Gibney said he’d prefer a cheaper solution if he eventually rules against Dominion, which isn’t a given because of another legal issue over whether the ponds can be classified as a “point source” of the pollution. Point sources are usually smaller, easier to identify sources such as discharge pipes.

Lawyers for SELC said none of the cheaper alternatives they’ve seen mentioned will meet the requirements of the Clean Water Act that require the pollution to be stopped.

“This is going to be a perpetual source of pollution unless the ash is removed,” SELC lawyer Deborah Murray said. “Somebody has to live with the consequences, and we’re saying the Clean Water Act puts the burden on the polluter.”

Dominion’s lawyers argued that the case was an attempt to sidestep the state Department of Environmental Quality’s authority by a group that disagreed with its decisions. James Golden, director of operations for DEQ, testified Friday that the agency is responsible for enforcing the federal Clean Water Act in Virginia and that Dominion is in compliance with all of its state-issued permits in Chesapeake.