many of the remaining risks can be mitigated. One great example of a risk in many underground transmission projects is the fact that often there are separate civil and electrical contractors building the cable system installation. By having a robust QA/QC program in place, the project can see that these seams are better managed and that risks such as schedule delays and rework are avoided.

Additionally, hiring qualified vendors and contractors can help efficiently execute a project and minimize the impact of identified risks. Safety goes hand in hand with the vendor’s capabilities. Developing and executing a thorough, project-specific safety plan and adhering to safety best practices can drastically reduce risks pertaining to safety of on-site workers, project delays and costly mishaps.

Underground transmission projects have different technical and nontechnical requirements than overhead transmission projects; such projects have different design, procurement and construction constraints. Experience helps in preparing the most suitable designs and sets up the project to avoid, mitigate, transfer or manage risks.

 

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Nathan Rochel, PE, P.Eng, leads underground transmission work for Burns & McDonnell. His experience spans a full spectrum of unique and challenging projects both domestically and internationally.