October 2015 Vol. 70 No. 10
Editor's Log
Seeking Solutions For Undergrounding Electric Transmission
by Robert Carpenter, Editor-in-Chief
Recently, I was honored to be asked by the Electric Power Research Institute (EPRI) to participate as one of about 40 industry members in a special workshop. The title of the event, Reducing Cost of Construction Underground Transmission Lines, is obviously an extremely important subject for the underground utility construction market.
At this workshop, experts from around the country were asked to provide presentations on specific subjects, ask questions and brainstorm in breakout sessions. The purpose was to develop research directions to expedite and facilitate the growing trend of placing transmission power lines underground.
Electric distribution lines have been going underground at a rapid pace for years. The current build-out of the electric grid has clearly demonstrated the cost-effectiveness of placing electric distribution conduit underground in a safer, cleaner and more practical environment. Modern construction methods, such as HDD combined with increasing environmental and public pressures, have led utilities to explore undergrounding options and frequently, they are shocked by the competitive price tag and much improved results – not to mention tremendously improved community relations.
Some areas have actually removed their unsightly poles from neighborhoods. Of course, at that point it becomes a financial consideration as frequently other utilities, such as telephone and cable companies, may be renting space on the pole system.
But overhead transmission power lines and their massive tower infrastructure has historically been viewed as a bastion of stability for overhead design and construction as many complicating factors and high costs effectively blocked any major impetus for undergrounding. Subsequently, placing power transmission lines underground is commonly viewed as a decision of last resort.
The thermal limitations and requirements of the massive transmission cables combined with size and weight issues have always tended to drive costs higher ranging from six to 20 times more expensive than overhead. We’ve had to settle for giant towers cutting a large swath of right-of-way through the countryside and all too frequently, our neighborhoods.
Inevitably, times change, perceptions evolve and shifting realities have brought a new outlook to this market that has traditionally been outside the reach of underground construction. The underground option has increasingly become more attractive as environmental considerations enter planning discussions and new, more stringent regulations create difficulty in maintaining the overhead-leaning status quo. Start factoring in dramatically reduced life cycle costs, resistance to weather impacts and overall more reliable service and the advantages of undergrounding are beginning to sway conventional thinking.
The advent of horizontal directional drilling has added another new wrinkle to streamlining the installation of transmission cables. Rapid improvements of thermal grouts and the cables themselves now offer options making undergrounding more feasible. Of course, creating the power line elements to function properly and effectively can still be very costly. Installing multi-ducts in trenches through open cut or other trenchless methods can also be effective alternatives to a 30-foot eyesore.
But as I listened to utility managers and engineers discuss the challenges of civil construction, it seemed that constructing underground was being viewed as a tremendously complicated and involved process, full of risks andexpenses. Locating existing utilities, potholing and obtaining soil samples, how to properly fill trenches and more such routine aspects of going underground seemed almost foreign to many. With that kind of mindset, it is no wonder people would rather build large towers in your backyard rather than go underground.
Yes, underground work does involve its own set of challenges, but it’s nothing that contractors haven’t dealt with for decades. It is not rocket science. Locating existing utilities, effectively navigating an installation path in and around other pipes, achieving proper depth and fill/compaction of trenches, etc., this is the type of work the good underground contractors do every day of the week in a safe, productive and efficient manner.
My suggestion for achieving savings was simply get contractors involved early in the process. As my good friend Ron Halderman, director of HDD for the Mears Group, pointed out during his presentation, “for owners, being risk adverse costs money. To keep costs down, we need to work together on planning from the start.”
Obviously, this last hold-out of above ground utility construction has much to accomplish in terms of costs, technology and equipment before the practice of going underground becomes routine. But several suggestions came out of the workshop that should aid and direct continued developments of methods and technologies to make this happen. It will be very interesting to see the results of any forthcoming research directions of EPRI. Kudos to the group and its members for embracing the future of underground power transmission installations.
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