Dominion Energy’s troubled 500-kV overhead transmission line crossing the James River in historic Colonial Virginia has hit another challenge, but the company says there will be no further delay to the line’s completion date. A lawsuit against the beleaguered line, however, threatens its completion.

The utility delayed construction of the 17 foundations that will hold the lattice towers, some as tall as 295 ft, across the tidal river because it had to double the length of a floating pier to accommodate the river’s tidal flows. The pier is used to load concrete trucks onto barges.

The lost time will be made up during construction, says Bob McGuire, Dominion’s director of transmission development. Towers are expected to rise in July.

Originally needed “urgently” by June 1, 2015, the utility had to resolve challenges from a local government, which wanted the eight-mile line under the river. Now the $325-million project is expected to come online next spring.

The lawsuit filed last July by the National Parks Conservation Association against the U.S. Army Corps of Engineers says that the National Park Service, not the Corps, should have final say. The Interior Dept., in a letter to the Corps, says the power line would cross directly over the Captain John Smith Chesapeake National Historic Trail and be within sight of Jamestown Island, the Colonial Parkway and Carter’s Grove Plantation National Historic Landmark: “In no other place in the U.S. do we have a concentration of historic resources like this, in particular, Jamestown.”

Interior said the historic value of the properties is in the landscape, rather than structures, and as such it was undervalued in an assessment by Dominion contractor Stantec. The plaintiffs argue it is an extraordinary situation in which one federal agency has authorized a project that will traverse public resources managed by another.

Additional transmission is needed after Dominion closed two coal-fired units at its Yorktown power plant. The new line will take power from the Surry nuclear plant to Newport News.