ST. PETERSBURG, Fla.—Engineers and dam safety specialists evaluating the danger of a catastrophic flood from a leaking Florida wastewater reservoir determined that the threat of a possible second breach was “unsubstantiated,” the Florida Department of Environmental Protection said. Officials had said Monday that a drone discovered a possible second breach in the reservoir, whose east wall continues to show “concentrated seepage.” But by Monday evening, experts from four government agencies and outside engineers concluded that this second site was safe to continue working on, the agency announced. Meanwhile, the agency said dozens of pumps and 10 vacuum trucks have been deployed to remove 35 million gallons (132 million liters) of wastewater per day into the Tampa Bay estuary, where 11 different sampling operations are monitoring water quality and considering ways of minimizing algae blooms that kill marine life and make beachgoing hazardous to humans in the tourism-dependent state. “All water …