A Superior Court judge has certified a class action suit that seeks medical monitoring for Gloucester County, New Jersey, residents — including former Girls Scouts — who fear they were poisoned by toxic waste dumped at one of the state’s worst Superfund sites.

The liquid chemical waste dumped at the Lipari Landfill in Mantua seeped through the soil to ground water below, contaminating nearby streams and Alcyon Lake, the location of a day camp used by the Girl Scouts in the 1960s.