Pepco’s substation parking lot just west of the now-closed power plant on Alexandria’s riverfront would be the terminus of an underground transmission line proposed by Dominion Northern Virginia. (Patricia Sullivan/The Washington Post)

Building a major new power transmission line in north Old Town Alexandria would be “hugely disruptive,” Alexandria City Council members told Dominion Virginia Power officials Wednesday night, expressing skepticism that the construction would benefit the city.

In a 90-minute session with Dominion and Pepco officials, city council members said they only learned two weeks ago that the utility plans over the next four years to build and bury a 230-kilovolt transmission line beneath city streets.

The line would require a trench 8 to 30 feet wide, 41 inches deep, with nothing significant allowed atop it, including containers for trees. It would start at Dominion’s Four Mile Run substation along Four Mile Run in Arlington,and end at the Pepco switching station parking lot, just west of the now-shuttered NRG power plant previously owned by Pepco, GenOn and Mirant, along the Potomac River.

The city has been eyeing that site for a major mixed-use development that they hope would bring in millions in new taxes and enliven the largely residential neighborhood that has suffered through decades of industrial pollution that came from the power plant.

Deborah Tompkins Johnson, Dominion’s regional manager of state and local affairs, said the transmission line is needed to handle an expected increase in local demand for power and to add a connection to the national electrical grid. New federal regulations also require utilities to have more contingency plans to prevent power shortages.

The project must be approved the State Corporation Commission; Johnson said a proposal will be submitted in the fall and construction could begin in two years.

But Alexandria officials said the electricity is destined not for needs in Alexandria or even neighboring Arlington County, but for power-hungry data centers to be built in Loudoun and Fairfax counties. They clearly didn’t believe assurances that no route has been set, alternatives evaluated or that there is time for community input.

“You’re evaluating this project that is going to be hugely disruptive to this community and in­cred­ibly complex,” said council member Paul Smedberg (D). “I find this extremely hard to believe and very disturbing.”

City officials pointed to a February report from PJM, a regional transmission organization that coordinates the movement of wholesale electricity. The report says that the Dominion system was “experiencing significant load growth capacity” in Northern Virginia “primarily due to new computer data centers locating in the area.”

Johnson told the council that she was “perplexed” by the statement in the PJM report, but that expected growth in the Franconia, Van Dorn, Carlyle and North Old Town areas were the primary reason for the line. Later, outside the meeting, she put it more strongly.

“We have data center growth in other communities and we are building transmission projects to address those needs,” she said. “We want to dispel the belief, or any conversation, that this project is being built for data centers or other needs anywhere else,” she said.

Mayor William D. Euille (D) said later that city officials are hearing through other channels that those suburban data centers — none of them located in the city — are the real reason that Dominion is pushing for the project on a fast-track schedule. He and several City Council members insisted on more detail, and asked if the utility had considered running their power line along the railroad right of way, in or beneath Four Mile Run and the Potomac River, or along George Washington Memorial Parkway, whether other utilities are buried.

Johnson repeated that no routes have been identified, although Dominion will have to submit a preferred alternative to the SCC. She said that Dominion will collaborate with the council and the community, holding open houses and creating a Web site that will track each step of the process.

She noted that a similar 230-kilovolt transmission line is buried beneath the Potomac Yard redevelopment site along Route 1, but city staff said they are already having problems working around it, and its location prevented the planting of trees along the road.

Outside the meeting, Johnson said the schedule for a new transmission line is firm.

“We have to have the project done by 2018 because we have an obligation to serve our customers. These are very real constraints,” she said. Dominion has been building similar projects in Ashburn, she said. “Heretofore, Alexandria has been the beneficiary of other projects we’ve built.”

That firmness did not sit well with Elizabeth Chimento, an Alexandria “living legend” who first raised the alarm about the pollution from the power plant and who fought for a dozen years to get it closed.

“You have hit a hornet’s nest, given the history of this corner of Old Town,” she warned Johnson, describing the Pepco switching station as “an eyesore” and objecting to the lack of notification to the city and its citizens. “This is the wrong place, and it should not happen here.”