While local activists rev up their arguments for a potential lawsuit to stop the city from blasting at the Jerome Park Reservoir, they also are considering suing the city for not having a buildings permit to construct the water filtration plant in Van Cortlandt Park.

Activists and Bronx elected officials recently pointed out that the city’s Department of Environmental Protection (DEP) does not have a building permit for the eight-story underground facility.

The Department of Buildings (DOB) deemed the permit unnecessary on a technicality on July 15. The agency ruled that the plant constituted an attached component of a pipe (the Croton Aqueduct) which is exempt from the requirement of a building permit under the City Charter.

“It’s kind of like saying that your body is attached to your arm,” said Assemblyman Jeffrey Dinowitz, who demanded a reexamination of the decision in a July 18 letter to Mayor Bloomberg and other city officials. Dinowitz said the idea that the city does not need a building permit for such a large project is “ludicrous.”

The city has no zoning for a water filtration facility, a fact that cannot be ignored, argues Karen Argenti, a veteran plant opponent who is also a member of the Bronx Council for Environmental Quality. The zoning code, Argenti believes, must itself be revised to create a zoning category for such a facility, a time consuming process that must go through every community board in the city.

“They can’t do what they’re trying to do,” Argenti said.

A judge may determine whether or not she’s right.