Solution
BGE selected Burns & McDonnell to evaluate its options and manage the design and implementation of a solution. After a year of analysis, it was determined that installing new overhead lines would be highly favorable compared to pursuing an underground replacement. Building underground would cost approximately twice as much, create significantly greater environmental impact, and affect port operations to a greater degree.
Crossing any river is challenging for transmission lines because of the difficult logistics, planning and coordination. After consultations with the environmental community, the team chose to proceed with the overhead alternative.
The team took proactive measures to communicate with all interested parties, including the Port of Baltimore, the National Park Service, the U.S. Coast Guard and the Association of Maryland Pilots. Planning included the use of construction techniques and timing that would minimize environmental impacts.
The overhead line design included eight towers, five of them in the river. The in-river towers and associated foundation structures had to be designed to withstand the energy from a ship’s impact. To support their foundations, the team drove almost 4 miles of steel pipe pile, totaling about 7 million pounds, to support the precast sections. Each of those towers also required Vessel Collision Protection structures. For towers 3 and 4, which straddle the main shipping channel into the Baltimore Harbor, these structures measured approximately 246 feet long by 156 feet wide.
Construction and installation of the line required deploying diverse specialists and equipment, including helicopters, boats, commercial divers and pile drivers. Running the transmission wires by helicopter also required river shipping and recreational traffic to be shut down temporarily by the Coast Guard. The team worked closely with interested parties to manage and minimize the shipping lane closures for wire stringing activities.
